Laser technique gives new views on nitrogen chemistry

17 Jun 2002

Researchers have used photocrystallography to gain insight into the structure of fleeting compounds in the body.

Chemists at the University of Buffalo, US, have developed a new technique for determining the structures of normally unstable chemical species that play a basic role in body chemistry. The method uses a combination of X-ray diffraction and laser excitation.

Called photocrystallography, the technique involves exciting a molecular crystal using a laser pump and probing its structure with an X-ray diffractometer.

The approach is allowing researchers to observe molecules that exist for millionths or even billionths of a second - while one molecule is binding to another - and has provided new information on how certain nitrous oxide compounds bind to proteins.

It has also fundamentally altered a widely held assumption that the new chemical states of nitrosyl compounds (in which nitric oxide binds to transition metal atoms) generated by illumination with laser light were electronically excited states: instead the work has shown that these states are in fact "linkage isomers" - with new atomic arrangements.

"In short, for a very brief time, they become different molecules," said Philip Coppens, Distinguished Professor and principal investigator on the project. "That is significant, as such simple molecules play a crucial role in body chemistry, such as in vasodilation, inhibition of platelet aggregation and in nerve transmission," he said.

Coppens is working in collaboration with George B Richter-Addo, a professor in the Department of Chemistry and Biochemistry at the University of Oklahoma, and Kimberly Bagley, professor of chemistry at Buffalo State College.