摘要:

AbstractThis paper describes the use of dynamically programmed scanning in the automation of the acquisition and processing of data using a quadrupole ion trap mass spectrometer. The programs written to carry out the fixedion tandem mass spectrometry experiments and to automate the production of the three‐dimensional graphs are described. The use of three‐dimensional graphs to display familial data is also discussed, with examples of spectra gi

ISSN:0951-4198    

DOI:10.1002/rcm.1290090903

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractA new interface for coupling electrospray (ES) ionization and Fourier transform ion cyclotron resonance (FTICR) mass spectrometry has been developed based on an electrostatic ion guide (EIG). In these initial studies, the EIG interface has been demonstrated to be a simple but effective means of transmitting ES ions generated outside the magnetic field to the FTICR cell. In the current system, the pressures in the EIG region and front FTICR cell are 10−5and 10−6Torr, respectively. Under these conditions, ions may be accumulated with low trapping voltages (0.5–0.75 V) and without a high pressure pulse of buffer gas. ES‐FTICR spectra of picomole to femtomole quantities of several peptides, proteins, nucleotides and dinucleotides have been obtained. Modifications currently in progress should enhance performance with respect both to limits of detection and to mass res

ISSN:0951-4198    

DOI:10.1002/rcm.1290090904

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractA new approach is developed for the rapid and cost‐effective detection of human genetic polymorphisms based on matrix‐assisted laser description/ionization mass spectrometric (MALDI MS) detection using a nitrocellulose film substrate. This method employs polymerase chain reaction (PCR) amplification using DNA extracted from buccal cells as templates, followed by direct digestion with restriction enzymes and subsequent analysis by MALDI MS. The extraction of DNA from buccal cells provides a rapid and convenient means for sampling PCR‐based diagnostic analysis. The amount of DNA was sufficient as the template for both normal PCR amplifications, and amplifications involving the use of mismatched primers and multiple primers. The MALDI MS methodology has been successfully used for the analysis of such PCR products where restriction fragments generated directly in PCR reactions have been used for detection of carbonic anhydrase and cystic fibrosis transmembrane conductance regulator as model genes. The detection of genetic polymorphisms following routine biological and clinical procedures with the MALDI MS method is demonstrated. The results from MALDI MS analysis are shown to be comparable to those obtained from gel electrophoresis but the MALDI MS method is several orders of magnitude faster than gel electrophoretic techniques. The method described herein should also be readily extended to other areas involving DNA screening and te

ISSN:0951-4198    

DOI:10.1002/rcm.1290090905

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractIon yields were investigated in matrix‐assisted laser desorption/ionization (MALDI) as a function of amino acid composition using a variable wavelength ion source. In the case of nitrogen laser excitation (337 nm), [M+H]+ions were abundant for short peptides containing basic or polar amino acid residues. The lack of basic residues led to diminishing ion formation at 337 nm. Increasing the chain length led to enhanced ionization even for peptides with non‐polar side chains. In contrast to the liquid phase basicities the basic residues showed Arg>His>Lys order in their affinity to protons. Variations in the average ion yield showed decreasing trend with increasing basicity of the residues pointing to potential differences in the matrix incorporation of different guest molecules. Dye laser excitation at 280 nm resulted in extensive fragmentation and enhanced ion formation from peptides containing aromatic side chains indicating the possible role of analyte excited states in ion formation. Semi‐empirical quantum chemical calculations were used to explore the sites of protonation. Heat of formation diagrams of the matrix‐analyte complexes were examined as a function of their configuration. Investigation of the optimized geometries allowed the location of bifurcated and linear hydrogen bonds between the non‐polar analyte (e.g., Gly‐Gly) and matrix molecules. In addition to these intermolecular bonds, in the case of His‐His an intramolecular hydrogen bond was also formed within the analyte molecule. Proton affinity values were calculated for every dipeptide while the site of protonation was varied. The results seemed to indicate that for every dipeptide the amino terminus was more susceptible to protonation than the peptide bond. Due to increased stabilization effects in homo‐oligomers (Glyn), increasing the number of residues led to an increase in proton affinity. For basic diopeptides (e.g., His‐His), the side chains had the highest proton affinity, underlining their role in

