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|Title:||Influence of palmitic acid and hexadecanol on the phase transition temperature and molecular packing of dipalmitoylphosphatidyl-choline monolayers at the air-water interface|
|Authors:||Lee, K. Y. C.|
von Nahmen, A.
Zasadzinski, J. A.
Smith, G. S.
Howes, P. B.
|Publisher:||American Institute of Physics|
|Citation:||Journal of Chemical Physics, 2002, 116 (2), pp.774-783|
|Abstract:||Palmitic acid (PA) and 1-hexadecanol (HD) strongly affect the phase transition temperature and molecular packing of dipalmitoylphosphatidylcholine (DPPC) monolayers at the air–water interface. The phase behavior and morphology of mixed DPPC/PA as well as DPPC/HD monolayers were determined by pressure-area-isotherms and fluorescence microscopy. The molecular organization was probed by synchrotron grazing incidence x-ray diffraction using a liquid surfacediffractometer. Addition of PA or HD to DPPC monolayers increases the temperature of the liquid-expanded to condensed phase transition.X-ray diffraction shows that DPPC forms mixed crystals both with PA and HD over a wide range of mixing ratios. At a surface pressure (π) of 40 mN/m, increasing the amount of the single chain surfactant leads to a reduction in tilt angle of the aliphatic chains from nearly 30° for pure DPPC to almost 0° in a 1:1 molar ratio of DPPC and PA or HD. At this composition we also find closest packing of the aliphatic chains. Further increase of the amount of PA or HD does not change the lattice or the tilt.|
|Rights:||Copyright © 2002 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in J. Chem. Phys. 116, 774 (2002); and may be found at http://dx.doi.org/10.1063/1.1420730|
|Appears in Collections:||Published Articles, Dept. of Physics and Astronomy|
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