Metachromatic properties of admixture of thionine and methylene blue(MB) in aqueous solution and phospholipid bilayer membrane have been studied by absorption spectroscopy. When thionine and MB were mixed, new coaggregate has been formed because of MB was redistributed to thionine aggregate. In phosphlipid bilayer membrane system, the highly concentrated thionine was easily formed the coaggregation with MB moiety independent of MB concentration, and absorption band of admixture were more transferred to short wavelength than aqueous system. In monomeric thionine concentration, the coaggregation band was observed at the middle wavelength between the site of monomeric thionine and the site of dimeric MB in the presence of lipid bilayer membrane.

Toxic Mastoparan B(MP-B) which is purified from the venom of the hornet Vespa basalis is a cationic amphiphilic tetradecapeptide. MP-B and its Ala-substituted analogues were synthesized by solid phase method and the toxic peptide-membrane interactions were examined by circular dichroism(CD) spectra, fluorescence spectra, and leakage abilities in phospholipid membranes. In the presence of phospholipid vesicles, synthetic MP-B and its analogues formed amphiphilic α-helical structures, but in the buffer solution, those exhibited random coil conformation as measured by CD. Fluorescence spectra of MP-13 and its analogues which indicated the binding affinity of peptide on phospholipid vesicles showed that the replacement of Lys at position 2 and 11 with Ala caused a remarkable effect in the blue shift and that at position 2, in the leakage ability of the peptide.