Effect of galactose-substitution-patterns on the interaction properties of galactomannas

A range of galactomannans varying widely in the contents of d-galactose have been compared for self-association and their interaction properties with agarose and xanthan. Whereas, in general, the most interactive galactomannans are those in which the (1→4)-β-d-mannan chain is least substituted by α-d-galactosyl stubs, evidence is presented which indicates that the distribution of d-galactosyl groups along the backbone (fine structure) can have a significant effect on the interaction properties. For galactomannans containing <30% of d-galactose, those which contain a higher frequency of unsubstituted blocks of intermediate length in the β-d-mannan chain are most interactive. For galactomannans containing >40% of d-galactose, those which contain a higher frequency of exactly alternating regions in the β-d-mannan chain are most interactive. This selectivity, on the basis of galactomannan fine-structure, in mixed polysaccharide interactions in vitro could mimic the selectivity of binding of branched plant-cell-wall polysaccharides in biological systems.