Synthesis of Branched Chemodegradable Homopolymers of N-(2-Hydroxypropyl)methacrylamide

Branched water-soluble N-(2-hydroxypropyl)methacrylamide homopolymers containing interchain urethane links were prepared. The hydrodynamic and molecular-weight characteristics of the branched homopolymers and the rate of their hydrolysis under the conditions close to those of a living body (saline, pH 7.0, 37°C) were determined.     

Synthesis,Structure, and Characteristics of Ultra-High-Molecular-Weight Poly-N-methacryloyloxyethyl-N,N,N-Trimethylammonium Methyl Sulfate

Two procedures for synthesis of water-soluble poly-N-methacryloyloxyethyl-N,N,N-trimethylammonium methyl sulfate are compared. Synthesis occurred by the radical mechanism with the Co(III)-glycine system and with acid catalytic initiation. The effect of the initiator nature and the reaction conditions on the course of polymerization was studied.     

Spectroturbidimetric Determination of the Size and Concentration of Terrestrial Particles in Potable Water

A method was proposed for determining the average size and mass-space concentration of terrestrial particles in potable water from the turbidity spectrum. This method was applied to a systematic study of a formazine suspension and potable water samples.     

Kinetics of protein binding in solid-phase immunoassays: theory

In a solid-phase immunoassay, binding between an antigen and its specific antibody takes place at the boundary of a liquid and a solid phase. One of the reactants (receptor) is immobilized on a surface. The other reactant (ligand) is initially free in solution. We present a theory describing the kinetics of immunochemical reaction in such a system. A single essential restriction of the theory is the assumption that the reaction conditions are uniform along the binding surface. In general, the reaction rate as a function of time can be obtained numerically as a solution of a nonlinear integral equation. For some special cases, analytical solutions are available. Various immunoassay geometries are considered, in particular, the case when the reaction is carried out on a microspot.     

Electron microscopy studies on the coil-to-globule transition of a polyelectrolyte in a water–acetone mixture

A high molar mass polycation poly(methacryloylethyl trimethylammonium methylsulphate), PMETMMS, dissolved in mixtures of water and acetone, was studied using light scattering during the reversible coil-to-globule transition. When the mass fraction of acetone in the solvent mixture, γ, is higher than 0.80, PMETMMS adopts a globular state but does not aggregate. The collapse of PMETMMS can also be induced by the dilution of the polymer solution, if 0.70 ≤ γ < 0.80, and the solvent composition is kept constant. The results obtained by light scattering have been confirmed using a transmission electron microscope with which the collapse of PMETMMS has been observed. At high polymer concentration and 0.70 ≤ γ < 0.80, a transient network is formed: coils strongly interact with each other via dipole–dipole interactions in a thermodynamically poor solvent. At low concentration regime when 0.70 ≤ γ < 0.80, or in solutions with the mass fraction of acetone higher than 0.80, all the PMETMMS molecules are collapsed. In the intermediate region, the collapse of PMETMMS is gradual and coils, globules, as well as fragments of the network coexist in the solution. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3337–3343, 1999     

Lateral Surface Electrization of Z-Cut Lithium Niobate During Pyroelectric Effect

Russian Physics Journal - The paper focuses on the surfaces electrization of Z-cut single-crystal lithium niobate during the pyroelectric effect. It is shown that the properties of the electric...     

Crystalline inclusion complex of a calixarene with a nitroxide

The first capsular crystalline inclusion complex of para-hexanoyl calix[4]arene with stable nitroxyl radical DEPN has been isolated and showed a low mobility of the radical in the capsule.     

Facilitated diffusion of DNA-binding proteins

The diffusion-controlled limit of reaction times for site-specific DNA-binding proteins is derived from first principles. We follow the generally accepted concept that a protein propagates via two competitive modes, a three-dimensional diffusion in space and a one-dimensional sliding along the DNA. However, our theoretical treatment of the problem is new. The accuracy of our analytical model is verified by numerical simulations. The results confirm that the unspecific binding of protein to DNA, combined with sliding, is capable to reduce the reaction times significantly.     

Facilitated diffusion of DNA-binding proteins: Simulation of large systems

The recently introduced method of excess collisions to estimate reaction times of protein-DNA systems in the presence of facilitated diffusion ("sliding") requires a cell of full system size. This bottleneck is avoided with a modification, by which a set of empirical parameters is calibrated using numerical simulations of a small test system. Once this is done, reaction times for systems of arbitrary dimensions are derived by extrapolation. It is shown that at physiological sliding lengths a test system of the order of 100 nm radius suffices to extract accurate reaction times for realistic cell dimensions. The achieved speedup, when compared to explicit simulations of the reaction process, is increasing in third order of the extrapolated radius of the cell.