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Proceedings Paper

Time-resolved x-ray studies of pressure-jump-induced topological transitions in biological membranes
Author(s): Shyamsunder Erramilli; Frederik Osterberg; Sol M. Gruner; Mark W. Tate; Manfred Kriechbaum
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Paper Abstract

Topological transitions in membrane liquid crystals formed by biological lipid-water systems have been the subject of much recent interest. We have developed an x-ray diffraction system capable of initiating pressure jumps of up to 3 kbar in about 5 ms. Time-resolved x-ray diffraction patterns were obtained (approximately 9 ms each) at the National Synchrotron Light Source using two state-of-the-art CCD based detectors developed at Princeton. Numerous Bragg diffraction patterns were obtained in studying the effect of pressure on the simplest topological transitions in membranes, the lamellar to hexagonal phase transition. The patterns from one of the detectors were recorded with a signal-to-noise sufficient to measure peak positions, peak widths, and integrated areas to an accuracy adequate to test models and mechanisms of phase transition kinetics. Additional longer time-scale studies were performed using optical turbidity measurements and were found to be consistent with x-ray studies. Transition rates were found to vary by nearly 5 orders of magnitude as the difference between the final pressure and the equilibrium transition pressure was varied. As the magnitude of the pressure jump in these lyotropic systems is increased, the transition mechanism is determined not only by the rate at which water and lipid molecules transform from one phase to the new emerging phase, but also by the need for water transport. Finally, it was found that the lamellar phase acts as an intermediate phase in transitions between the gel phase and the hexagonal phase, induced by very large pressure jumps (> 2 kbar).

Paper Details

Date Published: 1 September 1995
PDF: 9 pages
Proc. SPIE 2521, Time-Resolved Electron and X-Ray Diffraction, (1 September 1995); doi: 10.1117/12.218351
Show Author Affiliations
Shyamsunder Erramilli, Princeton Univ. (United States)
Frederik Osterberg, Princeton Univ. (United States)
Sol M. Gruner, Princeton Univ. (United States)
Mark W. Tate, Princeton Univ. (United States)
Manfred Kriechbaum, Princeton Univ. (United States)

Published in SPIE Proceedings Vol. 2521:
Time-Resolved Electron and X-Ray Diffraction
Peter M. Rentzepis, Editor(s)

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