Oriented fixation of synthetic heme complexes in phospholipid bilayer membranes: Electrooptical measurement

Orientation of modified porphinatoiron (heme) complexes in a phospholipid bilayer was studied by electric birefringence and dichroism. The orientation angle (φ) between the heme plane and the phospholipid bilayer is close to zero for [5α,10α,15α,20α-tetrakis(o-(2,2-dimethyl-20-(((2- (trimethylammonio)ethyl)phosphonato)oxy)eicosanamido)phenyl)porphinato]iron (1) and [5α,10α,15α,20α-tetrakis(o-(2)2-dimethyl-20-(((2- carboxypropanyl)carbonyl)oxy)eicosanamido)-phenyl)porphinato]iron (2), while it is ca. 20-30° for [5α,10α,15α,20α-tetrakis(o-pivalamidophenyl)porphinato] iron (3). The stereostructure and the hydrophilic-hydrophobic balance of 1 and 2 are assumed to emphasize compatibility and orientation of the heme in the phospholipid bilayer. 2 is copolymerized with a polymerizable phospholipid (4) in a bilayer state and is covalently and orientedly fixed in the bilayer membrane.