Synthesis of branched polysaccharides by polymerization of 6-O-t-butyldimethylsilyl-D-glucal through stereoregular haloglycosylation

In this letter, we report synthesis of branched polysaccharide 2 by glycosylation of glucal-type monomer 1 with two free hydroxy groups at position 3 and 4. Monomer 1 polymerized with N-halosuccinimide promoter in acetonitrile solvent at room temperature--50 degrees C. The product was isolated as a petroleum ether insoluble fraction. The structure was determined by 1H and 13C NMR spectra as well as elemental analysis to be a polysaccharide consisting of 2-halo-2-deoxy-alpha-D-mannoside units, indicating that the polymerization proceeded via stereoregular glycosylation manner. The molecular weights determined by GPC with DMF were 3,300-4,000. The degree of branching was estimated by the NMR data of the product from the reaction of 2 with 3,5-dinitrobenzoyl chloride.     

Thermoreversible gelation and phase separation in aqueous methyl cellulose solutions

We derived typical phase diagrams for aqueous solutions of methyl cellulose (MC) of different molecular weights via micro‐differential scanning calorimetry, small‐angle X‐ray scattering, and visual inspection. The phase diagrams showed the cooccurrence of gelation and phase separation and qualitatively agreed with the theoretically calculated diagrams. The sol–gel transition line and phase separation line of a lower critical solution point type shifted toward lower temperatures and lower concentrations with an increase in the MC molecular weight. The sol–gel transition line intersected at a temperature higher than the critical point of the phase separation; therefore, both sol–gel phase separation and gel–gel phase separation were possible, depending on the temperature. Specifically, through visual inspection of a high molecular weight MC sample in the critical temperature region, we observed phase separation into two coexisting gels with different polymer concentrations. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 91–100, 2001     

Photocrosslinking reaction of vinyl‐functional polyphenylsilsesquioxane sensitized with aromatic bisazide compounds

Photochemical reactions of aromatic azide groups were applied for a novel photosensitive silicone ladder polymer, that is, partially vinyl‐substituted polyphenylsilsesquioxane sensitized with aromatic bisazide compounds as a photocrosslinker. The photocrosslinking reaction in this system was investigated from the viewpoint of the efficiency of the photocrosslinker, that is, the ratio of the photocrosslinker consumed for crosslinking. The numbers of photodecomposed azide groups and crosslinks in the polymer were determined by Fourier transform infrared measurements. At a higher bisazide concentration, the predominant reaction of nitrenes formed as the intermediary radical by the photolysis of azide was a coupling reaction that could not contribute to the gelation of the polymer. The ratio of the bisazide compound consumed for crosslinking showed the highest value at its concentration of 3 wt % and decreased with the addition of a larger amount. The semiempirical molecular orbital calculations were applied to the theoretical analysis of the photoreaction of nitrenes using phenylnitrene as a model structure. The calculation results indicated that the coupling reaction of nitrenes should proceed more easily than the photocrosslinking reaction in N₂ atmosphere, and the fact that the oxidation of nitrenes should proceed exclusively in the atmosphere including O₂ agreed with the experimental results. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4196–4205, 2001     

Immunoactivity of polymer microspheres with their hydrophilic/hydrophobic heterogeneous surface sensitized with an antibody

Styrene/2-hydroxyethyl methacrylate polymer microspheres consisting of various polymer compositions were produced by emulsifier-free seeded emulsion polymerization technique. Using these microspheres, which should have hydrophilic/hydrophobic heterogeneous surface, the effects of surface hydrophilicity on the main, fundamental requirements for an immunomicrosphere — high colloidal stability, sensitive immunologic agglutinability and insensitive non-specific agglutinability — were studied in detail. There was a region of the surface hydrophilicity that satisfied the three requirements simultaneously.Part CII of the series Studies on Suspension and Emulsion.     

High-performance liquid chromatographic analysis of serum short-chain fatty acids by direct derivatization

The application of direct derivatization in conjunction with high-performance liquid chromatography is described for the analysis of short-chain fatty acids in serum. The method is based on the reaction of these acids with acidic 2-nitrophenylhydrazine hydrochloride, without complicated isolation steps, which produces their non-volatile hydrazine derivatives. The hydrazides of fourteen saturated and unsaturated, straight and branched, short-chain fatty acids were separated from other acid hydrazides and interfering components by a simple solvent extraction, and were eluted isocratically on a reversed-phase C8 column within 24 min. UV detection demonstrated that the detection limits for the acids were 200-400 fmol per injection with linearity over the range from 400 fmol to 5 nmol per injection. Analytical recoveries ranged from 96.8% to 103.1% and coefficients of variation ranged from 0.9% to 3.8%. The present method is simple, accurate and adequate for the analysis of short-chain fatty acids in biological fluids and tissues of patients suffering from organic acidemias.     

Formation of an exciplex with mixed ligands in the mercury-photosensitized luminescence of alcohol-amine mixtures in the liquid phase

The liquid-phase mercury-photosensitized luminescence of tert-butyl alcohol (TL)-tert-butylamine (TM) mixtures has been investigated by a steady-state illumination method over a wide range of substrate concentrations. The emission bands from exciplexes (HgTL* and HgTM*) between an excited mercury atom and an alcohol or an amine molecule were observed at about 330 nm and 370 nm, respectively, in TL and TM solutions in cyclohexane. Two other bands appeared at 405 nm and 455 nm for TM at high concentrations. These bands were previously assigned to two types of 1:2 exciplexes (HgTM(2)* and HgTM(2)**). In TL-TM mixed solutions, a new band appeared at about 400 nm. The intensity of this band increased with increasing concentrations of TL and TM. This band was attributed to an exciplex with mixed ligands (HgTLTM*). This band was observed for the first time in this study. The energized intermediate, (HgTLTM*)(not equal), formed between HgAL* and AM can be effectively stabilized by collisions with solvent molecules in solution, while it decomposes to HgAM* and AL in the gas phase. The results for TL-TM mixtures can be explained by the proposed reaction mechanism.