Study on Ion-dynamics in solids by hole burning spectroscopy

The importance of hole burning spectroscopy for studying elementary migration processes of ions in superionic conductors is being discussed using two examples. In β″-alumina, the potential energy for the conduction of ions along the conduction path, as obtained from the analysis of the results of hole burning spectroscopy, showed that there are two different bare-potentials along the ionic conduction path. One of them is higher than the activation energy for ionic conductivity. This result gives direct evidence that an ionic interaction among the conducting ions plays an important role for ion migration in β″-alumina. In YSZ with various concentration of Y₂O₃, we have observed persistent holes in Pr³⁺ ions doped samples. Their disordered nature will be discussed using the bandwidth considerations. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15–21, 2002.     

A simple method for synthesis of amides and peptides through acyl chlorides : A rapid synthesis of thyrotropin releasing hormone

By improvement of the classical SOCl₂-pyridine method for the preparation of acid chlorides, amides and optically pure peptides were synthesized rapidly in a simple manner from DCHA dicyclohexylammonium) salts of carboxylic acids. This modified SOCl₂-pyridine method was applied to a rapid synthesis of TRH.     

Asymmetric reactions with cyclodextrins

Cyclodextrins have great potential for exploitation as a useful tool for asymmetric induction. Many kinds of asymmetric reaction have been achieved in the presence of cyclodextrin under various conditions such as the solid phase, heterogeneous suspension or homogeneous aqueous or organic solution. Complexation is essential for asymmetric induction. What is necessary to improve CDs for greater asymmetric induction?     

Recovery of host crystals from inclusion crystals of <Emphasis Type="Italic">p-tert-</Emphasis>butylcalix[4]arene and <Emphasis Type="Italic">p-tert</Emphasis>-butylthiacalix[4]arene by the treatment with a solvent and/or supercritical CO<Subscript>2</Subscript>

Upon stirring inclusion crystals of p-tert-butylthiacalix[4]arene (2) in solvents with heating, guest compounds were efficiently desorbed to yield guest-free crystals. More specifically, upon treatment with methanol, the exchange of guest compounds with methanol in the crystals, followed by the desorption of the methanol afforded metastable host crystals 2β, whereas, upon treatment with heptane, the dissolution of the inclusion crystals and simultaneous crystallization of compound 2 afforded stable host crystals 2α. Further, a host crystal of p-tert-butylcalix[4]arene (1) was recovered by the treatment of 2:1 (host/guest) inclusion crystals of compound 1 with supercritical carbon dioxide (scCO₂), and through the combination of the guest exchange of 1:1 inclusion crystals of compound 1 with hexane and scCO₂ treatment of the resulting 2:1 inclusion crystals 1₂·hexane. Although the recovered host crystal of compound 1 contained a small amount of CO₂, it could be reused for the inclusion of organic compounds.     

Total Synthesis and Biological Evaluation of the Glycosylated Macrocyclic Antibiotic Mangrolide A

The macrocyclic antibiotic mangrolide A has been described to exhibit potent activity against a number of clinically important Gram‐negative pathogens. Reported is the first enantioselective total synthesis of mangrolide A and derivatives. Salient features of this synthesis include a highly convergent macrocycle preparation, stereoselective synthesis of the disaccharide moiety, and two β‐selective glycosylations. The synthesis of mangrolide A and its analogues enabled the re‐examination of its activity against bacterial pathogens, and only minimal activity was observed.     

Kinetic study on the mechanism of inhibition of trypsin and trypsin-like enzymes by p-guanidinobenzoate ester

It was found that [4-(2-succinimidoethylthio)phenyl 4-guanidinobenzoate]methanesulfonate (E-3123) inhibits trypsin, thrombin and kallikrein, and its inhibitory activity is most potent toward trypsin. The interactions of these enzymes with E-3123 were studied mainly by using stopped-flow spectrophotometry. E-3123 behaved as a quasi-substrate of the enzymes and the inhibitory property was due to the efficient production of the stable acyl-enzyme. The acylation process with trypsin was exceedingly effective, and the resulting acyl-enzyme was the most stable among the three enzymes tested. This observation affords a rational basis for explaining the action of E-3123, which is a transient inhibitor most active toward trypsin.     

Extensive oxygen exchange between carbon dioxide and magnesium oxide surface

Temperature-programmed desorption study of C¹⁸O₂ adsorbed on MgO has revealed that the desorbed carbon dioxide is composed exclusively of C¹⁶O₂, indicating that the adsorbed CO₂ species roll over the MgO surface.     

Determination of tryptophan and its metabolites in human plasma and serum by high-performance liquid chromatography with automated sample clean-up system

An automated high-performance liquid chromatographic method that incorporates direct injection of biological samples followed by chromatographic sample clean-up in a precolumn is described for the determination of tryptophan and its metabolites in human plasma and serum. The system gave reproducible data with a coefficient of variation of less than 3% with a sample size of 100 microliters of human plasma. The major tryptophan metabolites found in 100 microliters of human plasma were kynurenine, indolelactic acid, indoleacetic acid, indolepropionic acid, serotonin and 5-hydroxyindoleacetic acid. The level of tryptophan and kynurenine in individuals was constant in comparison with other metabolites. Analysis of samples from normal controls, diabetics, gravida and their foetuses showed a tendency for tryptophan metabolites to be low in maternal plasma.