Because D- and L-amino acids are optical isomers, we used chiral substances to make the membrane. This allows both amino acids to alter the orientation of molecules at the membrane surface, consequently resulting in the alteration of the membrane electric potential. Two different types of optically active membranes were prepared, and each membrane consisted of an optically active reagent. A chiral alkaloid, quinine (L), was used as the chiral reagent and was dissolved in PVC and THF. Quinidine (D), which is an optical isomer of quinine, was used for comparison. Finally, the plasticizer (or lipids) was mixed with the PVC-optically active reagent-THF mixture resulting in the membrane solution. The two plasticizers (or lipids) used were TOMA, which gives rise to a positively charged membrane, and DOPP, which gives a neutral membrane.