Powered by
Teklogin
copyright 2004©
www.prlsamp.org
|
Chemistry |
Brito Rosa; Cabrera, Carlos R.*,Chemistry-UPR Río Piedras Campus
Derivatized platinum surfaces with 3-mercaptohexadecanoic acid, 16-mercaptohexadecanoic acid and 3-aminopropyltrimethoxysilane
Platinum surfaces have been chemically modified and derivatized with mercapto and amine compounds. Self-assembled monolayer of 3-mercaptopropionic acid (HSC2H4COOH, 3-MPA) and 16-mercaptohexadecanoic acid (HSC15H30CO2H, 16-MHDA) were formed at Pt surfaces using 1mM solutions of the modifiers in ethanol. The surface modification with 3-MPA or 16-MHDA was followed by a chemical derivatization with 3-aminopropyltrimethoxysilane (H2NC3H6Si(OCH3)3, 3-APS). The derivatization of the SAM formed at Pt surfaces was done using a 2mM 3-APS, in dimethylformamide (DMF), solution. The final surfaces formed by the derivatization of the SAM/Pt surfaces were characterized by cyclic voltammetry using a 2.5 mM K3Fe(CN)6 in 0.1 M KCl or 2.5 mM Ru(NH3)6Cl3 in 0.1 M KCl solution. These redox system were chosen to study the defect site induced by electrochemical desorption and its effect on the charge transfer processes. Electrochemical impedance spectroscopy (EIS) was used as an additional electrochemical tool, to study the derivatized platinum surfaces. In addition, this technique was useful in the determination of the pinhole size on the derivatized platinum surfaces, at different desorption potentials. For the derivatization of platinum surfaces with amide(3-MPA) and amide(16-MHDA), Nyquist and Bode plots were done using EIS. In summary, the 3-APS derivatization of 16-MHDA/Pt [amide(16-MHDA)/Pt] resulted less accessible to mass transfer effects compared to the derivatized 3-MPA/Pt surface [amide(3-MPA)/Pt].
Calderón, Xiomara; Piñero, Luis E.; Oyola, Rolando; García, Carmelo* Department of Chemistry UPR-Humacao
Síntesis de promazinas 2-substituidas en medio basico
Los derivados de la fenotiazina 2-substituidos tienen una significante importancia farmaceútica debido a sus propiedades neurolépticas, sedativas, antistamínicas y antiplásmicas. La efectividad de la droga y la intensidad de sus efectos secundarios dependen grandemente del substituyente. Fototoxicidad es uno de los el efectos secundarios más importantes de estas drogas. Por lo tanto es importante entender los efectos de estos substituyentes en sus propiedades fotofísicas. En este proyecto hemos sintetizado y caracterizado varios derivados de fenotiazina (2-CN, 2-NO2 y 2-NH2) añadiendo una cadena alifática en medio básico. La caracterización de los productos se hizo con GC-MS y los pro ciento de rendimiento estan en el rango de 40-93%.
Cardona, Rocío del A.; Guadalupe, Ana*; Carrasquillo, José, Chemistry Department, University of Puerto Rico, Río Piedras
Synthesis and characterization of ruthenium electroactive tags for the development of nucleic acid sensors
Innovations in Genetics are leading the scientific community to study the molecular basis of diseases and to look for better diagnostic tools and more sensitive and cost efficient methods. Our research goal is to develop Ruthenium Electroactive Tags for the development of nucleic acid sensors. In this study, the focus is on the synthesis and characterization of the electroactive complexes: [Ru(phen)2(Cl)2], [Ru(phen)2(aphen)(PF6)2] and [Ru(phend)2(a-phen)(PF6)2] wehre phen is 1,10-phenathroline, aphen is 5-amino-1,10-phenathroline and phend is 1,10-phenathroline-5,6-dione. The products obtained from the synthesis were studied using Fourier Transformation InfraRed (FT-IR), Ultraviolet- Visible (UV-vis) and Proton Nuclear Magnetic Resonance (H1-NMR) and Cyclic Voltammetry. Experimental results indicate that the phendione complexes binds to the ruthenium by the N, N’ and O, O’ funcionalities resulting in a mixture of products. We are presently looking into synthetic routes that could discriminate between the two bonding modes and into the synthesis of electroactive polycations using these complexes.
Colón, Jessica, UPR-MAYAGUEZ, Industrial Biotechnology; Campbell, Muriel, Chemical Engineering, UPR-Mayagüez; Pastrana, Belinda*, Chemistry Department, UPR-Mayaguez
Recombinant of a human protein: centrin 2
Centrin is a member of the EF-hand calcium binding proteins, closely related to calmodulin (CaM) with a 30% of sequence identity. Human centrin is a highly conserved protein comprised of 172 amino acids. There are three isoforms of human centrin (Hcen1, Hcen2, and Hcen3). These proteins have different functions: Hcen1, located in chromosome 18, is associated with sprerm flagella (motility); Hcen2, located in chromosome X, has an important role in centriole positioning and organization, and in centrosome segregation during cell division; and Hcen3, with locus in chromosome 5, is associated with spindle pole duplication, also vital in cell division. We are currently interested in Hcen2. Our objective is to generate a recombinant of Hcen2 using pCAL-n vector for transformation in E. coli BL21 (DE3) competent cells. pCAL-n has been successfully used for expression of human CaM. This 5.8 kb vector features a CaM-binding peptide (CBP) affinity tag which will allow purification and expression of the protein passing it through a CaM resin. Future works will include sequencing of the recombinant and expression.
Colón, Marisol; Jaamillo, Kara; Antoun, Helena; Solá, Hilda; Rosario, Osvaldo* Chemistry Department, University of Puerto Rico, Rio Piedras Campus
Distribution of organic compounds in aquatic systems
The distribution, transport and ultimate fate of organic pollutants is of great importance but it is still not completely understood. To better understand the process, it is necessary to detect pollutants, at the ppb and ppt range, in the different compartments that constitute the system. The objective of our work is to optimize extraction methods for the analysis of organic pollutants in different compartments of the aquatic system and to have a better understanding of the distribution of such compounds in the systems. We are interested in a three-phase system composed of the water column, the suspended particles and the sediments as the compartments of the system. In the first stage of this research, we are optimizing the analysis methods used for the detection of organic pollutants, in the three-phase system. To have a controlled system we used kaolin and silica as the model matrix to simulate the suspended particles and the sediments. Spiked real samples are also used. The water column is extracted with Solid Phase Microextraction (SPME). Suspended particles are sampled on a GF/F filter and extracted with a mixture of solvents in an ultrasonic extractor. Supercritical fluid extraction and ultrasonic extraction are being compared for the analysis of sediments. To lower the detection limits, SPME and stir bar solid extraction (SBSE) of the concentrated extraction are being performed. Solid phase micro extraction is being used for the extraction of water. Gas Chromatography-Mass Spectrometry is being used for the analysis of all the extractions.
Colón Rosado, Yaitza; Bermudez, Ricardo; Colon, Jorge L.*University of Puerto Rico, Rio Piedras Campus, Department of Chemistry
Intercalation and photophysical characterization of 1-pyrenemethylamine into the 10.3 Å phase of layered zirconium phosphate
We are studying the intercalation of poly aromatic hydrocarbons between layers of zirconium phosphate (ZrP). The aromatic hydrocarbons have been used in different environments as luminescent probes. We have been working with a Pyrene derivate called 1-pyrenemethylamine hydrochloride (PYMA), to investigate its photophysical as well as photochemical properties in this microenvironment. The matrix used is a derivate of -zirconium phosphate, with a separation between the layers of 10.3 Å. The intercalation was performed at 1:1, 5:1, 10:1 PYMA/zirconium phosphate ratios. The product was characterized using X-ray Powder Diffraction (XRPD), UV- Visible Spectrophotometry (UV-Vis), Luminescence Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). Similar results were obtained with the three PYMA/ZrP ratios. In XRPD, an increase in the distance between the layers from 10.3 Å to 23.5 Å was observed, which suggests PYMA is being intercalated. The UV-Vis absorbance spectrum showed the presents of PYMA bands, confirming its presence between the layers. The luminescence spectrum showed bands similar to those observed in aqueous solution, except that an excimer band absence in solution is observed in ZrP. XPS analysis showed a 2:1 P:N ratio, which suggests that the maximum amount of PYMA between layers of ZrP has been reached.
YCR: acknowledges the financial support of the PR-LSAMP program.
Correa Ramírez, Wildeliz; Ortiz-Marciales, Margarita*Departamento de Quimica, Universidad de Puerto Rico-Humacao
Síntesis de aril alquil aminas
Las aminas quirales son compuestos de importancia biológica, utilizadas en la síntesis de gran variedad de compuestos farmacéuticos. Las 1,3,2-oxazaborolidinas son utilizadas como reactivos importantes para la reducción enantioselectiva de cetonas e iminas, y también utilizada para otras transformaciones enantioselectivas. Estos compuestos fueron preparados in situ debido a que son extremadamente sensitivos al aire y a la humedad y son muy difíciles de purificar por destilación o recristalización. El objetivo principal de nuestra investigación es desarrollar nuevos métodos para la síntesis de aryl alquil aminas de importanica biomédica. En particular, se desea conseguir un método general y eficiente para la síntesis de las aminas quirales con un alto exceso enantiomérico. Nuestro trabajo envuelve la reducción de la sal de la imina preparada por la adición de un oganolitio, como butil, fenil y metil litio a un nitrilo aromático, como 2-methoxy benzonitrilo. Como agente reductor utilizamos borano y 1,3,2-oxazaborolidinas enantiopuras. Estas oxazaborolidinas fueron preparadas por la reacción de 1R-2S-(-)-efedrina y 1R-2S-(-)-norefedrina con 2.6 equivalentes de borano a temperatura ambiente. Se investigó la formación de un aminoborohidruro como agente reductor quiral usando n-butil litio. Resultados preliminares de la reducción de 1-(2-metoxifenil)-pentilamina quiral con el borohidruro de esta reacción serán presentados. Utilizando el aminoborohidruro como agente reductor quiral y añadiéndole luego borano se obtuvo un 34 por ciento de exceso enantiomérico.
Cotto, Marlene; Miranda, Carlos; Carballeira, Nestor* Department of Chemistry, UPR-Río Piedras campus, PO Box 23346, San Juan, PR
The first total synthesis of the marine fatty acid (±)-9-methoxypentadecanoic acid.
A synthetic route towards mid-chain methoxylated fatty acids
The marine fatty acid (±)-9-methoxypentadecanoic acid was synthesized for the first time in seven steps (7.8 % overall yield) starting from commercially available 9-decen-1-ol. The key step in the synthesis was the coupling of a pentylmagnesium bromide to 1-benzyloxy-9,10-epoxydecane catalyzed by 1,5-cyclooctadiene copper (I) chloride. Nuclear magnetic resonance data are provided for the first time for this type of fatty acids and the synthetic approach utilized can be used in the synthesis of other mid-chain methoxylated fatty acids. These results will be helpful in subsequent characterizations of other mid-chain methoxylated fatty acids, and should provide sufficient quantities for biological evaluations of this type of fatty acids.
