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Acevedo Acevedo, Delgado; Leon-Velasquez, Madeline; Cortes-Figueroa, Jose E. Department of Chemistry, UPR-Mayagüez.
A biphasic displacement of 1,10-phenanthroline from fac-(dihapto-phenanthroline) (dihapto-[60]fullerene) tricarbonylmolybdenum(0) by triphenylphosphine
Triphenylphosphine displaces 1,10-phenanthroline from fac-(dihapto-phenanthroline)(dihapto-[60]fullerene)tricarbonylmolybdenum(0). The reaction was studied under flooding conditions where the molar concentration of triphenylphosphine was at least 10,000 times the molar concentration of fac-(dihapto-phenanthroline)(dihapto-[60]fullerene)tricarbonylmolybdenum(0). The reactions' progress were followed by measuring the absorbance at 440 nm. Plots of absorbance - absorbance infinity vs. time showed a biphasic behavior. This observation suggest that [60]fullerene is a cis labilizing ligand. The mathematical description to resolve the biphasic plot into two consecutive first order reactions will presented in detail. Acknowledgments are made to the Petroleum Research Fund (PRF 36623-B3), Administered by the American Chemical Society, to National Science Foundation (CHEM-0102167) for support of this work. DAA received financial support from PR-LSAMP.
Aviles, Yadriel; Alejandro Blanco; Samuel P. Hernández-Rivera. Center for Chemical Sensors Development for Explosives, Department of Chemistry. University of Puerto Rico. Mayagüez.
Investigación espectroscópica de 2,4-DNT y 2,6-DNT y sus interacciones con particulas de silica
A través de los años, como parte de conflictos bélicos, los dispositivos explosivos más se utilizados son minas terrestres. Las mismas son cargas explosivas que se colocan bajo suelo y luego se detonan por contacto. Existen miles de minas enterradas distribuidas atraves de 70 países en todo el mundo. Hasta hace poco tiempo era factible utilizar detectores de metales para detectar este tipo de artefactos explosivos. Hoy en día las minas se colocan en envases de plástico. Otro problema es que la técnica es incapaz de detectar pequeñas cantidades de cristales de explosivos. La Espectroscopia de Raman es una herramienta establecida para análisis de espectroscopia vibracional. La interacción de explosivos con diferentes substratos puede ser estudiada de información del desplazamiento cuantitativo de señales vibracionales Raman asociada con dicha interacción. Se hizo un estudio de espectroscopia vibracional para cristales de 2,4-DNT y 2,6-DNT. Para esto se utilizó un microscopio de Raman equipado con una línea de excitación láser de 514 nm. Las muestras se recristalizaron en diferentes solventes (agua, metanol y acetonitrilo) y luego se expusieron a la interacción con sílice. La interacción con silica gel dopadas con compuestos nitroaromáticos mostraron un desplazamiento significativo en las señales de los espectros. Esta información se utilizó para detectar DNT en muestras de silica usando Microscopia de Raman. También se midió la variación del desplazamiento de la señal Raman a diferentes valores de pH (4, 7 y 9). Estos resultados pueden servir de base para desarrollar nuevos sensores para detección de materiales explosivos.
Benítez, Jaime; Marrero, Jeffrey; Rodríguez, Abimael D. Department of Chemistry, University of Puerto Rico, Río Piedras.
Isolation and structural elucidation of two highly oxygenated cembranoids diterpenoids from the Sea Plume Pseudopterogorgia kallos
The chemical study of the chloroform extract from the Colombian Sea Plume Pseudopterogorgia kallos resulted in the isolation of two new highly oxygenated cembranoids diterpenes, bipinnatin K (1) and L (2). Their chemical structures were elucidated using 1D- and 2D NMR experiments (HMQC, 1H-1H COSY, HMBC, and NOESY) in combination of UV, IR, and HR-MS analysis. The biological activity of the forementioned compounds are currently under study.
Borrero, Solmarie; Santiago, Mitk'El; Guadalupe, Ana R.; Colón, Jorge L. Chemistry Department, University of Puerto Rico, Rio Piedras.
