Toward accurate computations in photobiology

This chapter reviews the results of recent computational studies of spectroscopy and molecular mechanism underlying the activity of very different photoactive proteins. It covers high-level (i.e. accurate) abinitio quantum chemical methodologies may be used to unveil the mechanistic details of photochemical processes occurring in photobiological systems. During the last few years, computational methods have been successfully applied to explore photon energy wastage mechanisms (for example, in fluorescent probes) and the mechanism of fast internal conversion in the DNA basis. Similarly, as an example of process where light is exploited to drive stereospecific reactions, as in the photochemical pericyclic reactions. The same types of processes can be found in photobiology. For instance, there are fluorescent proteins, such as the green fluorescent protein (GFP), where the energy of the photon is "wasted" radiatively to produce fluorescence while there are other proteins, such as the visual pigment Rhodopsin (Rh), where the energy of the photon is exploited to produce a change in the protein conformation. The chapter also discusses a recent attempt to map the photoisomerization path of the full Rh protein.