M. Cotto thanks the UPR-RP RISE program for an undergraduate fellowship.
Crespo Méndez, Yolanda; Sánchez Báez, Eliany; Ramírez Soto, Doris * Department of Chemistry, UPR-Mayagüez
Caracterización de giberelinas endógenas en Eryngium foetidum L. Apiaceae
Las giberilinas (GAs) son biorreguladores que controlan varios procesos fisiológicos en las plantas tales como el alargamiento del tallo, desarrollo del fruto y la sincronización floral. El objetivo de la investigación es caracterizar las giberilinas endógenas presentes en la semilla y en la hoja del Eryngium foetidum L. Apiaceae. La semilla y la hoja inmadura del culantro se recolectaron por separado y se homogenizaron en metanol. Las muestras se filtraron, se extrajeron con acetato de etilo, se eluyeron utilizando una columna empacada con polivinilpolipirrolidona seguido de una columna de carbón activado-celita y luego se extrajo con acetato de etilo y un amortiguador de fosfato. Se utilizó cartuchos de C18 para separar los compuestos obtenidos seguido de de cromatografía líquida de alta presión (HPLC). Las fracciones con actividad biológica se identificaron con la técnica del bioensayo de hipocotilo de lechuga. Las muestras con actividad biológica se secaron, se metilaron con diazomentano y se sililaron con N,O-bistrimetilsililtrifluoroacetamida. Las giberilinas fueron identificadas utilizando un cromatógrafo de gas acoplado con un detector selectivo de masa (GC-MSD). Las muestras de semilla con actividad biológica han mostrado la presencia de la GA3, 2a-OH GA24, y la GA39, mientras que en la hoja mostró la presencia de la GA 68. Esto nos sugiere que las GAs presentes en la semilla y en la hoja tal vez no tengan la misma ruta metabólica
Cruz Martínez, Nadya; García, Carmelo*; Nieves, Ileana*, Department of Chemistry, UPR-Humacao; Oyola, Rolando; Piñero, Luis; Arce, Rafael* Department of Chemistry, UPR-Río Piedras
Estudios electroquimicos de algunos derivados de promazina
Las promazinas son drogas tri-cíclicas de gran importancia farmacológica debido a sus efectos antiestamínicos, sedativos, neurolépticos y anti-tumorales. Se postula que los mecanismos de reacción relacionados a la efectividad de la droga y a sus efectos secundarios se deben a intermediarios de corta vida que dependen de la capacidad de las drogas para oxidarse. La sustitución de diferentes grupos funcionales en la posición 2 de los derivados de promazina afecta la capacidad de oxidarse. Por esto estamos estudiando la electroquímica de algunos derivados en diferentes disolventes y en mezclas de éstos. Se determinaron los potenciales de oxidación y de reducción usando un Analizador Polarográfico (BAS CV-50) en acetonitrilo y metanol (TBAP 0.1M como electrolito soporte). Se utiliza carbono, cloruro de plata saturado y platino como electrodo de trabajo, de referencia y auxiliar, respectivamente. La magnitud de los potenciales se relaciona con la facilidad de oxidación de los derivados y se comparan con las respuestas fotoquímicas y fotofísicas de las drogas. La relación es importante para entender los efectos secundarios observados en la piel de pacientes. Además, estos resultados son importantes en el desarrollo de drogas nuevas más efectivas y con menos efectos secundarios.
Auspiciado por Advance, NSF-UPR-Humacao (SBE-0123645) y AMP, NSF-UPR-Río Piedras
Cruz Rodríguez, Osvaldo; Rodriguez, Lolita; Souto Bachiller, Fernando A.*Chemistry Department; Industrial Biotechnology Program, UPR-Mayagüez
Antilithic activity and ionized calcium binding capacity of 4-nerolidylcatechol, a major component of Baquiña hembra
Lepianthes peltatum (L.) Raf. is a folk remedy to treat kidney stones (CaC2O4) and calcifications. Previous work at the Natural Products Laboratory has shown that leaf decoctions of Baquiña are able to bind Ca+2. The principal component of Baquiña is 4-nerolidylcatechol (4-NC(OH)2), as revealed by a GC/MS analysis. This cathecol is likely responsible for the Ca+2 binding capacity shown by the plant decoction. Consequently, the objective of this study was to isolate 4-NC(OH)2 and determine its Ca+2 binding capacity. Plant material was field collected, freezed dried, milled and extracted with CH2Cl2 in a Soxhlet apparatus. The extract was analyzed by normal phase TLC. The catechol was revealed with the vanillin-sulphuric acid reagent, a catechol specific test. Following the chromatographic identification as 4-nerolidylcatechol by GC-MS, the components of the extract were separated by LC. Fractions were collected and analyzed by TLC and HPLC. Those with the highest purity were rechromatographed for further purification. The resulting pure fractions were analyzed by 1H and 13C NMR confirming their identity and purity. The binding capacity of the pure product is under investigation with the calcium selective electrode, the o-cresolphthalein complexone and the arsenazo-III colorimetric assays. Preliminary results with the o-cresolphthalein complexone are encouraging since they suggest a high affinity to bind free calcium for 4-NC(OH)2. The experiments with the calcium electrode have indicated an unexpected solubility problem for this compound at all pH’s. This suggest a water soluble form of 4-NC(OH)2 is more likely to be responsible for the antilithic action of this plant.
Cuadra, Luis; Alvarez, Olga; González, Ileana; Jiménez, Braulio; Rosario, Osvaldo*, Chemistry Department, UPR-Rio Piedras
Characterization of organic toxic compounds in respirable particulate matter
Airborne particulate matter has been reported in several epidemiological studies around the world as one of the principal causes of respiratory illnesses and other health conditions. Recently EPA has reported how fine particles in air affect the health of populations in the USA and has even attributed levels of mortality to polluted air. On average, fine particle mass consists of about 20-40% carbonaceous material, with about one-third of the aerosol carbon present as black elemental carbon and two-thirds present as organic compounds. Dr. Darwin Reyes performed the first toxicological screening and chemical characterization of the organic compounds in particulate matter samples from Puerto Rico (Guaynabo and Fajardo). The purpose of this research is to expand Dr. Reyes’ study by developing an analytical method that will increase the scope of organic compounds that can be identified in particulate matter. The methodology being developed uses the determination of toxicity in each of the fractionation steps to focus analysis on the more active fractions. New alternatives have been studied and applied in order to increase the number of compounds analyzed and improve the identification and analysis in particulate samples by GC/MS. Supercritical Fluid Extraction (SFE) and Thermal Desorption (TD) are being explored on ambient samples with good results. Samples taken downwind from an incinerator in Caguas were analyzed. SEM, XRF amd GC/MS analysis were performed. Higher levels of chlorine content were observed than at other sites of Puerto Rico
Días-Ayala, Ramonita; Pérez, Sorybel; Marrero, Cruz; Raptis, Raphael*; Cabrera, Carlos R.*, Department of Chemistry, University of Puerto Rico, Río Piedras Campus
Thermal reduction of different molecular precursors to form Pd nanoparticles at HOPG surface
A highly ordered pyrolytic graphite (HOPG) surface has been modified by the adsorption of Pd ion molecular precursor from solution. The modified surface has been characterized by X-Ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). In order to obtain PdO and Pd nanoparticles the neutral molecular precursor will be reduced in hydrogen atmosphere. Thermogravimetric analysis were done to establish the behavior of these precursor at different temperatures. The stability of PdO at different temperatures is very important because of its use in primary catalytic combustion, methane oxidation. The reductive process was monitored by XPS.
Díaz, Agustín; Santiago Berríos, Mitk'El B.; Guadalupe, Ana R.*; Colón, Jorge L.*, Chemistry Department, UPR-Río Piedras
Synthesis, characterization and intercalation of bis(1,10-phenanthroline-5,6-dione)bipyridine ruthenium(II) into the 10.3 Å phase of layered zirconium phosphate
We are interested in the construction of electrochemical biosensors using zirconium phosphates inorganic solids. Zirconium phosphates (ZrP), which are acidic, inorganic, ion exchangers with layered structures, have been extensively investigated. We are investigating the use of these materials as hosts for electron mediators for biosensor work using a 10.3 Å phase of ZrP which we have recently demonstrated directly exchanges large metal complexes. The electron mediator chosen for our studies is the inorganic complex bis(1,10-phenanthroline-5,6-dione)bipyridine ruthenium(II) ([Ru(phend)2(bpy)]2+). This complex has been previously utilized in the preparation of biosensors, but this is the first time that is being used in this more rigid microenvironment. The synthesis of the 10.3 Å ZrP phase and [Ru(phend)2bpy]2+ were successful and both were characterized. [Ru(phend)2bpy]2+ showed the characteristics MLCT bands in the UV-Vis absorption spectrum and also showed the characteristics bands in the IR spectrum. The interlayer distance of the zirconium phosphate layer with the immobilized electron mediator intercalated is 14.1 Å as determined using X-ray powder diffraction.
A.D. acknowledges the financial support of the NIH-RISE/SUBE Undergraduate Fellowship
Espinosa Díaz, Sandralíz; Ortíz Marciales, Margarita*, Departamento de Química, UPR-Humacao
Síntesis de aminas quirales primarias
Un gran número de los compuestos orgánicos quirales son usados en la síntesis de drogas farmacológicamente activas. Las aminas primarias con un carbono asimétrico alfa tienen una gran importancia, debido a que son usadas en la síntesis de drogas quirales como anfetaminas, de antistaminas y de antibióticos. El objetivo de nuestro proyecto de investigación es desarrollar un nuevo método para la reducción enantioselectiva de iminas con los reactivos chirales del organoborano para obtener las alquil aril aminas primarias. Las sales de los iminas fueron formadas por la adición del reactivo del organolitio al anisonitrilo. El agente reductor quiral en esta rección es la B–Butil 1,3,2-oxazaborolidine de (1R, 2S)-(-)-norephedrine y borano. Después de la hidrólisis de la mezcla de reacción con HCl y la neutralización con el NaOH, las aminas fueron obtenidas con un buen rendimiento químico, no obstante el exceso enantiomerico fue bajo (12-20%). Estamos estudiando otras condiciones de la reacción para mejorar la enantioselectividad.
García, Edgardo; Department of Chemistry, UPR-Cayey
Electrochemical analysis and SPM characterization of benzenethiol on gold surfaces
The field of the self-assembled monolayers (SAMs) had become a great tool for the biosensor engineering, corrosion inhibition and for the development of different materials with a great molecular identification capacity. The interaction between gold and benzenethiol is under study because spontaneous monolayers can be created in the adsorption of benzenethiol on gold surfaces. The gold surfaces will be prepared on mica substrates by ultra high vacuum sputtering procedures because of the uniform molecular orientation of mica that permit the gold atoms deposited to also orientate in the same pattern. The sputtering technique consists of an ion bombardment impact that establishes a train of collisions in a target (gold). It is related to momentum transfer from energetic particles of the plasma to the surface atoms of the target. Atomic force microscopy (AFM) and scanning tunneling microscopy (STM) will be use for the characterization of the mica-gold surface and the orientation of the benzenethiol SAM. FTIR have been used to demonstrate the presence of benzenethiol on gold surfaces. Cyclic Voltammetry have been used for the electrochemical behavior of benzenethiol on gold. Preliminary results show the presence of two voltammeter waves suggesting an adsorption desorption processes.
García Fragra, Oscar; Díaz Vázquez, Liz M.; Arocho Pérez, Freddie; Rosario, Osvaldo*, Department of Chemistry, University of Puerto Rico, Río Piedras
Method development for the non invasive determination of environmental pollutants through sebum
Human exposure to exogenous compounds has been an area of interest for many reasons. These are the health implications of these compounds, the development of preventive methods, the understanding of substance interactions with the environment and the study and understanding of the processes of incorporation into the human body. In order to study, determine, monitor and characterize exogenous compounds in the body different matrixes have been used. Among these matrixes are blood, urine, nails, hair, saliva, plasma and sweat. These matrices present some advantage and disvantages. Between the disvantage are that the collection is invasive to the patient and the complexity of the matrices. Sebum has been used to monitor use of controlled drugs as well as exposure to dioxins. Based on this, it is logical to extrapolate its use to also monitor exposure to other environmental pollutants. We have been working on the development of methodology for the sampling extraction, and analysis of organic compounds in sebum. Commercially available sebum has been used for the method development. We have tested the use of patches, cotton swabs and cotton balls for the direct sampling of sebum. SEM\EDS has been used to characterize and determine the composition and appearance of the collected sample. In addition to thermal desorption, Soxhlet and ultrasonic extraction, a range of solvents and solvent mixtures were tested to optimize extraction of analytes spiked onto sebum. Hexane gave the best results in terms of the number of compounds extracted however dichloromethane was able to extract certain compounds more efficiently. Also supercritical fluid extraction and SPE is being tested to remove spiked analytes onto sebum. Pyrene was detected in high abundances. To reach this goal we have to test different collection devices, extraction techniques and analysis and modes of detection. Focus in this method development is placed on standard compounds, the majority of which are lipophylic. The challenge of this research is to optimize the available technology and existing methodology in order to develop a universal methodology for this purpose. Once validated, the method will be used to evaluate exposure to environmental pollutants.
Giovanni Paraliticci; Angel Martí; Jorge L. Colón*, Departamento de Química, Universidad de Puerto Rico, P.O. Box 22346, San Juan, Puerto Rico 00931
Spectroscopic characterization of methylviologen encapsulated into a-zirconium phosphate
Methylviologen (MV2+) or paraquat is commonly used in chemical, biological and photochemical redox reactions as an electron-transfer indicator. The potential applications of methylviologen of storage and energy conversion have captured great attention. Among inorganic compounds, layered metal oxides and phosphates occupy a major position for exploring artificial photochemical and photophysical process in controlled media. Because of its 2+ charge and its small size, this reagent is appropriate to be ion exchanged into the a-zirconium phosphate gallery. We have characterized MV2+ exchanged at a-ZrP by: Luminescent spectroscopy, X-ray Powder diffraction and UV- visible spectrophotometry. Also we will report quenching studies.
