title: Role of proton gradients in the mechanism of osmosis.
abstract: Experiments were carried out to determine whether the newly identified "exclusion zone" found adjacent to hydrophilic surfaces might play a role in osmosis. Two chambers were juxtaposed face to face, separated by a membrane made of cellulose acetate or Nafion. One chamber contained water, the other 100 mM sodium sulfate solution. Osmotically driven transmembrane fluid flow from low to high salt was observed using both membranes, in agreement with previous reports. Characteristic pH differences and potential differences between chambers were also noted. Visual examination with microsphere markers revealed extensive exclusion zones adjacent to both types of membrane. As these zones routinely generate protons in the water regions beyond, unequal proton concentrations in the respective chambers may be responsible for creating both the pH and potential gradients, which may be ultimately responsible for the osmotic drive.
authors.affiliation: Department of Bioengineering, Box 355061, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhao
authors.forename: Kate
authors.initials: K
authors.lastname: Ovchinnikova
authors.forename: Binghua
authors.initials: B
authors.lastname: Chai
authors.forename: Hyok
authors.initials: H
authors.lastname: Yoo
authors.forename: Jeff
authors.initials: J
authors.lastname: Magula
authors.forename: Gerald H
authors.initials: GH
authors.lastname: Pollack
mesh_terms: D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D009995:Osmosis; D011522:Protons; D013431:Sulfates / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D008567:Membranes, Artificial; D011522:Protons; D013431:Sulfates; D014867:Water; C012036:sodium sulfate