Photoinduced Reduction of Methylviologen by Ascorbate Using Chlorophyllin in Liposome System

Article abstract of DOI:10.1246/bcsj.58.207

Photoinduced electron transport across bilayer lipid membrane was studied, using chlorophyllin (Chln), a water-soluble derivative of chlorophyll.Photoreduction of methylviologen (MV2+) by ascorbate was observed only in the liposome system containing ascorbate in the internal aqueous phase and MV2+ in the external aqueous phase.This suggests asymetry of bilayer lipid membrane.This reaction rate was not affected by the addition of carbonyl cyanide m-chlorophenylhydrazone in the system buffered by tris(hydroxymethyl)aminomethane (Tris), but strongly affected by N-2-hydro xyethylpiperazine-N'-2-ethanesulfonic acid.In the system buffered by Tris, a proton carried is not Chln having carboxyl groups but Tris possesing primary amine group.Replacement of the central Mg of Chln with Zn gives higher rate of MV2+ photoreduction, but when Cu was used in place of Zn, photoreduction was not observed.The central metal may affect the redox potential and the life time of exited Chln.