Study of isocyanate group opening initiated by potassium polyoxyethylene glycolate

The opening of phenyl isocyanate NCO groups initiated by potassium polyoxyethylene glycolate was studied. The rate constants of the initiation, polymerization, cyclic trimerization, and urethane formation reactions proceeding in the system were calculated, and it was concluded that the polymerization makes a predominant contribution to the overall rate of the process. Using IR, UV spectroscopy, and luminescence methods, it was shown that isocyanate groups react via the opening of the carbonyl double bond under the studied conditions. A method for the stabilization of acetal terminal polyisocyanate units by their chemical binding to rare-earth ions was proposed.     

Indirect detection of protein-Metal binding: Interaction of serum transferrin with In<Superscript>3+</Superscript> and Bi<Superscript>3+</Superscript>

Transferrins comprise a class of monomeric glycoproteins found in all vertebrates, whose function is iron sequestration and transport. In addition to iron, serum transferrin also binds a variety of other metals and is believed to provide a route for the in vivo delivery of such metals to cells. In the present study, ESI MS is used to investigate interactions between human serum transferrin and two nonferrous metals, indium (a commonly used imaging agent) and bismuth (a component of many antiulcer drugs). While the UV-Vis absorption spectroscopy measurements clearly indicate that both metals bind strongly to transferrin in solution, the metal-protein complex can be detected by ESI MS only for indium, but not for bismuth. Despite the apparently low stability of the transferrin-bismuth complex in the gas phase, presence of such complex in solution can be established by ESI MS indirectly. This is done by monitoring the evolution of charge state distributions of transferrin ions upon acid-induced protein unfolding in the presence and in the absence of the metal in solution. The anomalous instability of the transferrin-bismuth complex in the gas phase is rationalized in terms of conformational differences between this form of transferrin and the holo-forms of this protein produced by binding of metals with smaller ionic radii (e.g., Fe3+ and In3+). The large size of Bi3+ ion is likely to prevent formation of a closed conformation (canonical structure of the holo-protein), resulting in a non-native metal coordination. It is suggested that transferrin retains the open conformation (characteristic of the apo-form) upon binding Bi3+, with only two ligands in the metal coordination sphere provided by the protein itself. This suggestion is corroborated by the results of circular dichroism measurements in the near-UV range. Since the cellular consumption of metals in the transferrin cycle critically depends upon recognition of the holo-protein complex by the transferrin receptor, the noncanonical conformation of the transferrin-bismuth complex may explain very inefficient delivery of bismuth to cells even when a high dosage of bismuth-containing drugs is administered for prolonged periods of time.     

Framed aromatic polyurethanes based on an anionic macroinitiator, 4,4'-diphenylmethane diisocyanate,and 4,4'-dihydroxy-2,2-diphenylpropane: Synthesis and characterization

Polyurethanes composed of aromatic components are synthesized using the catalytic effect of potassium alcoholates on the reaction of urethane formation occurring with participation of 4,4'-dihydroxy-2,2-diphenylpropane, 4,4'-diphenylmethane diisocyanate, and polyisocyanate, which is a mixture of 4,4'-diphenylmethane diisocyanate and its branched derivatives. In the case of 4,4'-diphenylmethane diisocyanate, segmented polyurethanes with the predetermined length of the rigid block are formed, while the use of polyisocyanate gives rise to framed aromatic polyurethanes. The use of macroinitiators as carriers of potassium alcoholate groups does not cause microphase separation of flexible and rigid segments.     

Transformations of Ethanol Supercritical Fluid

Russian Journal of Organic Chemistry - Nowadays, a new approach to the synthesis of glycerol-free biodiesel is being developed in the framework of sub- and supercritical fluid (SCF) technologies,...     

Limit Automorphisms of the <Emphasis Type="Italic">C</Emphasis>*-Algebras Generated by Isometric Representations for Semigroups of Rationals

We consider inductive sequences of Toeplitz algebras whose connecting homomorphisms are defined by collections of primes. The inductive limits of these sequences are C*-algebras generated by representations for semigroups of rationals. We study the limit endomorphisms of these C*-algebras induced by morphisms between copies of the same inductive sequences of Toeplitz algebras. We establish necessary and sufficient conditions for these endomorphisms to be automorphisms of the algebras.     

On Covering Groups

We study finite-sheeted covering mappings from compact connected spaces onto compact connected groups. For such a covering mapping we consider a method of supplying its covering space by a group structure. The covering space endowed with that group structure is a topological group, and a given covering mapping turns into a homomorphism of compact connected groups.

     

Efficient spectral and pseudospectral algorithms for 3D simulations of whistler-mode waves in a plasma

Efficient spectral and pseudospectral algorithms for simulation of linear and nonlinear 3D whistler waves in a cold electron plasma are developed. These algorithms are applied to the simulation of whistler waves generated by loop antennas and spheromak-like stationary waves of considerable amplitude. The algorithms are linearly stable and show good stability properties for computations of nonlinear waves over tens of thousands of time steps. Additional speedups by factors of 10–20 (comparing single core CPU and one GPU) are achieved by using graphics processors (GPUs), which enable efficient numerical simulation of the wave propagation on relatively high resolution meshes (tens of millions nodes) in personal computing environment. Comparisons of the numerical results with analytical solutions and experiments show good agreement. The limitations of the codes and the performance of the GPU computing are discussed.     

Supercritical Fluid Impregnation of Broken Stone with Deasphaltizate Obtained from Oil Residue

Results are presented concerning the studies on obtaining a heavy oil residue, its deasphalting and the impregnation of crushed carbonate stone with deasphaltizate. The heavy oil residue is obtained via the separation of extra-heavy crude oil using a steam thermal method. The deasphalting of the oil residue and the impregnation of crushed carbonate stone are carried out using a propane-butane solvent in the liquid and supercritical fluid state, respectively.