title: Anomalous water molecules and mechanistic effects of water nanotube clusters confined to molecular porous crystals.
abstract: The movement of water molecules in the limited space present within nanoscale regions, which is different from the molecular motion of bulk water, is significantly affected by strong interfacial interactions with the surrounding outer walls. Hence, most of the water molecules that are confined to nanochannel spaces having widths less than ca. 2 nm can generally be classified together as "structural water". Since the motions of such water molecules are limited by interfacial interactions with the outer wall, the nature of structural water, which is strongly influenced by the interactions, will have different characteristics from normal water. For our investigations on the characteristics of structural water, we have developed a nanoporous crystal with a diameter of ca. 1.6 nm; it was constructed from 1-D hydrophilic channels by self-organization of the designed molecules. A tubelike three-layered water cluster, called a water nanotube (WNT), is formed in each internal channel space and is regulated by H-bonds with the outer wall. The WNT undergoes a glass transition (T(g) = 107 K) and behaves as a liquid; it freezes at 234 K and changes into an icelike nanotube cluster. In this study, the structure of the WNT is investigated through neutron structure analysis, and it is observed to stabilize by a mechanistic anchor effect of structural water. Furthermore, from neutron-scattering experiments, it is seen that a few water molecules around the center of the WNT move approximately with the same diffusion constant as those in bulk water; however, the residence time and average jump length are longer, despite the restrictions imposed by the H-bonding with structural water. The behavior of mobile water within a WNT is investigated; this can be used to elucidate the mechanism for the effect of structural water on vital functions on the cell surface.
authors.affiliation: Department of Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Tadokoro
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohhara
authors.forename: Yuhki
authors.initials: Y
authors.lastname: Ohhata
authors.forename: Takaaki
authors.initials: T
authors.lastname: Suda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Miyasato
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamada
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kikuchi
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tanaka
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kurihara
authors.forename: Masaharu
authors.initials: M
authors.lastname: Oguni
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Nakasuji
authors.forename: Osamu
authors.initials: O
authors.lastname: Yamamuro
authors.forename: Kuroki
authors.initials: K
authors.lastname: Ryota
mesh_terms: D002152:Calorimetry, Differential Scanning; D003035:Cobalt / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D043942:Nanotubes / Q000737:chemistry*; D016062:Porosity; D014867:Water / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D014867:Water; D003035:Cobalt