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1. |
Modelling coulomb effects in Fourier‐transform ion cyclotron resonance mass spectrometry by charged disks and charged cylinders |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 1-3
Shu‐Ping Chen,
Melvin B. Comisarow,
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摘要:
AbstractA two‐dimensional charged‐disk model is proposed to explain Coulomb‐induced frequencey shifting in Fourier‐transform ion cyclotron resonance (FT‐ICR) mass spectrometry. This model corresponds more closely to the actual FT‐ICR experiment than does the charged‐point model,1which we recently developed. The model consists of a uniformly charged disk of ions of mass m1, whose excited cyclotron motion is perturbed by a second uniformly charged disk of ions of mass m2, whose cyclotron motion is also excited. By looking in a rotating coordinate frame which rotates at the cyclotron frequency of the first disk, it is seen that the second disk creates an average radial force on the first disk which lowers the cyclotron frequency of the first disk. This radial force is numerically evaluated and found to be a function of the cyclotron radius, the ration of the cyclotron radius to the disk radius, and the charges of the two disks. Unlike the charged‐point model, which was flawed by having an infinite average radial Coulomb force, the average radial Coulomb force for the charged‐disk model is finite. This average Coulomb force allows the use of formulae which permit characterization of a given set of model parameters in terms of an ‘apparent Coulomb distance’, for which a model consisting of point charges with a fixed location in a rotating frame would give the same frequency shift. It is argued that the same ‘apparent Coulomb distance’ would apply for a charged cylinder model, which accounts for Coulomb‐induced line broadening in addition to Coulomb‐induced frequency shifting. It is suggested that the treatment in this paper, together with the use of elongated cells equipped with trapping screens, could permit absolute mass
ISSN:0951-4198
DOI:10.1002/rcm.1290060102
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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2. |
Mass spectrometric analysis of a transition‐metal‐binding peptide using matrix‐assisted leaser‐desorption time‐of‐flight mass spectrometry. A demonstration of probe tip chemistry |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 4-8
Randall W. Nelson,
T. William Hutchens,
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摘要:
AbstractMatrix‐assisted laser desorption time‐of flight mass spectrometry has been used to investigate the affinity of aqueous copper ions for a 26‐residue synthetic peptide predicted to have metal‐binding properties. A specific reaction occurred upon the dirct application of aqueous CuSO4to the matrix/peptide sample remaining on the probe tip ater initial mass spectrometric investigation. Results indicated the binding of up to one copper ion per histidine residue and the loss of one proton for each bound copper. Bound copper was not returned to solution upon subsequent cold water washings of the probe tip. These results suggest that covalent interations, between the copper and the peptide, occurred during the probe‐tip application of the metal ion to t
ISSN:0951-4198
DOI:10.1002/rcm.1290060103
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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3. |
Electrospray ionization mass spectra of hemoglobin and transferrin by a magnetic sector mass spectrometer. Comparison with theoretical isotopic distributions |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 9-13
Yoshinao Wada,
Jun Tamura,
Brian D. Musselman,
Daniel B. Kassel,
Toru Sakurai,
Takekiyo Matsuo,
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摘要:
AbstractElectrospray ionization mass spectra of human hemoglobin chains and of transferrin were acquired on a magnetic sector mass spectrometer. The observed molecular ion for each hemoglobin chain was in good agreement with the theoretical isotopic distribution at a reasonable resolution of 2000. The clear separation of a variant ß‐chain in admixture with the normal counterpart at mass 15867 that differed from it by 14 Da (0.09%) ensured that a smaller mass difference could be detected. The molecular ions for human transferrin were too broad compared with the theoretical shape to determine the molecular mass accurately, probably due to the heterogeneity of the carbohydrate moiety. A decrease in mass by neuraminidase digestion, however, determined the average number of sialic acids in the molecu
ISSN:0951-4198
DOI:10.1002/rcm.1290060104
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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4. |
Ionspray mass spectrometry of marine toxins. III. Analysis of paralytic shellfish poisoning toxins by flow‐injection analysis, liquid chromatography/mass spectrometry and capillary electrophoresis/mass spectrometry |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 14-24
S. Pleasance,
S. W. Ayer,
M. V. Laycock,
P. Thibault,
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摘要:
AbstractIonspray mass spectrometry has been used to monitor the purification of saxitoxin, the parent compound in the family of toxins responsible for paralytic shellfish poisoning (PSP), from a strain of the dinoflagellate Alexandrium excavatum. Quantitative results obtained by flow‐injection analysis are compared to those obtained by high‐performance liquid chromatography with post‐column oxidation and fluorescence detection. The coupling of liquid chromatography and capillary electrophoresis with ionspray mass spectrometry is described for the separation of mixtures of PSP toxins and the highly potent pufferfish toxin tetrodotoxin. Tandem mass spectrometry is used to provide the structural information, and the ability to distinguish isomeric PSP toxins both chromatographically and mass spectrometrically is demonst
ISSN:0951-4198
DOI:10.1002/rcm.1290060105
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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5. |
Measurement of gas‐phase binding energies of crown ethers with metal ions by Fourier‐transform ion cyclotron resonance mass spectrometry |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 25-27
Alan R. Katritzky,
N. Malhotra,
