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Issue 31, 2013
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Single-molecule observations for determining the orientation and diffusivity of dye molecules in lipid bilayers

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Abstract

The molecular orientation and diffusion of dye molecules in artificial lipid bilayers were observed using total internal reflection fluorescence microscopy. An artificial lipid bilayer composed of a ternary lipid mixture of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), and cholesterol was used. The molecular orientation, which was obtained through defocused imaging, clarified the microscopic features, including cholesterol-induced changes in the local packing structure. Diffusion analysis gave insights into the macroscopic aspects of phase distribution in the heterogeneous bilayer system. Combining these two independent investigations, we revealed the effect of cholesterol addition on microscopic local packing and macroscopic phase structures. Our observations showed a transition from a DLPC-network-like structure to a DPPC-network-like structure upon the addition of cholesterol, which was not evident from previous domain shape observations. The present single-molecule observations yielded the actual phase structure that controls the motion of molecules in the membrane. The results imply that the orientation and diffusivity of molecules offer useful information regarding the phase distribution, which may be hindered by the apparent phase structure in a heterogeneous lipid bilayer that contains cholesterol.

Graphical abstract: Single-molecule observations for determining the orientation and diffusivity of dye molecules in lipid bilayers

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The article was received on 13 Apr 2013, accepted on 30 May 2013 and first published on 28 Jun 2013


Article type: Paper
DOI: 10.1039/C3CP51585K
Phys. Chem. Chem. Phys., 2013,15, 12895-12902

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    Single-molecule observations for determining the orientation and diffusivity of dye molecules in lipid bilayers

    T. Motegi, H. Nabika and K. Murakoshi, Phys. Chem. Chem. Phys., 2013, 15, 12895
    DOI: 10.1039/C3CP51585K

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