Electron impact/desorption mass spectrometry, structural studies

Structural Studies of Neutral Glycosphingolipids of Human Neutrophils by Electron Impact/Desorption Mass Spectrometry... 

At the outset of the structure investigation it was hoped that single-crystal X-ray methods might be successful, particularly with the large alkaloids however, as a number of trials were not promising, the approaches to structures have relied on spectroscopic and chemical methods. Spectroscopic examination involved electron impact, chemical ionization, and field desorption mass spectrometry, H- and C-nuclear magnetic resonance study (sometimes NOE and correlation spectroscopy), and this was followed by isolation of the polyhydroxylated core by alcoholysis or hydrolysis. Core 30 was novel and its structure established spectroscopically 48), whereas euonyminol was characterized as its octaacetate and compared with an authentic sample. 

Mass spectrometry (MS) has not been applied extensively to the study of naturally occurring xanthones, but the mass spectral data provide valuable information about the structure elucidation of xanthones. As well as electron impact MS, which is a routine technique for the structure elucidation of xanthones, recently developed soft ionization techniques, such as desorption-chemical ionization MS (D/CI-MS) and fast atom bombardment MS (FAB-MS), are of great interest for the analysis of glycosides. Molecular ion peaks can be observed without derivatization. Tandem MS/MS can be extensively employed in directly characterizing constituents of complex mixtures. Recently, xanthone profiles of H. perforatum cell cultures were identified by HPLC-MS/MS analysis [106]. 

Puzo G, Tissie G, Lacave C, Aurelle H, Prome JC. Structural determination of cord factor from a Corynebacterium diphtheriae strain by a combination of mass spectral ionization methods field desorption cesium cationization and electron impact mass spectrometry studies. Biomed Mass Spectrom. 1978 5 699-703. 

Mass Spectrometry (MS). MS is one of the key techniques used in structure determination of carbohydrates and analyses via electron impact (E.I.) and chemical ionization (C.I.) methods are performed routinely on low molecular weight permethylated or peracetylated carbohydrates. Recently, MS procedures have found wider application in the structure elucidation of less volatile higher molecular weight oligosaccharides as a result of instrumental developments (in particular, desorption methods of ionization, based on fast atom bombardment (FAB) (93), field desorption (FD), laser desorption (LD), plasma desorption (PD), and secondary ion (SI) mass spectrometry) and improvements in derivatization techniques. For example, a series of malto-oligosaccharides, starch and other glycans have been examined with LD FD-MS (94,95) whilst FAB techniques have been employed for studies of cello- and malto-oligosaccharides (96) and branched cyclo-dextrins (97). 

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