González, Daliangelis; Torres-Silva, Ivelisse; Rosario, Osvaldo*, Chemistry Department, University of Puerto Rico, Río Piedras
Method Development for the Determination of Suspected Endocrine Disrupting Compounds (EDCs) in Seawater
The determination of pollutants in seawater is an area that has not been well studied in environmental sciences. Cases of endocrine disruption in marine species are known and its ecological significance has been discussed. There is a need to know the levels of Endocrine Disrupting Chemicals (EDCs) in seawater. The purpose of this investigation is to develop and validate methodology to study EDCs in seawater. Solid Phase Microextraction (SPME) is being used as the extraction technique and GC/MS for the chemical analysis. Polydimethylsiloxane/ divinylbenzene 65µm fiber was better for the extraction of the phthalate ester standards studied from the model matrix in comparison with the Polyacrylate 85µm and Polydimethylsiloxane 100µm. An extraction time of 45 minutes was determined from the extraction time profiles as well as practical limitations. Sample stirring was observed as an important parameter in SPME in which 700 rpm was chosen in our study. A decrease in extraction efficiency was observed when commercial humic substances were added to the model matrix. Natural humic material has been sampled from ocean water and will be used to study its effect on the SPME fiber. The effect of multiple samplings on the fiber was studied using Scanning Electron Microscopy (SEM). A marked deterioration of the fiber can be observed. Additional experiments will be performed to optimize and validate the methodology.
González, Yanira; Colón, Maricel; Quiñones, Luis; Morales, Reginald*, Department of Chemistry, University of Puerto Rico, Río Piedras; Quesada, Orestes*, Department of Physical Sciences, University of Puerto Rico, Río Piedras
Using PLA'S to probe the interaction of the detergents TOPPA and TOPPS with intact membranes
The interaction of two detergents with the same bulky hydrophobic moiety but, with different headgroups; 3-[(4-tert-octyl)phenoxy]-1-(trimethyl-ammonium) propylbromide (TOPPA) and 3-[(4-tert-octyl)phenoxy]-1-propanesulfonic acid (TOPPS) were probed by measuring their effects on binding and hydrolytic rates of two different snake venom phospholipases A2 (PLA). The PLA’s used included a non-specific enzyme from Naja nigricollis, a specific PLA from Agkistrodon halys. The concentrations of detergent used were those which were found to induce minor shape changes in erythrocytes membrane (0-250 nmo added/mL cells), but no significant hemolysis. Work with cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS) indicated that both PLA's were affected similar levels of detergents in a qualitatively similar fashion. In the case of the N. nigricollis both decreased binding, but SDS increased vo/Ebt by 2.4 fold and CTAB decreased it 50%. (Supported by MARC Program)
Guillen, Nancy; UPR-Mayagüez, Industrial Biotechnology Program/ Faculty of Arts and Sciences; Narvaez, Daniel; Pastrana-Rios, Belinda*, Department of Chemistry, UPR-Mayagüez
Fast H/D Exchange Two-Dimensional Correlation Spectra Studies for EGF AND TGF-alpha using FT-IR
Growth factors are small proteins found in serum in very low concentrations that directly stimulate cell division. Epidermal growth factor (EGF) is a single chain growth factor containing 53 amino acids (6 kD) and three disulfide bonds. Transforming growth factor alpha (TGF-á) is a small 50 amino acid mitogenic protein, which shares about 30% sequence identity with EGF and competes as a ligand with it for the same receptor sites of Epidermal Growth Factor Receptor (EGFR). EGFR is a transmembrane glycoprotein found primarily on cells of epithelial origin. It is a member of a family of growth-factor receptors with tyrosine kinase activity. Binding of ligands to the growth-factor receptor triggers a number of cellular responses that eventually lead to cell proliferation and act in an atypical manner in tumor cells. As part of this research, fast H/D exchange studies of the ligands EGF and TGF-á were performed using Attenuated Total Reflectance (ATR) - FTIR spectroscopy. This provided information on the ligands accessibility to its aqueous environment, its conformation and its dynamic behavior upon H/D exchange. The spectra obtained were analyzed by a two-dimensional correlation to determine which regions of the protein go through the H/D exchange first and the subsequent order of events during the exchange process. A goal of this investigation is to clarify the role of a soluble isoform of epidermal growth factor receptor (110 kD-sEGFR), a serum biomarker for epithelial ovarian cancer, in modulating the interaction of EGF, and TGF-á with EGFR.
Hernández, Yuanil; Department of Biology, UPR-Mayagüez; Rivera Montalvo, Luis A.*, Department of Chemistry, University of Puerto Rico-Mayagüez
Synthesis and characterization of polycyclic and heterocyclic fluorene derivatives by deprotonation of fluorene and subsequent condensation with appropriate aromatic or heterocyclic aldehydes
As a general objective of developing new synthetic strategies to the preparation of novel heterocyclic compounds with potential as pharmaceutical drugs, we have explored the base catalyzed addition of fluorene nucleus to aromatic and heterocyclic aldehydes. We have prepared the 9-(1-chloro-4-nitrophenylmethylidene)fluorene with the purpose of validating the condensation reaction and our primary goal has been focused on the preparation of the 9-(2-thiazolylmethylidene) fluorene. The reaction conditions and experimental results will be presented. The characterization was performed by interpretation of FT-IR and GC-MS spectroscopic data.
Hernández Pagán, Emil A.; Hernández, Samuel *, Castro, Miguel E. *, Chemistry Department, UPR-Mayagüez
Development of photolitogrphy using sunlight
Photolithography is an attractive approach to the fabrication of biosensors, miniaturized sensors, microelectronic mechanical systems (MEMS) and microelectronic circuits. We have use sunlight for the effective fabrication of metallic patterns containing silver clusters. This, because silver cluster photo-deposition was found to be sensitive to the incident of light source, with only UV light resulting in pattern formation. Patterns as small as a few micrometers have been prepared by the photo-reduction of concentrated AgNO3 solutions on cellulose substrates. The mask pattern was design employing AutoCAD, and develop in a transparency with the use of a common printer: micro-patterns suitable for miniaturized sensor development were developed using this approach. Silver cluster patterns have been characterized with optical microscopy and X-ray fluorescence measurements. We attempted to develop these metallic patterns in a smaller scale by decreasing the dimension of the mask pattern; but we encountered the imitation that the printer did not have enough resolution. Therefore the ongoing work focuses on the use of near field optical microscopy techniques for the preparation of nano-patterns with dimensions as small as a few nanometers.
Jiménez Hernández, Yajaira; Ingeniería Química, UPR-Mayagüez; Plaza, Maria de L.*, Prof. Programa Ciencia y Tecnología de Alimentos/UPR-Mayagüez; Rodríguez Flores, Manuel*; De Jesús Echevarría, Maritza*, Departamento de Química, UPR-Mayagüez
Composición química del aroma de la fruta "Mammea americana L." por SPME y GC/MSD
El clima tropical de Puerto Rico ha favorecido siempre el crecimiento de una exótica y variada flora. Esta característica ha sido un factor importante para que el árbol frutal de la Mammea americana L., mejor conocido como el mamey, se coseche en muchos pueblos de la Isla. La fruta del mamey es grande y el color de su pulpa puede variar entre amarillo y anaranjado intenso. Su pulpa es firme y carnosa y la misma tiene un aroma suave y delicioso. Ésta, generalmente se come fresca y en muchas ocasiones se sirve en lascas. La pulpa además, puede prepararse en preservas, incorporarse a “pies” o ser utilizada para la preparación de licor. El objetivo principal de esta investigación es estudiar la composición química de esta fruta en diferentes pueblos de la Isla. Se seleccionaron tres pueblos, Mayagüez, Isabela y Aguadilla y se desarrollo un método comparar los resultados de su composición química por la técnica “Solid Phase Microextraction” (SPME) y utilizando cromatografía de gas acoplado a un detector selectivo de masa GC/MSD. Se analizaron 19 muestras de la fruta, que fueron recolectadas en los pueblos de Aguadilla, Isabela y Mayagüez. Los resultados fueron muy exitosos. La composición química de las frutas de los diferentes pueblos era parecida, especialmente los componentes que se encontraban en mayor abundancia, aunque había ciertas variaciones. Se logró identificar tentativamente 20 compuestos volátiles y semi-volátiles con una probabilidad de 99%. Entre los componentes encontrados había monoterpenos, sesquiterpenos, alcoholes, ésteres y otros.
López Alvarez, Yania M.; López, Gustavo*; Pastrana-Ríos, Belinda*, Chemistry Department, UPR-Mayagüez
Computational studies of model surfactant langmuir monolayers
A new computational model has been implemented in order to describe the behavior of model surfactant molecules forming a Langmuir monolayer. The model consists of the coupling of an isothermal-isobaric simulation that describes the surfactant with a canonical simulation that describes the water phase. The method permits the construction of adsorption isotherms, where the area of the monolayer is computed as a function of applied lateral pressure. The interparticle interactions were modeled using a bead-like potential that describes the hydrophobic and hydrophilic interactions. The isotherms constructed showed three distinctive region of the phase diagram; i.) An expanded liquid phase in a high temperature region at all applied pressures, ii.) A expanded-liquid compressed-liquid equilibrium at intermediate temperatures, and iii.) A compressed liquid phase at low temperatures at all applied pressures. The results obtained from these simulations are in good agreement with experimental studies.
López Colón, Dalia; Alegría, Antonio E. *, Departamento de Química, UPR-Humacao Sonochemistry of quinone-containing antitumor drugs
Sonodynamic therapy of tumors is a modality in which certain drugs act sinergistically with cavitation-producing ultrasound on tumor cell killing. In this work we demonstrate that antitumor quinones enhance the rate of ferricytochrome c reduction during the ultrasound sonication of aqueous solutions. These enhancements are partially inhibited by superoxide dismutase (SOD), thus implying a role for the superoxide ion in this process. Best correlations were obtained between the rates of ferricytochrome reduction and quinine hydrophobicity than with quinine redox potential. The latter can be explained by the better accessibility of hydrophobic quinines to reducing radicals (H, O2¯) at the interfase of the cavitation bubble.
Maldonado, Lorena; Marti Angel; Colón, Jorge *, Chemistry Department, University of Puerto Rico-Río Piedras
Synthesis, characterization and incorporation of a novel rhenium complex into zirconium phosphate
We are interested in the incorporation of luminescent metal complexes into the inorganic layered material zirconium phosphate (ZrP). One approach that we are pursuing is the covalent attachment of the metal complex to the inorganic layers through one of the ligands of the complex. A suitable ligand candidate is 1,10-phenanthroline 5,6-epoxide (ephen). We have synthesized the inorganic complex fac-(1,10-phenanthroline 5,6-epoxide)tricarbonylrhenium(I) (Re(ephen)(CO)3Cl) which incorporates this ligand. Rhenium complexes have special photochemical and photophysical properties that make them suitable for photoinduced electron and energy transfer. We are interested in these properties because of their possible application in the area of solar energy storage and conversion. This is the first reported synthesis of the Re(ephen)(CO)3Cl complex whose novelty is that it possesses the ephen ligand. The techniques used to characterize this complex include NMR, infrared, UV-Visible, and luminescence spectroscopies. We will present the complete characterization of this complex and preliminary results of its incorporation into ZrP and the photophysical properties of the resulting material. L.M. acknowledges the financial support of the Howard Hughes Program A.M. acknowledges the financial support of the NIH-RISE/SUBE Graduate Fellowship. J.L.C. acknowledges the financial support of the NIH-SCORE program.
