A. S. Chumakov

Ab initio electron propagator calculations of transverse conduction through DNA nucleotide bases in 1-nm nanopore corroborate third generation sequencing.

BACKGROUND The conduction properties of DNA molecule, particularly its transverse conductance (electron transfer through nucleotide bridges), represent a point of interest for DNA chemistry community, especially for DNA sequencing. However, there is no fully developed first-principles theory for molecular conductance and current that allows one to analyze the transverse flow of electrical charge through a nucleotide base. METHODS We theoretically investigate the transverse electron transport through all four DNA nucleotide bases by implementing an unbiased ab initio theoretical approach, namely, the electron propagator theory. RESULTS The electrical conductance and current through DNA nucleobases (guanine [G], cytosine [C], adenine [A] and thymine [T]) inserted into a model 1-nm Ag-Ag nanogap are calculated. The magnitudes of the calculated conductance and current are ordered in the following hierarchies: gA>gG>gC>gT and IG>IA>IT>IC correspondingly. The new distinguishing parameter for the nucleobase identification is proposed, namely, the onset bias magnitude. Nucleobases exhibit the following hierarchy with respect to this parameter: Vonset(A)<Vonset(T)<Vonset(G)<Vonset(C). CONCLUSIONS The difference in current magnitudes and onset voltages implies the possibility of nucleobases electrical identification by virtue of DNA translocation through an electrode-equipped nanopore. GENERAL SIGNIFICANCE The results represent interest for the theorists and practitioners in the field of third generation sequencing techniques as well as in the field of DNA chemistry.

Copper nanoparticles obtained by chemical reduction stabilized by micelles of various surfactants

We carried out the synthesis of copper nanoparticles via chemical reduction of micelles stabilized by various surfactants of different nature, such as cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTAB). We investigated the sustainability of the products of synthesis, i.e. copper nanoparticles stabilized by micelles of various surfactants, after the period of 50 days. Surface morphology and elemental composition of obtained copper nanoparticles were characterized by scanning electron microscopy (SEM).

The Formation of Quantum Dots - Liquid Crystal monolayers by Langmuir-Blodgett method

The article describes the features of the formation of CdSe/CdS/ZnS quantum dots - liquid crystal Langmuir monolayers on a water subphase surface by different temperature value. Monolayers structure was investigated by analyzing the compression isotherms and surface potential value. Films on the solid substrate (glass plates) were investigated by atomic force microscopy method for morphology, thickness and roughness. Film structure was studied as a function of the pressure at which the transfer was carried. It is shown that the structure of films obtained by a higher temperature of subphase is more perfect. The film is monolayered and uniform in thickness.

Ligands Exchange, Studying the Stability and Optical Properties of CdSe/CdS/ZnS Quantum Dots with Liquid Crystal

Liquid crystal (LC) ligands have the ability to control the dispersion and the homogeneity of quantum dots (QDs) in solution. LC phase transition can be used as a tool to control the assembly of dispersed QDs. Comparing the results before and after the ligands exchange (oleic acid to liquid crystal) highlights some important differences in optical and morphology properties of QDs. We have studied changes in optical properties and a shift in the spectral wavelength band of QDs with LC ligands. Application of LC ligands leads to quenching of the emission and excitation spectra intensity of CdSe/CdS/ZnS QDs. Such hybrid materials have interesting potential for usage in a variety of applications such as photonic materials or (bio) chemical sensors.

The influence of redistribution ions in subphase at the properties Langmuir monolayer: physical and theoretical experiments

The formation of a monolayer and its structure depend on many factors. One of the least studied factors is the influence of the electric field. In this regard, the purpose of this study is to investigate the influence of the direction and magnitude of the electric field on the properties of monolayer, formed on the surface of water. The experiments have revealed: the electric field exerts a significant influence on the formation of monolayers, in particular, during liquid phase formation. The second part of the isotherm (corresponding liquid phase) were significantly stretched. We explain the liquid phase extension by the fact of the charge increasing (and change pH) of the surface region. To confirm this assumption also we made computer modelling of process monolayer formation.

Processes in suspensions of nanocomposite microcapsules exposed to external electric fields

Microcapsules with and without magnetite nanoparticles incorporated in the polyelectrolyte shell were prepared. The effect of external electric field on the nanocomposite polyelectrolyte microcapsules containing magnetite nanoparticles in the shell was studied in this work as a function of the electric field strength. Effect of electric fields on polyelectrolyte microcapsules and the control over integrity of polyelectrolyte microcapsules with and without inorganic nanoparticles by constant electric field has been investigated. Beads effect, aggregation and deformations of nanocomposite microcapsule shell in response to electric field were observed by confocal laser scanning microscopy (CLSM). Thus, a new approach for effect on the nanocomposite microcapsule, including opening microcapsule shell by an electric field, was demonstrated. These results can be used for creation of new systems for drug delivery systems with controllable release by external electric field.