Static Water Structure Detected by Heat Capacity Measurements on Aqueous Solutions of a Triple-Helical Polysaccharide Schizophyllan

Abstract

Heat capacity measurements were made on aqueous solutions of a triple-helical polysaccharide schizophyllan by precision adiabatic calorimetry over a wide range of concentrations 30.45-90.93 wt % at temperatures between 5 and 315 K. The heat capacity curves obtained were divided into four groups depending on the weight fraction of schizophyllan w regions I-IV. In region I, triple-helices with the sheath of bound water, structured water, and loosely structured water forming layers around the helix core are embedded in free water. In region II, there is no free water, and loosely structured water decreases until it vanishes, but structured water stays constant with increasing w. In region III, bound water remains unaffected, but structured water decreases with increasing w by overlapping each other. Finally, in region IV, only schizophyllan and bound water exist, the latter decreasing upon increasing w. The maximum thickness of each layer is 0.18(3) nm for bound water, 0.13(4) nm for structured water, and 0.23(6) nm for loosely structured water, and these layers of water are at the enthalpy levels of 53%, 93.7%, and nearly 100%, respectively, between ice (0%) and free water (100%).

Immunomodulation of Fungal β-Glucan in Host Defense Signaling by Dectin-1

“…A cross-sectional view of the triple helix of β-glucan in water showed that it has four water boundaries, rendering it difficult to dissolve in water. The approximate diameters of the innermost core and outermost shell of the helix are 1.68 and 2.79 nm, respectively (Yoshiba et al ., 2003). X-ray crystallographic studies showed that the triple helix formation of schizophyllan has a diameter of 2.6 nm and a 1.8-nm pitch.…”

Ordering in aqueous polysaccharide solutions. II. Optical rotation and heat capacity of aqueous solutions of a triple‐helical polysaccharide schizophyllan*

“…This due to the concentration dependence of the transition, as will be discussed in a separate publication. 47 Table II summarizes the solution concentrations and used parameter values. Figure 8 presents a schematic view of the molecular mechanism behind this transition.…”

“…Here C P EX is positive at all ‡ It has been found that the number of unfreezable water molecules is almost constant between w ϭ 0.0448 Ϫ 0.718. 47 This finding along with the very small difference in C p between the annealed and quenched samples is taken to show that schizophyllan is molecularly dispersed even in the frozen state. temperatures and contains the order-disorder transition peak around 290 K. It is suggested that C P EX mainly originates from the interaction between schizophyllan and water, so-called solvation, and so forth, but no detailed molecular mechanism is as yet proposed.…”

“…This aspect will be discussed in detail in a later publication dealing with the concentration dependence of the transition. 47 It is noted that the elucidation of water structure in biological environments by simulations has growing interests and the schizophyllan-water system can be an interesting target among such studies including simulations 50 because of abundant information about possible different structures as discussed here. Here it is assumed that (T)w is the weight fraction of unfrozen or ordered water.…”

Antitumor activity of methylan polysaccharide derivatives

“…3)-b-D-glucans, but neither possesses antitumor properties because both have single helical structures. Yet schizophylalan, pachymaran and carboxymethylpachymaran have marked antitumor activity (Ooi 2009;Yoshiba et al 2003;Chihara et al 1970bChihara et al , 1987Hamuro et al 1971). All have triple helical structures.…”