Fast Atom Bombardment Mass Spectrometry Spectra Research Articles

Structural Determination of Saponins Extracted from Starfish by Fast Atom Bombardment Collision-Induced Dissociation Mass Spectrometry

Three saponins were extracted and isolated from starfish by reversed-phase high performance liquid chromatography (HPLC), and analyzed by fast atom bombardment mass spectrometry (FAB-MS). Their molecular weight information could be obtained by the presence of abundant [M+Na]+ ions and weak [M+H]+ ions in FAB-MS spectra. Moreover, high resolution mass measurements of their [M+Na]+ ions were performed at the resolution of 10000 to elucidate the element composition of extracted saponins. The collision-induced dissociation (CID) of sodium-adducted molecules [M+Na]+ yielded diverse product ions via dissociated processes. In the collision-induced dissociation (CID)-MS/MS analysis of [M+Na]+ ion, the sulfate-containing saponins produced characteristic ions such as SO4Na+, [NaHSO4+Na]+, [M+Na-sugar]+ and [M+Na-2sugar]+ ions, whereas the sulfate-free compound showed characteristic ions produced by cleavage of sugar moiety and side chain of aglycone. The fragmentation patterns could provide information on the linkage position of sugar groups in aglycone and sulfate groups.

Phospholipid molecular species distributions of Candida isolates from the UK and Iran.

Some species of Candida have been shown to differ with respect to their polar lipid fingerprints when analysed by fast atom bombardment mass spectrometry (FABMS). The aims of this study were to contribute to the existing body of information by (i) examining representatives of species not previously examined and (ii) seeking strains differences associated with country of origin (UK or Iran). FABMS analysis was performed on extracted lipids of 22 strains representing eight species of Candida. The most abundant anion (19 isolates) in spectra was with mass to charge (m/z) 281, corresponding to C18:1 carboxylate. The major phospholipid analogue anions were m/z 515 and 501 (13 strains). These anions were putatively identified as the phosphatidyl molecular species PA(23 : 2) and PA(22 : 2) respectively. Data for strain pairs were compared using the Pearson's coefficient of linear correlation. The values generated were used to cluster strains by nearest-neighbour linkage, using both carboxylate and phospholipid analogue anion data. Isolates of C. parapsilosis were clearly distinct from other isolates. Iranian isolates tended to cluster together when phospholipid anion data were used. However, if carboxylate anion data were used, four Iranian isolates of C. albicans were tightly clustered with three UK isolates, of which two were C. albicans and one was C. dubliniensis. It is concluded that both lower, and higher, mass peaks in FABMS spectra can be of potential value in comparing Candida isolates from different countries and from different species. When polar lipids of different Candida species are compared, it is important to bear in mind that geographical differences affect results as has been observed with bacteria in similar studies.

Negative-ion fast atom bombardment mass spectrometry of sulfonylurea herbicides

Seven sulfonylurea herbicides were studied using negative-ion fast atom bombardment mass spectrometry (FAB-MS). The spectra were characteristic of the structure of the examined herbicides with fragmentation at the sulfonylurea bridge representing both aromatic moieties. The fragmentation pattern was established based on the FAB- B/E mass spectrometry/mass spectrometry linked-scan spectra. Background-subtracted negative ion FAB-MS spectra of the herbicides exhibit [M‐1] ‐ peaks and their fragmentation products. Application of triethylenetetramine as a FAB matrix resulted in enhanced fragmentation. The 3-nitrobenzyl alcohol FAB spectra typically exhibited high-abundance [M‐1] ‐ peaks and fewer fragment

Analysis of long-chain fatty acyl coenzyme A. Thioesters by negative ion fast-atom bombardment mass spectrometry and tandem mass spectrometry