Synthesis, characterization and intercalation of [Co(tpy)2](PF6)2 into the 10.3 Å phase of layered zirconium phosphate
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 inorganic complexes using a 10.3 Å phase of ZrP, which we have recently demonstrated directly exchanges large metal complexes. The inorganic complex chosen for our studies is [Co(tpy)2](PF6)2, an electron mediator suitable for biosensor applications. The synthesis of the 10.3 Å ZrP phase, [Co(tpy)2](PF6)2, and were successful and all materials were characterized. The characterization was done using X-Ray Powder Diffraction, Infrared Spectroscopy, and UV-visible spectrophotometry. Carbon paste electrodes were modified with [Co(tpy)2]2+-exchanged ZrP. The electrochemical characterization of this material will also be presented. S.B.M. acknowledges the financial support of the PR-LSAMP program. M.B.S. acknowledges the financial support of NIH-RISE/SUBE Graduate Fellowship.
Burgos-Frontanes, Samuel; Leonardo Pacheco Londoño; Oliva M. Primera Pedrozo; Samuel P. Hernandez Rivera. Centro de Desarrollo de Sensores Químicos para la Detección de Explosivos, Departamento de Quimica, University of Puerto Rico-Mayagüez.
Estudio de fases de RDX a diferentes concentraciones de cristalización en superficies
Existen cuatro confórmeros de RDX, en fase gaseosa. En sólida solo se han descubierto dos de estos confórmeros, los cuales producen dos fases estables: RDX- y RDX-. Cuando se tiene RDX en solución y se deposita en una superficie este forma una de las dos fases. La forma en la cual condense depende de la superficie, de la concentración, de la cantidad depositada y del solvente. En este trabajo se variaron estos cuatro parámetros, encontrando que la concentración y la cantidad depositada eran los factores más influyentes en la cristalización. Para una superficie como acero inoxidable no-magnético tipo 316 se encontró que depositando 20 µL a una concentración mayor de 200 ppm de RDX en acetonitrilo se produce RDX- y a concentraciones RDX- es más estable y se produce en forma prominente, aunque no exclusivamente. La verificación de las fases se hizo mediante Microscopia Raman, FT-IR y FT-IR acoplado a fibra óptica con sonda de Angulo de rozamiento.
Campbell, Muriel; Sanoguet Zuleika. Chemistry Department, UPR-Mayagüez – Hu, Haitao; Chazin, Walter. Center for Structural Biology, Vanderbilt University – Pastrana, Belinda. Chemistry Department, UPR-Mayagüez.
Characterization of phosphorylated Chlamydomonas centrin
Centrin, a 20 kD protein, is a member of the calmodulin superfamily of EF-hand calcium binding proteins. It plays an essential role is centrosome duplication by mediating chromosome segregation during mitosis. Centrin was originally cloned at the DNA level from the unicellular green algae Chlamydomonas reinhardtii. Since then, homologs of centrin have been identified in yeast, mice, and humans, among other species. Centrin has two structurally independent domains connected by a flexible linker. The C- terminal domain of centrin (CRC-C) has a PKA phosphorylation site at serine 167. In vitro phosphorylation was performed on both, full length centrin and CRC-C, in order to analyze the effects of phosphorylation on the protein’s conformation. Differential Scanning Microcalorimetry was performed on both samples. The results suggest that phosphorylated centrin adopts a slightly different conformation and is less stable than the unphosphorylated form of centrin.
Cardona, Rocío del A.; Muñoz, Lisa; Guadalupe, Ana R. Department of Chemistry, University of Puerto Rico, Río Piedras Campus.
Development of a DNA sensor using peptide nucleic acid (PNA) as a probe attached to polystyrene films
The need for fast detection of harmful bacteria and other pathogens has lead the scientific community to study new sensor probes and devices. Peptide Nucleic Acid (PNA), a DNA synthetic analog, is a new tool in nucleic acid research. This molecule posses many of DNA properties but also present promising features because of its capacity to form more rigid structures, better hybridization and to detect bases mismatches. Due to its properties PNA has been used as a probe in the construction of DNA biosensors. Thin films of polystyrene functionalized with succinimide were prepared over gold substrates. PNA chains modified with amino groups were immobilized in the polymer surface. The complementary DNA sequence for PNA was labeled with a ferrocene complex. The hybridization was monitored by the redox process of ferrocene using Osteryoung Square Wave Voltammetry (OSWV). Atomic Force Microscopy (AFM) and X-Ray Photoelectron Spectroscopy (XPS) were used to determine morphology changes after immobilization and hybridization. The electrochemical studies showed that the response time for double strand formation were around 60 min. Using AFM and XPS the formation of the double strand was also confirmed after changes in surface morphology and elemental analysis, respectively. To complete the development of our DNA/PNA sensor a calibration curve will be construct to evaluate the usable concentration range and the sensor analytical parameters.
