摘要:

AbstractIdentifying complementary pairs of fragment ions, b‐type vs y‐type, is a key step in mass spectral sequencing of proteins without degradation prior to ionization. Observations that b‐type ions tend to be less stable than y‐type have been extended to carbonic anhydrase (29kDa) as a model protein. Infrared multiphoton dissociation (IRMPD) of 24+, 27+, 30+ molecular ions shows y‐type ions from complementary pairs require, on average, 27% longer irradiation times for onset of abundance decrease, while in nozzle/skimmer dissociation of all charge states, y‐type ions require a 20% higher potential difference. In some cases, b‐ion dissociation appears to accompany its formation, as its rate of increase with increasing energy deposition is far less than that of its

ISSN:0951-4198    

DOI:10.1002/rcm.1290091002

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractThe application of aqueous matrices to fast‐atom bombardment mass spectrometry enables the detection of several organogermanium compounds as specific complexes with matrices. In the positive‐ion mode, the organogermanium compounds showed a dominant ion [M+matrix‐3 · H2O+H]+whose dehydration involved atoms attached to the germanium atom. On the other hand, two types of fragmentation were observed in the negative‐ion mode The first was a group of compounds, with a carboxy group, that formed a lactone ring and showed a dominant ion at [M+matrix ‐3 · H2O‐H]−. The other group, without carboxy, attached another matrix molecule and showed a dominant fragment ion at [M+2 · matrix‐3 · H2O‐H]−. The investigation of these complex structures was performed using various mat

ISSN:0951-4198    

DOI:10.1002/rcm.1290091003

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractComplexation in aqueous solutions between vancomycin, ristocetin A, teicoplanin and two bacterial cell‐wall analogues, Ac2‐L‐Lys‐D‐Ala‐D‐Ala (tripeptide) and Ac‐D‐Ala‐D‐Ala (dipeptide) has been examined by positiveion electrospray mass spectrometry (ES‐MS) and capillary zone electrophoresis (CZE)/ES‐MS. The ES‐MS data demonstrate that as well as complexes between monomeric antibiotics and either peptide, the investigated solutions contained complexes ranging from the simple homodimer of the antibiotic to a more complex association giving ions of the type [2(antibiotic)+3(tripeptide)+3H]3+. The same data also demonstrate that the homodimers of the investigated antibiotics are significantly suppressed in the presence of the tripeptide. The use of CZE/ES‐MS made it evident that the complexes between the antibiotic and the tripeptide were present in the solution prior to their introduction into the ion source. The two sets of data are compared with existing UV difference spectroscopy and nuclear magnetic resonance data on

ISSN:0951-4198    

DOI:10.1002/rcm.1290091004

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractThe advantages offered by the scanning facility of a multisector hybrid mass spectrometer of E1BE2qQ geometry, with software featuring an ‘experimental design’ function, are used to elucidate the origin of an artefact observed atm/z290.8 in the linked scan spectrum at constant B/E of them/z299 ion ofN,N‐bissalicylidene 1,2‐phenylenediamine, when performed using a forward geometry (EB) instrument. A previously proposed explanation, whereby the artefact peak was thought to originate from a fragmentation in the first field‐free region, could not be verified by repeating the scan using an instrument of E1BE2qQ geometry, where E1and E2were linked during the scan at constant B/E. Several different scans were performed using an ‘experimental design’ scanning function, which allows analyzers to be scanned and linked by means of user‐defined relationships. Thus, a mass‐analysed ion kinetic energy (MIKE) (E2) scan, with E1set to a value of 0.9725E0, revealed a peak at a value of 0.9462E0which was subsequently determined to be due to an ion with a mass‐to‐charge ratio of 299, by using the quadrupole mass filter. A recently proposed graphical method, that allows the field values at which the artefact ion is transmitted to be plotted three dimensionally on a cube, illustrates that while the peak will appear in the spectrum obtained using a linked scan at constant B/E using an EB instrument, this will not be the case with an EBE geometry instrument. The EBE arrangement shows that the interference peak atm/z290.8 appears to be the result of the transition of a higher‐mass ion within the fir

ISSN:0951-4198    

DOI:10.1002/rcm.1290091005

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractCoupling ofin vivomicrodialysis with capillary electrophoresis/mass spectrometry (MD‐CE/MS) was demonstrated. A microdialysis probe was inserted in the striatum of a rat brain and γ‐aminobutyric acid (GABA) in the brain was detected by CE/MS without any chemical treatment of the sample. MD‐CE/MS is expected to be a useful technique for analyzing brain substances, because of the relatively small damage it causes to a living structure and the high selectivity of the analytical tec

