B. G. Sukhov

Bactericidal action of Ag(0)-antithrombotic sulfated arabinogalactan nanocomposite: coevolution of initial nanocomposite and living microbial cell to a novel nonliving nanocomposite

UNLABELLED The first step of the interaction between Ag(0) nanocomposite with antiatherogenic anticoagulant sulfated arabinogalactan involves the transportation and concentration of antimicrobial nanosilver in the bacteria target (E. coli). Further, the silver ions in dynamic equilibrium with metal backbone of the nanoparticles (NPs) reach the membrane surface and bond with this surface. Simultaneously, the redox interaction of silver cations with main reducing components of the membrane surface is triggered to afford the zero-valence silver atoms that are stabilized to form metal clusters, or new NPs of silver. Size and morphology of these NPs are defined by specific conditions of their synthesis involving the microorganism membrane: The Ag(0) NPs formed on membranes and fragments of the destroyed bacteria have other morphology (including triangular) and smaller sizes in comparison with the initial nanocomposite that additionally enhances antimicrobial activity of such NPs. FROM THE CLINICAL EDITOR This study investigates silver nanocompistes (Ag(0) NPs) and their interaction with antiatherogenic anticoagulant sulfated arabinogalactan. A complex set of interactions are described, leading to Ag(0)NPs formed on membranes and fragments of destroyed bacteria demonstrating altered morphology and smaller sizes in comparison with the initial nanocomposite that additionally enhances antimicrobial activity of such NPs.

Redox reactions of arabinogalactan with silver ions and formation of nanocomposites

Formation of silver nanoparticles in the course of chemical reduction of AgNO3 with arabinogalactan in aqueous alkaline solution was studied by electronic absorption spectroscopy and X-ray diffraction analysis. The pH of the solution was found to be the major factor affecting the degree of reduction of Ag+ ions. The probable reaction mechanism was discussed. Composites containing up to 58% Ag, with the metal particle size of 7–16 nm, were prepared. The nanoparticle size can be controlled by varying the reactant ratio AgNO3: arabinogalactan. Chemical modification of arabinogalactan was confirmed by IR and 13C NMR spectroscopy and by TLC.

Addition of secondary phosphines to N-vinylpyrroles

Abstract Secondary phosphines 1 – 3 react readily with N -vinylpyrroles 4 and 5 under radical initiation to give regiospecifically anti-Markovnikov adducts, diorganyl-2-(1-pyrrolyl)ethylphosphines 6a – d , highly reactive building blocks for organic synthesis, in 88–91% yields.

Reactions of Elemental Phosphorus and Phosphine with Electrophiles in Superbasic Systems: XIV.1 Phosphorylation of 2-Vinylnaphthalene with Elemental Phosphorus and Phosphines in the KOH-DMSO System

Elemental phosphorus (red or white) reacts with 2-vinylnaphthalene while heating at 90-96°C in the superbasic KOH-DMSO system to form 2-(2-naphthyl)ethylphosphine, 2-(2-naphthyl)ethylphosphinic acid, bis[2-(2-naphthyl)ethyl]phosphine, bis[2-(2-naphthyl)ethyl]phosphine oxide, and tris[2-(2-naphthyl)ethyl]phosphine oxide in a total yield of up to 40%. Selective conditions for preparing the tertiary phosphine oxide from white phosphorus and 2-vinylnaphthalene in 58% yield were found. Phosphine and (2-phenylpropyl)phosphine add to 2-vinylnaphthalene in the KOH-DMSO system to form, under certain conditions, corresponding secondary phosphines in high yields.

Formation kinetics of gold nanoparticles in the galactomannan polysaccharide matrix

282 Gold nanoparticles and nanocomposites based on them are finding more and more extensive use as highly effective catalysts of various chemical processes [1], optical sensors of biospecific interactions [2], agents for the targeted drug delivery [2] and photo thermolysis of cancer cells [3], inhibitors of autoim mune diseases [4], etc. However, the problem of ther modynamic instability of nanoparticles caused by excess of their surface energy has not still been ulti mately solved [5, 6]. This problem is addressed using stabilizing polymeric matrices of synthetic and natural origin, in particular, polysaccharides, which impart a specific set of additional physicochemical and biolog ical properties to nanoparticles [7, 8]. Galactomannan is a natural water soluble polysac charide widely used in food and pharmaceutical industries [9]. Previously, it was used to prepare bio logically active nanocomposites containing silver metal nanoparticles [10]. Here we report on the results of synthesis of bio compatible aggregation stable nanocomposites con sisting of zerovalent gold nanoparticles stabilized by galactomannan macromolecules. The macromolecule of this polysaccharide (MM 1300 kDa) consists of 1,4 β polymannopyranoside chain with single α galactopyranose side branches. The Man : Gal ratio determined by quantitative 13C NMR spectroscopy is 1.6 [10].

