NMR-spektroskopische Untersuchungen der membranmodifizierenden Eigenschaften polyphiler Moleküle: Struktur und Lipiddynamik

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The goal of this subproject is the comprehensive NMR-spectroscopic characterization of the membrane-modifying properties of polyphilic molecules which are synthesized in the subprojects of the other groups, and which are studied by complementary techniques in the groups of Blume and Bacia. Due to its chemical regio-selectivity, solid-state NMR, more than any other method, is well suited to clarify the origins of membrane-modifying properties on a molecular basis. In the first funding period, we were mainly occupied with methodological developments, subjecting different NMR methods to conceptual tests and widening their application range and the known limitations, and gained first insights into the interaction mechanisms. We have established methods that report on the one hand (i) on the structural arrangement of guest molecules at or in the membrane via the measurement of dipole-dipole couplings and cross relaxation/spin diffusion, and on the other hand (ii) on changes of the membrane properties such as stiffness, porosity, or defect content. For the latter, measurements of CH dipole-dipole couplings in the lipid chains, static 2H spectra of the interlamellar water, diffusion measurements of the through-membrane transport, and studies of the reorientation dynamics of the head groups via the 31P chemical shift anisotropy have proven useful. However in some cases, owing to partially contradictory and incomplete literature data, we see a further need for methodological development. A part of the studied polyphiles turned out to be merely surface active, i.e., small lamellar fragments (bicelles) were stabilized by lateral interactions and no changes in the molecular dynamic properties of the lipids were detected. Membrane-soluble polyphiles with distinct membrane-modifying properties were available only by the end of the period under report, and are currently subjected to a comprehensive study. First interesting results are presented in the project report