Issue Date: January 19, 2009
Ronald Breslow Award For Achievement In Biomimetic Chemistry
Sponsored by the Ronald Breslow Endowment
A pioneer in bioinorganic and biomimetic chemistry, James P. Collman has made major contributions to the understanding of the mechanisms of biological proteins by designing, constructing, and studying functional synthetic analogs of metal-containing biological systems. His work on hemoglobin, myoglobin, and cytochrome c oxidase have led to a deeper understanding of the way protein-metal interactions influence the function of these key biomolecules.
"Collman's research has changed the way in which we approach and understand the chemistry of biology," notes chemistry professor John Brauman of Stanford University. "This is a result of critical insights coupled with extraordinary scientific achievements. This powerful combination has led to a new paradigm in chemistry."
Collman and coworkers were first to prepare and characterize stable, functional analogs of the active sites of hemoglobin and myoglobin. These "picket-fence porphyrins" are discussed in many biochemistry textbooks. The power of picket-fence porphyrins is that they mimic the magnetic, spectroscopic, and structural characteristics of the hemoglobin and myoglobin active sites; bind O2 reversibly, as the two proteins do; and have O2-binding affinities similar to those of the two proteins.
The researchers used X-ray diffraction studies of picket-fence porphyrins to clarify the different structural properties of the iron-O2 linkage in the two main forms of hemoglobin quaternary structure (its R and T states). These studies enabled them to explain the origin of the states' different O2 affinities, a difference that makes it possible for hemoglobin to bind O2 in the lungs and deliver it to tissues. The models also mimic the low affinity of hemoglobin for CO.
Collman and coworkers also created functional mimics of the O2-binding and O2-reducing site in cytochrome c oxidase. During respiration, this enzyme catalyzes the conversion of O2 to H2O, which leads to production of adenosine triphosphate, the energy currency of cells in aerobic organisms. The active site of the enzyme consists of an O2-binding iron porphyrin coupled to a copper ion called CuB, but the way these structures work together to catalyze the O2-to-H2O conversion was unclear.
By covalently attaching their functional mimics to synthetic membranes on electrode surfaces, the researchers reproduced the slow, diffusion-limited electron delivery conditions under which cytochrome c oxidase operates in living cells. These experiments were the first to carry out electron delivery to a biomimetic catalyst site in a rate-limited manner.
Electrocatalytic studies of O2 reduction by the functional mimics enabled Collman and coworkers to determine the previously unknown role of CuB and a neighboring tyrosine in the four-electron reduction of O2 by cytochrome c oxidase. Their work showed that CuB makes it possible for the enzyme to catalyze O2 reduction without producing toxic, partially reduced oxygen species.
Collman, 76, was born in Beatrice, Neb. He earned B.S. and M.S. degrees in chemistry at the University of Nebraska, Lincoln, in 1954 and 1956, respectively, and a Ph.D. in chemistry at the University of Illinois, Urbana-Champaign, in 1958. He served on the chemistry faculty at the University of North Carolina, Chapel Hill, from 1958 to 1967. Since 1967, he has been professor of chemistry at Stanford University, and he currently holds the George & Hilda M. Daubert Endowed Chair in Chemistry. His publications include three books and more than 355 scientific papers.
Collman will present the award address before the Division of Inorganic Chemistry.
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