A Preliminary Application of Phase/Modulation Fluorometry to the Tryptophan Problem

Abstract

Rayner and Szabo^l concluded that the fluorescence decay of tryptophan in aqueous solution at 20⁰ and neutral pH was best described by two lifetimes with relative weights varying across the emission band. Specifically, they reported a short (0.5ns) and a long (3.lns) component, the short component being more prominent at the blue edge of the emission spectrum. Additional studies by the same researchers² and others³ have generally supported the original findings. The published investigations have utilized pulse fluorometry with single-photon counting. Since the phase method generally offers superior precision over the pulse method for subnanosecond lifetimes, it seems appropriate to consider the applicability of the former technique to the tryptophan problem.