Electrostatic models of electron-driven proton transfer across a lipid membrane

Abstract

We present two models for electron-driven uphill proton transport across lipid membranes, with the electron energy converted to the proton gradient via the electrostatic interaction. In the first model, associated with the cytochrome c oxidase complex in the inner mitochondria membranes, the electrostatic coupling to the site occupied by an electron lowers the energy level of the protonbinding site, making the proton transfer possible. In the second model, roughly describing the redox loop in a nitrate respiration of E. coli bacteria, an electron displaces a proton from the negative side of the membrane to a shuttle, which subsequently diffuses across the membrane and unloads the proton to its positive side. We show that both models can be described by the same approach, which can be significantly simplified if the system is separated into several clusters, with strong Coulomb interaction inside each cluster and weak transfer couplings between them. We derive and solve the equations of motion for the electron and proton creation/annihilation operators, taking into account the appropriate Coulomb terms, tunnel couplings, and the interaction with the environment. For the second model, these equations of motion are solved jointly with a Langevintype equation for the shuttle position. We obtain expressions for the electron and proton currents and determine their dependence on the electron and proton voltage build-ups, on-site charging energies, reorganization energies, temperature, and other system parameters. We show that the quantum yield in our models can be up to 100% and the power-conversion efficiency can reach 35%.

Simultaneous Study of Anti-Ferroptosis and Antioxidant Mechanisms of Butein and (S)-Butin

“…As shown in Supplementary Materials S1, the two isomers increased the LPO inhibition percentages with increasing concentration. Both the inhibition and formation of LPO are reported to stem from electron-transfer (ET) reactions [37][38][39][40][41]. To explore ET, the two were further investigated using the Fe 3+ -reducing antioxidant power (FRAP) assay and Cu 2+ -reducing antioxidant power (CUPRAC) assay.…”

From classical to quantum and back: Hamiltonian adaptive resolution path integral, ring polymer, and centroid molecular dynamics

“…This can be the case, for example, in biomolecular systems, in which the study of nuclear quantum effects has gained significant interest [6][7][8][9][10][11][12][13][16][17][18][19][20][21]98 . way.…”

Optimal efficiency of the Q-cycle mechanism around physiological temperatures from an open quantum systems approach

“…Following a similar approach, we hereby focus on the electron transport chain, which represents the second stage of the photosynthetic machinery, immediately connected to the primary light-absorbing processes. Several early applications of open quantum systems (OQS) theory to such crucial particle and charge transport processes at the molecular level are known in the literature 11–18 , including investigations of coherence 11 , correlations 15 and non-Markovian effects 14 . Building on an OQS-based kinetic model originally proposed by Smirnov and Nori 17 , here we develop a simple but accurate Markovian theory of the Q-cycle.…”