Label-Free Surface-Enhanced Infrared Spectroelectrochemistry Studies the Interaction of Cytochrome c with Cardiolipin-Containing Membranes

Interactions of cytochrome c (cyt c) with cardiolipin (CL)-containing membranes have been revealed to play an important role in inducing early apoptosis. In this paper, we studied the interaction of cyt c with solid-supported CL-containing lipid bilayers by a lable-free spectroelectrochemistry method. The biomimetic membrane was fabricated by fusing cardiolipin-phosphatidylcholine (CL_PC, 1:4) vesicles onto the hydrophobic surface of a preadsorbed 1-dodecanethiol (DT) on a gold electrode (CL_PC/DT/Au). The adsorption of cyt c onto the CL_PC/DT/Au was in-situ studied by cyclic voltammetry (CV) and surface-enhanced Infrared adsorption spectroscopy (SEIRAS). The electrochemistry of Cyt c/CL_PC/DT/Au exhibits the formal potential (E-f) at 0.21 V (vs Ag/AgCl), a positive shift of 190 mV as compared to that of native cyt c adsorbed at the mercaptoundecanoic acid-modified gold electrode (Cyt c/MUA/Au). The potential-induced SEIRA difference spectroscopy discloses that cyt c was loosely adsorbed onto CL_PC/DT/Au in a different orientation and underwent a new beta-sheet formation relative to native cyt c adsorbed onto MUA/Au. It could be the enhanced hydration change of CL-bound cyt c upon oxidization and reduction and the different adsorption orientation that determine the positive shift in its formal potential