R. Ramanathan,
R. C. Kemerait,
Jaffrey A. Zimmerman,
John R. Eyler,
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摘要:
AbstractComplexes of the type [crown+M]+were observed following laser desorption ionization of 18‐crown‐6 molecules ‘doped’ with K+, Cs+, and Ba+. Laser desorption ionization of 15‐crown‐5 and 12‐crown‐4 ‘doped’ with the same metals gave [(crown)]2+[M]+type sandwich complexes. Binding energies of crown ethers with different metal ions in all such complexes have been estimated from appearance energies obtained in the collisionally‐activated dissociation of the corresponding last
ISSN:0951-4198
DOI:10.1002/rcm.1290060106
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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6. |
Desorption of ions from locust tissues. II. Metabolites of E‐destruxin using negative‐ion fast‐atom bombardment mass spectrometry |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 28-31
C. Lange,
C. Loutelier,
J.‐C. Cherton,
P. Cassier,
A. Vey,
M. Pais,
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摘要:
AbstractDetoxification of E‐destruxin into E‐diol‐destruxin, conjugated glutathion‐E‐destruxin, cysteinyl‐E‐destruxin, and phosphorylated‐E‐destruxin in vivo inLocusta migratoriais demonstrated using direct negative‐ion fast‐atom bombardment mass spectrometry (FAB‐MS) without the need for prior ext
ISSN:0951-4198
DOI:10.1002/rcm.1290060107
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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7. |
The correct molecular weight of myoglobin, a common calibrant for mass spectrometry |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 32-36
Joseph Zaia,
Roland S. Annan,
Klaus Biemann,
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摘要:
AbstractMyoglobins from horse heat muscle, horse skeletal muscle and sperm whale are widely used as calibration standards or test compounds for various mas spectrometric methodologies. In all such cases reproted in the literature, a molecular weight value is used (16950.5 and 17199, respectively) which is based on the assumption that amino acid 122 in this 153 amino‐acid‐long protein is asparagine, overlooking a published suggestion that it is aspartic acid instead. Since the mass assignment accuracy for matrix‐assisted laser desorption mass spectrometry is reproted to be ±0.01% and for electrospray ionization ±0.0025%, and error of one mass unit in ∼ 17000 would be significant. The mass‐to‐charge ration of ions of the tryptic peptide encompassing amino acid 122 derived from commercially available horse heart and horse skeletal myoglobins, the apomyoglobin of the latter, and the tryptic and chymotryptic peptide of sperm whale myoglobin proved that in both proteins amino acid 122 is indeed aspartic acid, rather than asparagine. This finding was further confirmed by the collision‐induced dissociation sectra of the [M+H]+ ions of the tryptic peptides from the horse myoglobins and the chymotriptic peptide from sperm whale myoglobin. Thus, the correct molecular weight of horse myoglobinis 16951.49 and that of the sperm whale prot
ISSN:0951-4198
DOI:10.1002/rcm.1290060108
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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8. |
Dissociation of positively‐charged apliphatic epoxides. III. [C4H8O]+˙ eposides and α, β unsaturated ethers |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 37-45
Florence Berruyer‐Penaud,
Guy Bouchoux,
Jeanine Tortajada,
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摘要:
AbstractUnimolecular dissociation of the molecular cations of 1,2‐expoxybutane (1), 1‐methoxypropene (2), 2,3‐epoxybutane (3), ethyl‐vinyl ether (4), 1,2‐epoxy‐2‐methylpropene (5), and 2‐methoxypropene (6)have been investigated. Different behaviour of pairs of [C4H8O]+˙ isomers (1+˙/2+˙), (3+˙/4+˙) and (5+˙/6+˙) have been demonstrated. Isomerization by epoxide ring opening and 1,4‐hydrogen migration is suggested to explain the similar unimolecular chemistry observed for the two partners
ISSN:0951-4198
DOI:10.1002/rcm.1290060109
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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9. |
Identification of cyclobutane‐type dimers of substituted cinnamic acids by gas chromatography/mass spectrometry |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 46-53
D. Stewart,
G. W. Robertson,
I. M. Morrison,
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摘要:
AbstractSubstituted cinnamic acids were dimerized, under fluorescent or UV light, as a glassy coating on a vial then subsequently analysed by GC/MS. Mass Spectrometric analysis of the dimers formed by each acid allowed the assignment of the dimer as a truxillic or truxinic structure since these structures had distinctive fragmentation patterns; the breakdown of the truxillic acids involves a McLafferty rearrangment before fragmentation occurs, whereas the truxinic acids, which have both carboxy groups on one side and both aromatic groups on the other, fragment asymmetrically to give characteristic stilbene and dicarboxylate fragments. It is apparent from the results of the dimerization of the lcinnamic acids that, under the conditions used here, if the monomeric acid had the capacity for hydrogen bonding using the ring substituent as well as the carboxy group, the dimerization products would be overshelmingly truxillic in structure. However, if only the carboxy group could hydrogen bond, the products would be almost exclusively traxinic in structure.
ISSN:0951-4198
DOI:10.1002/rcm.1290060110
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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10. |
Negative‐ion fragmentations of deprotonated heterocycles. The pyrazole and imidazole ring systems |
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Rapid Communications in Mass Spectrometry,
Volume 6,
Issue 1,
1992,
Page 54-57
Gregory W. Adams,
John H. Bowie,
Roger N. Hayes,
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摘要:
AbstractImidazole and pyrazole deprotonate preferentially at the 1‐position, and a number of fragmentations are best rationalized as occurring through common ring‐opened intermediate−NHCHCHCN.C‐Methylomidazoles and pyrazoles fragment
ISSN:0951-4198
DOI:10.1002/rcm.1290060111
出版商:Heyden&Son Limited
年代:1992
数据来源: WILEY
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