Direct injection analysis of ketoprofen enantiomers in plasma using column-switching high-performance liquid chromatography system

A high-performance liquid chromatography system was developed for the stereoselective determination of ketoprofen enantiomers in human plasma following direct sample injection. The system comprised of a pretreatment column and a chiral separation column connected in a series via a switching valve. When a 200 microliter portion of human plasma containing a therapeutic level of ketoprofen was directly applied to the system, ketoprofen was adsorbed in the pretreatment column, while plasma proteins were excluded. After the elution of proteins from the pretreatment column, the valve was switched and ketoprofen was desorbed and transferred to the chiral separation column where the enantiomers were separated and determined by ultraviolet-absorption. The mobile phase conditions for the pretreatment and chiral separation were optimized, which enabled rapid and complete recovery followed by satisfactory separation of the enantiomers. The calibration line for each enantiomer showed good linearity in the range of 0.25-5 micrograms/ml with a detection limit of 0.02 micrograms/ml (signal to noise ratio (S/N) greater than 3), which was sufficient for practical demands. The precision test indicated that the coefficient of variation for five repeated determinations of (-) ketoprofen was 5.4% at 0.1 microgram/ml and 1.4% at 1 microgram/ml.     

Design and synthesis of a novel water-soluble Aβ1-42 isopeptide: an efficient strategy for the preparation of Alzheimer's disease-related peptide, Aβ1-42, via O-N intramolecular acyl migration reaction

A novel water-soluble isopeptide of Alzheimer's disease-related peptide Aβ1-42, `26-O-acyl isoAβ1-42', which could efficiently convert to intact Aβ1-42 under physiological conditions via O-N intramolecular acyl migration, was synthesized providing a new system useful for investigation of biological function of Aβ1-42.     

Determination of strontium in biological materials by charged-particle activation analysis using the stable isotope dilution method

In order to apply the stable-isotope dilution method to charged-particle activation analysis, determination of strontium in biological materials has been studied by proton activation using isotopically enriched⁸⁶Sr as a spike. To avoid thermal decomposition of biological materials due to the low penetrating power of proton beam, and to eliminate interfering nuclear reactions due to the matrix elements, strontium in the sample and/or isotopic mixture as a comparator was separated chemically together with most of calcium before bombardment, and the fraction isolated was converted to a silica-gel pellet as a most suitable physical and chemical form for bombardment. By processing as above, it was demonstrated that the strontium contents in the biological materials can be determined accurately, precisely and easily. Through a series of experiments, the method was also proved to be applicable for charged-particle activation analysis.     

A new internal conversion spectrometer and its characteristics

A new internal conversion electron spectrometer with high energy resolution has been developed using a windowless Si(Li) detector, and its characteristics are examined and discussed. As a result, it is confirmed that the energy resolutions are 0.48 keV in FWHM for 42 keV electrons and 1.43 keV for 624 keV electrons, respectively.     

1,6-Dihydro-3 (2H)-pyridinones as synthetic intermediates. Formal synthesis of (±)-tabersonine and (±)-catharanthine

Formal synthesis of (±)-tabersonine (3) and (±)-catharanthine (4) has been achieved starting from ethyl 1,6-dihydro-3 (2H)-pyridinone-1-carboxylate (1a) as a common synthon.     

Molecular design, characterization, and application of multiinformation dyes for optical chemical sensing: IV. Multiinformation dyes with extended spectral sensitivity in the near-infrared spectral range

In this paper, new “multiinformation dyes” (MIDs) with extended spectral sensitivity reporting on both changes in solvent polarity (solvatochromism) and in pH (halochromism) by changes in their visible absorption spectra, are presented. The merocyanine dyes 2,6-dibromo-4-[4-(1-dodecyl-4(1H)-pyridinylidene)-2-butenylidene]-2,5-cyclohexadien-1-one (KD-M301) and 2,6-dibromo-4-[4-(1-dodecyl-4(1H)-quinolinylidene)-2-butenylidene]-2,5-cyclohexadien-1-one (KD-M402) were designed, synthesized, and characterized regarding analytical applications. The spectral sensitivity for the MIDs was extended into the near-infrared (NIR) wavelength range (λ_max=800 nm in CHCl₃ for KD-M402) and at the same time, the degree of solvent polarity-induced spectral shifts was strongly enhanced (Δλ_max=202 nm for KD-M402 between tetrahydrofuran (THF) and methanol), reaching similar values to the standard solvatochromic dye Dimroth-Reichardt’s betaine on which the empirical E_T(30) classification of solvent polarity is based. Compared to Dimroth-Reichardt’s betaine dye, the molar absorption coefficient ε, is increased more than 10-fold (ε of KD-M402 in THF: 7.7×10⁴ M⁻¹ cm⁻¹), allowing sensitive measurements at low concentrations of the dye. The dodecyl-substituted KD-M402 is suitable as a lipophilic pH indicator in ion-exchange type optical sensors (optodes) with optical detection in the near-infrared wavelength range.     

Light-controlled gas permeability of mesoporous silica glass bearing photochromic spironaphthoxazine on its surface

N2 and CO2 gas permeability of mesoporous silica glass bearing photochromic indolinospironaphth[2,1-b][1,4]oxazine through a covalent linkage was controlled by photo-irradiation: the photo-isomerization of the spironaphthoxazine to the photomerocyanine form suppressed the gas permeation of the glass.     

Purification and characterization of adenosine diphosphatase from human umbilical vessels.

Adenosine diphosphatase (ADPase) activity was solubilized with a non-ionic detergent, Tween 20, from human umbilical vessels and purified to homogeneity by diethylaminoethyl-Sepharose CL-6B, adenosine 5'-monophosphate-Sepharose 4B, and concanavalin A-Sepharose chromatography. The apparent molecular mass was 75 kDa. The purified enzyme hydrolyzed pyrophosphate bonds of nucleoside di- and triphosphates in the presence of calcium ion. It was insensitive to the adenosine triphosphatase (ATPase) inhibitors, oligomycin and ouabain, and sensitive to sodium azide. Therefore, we concluded that the ADPase activity in human umbilical vessels does not derive from ADPase degrading only ADP but from ATP diphosphohydrolase (EC 3.6.1.5). The broad substrate specificity and the sensitivity to various inhibitors and calcium ion are common to ATP diphosphohydrolase from bovine aorta. However, there might exist some structural difference around the active site, because the antiserum raised in rabbit against the bovine aorta enzyme scarcely inhibited the human umbilical enzyme.     

Instrumental photon activation analysis of soil samples using the internal standard method coupled with the standard addition method

Multielement determinations in the certified reference materials of soils (IAEA soil-5 and 7) have been studied fundamentally by instrumental photon activation analysis using the internal standard method coupled with the standard addition method. For the soil-5 sample, in the first place, the qualities of the comparative standards prepared by two processing methods were compared with each other. As a result, it was demonstrated that a highly accurate and precise multielement determination can be achieved easily by minor improvement in the processing method of the comparative standard to ensure homogeneity. The utility of this processing method for soil samples was proved further through a similar analysis in another soil sample (IAEA soil-7).     

Reaction of alpha,alpha-dibromo oxime ethers with Grignard reagents: alkylative annulation providing a pyrimidine core

A convergent synthesis of a pyrimidine core has been achieved. Treatment of alpha,alpha-dibromo oxime ethers, which are easily derived from the corresponding esters, with a variety of Grignard reagents provides trisubstituted pyrimidines in good yields. This new method offers an easy access to functionalized pyrimidines.