Light Induced Liquid Crystalline Phases in the Lipid Bilayer

Abstract

The cell membrane is one the most well known examples of liquid crystalline behavior in living systems and in recent years more detailed attention has been paid to the different phases which may occur in biologically relevant lipid bilayers. In this paper we examine a ternary lipid mixture formed from DOPC, sphingomyelin, and cholesterol. In such mixtures fluorescence illumination has been shown to induce the formation of large, more ordered domains or ‘rafts’. This mechanism is investigated using fluorescence microscopy and we find the formation of various “soft” structures including the newly discovered “disc instability” is induced by illumination of lipid tubules.

Keywords:

• biological-membranes
• cholesterol
• fluorescence microscopy
• giant vesicles
• model membranes
• phase-separation
• phase-transitions
• rafts
• tubules

Acknowledgments

The authors would like to acknowledge generous funding from the National Science Foundation, through an NSF CAREER award (DMR–BMAT #0745786). Additional support was provided by the Center for Materials Science and Technology (MARTECH) and the Institute of Molecular Biophysics, both at Florida State University.