Martín, Mariana; Rodríguez, David; Prieto, José A.*, Department of Chemistry, University of Puerto Rico, Río Piedras
A new epoxide approach to polypropionate chains using trimethylalane
Alternating hydroxyl and methyl groups on an aliphatic chain with a distinct stereochemistry is known as a polypropionate unit. Polypropionates are a common feature of many macrolides and ionophores possessing remarkable biological activities. In our research laboratory, we have been developing a general, stereoselective synthetic strategy to polypropionates based on oxirane and propynyl alane chemistry. This strategy uses iodocyclization reactions to attain the required stereoselective epoxidations and propynyl alane as the epoxide cleaving agent. Herein we report a new approach towards the preparation of polypropionates based on peroxide epoxidation and trimethylalane cleavage. The protected dieneol 1 is being transformed into 2 via a sequential monoepoxidation and epoxide cleavage with an alane reagent followed by a second epoxidation and alane cleavage. This approach is different from our standard epoxide approach to polypropionates and should produce similar compounds more efficiently. The details of this study will be presented. Work supported by the NIH SCORE 2S0GGM-08102-29, NIH RISE (1R2S-GM-G11S1-01AI) and MARC (5T34GM07821)
Martínez Ginel, Carmen; De Jesús Echevarría, Maritza; Rodríguez Flores, Manuel*, UPR-Mayagüez Artes y Ciencias/ Departamento de Química, UPR-Mayagüez; Lo Presti, Joseph, Ingeniería Química, UPR-Mayagüez
Método para la determinación de benzodiazepinas en pastillas genéricas y originales.
En la actualidad las benzodiazepinas son algunos de los compuestos que más se venden en las farmacias, ya que se utilizan para controlar la ansiedad. En las farmacias venden las pastillas en su forma original o genéricas o bioequivalentes. Existe una gran preocupación, si existe una diferencia entre las pastillas originales y la bioequivalentes con relación a su componente activo. El objetivo de esta investigación fue desarrollar un método para aislar estos compuestos en las pastillas original y genérica, y comparar si el ingrediente activo estaba presente en ambas pastillas y en que cantidades. Después de varios intentos durante el semestre se pudo desarrollar un método rápido y efectivo para aislar las benzodiazepinas de las pastillas original y genérica. Además se encontraron los parámetros cromatográficos óptimos para el análisis. Los resultados muestran que existe una diferencia entre la concentración de las benzodiazepinas genéricas y las originales. Si al hacer más pruebas de este experimento se siguen observando este mismo patrón se podría decir que las pastillas genéricas son menos eficientes que las originales, y que es muy probable que los pacientes no sintieran los mismos resultados al utilizar la genérica. También es posible que los pacientes que utilicen la genérica experimenten algunos efectos secundarios que las originales no les causaría.
Medina-Emmauelli, Nadia M.; Universidad Católica, Department of Chemistry; Kristian, Kathleen E., Department of Chemistry, Swarthmore College; González, Adolfo; De Jesús, Joel; Vargas, Iris M., Department of Physics, University of Puerto Rico; Ortiz, Oscar O., Department of Chemical Engineering, Polytechnic University; Weiner, Brad R.* Department of Chemistry, University of Puerto Rico; Morell, Gerardo*, Department of Physical Sciences, University of Puerto Rico
Raman spectroscopy study of the effects of space radiation on the microstructural properties and composition of sulfur-incorporated nanocomposite carbon thin films
The compositional and microstructural transformations induced by simulated space radiation (i.e., heavy ions) on sulfurincorporated nanocomposite carbon (n-C:S) were investigated by Raman Spectroscopy (RS) and Scanning Electron Microscopy (SEM). Two identical sets of n-C:S films were prepared in a hot filament chemical vapor deposition (HFCVD) system using CH4, H2 and H2S. Films with various sp3 C and sp2 C bonding distributions were present within each set, which were obtained by varying the substrate temperature (300-900 ºC), the CH4 concentration (0.3 and 2.0%) and the H2S concentration (0 and 500 ppm). One set of films was submitted to a 25 Krad dose of energetic Si and Fe ions at Brookhaven National Laboratory's Alternating Gradient Synchrotron (AGS). All the films showed the characteristic diamond (tetragonal sp3 C) band at around 1332 cm-1 and the graphitic (trigonal sp2 C) D and G bands at around 1350 and 1590 cm-1, respectively, evidencing their composite nature. Films with only sub-micron particles showed no significant morphological changes after being exposed to the ion radiation, while microcrystalline diamond particles underwent dramatic morphological improvement upon irradiation. Detailed quantitative analysis of the RS spectra indicated that significant changes in the aggregation state of sp2 C and in the fraction of sp3 C took place. The sp2 C component showed a definite tendency towards aggregation upon irradiation, regardless of whether its total fraction was increasing or decreasing. However, the changes in the sp3 C component were found to depend on the film’s initial carbon bonding distribution. Films that were initially rich in sp3 C became less rich in sp3 C and richer in sp2 C after irradiation, and vice versa. These results suggest that stable nanocomposite carbon materials can be prepared that would remain unchanged in their average composition while absorbing ionizing radiation. Such behavior goes beyond the concept of radiation hardness and into radiation insensitiveness. The results can be understood in terms of the carbon bonding interconversion hypothesis proposed by Gupta et al (Journal of Applied Physics 92, 2002) for gamma irradiated microcrystalline and nanocrystalline diamond films, and provide additional support to the possibility of fabricating carbon-based radiation buffers.
Acknowledgements: This investigation was supported by the NSF-REU Summer Program at the University of Puerto Rico Award # 0097768 and NIH National Research Service Award GMO7732-23 from the Pontifical Catholic University of Puerto Rico
Montano, Nashbly; González, Karilys; Pérez, Caroline; Griebenow, Kai*, Department of Chemistry, University of Puerto Rico, Río Piedras Campus
Stabilization of -chymotrypsin at methylene chloride/water interface and upon encapsulation in polyester microspheres using the w/o/w technique
The loss in activity and protein aggregation is a serious drawback in their encapsulation in bioerodible polymers by water-in-oil-in-water (w/o/w) encapsulation techniques for their release. Herein, the model protein chymotrypsin was employed to investigate whether its stabilization towards the emulsification of an aqueous protein solution in methylene chloride (CH2Cl2) resulted in the formation of protein aggregates and a reduction in the specific enzyme activity. -Chymotrypsin showed substantial loss in activity and protein aggregation when it was homogenized with methylene chloride and encapsulated in poly(lactic-co-glycolic) acid (PLGA) microspheres by the water-in-oil-in-water (w/o/w) method. Co-dissolving the protein with maltose and polyethylene glycol (PEG, Mw 8000) in the first aqueous phase helped to preventing interface-induced protein aggregation and inactivation. It was found that those excipients efficient in preventing interface-induced aggregation and inactivation also led to reduced a- chymotrypsin inactivation and aggregation upon encapsulation in poly(lactic-co-glycolic) acid (PLGA) microspheres. Employing these excipients during w/o/w encapsulation led to a reduction in -chymotrypsin inactivation (10%) and aggregation (12%) upon encapsulation in PLGA microspheres. This demonstrates that the o/w emulsification step is the main stress-factor in the w/o/w encapsulation procedure. In addition, employing PEG as excipients in the organic phase prior to encapsulation decreased the amount of non-covalent aggregates inside the microspheres to 7% and the specific activity was 95%. In summary, by rationally selecting excipients efficient in stabilizing chymotrypsin during the first emulsification step, protein aggregation and inactivation were reduced during the w/o/w encapsulation.
Montano, Rubenier; García, Zulma; Arce, Rafael*, Department of Chemistry, University of Puerto Rico, Río Piedras
The effect of the nature of the surface on the photochemistry of adsorbed 1-nitropyrene on models of atmospheric particulate matter
Nitropolycyclic aromatic hydrocarbons (nitro PAH) are well known mutagenic and carcinogenic compounds formed either directly by combustion of fossil fuels, or by photochemical and chemical reactions of the parent polycyclic aromatic hydrocarbons in polluted atmospheres. Studies have been performed on the photochemical transformations of nitropyrenes adsorbed onto models of the atmospheric particulate matter in order to provide information on the fate of these contaminants in the atmosphere. The effect of the average pore diameter and of the nature of the surface on the mechanisms of photodestruction was studied. Samples of equal surface loading of 1-nitropyrene on Alumina, CaO, MgO, (NH4)2SO4 and on Silica of different average pore sizes (25, 60 and 150Å) were used to study the effect of these surface’s parameters on the photodegradation rates. Fluorescence and diffuse reflectance techniques were used to determine the photodegradation rate of 1-nitropyrene on these surfaces. Employing absorption measurements the amount of 1-nitropyrene adsorbed from equilibrated solutions with the adsorbents was determined. These measurements as well as diffuse reflectance spectra demonstrate that 1-nitropyrene adsorption is larger on Silica 60Å, Silica 25Å, and Silica 150Å surfaces (79, 75 and 65%, respectively) than on the other surfaces: alumina (~17%), CaO (19%), MgO (8%), (NH4)2SO4 (30%). However, 1-nitropyrene adsorbed on any of the surfaces mentioned above does not exhibit fluorescence, except on (NH4)2SO4 for which an emission band at lmax=540nm (lexc=409nm) is observed.
Morales-Cruz, Angel; Cabrera, Carlos R.*, Department of Chemistry, University of Puerto Rico, Río Piedras; Miranda, Félix A., NASA Glenn Research Center
Self-assembled monolayers at ferroelectric thin film of barium strontium titanate (Ba0.5Sr0.5Ti03) used for RF technology
Ferroelectric materials are an enticing prospect for incorporation into agile frequency microwave components including phase shifters, varactors, tunable filters, resonators and antennas. Thin films of the ferroelectric barium strontium titanate (Ba1-xSrx TiO3 (BSTO)) has been used in coupled microstrip phase shifters (CMPSs) for possible insertion in satellite and wireless communication platforms primarily because of their high dielectric constant, low loss, large tunability and good structural stability. In attempt to improve the figure of merit K of phase shifters (phase shift (degrees)/ dB of loss) of phase shifters, modification of the metal/ferroelectric interface of these devices was done through surface modification of the ferroelectrics layer using a self-assembled monolayer approach. The impact of this nanotechnology promises reduce RF losses by improving the quality of the metal/ferroelectric interface. In this study, compounds such as 3- mercaptopropyltrimethoxysilane (MPS), 16-mercaptohexadecanois acid (MHDA) and 3- mercaptopropionic acid (MPA) were used to form the self-assembled monolayers on the ferroelectric surface. As a result of the previous modification, chemical derivatization of the self-assembled monolayers was done in order to increase the chain length. Chemical derivatization was done using 3- aminopropyltrimethoxysilane (APS) and 16-mercaptohexadecanoic acid. Surface chemical analysis was done to reveal the composition of the derivatization via X-ray electron spectroscopy (XPS) and Fourier Transform Infrared (FT-IR). Low and high frequencies measurements of phase shifters were done in order to measure the performance of these devices for further insertion in antennas.
Morante, Tatiana; Rodríguez, Felipe; Cabrera, Carlos, Chemistry Graduate Program-University of Puerto Rico, Río Piedras Campus
Influence of ruthenium concentration on sequential and simultaneous electrodeposition of Pt-Ru electrocatalysts on HOPG substrate: a surface morphology and electrocatalytic study
Influences of Ru concentration electrodeposited by sequential and simultaneous lineal sweep potential techniques with Pt have been studied on previously activated HOPG substrates. RuCl3 and K2PtCl6 have been used as sources of Ru and Pt respectively. The concentration of 1mM, K2PtCl6 was constant in all the experiments, and RuCl3 concentrations have changed from 0.05 to 10mM. Sequential voltammetric results allowed determine loading of Pt, Ru and a complete catalytic evaluation, which is difficult to determine via simultaneous deposition. Morphological characterizations through scanning electron microscopy (SEM) and atomic force microscopy (AFM) have shown that the deposits are composed by aggregates particles of different shape and size forming clusters. Scanning tunneling Microscopy (STM) demonstrate that the tops of these clusters are nanoclusters from 5 to 10 nm. The distribution of these clusters on the HOPG surfaces is heterogeneous and disperses. The presence of Ru on the surface produce changes in diameter and height of clusters as compared with pure Pt clusters. XPS results show that Ru and RuOx or Ru(OH)x are the chemical species present on the electrode surface before methanol oxidation. The Ru amounts decrease remarkably after methanol oxidation experiments. The ratio of Pt-Ru surface concentration obtained via XPS and the electrochemical ratio follow the tendency of molar concentrations. Catalytic effect tested by cyclic voltammetry and chronoamperometry by methanol oxidation showed that the electrodes of Pt-Ru have an enhancement at the current density at least three times more than pure Pt nanoclusters.
