Charge reversal in anionic liposomes: experimental demonstration and molecular origin.

: We present experimental and simulation evidence for a new mechanism of charge reversal operating only for ions capable to penetrate into soft interfaces. It is based on the preferential solvation of counterions by amphiphilic molecules and hydration water rather than by bulk water. This mechanism does not require high surface charge densities and it is not affected by the addition of 1:1 salt. This behavior is opposite to that observed in systems as diverse as microfluidic channels or latex colloids. The robustness of the mechanism to physiological amounts of 1:1 salt suggests a significant impact in processes involving ion-amphiphile interaction in salty water (typical, e.g., of biophysics).