NONRADIATIVE PATHWAYS OF 7-AZAINDOLE IN WATER

The 7-azaindole chromophore in water is studied by means of picosecond absorption and fluorescence spectroscopy in order to determine its nonradiative decay pathways. It is concluded that a small population of 7-azaindole molecules (approximately 20%) undergo excited-state tautomerization in about 70 ps. Intersystem crossing and photoionization are also identified as nonradiative decay channels. Photoionization occurs largely from an electronic state lying slightly in energy above the fluorescent state. This new understanding of the photophysics of the 7-azaindole chromophore in water will be essential in interpreting its behavior when it is used as an optical probe of protein structure and dynamics.