Morera, Shakira; Guadalupe, Ana*, Department of Chemistry, University of Puerto Rico, Río Piedras campus
Homogeneous and electrochemical studies of NAD+ reduction catalyzed by pentamethylcyclopentadienyl(1,10-phenanthroline-5,6-dione)chloro rhodium(III) hexafluorophosphate
Nicotinamide Adenine Dinucleotide (NADH) function as the hydride donor in hundreds of enzymatic reduction reactions. In order to overcome the high cost in the regeneration of NADH, organic and inorganic mediators for the electrocatalytic reduction of NAD+ have been studied. These systems are attractive for the development of biosensors and industrial reactors. Studies of rhodium polypyridil complexes have been done for their potential application as homogeneous and heterogeneous catalysts. Following these studies [Rh(Cp*)(phend)Cl]PF6 was synthesized to study the chemical and electrochemical reaction with NAD+. UV-Vis, IR, ES-MS, and Cyclic Voltammetry were used to characterize the complex. Its catalytic activity was monitored following the production of NADH at 340nm. Turnovers between 7 and 453 hr-1 were obtained at different temperatures and Rh complex concentrations, varying the pH of a phosphate buffer solution. Current studies are geared to determine the reaction products and test the system efficiency when coupled to enzymatic reactions.
Ortiz, Yazmín; Reyes, Elba D.*, Chemistry Department, University of Puerto Rico, Cayey Campus
Composition of lipids from sunflower (Helianthus annus) collected in Puerto Rico
It is know that some tropical plants have therapeutic effects. However, little is know about which components of these plants is responsible of the therapeutic effect. Specifically the lipid composition of medicinal plants of Puerto Rico is a very interesting research area; therefore we have focused this work in the isolation and characterization of the fatty acid composition of the Sunflower (Helianthus annus). To obtain the crude extract the plants were extract with CH2Cl2. The organic components of the plants were separated using column chromatographic techniques and analyzed by GC-MS. Derivatization reactions were also performed to help in the GC-MS identification of the constituents. The composition of lipids from Sunflower identified by these methods will be presented. In addition, the lipid constituents will be compared with the composition from similar sunflowers collected in Canada.
Ortiz Barreto, Luis; Cádiz, Mayra E. *; Hernández, Samuel P. *, Departamento de Química, UPR-Mayagüez
Preparation of silver surfaces for SERS analysis of DNA bases
The Surface Enhanced Raman Scattering (SERS) technique is very useful for trace analysis, also allowing the study of biological systems in aqueous media. Very strong enhancement of the vibrational bands is obtained by absorbing the samples onto the surface of metal islands or colloids. In this project, glass surfaces were covered by the SERS active silver substrate using the mirror reaction method. Rhodamin6G at micro molar concentrations were used to evaluate the degree of enhancement. Experiments were made to determine if the spectrum of Rhodamine6G varied with changes in the area of the silver film being probed, and with time. No significant variations were observed. In addition, the spectrum of adenine at micro molar concentration was recorded. Adenine marker bands were identified at 724 cm-1, 1309 cm-1 and 1442 cm-1, among others. The method proved to be effective for the study of molecules with delocalized pi-systems, such as DNA bases. The study of platinum anticancer complexes and their reactions with biologically relevant molecules such as DNA, adenine, and guanine, among others is in progress.
Oyola Cintrón, Jessica; Fuentes, Lymari; Quiñones, Edwin*, Department of Chemistry, University of Puerto Rico, Río Piedras campus
Studies of physical and chemical changes of Azurin from Pseudomonas aeruginosa
The immobilization of proteins in porous materials allows the study of their chemical and thermal stability under non physiological conditions with the purpouse of developing sensing devices. Azurin from Pseudomonas aeruginosa was used to study the conformational changes and the chemical reactions of the entrapped protein in a sol-gel matrix. The chemical stability of azurin was studied using guanidine hydrochloride (Gnd HCl) as the denaturing agent. The chemical denaturation of azurin was studied by monitoring the red shift in the fluorescence band of tryptophan (Trp). Values of ?G (chemical denaturation) of 14.42 and 11.13 kcal/mol were calculated for azurin in solution and in the sol-gel, respectively. Also, we studied the thermal stability of the protein. For this study we report experiments of the thermal denaturation of azurin free in solution. These experiments showed the presence of an intermediary in the denaturation reaction. The thermal denaturation was also detected by monitoring the red shift of the Trp band in fluorescence. To corroborate the presence of the intermediary state we report experiments using acrylamide as a quencher. The results of these experiments showed that there are three species involved in the denaturation. Finally, spectroscopic evidence of the reduction and removal of the copper ion is presented.
Pérez, Naydi; Santos Santori, Lizette*, Chemistry Department, Pontifical Catholic University of Puerto Rico
Efecto de furafulina e isoniazida en el sistema de Citocromo P-450 de Santalum album
El sistema citocromo P-450 es un grupo de enzimas molecularmente activas. El método principal de acción de las enzimas de este sistema es el de introducir un grupo funcional al compuesto lipofílico, o sea, hacerlo mas hidrosoluble, y por lo tanto, mas facilmente excretable. Tiene un espectro de absorción en la frecuencia de 450nm, de ahí su nombre, y además tienen un pigmento que es el componente final de la cadena transportadora de electrones que catalizan la oxidación de sustratos. En esta investigación se utilizó la planta del árbol científicamente conocido como Santalum album, que proviene de la familia Santaláceas y es utilizado medicinalmente para tratar condiciones de la piel (acné, disentería, gonorréa). El objetivo principal de esta investigación es determinar si la presencia de Furafulina e Isoniazida afectan el complejo enzimático de citocromo P-450. La primera fase de ésta investigación consistió en tratar la planta con estos compuestos: Furafulina como inhibidor e Isoniazida como inductor. Habían dos grupos controles uno de agua y otro DMSO. Luego del tratamiento preparamos los microsomas y se realizaron los siguientes ensayos: Contenido total de proteína, Determinación del complejo enzimático Citocromo P-450, Actividad enzimática de NADH Citocromo C Reductasa. Los resultados preliminares del tratamiento con furafulina fueron: Proteína total 0.7208 mg/ml, CYP 450 2.7, NADH reductasa 24.18. Los resultados del tratamiento con Isoniazida fueron: Proteína total 0.5975 mg/ml, CYP 450 7.67, NADH reductasa 1059.24. Debido a que estos resultados son preliminares, realizaremos una segunda fase que consiste en realizar nuevamente los ensayos para coroborar los resultados de la data obtenida. Además se realizarán ensayos más específicos que definan la presencia de ciertas enzimas encontradas en el Citocromo P 450.
Perocier López, Yajaira; Rivera Montalvo, Luis A.*, Arts and Sciences, Department of Chemistry, University of Puerto Rico-Mayagüez
Optimization of n-alkylation of 2-methylbenzimidazole under phase-transfer conditions
The objective of this research project is to assess the optimum reaction parameters for the n-alkylation of 2-methylbenzimidazole under phase-transfer catalysis. Previous synthetic efforts involved different catalytic agents, solvent system and temperature conditions. In our hands, we focused attention on the nature of the catalytic agent and tryed to optimize reaction conditions. The system studied was the reaction between 2-methylbenzimidazole and isopropyl bromide in the presence sodium hydroxide. Details of the use of the solvent system and reaction conditions (temperature, reaction times, catalytic agent) used will be presented. The nature of the catalytic agent used was the most critical parameter.
Prieto Figueroa, José, Ciencias Agrícolas, Departamento de Protección de Cultivos, UPR- Mayagüez; De Jesús Echevarría, Maritza; Rodríguez, Rodríguez, Lolita; Souto Bachiller, Fernando*, Departamento de Química, UPR - Mayagüez
Evaluación de tagetes patula como control biologico de nematodos fitoparasíticos: perfil químico de la raíz
Un gran reto para la ciencia en estos días es la búsqueda de alternativas más seguras para proteger los cultivos de las plagas que, con el tiempo, han desarrollado resistencia a los métodos tradicionales de control. La capacidad de muchas plantas de producir compuestos repelentes o específicamente tóxicos a organismos fitoparasíticos nos puede servir como una alternativa para la producción de alimentos sin contaminar el medioambiente. En esta investigación se estudió la capacidad de la planta Tagetes patula de bio-sintetizar compuestos repelentes o tóxicos a nematodos fitoparasíticos utilizando técnicas de cultivo in-vitro, cromatografía de gas acoplada a un espectrofotómetro de masas (GC-MS) y extracción de constituyentes orgánicos tipo Soxhlet. Se hicieron extracciones de las flores, raíces, hojas y tallos encontrándose, tentativamente, cinco constituyentes con propiedades nematicidas. Los compuestos encontrados conocidos como tiofenos fueron los siguientes: 5-(4-acetoxi-1,2,2-bitienil (C14H12O2S2), tertiofeno (C12H8S3), thriantreno (C12H8S2), 5-(3-buten-1-inil)-2,2’-bitienil (C12H8S2), 3-feniltiopental -1,3-dieno (C11H12S). Estos compuestos se hallaron principalmente en las raíces tanto en cultivos in-vitro como en las plantas cultivadas en tierra, siendo en las plantas cultivadas en tierra donde mayor concentración de los mismos se pudo observar. Estos resultados concuerdan con los presentados recientemente en la literatura por Lilla Marl, Andras Tei, István Gyurján y Michael Wink (2002). Los resultados preliminares de esta investigación son alentadores ya que las técnicas utilizadas para extraer los constituyentes con propiedades nematicidas y para establecer los cultivos, resultaron ser eficientes y sencillas, dos características que son cruciales para la utilización de estos productos en la agricultura.
Quiles, Débora; Tirado, Liz M.; Alejandro, Felix; Guadalupe, Ana R.*, Chemistry Department of Chemistry, UPR-Río Piedras
Multilayer assembly of functionalized polymers in electrodes surfaces
Our research goal is to study the potential application of multilayer polymeric assemblies for the construction of dehydrogenase biosensors. To construct these assemblies, it is necessary to deposit in a sequential and alternate fashion a polycation (PC) and a polyanion (PA). In our case, the PA will be polyacrylic acid and the PC will be a ruthenium derivatized polycation. Ruthenium complexes are known to be chemically stable compounds, they are chemically and electrochemically reversible, and can act as redox mediators between redox active enzymes and electrode surfaces. This research involved the synthesis of 4-vinyl-4’-methyl-2,2’-bipyridine (vbpy), [Ru(phen)2]Cl2 and [Ru(phend)2(vbpy)](PF6)2 where phen is 1,10-phenathroline and phend is 1,10-phenathroline-5,6-dione. A temperature responsive polymer named N-isopropylacrylamide (NIPAAm), immobilized with [Ru(phend)2(vbpy)](PF6)2 and Nicotinamide Adenine Dinucleotide (NAD+), will act as the PC. The polymeric assemblies so constructed will be tested for the detection of ethanol in the presence of alcohol dehydrogenase enzyme. Results on the synthesis and characterization of the ruthenium complexes using 1H-NMR, IR and cyclic voltammetry techniques will be presented as well as initial results on the polycations assembling. Electrochemical studies will be conducted to study the potential of this approach for the construction of biosensors.
Rentas, Kenny; Rutzen, Hans; Dávila, Kariluz; Rosario, Osvaldo*, Chemistry Department, University of Puerto Rico
Method development for non invasive analysis of exogenous substances using sweat as biological matrix extracted with ultrasonic probe
We are exposed daily to pollutants in our environment. Methods using blood, urine and feces as well as other have been developed to monitor their bioaccumulation. However, in addition to difficulty and risks in their collection, complexity in composition of these matrices leads to interferences. Sweat has been shown to be a practical medium to monitor controlled additive drugs as well as nicotine. Among the advantages of sweat are those like compositions presents less interferences and it can be collected less intrusively. Sweat is sampled on adsorbent pads which also trap the analytes. For final analysis removal from the adsorbent matrix must be effected. Ultrasonic Probe extraction is widely used for the extraction of particulate trapped on filters. Ultrasonic extraction has been tested by our group for sweat samples on adsorbent pads. However ultrasonic extraction of cellulose pads on which was deposited spiked artificial sweat has not been effective, even with different solvent media. We are presently testing this extraction approach with glass fiber pads prior to taking real samples.
