Label-free surface-enhanced infrared spectro-electro-chemical analysis of the Redox potential shift of cytochrome c complexed with a cardiolipin-containing lipid membrane of varied composition

摘要

In this study, a lipid membrane was fabricated by fusing cardiolipin-phosphatidylcholine(CL PC, 1:4) vesicles onto a hydrophobic surface of 1-dodecanethiol(DT) preadsorbed on a nanostructured gold film. By changing the concentration of the DT adsorption solution, we constructed a series of CL PC-DT bilayers with different hydrophobicity to study the effects of lipid membrane characteristics on the adsorption conformation of cytochrome c(Cyt c). Electrochemical analysis showed that the formal potential is 0.24 V for Cyt c-CL PC-DT(10), 0.2 V for Cyt c-CL PC-DT(20), and 0.16 V for Cyt c-CL PC-DT(40) — a gradual positive shift with the decreasing DT concentration — relative to the potential of native cyt c(0.02 V). Potential-induced surface-enhanced infrared adsorption difference spectroscopy revealed that the gradual positive shift of the formal potential of CL-bound cyt c is determined by the environment with the gradually lowered dielectric constant for the heme cofactor in CL-bound cyt c(Fe3+).