title: 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%).
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Ritsumeikan University, Nojihigashi 1-1-1, Kusatsu, Siga 525-8577, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Yoshiba
authors.forename: Akio
authors.initials: A
authors.lastname: Teramoto
authors.forename: Naotake
authors.initials: N
authors.lastname: Nakamura
authors.forename: Kyo
authors.initials: K
authors.lastname: Kikuchi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Miyazaki
authors.forename: Michio
authors.initials: M
authors.lastname: Sorai
mesh_terms: D002236:Carbohydrate Conformation; D006358:Hot Temperature; D015394:Molecular Structure; D044367:Phase Transition; D012566:Sizofiran / Q000737:chemistry*; D012996:Solutions; D013816:Thermodynamics; D017186:Titrimetry; D014867:Water / Q000737:chemistry*
chemical_list: D012996:Solutions; D014867:Water; D012566:Sizofiran