title: The mobility of single-file water molecules is governed by the number of H-bonds they may form with channel-lining residues.
abstract: Channel geometry governs the unitary osmotic water channel permeability,pf, according to classical hydrodynamics. Yet,pfvaries by several orders of magnitude for membrane channels with a constriction zone that is one water molecule in width and four to eight molecules in length. We show that both thepfof those channels and the diffusion coefficient of the single-file waters within them are determined by the numberNHof residues in the channel wall that may form a hydrogen bond with the single-file waters. The logarithmic dependence of water diffusivity onNHis in line with the multiplicity of binding options at higherNHdensities. We obtained high-precisionpfvalues by (i) having measured the abundance of the reconstituted aquaporins in the vesicular membrane via fluorescence correlation spectroscopy and via high-speed atomic force microscopy, and (ii) having acquired the vesicular water efflux from scattered light intensities via our new adaptation of the Rayleigh-Gans-Debye equation.
authors.affiliation: Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Horner
authors.affiliation: Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Zocher
authors.affiliation: Center for Advanced Bioanalysis GmbH (CBL), Gruberstr. 40, 4020 Linz, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Preiner
authors.affiliation: Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria.
authors.forename: Nicole
authors.initials: N
authors.lastname: Ollinger
authors.affiliation: Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria.
authors.forename: Christine
authors.initials: C
authors.lastname: Siligan
authors.affiliation: A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr., 31/5, 119071 Moscow, Russia. ; National University of Science and Technology "MISiS," Leninsky pr., 4, 119049 Moscow, Russia.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Akimov
authors.affiliation: Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Pohl