Structural and conformational characteristics of DNA complexes with polycations of different structure

The formation of DNA complexes with polycations of different structure (homopolymers: N,N-dimethylaminoethyl and methylsulfate salt of N,N,N-trimethylaminoethylmethacrylate, along with a copolymer of N,N-dimethylaminoethyl methacrylate with N-methacryloylaminoglucose) in water-salt solutions, was studied by the method of static and dynamic light scattering. It was shown that, depending on the value of ϕ = [mol polycation]/[mole of DNA], complexes of different structure are formed: in field ϕ < 6, they are dense and compact formations; when ϕ > 6 in the presence of a large excess of polycations, loose structures are formed. The extreme dependence of the molecular weight of formed supramolecular structures on the values of ϕ was established.     

Two fluoroalcohols as components of basic buffers for liquid chromatography electrospray ionization mass spectrometric determination of antibiotic residues

Two fluoroalcohols--1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol (HFTB)--were evaluated for the first time as volatile buffer acids in the basic mobile phase for reversed-phase chromatography with electrospray ionization-mass spectrometric (LC-ESI-MS) detection of five antibiotics. Chromatographic separation as well as positive and negative ion ESI-MS intensities using these novel buffer components were compared to traditional buffer systems. Overall, the highest signal intensities and best chromatographic separation for the five antibiotics (ciprofloxacin, norfloxacin, ofloxacin, sulfadimethoxine and sulfamethoxazole) were achieved using 5 mM HFIP as the buffer acid to methanol : water mobile phase (pH of the aqueous component adjusted to 9.0 with ammonium hydroxide). Comparable results were achieved using 5 mM HFTB (pH adjusted to 9.0 with ammonium hydroxide). The suitability of HFIP for analysis of antibiotic residues in lettuce is demonstrated.     

Adsorption of Hydroxyethyl Cellulose Selenium Nanoparticles during Their Formation in Water

Two previously unknown phenomena were observed in studying the reduction of selenious acid with ascorbic acid in an aqueous hydroxyethyl cellulose solution: (1) formation of nanoparticles of amorphous Se⁰ with uniform particle size distribution and mean particle radius of 15 ± 4 nm and (2) adsorption of more than 3000 macromolecules on these nanoparticles with formation of spherical nanostructures.     

Interaction of Se0 nanoparticles stabilized by poly(vinylpyrrolidone) with gel films of cellulose Acetobacter xylinum

The sorption and desorption of poly(vinylpyrrolidone)-Se⁰ (PVP-Se⁰) nanoparticles on gel films of cellulose Acetobacter xylinum (CAX) are investigated. It is revealed that the hydrodynamic radius R _h of PVP-Se⁰ nanoparticles decreases from 57 nm in the initial solution (without CAX gel films) to 25 nm after the sorption of nanostructures on gel films and then increases to approximately 100 nm after the desorption of nanoparticles with water from dry samples of the CAX gel film-PVP-Se⁰ nanocomposite. It is found that selenium atoms do not penetrate into crystallites of the cellulose nanofibrils and replace water molecules sorbed by the primary hydroxyl groups of their walls. Poly(vinylpyrrolidone)-Se⁰ nanoclusters differ in the number and size upon their sorption inside the cellulose gel film and on the film surface.     

Theoretical study of the decaying convective turbulence in a shear-buoyancy PBL

The derivation of a theoretical model for the decaying convective turbulence in a shear-buoyancy planetary boundary layer is considered. The model is based on the dynamical equation for the energy density spectrum in which the buoyancy, mechanical and inertial transfer terms are retained. The parameterization for the buoyancy and mechanical terms is provided by the flux Richardson number. Regarding the inertial term an approach employing Heisenberg’s spectral transfer theory is used to describe the turbulence friction, caused by small eddies, responsible for the energy dissipation of the large eddies. Therefore, a novelty in this study is to utilize the Adomian decomposition method to solve directly without linearization the energy density spectrum equation, with this the nonlinear nature of the problem is preserved. Therefore, the errors found are only due to the parameterization used. Comparison of the theoretical model is performed against large-eddy simulation data for a decaying convective turbulence in a shear-buoyancy planetary boundary layer. The results show that the existence of a mechanical turbulent driving mechanism reduces in an accentuated way the energy density spectrum and turbulent kinetic energy decay generated by the decaying convective production in a shear-buoyancy planetary boundary layer.     

Coating electrospun chitosan nanofibers with polyelectrolyte multilayers using the polysaccharides heparin and N,N,N-trimethyl chitosan

A new method is presented for functionalizing electrospun nanofibers with GAGs and growth factors by PEM deposition. Electrospun chitosan nanofibers, spun from trifluoroacetic acid and dichloromethane, were coated with PEMs, using the polysaccharides heparin and N,N,N-trimethyl chitosan. FGF-2 was adsorbed on the PEM-coated nanofibers. Nanofiber neutralization, PEM construction, and FGF-2 adsorption were monitored using FT-IR spectroscopy and X-ray photoelectron spectroscopy. Alcian blue staining was used to confirm the presence of heparin. SEM was used to study nanofiber morphology.     

Complex formation of daunomycin with poly(vinylpyrrolidone) and poly(ethylene glycol)

Russian Journal of General Chemistry - Complexes of the anthracycline antitumor antibiotic daunomycin with biocompatible polymer carriers, poly(vinylpyrrolidone) and poly(ethylene glycol), have...