Sulphamido-groups

Two methods deserve some comment the use of nitrous acid where sulphamido groups occur and the use of (J-elimination, especially in pectins. Selective acid hydrolysis quite often indicates inhomogenecity in heteropolymers, but is seldom reproducible enough for help with exact sequencing. 

Sulphamido-groups (formerly called A -sulphates) are correctly specified as deoxy-sulphamido-residues. Hence the iV-linked sulphate found on glucosamine in heparinoids is described by 2-deoxy-2 sulphamido glucose , or, in jargon as glucosamine iV-sulphate. 

Sulphamido-groups are indicated by -NS, -NSO4 or -N.OSO3 for example 2-deoxy-2-sulphamido-glucose can be represented as GlcNS etc. 

Figure 4.17 Resonance stabilisation of conjugate base of acetyl sulphamido group.

Para relation with sulphamido group for optimum activity... 

Sulphonamides with unsubstituted ortho and meta positions are more active than ones substituted on these positions because the unsubstituted sulphonamides resemble PABA. The substitution of the sulphamido group at position with... 

Breakdown of the sulphamido group does not occur in alkaline solutions, but strong adds can degrade it (Fig. 4.36). Sulphonamides are generally photosensitive because of the reactivity of the primary amine at position 4. This group is oxidised under the catalytic action of light to produce diazo dimers. 

Direct C-C links between sugars would generally be difficult to form, without problems of steric hindrance and bridges of the C-O-C (ether) type would be more plausible. Likewise, ester linkages between hydroxyl and carboxyl groups are conveivable, as are various forms of (for example) amide, phosphate ester, sulphate ester, or sulphamido-bridges. However, there is... 

The structure required for a polysaccharide to induce the synthesis of a heparin-degrading system by F. heparinum has been studied. It was concluded that the polysaccharide must contain a uronic acid residue (with a free carboxy-group) attached to either a 2-acetamido-2-deoxy- or 2-deoxy-2-sulphamido-hexose residue by an a-(l - 4)-linkage. Neither O- nor A sulphated residues are essential for inducing the synthesis of this enzyme system. The reason why some heparan sulphates are more effective than heparin in inducing enzymic activity was discussed. 

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