Rivera, Casandra; Quiñones, Luis; Morales, Reginald*, Department of Chemistry, University of Puerto Rico, Río Piedras; Quesada, Orestes *, Department of Physical Sciences, University of Puerto Rico, Río Piedras
Probing the interaction of methylchlorpromazine with membranes using different PLA'S
The interaction of methylchlorpromazine (MCP) a cationic lipophilic agent synthesized from the widely used antipsychotic drug chlorpromazine (CP) with membrane lipids was studied using two phospholipases A2 (PLA2) from different snake venoms. Studies in which the intact human erythrocytes were incubated with low, non-hemolytic levels of methylchlorpromazine (75-250 nmole added/mL cells) clearly showed that these levels had no effects on either binding or hydrolytic rate of the Naja nigricollis PLA2. On the other hand, the same levels significantly decreased both bind and hydrolysis by the PLA from Agkistrodon halys. Since the A. halys PLA has been shown to interact with a surface protein, but PLA from N. nigricollis binds primarily to lipid, we propose that, at least at low levels, methylchlorpromazine is sequestered in the vicinity of membrane proteins.
Rivera, José; Pérez, Caroline; Griebenow, Kai*, Department of Chemistry, UPR-Río Piedras
Adsorption of lysozyme to poly(lactic-co-glycolic) acid and the effect of additives
Poly(lactic-co-glycolic) acid (PLGA) is the most widely used and thoroughly studied bioredodible polymer for the sustained delivery of protein drugs. Nevertheless, PLGA-based controlled release vehicles are not without problems. Protein drugs might adsorb to the hydrophobic polymer what might cause aggregation and incomplete release. Protein adsorption has been proposed to cause loss in bioactivity and unpredictable release kinetics. Lysozyme has long been known to undergo extensive adsorption to hydrophobic polymers and thus constitutes a good model to critically evaluate the use of additives to minimize adsorption of protein to the polymer matrix. Fluorescence spectroscopy was used to study the conformation of hen egg white lysozyme (0.3 mg/ml, pH 5.1) as a function of temperature in the presence and absence of PLGA. In the presence of PLGA the melting temperature decreased to 66±4ºC when compared to that of lysozyme in buffer (72 ± 2ºC) and thermal unfolding was not completely reversible. UV-Vis spectroscopy demonstrated that unfolding of lysozyme caused its irreversible adsorption to PLGA. In addition we studied the effect of the additives poly ethylene glycol (PEG, MW 5000) and lactulose at 0.3 mg/ml on the thermostability and adsorption of lysozyme to PLGA. Fluorescence and UV-Vis data indicate that the additives restore thermostability of lysozyme and prevent its adsorption to PLGA. Thermal denaturation experiments were reversible in the presence of the additives while they were not when lysozyme was exposed to PLGA in their absence. In conclusion, for the first time it has been demonstrated that unfolded proteins are prone to adsorption to hydrophobic polymers. Furthermore, excipients can prevent this adsorption. These findings may hold promise in improving drug delivery devices.
Rivera, Evelyn, University of Puerto Rico-Mayagüez; Cleveland, Taina M.*, Chemistry, Norfolk State University (VA) Noginov, Maxim Ocean Lake High School, Virginia Beach
Aerosols in the troposphere
Aerosols are microscopic particles of liquid or solid suspended in the atmosphere. They can be originated from many natural sources such as volcanic ash, desert dust, and haze, and anthropogenic sources such as industrial pollution, fly ash, fossil fuel combustion, and biomass burning. Aerosols affect the Earth Radiation Budget (ERB) in two ways: by the scattering and absorption of incoming sunlight and the absorption and emission of outgoing infrared radiation (direct effect), and by the modification of the optical properties and lifetime of clouds (indirect effect). Although significant understanding on the global climatological effects of aerosol exists, the regional effects need further study. The motivation of this work is to compare the aerosol optical and microphysical properties between Norfolk State University’s (NSU) land and CERES Observation and Validation Experiment’s (COVE) ocean sites. This will be accomplished by the comparison of the variations in aerosol optical thickness (AOT) and size distributions together with trajectory analysis to determine their sources of origin. The aerosol data was obtained from AERONET (AErosol RObotic NETwork), and the air masses were tracked using Hysplit 4 (Hybrid Single-Particle Lagrangian Integrated Trajectory).
Rivera Guzmán, Leslie A.; Rivera Montalvo, Luis A.*, Chemistry Department,
UPR-Mayagüez
The development of pyrene as a non-invasive thermal sensor
Surfactants are used in a wide variety of industrial applications. Extensive research has been done on mixed surfactants systems, since they can show superior performance as compared to single surfactant system alone. The present study attempts to explore the influence of molecular association between anionic and cationic surfactant mixtures on surface properties, such as surface tension, surface viscosity and conductivity. The combination of anionic surfactant, sodium dodecyl sulfate (SDS), and one of the three different cationic surfactants: dodecylammonium chloride (DAC), cetylpyridinium chloride (CPC), and cetyldimethylbenzylammonium chloride (CDBAC), leads to strong ion-ion interactions, thereby significantly influencing the interfacial properties. In an attempt to increase the solubilization of pyrene in a micellar aqueous solution, an appropriate cationic-anionic surfactant combination was chosen. The selected combinations of the mixed surfactant were the results of the interfacial studies mentioned above. The solutions are prepared in a 25 mL volumetric flask and the pyrene concentration of the solutions is 5.0 mM. Different solutions were prepared depending on the interfacial studies. Fluorescence measurements were achieved at different temperatures (C) in a range of 250-600 nm using a 337 nm excitation wavelength for the solutions used.
Rivera Ruiz, Luis D.; Casanova, Orlando; Ortiz Marciales, Margarita*, Departamento de Química, University of Puerto Rico, Humacao
Borane trifluoride catalyzed borane reduction of O-silyloximes
Amines are very important organic compounds used as intermediates for the synthesis of a variety of pharmaceutical products. The reduction of aromatic oxime ethers by borane and organoboron reagents have been known to afford the hydroxyl amine or the amine depending on the structure and reaction conditions. Previously, we have reported the formation of N-alkylanilines in the reduction of aromatic O-silylated oximes with borane in THF under reflux conditions. The yield of the expected arylalkylamine with respect to the secondary aniline depended strongly on the electronic effects of the substituents on the aromatic ring and on the steric effects of the silicon substituents. Now, we have investigated the effect of cyclic ring systems, such as indanone and tetralone, on the reduction of O-TBS oximes with borane under reflux conditions. We observed that BF3-etherate catalyzed the reduction of these O-silyloximes, and in addition, the methoxy substituted aromatic oxime provided mainly the secondary amine with high yield. This method contribute to the development of a new benzazepine synthesis.
Rosario Medardo; Betancourt, José; Carballeira, Néstor*, Chemistry Department, University of Puerto Rico-Río Piedras; García-Arrarás, José E.*, Department of Biology, University of Puerto Rico-Río Piedras
Lipid metabolism during the process of regeneration in Holothuria glaberrima
Holothuria glaberrima (sea cucumber) is an echinoderm with an amazing capacity to regenerate its organs following chemically induced evisceration. During the 3 weeks of regeneration the sea cucumber has no functional intestine, thus cannot undergo normal digestive processes. In order to survive during this period nutrients must be mobilized from other tissues. We have studied the metabolism of lipids to determine the changes in phospholipid fatty acid composition of the sea cucumber wall during the regeneration process. An isolation scheme involving organic extraction and gas chromatography was used for this purpose. Normal and regenerating animals at days 7, 14, 21, 28, following induced-evisceration were selected. Our results will provide a profile of the phospholipids fatty acid composition at each stage of regeneration and the quantitative fluctuations of phospholipids during regeneration. The study of this process will provide better understanding of metabolic changes during intestinal regeneration and more important,how these animals survive without food ingestion over prolonged periods.
Funded by AMP and NIGMS SCORE and RISE Programs.
Rosario-Castro, Belinda; Lozada, Dafne; Cabrera, Carlos*, Chemistry Graduate Program,
UPR-Rio Piedras
Development of a methodology for the preparation of ordered single-wall carbon nanotubes films by self-assembled monolayers techniques
Single-wall carbon nanotubes (SWNTs) are very interesting materials because of their morphology, semiconducting characteristics, and electronic and mechanical properties. Its morphology (high length-to-diameter ratio) and electronic properties suggest potential application for SWNTs as hydrogen storage material for fuel cells, and as anodes for lithium ion batteries. The introduction of SWNTs on these types of sources systems will improve their performance, efficiency, and capacity to store energy. SWNTs from commercial sources are usually impure. Impurities typically found in as-prepared SWNTs are metals used as catalysts for their growth, and amorphous carbon. These have to be removed in order to be able to study its properties and obtain the optimal performance on its various applications. A purification method has been applied for the removal of Fe catalysts from CNI SWNTs. This method combines the well-known acid reflux treatment and gas phase oxidation process. The goal of this project is the development of a self-assembled methodology for the preparation of ordered or aligned carbon nanotubes on platinum electrode surfaces. Self-assembled monolayer (SAM) of 4-aminothiophenol were deposited on Pt electrodes, in order to obtained an amino-terminated SAM. This amino SAM was characterized by electrochemical measurements, X-ray photoelectron spectroscopy (XPS), Fourier-transforms infrared (FTIR) spectroscopy, and Raman spectroscopy. Carbon nanotubes were deposited over the amino-terminated SAM by an amide bond formed between SAM amino groups and carboxylic acid groups at the open ends of the carbon nanotubes. This deposition was characterized using Raman spectroscopy and Scanning electron microscopy (SEM). The possibility of using high-surface-area nanostructure of SWNTs (nanothecnology) for energy storage may allow for smaller, lighter and more efficient batteries and fuel cell systems.
Rutzen, Hans; Rentas, Kenny; Davila, Kariluz; Rosario, Osvaldo*, Departamento de Química, Universidad de Puerto Rico-Río Piedras
Method development for non invasive analysis of exogenous substances using sweat as biological matrix extracted with thermal desorption
People are continuously exposed to exogenous substances that could affect their health. Many well-established procedures have been used to document this exposure. These include blood, urine, feces, among others. A disadvantage for these different matrices is that some are invasive, causing stress in the patient thereby creating problems in the collection. Another is the composition of the matrices is a problem because they are complex and other substances could interfere with the separation and identification in the analysis. If we use a matrix easy to collect and with less problems of composition, the analysis will be more practical. The tendency to explore non-invasive techniques such as sweat is growing. In recent years sweat has arisen as a matrix to analyze exogenous substances like controlled addictive drugs and nicotine. Advantages with sweat are: non-invasive, easy collection and the composition presents less problems or complications to separate and identify compounds of interest. Thermal Desorption (TD) has proven to be a powerful approach for the removal for subsequent analysis of low concentrations of compounds in different matrices. We have been exploring the use of direct thermal desorption of adsorbent patches used for sampling sweat. Reproducibility and limits of detection are being evaluated using spiked artificial sweat. Initial results look encouraging. In the future TD-GC-MS will be performed on patches taken on actual persons.
San Miguel, Lidaris; Guadalupe, Ana R.*, Chemistry Department, Universidad de PuertoRico-Río Piedras; Fonseca, L. F.*; Resto, O., Physics Department, UPR-Río Piedras Porous silicon multilayers for chemical detectors
Multilayered Porous Silicon films were synthesized and their change in reflectivity used for chemical detection. Molecular imprinting technique was proposed for improving detection selectivity. We describe the synthesis procedures for porous silicon multilayers and the silica gel filling material. The optical and structural properties of the films are presented. The impregnation process and the advances on the molecular imprinting of phenol and naphtol are discussed.
Sanabria-Rios, David; Cruz, Clarisa*; Carballeira, Néstor, M.*, Department of Chemistry, University of Puerto Rico, Río Piedras
Synthesis of new acetylenic fatty acids for topoisomerase I inhibition
The design of small molecules that bind to deoxyribonucleic acid (DNA) and its Topoisomerases I and II, is an active research area. The Topoisomerases I and II perform their functions by introducing transient protein-bridged DNA breaks on one (Topo I) or both DNA strands (Topo II). One possible way of Topo I inhibition is by DNA binding in the site where the enzyme binds. Topo I inhibitors constitute a family of antitumoral agents that can be used for cancer treatment. Some long-chain unsaturated fatty acids such as 9-octadecynoic acid, isolated from marine sponges, have been reported as DNA Topoisomerase I inhibitors. In this case the 9-octadecynoic acid, isolated from Schoepfia californica, has been reported as an agent that binds to DNA. This acid does not possess any of the structural characteristics of known molecules that bind to DNA. Therefore, its mode of interaction with DNA seems to be unprecedented. For these reasons, we have undertaken the total synthesis of delta 9-acetylenic analogues of 9-octadecynoic acid such as 9-hexadecynoic acid and 14-methyl-9-pentadecynoic acid in order to study their potential as new DNA Topoisomerase I inhibitors. Our efforts towards to the synthesis of these acetylenic fatty acids will be presented.
