Preparation and Mössbauer effect of Cr1−xFexOOH (0 ≦ x ≦ 1.0) with the InOOH-type structure

The complete solid solutions of Cr_1?xFe_xOOH with the InOOH-type structure were synthesized under high pressures. They were antiferromagnetic with Néel temperatures of 570 K for FeOOH, 454 K for Cr_0.2Fe_0.8OOH, 332 K for Cr_0.4Fe_0.6OOH, and 160 K for Cr_0.6Fe_0.4OOH as determined by the Mössbauer effect measurements.     

Determination of sulfates of androsterone and epiandrosterone in human serum using isotope diluted liquid chromatography-electrospray ionization-mass spectrometry

A promising liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) for analysis of the sulfates of 5alpha-androgen, androsterone and epiandrosterone (A-S and EpiA-S) in human serum was developed. The method was used to assess one of the markers of 5alpha-reductase activity of males including patients with prostate cancer (PC). After deproteinization with acetonitrile, the androgen sulfates and the internal standard, [7,7,16,16-2H4]dehydroepiandrosterone-S, were extracted from human serum using a solid-phase extraction cartridge and washed with hexane. The extract was reconstituted and applied to the LC/ESI-MS system operated in the selected ion monitoring mode. The method was validated over the range 0.02-5 microg/mL (A-S) and 0.005-1.5 microg/mL (EpiA-S) using 10 microL of human serum. The method was a concise procedure without chemical or enzymatic hydrolysis of the conjugates, purification by high-performance liquid chromatography and/or derivatization, and proved to be satisfactory in its reproducibility and accuracy. The levels of these androgen sulfates tended to decrease during aging, and the A-S levels in the sera obtained from both healthy males and patients with PC were correlated with their EpiA-S levels.     

Determination of 24,25-dihydroxyvitamin D(3) in human plasma using liquid chromatography-mass spectrometry after derivatization with a Cookson-type reagent

A practical LC-MS method for determination of (24R)-24,25-dihydroxyvitamin D(3) [24,25(OH)(2)D(3)] in human plasma has been developed using derivatization with a Cookson-type reagent, 4-[4-(6-methoxy-2-benzoxazolyl)phenyl]-1,2,4-triazoline-3,5-dione (MBOTAD). The derivatization with MBOTAD significantly improved the ionization efficiency of the analyte with a detection limit of 18 fmol [equivalent to 7.5 pg of 24,25(OH)(2)D(3)] per injection. The method employed protein precipitation with acetonitrile, purification with OASIS HLB cartridge and silica gel column, derivatization with MBOTAD and atmospheric pressure chemical ionization MS detection. The mass spectrometer was operated in the positive-ion mode of mass chromatography and [26,26,26,27,27,27-(2)H(6)]-24,25(OH)(2)D(3) was used as an internal standard. The intra- and inter-assay coefficients of variation were below 3.4 and 2.5%, respectively, and the analytical recovery of 24,25(OH)(2)D(3) was quantitative. Assay linearity was obtained in the range of 0.05-1.2 ng per tube and the limit of quantitation was 0.23 ng/mL for a 0.3 mL plasma aliquot. The developed method was applied to plasma samples obtained from volunteers and gave satisfactory results.     

XPS studies on the chemical structure of the stabilized polyacrylonitrile fiber in the carbon fiber production process

In the carbon fiber production process from polyacrylonitrile (PAN), PAN precursor is heated first in air to secure stabilization in the succeeding carbonization process at higher temperature. The mechanism of the stabilization reaction and chemical structure of the stabilized PAN have been examined by x-ray photoelectron spectroscopy and elemental analysis. The stabilized PAN was determined to have a ladderlike structure consisting of 40% acridone ring, 30% naphtyridine ring, 20% hydronaphtyridine ring, and others. This structure well explains the stability of the polymer in the succeeding carbonization process on carbon fiber production with conjugated π-electron systems over the whole polymer chain and intermolecular hydrogen bonds. A comonomer addition to the precursor was found to accelerate the dehydrogenation reaction in the stabilization process.     

