Manganese Porphyrin-Mediated Electron Transfer across a Liposomal Membrane and on an Electrode Modified with a Lipid Bilayer Membrane

Phospholipid-linked mesoporphyrins separated by spacer methylene groups (C n ), PE-C n -MnMPMME ( n = 0, 5, 11) (Chart 1) were synthesized. Manganese porphyrin-mediated electron transfers across a liposomal membrane and on a glassy carbon (GC) electrode covered with a phospholipid bilayer membrane were examined to provide insight into the effect of the structure of porphyrins on these electron transfers between porphyrins in lipid bilayers. Enhanced transmembrane electron transfers catalyzed by phospholipid-linked manganese porphyrin derivatives separated by spacer methylene groups (C n )( n = 0, 5, 11) (Chart 1) were observed in a liposomal membrane only above the phase temperature of the membrane, depending on the length of the C n and on the structure of the porphyrins. Furthermore, cyclic voltammetry on a SnO 2 glass electrode or on a GC electrode modified with a DPPC membrane containing manganese porphyrins showed that one set of waves was clearly visible corresponding to the consecutive monoelectronic reduction of the manganese porphyrin unit (Mn(III)/Mn(II)) only above the phase temperature of the membrane. Phospholipid-linked manganese porphyrins on the electrode modified with a lipid bilayer membrane also caused enhanced electron transfers, depending on the length of the C n but not on the structure of the porphyrins. Comparison of manganese porphyrin-mediated electron transfers between porphyrins in a liposomal membrane and porphyrins on a GC electrode modified with a lipid bilayer membrane is made.