Santamarina Rodríguez, Lourdes M.; Rivera Montalvo, Luis A.*, Department of Chemistry, UPR-Mayagüez
The development of Rhodamine B as a non-invasive thermal sensor
The technique of using a mixture of dyes was proposed because it could, in principle, avoid the variation in exciting light intensity due to refraction of the light passing through the thermal field and other effects. These fluorescent dyes selected should show emission intensities, which depend differently upon temperature. The non-temperature-sensitive dye must have an absorption spectrum similar to Rhodamine B (RhB) but a different emission band. Rhodamine 110 (Rh110) has similar spectral characteristics (wavelength of absorption= 496 nm, wavelength of emission= 520 nm), and its temperature dependence is much smaller (0.13 % K-1). Diluted aqueous solutions of RhB and Rh110 were prepared containing different milligrams per liter (mg/L) proportions of RhB to Rh110. All of these solutions were tested individually for variability and sensitivity with temperature, reversibility and reproducibility with very good results. A graph of the intensity ratio against temperature, from 15 C to 105 C as a function of the concentration ratio was prepared. It shows that the concentration ratio affects the intensity ratio and its sensitivity to the temperature. The concentration ratio at which the maximum sensitivity can be realized would be determined from a graph of the variation of the temperature sensitivity against the CRhB / CRh110. Also, it has been reported that by adding surfactant to rhodamine B especially anionic surfactants it increases the solution fluorescence. To observe if this fills our needs, rhodamine B 0.05 mM was mixed with four different surfactants at their critical micellar concentration. Fluorescence measurements were achieved at different temperatures (C) in a range of 250-750 nm using a 550 nm excitation wavelength for the solutions used.
Silva, Jenny; Oyola, Rolando; Piñero, Luis E.; García, Carmelo*, Chemistry Department,
UPR-Humacao
Protriptyline and dibenzocycloheptene fluorescence quenching by diethyl and tri ethyl amine: A simple model for drug-protein interaction
Protriptyline (PTL), a tricyclic antidepressant drug, is a skin photosensitizing agent in humans. It has been proposed that PTL acts by both photodynamic and non-photodynamic processes. A recent report of our group showed that its fluorescence and triplet excited state quantum yields are solvent dependant. This solvent effect has been attributed to different solvated species of the PTL hydrochloride or to an inter/intramolecular interaction between the amine terminal and the dibenzocycloheptene moiety (DBCH). In this work we study the interaction between the DBCH moiety with several amines and determined the Stern-Volmer quenching constant (KSV). This information is relevant to elucidate if the quenching mechanism is static or dynamic and to determine if an inter or intramolecular quenching process is the dominant pathway. Moreover, since it is known that PTL interacts with several proteins at the cellular level, it is important to known if there is any interaction between the PTL excited states and the amino acids with terminal amino groups. This work reports the quenching of the fluorescence of PTL-HCl, PTL free base and DBCH by diethylamine and triethylamine in water, acetonitrile and cyclohexane.
Souto, Natacha; Cadiz, Mayra*; Hernández Samuel*, Departamento de Química, UPR- Mayagüez
Síntesis de un derivado de cisplatino con 2, 5, 6-trimetilbenzotiazol
El cisplatino, cis-[PtCl2(NH3)2] es uno de los compuestos más efectivos en quimioterapia, específicamente en el tratamiento de cáncer del testículo y cáncer de ovario germinal. Recientemente se han diseñado derivados de cisplatino que poseen impedimento estérico y evitan los mecanismos de resistencia celular al disminuir la remoción del complejo causada por glutatión y otros tioles. El propósito de esta investigación es sintetizar y estudiar la actividad anticancerígena del complejo cis-diaminocloro-(2, 5, 6-trimetilbenzotiazol). Además, se estudiará su reactividad con DNA y con metionina, modelo de proteínas que contienen azufre. Para la síntesis de este compuesto, se llevaron a cabo reacciones de sustitución de ligando a partir de cisplatino. Para confirmar la identidad del compuesto este se sometió a análisis elemental, NMR de 1H, espectroscopia Raman e IR lejano. La técnica de Raman fue especialmente útil en la caracterización de las vibraciones Pt-ligando.
Suárez Fuentes, Christian, D.; Ortiz, Denisse; Carballeira, Néstor*, Chemistry Department, University of Puerto Rico, Río Piedras
Synthesis of (5Z,9Z)-2-methoxy-5,9-hexadecadienoic acid
The compound (5Z,9Z)-2-methoxy-5,9-hexadecadienoic acid is an analog of the naturally occurring (5Z, 9Z)-2-methoxy-5,9-hexacosadienoic acid acid. Just recently, we have found that the 2-methoxy fatty acids have a cytotoxic effect on human leukemia cells. In addition, experimentations with animals have confirmed that several fatty acids, like linoleic acid, inhibit skin, breast, colon and stomach cancers. Recent studies in our group have also established that iso-methylated of 2-methoxy fatty acids inhibit the K-562 leukemia cell line. Therefore, we were interested in testing the aforementioned fatty acid against several cancer cell lines and for this purpose we developed a total synthesis for this fatty acid. The synthesis of 2-methoxy-5,9-hexadecadienoic acid started with the coupling of 1,5 hexadyine with 1-bromohexane, since both of these compounds are commercially available. The total synthesis of this compound will be presented.
Vázquez, Emanuel; Santos, Orly; Reyes, Elba, Chemistry Department,
University of Puerto Rico-Cayey
Lipid composition from Curia (Justicia pectoralis) a medicinal plant collected in Puerto Rico
Many use plants from their gardens for therapeutic effects. In an effort to characterize possible active ingredients some researchers work in the isolation and characterization of organic compounds. In this research we are looking specifically at the lipid composition of Curia “Justicia pectoralis”. We have isolated and characterized the fatty acid composition from a Curia extract. The method that we used to obtain the crude extract is sonication using CH2Cl2 as solvent. The organic components of the extract were separated and analyzed by different chromatographic techniques. The results of the GC-MS analyses will be presented.
Vélez, Meredith; Santiago Berríos, Mitk'El B.; Guadalupe, Ana R.*; Colón, Jorge L.*, Chemistry Department, UPR-Río Piedras
Electrochemical characterization of bis(1,10-phenanthroline-5,6-dione)bipyridine ruthenium(II)-exchanged zirconium phosphate for the electrooxidation of NADH
We are interested in the construction of electrochemical biosensors using zirconium phosphates inorganic solids. Zirconium phosphates (ZrP) are acidic, inorganic, ion exchangers with layered structures, which have been extensively investigated. We are investigating the use of these materials as hosts for electron mediators. The heterogeneous interlayer microenvironment can have profound effects on the rate of chemical reactions occurring within the solid. We are using the inorganic complex bis(1,10-phenanthroline-5,6-dione)bipyridine ruthenium(II) ([Ru(phend)2(bpy)]2+) as the electron mediator in our layers. This complex has been previously used in the preparation of biosensors, but we are using it for the first time in this more rigid environment. Cyclic voltammetry experiments showed that [Ru(phend)2(bpy)]2+ remains electroactive within ZrP. We have used [Ru(phend)2(bpy)]2+-exchanged ZrP to determine the electrooxidation of NADH in a buffer environment. This presentation includes the electrochemical characterization of this material and the electrooxidation of NADH.
Vitelli, Alison, Department of Chemistry, UPR Cayey; Chiesa, Ricardo*, Biology Department, UPR Cayey
Fos-related antigen-1 (Fra-1) expression in the rat Amygdala might be involved in acquisition and consolidation of emotional memories
Memory consolidation is thought to involve a series of molecular events requiring transcriptional gene regulation, which eventually ends in long-term changes at the synapse. We found, by Western Blot analysis, a decrease in phosphorylated extracellular-signal regulated kinase 1 and 2 (ERK1/2) in amygdala protein extracts from conditioned taste aversion (CTA) trained animals at 1 hour and 6 hours after conditioning. Western Blot analysis also showed a decrease in the levels of cAMP Responsive Element Modulator Protein (CREM), at 1 hour after conditioning. We partially tested our model, which states that the molecular events leading the acquisition and consolidation of emotional learning is initiated by ERK1/2 inactivation, CREM, NOR-1 and Fra-1. We did Western Blot analysis for the transcription factor Fra-1 using protein extracts of CTA trained animals sacrificed at different time-points. The highest levels of Fra-1 were at early time-points, which suggest a role for Fra-1 in memory acquisition modulating other genes involved in learning and memory formation. We believe that the molecular events modulating the generation of a strong emotional memory, such as the one generated in CTA, is involved in other learning experiences or psychoemotional disorders, involve associative relations between different events, similar to the associative learning involved in CTA.
Rosado Román, Israel, Moll, Victor, Universidad Interamericana, Recinto de Arecibo
Análisis Vibracional y Cálculo de Propiedades Termodinámicas de Hidroxilamina
Programas computacionales disponibles, tales como Cache o Gaussian 98, permiten hacer estudios teóricos de sistemas químicos, tanto sencillos como de alta complejidad. Este trabajo hace un estudio de la estructura de la hidroxilamina gaseosa, cálculo de sus propiedades termodinámicas y análisis de la respuesta vibracional de los distintos enlaces presentes en la molécula.
Además, se desarrolla un análisis del enlace N-O a través del cálculo de su curva de energía potencial. Simulaciones de este tipo de curvas se pueden obtener a partir del programa computacional de Gaussian 98 utilizando diversos métodos y cuyos resultados permiten encontrar mediante un ajuste de mínimos cuadrados una serie de parámetros, tales como la energía de disociación de enlace, constantes de fuerza y longitud de enlace en el equilibrio.
La investigación presentada en este trabajo se desarrolló gracias a los fondos aportados por el proyecto MSEIP en Química, “Integration of Chemistry and Biology through Molecular Modeling ” y el apoyo de la Universidad Interamericana de Puerto Rico.
Cuadrado, Wanda, UPR-Río Piedras, Department of Chemistry; Diaz, Cristina Montes, Ingrid*
A Green Chemistry Multi-step Synthesis of Ferrocene Derivatives Using the Guided Inquiry Approach
Many students have difficulties understanding and applying concepts, finding relevance and transferring knowledge within and across disciplines. New learning strategies have been introduced to meet student’s needs and interests. A commonly used method to teach laboratory skills is the guided inquiry approach, which focuses on the dynamic nature of chemistry. This presentation describes a Green Chemistry multistep Ferrocene derivatives synthesis experiment, designed using the guided inquiry approach. By a multistep synthesis of ferrocene derivatives in the organic chemistry laboratory, students will learn fundamental knowledge of Green Chemistry, organometallic synthesis, analyze the results, collaborate with others, reach sound conclusions, report and discuss their findings, and enhance their knowledge and skills in the use and interpretation of FT-IR and H-1 and C-13 NMR spectroscopies. Some innovative application of this chemistry will be also discussed
Rodríguez, Víctor*UPR-Río Piedras, Department of Chemistry, Montes, Ingrid
What is Beyond the University of Puerto Rico-Río Piedras ACS Student Affiliate Program?
ACS Student Affiliates Chapters can be instituted as an additional effective experiential education platform that can complement the learning objectives. In this presentation we will discuss how the University of Puerto Rico-Río Piedras Campus' ACS Student Affiliate Chapter enhances the educational experience of undergraduate students through the participation in a variety of social and science oriented activities, of interest to its members, that:
1. Promote intellectual development by engaging students actively in using strategic and integrative thinking skills to solve the inevitable problems inherent in projects that are implemented in the real world where uncertainty and change characterize the context.
2. Develop entrepreneurial and problem-solving skills by encouraging students to create and implement chapter projects.
3. Assist in career development by encouraging networking, teamwork, effective communication, organizational skills, and exploration of career options.
4. Develop character by encouraging a strong work ethic, initiative and motivation, and build self-esteem and self-insight.
Galarza Karylin* Pontifical Catholic University of Puerto Rico; Infante, Gabriel A. Departamento de Química, Universidad de Puerto Rico en Cayey, Morales, Daisy, Centro de Investigaciones Científicas, Rev. T. Giangiacomo, PUCPR.
