title: Hyper-mobility of water around actin filaments revealed using pulse-field gradient spin-echo 1H NMR and fluorescence spectroscopy.
abstract: This paper reports that water molecules around F-actin, a polymerized form of actin, are more mobile than those around G-actin or in bulk water. A measurement using pulse-field gradient spin-echo (1)H NMR showed that the self-diffusion coefficient of water in aqueous F-actin solution increased with actin concentration by ∼5%, whereas that in G-actin solution was close to that of pure water. This indicates that an F-actin/water interaction is responsible for the high self-diffusion of water. The local viscosity around actin was also investigated by fluorescence measurements of Cy3, a fluorescent dye, conjugated to Cys 374 of actin. The steady-state fluorescence anisotropy of Cy3 attached to F-actin was 0.270, which was lower than that for G-actin, 0.334. Taking into account the fluorescence lifetimes of the Cy3 bound to actin, their rotational correlation times were estimated to be 3.8 and 9.1ns for F- and G-actin, respectively. This indicates that Cy3 bound to F-actin rotates more freely than that bound to G-actin, and therefore the local water viscosity is lower around F-actin than around G-actin.
authors.affiliation: Department of Materials Processing, Graduate School of Tohoku University, 6-6-02 Aobayama, Aoba-Ku, Sendai, Miyagi 980-8579, Japan.
authors.forename: Tetsuichi
authors.initials: T
authors.lastname: Wazawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Sagawa
authors.forename: Tsubasa
authors.initials: T
authors.lastname: Ogawa
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Morimoto
authors.forename: Takao
authors.initials: T
authors.lastname: Kodama
authors.forename: Makoto
authors.initials: M
authors.lastname: Suzuki
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry*; D000818:Animals; D002021:Buffers; D002232:Carbocyanines / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D013050:Spectrometry, Fluorescence; D014867:Water / Q000737:chemistry*
chemical_list: D002021:Buffers; D002232:Carbocyanines; D005456:Fluorescent Dyes; C089187:cyanine dye 3; D014867:Water; D003545:Cysteine