Caro-Gautier, Humberto. Institute for Tropical Ecosystem Studies, University of Puerto Rico Rio Piedras and Department of Chemistry, University of Puerto Rico Rio Piedras - J. Lugo Vega; R. Ríos Dávila. Graduate School of Public Health, Department of Environmental Health, Medical Sciences Campus, University of Puerto Rico, San Juan - Mayol-Bracero, O.L. Institute for Tropical Ecosystem Studies, University of Puerto Rico Rio Piedras and Department of Chemistry, University of Puerto Rico Rio Piedras.
Deposition of carbonaceous aerosol particles on the historical building “Ruinas de Caparra” in Puerto Rico
Atmospheric aerosols are collections of small particles suspended in the air originating from natural and anthropogenic sources. Carbonaceous aerosol particles (CAs), mainly composed of elemental and organic carbon (EC and OC), damage monuments and historical building around the world. These particles have been found in the inner surface of stone and mortars of historical buildings (mostly in Europe), generating the degradation of these materials by means of such chemicals reactions as the sulphatation of calcium carbonate into gypsum. The purpose of this study is to investigate the relationship between the soiling produced by carbonaceous aerosol particles and the formation of the black patina on the surface layers of “Ruinas de Caparra”. Samples of the patinas were collected at several points from the upper and side surfaces of the ruins. Analyses of these samples were performed according to the procedure developed by Ghedini et al., 2000. Scanning electron microscope (SEM) with energy dispersive spectrometry was used for the study of the morphology and elemental composition of the particles deposited on the surface of the collected samples. The determination of water-soluble ions (SO3-2, SO4-2, NO3-), was performed using ion chromatography. Parallel to these analyses, air sampling with a low-pressure impactor was also performed for the determination of the size resolved EC and OC concentrations to which the ruins are exposed on a daily basis. Preliminary results of this study will be discussed in this presentation.
Cartagena, Michelle; Reyes, Elba D. Chemistry Department, University of Puerto Rico, Cayey Campus.
Creating methodology to determine chemical changes of infusions
In Puerto Rico, infusions of plants with therapeutic effects are very useful but sometimes dangerous for the health. For many plants used to treat different illnesses, no phytochemical information are reported, therefore, nobody knows of possible secondary effects or side reactions that will happen due to changes in pH or side reactions with other synthetic drugs. The main goal of this research is to study the chemical changes of the plant compounds that have therapeutic effects (metabolites), which are namely ingested by humans. In particular, we want to answer the following questions: 1) Do the compounds present in an active extract suffer chemical changes at different pHs and temperatures? 2) Are all the organic compounds present or extracted from one source present in the infusions prepared by the population? We expect to: a) probe qualitatively if the general organic composition at specific infusions suffers chemical changes with lower or neutral pH’s; b) compare the total chemical compositions of the whole crude MeOH extracts of Citrus aurantium L. and Annona reticulata leaves with the extracted chemical composition in the aqueous phase when the infusions are prepared, and c) characterize the crude extracts presenting chemical changes. Preliminary TLC results, analyzing infusion extracts from leaves of Citrus aurantium L. and Annona reticulata (after mimicking human digestion, specifically stomach and plasma pH and corporal temperature) reveals irreversible chemical changes when the pH rises to 7.4. These preliminary results demonstrate that chemical changes could be occurring during the bioassays implicating that biological activity could be due to the chemical changes promoted by the extracts instead of natural metabolites. Extracts presenting chemical changes are submitted to Probit analyses, using brine shrimp as live source to probe citotoxicity. ED50 values and partially characterization of organic compounds using chromatographic (TLC, CC, GC) and spectroscopic techniques (IR, MS) will be presented.
Castillo Rivera, Dorianne A; Rodriguez Reyes, David; Prieto, Jose A. Chemistry Department, UPR-Rio Piedras.
