The active site of acetylcholin esterase probed by a photochromic ligand

The photochromic ligand PTA is shown to exhibit induced optical activity only if it is in the trans- form and bound to an asymmetric, ordered macromolecular matrix possessing hydrophobic binding sites. This observation can be used to probe for the existence and location of hydrophobic, ordered amino acids in the active cleft of an enzyme. It also explains the regulation of enzymic activity by reversible photo isomerization of PTA.