Monday, 23 May 2005

This presentation is part of: Spectroscopy of Biomolecules Posters

Time-resolved Resonance Raman Spectroscopy of Tryptophans and Flavins

Ullas Gurudas and Johannes P.M. Schelvis. New York University, New York, NY

Photolyase is a flavoenzyme that repairs DNA-specific damage induced by ultraviolet light. The photoreactivation mechanism of photolyase is unique in the repair of the cis,syn cyclobutane pyrimidine dimer (CPD) by a light-driven, electron-transfer catalyzed monomerization.  A second electron transfer process can occur in the photoreduction of the neutral radical form of the flavin cofactor to its catalytically active reduced form. The pathway of this electron transfer is debated in the literature, and electron-hopping through a chain of tryptophans has been proposed. Both electron transfer processes are initiated from a flavin excited, which plays an important role in the light-driven process of DNA photolyase and other blue-light photoreceptors, and tryptophan radical intermediates have recently been recognized as important electron transfer intermediates.  Time-resolved resonance Raman (TR3) spectroscopy is an excellent tool to characterize these species and may provide new exciting information about their roles in blue-light photoreception and electron transfer.  We will present the first TR3 spectrum of a neutral Trp radical intermediate in a protein and preliminary results on a flavin excited state.



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