Controlled Rotation of Lipid Tubules with Optical Tweezers

Chiral Phospholipids are found self-assembled into fascinating cylindrical tubules of 500 nm in diameter by helical winding of bilayer stripes under cooling in ethanol and water solution. Theoretical prediction and experimental evidence reported so far confirmed the modulated tilt direction in a helical striped pattern of the tubules. This molecular orientation morphology results in optically birefringent tubules. We manipulated birefringent lipid tubules under 532 nm linearly polarized laser tweezers. Spontaneous rotation of lipid tubules induced by radiation torque was observed with only one sense of rotation caused by chirality of lipid tubules. Rotation discontinues once the high index axis of lipid tubule aligned with a polarization axis of the laser. Thus, by controlling the direction of linearly polarized light, angle of tubule rotation can be specified. This observation holds promising applications in nano-and bio-technologies.