title: Local environment and property of water inside the hollow cylinder of a lipid nanotube.
abstract: We investigated the local environment of water confined inside the hollow cylinder of lipid nanotubes (LNTs) by time-resolved fluorescent measurements and attenuated-total-reflectance infrared (ATR-IR) spectroscopy. The LNT was obtained by self-assembly of cardanyl glucosides in water at room temperature and had an open-ended cylindrical nanospace with a diameter of 10-15 nm, a length of 10-100 microm, and hydrophilic inner and outer surfaces. We introduced a fluorescent probe of 8-anilinonaphthalene-1-sulfonate into the confined water and observed an extremely slow dynamic Stokes shift with a correlation time of 1.26 ns, which was 2-3 orders of magnitude longer than that of bulk-phase water. From the peak shift of the fluorescent spectrum, the local solvent polarity (ET(30)) of the confined water was estimated as 50 kcal/mol, which is 20% lower than that in bulk water. ATR-IR measurements showed that the hydrogen-bond network of water inside the LNT was more developed than that in bulk water at room temperature, which is in contrast to the water in other self-assembled confined geometries, such as Aerosol-OT (AOT) reversed micelles.
authors.affiliation: CREST, Japan Science and Technology Agency, Nanoarchitectonics Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562, Japan. hiroharu-yui@aist.go.jp
authors.forename: Hiroharu
authors.initials: H
authors.lastname: Yui
authors.forename: Yanli
authors.initials: Y
authors.lastname: Guo
authors.forename: Kana
authors.initials: K
authors.lastname: Koyama
authors.forename: Tsuguo
authors.initials: T
authors.lastname: Sawada
authors.forename: George
authors.initials: G
authors.lastname: John
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Masuda
authors.forename: Toshimi
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D005960:Glucosides / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D043942:Nanotubes / Q000737:chemistry*; D013057:Spectrum Analysis; D014867:Water / Q000737:chemistry*
chemical_list: D000817:Anilino Naphthalenesulfonates; D005456:Fluorescent Dyes; D005960:Glucosides; D008055:Lipids; D014867:Water; C027132:1-anilino-8-naphthalenesulfonate