Analysis of Intermediate Structures of Photoactive Yellow Protein by Raman Spectroscopy and Quantum Chemical Calculations

Abstract

Recent advances in computational chemistry have significantly enhanced the capability of vibrational spectroscopy such as a Raman technique. It is now possible to simulate the Raman spectrum for large molecules such as proteins on the basis of ab initio quantum chemistry. Using both resonance Raman spectroscopy and quantum chemical calculations, we have determined the chromophore structures in the intermediate states of photoactive yellow protein(PYP). We have successfully extracted key information on the chromophore-protein interactions. The results permit us to propose structural models of the intermediates, which reveal the photocycle mechanism of PYP under physiological conditions.