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場所： 理化学研究所（和光）
研究棟本館 1F (124,126)
　　　 〒351-0198 埼玉県和光市広沢 2-1
　　　 http://www.riken.jp/index_j.html
Speaker: Prof. Gerhard Stock
Institute of Physical and Theoretical Chemistry, J. W. Goethe University Frankfurt, Germany
http://www.theochem.uni-frankfurt.de/
Title: Quantum-classical modeling of biomolecular spectra
Abstract:
Multidimensional IR spectroscopy allows us to study the structure and dynamics of peptides in great detail. A common approach to model these spectra is based on an exciton Hamiltonian for the vibrational system (e.g., the amide I band) under consideration. Classical molecular dynamics (MD) simulations are used to account for the time-dependent fluctuations of the Hamiltonian matrix, thus reflecting the structure and conformational dynamics of the system. Hence, the validity and interpretation of the simulated spectra depend to a large part on quality of the classical MD description.

In this talk, I wish to critically evaluate to what extent commonly used MD force fields and sampling techniques are able to correctly account for various molecular properties of spectroscopic interest. Key quantities in stationary IR spectroscopy include the conformational distribution (giving the thermal populations of conformational states), the solvation of the peptide (yielding solvent-induced frequency shifts), and vibrational level crossings (resulting in nonadiabatic vibrational transitions). Modeling transient IR spectra by nonequilibrium MD simulations, moreover, various dynamical properties of the simulation are of importance. In particular, this includes conformational transition rates and the energy transfer along the peptide backbone and to the solvent.