X-ray gated Mössbauer spectroscopic studies on57Co-labelled cobalt/II/ fluoride

KX-ray-gated emission Mössbauer spectra of⁵⁷Co-labelled CoF₂ and CoF₂.2H₂O were measured at room temperature, using the coincidence technique. A difference was found in the relative intensity of⁵⁷Fe(II)/⁵⁷Fe(III) between the X-ray-gated and non-gated emission spectra. The results are explained in terms of local radiolytic effects of water of crystallization and the chemical effects associated with the de-excitation processes caused by EC-decay.     

The first synthesis of a methano[60]fullerene with an electron-donating group at the methano-bridge carbon: synthesis and reaction of aminomethano[60]fullerene

[reaction: see text] Aminomethano[60]fullerene was synthesized for the first time as a trifluoromethanesulfonic acid salt by applying the Curtius rearrangement of azidocarbonylmethano[60]fullerene as the key reaction. Aminomethano[60]fullerene thus obtained was found to be able to react with various acyl chlorides to afford the corresponding amides.     

Ion chromatographic separation of hydrogen ion and other common mono- and divalent cations

We introduced an approach to the ion chromatographic determination of common mono- and divalent cations including hydrogen ion and demonstrated the ability of a C30 column dynamically coated first with dodecylsulfate and then with 18-crown-6 ether to separate the cations by ion-exchange mechanism. Using an ethylenediamine solution containing a small concentration of 18-crown-6 ether and lithium dodecylsulfate at pH 6.2 as eluent, the cations were eluted in the order Li < Na+ < NH4+ < H+ < K+ < Mg2+ < Ca2+ with symmetrical peaks. The conductivity vs. concentration plots were linear about three orders of magnitude, from millimolar to micromolar; and the detection limits were all < 0.6 microM. Rainwater was analyzed directly using this ion chromatographic system with satisfactory results.     

Electrochemical analysis of single nucleotide polymorphisms of p53 gene

Single nucleotide polymorphisms (SNPs) of cancer repression gene p53 were analyzed electrochemically with ferrocenyl naphthalene diimide (1) as a hybridization indicator. The SNPs studied were the transition to A from G in the codon for amino acid at positions 175, 248 or 273 and the transversion to C from G in the codon for the amino acid at position 72. Thus, 20-meric oligonucleotides carrying the SNP site were used both as a sample and a probe with the latter immobilized on an electrode. Even one base difference on the p53 gene resulted in a significant difference in the current response of 1 and the magnitude of the response correlated with the amount of the DNA hybrid on the electrode. Moreover, when PCR products of exon 4, on which the P72/R72 SNP resides, of the p53 gene were analyzed by this method, the heterozygote and homozygotes were discriminated with modest precision.     

Noncatalytic kinetic study on site-selective H/D exchange reaction of phenol in sub- and supercritical water

The site-selective H/D exchange reaction of phenol in sub- and supercritical water is studied without added catalysts. In subcritical water in equilibrium with steam at 210-240 degrees C, the H/D exchange proceeds both at the ortho and para sites in the phenyl ring, with no exchange observed at the meta site. The pseudo-first-order rate constants are of the order of 10(-4) s(-1); 50% larger for the ortho than for the para site. In supercritical water, the exchange is observed also at the meta site with the rate constant in the range of 10(-6)-10(-4) s(-1). As the bulk density decreases, the exchange slows down and the site selectivity toward the ortho is enhanced. The enhancement is due to the phenol-water interaction preference at the atomic resolution. The site selectivity toward the ortho is further enhanced when the reaction is carried out in benzene/water solution. Using such selectivity control and the reversible nature of the hydrothermal deuteration/protonation process, it is feasible to synthesize phenyl compounds that are deuterated at any topological combination of ortho, meta, and para sites.     

