The crystal structure of cholesterol helical ribbons

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.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Hossain, Chintan

Advisor dc:contributor.advisor

• George B. Benedek.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/40897

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/40897