Effects of Interfacial Interactions on Electrocatalytic Activity of Cytochrome c Oxidase in Biomimetic Lipid Membranes on Gold Electrodes

Abstract

Effects of interfacial interactions on the electrocatalytic activity of protein-tethered bilayer lipid membranes (ptBLMs) containing cytochrome c oxidase (CcO) for the oxygen reduction reaction are studied by using protein film electrochemistry and surface-enhanced infrared absorption (SEIRA) spectroscopy. Mammalian CcO was immobilized on a gold electrode via self-assembled monolayers (SAMs) of mixed alkanethiols. The protein orientation on the electrode is controlled by SAM–CcO interactions and is critical to the cytochrome c (cyt c) binding. The CcO–phospholipid and CcO–cyt c interactions modulate the electrocatalytic activity of CcO, and more densely packed ptBLMs show higher electrocatalytic activity. Our study indicates that spectroscopic and electrochemical studies of ptBLMs can provide insights into the effects of relatively weak protein–protein and protein–lipid interactions on the enzymatic activity of transmembrane enzymes.

Metal Ion-Linked Molecular Multilayers on Inorganic Substrates: Structure and Applications

“…Nearly a century of theoretical and experimental work has underscored the importance of distance and orientation on intermolecular communication and its impact on photoinduced events like energy and electron transfer. , Its importance is arguably best exemplified in photosynthetic systems, where millions of years of evolution have optimized the structure of supramolecular assemblies to funnel excited states and redox equivalents to specific reaction centers. , Progress has also been made on human generated assemblies that control molecular orientation and proximity via molecular crystals, covalent and metal organic frameworks, phospholipid bilayers, polymers, and more. − Self-assembly via metal ion-linked multilayers is a particularly appealing strategy because of their ease of preparation, versatility in component selection/design, and control over structure, and they are assembled on an inorganic substrate which is useful in hybrid electronics, heterogeneous catalysis, sensing, and more. − The multilayers are prepared via a stepwise loading procedure (Figure a) where an inorganic substrate is first soaked in a solution containing a molecule having a surface binding motif and a geometrically opposed metal binding group (e.g., COOH, PO 3 H 2 ). The monolayer films are then submerged in a solution containing a metal-linking ion (typically Zn 2+ or Zr 4+ ) followed by a second molecule (either the same or different), and so on .…”