Writing and erasing barriers to lateral mobility into fluid phospholipid bilayers

We describe a method for making and erasing barriers to the lateral diffusi on of membrane components in fluid lipid bilayers supported on glass substr ates. When a bilayer is mechanically partitioned by scratching the membrane -coated surface at basic pH, barriers to lateral diffusion are formed which prevent mixing between the regions separated by the scratches. Upon loweri ng the pH, the bilayer is observed to spread over the scratch boundary, all owing diffusive mixing between the previously separated regions. This is ex ploited in combination with electrophoresis within the membrane to separate fluorescently labeled charged lipid probes, partition them with a scratch, and allow remixing to occur when the scratch is healed. This method for me mbrane manipulation can be used to transform a homogeneous membrane into an array of corrals with different compositions while preserving the ability to allow subsequent remixing. This approach should be useful for examining the kinetics of reactions and the assembly of fluid membrane-associated com ponents in a native setting, and for investigating the dynamics of two-dime nsional fluids.