|1993-1995||MIT Chemistry Department Postdoctoral Fellow with professor A. M. Klibanov.|
Ph. D. in Physical Organic Chemistry, Rutgers University. Supervisor. Prof. F. Jordan
Thesis title: Reaction of 2-Alkyl Thiazolium Salts at Their C2-Positions Relevant to Thiamin Enzymes; Electrochemistry and Acid-Base Properties.
|1985-1987||B.S. in Chemistry, SUNY at Old Westbury|
Bronx Community College.
1995-present University of Puerto Rico - Humacao College. Associate Professor, Department of Chemistry.
1993-1995 Massachusetts Institute of Technology NIH Postdoctoral Fellow with professor A. M. Klibanov. Investigation of the effect of solvents on the substrate enantioselectivity and the reaction kinetics of an enzyme (Mucor miehei lipase) catalyzed transesterification reactions between chiral alcohols and activated esters.
1988-1993 Rutgers University Graduate
assistant with professor F. Jordan, Department of Chemistry.
.The redox potentials of a series of 2-alkyl and 2-benzylthiazolium salts, structurally similar to the key enzyme-bound enamine intermediate in all thiamin diphosphate dependent enzymes, were determined using cyclic voltammetry in (Me)2SO. The number of electrons transferred during oxidation was determined.
.The products of controlled-potential electrolysis reactions of 2-alkylthiazolium salts were isolated and identified as a dimer formed by a free-radical reaction. A mechanism for the reaction was proposed. These findings are relevant to the enzymatic decarboxylation of pyruvic acid, by pyruvate-ferredoxin oxidoreductase.
.The kinetic properties, the pKa=s and the kinetic isotope effects of 2-benzylthiazolium salts in water were determined by stopped-flow, and a mechanism for this reaction was proposed.
S.U.N.Y. at Old
Westbury. Research assistant with professor R. Hoyte.
.Improvements in the synthesis of a steroid derivative.
1997-2000 Academic Research Enhancement
Award (grant # GM55896-01).
Grant Title: Improving the Use of Enzymes for Synthesis
1997-1999 Minority Biomedical Research
Support Program (grant # GM08216-14S1).
Grant Title: Improving the Use of Enzymes for The Synthesis of Biologically Active Compounds
1999-2003 Minority Biomedical Research
Support Program (grant # GM08216-14S1).
Grant Title: Study of the Solvent Dependence of Enzyme Enantioselectivity.
Gabriel Barletta, Alex C. Chung, Carlos B. Rios, Frank Jordan, and James M. Schlegel "Electrochemical Oxidation of Enamines Related to the Key Intermediate on Thiamin Diphosphate Dependent Enzymatic Pathways: Evidence for One Electron Oxidation via a Thiazolium Cation Radical". J. Am. Chem. Soc. 1990, 112, 8144-8149.
Jordan, F., Zeng, X.-P., Menon-Rudolph, S., Annan, N., Barletta, G., Chung, A.C. and Rios, C. B. "Observation and Properties of the 2-a-carbanion (enamine) Intermediate on Pyruvate Decarboxylase and in Chemical Models". Biochemistry and Physiology of Thiamin Diphosphate Enzymes. 1991, H. Bisswanger and J. Ullrich, Ed. VCH Publishers, pp 34-49.
Gabriel Barletta, W. Phillip Huskey, and Frank Jordan "Observation of a 2-a-Enamine from a 2-(Methoxyphenylmethyl)-3, 4-dimethylthiazolium Salt in Water: Implications for Catalysis by Thiamin Diphosphate-Dependent a-Keto Acid Decarboxylases". J. Am. Chem. Soc. 1992, 114, 7607-7608.
Gabriel L. Barletta and Frank Jordan, "Spectroscopic Observation of the Kinetic Fate of a Thiamin-Bound Enamine Intermediate in Water". Biochemistry 1992, 31, 2201
Yao-Tsung Chen, Gabriel Barletta, Khadijah Haghjoo, Jung Tsang Cheng and Frank Jordan, "Reactions of Benzaldehyde with Thiazolium Salts in Me2SO: Evidence for Initial Formation of 2-a-(Hydroxybenzyl)thiazolium by Nucleophilic Addition, and for Dramatic Solvent Effects on Benzoin Formation". Journal of Organic Chemistry 1994, 59, 7714-7722.
Hidetaka Noritomi, Orn Almarsson, Gabriel L. Barletta and Alexander M. Klibanov, "The Influence of The Mode of Enzyme Preparation on Enzymatic Enantioselectivity in Organic Solvents and Its Temperature Dependence". Biotechnol and Bioeng. 1996, 51, 95-99.
Chingfan C. Chiu, Alex Chung, Gabriel Barletta and Frank Jordan, "Intramolecular Model for the Reductive Acyl Transfer Catalyzed by a-Keto Acid Dehydrogenases". J. Am. Chem. Soc. 1996,118, 11026-11029.
Gabriel L. Barletta, Yu Zou, W. Phillip Huskey, and Frank Jordan, "Kinetics of C(2-a)-Proton Abstraction from 2-Benzylthiazolium Salts Leading to Enamines Relevant to Catalysis by Thiamin-dependent Enzymes". J. Am. Chem. Soc. 1997, 119, 2356-2362.
Kai Griebenow, Yanira Diaz Laureano, Angelica M. Santos, Ileana Montañez Clemente, Luiz Rodriguez, Michael W. Vidal, and Gabriel Barletta. "Improved Enzyme Activity and Enantioselectivity in Organic Solvents by Methyl –$-Cyclodextrin" J. Am. Chem. Soc. 1999, 121, 8157-8163.
Angelica Santos, Ileana Montanez Clemente, Gabriel Barletta and Kai Griebenow. Activation of Serine Protease subtilisin Carlsberg in Organic Solvents: Combined effects of Methyl -b-cyclodextrin and Water.Biotechnol and Bioeng. 1999, 21,1113-1118.
Ileana Montañez-Clemente, Edgardo Alvira, Minedys macias, Amaris Ferrer, Maricely Fonseca, Jessica Rodríguez, Anicele González, Gabriel Barletta. Enzyme Activation in Organic Solvents: Co-Lyophilization of Subtilisin Carlsberg with Methyl-B-Cyclodextrin Renders and Enzyme Catalyst More Active than the Cros-Linked Enzyme Crystals. Wiley Periodicals, Inc. 2002, 53-59.
Susimar González, Edgardo Alvira, Liz Vergara, Amaris Ferrer, Ileana Montañez and Gabriel L. Barletta. High Initial Activity but Low Storage Stability for Several Preparations of Subtilisin Carlsberg Suspended in Organic Solvents. ACS and AICE, Biotechnology 2002 18, 1462-1466.