Regensburg 2013 – scientific programme
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BP: Fachverband Biologische Physik
BP 28: Focus session: Intracellular Spectroscopy
BP 28.9: Talk
Thursday, March 14, 2013, 12:15–12:30, H44
Calculation of the CD spectrum of a flexible peptide — •Zlatko Brkljača1, Karmen Čondić-Jurkić1,2, Momir Mališ2, David M. Smith2,3, and Ana-Sunčana Smith1 — 1Institut für Theoretische Physik, Universität Erlangen-Nürnberg, Erlangen, Germany — 2Ruđer Bošković Institute, Zagreb, Croatia — 3Computer Chemie Centrum, Universität Erlangen-Nürnberg, Erlangen, Germany
Circular dichroism (CD) spectroscopy is a standard experimental method employed in the structural characterization of optically active chiral molecules, such as proteins and peptides. Because the CD spectrum of a molecule is an ensemble average over its entire conformational phase space, the interpretation of the experimental data is challenging. This is particularly true for highly flexible peptides, where the spectra cannot be unambigously interpreted without theoretical modelling. However, so far there has been no accurate theoretical approach to predict peptide CD spectra. We address this problem by developing a method that combines replica exchange molecular dynamics to generate the conformational phase space, and TDDFT to calculate the electronic transitions. Thereby we systematically treat the solvent induced polarization of the peptide. We validate our method on an example of the CD spectrum of the opioid growth factor (Met-enkephalin). On the level of the single conformation we compare TDDFT with high level ab-initio calculations (RI-CC2), while on the level of the ensemble we make a comparison with the experimentally measured spectrum. Good agreement is obtained in both cases.