title: Dynamics of proton diffusion within the hydration layer of phospholipid membrane.
abstract: The diffusion of protons at the immediate vicinity of (less than 10 A from) a phospholipid membrane is studied by the application of the laser-induced proton pulse. A light-sensitive proton emitter (8-hydroxypyrene-1,3,6-trisulfonate) was trapped exclusively in the hydration layers of multilamellar vesicles made of egg phosphatidylcholine, and the protons were dissociated by a synchronizing laser pulse. The recombination of the proton with pyranin anion was monitored by time-resolved spectroscopy and analyzed by a diffusion-controlled formalism. The measured diffusion coefficient is only slightly smaller than the diffusion coefficient of proton in bulk water. Modulating the width of the hydration layer by external pressure had a direct effect on the diffusibility of the proton: the narrower the hydration layer, the slower is the diffusion of protons.
authors.affiliation: Department of Biochemistry, Tel Aviv University, Ramat Aviv, Israel.
authors.forename: M
authors.initials: M
authors.lastname: Gutman
authors.forename: E
authors.initials: E
authors.lastname: Nachliel
authors.forename: S
authors.initials: S
authors.lastname: Moshiach
mesh_terms: D001190:Arylsulfonates; D005456:Fluorescent Dyes; D007700:Kinetics; D007834:Lasers; D008081:Liposomes; D010713:Phosphatidylcholines; D011522:Protons
chemical_list: D001190:Arylsulfonates; D005456:Fluorescent Dyes; D008081:Liposomes; D010713:Phosphatidylcholines; D011522:Protons; C005047:pyranine