[Photoconformational relaxation of protein structure from the data of tryptophan fluorescence]

It was shown that the decrease of polarization degree with increasing the wavelength of protein tryptophane fluorescence lambda f was caused by the lengthening of the lifetime tau. A considerable rotational nanosecond mobility of the internal tryptophanyls was observed. This mobility is not spontaneous but caused by photoexcitation. The increase of tau with lambda f is observed not only for multitryptophan proteins but also for monotryptophan ones and for DL-tryptophane in glycerol. The increase of tau is caused by relaxation processes occurring in close proximity to tryptophane after its photoexcitation and reflects the photoinduced nanosecond mobility of the tryptophane microenvironment. Photoconformational relaxation of protein in the nanosecond time range and possible role of this process in photoinactivation of enzymes are discussed.