Temperature scanning FTIR analysis of hydrogen bonding states of various saccharides in amorphous matrixes below and above their glass transition temperatures

Temperature scanning Fourier transform infrared, TS-FTIR, spectroscopy of various amorphous sugar matrixes was conducted to investigate the relationship between the glass transition temperature, T(g), of an amorphous sugar matrix and the nature of the hydrogen bonds in the matrix. An amorphous sugar matrix was prepared by air-drying an aqueous solution of sugar, and the degree of formation of hydrogen bonds in the matrix was evaluated at different temperatures using the peak positions of the IR band corresponding to the O-H stretching vibration at around 3400 cm(-1). The T(g) value increased with increasing peak position of the O-H stretching vibration at T(g) and were correlated reasonably well with the magnitude of the peak shift by the temperature increase (from 25 degrees C) to the T(g) value. This demonstrates that the amorphous sugar matrix, in which the segments are fixed by fewer hydrogen bonds, has a higher thermal resistance. The glycosidic linkage largely contributes to the restriction of the segments, pyranose ring, rather than a hydrogen bond. As the degree of polymerization of pyranose rings increases, the degree of hydrogen bond formation needed to hold the matrix in a fixed position decreases. However, the magnitude of the restriction of pyranose rings by a glycosidic linkage changes depending on the type: the restrictions imposed by alpha-1,1 and -1,6 glycosidic linkages are the tightest and most flexible of all of the types of glycosidic linkages, respectively.     

Removal of proteinaceous soils using hydroxyl radicals generated by the electrolysis of hydrogen peroxide

We have developed here for the first time a novel method to generate hydroxyl radicals, *OH, by applying slightly negative electric potentials (-0.2--0.8 V vs Ag/AgCl) to the surface of a metal (or metal oxide) that is in contact with hydrogen peroxide solution containing a supporting electrolyte. Namely, *OH radicals were generated at the surface by the electrolysis of hydrogen peroxide according to the equation, H2O2+e- --> *OH+OH-. This method was used to clean a stainless steel fouled with a model protein, beta-lactoglobulin. The *OHs generated at the surface were effective in removing beta-lactoglobulin that had been irreversibly adsorbed, by several minutes of treatment at room temperature (22+/-2 degrees C). The removal rates measured for various concentrations of H2O2 and supporting electrolyte and different potentials were determined exclusively by the electric current.     

Separation of trace amounts of rhodium(III) with tri-n-butyl phosphate from nitric acid and sodium trichloroacetate media

A new method for the quantitative extraction and separation of trace amounts of rhodium from nitric acid and sodium trichloroacetate media has been established based on the formation of an ion-association complex of hexahydrated rhodium cation Rh(H₂O)₆ ³⁺ and the trichloroacetate (TCA) anion in tri-n-butyl phosphate (TBP). The effect of various factors (solvent, pH, sodium trichloroacetate, shaking time, phase volume ratio, composition of the extracted species, foreign ions, transformation of rhodium chlorocomplexes into hexahydrated cation, etc.) on the extraction and back-extraction of rhodium has been investigated. The method can be combined with subsequent FAAS determination of rhodium. The procedure was applied to determine rhodium traces in chloroplatinic acid and palladium chloride. Received: 17 March 2000 / Revised: 15 May 2000 / Accepted: 19 May 2000     

Photoluminescence and FT-IR studies of the dissociative adsorption of H2 on the active ZrO2 catalyst and its role in the hydrogenation of CO

Photoluminescence and FT-IR studies of the adsorption of H₂ on ZrO₂ catalysts have been performdd to clarify the true natuee of active surface sites for the activaiion of H₂ in connection with the CO — H₂ reaction on the catalyst. The results indicate that the coordinatively unsaturated surface sites with different coordination numbers are generated on the surfaces by evacuation at temperatures higher than 600 K. These surface sites of lower coordination play a significant role in the reversible and irreversible dissociative adsorption of H₂ on the active ZrO₂ catalyst. The former seems to act as active hydrogen species for the CO — H₂ reaction to form branched hydrocarbons on the ZrO₂ catalyst.     

