Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (08): 2008-2014.doi: 10.3866/PKU.WHXB201205171

• BIOPHYSICAL CHEMISTRY • Previous Articles    

Structural Properties of the Liquid Ordered Phase of Phosphatidylcholine/Stigmasterol Liposomes: A Synchrotron X-Ray Diffraction Study

WU Rui-Guang1,2, CHEN Lin1, YU Zhi-Wu1   

  1. 1. Key Laboratory of Bioorganic Phosphorous Chemistry & Chemical Biology of the Ministry of Education, Department of Chemistry, Beijing 100084, P. R. China;
    2. School of Chinese Material Medica, Beijing University of Chinese Medicine, Beijing 100102, P. R. China
  • Received:2012-04-09 Revised:2012-05-17 Published:2012-07-10
  • Contact: YU Zhi-Wu E-mail:yuzhw@tsinghua.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20633080, 21133009).

Abstract:

The properties of the liquid ordered (Lo) phase of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/stigmasterol liposomes were investigated using synchrotron small-angle and wide-angle X-ray diffraction techniques. The lamellar repeat distance of the Lo phase, derived from small-angle X-ray scattering experiments, changes slightly with sterol concentration and temperature. While the d-spacings of the acyl chains, evaluated from wide-angle X-ray scattering data, show a much broader range than those of the gel and liquid-crystal phases, varying from 0.422 to 0.460 nm when the temperature increases from 30 to 52 °C. The electron density profiles show that the bilayer thickness and the water-layer thickness of the liquid-ordered phase are larger than that of the liquid-crystal phase, and the bilayer thickness of the liquid-ordered phase decreases with increasing temperature. The results of this study are of help in understanding the phase state and the ordered structure of biomembranes.

Key words: Liquid ordered phase, Lipid raft, Stigmasterol, 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine, X-ray diffraction, Small-angle scattering, Electron density

MSC2000: 

  • O641