Asymmetric selective polymerization of racemic methacrylates with the cyclohexylmagnesium bromide-(−)-sparteine system

Asymmetric selective (or stereoelective) polymerization of various racemic methacrylates with cyclohexylmagnesium bromide (c-HexMgBr)-(-)sparteine (1/1.2) catalyst was studied in toluene at ?78°C. The methacrylates of α-ethylbenzyl (EBMA), α-isopropylbenzyl (i-PBMA), α-tert-butylbenzyl (t-BBMA), sec-butyl (s-BuMA), 1-methylallyl (1-MAMA), 2,3-epoxypropyl (2,3-EPMA), 2-phenylpropyl (2-PPMA), and menthyl (MentMA) alcohols were used as racemic monomers. In the polymerization of EBMA and i-PBMA (S) enantiomers were consumed preferentially and the optical purity of initially polymerized i-PBMA was as high as 97%. Optically pure (R) monomers were recovered at about 60% conversion for i-PBMA and 80% for EBMA. In t-BBMA, however, the (R) monomer was consumed preferentially over the (S) isomer. In the polymerization of s-BuMA and 1-MAMA (S) monomers were consumed in excess and the optical purity of the polymers formed in the early stage was about 30%. In 2,3-EPMA and 2-PPMA, which have asymmetric centers at the β position from the ester oxygen, (R) antipodes were more reactive. MentMA did not polymerize at ?78°C. Enantiomer selectivity ratios r_S and r_R were determined in the polymerization of EBMA, i-PBMA, and 1-MAMA. All polymers except poly(t-BBMA) were highly isotactic, but the tacticity of poly(t-BBMA) could not be estimated. Circular dichroism spectra of optically active polymers of α-substituted benzyl esters were measured.     

Coulometric argentometric determination of microamounts of sulphur in iron and steel after reduction to hydrogen sulphide with iron(II) in strong phosphoric acid medium

A coulometric method was developed for the determination of microamounts of sulphur in iron and steel. Hydrogen sulphide is quantitatively evolved by reduction with iron(II) in strong phosphoric acid medium and is titrated with electrolytically generated silver ion from a silver anode. Microamounts of sulphide (2.96–224.3 μg) in sodium sulphide standard solutions could be determined with an error of only a few percent. Sulphur in a potassium sulphate standard solution is quantitatively reduced to hydrogen sulphide and could be separated from the solution by heating and determined accurately. Trace amounts of sulphur (7–100 μg g^?1) in iron and steels could be determined with a standard deviation of 0.7–2.1 μg g^?1.     

Recent progress in the solid-phase synthesis of glycopeptide

The recent understanding of the biological role of glycoproteins has brought about a demand for the highly homogeneous glycopeptides as the functional model for glycoproteins. Thus, much efforts have been made to establish easy and efficient method for glycopeptide synthesis. In this paper, we briefly review the recent advances in the synthesis of O- and N-linked glycopeptide based on the solid-phase method. In O-glycopeptide section, the preparation of glycosylated amino acid units with mucin type and other O-linked carbohydrate chains and their use for solid-phase synthesis are summarized. Other approaches, such as the glycosylation of resin bound peptide are also overviewed. In N-glycopeptide section, the synthesis using glycosylated amino acid units as well as other methods are described.     

Simultaneous operation of plural separation modes in capillary electrophoresis with a chemiluminescence detector possessing a micro-space area for reaction/detection

Analysis of alpha-amino acids, proteins, and phenolic compounds was simultaneously performed using three capillaries in capillary electrophoresis with chemiluminescence detection, taking advantage of the micro-space area for reaction/detection at the tip of the capillary. The three capillaries included usual, polymer-containing, and sodium docley sulfate (SDS)-containing migration buffers for separation. The eluted samples from the capillaries, which were inserted into the chemiluminescence detection cell, were mixed with chemiluminescence reagent at the tips of the capillaries to generate visible light. The specific micro-space area for reaction/detection at the tips of the capillaries enabled the simultaneous operation of the three separation modes in the present system.