Theoretical aspects of several successive two-step redox mechanisms in protein-film cyclic staircase voltammetry

Protein-film voltammetry (PFV) is a versatile tool designed to provide insight into the enzymes physiological functions by studying the redox properties of various oxido-reductases with suitable voltammetric technique. The determination of the thermodynamic and kinetic parameters relevant to protein’s physiological properties is achieved via methodologies established from theoretical considerations of various mechanisms in PFV. So far, the majority of the mathematical models in PFV have been developed for redox proteins undergoing a single-step electron transfer reactions. However, there are many oxido-reductases containing quinone moieties or polyvalent ions of transition metals like Mo, Mn, W, Fe or Co as redox centers, whose redox chemistry can be described only via mathematical models considering successive two-step electron transformation. In this work we consider theoretically the protein-film redox mechanisms of the EE (Electrochemical–Electrochemical), ECE (Electrochemical–Chemical–Electrochemical), and EECat (Electrochemical–Electrochemical–Catalytic) systems under conditions of cyclic staircase voltammetry. We also propose methodologies to determine the kinetics of electron transfer steps by all considered mechanisms. The experimentalists working with PFV can get large benefits from the simulated voltammograms given in this work

Multistep Surface Electrode Mechanism Coupled with Preceding Chemical Reaction-Theoretical Analysis in Square-Wave Voltammetry

In this theoretical work, we present for the first time voltammetric results of a surface multistep electron transfer mechanism that is associated with a preceding chemical reaction that is linked to the first electron transfer step. The mathematical model of this so-called “surface CEE mechanism” is solved under conditions of square-wave voltammetry. We present relevant set of results portraying the influence of kinetics and thermodynamics of chemical step to the features of simulated voltammograms. In respect to the potential difference at which both electrode processes occur, we consider two different situations. In the first scenario, both peaks are separated for at least |150 mV|, while in the second case both peaks occur at same potential. Under conditions when both peaks are separated for at least |150 mV|, the first process can be described with the voltammetric features of a surface CE mechanism, while the second peak gets attributes of a simple surface electrode reaction. When both peaks take place at same potential, we elaborate an elegant methodology to achieve separation of both overlapped peaks. This can be done by modifying the concentration of the substrate “Y” in electrochemical cell that is involved in the preceding chemical reaction. The results of this work can be of big assistance to experimentalists working in the field of voltammetry of metal complexes and drug-drug interaction

Analysis of Drug-Drug Interactions with Cyclic Voltammetry: An Overview of Relevant Theoretical Models and Recent Experimental Achievements

In this review, we focus on cyclic voltammetry as a reliable electrochemical technique to study mechanisms, kinetics and thermodynamics of various types of drug-drug interactions. While we present and discuss six theoretical models relevant to analyze drug-drug (or drug-DNA) interactions, we also give hints about recent experimental achievements in this field. In addition, we provide the readers several sets of simulated voltammograms and data in tabular form, which can be used to recognize particular mechanism of drug-drug interactions in cyclic voltammetry. Moreover, we give hints to the voltammetric procedures that allow access to kinetics and thermodynamics parameters, which are relevant to various types of drug-drug interactions. The results we present in this work can be of big help to the scientists working in the field of pharmacy, pharmacology, medicinal chemistry and bio-electrochemistry

Multistep Surface Electrode Mechanism Coupled with Preceding Chemical Reaction-Theoretical Analysis in Square-Wave Voltammetry

In this theoretical work, we present for the first time voltammetric results of a surface multistep electron transfer mechanism that is associated with a preceding chemical reaction that is linked to the first electron transfer step. The mathematical model of this so-called “surface CEE mechanism” is solved under conditions of square-wave voltammetry. We present relevant set of results portraying the influence of kinetics and thermodynamics of chemical step to the features of simulated voltammograms. In respect to the potential difference at which both electrode processes occur, we consider two different situations. In the first scenario, both peaks are separated for at least |150 mV|, while in the second case both peaks occur at same potential. Under conditions when both peaks are separated for at least |150 mV|, the first process can be described with the voltammetric features of a surface CE mechanism, while the second peak gets attributes of a simple surface electrode reaction. When both peaks take place at same potential, we elaborate an elegant methodology to achieve separation of both overlapped peaks. This can be done by modifying the concentration of the substrate “Y” in electrochemical cell that is involved in the preceding chemical reaction. The results of this work can be of big assistance to experimentalists working in the field of voltammetry of metal complexes and drug-drug interaction

Two-Step Protein-Film Voltammetry Associated with Intermediate Reversible Chemical Reaction-Diagnostic Criteria for Characterizing Systems with Inverted Potentials in Square-Wave Voltammetry

Many electron transfer mechanisms of important physiological systems commonly occur as multistep electrode reactions that are initiated by a gain or loss of an electron. The product of initial electrochemical reaction might subsequently participate in chemical and/or electrochemical reaction(s), in which the final product of entire mechanism is generated. Therefore, a proper understanding of electron transfer phenomena is of outmost importance to get information about mechanism going on in the redox transformation of relevant physiological systems. In this work, we focus on theoretical voltammetric features of complex multielectron surface electrode mechanisms, in which two electron transfer steps are bridged by a reversible chemical reaction. Special attention is paid to systems with so-called “inverted potentials”, in which the second electron transfer requires less energy to occur than the first one. Square-wave voltammetry (SWV) of so-called “surface ECrevE mechanism” is explored as a valuable technique that can give relevant information about diagnostics of this mechanism. The presented model is suitable to study the activity of various enzymes and lipophilic organic compounds by exploring the “protein-film voltammetry” scenario

