Conformational equilibrium of unsulphated iduronate in heparan sulphate tetrasaccharides
Tóm tắt
Proton-proton coupling constants for terminal α-l-iduronate residues in tetrasaccharides obtained from heparan sulphates by complete nitrous acid deaminative cleavage were shown to vary with experimental conditions. It is proposed that the iduronate residue is in a conformational equilibrium between the1C4 chair and either the2So skewboat or possibly the2H3 half-chair conformers. It was not possible to discriminate between the two non-chair forms empirically. The position of the equilibrium is sensitive to temperature, pH and sulphation of neighbouring residues. The likelihood of iduronate residues within glycosaminoglycans existing in the4C1 conformer in addition to the1C4 and2So forms is discussed.
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