Sugar linkage analysis

Methylation (linkage) analysis To determine linkages between sugars. 

The elucidation of the structure of polysaccharides and of the carbohydrate portion of glycoconjugates involves sugar analysis, linkage analysis, and the determination of anomeric configurations and the sequences of the sugar residues. When non-sugar substituents are present, these should also be identified and located. 

The limited quantities available ofLPS from MO 19,0 3 and 0 6 strains were insufficient to establish the formal connection of tliis outer heptoglycan to the core OS region. However, on the basis of linkage analysis, the following sugar residues, additional to those already placed in the outer O chains heptoglycan and the inner core OS regions, remained to be accommodated. Two types of units were those of... 

Methylation analysis is the most important procedure for linkage analysis in carbohydrate-containing polymers (Lindberg, 1972). The procedure requires that all free hydroxyl in the oligo- or polysaccharide are etheri-fied. Following depolymerization of the methylated material, the monomers are separated, identified, and quantified. The free hydroxyl groups in the partially methylated monomers mark the position(s) at which the sugar residues were substituted. 

CWM was then extracted sequentially with water at 80 and with ammonium oxalate at 80, delignified with acidified sodium chlorite at 70 , and then further extracted with M and 4M sodium hydroxide. The crude polysaccharide extracts were likewise analyzed for constituent sugars and uronic acid (Table II). In order to obtain defined polysaccharide fractions the following separations were attempted. Polysaccharide fraction A was separated by ion-exchange chromatography on diethylaminoethyl(DEAE)-Sephadex A-50 and the neutral fraction afforded a virtually pure arablnan ( in Scheme 2) after selective precipitation with cetyltrimethylammonium hydroxide (7 ). Linkage analysis by methylation confirmed that this arablnan was of the highly branched type associated with pectins for which the representative, but not unique, structure (J ) may be advanced. 

Linkage analysis of pectins by methylation, designed to avoid the twin problans of base-catalyzed degradation during methylation and sugar decomposition under conditions required for... 

A GC/MS method, commonly called linkage analysis or methylation analysis, has also proven to be a successful approach to determining interresidue linkage and branch points [14]. It involves complete alkylation of all free hydroxyl groups. The fully methylated oligosaccharides are hydrolyzed into monomers, which are further reduced and acetylated to provide partially methylated alditol acetates (PAMAs). Acetylation takes place at those positions that were newly exposed by hydrolysis and reduction. The GC retention times and fragmentation patterns can reveal the mode of attachment in the native sugar. 

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