Cryophotolysis of ortho-nitrobenzyl derivatives of enzyme ligands for the potential kinetic crystallography of macromolecules

Even under cryogenic conditions at 100 K, the photofragmentation reaction o f ortho-nitrobenzyl derivatives of enzyme . ligands (see picture; Y = arsen ocholine or dTMP) is demonstrated to occur, as analyzed by microspectrophot ometry and HPLC. In particular, the possibility to fragment, at 100 K, a ca ged cholinergic ligand complexed within a crystal of acetylcholin-esterase was shown. This new approach in cryocrystallography could be used, for exam ple, for the controlled release of an enzyme substrate or product bound in the active site.