Ultrafast Vibrational Dynamics and Infrared Spectroscopy of Biologically Relevant Hydrogen Bonds

• Applicant: Professor Dr. Oliver Kühn
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: from 2009 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 111246604

The goal of this project is to develop methods for treating the ultrafast nonlinear spectroscopy of hydrogen bonds in biologically relevant systems. On the methodological side this involves hybrid quantum mechanics/molecular mechanics trajectory simulations of nonlinear response functions. This is achieved by identifying a relevant system coupled to the fluctuating environment. Alternatively, fully classical simulations shall be performed which are based on the propagation of the first order stability matrix. Two applications will be considered: First, the dynamics of the hydrogen-bonded NH stretching vibration of a substituted adenine-uracil base pair in solution. Here, we want to find a microscopic explanation for the increase of vibrational relaxation upon hydrogen bonding. Second, we will investigate the amide A type vibrations of the hydrogen bonds in the cyclic peptide gramicidin S. In a first step anharmonic calculations of the spectral positions of specific NH-vibrations in the gas phase shall be used to validate a certain conformation. Subsequently, the simulation of one- and two-color pump-probe spectra shall enable us to assign these hydrogen bonds also in terms of their distinct relaxation pathways.

• DFG Programme: Research Grants