Diffuse-double layer at a membrane-aqueous interface measured with X-ray standing waves

Michael J. Bedzyk*, G. Mark Bommarito, Martin Caffrey, Thomas L. Penner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

141 Scopus citations


The ion distribution in an electrolyte solution in contact with a charged polymerized phospholipid membrane was directly measured with long-period x-ray standing waves. The 27-angstrom-thick lipid monolayer was supported on a tungsten/silicon mirror. X-ray standing waves were generated above the mirror surface by total external reflection of a 9.8-kiloelectron volt x-ray beam from a synchrotron undulator. The membrane surface, which contained negatively charged phosphate headgroups, was bathed in a dilute ZnCl2 solution. The concentration of Zn2+ in the condensed layer at the membrane surface and the Zn2+ distribution in the diffuse layer were measured as a function of headgroup charge. The Debye length of the diffutse layer varied between 3 and 58 angstroms. The results qualitatively agree with the Gouy-Chapman-Stern model.

Original languageEnglish (US)
Pages (from-to)52-56
Number of pages5
Issue number4951
StatePublished - 1990

ASJC Scopus subject areas

  • General


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