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Pressure-jump X-ray studies of liquid crystal transitions in lipids

Conn, C.E., Ces, O., Heron, A.J., Mulet, X., Shearman, G.C., Templer, R.H. , Seddon, J.M. and Squires, A.M. (2006) Pressure-jump X-ray studies of liquid crystal transitions in lipids. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 364 (1847). pp. 2635-2655. ISSN 1364-503X

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To link to this article DOI: 10.1098/rsta.2006.1844

Abstract/Summary

In this paper, we give an overview of our studies by static and time-resolved X-ray diffraction of inverse cubic phases and phase transitions in lipids. In 1, we briefly discuss the lyotropic phase behaviour of lipids, focusing attention on non-lamellar structures, and their geometric/topological relationship to fusion processes in lipid membranes. Possible pathways for transitions between different cubic phases are also outlined. In 2, we discuss the effects of hydrostatic pressure on lipid membranes and lipid phase transitions, and describe how the parameters required to predict the pressure dependence of lipid phase transition temperatures can be conveniently measured. We review some earlier results of inverse bicontinuous cubic phases from our laboratory, showing effects such as pressure-induced formation and swelling. In 3, we describe the technique of pressure-jump synchrotron X-ray diffraction. We present results that have been obtained from the lipid system 1:2 dilauroylphosphatidylcholine/lauric acid for cubic-inverse hexagonal, cubic-cubic and lamellar-cubic transitions. The rate of transition was found to increase with the amplitude of the pressure-jump and with increasing temperature. Evidence for intermediate structures occurring transiently during the transitions was also obtained. In 4, we describe an IDL-based 'AXCESS' software package being developed in our laboratory to permit batch processing and analysis of the large X-ray datasets produced by pressure-jump synchrotron experiments. In 5, we present some recent results on the fluid lamellar-Pn3m cubic phase transition of the single-chain lipid 1-monoelaidin, which we have studied both by pressure-jump and temperature-jump X-ray diffraction. Finally, in 6, we give a few indicators of future directions of this research. We anticipate that the most useful technical advance will be the development of pressure-jump apparatus on the microsecond time-scale, which will involve the use of a stack of piezoelectric pressure actuators. The pressure-jump technique is not restricted to lipid phase transitions, but can be used to study a wide range of soft matter transitions, ranging from protein unfolding and DNA unwinding and transitions, to phase transitions in thermotropic liquid crystals, surfactants and block copolymers.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:11609
Uncontrolled Keywords:lyotropic liquid crystals, phase transitions, hydrostatic pressure, X-ray diffraction , BICONTINUOUS CUBIC PHASES, ACID PHOSPHATIDYLCHOLINE MIXTURES, MINIMAL-SURFACES, MODEL BIOMEMBRANES, BLOCK-COPOLYMERS, WATER SYSTEM, MESOPHASES, DIFFRACTION, KINETICS, LAMELLAR
Additional Information:Meeting on New Directions in Liquid Crystals Royal Society of Medicine, London, ENGLAND 5-6 Dec 2005
Publisher:Royal Society Publishing

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