Phase separation of multicomponent phospholipid membranes can, for different membrane compositions, lead to fluid-fluid or fluid-solid coexistence of microscopic and nanoscopic domains. The solid domains are thought to be comprised, typically, of a gel phase in which molecules are tilted relative to the membrane surface; however, saturated-tail phosphatidylcholine lipids also have produced solids with ripple or corrugated structures, at least in single-lipid systems. Using different tracer lipids we have demonstrated polymorphism in the patchy or striped solid membrane domains formed during the cooling of giant unilamellar multicomponent vesicles. Observations are currently best explained by the formation of the gel at elevated tensions or, at long times low temperatures. Low tensions permit the formation of compact ripple phase domains. We show here how the formation of patches versus striped domains can be difficult to anticipate and therefore challenging to control because of the complex interplay between cooling rate, osmolarity, and membrane compositions, all variables that alter the vesicle tension as domains are forming. We additionally explore the interplay between membrane tension and rigid vs fluctuating curvature to produce long range ordering of patchy domains, controlling whether the domains are limited by vesicle curvature and whether they arrange into strings of patches or assemble with uniform spacings.

Stressful process of patterning fluid-solid membrane domains

2019 Spring National Meeting

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