Studies toward the synthesis of Rifamycin S ansa chain
Rifamycin S is a member of the ansamycin family of antibiotics. Its structure consists of an aliphatic ansa chain with eight consecutives stereogenic centers and an aromatic portion. In order to construct the polypropionate array, we are currently working in a reiterative approach that consists in the stereoselective synthesis of epoxides, followed by a regioselective cleavage process with an organometallic compounds. Following the proposed work, we epoxidized Ethyl trans crotonate with 3-chloroperoxybenzoic acid (mCPBA) in moderate yield. This epoxide was cleaved with diethylpropynylalane in high yield (80%) and the alkynyl ester was transformed into its corresponding alkynyl acid in quantitative yield using microwave technology. Then, a trans reduction of the alkyne functionality was performed in very high yield under sodium/ammonia conditions (95-100%). Iodolactonization followed by methanolysis produced a second epoxy ester (56%). Since the cleavage of this epoxide showed to be problematic , we are working in the reduction of the ester functionality and protection of the resulting primary alcohol before exposing the epoxide to the cleavage process. At this stage, we have synthesized six of the stereogenic centers of Rifamycin S. Currently, we are investigating the best reaction conditions to finally incorporate the remaining two stereogenic centers of the ansa chain. Work supported by NIH RISE (R25-GM-061151) and NIH SCORE (S06GM-08102).
Cotto, Marlene; Miranda, Carlos.; Carballeira, Néstor M. Department of Chemistry, University of Puerto Rico, Rio Piedras.
The total synthesis of (+)-2- methyldecanoic acid, a potential antimycobacterial fatty acid
Biologically active compounds containing methyl branching are abundant in nature. The fatty acid (+)-2-methyldecanoic acid was synthesized in three steps starting from commercially available decanoic acid. This synthesis provided sufficient quantities for biological evaluation against Mycobacterium tuberculosis H37Rv. The previously synthesized 2-methoxydecanoic acid has demonstrated activity (99% inhibition) at 6.25 µg/mL against this strain of M. tuberculosis and such studies are underway.
M.Cotto thanks the UPR-RP RISE program for an undergraduated fellowship
Crespo-Román, Gisela; Ocasio-Delgado, Yessenia; Cortes-Figueroa, Jose E. Department of Chemistry, UPR-Mayagüez.
Mechanisms of ligand exchange reactions on (dihapto-[C60]fullerene) transition-metal carbonyl complexes
The Lewis bases (L) piperidine, triphenylphosphie, and triciclohylphosphine displace bidentate ligands (bidentate ligands = 1,2-bis(diphenylphosphino)ethane (dppe) and 1, 10-phenanthroline (phen)) from fac- and mer-(dihapto-C60)(dihapto-bidentate ligand)M(CO)3 to produce fac- and/or mer- (dihapto)(monohapto-L)2M(CO)3 and (monohapto-L)(dihapto-bidentate ligand)M(CO)3 (M = Cr, Mo, W). The reactions are first order with respect to the molar concentration of (dihapto-C60)(dihapto-bidentate ligand)M(CO)3. The order with respect to L is complex. The proposed mechanisms involve a competition between a L-assisted ring-opening of the chelate ring to produce the electronically-saturated intermediate (dihapto-C60)(monohapto-L)(monohapto-bidentate ligand)M(CO)3, solvent-assisted ring-opening of the chelate ring to produce the electronically-saturated intermediate (dihapto-C60)(solvent)(monohapto-bidentate ligand)M(CO)3 and a solvent-assisted dissociation of C60 producing the electronically-saturated species (monohapto-L)(dihapto-bidentate ligand)M(CO)3. These mechanisms differ from previously proposed mechanisms for the ligand exchange reactions of closely-related complexes such as fac-(monohapto-L)(dihapto-dppe)M(CO)3 (L = CO, piperidine, pyridine) and is contrary to the known cis labilizing property of dppe. These results suggest that [C60]fullerene has a strong steric influence on the inorganic moiety of the complex and on its chemical behavior. Acknowledgments are made to the Petroleum Research Fund (PRF 36623-B3), Administered by the American Chemical Society, and to National Science Foundation (CHEM-0102167) for support of this work.
Cruz, Nadya; Nieves, Ileana; Oyola, Rolando; García, Carmelo; Piñero, Luis; Rivera, Jessica; Department of Chemistry, UPR-Humacao.
