title: Hydration-scanning tunneling microscopy as a reliable method for imaging biological specimens and hydrophilic insulators.
abstract: The recently discovered high lateral conductivity of molecularly thin adsorbed water films enables investigation of biological specimens, and even of surfaces of hydrophilic insulators by scanning tunneling microscopy (STM). Here we demonstrate the capabilities of this method, which we call hydration-STM (HSTM), with images of various specimens taken in humid atmosphere: We obtained images of a glass coverslip, collagen molecules, tobacco mosaic virus, lipid bilayers and cryosectioned bovine achilles tendon on mica. To elucidate the physical mechanism of this conduction phenomenon we recorded current-voltage curves on hydrated mica. This revealed a basically ohmic behavior of the I-V curves without a threshold voltage to activate the current transport and indicates that electrochemistry probably does not dominate the surface conductivity. We assume that the conduction mechanism is due to structuring of water at the surface.
authors.affiliation: Max-Planck-Institut für Biochemie, Abt. Molekulare Strukturbiologie, Martinsried, Germany. heim@alf.biochem.mpg.de
authors.forename: M
authors.initials: M
authors.lastname: Heim
authors.forename: R
authors.initials: R
authors.lastname: Eschrich
authors.forename: A
authors.initials: A
authors.lastname: Hillebrand
authors.forename: H F
authors.initials: HF
authors.lastname: Knapp
authors.forename: G
authors.initials: G
authors.lastname: Cevc
authors.forename: R
authors.initials: R
authors.lastname: Guckenberger
mesh_terms: D000538:Aluminum Silicates; D000818:Animals; D002417:Cattle; D003094:Collagen / Q000648:ultrastructure; D004553:Electric Conductivity; D004563:Electrochemistry; D005898:Glass; D008051:Lipid Bilayers; D016252:Microscopy, Scanning Tunneling / Q000379:methods*; D013499:Surface Properties; D013710:Tendons / Q000648:ultrastructure; D014027:Tobacco Mosaic Virus / Q000648:ultrastructure; D014867:Water
chemical_list: D000538:Aluminum Silicates; D008051:Lipid Bilayers; D014867:Water; D003094:Collagen; C011934:mica