Electrostatic repulsion of positively charged vesicles and negatively charged objects

A positively charged, mixed bilayer vesicle in the presence of negatively c harged surfaces (for example, colloidal particles) can spontaneously partit ion into an adhesion zone of definite area and another zone that repels add itional negative objects, Although the membrane itself has nonnegative char ge in the repulsive zone, negative counterions on the interior of the vesic le spontaneously aggregate there and present a net negative charge to the e xterior. Beyond the fundamental result that oppositely charged objects can repel, this mechanism helps to explain recent experiments on surfactant ves icles.