English
J. Mass Spectrom. Soc. Jpn., 49(5), 175-182, 2001
A numerical spectral-deconvolution method with an autoregressive (AR) model is proposed to overcome a noise problem that limits resolution-enhancement ability of a traditional Fourier-transform (FT) deconvolution. The optimal AR-model is determined by a new criterion that uses similarity between measured and reconstructed spectra. Additionally, unreliable peak-heights appearing in an AR power-spectrum are corrected by using its convolution with a Gaussian function with a small width. The proposed method was applied to noisy and low-resolution spectra of a bio-molecule, and found to be useful for determination of its monoisotopic mass.
English
J. Mass Spectrom. Soc. Jpn., 49(5), 183-187, 2001
The photo ligand substitution reaction of the bisphenanthroline complex [Ru(phen)2B]2+ (where phen=1,10-phenanthroline, B=ethylenediamine (en), trimethylenediamine (tn), or butanediamine (bn)) in acetonitrile solution was studied using electrospray ionization mass spectrometry (ESI-MS). The photochemical reaction of a diamineruthenium(II) complex has been known to proceed by oxidation of a diamine ligand to an a,a'-diimine by oxidative dehydrogenation. The final reaction product was a solvent substituted complex [Ru(phen)2S2]2+, where S is the solvent acetonitrile. We detected two monodentate complexes, an imine complex [Ru(phen)2-(B-2)S]2+ and a nitroso complex [Ru(phen)2(en+14)S]2+ in the ESI-MS analysis of the photoreaction products of [Ru(phen)2B]2+. These monodentate complexes were not observed with a bipyridine complex [Ru(bpy)2B]2+ (where bpy=2,2'-bipyridine, B=en or tn). In addition, photochemical reactivity of the phen complex was found to be higher than that of the bpy complex. The difference in the photochemical reactivity can be explained by the difference in configurational flexibility of the phen and bpy ligands in the ruthenium complexes.
English
J. Mass Spectrom. Soc. Jpn., 49(5), 188-194, 2001
The gas-phase ion-molecule reactions of CH5+, C2H5+, and C3H5+ with five monosubstituted benzenes (M) carrying a nitrogen atom in the substituent [PhX: X=NH2, NHCH3, N(CH3)2, NO2, CN] have been reinvestigated under a reactant-ion selective mode of an ion-trap type of GC/MS. The dependence of product-ion distributions on the reaction time indicated that collisional stabilization takes part in the formation of all adduct (M+C2H5)+ and (M+C3H5)+ ions. It was found that radiative association also participates in the formation of adduct (PhNH2+C3H5)+ and (PhCN+C3H5)+ ions. The initial product-ion distributions were determined by extrapolating the dependence of branching ratios of product ions on the reaction time to zero reaction time. The reaction mechanism was discussed based on initial product-ion distributions and heats of formation of each reaction pathway.
English
J. Mass Spectrom. Soc. Jpn., 49(5), 195-200, 2001
The intact total lipid from Sulfolobus sp. (99.9% identical to Sulfolobus shibatae by comparison of 16SrRNA) was examined by electrospray ionization/time of flight mass spectrometry (ESI/TOF MS) in negative ion mode with high-resolution. Solution of the total lipid in a mixed solvent of chloroform and methanol (1 : 3) was injected into the ion source using a loop injection system with an infusion pump. Some ions directly corresponding to phospho- and sulfo-ether lipids isolated from Sulfolobus acidocaldarius were detected. The ions between m/z 1,532 and 1,546 were assigned to phospholipid (PL1), the ions between m/z 1,840 and 1,847 to sulfolipid (SGLII), and the ions between m/z 1,856 and 1,865 to phospholipid (PGLI and/or PGLII). Each group of ions was analyzed as the mixture of the ether lipids containing different number of five-membered ring in the isoprenoid chain with their isotope peaks. Examination of the ether lipids of the bacteria cultivated at different temperatures (65°C and 75°C) indicated that (1) the molecule having four five-membered ring was the major component in the tetraethers; (2) the maximum number of five-membered ring in the tetraethers was six at both growth temperatures; (3) the number of five-membered ring extends toward smaller numbers on cultivation at the lower temperature.
Japanese, English Abstract
J. Mass Spectrom. Soc. Jpn., 49(5), 201-206, 2001
The effect of vibrational supercooling in supersonic molecular beam (SMB) on the electron impact mass spectrometry (EIMS) was demonstrated for a number of organics, (i) hydrocarbons, (ii) monoterpenes, and (iii) fatty acid esters. With SMB/EIMS, all of these compounds showed enhanced molecular ion intensities whereas the fragment ion intensities were greatly suppressed. Effect of electron impact energy was also examined. With increase in electron energy, fragment ion intensity increased for (i) hydrocarbon and (ii) aliphatic alcohol, whereas fatty acid methyl ester showed opposite behavior. At 20 eV, peak intensities of McLafferty rearrangement (m/z 74) and molecular ion were 100% and 55%, respectively, whereas at 70 eV, they were 25% and 100%, respectively. Sensitivity for GC/MS mode was also examined.
Japanese, English Abstract
J. Mass Spectrom. Soc. Jpn., 49(5), 207-210, 2001
Periodicity of the cosmic-ray exposure ages has been recognized for the 3He-deficient iron meteorites. These irons might have been thrown away from the Asteroid Belt to the orbits close to the Sun. The intervals are similar to the orbital period of the Sun (
230 My) around the center of the Galaxy. Therefore, the periodicity of the exposure ages may be caused by the periodic perturbation of the Asteroid Belt due to the extrasolar stars. The exposure ages of IAB iron meteorites also reflected the periodic perturbations of the Asteroid Belt. The detailed studies of exposure history of IAB iron meteorites may reveal the history of the perturbations.
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