Electrochemical potential biochemical reactions

Biochemical reactions are basically the same as other chemical organic reactions with their thermodynamic and mechanistic characteristics, but they have the enzyme stage. Laws of thermodynamics, standard energy status and standard free energy change, reduction-oxidation (redox) and electrochemical potential equations are applicable to these reactions. Enzymes catalyse reactions and induce them to be much faster . Enzymes are classified by international... 

A transducer is selected with respect to the features of the biochemical reaction. In amme-tering transducers, constant potential applied to the reference electrode and the current generated in the redox transformation of the electrochemically active compound present on the enzymatic electrode surface is measured. Electron transfer rate is controlled by increasing or reducing the potential drop between electrodes. 

Theory of Electrochemical MEMS Biosensors Potentiometric MEMS Biosensors Potentiometric MEMS biosensors are a direct analytical application of the Nemst equation through measurement of the potential of nonpolarized electrodes when current is zero. A reference electrode is necessary to investigate potential changes due to biochemical reactions. Without a stable reference electrode, reliability of the biosensor cannot be achieved [3]. 

Different lactate oxidising enzymes use different co-substrates and, therefore, a variety of electrochemical indicator reactions in biosensors can be utilised. Most of the lactate biosensors are based on enzymes like lactate oxidase (LOD) and lactate dehydrogenase (LDH). A needle-type lactate biosensor has been recently developed by Yang and coworkers who fabricated poly (1,3-phenylenediamine) electrodes immobilised with LOD for continuous intravascular lactate monitoring [185]. In the enzyme electrodes based on LDH, the biochemical reaction has been coupled to the electrode via NADH oxidation, either directly [119,123,163], or by using mediators [186] or additional enzymes [119]. This may lead to a shift of the unfavourable reaction equilibrium by partial trapping of the reduced cofactor. Direct oxidation of NADH requires potentials of more than 0.4 V ... 

Faraggi M, Klapper MH (1993) Reduction potentials determination of some biochemically important free radicals. Pulse radiolysis and electrochemical methods. J Chim Phys 90 711-744 Faraggi M, Klapper MH (1994) One electron oxidation of guanine and 2 -deoxyguanosine by the azide radical in alkaline solutions. J Chim Phys 91 1062-1069 Faraggi M, Broitman F, Trent JB, Klapper MH (1996) One-electron oxidation reactions of some purine and pyrimidine bases in aqueous solutions. Electrochemical and pulse radiolysis studies. J Phys Chem 100 14751-14761... 

According to the peak current, the concentrations of the reactant can be quantified when the diffusivity is negligible. The potential at which the peak current occurs can be used to identify the reaction. Based on the half-cell potential of the electrochemical reactions, the identification for reactions or reactants is listed extensively in handbooks and references. Amperometric sensors can be used very effectively to carry out qualitative and quantitative analyses of chemical and biochemical species. 

During the past few years interest in the electrochemical behaviour of biological molecules has been further stimulated by the quest for practical biosensors. These devices combine the inherent selectivity of a biochemical process, e.g., an enzyme reaction, with the advantages of measuring the analyte concentration in terms of a potential or current. 

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