摘要:

AbstractThe analysis of reaction products in methylation of four dinucleoside monophosphates (ApA, UpU, ApU, UpA) by FDMS is reported. Both the relative amounts of the various methylation products and the sites of methylation could be determined, the latter from the fragmentation patterns. The results are explained by the different reaction rates of the nucleoside moieties.

ISSN:0021-2148    

DOI:10.1002/ijch.197800026

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractIn oligomers, a structure element is repeated periodically. If a fragmentation pathway in the mass spectrometer is detectable arising from such a periodicity of structure, an analysis of the sequence of monomers is possible. This is the case in oligopeptides. Tracing the generation of consecutive ions stepwise by DADI‐MS leads successfully to the sequence of amino acids in tripeptides. This is demonstrated by different examples containing simple and more complex amino acid

ISSN:0021-2148    

DOI:10.1002/ijch.197800027

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractIn the FD–MS of oligosaccharide derivatives by the cationization method, the influence of the nature of the cation was studied so as to observe either monomeric doubly or singly charged ions. Trehalose was used as a model for this study. The use of alkaline‐earth salts does not allow the desorption of doubly charged monomeric ions. These ions are formed during the desorption of mixtures of trehalose and NaI, but the narrowness of their desorption temperature range limits the applicability of the method. Monomeric cationized ions are formed with alkaline cations: cesium iodide seems to be a suitable cationizing reagent as regards the appearance‐emitter temperature, the width of the desorption temperature range, and the sensitivity. The FD/Cs spectra of several diacyl trehaloses are presented. The desorption of a synthetic “cord factor” (dimycoloyl trehalose) containing 100 carbon atoms produces an intense peak at the expected m/e value for the (M + Cs) ions. The spectrum of the natural “cord factor” fromCorynebacterium diphtheria

ISSN:0021-2148    

DOI:10.1002/ijch.197800028

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe mass spectra of the new piperidyl‐PGA (TMS), derivatives, formed by reaction of prostaglandin A1or A2with BSTFA/piperidine, are characterized by a dominant M − 173 ion, remarkably specific for MID applications. Similar derivatives have also been obtained with mixtures of BSTFA and other heterocyclic amines (hexamethylenimine, pyrrolidine, morpholine and propylenimine), which give the respective heterocycle‐PGA (TMS), derivatives. Likewise, the corresponding 11‐piperidyl‐19‐OH‐PGA (TMS)4seem specially suited for the selected ion detection of PGA “artifacts” in extracts of human semen. The postulated structure of fragments at M − 173 and M − 423 (series I) and M − 425 (series II) is in favour of a pushpull type of reaction mechanism leading to these derivatives by nucleophilic addition of the amine on the C‐11 atom of the PGA's and concurrent formation of an enolate ion from the 9‐keto group with silanization of all reactive groups by BSTFA. An example of an application to the determination of PGA's and 19‐OH‐PGA's i

ISSN:0021-2148    

DOI:10.1002/ijch.197800029

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractA Laser Microprobe Mass Analyser (LAMMA) has been developed for the analysis of microscopically small volumes (10−11–10−13cm3) of thin organic specimens (0.1–1 μm). Detection limits for most of the organic ions are in the range of 10−17–10−20g corresponding to 0.1–10 ppm. The instrument is based on the combination of a light microscope for observation and exact localisation of the sampled volume within the morphological structures of the specimen as well as for focusing the beam of a pulsed laser onto the specimen. The ions of the laser‐generated microplasma are analysed with a time‐of‐flight mass spectrometer. Mass spectra of organic standard samples and heart muscle cells are

ISSN:0021-2148    

DOI:10.1002/ijch.197800030

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractAmaryllidaceae alkaloids have been isolated from the bulbs ofCrinum ornatumandCrinum natansand studied by a combination of mass spectral techniques including EI, CI, FD and GLC/EI mass spectrometry. In addition to the abundant lycorine present in both species three new alkaloids have been obtained in crystalline form fromC. ornatumand one new crystalline alkaloid fromC. natans. Several other new alkaloids were also shown to be present by GLC/MS and FD/MS. Tentative structures are proposed for the new alkaloids fromC. ornatumbased on mass and NMR spectral evidence.

ISSN:0021-2148    

DOI:10.1002/ijch.197800031

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe electron impact mass spectra of the epimers 3β‐dimethylamino‐3α‐methyl cholestane and 3α‐dimethylamino‐3β‐methyl cholestane are different. The favoured loss of a methyl radical from the latter (further enhanced at low ionization voltage) is attributed to the predominance in the molecular ions of this compound, of one rotational isomer in which the nitrogennorbital is antiparallel with the C3‐methyl bond. The mass spectra of the corresponding primary and secondary amines confirm this interpretation. These results show the role of the configuration of the amino‐group in the fragmentation and the existence of rotational isomers i

ISSN:0021-2148    

DOI:10.1002/ijch.197800032

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe relative stabilities of stereoisomers in the vitamin D3series were established using the appearance — ionization energies differences obtained for the main fragmentation processes characteristic of these compounds. The influence of (Z)‐and (E)‐configurations of the 5,6‐double bonds in vitamin D3stereoisomers on the previtamin D ‐ vitamin D equilibrium in gas phase, have been als

ISSN:0021-2148    

DOI:10.1002/ijch.197800033

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe value of direct chemical ionization mass spectrometry in combination with electron impact for both screening and confirmation purposes has been demonstrated. It was found to be an analytical tool for the identification of drugs and related compounds.

ISSN:0021-2148    

DOI:10.1002/ijch.197800034

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractA rapid procedure was devised for analyzing anticonvulsants in serum by chemical ionization mass spectrometry. Samples were volatilized by heat into the ion source of the mass spectrometer and reacted there with CH5+and other reactant ions produced by ion‐molecule reactions of the methane reagent gas. Increasing the temperature of the probe produced quasimolecular ion peaks of the different drugs, which rose and fell on the oscilloscope tracing at overlapping rates, indicating similar but not identical rates of volatilization. These peaks were recorded by connecting the electron multiplier ion detector output through a voltage to frequency converter to a 200 channel multichannel analyzer (MCA) operated in the multiscale mode. The concentration of the anticonvulsants were then calculated from the ratio of the counts in the channel of the drug to that of the appropriate internal standard. Other drugs present, including barbiturates, carbamazepine, ethosuximide and caffeine were readily identified when present. With one solid probe inlet, an assay could be performed every two minute

ISSN:0021-2148    

DOI:10.1002/ijch.197800035

出版商:WILEY‐VCH Verlag    

年代:1978

数据来源: WILEY