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MO: Molekülphysik

MO 30: Poster: Quantum Chemistry

MO 30.4: Poster

Dienstag, 14. März 2006, 16:30–18:30, Labsaal

Quantum-classical calculation of time-resolved infrared spectra of biomolecules — •Roman Gorbunov, Nguyen Phuong, and Gerhard Stock — Institut für Physikalische und Theoretische Chemie, J.W. Goethe Universität, Marie-Curie-Str. 11, 60439 Frankfurt am Main, Germany

Various approaches for the calculation of vibrational spectra of peptides in aqueous solution are discussed. To describe the amide I vibrations in peptides, we use an ab initio based exciton model combined with a solvent correction of local amide I frequencies. The exciton model of amide I vibrations contains the conformationally dependent force constants of the local vibrations as well as the coupling between them. The solvent correction is based on an empirical relation between frequency of the local vibrations in peptide and the corresponding electric field produced by surrounding water molecules. Conformational dynamics of the peptide and the dynamics of surrounding water molecules were obtained by classical molecular dynamic simulations. In the present work, we have studied the influence of the solvent correction on the vibrational spectra. Different protonation states (reflecting different pH values) were considered and their influence on the vibrational spectra was investigated. The accuracy of the second order cumulant expansion and the Condon approximation were studied for different cases.