Biological membranes are self-assembled highly flexible structures which can undergo an array of dynamic conformational transitions vital to many biological processes. One of the possible collective motions of lipid molecules is the thickness fluctuation, which has been proposed as a mechanism for membrane pore formation. Although computational works have captures such fluctuations, the motion has never been directly observed experimentally. In the present study, we utilized neutron spin echo spectroscopy to measure such fluctuations in model systems of relatively monodisperse unilamellar vesicles. The results show that above the main transition temperature, Tm, the relaxation time of the motion is on the order of 100 ns with an amplitude of a few angstroms. Below Tm however the mode was not observed within our time window, suggesting it is either suppressed or more realistically is significantly slowed down.

Experimental observation of thickness fluctuations in lipid unilamellar vesicles

245th National Meeting (2013)

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