Dynamic aspects of biological membranes.

Several aspects of membrane structure and function have been treated in which the dynamic properties of membrane components are particularly significant. The establishment and maintenance of asymmetries across the membrane, and heterogeneities in the plane of the membrane, place certain restrictions on the nature and extent of membrane fluid properties. Long-range order, which may give differential restrictions to rotational versus translational diffusion, requires specific interactions between membrane components that are strong enough to overcome thermal energy. Processes such as membrane fusion are likely to involve local areas in the membrane where certain membrane proteins are sequestered. And finally, the budding of virus membranes by mechanisms that specifically exclude host cell membrane proteins will require specialized interpretations in view of the fluid membrane model. These and other membrane phenomena illustrate the importance of the dynamic properties of membranes.