Fungal metabolites. Part 3. Structural elucidation of antibiotic peptides, trichosporin-B-IIIb, -IIIc, -IVb, -IVc, -IVd, -VIa and -VIb from Trichoderma polysporum. Application of fast-atom bombardment mass spectrometry/mass spectrometry to peptides containing a unique Aib–Pro peptide bond
Akira IidaMasahiro OkudaShinichi UesatoYoshihisa TakaishiTetsuro ShinguMasanori MoritaTetsuro Fujita
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Trichosporin-B-IIIb, -IIIc, -IVb, -IVc, -IVd, -VIa and -VIb are components of an antibiotic peptide mixture produced by Trichoderma polysporum. Each component was purified by reversed-phase high-performance liquid chromatography (HPLC). The amino acid sequences of these peptides, which have an unstable peptide bond, Aib–Pro, were elucidated by fast-atom bombardment mass spectrometry (FAB MS) and fast-atom bombardment mass spectrometry/mass spectrometry (FAB MS/MS) with the help of NMR spectroscopy. The molecular weights of these peptides were all ca. 2000 and the structures were very similar.Keywords:
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A comparison of old and new fast atom bombardment (FAB) mass spectrometric strategies for characterization of ganglioside inner esters (lactones) is presented. Data obtained for lactones of GD3 (NeuAcα 2→8NeuAcα2 → 3Galβ1 → 4Glcβ1 → 1Cer) using negative ion FAB mass spectrometry of underivatized materials, negative ion FAB mass spectrometry following ammonolysis, and positive ion FAB mass spectrometry following ammonolysis and permethylation are presented and discussed. The latter method uses well-known reactions to produce a novel type of ganglioside derivative, highly amenable to analysis by positive ion FAB mass spectrometry, which is introduced to simplify unambiguous location of NeuAc residues involved in ester linkages to other sugars.
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Abstract GE2270A is a novel antibiotic active against Gram‐positive bacteria and anaerobes. Its structure originates from a peptidic backbone, the amino acids of which have been modified to produce a macrocycle and a side‐chain. It contains a heterocyclic chrornophonc system, a number of thiazoleamino acids and three unmodified natural amino acids. The structure [relative molecular mass (RMM) 1289] was determined using various spectroscopic techniques, of which fast atom bombardment mess spectrometry, gas chromatography/mass spectrometry, desorption chemical ionization mass spectrometry and fast atom bombardment tandem mass spectrometry played an important role. The mass spectrometric approach was applied to the intact molecule and to the various hydrolysis products, including the chromophoric part (RMM 634).
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The determination of negative and positive fast atom bombardment mass spectrometry (FAB-MS) and field desorption mass spectrometry (FD-MS) were carred out on 25 iridoidal glycosides.The result showed that negative FAB-MS is more useful for the determination of molecular weight and the structural elucidation of iridoidal glycosides than positive FAB-MS and FD-MS.
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Fast atom bombardment
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Ion-mobility spectrometry–mass spectrometry
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Fast atom bombardment (FAB) mass spectrometry provides useful structural information about salen complexes and salen-based oxo transfer catalysts that are not appreciably soluble in organic solvents. It was discovered that initial dissolution of these complexes in trifluoroacetic acid was crucial for producing good FAB mass spectra. Trifluoroacetic acid helps dissolve the salen-based catalysts, concentrates the analyte molecules at the matrix surface, and most importantly, suppresses the reduction process, which is a well-known phenomenon when protic matrices are used. The best FAB matrices for these catalysts were found to be thioglycerol and "magic bullet." However, dechlorination occurred under the acid conditions for complexes containing iron chloride and manganese chloride. Demetalation also occurred for nickel-containing oxo transfer salen-based complexes. When the salen-based complexes are soluble in LC solvents, they can be analyzed easily by atmospheric pressure chemical ionization (APCI) mass spectrometry without the employment of relatively nonvolatile matrices. In addition, APCI/MS provides much more sensitive detection for manganese-salen complexes when compared with FAB results. No dechlorination or demetalation were observed when a negative ion mode APCI was employed. To our knowledge, this is the first time that an intact molecule of this type of complex has been observed by mass spectrometry.
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A comparison has been made of positive- and negative-ion fast-atom-bombardment (FAB) and electron-impact (EI) mass spectrometry for analysis of oligosaccharides and alditols containing alternating and consecutive sequences of neutral and acetamido sugars. Among these were novel chemically synthesized tetrasaccharides with Ii antigen activities. FAB ionization has the advantage that it is applicable to non-derivatized oligosaccharides and it can determine Mr. However, the abundance of fragment ions providing structural information and the amount of material required for analysis (1-50 nmol) varied from sample to sample. In contrast, EI mass spectrometry of 5 nmol of permethylated or peracetylated oligosaccharides reliably gives all the fragment ions formed by cleavage across the glycosidic bonds.
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Trichosporin-B-IIIb, -IIIc, -IVb, -IVc, -IVd, -VIa and -VIb are components of an antibiotic peptide mixture produced by Trichoderma polysporum. Each component was purified by reversed-phase high-performance liquid chromatography (HPLC). The amino acid sequences of these peptides, which have an unstable peptide bond, Aib–Pro, were elucidated by fast-atom bombardment mass spectrometry (FAB MS) and fast-atom bombardment mass spectrometry/mass spectrometry (FAB MS/MS) with the help of NMR spectroscopy. The molecular weights of these peptides were all ca. 2000 and the structures were very similar.
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Three glutathione conjugates of acetaminophen were characterized by fast atom bombardment/mass spectrometry (FAB/MS) and fast atom bombardment/mass spectrometry/mass spectrometry (FAB/MS/MS). The conjugates, 3-(glutathion-S-yl)acetaminophen, 3-(glutathion-S-yl)diacetaminophen and 3-(diglutathion-S-yl)diacetaminophen showed intense [MH]+ ions at m/z 457, 606 and 911, respectively. Only 3-(glutathion-S-yl)acetaminophen showed any fragmentation by FAB/MS. Structurally characteristic fragmentation was observed with all three conjugates when the [MH]+ ions were collisionally activated. The loss of the glycine (GLY) and glutamic acid (GLU) moieties indicated the presence of at least one glutathione (GSH) group. Multiple losses, some of which could only occur via cleavages in both GSH moieties, were observed with the diglutathione conjugate.
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Abstract In positive-ion fast atom bombardment (FAB) mass spectrometry, when oligosaccharides are mixed with an appropriate amount of NH4Cl, a highly abundant [M+NH4]+ peak appears in FAB mass spectra. From the adduct ion [M+NH4]+, the molecular weights of oligosaccharides can be determined definitively. This technique may especially be applied to analyze the mixture of oligosaccharides.
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