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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.