Surface Electrode Mechanism Associated with Preceding and Follow up Chemical Reactions – Theoretical Analysis in Square-Wave Voltammetry

Surface electrode reaction (E), coupled with reversible preceding and reversible follow up chemical steps (C), or so-called “surface CEC mechanism” is considered theoretically under conditions of square-wave voltammetry. Large set of square-wave voltammograms of considered electrode system are calculated as a function of thermodynamics and kinetics of chemical steps involved in this complex mechanism. The surface CEC mechanism can be simplified to a surface CE, or a surface EC mechanism, if one assumes defined magnitudes of the equilibrium constants of chemical steps involved. Although the influence of the square-wave frequency to the voltammetric patterns is quite complex, a frequency analysis can reveal important aspects to recognize this mechanism. While we present important differences that can distinguish between the effect of the kinetics of both chemical steps, we also give the readers hints on how to design experiments in order to get access to all relevant kinetic constants. Theoretical results elaborated in this work are quite important, since there are important experimental systems, such as redox enzymes and metal-ligand complexes, whose voltammetric behaviour fits to this mechanism. This work is licensed under a Creative Commons Attribution 4.0 International License

Theory of Square-wave Voltammetry of Two-step Surface Electrode Mechanisms Associated with Chemical Equilibria

Two-step electrode mechanisms that are associated with chemical equilibria are considered theoretically under conditions of square-wave voltammetry. The mechanisms designated as "surface EE", "surface ECE", "surface EECrev" and "surface EECatalytic" mechanisms are often encountered in experimental chemistry of many drugs and redox enzymes containing ions of transient metals as co-factors, or quinone-moieties, as well. We present large set of representative results that reveal specific features met at all considered mechanisms. We also propose set of simple methodologies to get access to kinetic and thermodynamic parameters relevant to electron transfer step, and to associated chemical reactions, as well. The work is of outmost importance to understand many aspects of enzyme-substrate interactions, but also the nature of drug-drug interactions of lipophilic and hydrophilic drugs

Хепатопротективна активност на растителни дроги

Лековитите растенија имаат значајна улога во здравствената заштита на луѓето. Голем процент од светската популација се потпира на употребата на традиционалната медицина што генерално се базира на хербални препарати. Црниот дроб е еден од најважните и најкомплексните органи во човековиот организам поради неговата специфична улога во метаболичките процеси во организмот. Притоа, најважната функција на црниот дроб е регулирање на биохемиските процеси и одржување на хомеостазата. Црнодробните заболувања се вбројуваат во групата на сериозни болести. Пронајдени се многу растенија чии фитоелементи покажале хепатопротективни карактеристики. Со помош на голем број експериментални истражувања, потврдено е хепатопротективното дејство на растенијата како Silybum marianum, Curcuma longa, Picorhiza kurroa, Phyllantus amarus, Glychyrriz glabra, Berberis vulgaris и др., при различни механизми на делување. Нивниот наизјразен ефект е нивното релативно силно антиоксидативното дејство. Многу често, едно растение не ги покажува сите посакувани дејства што сакаме да ги постигнеме во фитотерапевтскиот пристап на третманот и во тој случај е потребна комбинација на повеќе хербални екстракти или фракции за постигнување на саканиот резултат. Развојот на хербалните лекови со високи стандарди за безбедност и ефикасност може да го ревитализира и унапреди третманот кај црнодробните нарушувања и хепатопротективната ефикасност. Целта на ова истражување е да се направи преглед на најчестите хепатални заболувања кои се јавуваат како резултат на дисфункција на црниот дроб и намалување на оштетувањето предизвикано од хепатални стрес фактори и различни заболувања во организмот, со примена на соодветните фитотерапевтски пристапи кон нивно лекување, користејќи хербални дроги од соодветни растенија

Direct Voltammetry in Human Blood Serum

This presentation focuses on direct voltammetric measurements in human blood serum. By application of fast and sensitive voltammetric technique, as it is the square-wave voltammetry, it is possible to make a simultaneous detection and quantification of important physiological systems. We give in this presentation the basic concepts in designing a simple voltammetric sensor able to detect several compounds in human serum

Scanning Electrochemical Microscopy-Basic Principles and Application

Scanning Electrochemical Microscopy (SECM) is an electrochemical�microscopic technique that is designed to get simultaneous insight into the local electrochemical activity and in topography of different redox systems. In this work, we present the basic principles of SECM, while we also shortly elaborate the instrumentation used in this technique. The basic principles of SECM that allow this technique to be applied in qualitative and quantitative analysis are also discussed. In this work, we also elaborate some of important applications of SECM for quantification of biomolecules in experiments with cells. We also discuss some of the problems met in this technique, mainly problems with pollution of working electrodes and problem with interferences. Alongside, we discuss application of SECM for quantification of important biomolecules, such as oxygen, hydrogen peroxide, glucose, DNA and RNA