Abstract

Although most amino acids readily react with hypochlorous acid (HOCl), only the reaction involving tryptophan (Trp) produces a measurable chemiluminescence (CL). Most of this luminescence takes place after total consumption of HOCl when the process is carried out in an excess of Trp. The quantum yield of the process is relatively low (2 × 10-8 Einstein/mol HOCl reacted). The luminescence is attributed to free radical-mediated secondary reactions of the initially produced chloramines. This is supported by experiments showing that the chloramines produced when HOCl reacts with alanine are able to induce Trp chemiluminescence. and that this luminescence is partially quenched by free radical scavengers. The spectral changes and the effect of pH upon the observed luminescence are compatible with light emission from products produced in the free radical oxidation of Trp. Copyright @ 2002 John Wiley & Sons, Ltd.