FT-IR study of the stabilization reaction of polyacrylonitrile in the production of carbon fibers

The stabilized fibers prepared by heating PAN and a PAN copolymer in air and under reduced pressure have been examined by FT-IR spectroscopy in order to determine their chemical structures. Three kinds of reactions, cyclization, dehydrogenation, and oxygen uptake are found to occur almost simultaneously in the stabilization process in air by digital difference spectrum method. The effect of the comonomer is confirmed to accelate the dehydrogenation reaction and also the formation of acridone ring in the thermal stabilization in air by kinetic study.     

Conductive characteristics of radical‐bearing polythiophenes using a microcomb‐shaped electrode

The electric conductivity of π‐conjugated and radical‐bearing polymers, i.e., polythiophenes bearing pendant galvinoxyl and phenoxyl radical groups, was measured using a microcomb‐shaped electrode. The electric conductivity was found to be enhanced by the radical content in the polymer. The infrared (IR) and Raman spectroscopies suggested a structural change from an aromatic form to a quinoid one in the polythiophene backbone by the phenoxyl radical generation. The effect of the pendant galvinoxyl radical's unpaired electron on the electric conductivity of the polythiophene was discussed by comparing the conductivity of a radical‐bearing polystyrene and a polythiophene mixed with low‐molecular radical molecules. Copyright © 2007 John Wiley & Sons, Ltd.     

Development of Odorless Thiols and Sulfides and Their Applications to Organic Synthesis

Summary. Development of new odorless thiols (dodecanethiol, 4-n-heptylphenylmethanethiol, 4-trimethylsilylphenylmethanethiol, 4-trimethylsilylbenzenethiol) and an odorless sulfide (1-methylsulfanyldodecane) and their applications to dealkylation, Michael addition, Swern oxidation, and Corey-Kim oxidation are described.     

Studies on steroids. CC. Determination of 17-ketosteroid sulphates in serum by high-performance liquid chromatography with electrochemical detection using pre-column derivatization

A new sensitive method is described for the determination of 17-ketosteroid sulphates, particularly dehydroepiandrosterone sulphate, in human serum by high-performance liquid chromatography with electrochemical detection. The 17-ketosteroid sulphates in serum were extracted with acetonitrile and derivatized with p- nitrophenylhydrazine in trichloroacetic acid--benzene solution. The p- nitrophenylhydrazones were separated by high-performance liquid chromatography on a mu Bondapak C18 column using methanol--0.5% ammonium dihydrogen phosphate (8:3) as a mobile phase. The proposed method proved to be applicable to the quantitation of 17-ketosteroid sulphates with satisfactory sensitivity and reliability, providing a quantitation limit of 80 ng/ml and coefficient of variation of 4%. A good correlation was observed between the values obtained by the present method and radioimmunoassay for dehydroepiandrosterone sulphate in serum.     

Effects of diazepam administration on melatonin synthesis in the rat pineal gland in vivo.

The effect of diazepam (DZP) on melatonin synthesis in rat pineal gland was investigated in vivo. Subcutaneous injection of DZP (3 mg/kg) 1 h before the start of darkness significantly suppressed nocturnal elevations of pineal N-acetylserotonin (NAS) and melatonin contents in rats, and caused a 2-h delay in reaching the maximum melatonin level in the dark phase. DZP treatment also markedly suppressed the dark-induced increase of pineal N-acetyltransferase activity, which catalyzes the rate-limiting step in melatonin synthesis, but had no effect on hydroxyindole-O-methyltransferase activity, which catalyzes the final step of melatonin formation. Pineal norepinephrine and dopamine contents, in contrast, were not altered by DZP injection. The distribution rate of DZP to the brain reached the highest level 30 min after a single injection, while that to the pineal gland was observed 5 h later (i.e., 4 h after the start of darkness). It is clear that the inhibitory effect of DZP on melatonin synthesis in rat pineal gland appears concomitantly with the increase in the distribution volume of DZP into this gland. These results suggest that the inhibitory effect of DZP on melatonin synthesis results from the drug's direct action on the rat pineal gland.