Miller's research showcases the advantages of integrating computational and experimental biochemistry. However, both the subtlety of the interactions involved and the large variety of enzyme functions which the flavins assist are especially challenging. "In order to capture the particulars of an enzyme active site," she explains, "you need to include a few of the surrounding [protein] groups." It is crucial to identify features that are important to the flavin behavior without including inessential detail that will tend to blunt the focus of the conclusions and enormously increase the computational cost.

Another concern is the ability of existing experimental methods to support the extraordinarily fine structural detail needed to correctly compute electron density distribution. Miller says that typical current crystallographic structures available for proteins, at 1.8 angstrom resolution, do not have sufficient resolution for studies of flavin electron density. "That accuracy is as good as is available for proteins, but it's still very crude for quantum mechanical calculations. 0.1 angstrom makes a huge difference in the energy and the electronic structure calculated."

The reward of all this careful calibration and concentration on the infinitesimal world of flavin enzyme electron density, Miller hopes, will be a greater understanding of how the versatile flavins operate--and how they can be engineered to perform yet more useful tasks. "We would like to be able to design changes in an existing enzyme in order to make a new version that would catalyze desired chemistry," she explains. Engineered flavin enzymes are being used in the areas of drug metabolism and waste detoxification treatment and could even provide new gene therapies for congenital birth defects.

In the end, such essential biological processes come down to the valence electrons.

TEAM MEMBERS
Anne-Francis Miller, University of Kentucky
Joseph Walsh, National Cancer Institute
Ronald Koder, University of Pennsylvania

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Anne-Frances Miller,
University of Kentucky.
(Photo courtesy Magda Fus.)