Abstract
Lipid bilayer membranes undergo rapid bending undulations with wavelengths from tens of nanometers to tens of microns due to thermal fluctuations. Here, we probe such undulations and the membranes’ mechanics by measuring the time-varying orientation of single gold nanorods (GNRs) adhered to the membrane, using high-speed dark field microscopy. In a lipid vesicle, such measurements allow the determination of the membrane’s viscosity, bending rigidity, and tension as well as the friction coefficient for sliding of the monolayers over one another. The in-plane rotation of the GNR is hindered by undulations in a tension dependent manner, consistent with simulations. The motion of single GNRs adhered to the plasma membrane of living cultured cells similarly reveals the membrane’s complex physics and coupling to the cell’s actomyosin cortex.
Highlights
The plasma membrane of cells serves as a boundary and mediates force transmission and information and material flow between inside and outside, via cytoskeletal adhesion proteins, signal receptor proteins, and endocytic and exocytic vesicle formation
The angular motion of gold nanorods (GNRs) bound to a Huh7 cell is tracked to investigate bending dynamics of a plasma membrane
giant unilamellar vesicles (GUV) were formed by drop casting mixed lipids (Avanti) dissolved in an organic solvent on indium tin oxide (ITO) coated slides, vacuum drying to completely remove the solvent followed by electroformation [18,19] in an aqueous buffer containing 0.3 M sucrose as an osmolyte
Summary
The plasma membrane of cells serves as a boundary and mediates force transmission and information and material flow between inside and outside, via cytoskeletal adhesion proteins, signal receptor proteins, and endocytic and exocytic vesicle formation. We utilize orientational tracking of single gold nanorods (GNRs) to characterize the bending dynamics of reconstituted lipid GUVs and the plasma membrane of cultured cells.
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