Conformational characteristics of $β$-glucan in laminarin probed by terahertz spectroscopy

We measured the binding-state-dependent power absorptions, refractive indices, and dielectric constants of triple-stranded helices (TSHs) and single-stranded helices (SSHs) $β$-glucans in laminarin using terahertz time-domain spectroscopy (TDS). The SSH $β$-glucan was obtained from a TSH $β$-glucan laminarin by a chemical treatment with NaOH solution. The power absorption of TSH $β$-glucan increased more rapidly than that of the SSH $β$-glucan with the frequency increment. The refractive index and dielectric constants of TSH $β$-glucan were also larger than those of the SSH $β$-glucan. This result implies that terahertz-TDS is a very effective method in classifying the conformational state of $β$-glucans.