Oligomers direct mass spectrometry

Especially noteworthy are the methods for determining the sequence of glycosyl residues in a complex oligo- or poly-saccharide. Methods of this type generate a series of overlapping oligomers that are separated and identified by l.c., in conjunction with either direct or indirect mass spectrometry. Most of these methods are still in the developmental stages, and they often require expensive and not-routinely available equipment (see also. Section IV,2) (see Addendum). 

However, the data available suggest that the results obtainable from mass spectrometry will considerably facilitate the structural analysis of oligosaccharides and thus permit direct investigation of the products of partial hydrolysis of polysaccharides on the oligomer level. 

In principle it should be possible to determine M and M , by mass spectrometry, since the technique directly provides the information needed— oligomer molecular weights (AQ and relative abundances (or number of molecules, Field desorption was the first mass spectral method to be used to directly determine molecular weight averages of synthetic polymers (1980). ... 

Direct MS analysis of oligomer mixtures by FAB can be combined with the Collision Induced Dissociation (CID) technique, which is used to induce the fragmentation of selected molecular ions by means of collision with an inert gas (MS/MS). This allows one to obtain daughter ions classical MS/ MS techniques utilize the linked scanning of two or more mass analyzers to obtain product (daughter) and/or precursor (parent) ion spectra see Chapters 1 and 4. Systematic application of tandem Mass Spectrometry (MS/ MS) has produced important results in the analysis of polymeric materials by FAB. " ... 

Due to the insolubility of AP-aggregates, fibril formation could not be analyzed directly by mass spectrometry. In order to determine the molecular composition of aggregates, in gel tryptic digestion and mass spectrometric analysis of the gel electrophoresis bands of Ap-oligomers was performed. AP(l-40) was subjected to fibril growth at 1 J,g/ jL (220 pM) in buffer solution, pH 7.5, and incubated for 5 days at... 

An alternative, and a more elegant approach to analyzing large polymers is to couple a GPC via an electrospray ionization interface to the FT/MS. Each oligomeric fraction that elutes from the GPC would be measured directly by mass spectrometry with minimal interference from the multiple charge states of adjacent oligomers. 

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