ISSN:0951-4198    

DOI:10.1002/rcm.1290090906

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractN‐Phenyllinoleamide (NPLA), the anilide of linoleic acid, has been regarded as a marker of the case oils associated with toxic oil syndrome, but the mechanisms of toxic injury remain enigmatic. Experimental data have related an increased systemic toxic effect of heated linoleic anilides to chemical structural modifications that might also be possible byin vivometabolism; however, little is known about their metabolism. Taking into account thatNPLA is a derivative of linoleic acid, a fatty acid that can be metabolized by lipoxygenase activity to a vast array of derivatives possessing biological activity, the objective has been to elucidate the oxidative metabolism ofNPLA by mouse peritoneal macrophages, a cellular model with high lipoxygenase activity. Cells were incubated with 0.1 mMNPLA spiked withN‐phenyl[1‐14C]linoleamide. The metabolites were separated by high‐performance liquid chromatography and individually collected prior to GC/MS analysis. Identification of trihydroxy‐, monohydroxy‐ and epoxy‐derivatives ofNPLA, suggests that this xenobiotic can be metabolized via the same oxidative processes as for linoleic acid. Furthermore, identification of the non‐amidated monohydroxylated and trihydroxylated derivatives of linoleic acid arising fromNPLA suggests an amidase‐like activity with release of aniline and the free fatty acid. These results provide information about possible biological structures arising fromNPLA, and open the way to evaluate the biological significance of these metabolites in the inflammatory reactions associated with t

ISSN:0951-4198    

DOI:10.1002/rcm.1290090907

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractA tandem reflectron time‐of‐flight mass spectrometer has been constructed for the investigation of laser photofragmentation of selected molecular ions. Ions are generated by an ablation laser and attracted by ion optics into the field‐free flight region of a reflectron time‐of‐flight mass spectrometer. Laser photofragmentation of selected molecular ions takes place at the turn‐around point of ions in the reflectron. Fragmentation mass calibration, parent ion selection, ion collection effects, reflectron field effects and the mass resolution of this tandem reflectron time‐of‐flight mass spectrometer are described. Furthermore it is shown that laser parameters may be used to control the fragme

ISSN:0951-4198    

DOI:10.1002/rcm.1290090908

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractA multiresidue method was developed for the trace level determination of sulfonylurea herbicides in aqueous samples. The method employs on‐line solid‐phase extraction and electrospray and thermospray reversed‐phase liquid chromatography mass spectrometry. In combination with time‐scheduled selected‐ion monitoring, the method permits the detection of the sulfonylureas down to the 50–100 ng/L level with excellent recoveries of>90% and reproducibilities between 2 and 8.5% for almost all of the investigated compounds. This improved method is superior to existing techniques because no special clean‐up step is necessary, and owing to the fast online preconcentration step, the technique can be used as a rapid screening and confirmatory method. The method can be used with either thermospray cr electrospray mass spectrometry, both of which provided mass spectra with at least three structure‐signficant ions necessary for an unambiguous identification in enviro

ISSN:0951-4198    

DOI:10.1002/rcm.1290090909

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractThe most common mutation of the cystic fibrosis gene is characterized by the deletion of three nucleotides that code phenylalanine in the 508 position of the cystic fibrosis transmembrane conductance regulator. We report the first measurements by matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight mass spectrometry for the ΔLF508 mutation in cystic fibrosis carriers and patients. Furthermore, in a blind test, results from the normal and ΔLF508 mutant alleles in 30 clinical samples based on MALDI mass spectrometry and on conventional gel analysis of the DNA were in total agreement. These results demonstrate the utility of MALDI mass spectrometry in the molecular diagnosis of mutant alleles and point to its potential use for ultra‐fast detection in large‐scale screening of DN

ISSN:0951-4198    

DOI:10.1002/rcm.1290090910

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractThe quantitative investigation of the four RNA nucleosides (adenosine, guanosine, cytidine and uridine) using fast‐atom bombardment mass spectra is reported. Nucleoside concentrations are varied in the 0.8–4% range. The nucleoside hydrogen‐bonded complexes are shown to form primarily on the liquid matrix su

ISSN:0951-4198    

DOI:10.1002/rcm.1290090911

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY

摘要:

AbstractThe electron impact mass spectra of some 2‐methyl‐3‐furancarboxanilides and 2‐methyl‐3‐furancarbothioanilides are discussed. Dominant peaks are formed by simple cleavage of a CN bond in the anilides as well as in the thioanilides. Thioanilides show some additional fragmentation pathways recently reported which are not seen in the anilides. (T. Jagodzinski and M. Stobiecki,Org. Mass Spectrom., Vol. 25, p

ISSN:0951-4198    

DOI:10.1002/rcm.1290090912

出版商:Heyden&Son Limited    

年代:1995

数据来源: WILEY