New techniques in fast time-resolved structure determination

New techniques in fast time-resolved X-ray crystallography provide a differ ent approach to understanding the structural basis of protein function. Two biological systems have been studied as part of the refinement of these te chniques, and have actually spurred new ideas in time-resolved structural s tudies. The dissociation of carbon monoxide from carbon-monoxy myoglobin ha s earlier been investigated over a time range spanning 18 orders of magnitu de (femtoseconds to hours) using spectroscopic methods. Rapid time-resolved determination of the entire myoglobin structure made it possible to determ ine both the position of the CO after photodissociation and the entire glob in structure, over a time range from nanoseconds to milliseconds, during wh ich the heme and globin relax and the carbon monoxide rebinds. Photoactive yellow protein, a relative newcomer to biophysical research, has a fully-re versible photocycle containing several spectrally distinct intermediates. I dentifying and solving the structures of each intermediate is the initial g oal in time-resolved studies on this protein and will contribute to a great er understanding of the biological process of light driven signal transduct ion.