Long-chain acyl Coenzyme A (CoA) is essentially composed of three major chemical groups, fatty acyl-, phosphopantetheino-, and 3′,5′,-adenosine diphospho-moieties. The negative ion fast-atom bombardment mass spectrometry spectra of long-chain acyl CoA thioesters were characterized by the formation of abundant [M = H] − and two distinct classes of fragment ions, one class which retained the acyl group and another class which is related to CoA that contains the phosphopantethene and adenine. The ions which retained the acyl group in the spectrum of palmitoyl CoA appeared at m/z 675, 657, 595, and 577 and were found to decompose by loss of alkylketene observed at m/z 357 and 339. Those ions which retained the adenine group were observed at m/z 426 and 408. In contrast to these ions observed following fast-atom bombardment ionization, tandem mass spectrometry of the [M - H] −, from palmitoyl CoA ( m/z 1004), yielded the adenine-containing ions as major products and the acyl-containing ions were of low abundance or not detected. These results suggested that the formation of many characteristic ions observed in direct FAB analysis occurred during the desorption process. The unique relationship between ions which involved the transition from acyl-containing ions to only CoA-containing ions by the loss of alkylketene allowed the development of tandem mass spectrometry protocols for the analysis of acyl CoA mixtures. Precursor scans of either m/z 357 or 339 yielded the identification of each species in a complex mixture. Identification of specific species was obtained with a neutral loss scan of the mass for a specific alkylketene.

Studies of naturally occurring modifications of sialic acids by fast-atom bombardment-mass spectrometry. Analysis of positional isomers by periodate cleavage.

A variety of modifications of sialic acids have been described in nature. There are currently many difficulties in the detection and quantitation of these modified sialic acids from biological sources. We report here that fast-atom bombardment-mass-spectrometry (FAB-MS) of native sialic acids provides specific detection and quantitation of many previously known compounds. Derivatization of the sialic acids by reduction and peracylation under acidic conditions prior to FAB-MS provides further confirmation of their identity and improves the sensitivity of detection. Samples containing as little as 100 ng of a derivatized sialic acid loaded onto the FAB target allowed accurate identification. Mixtures of sialic acids could be analyzed, and minor components were seen, at levels undetectable by other currently known techniques. Analysis of known mixtures of different sialic acids gave reproducible relative signal intensities, indicating that quantitative data can be derived from the FAB-MS spectra. After reduction and peracylation, each sialic acid gave two major molecular ions, corresponding to the fully derivatized linear species and a lactone form, and a minor ion, corresponding to an anhydro form. Lactone formation was minimal in the case of four substituted sialic acids, indicating that the hydroxyl group at the 4-position is involved in lactonization. Differentiation between different positional isomers of the modified sialic acids could be achieved using controlled degradation with periodate, tagging of the fragments with p-aminobenzoic acid ethyl ester under acid reducing conditions, peracylation, and FAB-MS of the derivatized products. We used this FAB-MS strategy to identify a novel sialic acid, 8-O-methyl-7,9-di-O-acetyl-N-glycolyl-neuraminic acid from the starfish Pisaster brevispinus, and to demonstrate the presence of a previously undetected sialic acid, 4,8-anhydro-N-acetyl-neuraminic acid in acid hydrolysates of horse serum. We also use FAB-MS to show that the alkaline conditions traditionally used for analytical de-O-acetylation of sialic acids causes substantial conversion of 4-O-acetylated sialic acids into the same anhydro compound.

Secondary ion mass spectrometry (SIMS) of metal halides. IV. The envelopes of secondary cluster ion distributions

The relative secondary ion intensities of cluster ions of the type [M(MI) n ] + and [I(MI) n ] − from the fast atom bombardment mass spectrometry (FABMS) of alkali iodides (MI) for n<100 are presented, and mass-resolved mass spectra of cesium iodide (CsI) clusters exceeding m/z 25 000 are reported. The FABMS spectra are qualitatively consistent with previously reported secondary ion mass spectrometry (SIMS) spectra. The envelopes of the extended mass spectra are fitted to the distributions predicted by a model based on random bond breaking. The bond-breaking model (BBM) distributions fit well on the overall envelope of both the positive and negative ion sodium iodide (NaI, simple cubic) and CsI (body-centered cubic) cluster ion distributions, when Bethe lattices of the appropriate coordination number are used to approximate the true lattices. Ion abundance enhancements at certain “magic numbers” in the envelopes can be predicted by the BBM; however, these enhancements and the reduced ion abundance immediately following the “magic number” are consistent with experimentally observed unimolecular, or more appropriately, unicluster decompositions. Finally, we contrast secondary cluster ion distributions with those obtained using other cluster sources and we discuss in detail possible origins of the large cluster ions observed in these studies.