(201i) The Influence of the Electrochemical Interface on Protein Structure and Function

Proteins engage with solid surfaces to spontaneously create intrinsic electric fields at the protein-solid interface which results in their electrical polarization. The influence of this electrochemical interface on protein properties such as structure and function, plays a significant role in pharmaceuticals, bioelectrochemistry, and biomedical applications. In pharmaceuticals, for instance, drug delivery systems often involve nanoparticles or solid carriers to encapsulate and protect therapeutic proteins or drugs. The electrochemical interface between proteins and the solid surface can affect the stability and conformation of the protein, which, in turn, influences drug release kinetics and bioavailability. The electrochemical interface also greatly influences the performance of an enzyme electrode by modulating electron transfer between the enzyme and electrode while also affecting enzyme orientation. The influence of the electrochemical interface on protein properties is further complicated by the accompanying salt and pH gradients due to the strong electric field. Understanding the influence of electrochemical interface on protein properties would provide foundational understanding needed to ultimately tailor protein-surface interactions.

Here, we investigated the significance of the electrochemical interface on protein structure and function using surface-sensitive spectroscopy and cryogenic electron microscopy. The outer membrane protein from a models bacterium Shewanella oneidensis which was capable of transfer electrons toward/from electrodes was chosen as the target protein. We studied protein behavior under different electrochemical conditions by fixing potentials with redox buffers. This deconvoluted the effects of potential from other factors such as pH gradients and electrolyte salts. By leveraging surface-sensitive spectroscopy and cryogenic electron microscopy, our investigations provided new insights into protein structure-function relationship at electrochemical interfaces, allowing for the design of innovative surface modifications, enzyme electrodes and bio-electrochemical systems. More importantly, the developed methodology combining potential pinning, in situ spectroscopy and cryogenic microscopy can be applied to other electrochemical systems, such as Li batteries, H₂ evolution reaction, CO₂ and N₂ electroreduction, and fuel cells, allowing for the investigation of the electrochemical interfaces involved in these systems.