Collision‐induced dissociation of aluminum cluster ions: Fragmentation patterns, bond energies, and structures for Al+2–Al+7

Nonribosomal cyclopeptide cyclosporin A (CsA), produced by fungus Tolypocladium inflatum, is an extremely important immunosuppressive drug used in organ transplantations and for therapy of autoimmune diseases. Here we report for the first time production of CsA, along with related cyclosporins B and C, by Tolypocladium inflatum strains of marine origin (White Sea). Cyclosporins A–C contain an unusual amino acid, (4R)-4-((E)-2-butenyl)-4,N-dimethyl-l-threonine (MeBmt), and are prone to isomerization to non-active isocyclosporine by N→O acyl shift of valine connected to MeBmt in acidic conditions. CsA and isoCsA are not distinguishable in MS analysis of [M+H]+ ions due to the rapid [CsA+H]+→[isoCsA+H]+ conversion. We found that the N→O acyl shift is completely suppressed in cyclosporine [M+2H]2+ ions, and their MS/MS fragmentation can be used for rapid and unambiguous analysis of cyclosporins and isocylosporins. The fragmentation patterns of [CyA+2H]2+ and [isoCyA+2H]2+ ions were analyzed and explained. The developed approach could be useful for MS analysis of other peptides containing β-hydroxy-α-amino acids.

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Noncovalent metal-ligand bond energies as studied by threshold collision-induced dissociation

Mass Spectrometry Reviews ◽

10.1002/1098-2787(200007)19:4<215::aid-mas2>3.0.co;2-x ◽

2000 ◽

Vol 19 (4) ◽

pp. 215-247 ◽

Cited By ~ 198

Author(s):

M. T. Rodgers ◽

P. B. Armentrout

Keyword(s):

Collision Induced Dissociation ◽

Bond Energies ◽

Metal Ligand ◽

Ligand Bond

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MASS SPECTRA AND DISSOCIATION PATTERNS OF TELLURIUM CLUSTERS USING POSITIVE AND NEGATIVE SECONDARY-ION MASS SPECTROMETRY

Surface Review and Letters ◽

10.1142/s0218625x96001042 ◽

1996 ◽

Vol 03 (01) ◽

pp. 577-582 ◽

Cited By ~ 5

Author(s):

H. ITO ◽

T. SAKURAI ◽

T. MATSUO ◽

T. ICHIHARA ◽

I. KATAKUSE

Keyword(s):

Mass Spectrometry ◽

Secondary Ion Mass Spectrometry ◽

Cluster Ions ◽

Mass Spectrometers ◽

Scanning Method ◽

Ion Mass Spectrometry ◽

Cluster Ion ◽

Sector Type ◽

Fragmentation Patterns ◽

Secondary Ion

Size distribution of positive and negative tellurium clusters in the size range from 2 to 56 atoms was investigated by secondary-ion mass spectrometry (SIMS). Cluster ions were produced by the 12-keV Xe+ ions bombardment of a sample tellurium sheet and were mass-analyzed using sector-type double-focusing mass spectrometers. It was found that a discontinuous variation of cluster-ion intensity appeared at specific numbers of n. These numbers were 5, 8, 12, 15, 19, and 23 for positive clusters and 6, 10, 13, and 16 for negative clusters. The dissociation pattern was also investigated by an acceleration-voltage scanning method. It was found that Te2, Te5, and Te6 fragmentation events occurred at a large probability. Observation of specific fragmentation patterns suggested the existence of nonsequential fragment channels.

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