ABSTRACT
Cell membranes are also composed of a rich diversity of membrane lipids in addition to proteins. Phospholipids can vary in length and saturation of the acyl tails and can feature diverse head groups, and there is also the presence of sterols and other types of lipid molecules. Together, these define the biophysical properties of membranes such as their rigidity, permeability, and viscosity. One property of the bilayer which is particularly well studied is fluidity with three phases usually defined – a gel phase, a liquid-ordered phase with low fluidity, and a liquid-disordered phase of high fluidity. This chapter details how environmentally sensitive membrane dyes can be used to report on and map the biophysical properties of membranes in live cells.