Synthesis of silver-containing nanocomposites based on humic substances of brown coal and their antioxidant activity

72 Silver nanoparticles and nanomaterials based on them exhibit a broad spectrum of biological properties and are multipurpose means for biomedicine [1, 2]. Indeed, the antimicrobial activity of silver nanoparti cles with respect to living cells may be determined by their size, shape, ligand environment, and particular preparation method [3, 4]. One of the most conve nient and environmentally safe methods for the syn thesis of metallic nanoparticles is reduction of a metal containing precursor in water in the presence of a sta bilizer for the formed nanoparticles (these may be polyhydric alcohols [5, 6], polysaccharides [7, 8], polyphenols [9, 10], and the like).

Colloidal aggregates of Pd nanoparticles supported by larch arabinogalactan.

Palladium nanoparticles (PdNPs) are used in catalysis, hydrogen storage, biomedicine, and so on. Arranging the self-assembly of PdNPs within colloidal aggregates is desirable for improving their consumer properties. Stable widely dispersed colloidal aggregates of larch arabinogalactan (LARB) containing nanosized (5-nm) PdNPs were obtained by reducing Pd ions in alkaline solutions of LARB. Centrifugation resulted in a set of LARB-PdNP colloids ranging from 60 to 240 nm. The colloids were studied by static light scattering (SLS) and dynamic light scattering (DLS). The SLS data presented as Kratki plots correspond to a particle scattering factor of linear rather than branched chains. The fractal dimension of the LARB-PdNP colloids was found by SLS to be d = 1.96, which is between the values for diffusion- and reaction-limited aggregation. This result is ascribed to the aggregates internal motion, which is evident from the power-law exponent of the dependence of the DLS relaxation rate on the scattering vector, ~ q(α) with α = 2.24. The structure-sensitive ratio of the radius of gyration to the hydrodynamic radius was found to vary within the interval of 0.8 ≤ R(g)/R(h) ≤ 1.2 corresponding, to the spherical form of LARB-PdNP colloids. A spiderweblike PdNP distribution pattern was observed by transmission electron microscopy. Insertion of PdNPs did not affect the fractal dimension, the power-law exponent α, or the architecture of the pristine LARB aggregates in water. The red shift of the surface plasmon extinction observed with increasing LARB-PdNP colloidal size indicates the collective optical response of the PdNP ensemble in the colloid.

Molecular-weight characteristics of galactomannan and carrageenan

It was established that the action of [H+] at concentration 1.96∙10–2 M at 90°C for 5–20 min decreased sharply the molecular weight of galactomannan and carrageenan and increased their overall reductive capability. The action of [OH–] at concentrations 2.6∙10–2 and 26∙10–2 under the same conditions was characterized by a slow decrease of the molecular weight and retention of the functionality of the polysaccharides. It was shown that modified galactomannan and κ-carrageenan exhibited increased watersolubility while retaining the structure and gel-forming and stabilizing capabilities and degree of sulfation (for carrageenan).

Regio- and stereospecific addition of phosphines to cyanoacetylenes

Abstract Primary and secondary phosphines add regio- and stereospecifically to phenylcyanoacetylene and 4-hydroxy-4-methylpent-2-ynenitrile under mild conditions to form corresponding functionalized secondary and tertiary phosphines of Z -configuration in 70–91% yield. According to ESR and UV data, the addition of primary phosphines to phenylcyanoacetylene involves a single electron transfer process.

Specific features of formation of silver nanoparticles in the polymer matrix

Nanocomposite materials containing silver nano� particles possess unique properties and are promising for medicine, optoelectronics, nanophotonics, and catalysis [1–3]. The properties of silver nanoparticles (dimension, distribution, stability, etc.) considerably depend on both the nature of the stabilizing polymeric matrix and the conditions of nanoparticle formation in the composite. This study is concerned with the synthesis and