PHOTOPHYSICS AND BIOLOGICAL APPLICATIONS OF 7-AZAINDOLE AND ITS ANALOGS

7-Azaindole is the chromophoric moiety of 7-azatryptophan, which is an alternative to tryptophan as an optical probe of protein structure an d dynamics. The great power of the 7-azaindole chromophore is that it is red shifted both in absorption and emission from tryptophan, that i ts fluorescence decay is single exponential in water under appropriate conditions, and that its emission is sensitive to solvent. In additio n, 7-azatryptophan can be incorporated into synthetic peptides and bac terial protein. In this article, the interactions of 7-azaindole with its environment are discussed. Special attention is directed to the di fference in its fluorescence properties in water as opposed to nonaque ous solvents, The sensitivity of 7-azaindole to its environment is dem onstrated and then exploited by studying it and its analogs in peptide s and in complexes with larger proteins containing many tryptophan res idues.