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Tethered Vesicles

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Lipid vesicles displaying DNA-lipid A can be tethered via DNA hybridization from a glass supported lipid bilayer displaying the complementary strand, A′.  The tethered vesicles diffuse randomly in the plane parallel to the supported lipid bilayer, as shown in this video taken on an inverted fluorescence microscope.  The colored lines trace the movement of six different vesicles through the video. The diffusion coefficient of tethered vesicles was measured by single particle tracking to be approximately 0.2 μm2/sec.  Vesicles occasionally collide, but are not observed to dock or fuse. 

"Arrays of Mobile Tethered Vesicles on Supported Lipid Bilayers", Chiaki Yoshina-Ishii and Steven G. Boxer, J. Am. Chem. Soc., 125, 3696-3697 (2003). [pdf]


Effect of Electric Field

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When vesicles are tethered to a patterned supported lipid bilayer containing a small percentage of negatively charged lipids, the tethered vesicles move in the direction of electro-osmosis.   In the video on the left, the vesicles first move to one side of the corral (50 μm grid), and upon reversing the direction of the field, the vesicles move the opposite direction.  The negatively charged dye molecules in the supported bilayer move toward the positive electrode by electrophoresis, as seen in the video on the right.   Once the field is removed, the dye molecules then diffuse randomly within the corral.

"Controlling Two-Dimensional Tethered Vesicle Motion Using an Electric Field: Interplay of Electrophoresis and Electro-Osmosis", Chiaki Yoshina-Ishii and Steven G. Boxer, Langmuir, 22, 2384-2391 (2006). [pdf]


Docked Vesicles

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Occasionally, a docking event can be observed between a red vesicle displaying DNA-lipid C and a green vesicle displaying the complement, C′.  This is observed as a colocalization of the red and green false-colored spots, which then continue to diffuse randomly in tandem.  This video was taken using a dual band excitation filter, splitting the emission onto two halves of a CCD, and recombining the red and green emission signals into a single image for each frame.  This allows real time observation of both vesicles simultaneously. 

"Kinetics of DNA-mediated Docking Reactions Between Vesicles Tethered To Supported Lipid Bilayers", Yee-Hung M. Chan, Peter Lenz, and Steven G. Boxer, PNAS, 104, 48, 18913-18918 (2007). [pdf]

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