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DEUTERIUM‐ISOTOPE EFFECT ON THE FLUORESCENCE YIELDS AND LIFETIMES OF INDOLE DERIVATIVES–INCLUDING TRYPTOPHAN AND TRYPTAMINE

1970; Wiley; Volume: 12; Issue: 1 Linguagem: Inglês

10.1111/j.1751-1097.1970.tb06039.x

1751-1097

Robert W. Ricci,

Electron Spin Resonance Studies

Abstract— The fluorescence yields and lifetimes of indole, five of its alkyl detivatives, tryptophan, and tryptamine have been determined in degassed, heavy and light water at room temperature. All of the compounds have radiative lifetimes nearly identical to the parent compound indole, and a comparison of these results with recently reported data on tryptophyl derivatives disclosed a striking uniformity in radiative lifetimes between indole and many amino acids and peptides which contain the indole group as the fluorescence unit. The fluorescence rate k f in H 2 O, was found to be 4.5 × 10 7 sec ‐1 . The nonradiative decay rates were found to vary between 5.1 and 46 × 10 7 sec ‐1 and from a study of the deuterium‐solvent isotope effect and the deuterium‐substituent effect a mechanism for nonradiative deactivation is proposed which includes an isotopically dependent proton transfer and a pathway involving energy loss via the ring carbon hydrogen vibrations. Tryptophan at pH 7 was found to have a unique nonradiative decay scheme not evidenced at a pH 1 or pH 10.