Study of triplet-singlet energy transfer in an enzyme-dye complex using optical detection of magnetic resonance

Abstract

Optical detection of magnetic resonance (ODMR) measurements were made on the enzyme .alpha.-chymotrypsin and on its complex with the dye, proflavin. Evidence that triplet-singlet energy transfer occurs in the complex is provided by the observation of characteristic tryptophan ODMR signals while monitoring the delayed fluorescence of the dye. The luminescence decay kinetics of the complex indicates that nontrivial triplet-singlet transfer originates from several (at least 3) tryptophan residues of the enzyme. ODMR sensitivity can be enhanced by coupling the sublevels of a weakly radiative triplet state to a fluorescent dye which satisfies Forster''s, conditions for energy transfer.