Research Projects

Biological Activation of Small Molecules (A)

One of the most tantalizing challenges at the interface of biology and chemistry is the understanding of complex biochemical processes in which inert molecules, such as H2, N2 and CO2, are transformed into more reactive forms, such as protons, electrons, ammonia, and methane. These processes occur at ambient temperature and pressure; therefore their technological implementations would be valuable. These novel \'green chemical\' transformations developed by learning from Nature, would also be environmentally sound, hazardous waste-free technologies.
N-cycle: The active-site of the nitrogenase metalloenzyme is the so-called iron-molybdenum-cofactor (FeMo-co), where the N2 binding and reduction occur. The FeMo-co has a rich activation chemistry, since it is capable of reducing N-N, C-N, C-C triple and double bonds such as in N2, cyanides, imines, alkines and alkenes. Inhibition studies indicate multiple substrate binding sites. Side-directed point-mutations reveal an intricate role of the protein environment. Other studies show the critical role of the homocitrate ligand. I am investigating the molecular basis of these environmental effects and the mechanism of the N-cycle.
H-cycle: The hydrogenases are responsible for H2 reduction and oxidation reactions. In the microorganism Clostridium pasteurianum, the H-cycle is coupled to the N-cycle. The evolved H2 as a sideproduct is recycled by hydrogenases. The active-site structure has revealed a biochemically unusual coordination of Fe ions with cyanide and carbonyl ligands. The [4Fe-4S] cluster, which is assumed to be the electron storage for the redox chemistry, can donate or accept electrons formed in H2 evolution or uptake, respectively. The H-cluster is the site where the bond cleavage/formation occurs. The roles of the iron atoms, the bridging dithiolate, and the CO/CN ligands are the focus of my research.

Publications

Szilagyi RK, Bryngelson PA, Maroney MJ, Hedman B, Hodgson KO, Solomon EI, "S K-Edge X-ray Absorption Spectroscopic Investigation of the Ni-Containing Superoxide Dismutase Active Site: New Structural Insight into the Mechanism." J. Am. Chem. Soc. 126 3018-3019 (2004)

Frank P, Benfatto M, Szilagyi RK, De\'Angelo P, Della Longa S, Hodgson K, "The Solution Structure of [Cu(aq)]²⁺ and Its Implications for Rack-Induced Bonding in Blue Copper Protein Active Sites." Inorg. Chem. 44 1922-1933 (2005)

Szilagyi RK, Schwab DE , "Sulfur K-edge X-ray absorption spectroscopy as an experimental probe for S-nitroso proteins." Biochem. Biophys. Res. Commun. 330 60-64 (2005)

Personnel:
Robert Szilagyi

Keywords:
Bioinorganic, Biophysical, Computational, Inorganic, Mechanism, Physical, Spectroscopy, Structure

Return to regular view	Text-only	Updated: 11/6/09