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71.
72.
Moriyasu T Minowa K Sakamoto M Kishimoto K Kadoi H Nakajima J Mori K Ogino S Fukaya H Shida Y 《Journal of AOAC International》2011,94(6):1770-1777
An analog of aildenafil, which is a potent and highly selective inhibitor of phosphodiesterase 5, was found in a dietary supplement marketed for enhancement of sexual function. The compound was isolated by silica gel column chromatography, and its structure was identified by means of 13C-NMR spectrometry, 1H-NMR spectrometry, high-resolution MS, and X-ray structure determination. The compound was identified to be sulfoaildenafil (other names: thioaildenafil, dimethyl sildenafil thione, and thiomethisosildenafil). Sulfoaildenafil is very similar to the compound thiohomosildenafil. As it is difficult to distinguish between them by LC-photodiode array detector analysis, ultra-performance LC (UPLC)/MS, ion trap LC/MS/MS (LC/IT-MS/MS), and GC/MS were performed. The mass spectra of thiohomosildenafil by UPLC/MS and LC/IT-MS/MS showed mass fragments of m/z 58, 72, and 355, and the mass spectrum by GC/MS showed mass fragments of m/z 56, 72, and 420. Some of these fragments had low intensities, but they were useful for distinguishing between the two compounds. The relationship between aildenafil (other names: dimethylsildenafil and methisosildenafil) and homosildenafil is similar to that between sulfoaildenafil and thiohomosildenafil. Therefore, these compounds were also examined. 相似文献
73.
An example of an SDP (semidefinite program) exhibits a substantial difficulty in proving the superlinear convergence of a direct extension of the Mizuno—Todd—Ye type predictor—corrector primal-dual interior-point method for LPs (linear programs) to SDPs, and suggests that we need to force the generated sequence to converge to a solution tangentially to the central path (or trajectory). A Mizuno—Todd—Ye type predictor—corrector infeasible-interior-point algorithm incorporating this additional restriction for monotone SDLCPs (semidefinite linear complementarity problems) enjoys superlinear convergence under strict complementarity and nondegeneracy conditions. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V. 相似文献
74.
We deal with finite dimensional differentiable optimization problems under linear constraints. Stability of stationary solutions under restricted perturbations of the constraints will be characterized. The restriction on the constraint perturbations is given by means of a certain rank condition; in particular, righthandside perturbations are allowed.Corresponding author. 相似文献
75.
Received April 15, 1997 / Revised version received July 22, 1998 Published online November 24, 1998 相似文献
76.
77.
A simple and precise preconcentration technique, based on collecting a precipitate on a membrane filter and dissolving the filter and precipitate in an organic solvent, has been applied to the spectrophotometric determination of trace sulphate in rain and snow. The sulphate is precipitated with 2-aminoperimidine and the resulting compound is dissolved in nitric acid, made alkaline with sodium hydroxide and then adsorbed on tetradecyldimethylbenzylammonium nitrate. The precipitate is then collected on a membrane filter and both precipitate and filter are dissolved in dimethylsulphoxide (DMSO). The absorbance of the DMSO solution is measured at 550 nm against a reagent blank. The molar absorptivity is 2.1 x 10(4) 1 . mole(-1) . cm(-1) and the coefficient of variation for six measurements is < 1.5%. The detection limit (S/N = 3) is 0.06 mug of sulphate in 5 ml of sample solution. 相似文献
78.
Conformational isomerizations of radical-ions are studied both experimentally and theoretically- The representative systems of stilbenes, polyenes, and non-planar alicyclic compounds will be reviewed first. Then, the result of the study on the radical-cations of 1,4-dithiacyclohexane and ethane-1,4-dithiol will be presented. It is found that the former cation suffers a change from a chair fore to a boat form and the latter from an anti- or a gauche-form to a cis form even in a rigid matrix. The conformational changes are manifested by drastic changes in the electronic absorption and ESR spectra- The strong “through-space” interaction between the lone pair orbitals of the sulfur atoms is responsible for the conformational changes. Ab initio óó'O calculations lend support to the analysis of the experimental results. 相似文献
79.
Ab initio calculations were performed to study the molecular structures and the vibrational levels of the low-lying ionic states (2B1, 2A1 and 2B2) of hydrogen sulphide. The equilibrium molecular structure and the vibrational analysis of these states are presented. The normal vibrational calculations at the RHF level and more extensive calculations at the SDCI level using the explicit vibrational Hamiltonians were used for the vibrational analysis. The theoretical ionization intensity curves including the vibrational structures of these ionic states are also presented and compared with the photoelectron spectrum. The results show that the global shape of the potential energy surface has to be taken into consideration in order to analyze the 2A1 and 2B2 states. A new assignment of the photoelectron spectra of H2S is proposed. 相似文献
80.
Ichiyanagi T Kashiwada Y Ikeshiro Y Hatano Y Shida Y Horie M Matsugo S Konishi T 《Chemical & pharmaceutical bulletin》2004,52(2):226-229
Capillary zone electrophoresis (CZE) mobilities of fifteen anthocyanins in bilberry extract were completely characterized. Four minor anthocyanins in bilberry extract (malvidin 3-O-alpha-L-arabinopyranoside (Mv 3-ara), peonidin 3-O-beta-D-galactopyranoside (Pn 3-gal), peonidin 3-O-alpha-L-arabinopyranoside (Pn 3-ara), and petunidin 3-O-alpha-L-arabinopyranoside (Pt 3-ara)) that remained unidentified in our previous CZE study were isolated from the bilberry extract, and the chemical structures were assigned by NMR and MS. Their CZE mobilities were then precisely examined together with those of other major anthocyanins in the extract. When the CZE mobilities of the fifteen anthocyanins assigned here were plotted against their molecular weight/numbers of free phenolic group, it was found that separation of anthocyanins by CZE is primarily determined by the type of conjugated sugar present, and secondly by the aglycon structure. 相似文献