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Chemistry and Biochemistry
University of California
230 Physical Sciences Bldg.
Santa Cruz, CA 95064
Phone: (831) 459-4002
Fax: (831) 459-2935
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Pradip Mascharak Professor of Chemistry Faculty Undergraduate Advisor B.S., M.S., University of Burdwan, India Ph.D., Indian Institute of Technology, Kanpur Postdoctoral work: Stanford University, Harvard University, Massachusetts Institute of Technology Office: 254 PSB Phone: (831) 459-4251 Fax: (831) 459-2935 pradip@chemistry.ucsc.edu

Mascharak Research Group Department of Chemistry University of California 1156 High Street Santa Cruz, CA 95064 Office Hours Class Times & Locations Labs: 243A PSB, 9-4605

RESEARCH INTERESTS: Inorganic Chemistry, Drug Design, Protein Active Site Modeling

Pradip Mascharak is interested in bioinorganic chemistry. His research activity includes modeling the active sites of enzymes that contain transition metal ions. This research involves syntheses of metal complexes/clusters with biologically relevant designed ligands that mimic various metalloenzymes in their structural, spectroscopic and catalytic behaviors. The ultimate goal is to elucidate the mechanism(s) of the complex biological transformations occurring at the metal-containing active sites. At this time, two enzymes are under study. The first one, nitrile hydratase (NHase), is involved in microbial assimilation of organic nitriles. The active site of this enzyme contains either a low-spin Fe(III) or non-corrin Co(III). The second enzyme is acetyl Co-A synthase/CO dehydrogenase (ACS/CODH), an enzyme involved in CO₂-fixation by various anaerobic chemotrophs. The so-called A-cluster of ACS/CODH contains a Ni-Ni-Fe₄S₄ unit. Both these active sites have very unusual coordination structures. The metal centers are attached to the peptide backbone via carboxamido nitrogens and Cys-sulfurs. In addition, two of the three Cys-S centers of NHase are post-translationally modified to Cys-sulfenato (-SO-) and -sulfinato (-SO₂-) groups. During the past few years, Mascharak's group has synthesized and structurally characterized series of designed metal complexes that resemble such active sites very closely and studied their reactivities to establish the mechanism of nitrile hydrolysis and acetyl group formation from CO and CH₃ at the metal sites. Several of the model complexes have been used to perform analogous chemical transformations under very different conditions. Syntheses of novel bio-inspired catalysts on the basis of these studies are in progress.

In recent years, metal nitrosyls like sodium nitroprusside have been used to control blood pressure and related hypertensive episodes. NO complexes that release NO upon illumination have been tried as agents in photodynamic therapy. During the past few years, Mascharak' group is involved in synthesizing designed metal nitrosyls that photorelease NO under very mild conditions (low intensity visible or UV light). Various chemical principles guide the design of such nitrosyls that deliver NO to biological targets under specific conditions. A variety of spectroscopic, magnetic and photochemical studies are performed to identify the factors responsible for the controlled release of NO from such nitrosyls upon illumination. Results of parallel theoretical studies are also utilized to elucidate the electronic origin of the NO photolability. At the present time, attempts are also being made to attach these NO-donors on beads of inert matrix that could be selectively placed at biological targets and then conveniently triggered to release burst of NO upon illumination.

Another research project in Mascharak's group is related to the area of new "Green Chemistry". For some time, this group has been studying oxidation of various organic substrates (including alkanes and alkenes) by non-heme iron and cobalt complexes in conjunction with O₂, H₂O₂and ROOH. The goal of this project is to synthesize catalysts that operate under mild conditions (less energy requirements) and utilize safer reagents (like O₂) for oxidations.

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