Using Chol/DPPC mixed monolayer as a model mammalian membrane,the interaction between AmB and membrane with cholesterol was investigated by recording л-A isotherms spread on Tris-HCl buffers containing different ions:(1)a physiological concentration of single Na+,K+,or Ca2+ions;(2)the absence or excess of Na+,K+,or Ca2+ions based on the coexistence of physiological concentrations of the three types of ions.