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Ellipsometry and x-ray reflectivity studies on monolayers of phosphatidylethanolamine and phosphatidylcholine in contact with n-dodecane, n-hexadecane, and bicyclohexyl

Thoma, Martin and Schwendler, Michael and Baltes, Hubert and Helm, Christiane A. and Pfohl, Thomas and Riegler, Hans and Möhwald, Helmuth. (1996) Ellipsometry and x-ray reflectivity studies on monolayers of phosphatidylethanolamine and phosphatidylcholine in contact with n-dodecane, n-hexadecane, and bicyclohexyl. Langmuir, 12 (7). pp. 1722-1728.

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Abstract

Monolayers of the phospholipids 1,2-dipalmitoylphosphatidylethanolamine (DPPE) and 1,2-dipalmitoylphosphatidylcholine (DPPC) are studied at the water/air interface in contact with n-hexadecane, n-dodecane, and bicyclohexyl by null ellipsometry and X-ray reflectivity along the isotherms. From recent diffraction data we derive refractive indices nx and nz to calculate the thickness of the mixed films in the condensed phase by ellipsometry. The thickness is compared with the results from X-ray reflectivity measurements. Both methods reveal that the mixed lipid/hydrocarbon film is not covered by a thin hydrocarbon film as known from short chain alcanes like hexane. The incorporation of the hydrocarbon affects the film thickness by reducing the tilt angle of the lipids. This way DPPC, which due to the large head group does not exhibit a non tilted condensed phase at the water/air interface at all, enlarges its value for nz at the expense of nx, yielding a condensed mixed phase with zero tilt angle. The resulting value for the thickness of the tail region from both methods is always smaller than 21 Å, showing that penetration is strictly limited to the monolayer region.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Biophysikalische Chemie (Pfohl)
UniBasel Contributors:Pfohl, Thomas
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
ISSN:0743-7463
e-ISSN:1520-5827
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:06 Nov 2017 12:33
Deposited On:26 Jan 2017 11:15

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