Bioelectrochemistry as a Field of Analysis: Historical Aspects and Current Status

Journal of Analytical Chemistry - The review considers the historical aspects of the formation and development of bioelectrochemistry and some issues of the analytical application of...     

On the influence of structural features of DNA on the possibility of metabolic transfer of electrons

Abstract

A fragment of a DNA molecule is considered as one of the channels of metabolic electron transfer. The heterogeneity of the complementary chains is effectively taken into account. This made it possible to find the speed of the electron injected into the DNA conduction band and the current density that it creates. Estimates of electron mobility in nucleic acid chains are made. They were an order of magnitude smaller than that of typical semiconductors. For the specific conductivity of nucleic acid chains, estimates provide a conductivity of one to two orders of magnitude lower than in graphite.     

Electrochemical oxidation of thrombin on carbon screen printed electrodes

The electrochemical oxidation of thrombin on the surface of carbon screen printed electrodes was studied. The electrochemical activity of thrombin was predicted, using bioinformation analysis, based on the data about the electrochemical properties of amino acids. The number of potentially electroactive amino acid residues, namely, tyrosine (Tyr), tryptophan (Trp), cysteine (Cys), histidine (His), methionine (Met), and cystine (Cys-Cys) located on the protein surface and orientated by their electroactive groups toward the electrode surface, i.e., accessible for electrochemical oxidation was calculated. The theoretical data were confirmed experimentally by cyclic and square-wave voltammetry. The available data on the protein structure allowed us to attribute the recorded electrochemical signals of thrombin oxidation to certain types of amino acid residue: the oxidation peak with a potential maximum at 0.7–0.8 V (vs. Ag/AgCl) was attributed to the oxidation of the Trp and Tyr residues; the wave in the range 1.0–1.2 V, to the oxidation of His; and the wave at 1.2–1.5 V, to the oxidation of Met and Cys-Cys. The electroanalysis based on the oxidation peak of the Tyr and Trp amino acid residues allowed to detect thrombin up to the concentration of 10^–7 M. The suggested strategy for predicting the electrochemical activity can be used for investigating the properties of many other proteins and peptides and serve as a basis for their quantitative determination when developing various sensor and biosensor devices.     

(CuO-CeO2)/glass cloth catalysts for selective CO oxidation in the presence of H2: The effect of the nature of the fuel component used in their surface self-propagating high-temperature synthesis on their properties

The potential of surface self-propagating high-temperature synthesis (SSHS) for obtaining (CuO-CeO₂)/glass cloth catalysts is demonstrated. The dependence of the structural and catalytic properties of the catalysts on their preparation conditions (nature of the fuel component) is considered. X-ray diffraction, electron microscopy, and EXAFS data suggest that the short-term action of high temperature in the SSHS leads to the complete decomposition of the precursors and has an effect on the distribution of the resulting phases. According to H₂ TPR and XPS data, the degree of dispersion of CuO and the electronic state of the reacting CuO and CeO₂ phases depend on the choice of fuel. This is likely due to fuels varying in the amount of heat released in their combustion. The degree of dispersion of CuO and the total contribution from Cu¹⁺ and Ce⁴⁺ to the electronic state of the active component increase as the standard enthalpy of combustion increases in the urea < glycerol < citric acid order. This leads to an increase in the catalytic activity of the (CuO-CeO₂)/glass cloth system in selective CO oxidation.     

Modification of the Surface Properties of PbSnTe〈In〉 Epitaxial Layers with Composition near Band Inversion

Technical Physics - High-resistance Pb1 –xSnxTe〈In〉 layers grown by molecular beam epitaxy on BaF2(111) substrates with compositions close to band inversion have been...     

Dislocation detachment from weak attachment points

Detachment of dislocations from weak attachment points under the action of a periodic external stress is considered with defect diffusion along dislocations being possible. The expression obtained for the probability of detachment is studied numerically for various amplitudes and durations of the external stress at various concentrations and strengths of the attachment points. Attachment point diffusion increases the probability of detachment, while as the interaction between the dislocation and the point defect increases, the influence of that phenomenon increases as well. Change in the probability of detachment during the excitation process should lead to time dependence of hysteresis-type dislocation internal friction.Translated from Izvestiya Vysshikh Uchebnykh Zavednii, Fizika, No. 5, pp. 24–28, May, 1989.     

Catalytic Etching of Platinoid Gauzes during the Oxidation of Ammonia by Air. Reconstruction of Surface of Platinoid Gauzes at 1133 K in Air,in Ammonia,and in an NH<Subscript>3</Subscript> + O<Subscript>2</Subscript> Reaction Medium

The structure, morphology, and chemical composition of the surface and near-surface layers of platinoid wires of polycrystalline gauzes, containing Pt (81 wt %), Pd (15 wt %), Rh (3.5 wt %), and Ru (0.5 wt %) after treatment at 1133 K in various media—in air, in ammonia, and after NH3 oxidation in air—are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS). A thin film is found on the surface of the initial gauze containing an oxide layer of Rh₂O₃ with a thickness of ~2 nm, on the surface of which an inhomogeneous graphite-like layer 10–50 nm thick is located. It is shown that the heat treatment of gauzes in air leads to the partial removal of the surface graphite-like film that forms the reticulated structure on the wire surface. The treatment of gauzes in an ammonia atmosphere leads to the complete removal of the graphite-like and oxide layers and to the growth of metal grains of ~10 μm. After the catalytic reaction of NH3 oxidation, a deep structural rearrangement of the surface layer of the wire takes place, as a result of which crystalline metal agglomerates of ~10 μm are formed. It is supposed that the reaction of NH3 molecules with oxygen atoms penetrated on the defects leads to the local increase of temperature, due to which the metal atoms emerge on the surface and form large crystalline agglomerates and pores in the region of the grain boundaries.     

Quantitative Aspects of Electrochemical Detection of Amyloid‐β Aggregation

The tyrosine based electrochemical analysis of synthetic amyloid‐β (Aβ) peptide – an analog of natural peptide implicated in Alzheimer's disease pathogenesis – was applied for a quantitative estimation of peptide aggregation in vitro. The analysis was carried out by square wave voltammetry (SWV) on carbon screen printed electrodes (SPE). The electrooxidation peak current (I_p) for Aβ42 peptide in different aggregation states was directly compared with the size and structure of Aβ42 aggregates occurring in the analyzed sample. Dynamic light scattering (DLS) and thioflavin T (ThT) based fluorescence assay were employed to estimate the size and structure of Aβ42 aggregates. The I_p was found to decrease in a linear fashion when the average diameter of aggregates and the relative ThT fluorescence in Aβ42 solutions exceeded 35 nm and 3, respectively, while being nearly constant below these values. It was suggested that the electrooxidation current is mostly generated by peptide monomers and that a depletion of the monomer pool due to inclusion of Aβ42 molecules in aggregates is responsible for the decrease of electrooxidation current. The direct electrochemistry is emerging as a method complementary to methods based on aggregates’ detection and commonly employed for monitoring Aβ aggregation. The work further enlarges the basis for application of the cost‐effective and rapid electrochemical techniques, such as SWV on carbon SPE, to in vitro studies of Aβ aggregation.