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Electron microscopic observation and rotational diffusion measurement of bacteriorhodopsin in lipid vesicles

  • Kunsheng Hu
  • Aojin Wang
  • Ian E. G. Morrison
  • Richard J. Cherry
Article

Abstract

The morphology of bacteriorhodopsin reconstituted into dimyristoylphosphatidylcholine and egg-phosphatidylcholine vesicles was observed by freeze-fracture electron microscopy. The rotational diffusion of bacteriorhodopsin at different concentrations of melittin was measured by observing flash-induced transient dichroism in dimyristoylphosphatidylcholine vesicles. In the presence of melittin, bacteriorhodopsin molecules in dimyristoylphosphatidylcholine vesicles were aggregated into large particles or patches, and the ability of rotational diffusion of bacteriorhodopsin in vesicles was decreased. This suggests that melittin produces its effect via direct electrostatic interaction with bacteriorhodopsin. Low temperature-induced aggregation of bacteriorhodopsin was also observed in dimyristoylphosphatidylcholine vesicles. Low temperature may cause phase separation. Bacteriorhodopsin was also successfully reconstituted into egg-phosphatidylcholine vesicles, but low temperature-induced aggregation of bacteriorhodopsin in dimyristoylphosphatidylcholine cannot appear in egg-phosphatidylcholine vesicles. This suggests that different lipids have different effects on bacteriorhodopsin in vesicles.

Keywords

Bacteriorhodopsin Melittin electron microscopy rotational diffusion 

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Copyright information

© Science in China Press 2001

Authors and Affiliations

  • Kunsheng Hu
    • 1
  • Aojin Wang
    • 1
  • Ian E. G. Morrison
    • 2
  • Richard J. Cherry
    • 2
  1. 1.Institute of BiophysicsChinese Academy of SciencesBeijingChina
  2. 2.Department of Biological ScienceUniversity of EssexUK

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