Hannover 2010 – scientific programme
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MO: Fachverband Molekülphysik
MO 17: Biomolecules
MO 17.7: Talk
Wednesday, March 10, 2010, 18:00–18:15, F 142
Microhydration of two polyalanine-based peptides — •Sucismita Chutia, Mariana Rossi, Volker Blum, and Matthias Scheffler — Fritz Haber Institute, Berlin, Germany
Microsolvation studies using vibrational spectroscopy are an important approach for analysing the influence of the solvent environment on peptides. Two small peptides have been the subject of such experimental studies in the recent years: Ac-Ala5-LysH+ [1] and Ac-Phe-Ala5-LysH+ [2]. The aim of this work is to theoretically identify the lowest-energy conformers of these peptides and carry out microhydration studies to find the preferred water binding sites. We first use a molecular dynamics calculation with the OPLS-AA force-field potential in the TINKER package to scan the potential energy surface for a wide variety of candidate conformers. We then use the all-electron electronic structure code FHI-aims [3] to follow up these structures with van der Waals corrected density functional theory to determine the energy hierarchy, and vibrational frequencies for comparison with the experimental spectra. Our findings indicate that both helical and "non-helical" conformers are present among the low-energy conformers of Ac-Phe-Ala5-LysH+, similar to the case of Ac-Ala5-LysH+. We find that, for both Ac-Phe-Ala5-LysH+ and Ac-Ala5-LysH+, the water molecule binds to the protonated lysine end in the lowest energy conformer. We also address the accuracy of the pre-screening forcefield compared to DFT-vdW. [1] M. Kohtani and M.F.Jarrold, JACS, 126, 8454-8458 (2004) [2] J.A. Stearns et al, PCCP, 11, 125-132 (2009) [3] V. Blum et al, Comp. Phys. Comm. 180, 2175 (2009).