Imipramines tricyclic drugs: An electrochemistry study in different solvents
The tricyclic anti-depressive drugs Imipramine (IPA), Desimipramine (DIPA) and Cloimipramine (CIPA) are of significant pharmaceutical importance because of their neuroleptic, sedative and antihistamic effects. Because these drugs are susceptible to changes in their molecular structures, the redox potentials of these drugs are relevant to understand their photoelectron transfer mechanism involving short-lived oxidation-reduction intermediates. The oxidation-reduction capability of a given derivative have been investigated in different solvents by Cyclic and Differential Pulse Voltammetry (CV and DPV, respectively) with a BAS CV-50 Voltammetric Analyzer controlled by the CV-50W version 2.3 software installed in a Pentium II computer. Results have shown that DIPA and IPA are easily oxidized compared to CIPA in the solvents used. As expected, the behavior of CIPA can be attributed to the chlorine induced electron withdrawing effect. In addition, CIPA shows the formation of two distinct oxidation intermediates when IPA/CIPA or DIPA/CIPA drug concentration ratio is changed in acetonitrile and methanol. Although the intermediates have not been characterized in these studies, the CV and DPV results may be correlated with the photochemical and photophysical response of these drugs related to the side effects. The gathered results are relevant for new drug development of efficient formulation with fewer side effects for the proper treatment of patients. Sponsored by Advance, NSF (SBE-0123645), UPR-Humacao
Cruz Moreira, Solimar; Ramos, Maiella, Department of Physics-Chemistry, University of Puerto Rico in Arecibo - Arbelo, José; Pantoja, Carlos; Mercado, Benjamín. Department of Biology, University of Puerto Rico in Arecibo.
Bioremediation of contaminated water with lead using Tropical plants in hydroponics cultures
Phytoremediation is a process of using plants to remove contaminants from the environment. The water hyacinth (Eichhornia crassipes) may be used as a sensitive bioindicator for continuously monitoring trace quantities of toxic heavy metals in aquatic systems. In this work we addressed the uptake of lead (Pb) by the water hyacinth aquatic plant. Hyacinth plants were grown in hydroponic solutions containing different concentrations of lead ranging from 0 ppm Pb to 10 ppm Pb. Levels of lead were determined in plant samples by means of an atomic absorption flame spectrometer. It was demonstrated that E. crassipes has a strong capability to accumulate higher lead concentrations in its roots than in its other parts. It was found that the concentrations of lead in the water hyacinth were higher than in the water. This heavy metal accumulated in the root tissues of water hyacinth may serve as a chemical marker for the evaluation of the remediation capabilities of this aquatic plant.
Delgado,
Dana; Nuñez, Daliangelis; Torres, Ivelisse; Rosario, Osvaldo.
Chemistry Department, UPR-Rio Piedras.
Isolation
and characterization of marine humic substances from seawater
Díaz,
Tanya; Malavé, María; Rivera, Mirna; Castillo, Jorge; Tremont,
Rolando. Department of Chemistry, UPR-Humacao.
Self-assembled
C26H24O2Fc on gold surface in ethanol solution
Gold
surface have been modified by self-assembled techniques. Controlling the
adsorption time of C26H24O2Fc at gold surface. This study was followed by
cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and
X-ray photoelectron spectroscopy (XPS) analysis. The method used for the
surface modification was the control of exposure time of gold surface in
the modifier/ethanol solution. By CV and EIS we demonstrated that the gold
surface was modified with C26H24O2Fc compound, avoiding the electron
transference in the interface. In the study by XPS we observed that the
organometallic molecule indeed has been adsorbed on the gold surface. In
addition, it was observed that the molecule-gold interaction is through
electrons of cyclopentadienyl, where the oxygen atoms are near the
air-molecule interface.
Domenech
Garcia, Maribella. Biotecnologia Industrial, UPR-Mayagüez
- McFallin, Jose Luis. Ingenieria Quimica, UPR-Mayagüez -
Velez, Gisselle. Quimica, UPR-Mayagüez - Justicia, Shandra.
Biotecnologia Industrial, UPR-Mayagüez - Rodriguez, Kristy;
Rodriguez, Lolita. Quimica, UPR-Mayagüez.
Effects
of aqueous extracts of baquiña in free calcium ion levels determined with
a calcium selective electrode
Para
identificar este posible principo activo hemos procedido a analizar los
constituyentes hidrosolubles presentes en las hojas de Baquiña. El
proceso de análisis de la planta, una vez las muestras se han secado (liofilización)
y molido (2 mm) ha consistido en realizar una extracción Soxhlet con agua
(5-10 gramos de material seco en 150 mL de agua), fraccionación por
filtración gel (Sephadex G-10 y G-25 fino y superfino) y estudio de las
fracciones resultantes por cromatografia líquida (HPLC, Alltima C18
5um, 27:73 acetonitrilo – agua). Resultados preliminares indican que hay
varias fracciones puras, llamándonos la atención un pico con tiempo de
retención de 4 minutos.
