Pulsed NMR study of the curing process of epoxy resin

To analyze a curing process of epoxy resin in terms of molecular motion, we adapted a pulsed NMR method. Three kinds of (1)H spin-spin relaxation times (T(2L) (long), T(2S) (short) and T(2M) (intermediate)) were estimated from observed solid echo train signals as the curing process proceeded. A short T(2S) value below 20 micros suggests the existence of a motion-restricted chain, that is, cured elements of resin, and its fraction, P(S), sigmoidally increased with the curing time. On the other hand, the fraction of T(2L), P(L), decreased with the reaction time reciprocally against P(S), suggesting the disappearance of highly mobile molecules raised from pre-cured resin. The spin-lattice relaxation time, T(1), was also measured to check another aspect of molecular motion in the process. T(1) of the mixed epoxy resin and curing agent gradually increased just after mixing both of them. This corresponds to an increment of a less-mobile fraction, of which the correction time is more than 10(-6) s, and also means that the occurrence of a network structure whose mobility is strongly restricted by chemically bonded bridges between the epoxy resin and curing agent. The time courses of these parameters coincided with those of IR peaks pertinent to the curing reaction. Therefore, pulsed NMR is a useful tool to monitor the hardening process of epoxy resin in real time non-distractively in terms of the molecular motion of protons.     

Polarization gratings in twisted-nematic liquid-crystal composites doped with azobenzene dye

Highly efficient and functionalized polarization gratings have been recorded in azobenzene-containing mesogenic composites with twisted nematic cell configurations. The polarization gratings formed in azobenzene-containing mesogenic composites show a high diffraction efficiency of more than 45% and convert the polarization state of light at the same time. The polarization direction of the diffracted laser beams can be controlled by the twisted angle of the nematic cell. These characteristics of the polarization gratings are well explained by means of Jones calculus.     

Spectrophotometric determination of urinary protein with o-sulfophenylfluorone-metal complex.

A simple and sensitive spectrophotometric method for the determination of human serum albumin (HSA) was established based on the ternary complex-formation reaction of HSA with o-sulfophenylfluorone (SPF) as a xanthene dye and metal ion (niobium(V) and bismuth(III)) in the presence of a dispersion agent. This new method enabled the determination of HSA in the range of 1 - 15 microg/ml HSA by measuring the difference of the absorbance at 530 nm between HSA-SPF-metal ion and SPF-metal ion solutions. In the determination of HSA, this method is about 2-times more sensitive than the Pyrogallol Red-molybdenum(VI) method (PR method), which accounts for more than 80% of the quantification methods for urinary protein assays in Japan. There was no significant difference between the results obtained by the present method and the PR method for human urine samples. The binding process between the SPF-metal complex and HSA was studied by determining the binding parameters and the thermodynamic parameters.     

High-performance liquid chromatographic determination and metabolic study of sennoside a in daiokanzoto by mouse intestinal bacteria

Daiokanzoto (DKT, combination of rhubarb and glycyrrhiza), a Kampo medicine, is clinically effective for constipation. Sennoside A is well known to induce diarrhea. Sennoside A is a prodrug that is transformed into an active metabolite, rheinanthrone, by intestinal bacteria. In this study, we investigated the effects of glycyrrhiza on the activity of sennoside A metabolism in intestinal bacteria using mouse feces. A high-performance liquid chromatography (HPLC) method for the determination of sennoside A in incubation mixture of DKT with mouse feces was established. The retention time of sennoside A was 9.26±0.02 min with a TSKgel ODS-80TsQA column by linear gradient elution using a mobile phase containing aqueous phosphoric acid and acetonitrile and detection at 265 nm. We found that the activity of sennoside A metabolism in intestinal bacteria was significantly accelerated when glycyrrhiza, liquiritin or liquiritin apioside coexisted with sennoside A, whereas that of glycyrrhizin was not altered. This method is applicable for determination of the activity of sennoside A metabolism by anaerobic incubation of DKT with mouse feces.     

Elimination of ingredients effect to improve the detection of anti HIV-1 p24 antibody in human serum using SPR apparatus.

Highly sensitive detection of proteins in serum becomes difficult in some cases during surface plasmon resonance (SPR) measurements, because some ingredients in the serum hugely enhance non-specific reactions on the sensing chip of SPR. It is well recognized that the antibody against core protein p24 of HIV in serum is one of the most important proteins in the accurate diagnosis of infection with HIV. In this study, we could attain the accurate detection of anti p24 antibody in human serum by eliminating the serious effects of the ingredients in serum on the measurement of SPR by employing these procedures: 1) blocking the gold surface of the sensing chip with human serum and 2) heating the serum sample at 56 degrees C for 30 min. Without these treatments, the signal of SPR was considerably suppressed on the measurements of the anti p24 antibody which contained human serum, making the accurate detection difficult. However, with introducing the above two treatments, the sensing of anti p24 antibody in human serum was improved, while a small non-specific reaction was still observed. By removing the non-specific reaction caused by the ingredients in the serum, we could accurately measure the antibody for p24 in human serum sample over the range from 1 to 20 micrograms/ml.     

Catalytic phenylborylation reaction by iridium(0) nanoparticles produced from hydridoiridium carborane

Well-dispersed iridium(0) nanoparticles stabilized with the ionic liquid, trihexyltetradecylphosphonium methylsulfonate, [THTdP][MS], have been successfully prepared by reduction of the precursor hydridoiridium carborane, (Ph 3P) 2Ir(H)(7,8- nido-C 2B 9H 11). The iridium nanoparticles were found to be active catalysts for arylborylation, forming boric acids. The activity of the catalyst has been investigated as a function of the activating base, and reaction conditions. The highest yield of 91% was achieved in a microwave reactor using the base, tetra-2-pyridinylpyrazine, in the presence of [THTdP][MS]. The catalytic system could be recycled at least six times with less than a 0.5% loss of activity.     

Unusual condensation of 3-Thia[5](1,1')ferrocenophane-1,5-dione with glyoxal. Formation of [1.1](2,3)thiopheno(1,1')ferrocenophane-1,7-dione

When 3-thia [5](1,1')ferrocenophane-1,5-dione 2 was condensed with glyoxal in the presence of sodium ethoxide, a thiophene-2,3-diyl derivative 3 was obtained as a sole product, instead of the expected 2,5-substituted compound 1.     

Toward the synthesis of γ-pyrone-containing natural products: diastereoselective aldol-type reaction of a γ-pyrone

The diastereoselective aldol-type reaction of a γ-pyrone via a sodium anion has been developed. This reaction is useful for synthesizing γ-pyrone-containing natural products. Also, we applied the Mukaiyama aldol-type reaction of silyl enol ether of γ-pyrone by using TiCl₄. This Mukaiyama aldol-type reaction of γ-pyrone indicated higher anti-aldol selectivity than the aldol-type reaction of a γ-pyrone with NaHMDS.