Análisis de metales pesados en las aguas subterráneas circundantes a vertederos de desperdicios sólidos
Utilizando la técnica de Espectroscopía de Emisión de Plasma Acoplado Inducido y el método analítico establecido por la Agencia de Protección Ambiental (APA) se determinaron cualitativa y cuantitativamente los metales: Al, Na, K, Ca, Mg, Cs, Ba, Fe, Mn, Pb, V y Zn en las aguas subterráneas circundantes a los vertederos de desperdicios sólidos en las municipalidades de Hormigueros y Yauco en Puerto Rico. Las determinaciones de estos metales se realizaron a dos largos de onda diferentes para limitar posibles interferencias. Las concentraciones de algunos de estos metales especialmente Fe, Zn y Mn sobrepasaron los límites establecidos por las agencias reguladoras. Se discutirá la implicación de estos resultados en la contaminación ambiental de los acuíferos de la región sur de Puerto Rico.
González Santos Maryliz* Pontifical Catholic University of Puerto Rico, Dept of Chemistry; Montealegre, Federico, Ph.D. Departamento de Microbiología, Escuela de Medicina de Ponce
Análisis de pureza de partículas de heces fecales de ácaro por medio de fluorescencia
El asma es una enfermedad que con frecuencia es secundaria a las alergias, y los factores que pueden afectar esta enfermedad pueden encontrarse tanto dentro como fuera de la casa. Uno de ellos en el hogar, que con mayor frecuencia dan problemas de índole alérgico al paciente asmático, son los ácaros, los cuales se alimentan de la descamación del ser humano. Estos se encuentran en almohadas, muebles, peluches, etc. La alergia se produce al estar en contacto con las heces fecales de estos artrópodos. Actualmente se están realizando estudios y extracciones de proteínas antigénicas en las heces fecales de los ácaros para los cuales es necesario cultivar y crecer ácaros, así como extraer las heces del medio de alimentación y cuerpos de ácaros. En vías de optimizar los métodos de extracción, que incluyen pasar las muestras de cultivo a través de diferentes filtros, disminuyendo el diámetro de apertura, se midió la presencia de heces fecales utilizando el microscopio de fluorescencia luego de cada paso. Nuestra hipótesis es que, dado a que las partículas de comida no son fluorescentes y las heces sí, podemos apreciar una forma indirecta de pureza.
Rodríguez, María de L.* Pontifical Catholic University of Puerto Rico, Dept of Chemistry, Santos Santori, Lizette
Determinación de la concentración de metales en cuerpos de agua de Ponce y Guayanilla.
Las aguas superficiales están siendo contaminadas por metales que son adversos a los ecosistemas y a la salud. El propósito del estudio es determinar por un período de diez meses la concentración de metales con el fin de medir la calidad del agua en los pueblos de Ponce y Guayanilla. El tipo de estudio es de carácter experimental. Se utilizaron tres muestras de los lugares establecidos. Las muestras fueron tratadas con 3ml de HNO3 para preservarlas y digestadas para ser analizadas en el ICP. Los metales analizados fueron: Aluminio, Arsénico, Cadmio, Cobre, Cromo, Hierro, Níquel, Plata, Plomo, Selenio, Vanadio y Zinc. Las poblaciones estudiadas fueron: las playas de Ponce y Guayanilla y el río de Guayanilla (control). Para el análisis de datos se utilizó la prueba de Análisis de Varianza (ANOVA). El análisis estadístico mensual determinó que en la mayoría de los metales estudiados (Al, Fe, Ni y Zn) hubo diferencia estadística significativa en las playas de Ponce y Guayanilla con el grupo control. La comparación que se hizo entre ambas playas, demostró diferencia estadística significativa. El análisis anual arrojó una diferencia estadística significativa entre los siguientes metales: Cadmio y Níquel. El resultado de la investigación nos demostró que las concentraciones obtenidas no representan una amenaza en estos lugares de acuerdo a una comparación de estándares para aguas superficiales establecidos por la EPA. Futuras recomendaciones para este campo son: analizar las muestras por periodos mayores de tiempo, y así, darle seguimiento a los cambios en las concentraciones de estos metales.
Burgos-Robles, Anthony* Pontifical Catholic University of Puerto Rico, Dept of Chemistry; Waxler, David Psychology, Rutgers University Otto, Tim PhD Psychology, Rutgers University
Rats’ Perception of Olfactory Contextual Fear Cohnditioning
The main focus of our research is to explore the ways in which olfactory contextual information is acquired and stored in the brain. Brain areas participating in the detection and analysis of olfactory information are intimately connected with several areas known to play a prominent role in learning about the context, including the hippocampus (HPC). Further more, previous studies have demonstrated that dorsal hippocampal lesions attenuate olfactory contextual fear expression in rats. Thus, our research involves an electrophysiological examination of the CA1 nucleus (HPC subdivision) in the rat brain to observe its contributions to olfactory contextual learning. Single-unit recording technique allows the assessment of the response properties of individual hippocampal neurons during an olfactory contextual fear conditioning paradigm. In this behavioral model, animals were exposed to two olfactory contexts during a single conditioning session. Each context was presented four times a session in an alternating fashion. In the presence of strawberry extract (context A) animals received 3 presentations of a pure tone (2.7kHz, 20s) (conditioned stimulus, CS). In the presence of 15% pyridine (context B) animals received 3 CSs which co-terminated with a short electrical foot shock. (0.4mA, 0.5s). After several trails, rats exhibited a significant attenuation of freezing (fear response) to context A but not to context B. Therefore, olfactory information serves to set the occasion for fear conditioning after the rats acquired the significance of each context. However, the electrophysiological data suggest that CA1 nucleus does not perceive changes in olfactory context as changes in spatial location.
Diaz, Maldonado, Naomi*UPR-Mayagüez, Department of Chemistry; Zullo, Alfred, Purdue University, Williams, Kristi, Purdue University, Taparowsky, Elizabeth, Purdue University
Cloning of the mouse BATF gene to produce a "knockout" (null mouse)
The BATF protein belongs to the AP-1 family of basic leucine zipper trasncription factors. The leucine zipper allows members of the AP-1 family to dimerize and the basic domain allows the dimer to interact with DNA. The most popular members of the AP-1 family are Jun and Fos. The heterodimer (AP-1) formed by Jun and Fos proteins lead to the activation of transcription. BATF is unique because it can bind to DNA and reduce transcription of target gen es. This is an important charasteristic of BATF because thDNA sequences that AP-1 binds are in the promoter region of genes involved in regulation of many genes including cell proliferation.
The goal of this project is to generate a "knockout" mouse in which we could examine the phenotype of mice laking of BATF. This would allow us to confirm previous modes of BATF function and inferne w functions of this unique transcription factor. In order to produce a "knockout" we must first construct a targeting vector.
My project has focused on cloning pieces of the mouse BATF to produce the targeting vector. Once we get the targeting vector it is going to be injected into ES cells of mice in order to produce a BATF null mou se.
Rodríguez, Sol* Pontifical Catholic University of Puerto Rico, Dept of Chemistry,
Role of P53 Gene Polymorphisms in the Genetics of Endometriosis
Many women suffer inflammation and severe pain in the abdominal area during the menstrual cycle, and some of them do not know that these symptoms can be endometriosis. Endometriosis is a gynecologic condition defined as the presence of endometrial tissue in the peritoneum, ovaries, and other organs. This disease can only be diagnosed by surgical intervention and treatments are limited. For these reasons more studies are necessary to better understand this disease. Endometriosis might be caused by an interaction between multiple genes as well as environmental factors and it is considered a polygenic and multifactorial disease. We hypothesize that endometriosis has a strong genetic component in our population and propose to study the role of p53 gene polymorphisms in the etiology of endometriosis. p53 is a tumor suppressor gene which has been associated with various types of cancer, and also with endometriosis in an Asiatic population. We conducted mutation analysis of p53 in genomic DNA from patients and controls. Mutations were detected by PCR amplification using specific primers and analysis of the polymorphisms by agarose gel electrophoresis. The study populations were: sporadic cases (n=34), familiar history cases (n=54), female controls (20), and male controls (19). In our series, we observed that p53 Arg homozygosity (Arg/Arg) is not related to a lower risk for endometriosis, in contrast with what was observed in a Chinese population. We found that there is no relationship between polymorphisms in codon 72 of the p53 gene and endometriosis in the Puerto Rican population. This discrepancy may due to ethnic differences. In conclusion, our study suggests that the p53 codon 72 polymorphism can not be used as a marker to predict endometriosis development in all populations.
Román Hernández, Giselle*UPR-Mayagüez, Chemical Engineering; Seiglie, Vanesa, Chemistry, UPR-Mayagüez, Sanoguet Zuleika, Chemistry, UPR-Mayaguez, Pastrana-Rios, Belinda Chemistry, UPR-Mayaguez
Large Scale Expression and Purification of Recombinant Isotope Edited CCEN
Centrin is a low molecular mass protein (20 kDa) that belongs to the EF-hand superfamily of calcium-binded proteins.This protein is associated with MTOC and flagellar roots in Chlamydomonas reinhartii, a green algae in which one of the first proteins of this class were discovered. As a conserved component of MTOCs in divergent species, centrin is a potential novel target for the development of new therapeutic approaches that influence critical functions of microtubules. Current efforts are directed towards understanding the structure-function relationship of this protein and its interaction with target peptides. To accomplish this goal large quantities of pure recombinant protein are required(1). Fermentor based bacterial expression using 2XYT and 13C enriched minimal media have been carried-out to obtain sufficient quantities of the desired protein for subsequent isolation and purification following the method described in Pastrana-Ríos et al.(2).
Antongiorgi, Kevin; Delgado-Morales, Wilfredo; Rodriguez, Jose F.*, Department of Biochemistry/ Medical Sciences Campus
Variations of nelfinavir plasma concentrations in HIV-HCV co-infected patients
The human immunodeficiency virus (HIV) is one of the most concerned epidemics in the world, and a current threat in our society. In Puerto Rico, approximately 50% of the patients infected with HIV are co-infected with Hepatitis C (HCV). Liver disease is the most common reason of death in this patient population. The treatment for HIV consists of a cocktail containing two or more medications from the following divisions: Nucleoside Analogue Reverse Transcriptase Inhibitors (NRTI), Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTI) and Protease Inhibitors (PI). The current treatment for HCV is a combination of Peg-Intron plus ribavirin. The objective of this study was to determine differences in PI plasma concentrations in HIV-HCV co-infected patients before and after HCV treatment. We validated an HPLC method for the determination of nelfinavir (the protease inhibitor used in the study) and measured plasma concentrations in the patient population. A twelve hour (12 h) pharmacokinetic study was performed at week 0 (no HCV treatment) and at week R12 (12 weeks after HCV treatment). A control group of HIV infected patients was used to determine intra-and inter- patient variability. Pharmacokinetic parameters such as area under the curve (AUC) and trough concentrations (Cmin) will be presented. A detailed description of the validation process will be also discussed.
Acknowledgments: This work was partially funded by the following NIH grants: RCMI G12RR03051; CRC RCMI IP20RR11126; R01 AI14941; RISE Program GM61838-03; ACTU AI34832-11.
Feliciano, Ileana; Rodríguez, José F. *, Deparment of Biochemistry/ School of Medicine Medical Sciences Campus; Meléndez, Margarita; Rosario, Osvaldo *, Department of Chemistry University of Puerto Rico, Río Piedras Campus
Therapeutic drug monitoring of zidovudine (AZT-TP) and lamovudine (3TC-TP) in HIV-HCV co-infected patients using HPLC tandem MS
Zidovudine (AZT) and Lamovudine (3TC), both nucleoside reverse transcriptase inhibitors (NRTIs) are being used as a combination for the treatment of Human Inmunodeficiency Virus (HIV). The active form of these compounds are the triphosphated metabolites (AZT-TP and 3TC-TP), which are metabolized in the host cells. In order to realize pharmacokinetic studies of these drugs, it is needed to use an analytical methodology with high sensitivity and specifity. HPLC tandem MS is the most powerful methodology for the Therapeutic Drug Monitoring (TDM) of these drugs in complicated matrix (plasma) allowing low limits of detections (2ng/mL). The objective of this study is determine the differences of intracellular AZT-TP and 3TC-TP in HIV-HCV co-infected patients before and after HCV treatment using HPLC tandem MS. In Puerto Rico, approximately 50% of the patients infected with HIV are co-infected with Hepatitis C (HCV). For the pharmacokinetic study, patient samples were collected in a 12 week period since the beginning of HCV treatment. After collection, the samples are submitted to a series of process including anion exchange Solid Phase Extraction (SPE) prior to the HPLC tandem MS analysis.