Echevarría
Torres, David; Santos, Lizette. Chemistry, PUCPR.
The effect of anticonvulsants on the microsomal cytochrome P450 monooxygenase system
The
liver is one of the most important organs involved in the metabolism of
exogenous and endogenous compounds in the body. The microsomal cytochrome
P450 monooxygenase system is present in the liver. This system play a
mayor role in the biotransformation of many compounds. The objective of
this study is to measure the effect of some anticonvulsants drugs on the
cytochrome P450 system. The anticonvulsants drugs to be studied are:
Tegretol (carbamazepine), Divalproex (depakote), Trilepal (oxcarbazepine)
and Dilantin (phenytoin). The isoenzymes that will be studied are CYP2C8
and CYP2C9. Microsomes will be prepare from Cricetulus griseus cells (CHO)
cells and treated with the anticonvulsants drugs. Enzyme activities will
be measured using HPLC Technique. Expected results will include the
determination of possible effects on the CYP2C8 and CYP2C9 isoenzymes.
Escalona,
Yma; Miller, Andrés. Natural Sciences Department, Inter American
University, Bayamón Campus.
Determinación
de concentración de plomo en árboles frutales silvestres, en la Isla de
Vieques
Flores,
Rosangelly; Brito, Rosa; Hernandez, Jessica; Cabrera, Carlos R.
Department of Chemistry, University of Puerto Rico-Rio Piedras.
DNA
density measurements using electrochemical methods on modified platinum
electrodes
García,
Rafael; Samuel P. Hernández-Rivera. Center for Chemical
Sensors Development for Explosives, Department of Chemistry,
Vibrational
spectroscopy and theoretical studies of transparent explosives
Explosives
are a special group of chemicals that have a high energy in their chemical
bonds that are able to release it in a short time in the form of hot
gases. In today’s modern world, explosives are important and
useful tools that play central roles in such as mining of mineral ores and
construction. In the political scene, explosives has been give a
more sinister and morbid use in terrorism. In the past the kind of
explosives that were used for terrorist application where somewhat common
and easily acquired in the international weapons underground market: black
powder, T.N.T, RDX and other military explosives. But these
explosives have an Aquiles heal, they can be detected in very small
quantities by the instruments (Ion Mobility Spectrometers) that the
transportation security agencies use. Being a very adaptable entity
terrorist, are now using exotic home-made explosives like Triacetone
Triperoxe (T.A.T.P) and Diacetone Diperoxe (D.A.T.P) that are virtually
invisible to current the technology used in these detection machines.
Our research centers in the analysis of this kind of chemical explosives:
Transparent Explosives and in the design of sensors for their detection.
In the initial experiments we combined different methodologies for
characterization and analysis. We used Spontaneous Raman
spectroscopy for vibrational characterization. Then the research
centered about to the use of silver colloids for applications of Surface
Enhanced Raman Spectroscopy. For target compounds we used model compounds
with similar characteristics with the transparent explosives. These
compounds are easier to use and have low toxicity.
García
Berríos, Edgardo; Elba Reyes; Raúl J. Castro. Department
of Chemistry,
In-situ
Friedel-Craft acylation of benzenethiol/Au self-assembled monolayers
Gavalda,
Salvador; Rodriguez, Jose; Smotkin, Eugene. Chemistry, UPR-Río
Piedras.
Preparation
and characterization of Cu/Zn/Al2O3 catalyst libraries for design of
experiments (DOE) development of water-gas-shift and/or methanol reforming
catalysts
Giménez,
Lizabeth; Sanabria, David; Cruz, Clarisa; Carballeira, Néstor.
Department of Chemistry,
The
synthesis of new fatty acids and their potential as antifungal compounds
Gonzalez,
Cristian. Chemical Engineering, UPR-Mayagüez -
Rivera, Luis A. Chemistry, UPR-Mayagüez.
Design,
synthesis, and characterization of potential biosensors for protein by
covalent immobilization of the amino acid threonine
Gonzalez
Freire, Carol L. Quimica, Universidad de Puerto Rico Recinto
de Rio Piedras - Quesada Gonzalez, Orestes. Estudios
Generales, Universidad de Puerto Rico Recinto de Rio Piedras -
Morales Guardia, Reginald. Quimica, Universidad de Puerto Rico Recinto de
Rio Piedras.
