Structural study for helical biomacromolecular complexes of β,3-D-glucans and polynucleotide by molecular dynamics simulation

It is well known that natural β-1,3-D-glucans take a right-handed 6₁ triple helix in aqueous solution. Recently, the most stable static models of β-1,3-D-glucans and β-1,3-D-glucan/polynucleotides were calculated by using the molecular orbital method to compare their hydrogen bonds, helical pitch and other structural properties. In this paper, we report the molecular dynamics simulation to understand the behavior of β-1,3-D-glucans and β-1,3-D-glucan/polynucleotides in aqueous solution under ambient pressure and at ambient temperature. The helical pitches of β-1,3-D-glucans and β-1,3-D-glucan/polynucleotides were extended by thermal fluctuation, and the degree of extensibility was strongly affected by the number of side chains attached to the β-1,3-D-glucans. The hydrogen bonds via water molecules between the side chain and the main chain and/or the side chain dominated the extension behavior. The extension of the helical pitch of a β-1,3-D-glucan/polynucleotide complex was constrained by the hydrogen bond between the phosphate groups of the polynucleotide and the hydroxyl groups of the β-1,3-D-glucan.