The effects of various amino acids on the membrane characteristics of liposomes were investigated in terms of particle size, encapsulating efficiency, micropolarity, and microviscosity. The particle sizes of the liposomes encapsulated buffer solutions including acidic amino acids were greater than these encapsulated buffer solutions including other amino acids. However, the encapsulating efficiencies of the liposomes encapsulated acidic amino acids were less than other liposomes. It is found that an electrostatic repulsion interaction between negative charges of the charged material (DCP) on the liposome surfaces and of the acidic amino acid in the aqueous solutions lead to looseness of orientation of lipid molecules, resulting in enhancement of their particle sizes and the micropolarity of liposomal membranes, and in decrement of the microviscosity of the membranes.