Possible
site of interaction of sanguinarine chloride and ipratropium
bromide on the human erythrocyte membrane
Gonzalez-Gonzalez,
Ileana; Tryk, Donald A.; Cabrera, Carlos R. Chemistry Department,
University of Puerto Rico, Rio Piedras Campus.
A
comparison of sulfur-doped and boron-doped diamond films as
electrocatalyst supports
Granell,
Laura; Pietri, Ruth; Lewis, Ariel; López-Garriga, Juan.
Chemistry, U.P.R.-Mayagüez Campus.
Determination
of the open and closed conformations of the hemoglobin II from Lucina
pectinata by FT-IR
Guillen,
Nancy; Narvaez, Daniel; Camacho, Carlos; Pastrana, Belinda.
Industrial Biotechnology, Chemistry Department, UPR-Mayagüez.
FT-IR
studies of EGFR ligands
Hernandez,
Emil; Castro, Miguel E. Chemistry, UPR-Mayagüez.
Nanoparticle
synthesis in a bubble: microreactors for selective nanoparticle synthesis
Hernández
Lugo, Dionne M.; García, Carmelo; Piñero, Luis E.; Oyola,
Rolando. Departamento de Química, Universidad de Puerto Rico
en Humacao.
Photophysical
properties of protriptyline and dibenzocycloheptene
Protriptyline
hydrochloride (PTL-HCl) is a tricyclic antidepressant and a skin
photosensitizing agent in humans. The mechanism of this cutaneous
photosensitivity is still unknown. It has been proposed that the
excited states and some of the short-lived intermediates of this drug are
directly associated with its in vivo phototoxic effects. Therefore
we have measured the photophysical properties of the protonated (PTL-HCl)
and unprotonated (PTL) forms of protriptyline and the parent molecule (dibenzocycloheptene,
DBCH). The ground and excited singlet state properties (molar extinction
coefficient, fluorescence quantum yield, fluorescence lifetime and
fluorescence quenching constant) were measured in methanol and
acetonitrile. The ground state properties are solvent and protonation
independent. The fluorescence quantum yield and lifetime, on the
other hand, strongly depend on the solvent. The quenching studies
were done in acetonitrile using diethyl and triethyl amine as quencher.
The Stern-Volmer quenching constants are also solvent dependent.
This work has been supported by NIH-MBRS Grant S06GM08216.
Justicia
Leon, Shandra D. Departamento de Biotecnologia Industrial,
UPR-Mayagüez - Souto Bachiller, Fernando; Rodriguez Rodriguez,
Lolita. Departamento de Quimica, UPR-Mayagüez -
Justicia Leon, Shandra D. Departamento de Biotecnologia Industrial,
UPR-Mayagüez - Velez Ruiz, Gisselle A.; Rodriguez Colon,
Kristy I. Departamento de Quimica, UPR-Mayagüez -
Domenech Garcia, Maribella. Departamento de Biotecnologia
Industrial, UPR-Mayagüez.
Fitoquimica de plantas medicinales diureticas: Rubia tinctorum
Rubia
tinctorum (R. tinctorum) es una
planta medicinal diurética utilizada tradicionalmente para tratar
calcificaciones, tales como la piedra del riñón, tracto urinario y
vejiga, compuestas fundamentalmente de oxalato y fosfato de calcio.
Existen múltiples testimonios de que las decocciones de esta planta
preparadas según el método tradicional (té), tienen la capacidad de
pulverizar dichas calcificaciones. Extracciones realizadas en el
laboratorio confirman que los extractos de R.
tinctorum son capaces de acomplejar sales de calcio solubles y
disolver las sales insolubles de oxalato y fosfato de calcio. El
acomplejamiento de calcio que presenta R.
tinctorum se le ha adjudicado preliminarmente a sus componentes
mayoritarios, alizarina, un pigmento anaranjado rojizo y purpurina,
amarillo. Un tercer componente lo es la lucidina, pigmento con alto grado
de toxicidad. El problema se fundamenta en que ninguno de los pigmentos
acomplejantes se encuentran en el extracto acuoso de la planta pues son
virtualmente insolubles en agua, por lo que se infiere la existencia de
otros componentes solubles. Candidatos posibles son los correspondientes
glicósidos solubles en solución acuosa. Para corroborar estas hipótesis,
actualmente se están realizando extracciones soxhlet con agua a partir de
las raíces de R. tinctorum,
fraccionación por ultracentrífuga o filtración gel de dichas
extracciones y, finalmente, estudios cromatográficos (HPLC) y
espectrofotométricos (UV-VIS) para determinar la composición y pureza de
fracciones recolectadas. La evidencia obtenida indica que hemos
aislado los glicósidos de alizarina y purpurina puros y que dichos glicósidos
muestran actividad antilítica determinada por el electrodo selectivo de
calcio. Además, no se puede decir que existen grandes cantidades del
componente tóxico, lucidina o sus glicósidos, en extractos de R.
tinctorum.
