The crystal structure of cholesterol helical ribbons
Name
197084010-MIT.pdf
Description
Full printable version
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2.51 MB
Format
Adobe PDF
Checksum (MD5)
756bc72b87ab2a3af4317df98d8b2eef
Author(s)
Hossain, Chintan
Advisor(s)
George B. Benedek.
Date Issued
2007
Publisher
Massachusetts Institute of Technology
Abstract
Helical ribbons form in a many multi-component solutions containing sterols similar to cholesterol, but remarkably, almost all the helices have a pitch angle of 11⁰ or 54⁰. The consistent pitch angle of the ribbons may be due to an underlying crystal structure. In order to determine the crystal structure, I undertook x-ray scattering studies of individual helical ribbons taken from two particular solutions: Chemically Defined Lipid Solution and model bile. Using a synchrotron x-ray source I observed Bragg reflections from ribbons with a pitch angle of 11⁰. From the diffraction patterns, I was able to deduce the parameters of the unit cell. The crystal structure of these ribbons is similar to that of cholesterol monohydrate, with the important difference that the length of the unit cell perpendicular to the cholesterol layers is tripled. Furthermore, I found that adjacent layers are shifted relative to each other along a single direction, and that the shift varies periodically with a period of 3 bilayers. I also found that the growth direction of the crystal is along one of the unit cell axes.
Description
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.
Includes bibliographical references (p. 49-50).
Subjects
Physics.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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