Molecular Simulations of Cytochrome c Adsorption on a Bare Gold Surface: Insights for the Hindrance of Electron Transfer

Experimental studies have shown that the adsorption of horse heart cytochrome c (Cyt- c ) on a bare gold surface leads to the hindrance of electron transfer (ET). The underlying mechanism remains controversial. In this work, the adsorption orientation and conformation of Cyt- c on Au(111) surface were investigated by performing Monte Carlo and molecular dynamics simulations. The results show that the most favorable binding mode of Cyt- c to gold agrees with the results characterized by SEIRA spectroscopy. The adsorption is mainly contributed by the strong van der Waals interactions between the surface and residues that have long side chains, which leads to the helix A and Ω1 loop of Cyt- c being in contact with the surface and most of the α-helixes being nearly parallel to the surface. The native structure of Cyt- c is well preserved during the adsorption, and only the flexible Ω1 loop and the N-terminal show a relatively larger mobility. The hindrance of ET is ascribed to the confined rotation of the heme prosthetic group and the farther positioning of the central iron to the surface (about 12.9 Å).