X-ray structural studies of freely suspended ordered hydrated DMPC multimembrane films

• Published in: The Journal of chemical physics 1990-04, Vol.92 (7), p.4519-4529
• Main Authors: SMITH, G. S, SIROTA, E. B, SAFINYA, C. R, PLANO, R. J, CLARK, N. A
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.457764

We have performed x-ray scattering studies of freely suspended, thick (∼2μ), oriented dimyristoyl–phosphatidyl–choline (DMPC)–water multilamellar films with the emphasis on the ordered phases. These stable films were drawn in situ on a triple axis x-ray spectrometer at a controlled, continuously variable temperature (T) and relative humidity (RH). The structure was determined at several temperatures and humidities and a T–RH phase diagram was constructed. We have found that the previously labeled ordered Lβ′ phase is in fact three distinct two-dimensional phases differentiated by the direction of chain tilt with respect to the in-plane lattice. The line shapes of the scattering data indicate that a lower limit of ∼200 Å may be placed on the in-plane chain–chain correlation length, while the chain positions are uncorrelated across the water layers.