Structure and Dynamics in Amphiphilic Bilayers: NMR and MD simulation Studies
Sammanfattning: Solid-state nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations were employed to study molecular structure and dynamics in amphiphilic bilayers. This thesis reports on method development and practical applications to two types of bilayer systems: simple cell membrane models composed of phosphatidylcholine lipids and cholesterol; and liquid crystals composed of ethyleneoxide-based surfactants often used in technological applications and in fundamental studies of amphiphile self-assembly. Structural analysis of the systems is done by means of C-H bond order parameters. Complete profiles of C-H bond order parameters are determined by using advanced solid-state 13C-1H NMR recoupling techniques. The profiles are obtained from samples with natural abundance of isotopes by combining polarization transfer methods with different sensitivities. The analysis of the order parameters measured is based on a combination of NMR experiments and MD simulations. With respect to the dynamics in bilayer systems, an NMR protocol for measurement of rotational diffusion is presented and applied to a lipid bilayer system. The method enables quantification of the effective correlation time of C-H bond reorientation motions at time-scales between nanoseconds and microseconds.
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