Synopsis

Measuring Membrane Mechanics

Physics 7, s54
A new method for measuring membrane viscosity allows a closer look at the effect of different proteins on the dynamical properties of the cell.
T. T. Hormel et al., Phys. Rev. Lett. (2014)

Lipid bilayers—flexible two-dimensional fluids of proteins and lipids—govern the dynamics of cell membranes. Understanding the dynamics of these bilayers is important if we want to explain their biological functions. For example, the membrane viscosity sets the time scales for protein diffusion, assembly of signaling complexes, and other processes that rely on two-dimensional motion. Measuring membrane viscosity, however, is notoriously difficult. Writing in Physical Review Letters, Raghuveer Parthasarathy and colleagues from the University of Oregon, Eugene, describe a new technique that can be used to accurately obtain membrane viscosity by probing the diffusion of anisotropic lipid-anchored particles.

Tracers made of paired 100-nanometer-diameter spheres were bound to particular lipids, which were then incorporated into the membrane. The location and orientation of the tracers were found from fluorescence images allowing measurement of both translational and rotational Brownian motion, the combination of which allows the two-dimensional viscosity to be determined. Since the technique only requires the binding of tracers to lipids, it can be applied to a wide variety of membrane systems from simple bilayers to more complex multilayer systems and vesicles.

Using this approach, the authors measured the change in membrane viscosity induced by a particular cargo trafficking protein that, in cells, helps to shape the membranes into curved buds. Surprisingly, they found that this particular protein increased membrane viscosity by more than an order of magnitude. Their results open the door to studying a wide array of mechanical effects induced by individual membrane-active proteins. – Katherine Wright


Subject Areas

Fluid DynamicsBiological Physics

Related Articles

More Informative Together Than Apart
Biological Physics

More Informative Together Than Apart

The concurrent analysis of two measurements of a biochemical signaling network can provide more information than two separate probes of the datasets. Read More »

Brain Asymmetry Driven by Task Complexity
Complex Systems

Brain Asymmetry Driven by Task Complexity

A mathematical model shows how increased intricacy of cognitive tasks can break the mirror symmetry of the brain’s neural network. Read More »

Making Miniature Artificial Cilia
Fluid Dynamics

Making Miniature Artificial Cilia

Researchers have reproduced the wafting motion of hair-like structures on cell surfaces with tiny magnetic rods and a rotating magnetic field. Read More »

More Articles