Research objectives and content
The best exampie of a biological photoreceptor acting as a proton pump is the bacterial pigment bacteriorhodopsin (BR). Photothermal methods such as temperature (T)-dependent laser-induced optoacoustic spectroscopy (LIOAS) and photothermal beam deflection (PBD) permit the determination of volume changes associated with the various steps of the light-induced process, in acqueous solutions at regular temperatures LIOAS studies with BR have shown that structural volume changes, AVR, occur in the ns time range; being followed by large changes in the u-and ms time ranges, as shown by PBD studies. Experiments with isomerizable dyes, models for the retinal chromophore in BR, indicated that the values of AVR result from a rearrangement of the solvation sphere in the photoisomerized chromophore. For photoinduced electron transfer reactions with Ru-cyano complexes, the AVR values were correlated with changes in specific solute-solvent interactions: To better understand the molecular origin of the AVR values, BR mutants in which amino acids have been exchanged, will be studied by T-dependent LIOAS and PBD, as well as model systems, such as various pH indicators in water, alone and with small polypeptides and lipids, both in regular and deuterated solutions
Training content (objective, benefit and expected impact)
The project will allow the candidate to carry out a postdoctorate research programme in the fields she has worked in during her PhD research training, namely photoactive molecules of biological interest. In particular the candidate will extend her skills in dealing with photobiological problems from a biophysical and chemico-physical point of view, with particular regard to primary molecular events triggered by the absorption of light and resulting in structural changes of the system involved. She will also gain wider laboratory experience in photocalorimetric and time resolved spectroscopic methods, taking advantage of the facilities of the host institution and the large experience in this field of the research unit.