Third Microsymposium of the "International Scholarship Program for Graduate Studies in Faculty of Chemistry, University of Warsaw - From simple molecules to nanostructured and bioactive materials" October 6 - 8th, 2011, Palace in Łochów, Poland
Chronicle
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Thursday Oct. 6th 11:45-12:45 - Prof. Gary J. Blanchard - invited lecture Optically Induced Perturbations in Bilayer Structures. Consequences on Local Organization H. A. Pillman and G. J. Blanchard, Michigan State University, Department of Chemistry, East Lansing, MI 48824 The interaction of light with constituents within lipid bilayer structures can cause perturbations to the local organization of the bilayer. This phenomenon can be important for proteins or other bilayer constituents that absorb light. The issue of importance is the dissipation of excess energy introduced to the system optically, and its consequences on the lipid bilayer structure. We have investigated the effects of transient heating on the molecular reorientation dynamics of perylene incorporated into the nonpolar acyl chain region of unilamellar vesicles comprised of DMPC, and DMPC/cholesterol as a function of system temperature. We observe distinctly different reorientation behavior for perylene, depending upon whether it is excited to its S1 or S2 electronic state. This difference is due to the dissipation of excess excitation energy through nonradiative relaxation from the S2 to the S1 manifold. The thermal energy deposited into the lipid bath following S2 <-- S0 excitation results in faster rotational diffusion than that observed for excitation to the S1 state. The presence of cholesterol in the bilayer structure alters the rigidity and local organization of the system, and different transient temperature changes are seen for bilayers with and without cholesterol. 
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