Reaction of trist(trifluoromethyl)cyclopropenyl trifluoromethyl ketone with azo compounds in the presence of triphenylphosphine,and synthesis of tetrakis(trifluoromethyl)pyridazine.

The title cyclopropenylketone reacts with azo compounds and tri-phenylphosphine to give unique heterocycles; tricyclourazoles and a diazaoxacyclooctatriene. The formers were converted into a pyridazine.     

Mechanism of catalytic reduction of NO by H2 or CO on a Pd foil; Role of chemisorbed nitrogen on Pd

The adsorption of NO and its reaction with H₂ over polycrystalline Pd were investigated using flash desorption technique and ultraviolet photoelectron spectroscopy under 10^?5 Pa pressure range of reactants and surface temperatures between 300 and 900 K. NO was adsorbed dissociatively onto the Pd surface above 500 K, and the heat of dissociative adsorption was ca. 126 kJ/mol. Atomic nitrogen was observed to accumulate on the Pd surface during the NO-H₂ reaction, whose desorption rate exhibited second order kinetics and is expressed as follows: V_d = 10^{?9.8 ± 0.3}exp(?67(kJ/mol)/RT) (cm²/atom·s). Hydrogenation of the adsorbed nitrogen proceeded rapidly at 485 K. It was confirmed from these results that formation of N₂ and NH₃ in the NO-H₂ reaction proceeds through this atomically adsorbed nitrogen. Pd-N bond energy and enthalpies of some intermediate states of the NO-H₂ reaction were estimated.     

Preparation and addition--elimination reactions of benzyl alpha,beta,beta-trifluoroacrylate. A new stereoselective approach to (Z)-beta-substituted alpha,beta-difluoroacrylates

Benzyl alpha,beta,beta-trifluoroacrylate (1) was prepared in good yield via the reductive Br-F elimination of benzyl 2-bromo-2,3,3,3-tetrafluoropropanoate or the palladium-catalyzed cross-coupling reaction of 1,2,2-trifluorovinylstannane with benzyl chloroformate. On treating 1 with various Grignard reagents or dialkylzinc reagents in the presence of copper(I) salt, the corresponding beta-substituted alpha,beta-difluoroacrylates were obtained in high yields with high Z-selectivity. Additionally, trialkylaluminum reagents were also found to be good nucleophiles, the corresponding addition-elimination products being afforded in good yields but with low stereoselectivity.     

Artificial polymeric receptors on the cell surface promote the efficient cellular uptake of quantum dots

In our previous paper, secondary-amine appended cationic polymer 1 was used as a scaffold to display artificial receptors on a cell surface (R. Kamitani et al., ChemBioChem, 2009, 10, 230). This polymer can be retained on the cell surface for more than 30 min before being slowly internalized into the cells. In this study, our aim is to achieve the efficient internalization of quantum dots (QDs) into target cells via artificial receptors on the polymer. As a receptor molecule, N-acetylglucosamine (GlcNAc) moieties were introduced into the polymer, and GlcNAc binding protein-displaying QDs were used as a ligand. We found that ligand-presenting QDs could be internalized effectively into cells via polymer-mediated endocytosis, whereas QDs were not internalized into untreated cells. These data suggest that our method based on cell-surface engineering using polymers affords a new approach to the delivery of various poorly permeable nanoparticles into cells.     

Dynamic Investigation of Mechanism of Catalytic Reactions as Revealed by Spectroscopic Techniques

The study of chemisorption of gases on catalyst surfaces is of primary importance in elucidating the mechanism of heterogeneous catalysis. Accordingly, the adsorption of each of the gases which participate in the catalysis has been studied separately in many cases. However, chemisorption on the catalyst surface during the progress of reaction, generally speaking, cannot be estimated from the adsorption equilibrium of reactants and products measured separately for each species, but depends upon the mechanism of the reaction, the interaction among the adsorbed species, the formation of reaction intermediates or surface complexes, and the area of active region on the surface.