Molecular weight control of curdlan (β-1,3-glucan polysaccharide) provides unique polynucleotide binding properties

Recently, we found that schizophyllan belonging to a β-1,3-glucan polysaccharide family forms macromolecular complexes with certain single-stranded polynucleotides. The specific complex formation is originated from the β-1,3-glucan skeleton in the main chain. In this paper, we have reported that curdlan, which is a β-1,3-glucan polysaccharide without a side chain glucose unit, shows unique poly(C) binding properties different from those of schizophyllan; in the experiments using curdlan samples with the controlled molecular weight, the complexation ability appeared only in a limited "M_w range window". Stoichiometric analysis revealed that the "Mw range window" appears as a result of the competition between curdlan-curdlan self-association and curdlan-polynucleotide complexation. Furthermore, when the experiments were extended to other polynucleotides such as poly(A), poly(dA) and poly(dT), the "M_w range window" also appeared at their characteristic molecular weights. We believe, therefore, that curdlan can be applicable, in spite of its cheapness, as a precious functional material to gene technology.