The effect of various solutes on the fluorescence of tyrosyl and tryptophyl residues

Abstract

The quenching of the fluorescence of tryptophan, tyrosine, and model compounds containing these residues has been investigated over a range of conditions with phosphate and Tris buffers in aqueous solution. Various thiols and their corresponding disulphides have been studied as quenchers of fluorescence emitted by the model chromophores. All the sulphur compounds quenched the emission but it was not possible to separate the contributions due to "true" quenching and to competing absorption of the excitation radiation by these compounds ("pseudo" quenching). A method is described for evaluating the relative quenching power of different substances on the emission from model tryptophan and tyrosine derivatives.