Triple-Helix Conformation of a Polysaccharide Determined with Light Scattering, AFM, and Molecular Dynamics Simulation

The chain conformation of a β-glucan extracted from black fungus (BFP) was studied by static/dynamic light scattering, viscometry, atomic force microscopy (AFM), and molecular dynamics (MD) simulation. The Mark–Houwink equation and the relationship between M w and R g of BFP in water at 25 °C were determined to be [η] = 1.78 × 10–7 M w 1.6 and R g = 5 × 10–4 M w 0.9, and the molar mass per unit contour length (M L) and the persistence length (q) were 2724 ± 276 nm–1 and 230 ± 30 nm, respectively, indicating triple-helix conformation. Moreover, the stiff-chain lengths of the BFP fractions were visualized with AFM images, and their M L values were estimated to give a mean of 2212 nm–1, consistent with the above. Importantly, MD simulation confirmed that the triple helix was the most stable conformation of BFP. We identified, for the first time, the triple-helix chain conformation of BFP and also offered an alternative method for the characterization of the rigid macromolecules.