Elucidation of the mechanism of blue-light reception by vibrational spectroscopy

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It is the aim of the project to achieve an atomic level of understanding of the mechanism of biological blue-light reception. Reaching this objective requires a methodology with acute sensitivity and sufficient time-resolution. These requirements are met by vibrational spectroscopy. The catalytic changes involve vibrational changes of the chromophore, the protein backbone and amino acid side chains. They can be as minute as alterations in hydrogen-bonding or protonation changes. The intermediates of the photoreaction along the reaction coordinate are either trapped by various techniques or directly traced in a time-resolved experiment. We will employ FT-IR spectroscopy which monitors virtually all vibrations of the protein. These data are compared to resonance-Raman spectroscopy which is selective for the vibrational modes of the chromophore. The biological systems under study are the LOV (Light Oxygen Voltage) domains, the BLUF (receptors of Blue Light Using FAD as chromophore) domains and the cryptochromes. Most of these samples will be provided by our collaborators. However, the cryptochrome CPH will be expressed in our lab. The project will greatly benefit from the structural studies of this collaborative effort on the one hand and from the expression of new blue-light photoreceptors on the other hand.