α-Synuclein Reduces Tension and Increases Undulations in Simulations of Small Unilamellar Vesicles

Using coarse-grained molecular dynamics simulations we have explored the effect of a-Synuclein (alpha Syn) on the structural and mechanical properties of small unilamellar vesicles in the fluid-phase. The study is motivated by observations that a high density of membrane-bound alpha Syn inhibits the fusion of synthetic small unilamellar vesicles. By combining three-dimensional pressure tensor calculations with our recently developed spherical harmonics fluctuation analysis approach, we show a reduction in membrane surface tension and increased membrane undulations when alpha Syn is bound to the vesicle's outer leaflet at a 200: 1 L/P. The protein effects these changes by decreasing the negative pressure in the headgroup region of the outer leaflet and increasing the positive pressure throughout the hydrocarbon core.