Issue Date: February 11, 2008
Alfred Bader Award in Bioinorganic or Bioorganic Chemistry
Sponsored by Alfred Bader
During the past several decades, research performed by Lawrence Que Jr. has changed the way scientists think about the chemistry of nonheme iron proteins and complexes and has placed him among the world's most prolific and important practitioners of bioinorganic chemistry.
Que, 58, 3M/Alumni Distinguished Professor of Chemistry at the University of Minnesota, Twin Cities, has played a pioneering role in understanding the functions that nonheme iron centers play in dioxygen activation in biology. These enzymes catalyze a diverse array of metabolically important transformations that include hydroxylation of aliphatic and aromatic C-H bonds, heterocyclic ring formation, arene cis-dihydroxylation, and oxidative ring cleavage. Using a multidisciplinary approach, Que has successfully combined biochemical/biophysical studies of metalloproteins and synthetic approaches to develop structural and functional models for these systems in order to produce as complete a picture as possible for the metal active site and its role in catalysis.
Highlights of Que's research accomplishments in the biomimetic area include the complete characterization of the first complexes containing the bis(µ-oxo)diiron "diamond" core, which has led to their postulated involvement in the mechanisms of dioxygen activation and substrate oxidation in important enzymes such as methane monooxygenase and ribonucleotide reductase. His group's synthesis and characterization of these systems represent a landmark in modern inorganic chemistry research and have captured the imagination of the international scientific community.
Que has also made spectacular progress in obtaining the first synthetic nonheme iron(IV)-oxo complexes. In 2003, he reported the first crystal structure of a mononuclear Fe(IV)=O complex. Subsequently, other examples have been obtained, including room-temperature stable complexes that hydroxylate cyclohexane. Such species are related to proposed intermediates in the catalytic cycles of some nonheme iron enzymes.
Another significant thrust in Que's efforts has been the design and characterization of functional models for iron enzymes, with the goal of mimicking key aspects of enzyme reactivity. In the past 20 years, Que has succeeded in developing excellent models for the oxidative cleavage of catechol (both intradiol and extradiol) by catechol dioxygenases, oxygen activation by α-keto acid complexes, arene hydroxylation, and olefin cis-dihydroxylation. In all cases, he reported the first well-characterized examples.
These biomimetic efforts led to the first examples of bioinspired nonheme iron catalysts capable of stereospecific alkane hydroxylation and enantioselective olefin cis-dihydroxylation with H2O2 as oxidant. These results may be useful toward developing new "green" oxidation catalysts. Low-temperature studies allowed the direct spectroscopic observation of an Fe(III)-OOH intermediate, and isotope labeling studies with 18O-labeled water strongly implicated the participation of an Fe(V)=O oxidant. This key finding has general significance in the chemistry of oxygen activation.
Que received a B.S. in chemistry in 1969 from Ateneo de Manila University, in the Philippines, and a Ph.D. in chemistry in 1973 from the University of Minnesota. He joined the faculty at Cornell University in 1977 and moved to the University of Minnesota in 1983.
The award address will be presented before the Division of Inorganic Chemistry.
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