ISSN:0951-4198    

DOI:10.1002/rcm.1290091006

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractWe report the sequence analysis of an oligodeoxyribonucleotide by electrospray mass spectrometry (ES‐MS). For full sequence analysis of the oligomer, d(CGTAGCTACG), an enzyme digestion step followed by off‐line high performance liquid chromatography was used. For ES‐MS analysis, introducing the sample in an imidazole buffer with 70% acetonitrile increased the electrospray ion currents and helped reduce sodium‐adduct io

ISSN:0951-4198    

DOI:10.1002/rcm.1290091007

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have identifiedin vitrometabolites of bupropion (Wellbutrin®) from incubations with human liver S9 fraction and human liver microsomes based on molecular weight information from full scan experiments using a liquid chromatograph coupled to a quadrupole ion trap mass spectrometer capable of multi‐stage operation (LC/MSn). Preliminary experiments have shown that this instrument provides comparable sensitivity to conventional LC‐coupled triple quadrupole instruments for metabolic studies, while allowing detailed structural studies using MSnexperiments and routine on‐line coupling with high performance liquid chromatography via an external atmospheric pressure chemical ionization (APCI) source. The LC/MS analysis of human S9 showed the presence of three isomeric monohydroxylated metabolites of bupropion. These were further characterized in a series of MS/MS experiments which gave characteristic spectra for the three isomers. A minor dihydroxylated species was also identified in the human S9 sample and further characterized in a series of MSnexperiments. Detailed structural information was generated by the use of on‐line LC/MSntype experiments. We have followed the fragmentation pathways of several molecular ion species in a series of sequential LC/MSnexperiments, extending as far as MS6with scan cycle times of less than 1.5 s. Such experiments have provided insights into the structure of specific fragment ions. Additional metabolic products were identified in the rat liver microsomes incubatio

ISSN:0951-4198    

DOI:10.1002/rcm.1290091008

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractThis Communication describes the use of a bench‐top ion trap mass spectrometer for the study of structurally diagnostic ion/molecule reactions. The power of the experiment is increased by the broad‐band ion‐isolation and tandem mass spectrometry capabilities of the ion trap which are used to isolate the reactant ion and study its reactions under controlled conditions. The availability of multiple‐stage mass spectrometry (MSnwheren= number of stages) provides additional information on the nature of the productions. The compound to be ionized is conveniently introduced into the ion trap from aqueous solution using membrane introduction techniques while the neutral reagent is leaked into the trap through the calibration gas inlet. Polar Diels–Alder reactions of the [4 + 2+] type are investigated and comparisons are made between the reactions occurring in the ion trap and those in a pentaquadrupole mass spectrometer. Three‐stage tandem mass spectra (MS3) are used to characterize the ion/molecule reaction products in the quadrupo

ISSN:0951-4198    

DOI:10.1002/rcm.1290091009

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractThe mass spectrometric behaviour of condensation products of nine substituted benzaldehydes with 3‐amino‐1,2‐propanediol and 3‐amino‐1‐phenoxy‐2‐propanol was studied under electron impact and chemical ionization. The 70 eV electron impact mass spectra showed that, as in solution, the amino diol derivatives existed as three different structural isomers in the gas phase: viz. open‐chain Schiff base, oxazolidine and tetrahydro‐1,3‐oxazine. The fragmentations revealed a large amount of the decomposed molecular ions to have the open‐chain structure, but also that the amount of both ring forms was considerable. In the same way, with the amino alcohol derivatives both the open‐chain and the oxazolidine ring forms were present in the gas phase. In all cases, the ring formation was much more favourable in the gas phase than in solution. Substituents at the phenyl ring caused changes in the relative amounts of the different forms: electron‐withdrawing substituents shifted the equilibria in favour of the ring forms while electron‐donating substituents favoured the open‐chain form. Under chemical ionization, methane, isobutane and acetone were used as reagent gas. Methane was the only reagent gas that led to some fragmentat

ISSN:0951-4198    

DOI:10.1002/rcm.1290091010

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractA method is described for the rapid analysis of mixtures of porphyrin methyl esters using laser desorption/ionization time‐of‐flight mass spectrometry (LDI‐TOF MS). Ions corresponding to [M+H]+for each component have been observed without the need for added matrix. LDI‐TOF MS has been applied to the analysis and characterization of porphyrin methyl esters derived from urine samples of patients suffering from various porphyrias. This technique has been shown to provide ‘fingerprint’ profiles of the porphyrins present in each urine sample, characteristic of the porphyria, which compare favourably with those obtained with the established method of high‐performance liquid chromatography. LDI‐TOF MS is a rapid and reliable method for the screening of urine from patients suffering

ISSN:0951-4198    

DOI:10.1002/rcm.1290091011

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY