Aleksandr M. Kuznetsov

Bio: Aleksandr M. Kuznetsov is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Electron transfer & Adiabatic process. The author has an hindex of 19, co-authored 79 publications receiving 1647 citations.

Electron Transfer in Chemistry and Biology: An Introduction to the Theory

Abstract: Some Theoretical Prerequisites. The Tunnel Effect in Physical, Chemical and Biological Processes. Elements of Dielectric Theory. Charge Transfer in Solids. The Simplest Chemical Process: Electron Transfer. Some Selected Experimental Data for Simple Electron Transfer Reactions. Towards More Precise Electron Transfer Theory. Optical Charge Transfer in Allowed and Forbidden Transitions. Elements of Proton and Other Light-Atom Transfer Theory. The Electrochemical Process. Elements of Long-Range and Multi-Level Electron Transfer. Stochastic Views in Chemical Rate Theory. Elements of Charge Transfer in Biological Systems. Perspectives and Outlook. Appendices. Index.

Proton and hydrogen atom tunnelling in hydrolytic and redox enzyme catalysis

Abstract: We discuss a broad theoretical frame for hydrogen transfer in chemical and biological systems Hydrogen tunnelling, coupling between the tunnel modes and the environment, and fluctuational barrier preparation for hydrogen tunnelling are in focus and given precise analytical forms Specific rate constants are provided for three limits, ie, the fully diabatic, the partially adiabatic, and the fully adiabatic limits These limits are all likely to represent real chemical or biological hydrogen transfer systems The rate constants are referred particularly to the driving force and temperature dependence of the kinetic isotope effect (KIE) The origin of these correlations is different in the three limits It is rooted in the tunnel factor and weak excitation of the heavier isotopes in the former two limits, giving a maximum for thermoneutral processes A new observation is that the adiabatic limit also accords with a KIE maximum for thermoneutral processes but the KIE is here reflected solely in the activation Gibbs free energy differences, in this case rooted in the low-frequency environmental nuclear dynamics Three systems of biological hydrogen tunnelling, viz lipoxygenase, yeast alcohol dehydrogenase, and bovine serum amine oxygenase, offer unusual new cases for analysis and have been analysed using the theoretical frames All the systems show large KIEs and strong indications of hydrogen tunnelling They also represent different degrees of fluctuational barrier preparation, with lipoxygenase as the most rigid and bovine serum amine oxygenase as the softest system

Theory of hydrogen-ion discharge on metals: Case of high overvoltages

Abstract: A detailed quantum-mechanical theory for hydrogen discharge on metals showing high hydrogen overvoltage is given, for the case where the discharge reaction is the rate-determining step.

Resonance and Environmental Fluctuation Effects in STM Currents through Large Adsorbed Molecules

Abstract: Scanning tunnelling microscopy (STM) involving electron tunnelling through large adsorbate molecules with discrete electronic levels accessible at low bias voltage, exhibits conceptual and physical analogies to other thermal and optical multi-level electronic processes. The analogies are most conspicuous if the adsorbate levels are strongly coupled to the environmental molecular, conformational or solvent nuclear motion but interact weakly with the conducting substrate and tip. These conditions would be appropriate for example for adsorbed large transition metal complexes or redox metalloproteins. In these limits electronic-vibrational coupling induces resonance between the local adsorbate level and either the substrate or the tip levels, and the STM current-voltage relations can be approached by methods known from the theory of related electronic transitions such as long-range molecular electron transfer and multi-photon optical processes. We provide a new theoretical frame for STM processes in this limit. The formalism rests on perturbative coupling of the adsorbate levels to the substrate and tip. Specific models incorporate strong coupling to the adsorbate and environmental nuclear motion, vibrational relaxation features, and the continuous electronic spectra of the substrate and tip. All these features are directly and transparently reflected in the current-voltage relations of the STM process.

The present state of the theory of charge transfer processes in condensed phase

Abstract: The main results obtained during the last 5 yr in the quantum-mechanical theory of the reaction elementary act in solutions are summarized. The method of qualitative and quantitative analysis of experimental data is presented. The electron transfer reactions and ligand substitution reactions are considered as a example of the application of the general method. The perspectives of the theory development and the main problems of the theory are discussed.

Electron transfers in chemistry and biology

Abstract: Electron-transfer reactions between ions and molecules in solution have been the subject of considerable experimental study during the past three decades. Experimental results have also been obtained on related phenomena, such as reactions between ions or molecules and electrodes, charge-transfer spectra, photoelectric emission spectra of ionic solutions, chemiluminescent electron transfers, electron transfer through frozen media, and electron transfer through thin hydrocarbon-like films on electrodes.

Reaction-rate theory: fifty years after Kramers

Abstract: The calculation of rate coefficients is a discipline of nonlinear science of importance to much of physics, chemistry, engineering, and biology. Fifty years after Kramers' seminal paper on thermally activated barrier crossing, the authors report, extend, and interpret much of our current understanding relating to theories of noise-activated escape, for which many of the notable contributions are originating from the communities both of physics and of physical chemistry. Theoretical as well as numerical approaches are discussed for single- and many-dimensional metastable systems (including fields) in gases and condensed phases. The role of many-dimensional transition-state theory is contrasted with Kramers' reaction-rate theory for moderate-to-strong friction; the authors emphasize the physical situation and the close connection between unimolecular rate theory and Kramers' work for weakly damped systems. The rate theory accounting for memory friction is presented, together with a unifying theoretical approach which covers the whole regime of weak-to-moderate-to-strong friction on the same basis (turnover theory). The peculiarities of noise-activated escape in a variety of physically different metastable potential configurations is elucidated in terms of the mean-first-passage-time technique. Moreover, the role and the complexity of escape in driven systems exhibiting possibly multiple, metastable stationary nonequilibrium states is identified. At lower temperatures, quantum tunneling effects start to dominate the rate mechanism. The early quantum approaches as well as the latest quantum versions of Kramers' theory are discussed, thereby providing a description of dissipative escape events at all temperatures. In addition, an attempt is made to discuss prominent experimental work as it relates to Kramers' reaction-rate theory and to indicate the most important areas for future research in theory and experiment.

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Temperature dependent activation energy for electron transfer between biological molecules

Abstract: This paper considers electron transfer between biological molecules in terms of a nonadiabatic multiphonon nonradiative decay process in a dense medium. This theoretical approach is analogous to an extended quantum mechanical theory of outer sphere electron transfer processes, incorporating the effects of both low‐frequency medium phonon modes and the high‐frequency molecular modes. An explicit, compact and useful expression for the electron transfer probability is derived, which is valid throughout the entire temperature range, exhibiting a continuous transition from temperature independent tunneling between nuclear potential surfaces at low temperatures to an activated rate expression at high temperatures. This result drastically differs at low temperatures from the common, semiclassical, Gaussian approximation for the transition probability. The experimental data of De Vault and Chance [Biophys. J. 6, 825 (1966)] on the temperature dependence of the rate of electron transfer from cytochrome to the chlorophyll reaction center in the photosynthetic bacterium Chromatium are properly accounted for in terms of the present theory.

Electron transport in molecular junctions.

Abstract: Building an electronic device using individual molecules is one of the ultimate goals in nanotechnology. To achieve this it will be necessary to measure, control and understand electron transport through molecules attached to electrodes. Substantial progress has been made over the past decade and we present here an overview of some of the recent advances. Topics covered include molecular wires, two-terminal switches and diodes, three-terminal transistor-like devices and hybrid devices that use various different signals (light, magnetic fields, and chemical and mechanical signals) to control electron transport in molecules. We also discuss further issues, including molecule-electrode contacts, local heating- and current-induced instabilities, stochastic fluctuations and the development of characterization tools.