Berlin 2012 – scientific programme

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BP: Fachverband Biologische Physik

BP 7: Posters: Proteins

BP 7.21: Poster

Monday, March 26, 2012, 17:30–19:30, Poster A

Solvent induced isomerization in phycocyanobilin — •Tobias Watermann, Hossam Elgabarty, and Daniel Sebastiani — Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin

Phytochromes belong to the family of light detecting proteins, that are responsible for the reaction of biological systems to light. Their central functional part is a chromophore, which isomerizes upon excitation and initializes the signaling process of the protein. Recent NMR experiments [1] on the isolated chromophore phycocyanobilin show differing spectroscopic properties for different solvents. We investigate the underlying conformational space by means of ab-initio molecular dynamics and free energy calculations as well as ab-initio spectroscopy [2]. It turns out that it is of crucial importance to include the explicit solvent and its interaction with the chromophore. In our ab-initio molecular dynamics simulations, we observe specific preferences for certain conformations as a function of the polarity of the solvent. These computational results are confirmed by comparing ab-initio NMR chemical shifts in the different situations to corresponding experiments. This solvent dependent effect can be traced back to a change in the equilibrium between intra- and intermolecular hydrogen bonds of the chromophore and the solvent.

1. M. Röben, P. Schmieder, Magn. Reson. Chem., 49, 543-548 (2011)
2. T. Watermann, H. Elgabarty, M. Röben, P. Schmieder, D. Sebastiani (Submitted)