López
Pacheco, Lilibeth; Santos, Lizette. Chemistry,
El
efecto de un complejo multivitamínico en el sistema de citocromo P450
López-Alvarez,
Yania M. Industrial Biotechnology Program, UPR- Mayagüez
- López, Gustavo E. Department of Chemistry, UPR-Mayagüez.
Computational
studies of the liquid-liquid equilibrium in Lagmuir monolayers
Madero-Vergara,
Mayraliz; García Fraga, Oscar; Díaz-Vazquez, Liz; Rosario,
Osvaldo. Chemistry Department, UPR Río Piedras.
Effects
of extraction conditions and modifiers on the supercritical fluid
extraction of some persistent organic pollutants from sebum
Maldonado,
Omar D.; Castro, Raul. Quimica, U.P.R. Cayey.
Aplicaciones
de QCM y EQCM para el estudio de SAM’s
Phospholipase A2 competition in human erythrocyte studies using confocal microscopy
The
existence of different interactive sites in human erythrocyte was
confirmed by a series of binding studies that characterized the binding
isotherms of the basic phospholipase A2 (PLA2) from A. halys and one of
the PLA2 from N. nigricollis snake venom. The interaction of N.
nigricollis PLA2 is characterized by its Ca+2 requirement for binding and
had no acyl specificity in other hand, A. halys PLA does not require
calcium for binding, but does so for hydrolysis and its specificity is
dependent on enzyme concentration. These studies reveled that A.
halys interacted in a very limited number (5.2 x 107 per cells) of high
affinity sites. Competition studies demonstrated that at high levels (50
ug/mL cells) N. nigricollis PLA competed for the high affinity site of A.
halys PLA. Confocal Microscopy imaging of intact human erythrocyte
using A. halys and N. nigricollis PLA labeled with Alexa Fluor 488 and
Alexa Fluor 532 respectively confirm the binding studies and calcium
dependance. Flourescence profile of both PLA2 at concentration in
wich N. nigricollis displaced A. halys from its high affinity site were
obtained. (Supported by MARC Grant 5T34GM07821-24)
Martín,
Mariana; Rodríguez, David; Castillo, Dorianne; Prieto, José A.
Department of Chemistry,
A
new epoxide approach to polypropionate chains using trimethylalane
Mattei,
María de los A; Santos, Lizette. Chemistry Department,
Metal
content determination of the potable water at the Pontifical Catholic
University of Puerto Rico
Morales,
Eduardo M.; Ortiz, Margarita. Chemistry Deparment,
UPR-Humacao.
Synthesis of alpha silylated and alkylated O-tert-butyldimethyl silyl aromatic ketoximes
New
synthetic methods for the chemo and stereoselective synthesis of important
biologically active molecules are in grat demand. Reactions of metal
enolates and azaenolates are well-known methods for construction of C-Si
and C-C bonds. O-TBS ketoximes are novel precursors for the
synthesis of highly rective azaenolates, which can be alpha-C substituted.
We studied the alpha silylation and alkylation of O-TBS substituted
aromatic cyclic and acyclic ketoximes with LDA under several reactions
conditions. Complete conversion and high yields were afforded for
the silylation of O-TBS-4-metoxyacetophenone and indanone oximes with LDA
at -78 oC, using trimethyl chlorosilane as electrophiles. O-TBS-alpha-tetralone
and 6-methoxy substituted oximes derivate, were also prepared and their
silylation gave different substituted silylated products with expected
molecular weight. The alkylation of alpha tetralone with benzyl
bromide was obtain in good conversion, but the product is unstable.
Morales,
Victor M.; Morales, Angel L. Chemistry Department, UPR-Rio
Piedras - Van Keuls, Fred.
Chemisorption
and chemical characterization of monolayers at barium strontium titanate
Ba0.5Sr0.5tio3 (BSTO) for phase shifter applications
Nuñez, Daliangelis; Delgado, Dana; Torres, Ivel