Carbon nanotube-modified electrodes for electrochemical DNA-sensors

Glassy-carbon electrodes (GCEs) are modified with preoxidized multiwalled carbon nanotubes (CNTs). According to the data of atomic force microscopy, the layers of CNTs on GCEs possess a homogeneous nanostructurized surface. The voltammetric properties of a GCE/CNT depend on the modifier load. Guanine and deoxyguanosine monophosphate are strongly adsorbed on GCE/CNT and oxidized at +690 and +930 mV (pH 7.0), respectively. The oxidation current of guanine DNA nucleotides adsorbed on a GCE/CNT is significantly higher for the thermally denaturated biopolymer than for the native one. Our results are of interest for the development of sensors based on the electrochemical properties of nucleic acids.     

Epoxidation of Bicyclo[2.2.1]hept-5-ene-2,3-endo- and Exodicarboxylic Acid N-Arylimides

Epoxidation of endo- and exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid N-arylimides with a solution of peracetic acid in anhydrous dioxane affords 5,6-exo-epoxybicycloheptanedicarboxylic acid N-arylimides. The epoxidation reaction is not sensitive to the configuration of the imide fragment, to the character and position of the substituent in the aromatic ring. The reaction is determined only by oxidation conditions.     

Computer diagnostics of an optically dense plasma from absorption spectra

An algorithm is constructed for solving the problem of diagnostics of an optically dense plasma from the absorption spectra of isolated self-reversed spectral lines. The basic parameters taken are the width of the absorption line at the level 0.8J_o, where J_o is the intensity of the transmitted radiation, and the asymmetry of the absorption profile. The problem is solved by computer with the iteration method on the basis of the transverse pattern of the spectra. The radial variation of the concentration of absorbing atoms, of the electron concentration, and of the thin layer profile is determined. The method is applied to a low-voltage pulsed discharge, 2 msec in length, with a time resolution of 0.10 msec.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 11–16, July, 1981.     

Subwavelength-resolution near-field Raman spectroscopy

The resolution capabilities of near-field Raman spectroscopy based on a giant enhancement of the electric field near a nanosized metal probe are studied. As a test sample, bundles of single-walled carbon nanotubes deposited on glass substrates are used. It is shown that this method ensures a subwavelength spatial resolution of about 50 nm and demonstrates a Raman scattering enhancement of the order of 10⁴.     

Effect of size and protein environment on electrochemical properties of gold nanoparticles on carbon electrodes

We studied the electrochemical properties of gold nanoparticles (GNPs) and their complexes with proteins using square-wave voltammetry. Effect of the nanoparticle size and detection procedure was explored upon the oxidation of GNPs on a glassy carbon electrode (GCE). For pre-characterized GNPs of 13, 35 and 78 nm diameter, the oxidation peak potential was + 0.98, + 1.03 and + 1.06 V vs. Ag/AgCl, respectively. The conjugation of GNPs with four different proteins was verified by UV–Vis spectroscopy and atomic force microscopy indicated the formation of protein shells around GNPs. This process hampered the oxidation of GNPs on bare GCE causing pronounced decrease in the current response by an average factor of 72. GCE modification with carbon nanotubes weakly influenced the sensitivity of GNP detection but resulted in a 14.5-fold signal increase averaged for all GNP–protein complexes. The acidic dissolution and electrodeposition of GNPs or their complexes adsorbed on GCE allowed superior signal amplification directly proportional to nanoparticle size. The results are useful for the optimization of voltammetric analysis of GNP–protein complexes and can be extended to the characterization of other metal nanostructures and their complexes with biological components.     

Oxidative bromination of aniline and its derivatives

Oxidative bromination of aniline and its derivatives containing various substituents (CH₃, Cl, NO₂, COOH) in ortho, meta, and para positions with a brominating mixture of NaBr (KBr) and 20–22% hydrogen peroxide in 6–8% hydrochloric acid at the molar ratio aniline : NaBr (KBr) : H₂O₂ : HCl = 1 : 3.5 : 3.2 : 4.5 is described.     

An evolutionary particle swarm optimization algorithm for mathematical processing of experimental spectra

A particle swarm optimization algorithm is applied for mathematical treatment of Fourier-transform IR spectra of branched copolymers of methyl methacrylate. The efficiency of reconstruction of the spectra using the particle swarm optimization algorithm as compared with the least squares method is illustrated by the example of decomposition of a six-component experimental spectrum.     

Quartz crystal microbalance immunosensor for the detection of antibodies to double-stranded DNA

We report the development of a novel quartz crystal microbalance immunosensor with the simultaneous measurement of resonance frequency and motional resistance for the detection of antibodies to double-stranded DNA (dsDNA). The immobilization of poly(l-lysine) and subsequent complexation with DNA resulted in formation of a sensitive dsDNA-containing nanofilm on the surface of a gold electrode. Atomic force microscopy has been applied for the characterization of a poly(l-lysine)–DNA film. After the blocking with bovine serum albumin, the immunosensor in flow-injection mode was used to detect the antibodies to dsDNA in purified protein solutions of antibodies to dsDNA and to single-stranded DNA, monoclonal human immunoglobulin G, DNase I and in blood serum of patients with bronchial asthma and systemic lupus erythematosus. Experimental results indicate high sensitivity and selectivity of the immunosensor. In memoriam Prof. Victor G. Vinter     

Synthesis of Polypropylene in the Liquid Monomer in the Presence of a Titanium—Magnesium Catalyst: Effect of Various Internal Donors

Russian Journal of Applied Chemistry - The influence of supported titanium-magnesium catalysts with various internal and external donors on the propylene polymerization in the liquid monomer medium...