Membrane Mechanics and Cell Adhesion

Abstract

Membrane-membrane recognition and adhesion are prominent processes in biology. In general, these events involve specific molecular binding and cross- bridging reactions. Formation of adhesive contact induces tensions in the membranes that ultimately limit the extent of contact. Subsequent separation by physical force also creates stresses that are transmitted through the membrane to the contact zone. The general impression in biology is that the factors that influence cell adhesion simply alter the chemical attraction between opposing membrane surfaces, and that the attraction is the sole determinant of the process. However, closer inspection shows that other physical factors play equally important roles in adhesion-separation processes. Most obvious are the external forces that act on cell or vesicle bodies produced by shear stresses in convecting suspensions. Less obvious, but intrinsically significant, is the mechanical rigidity of the cell or vesicle because it directly regulates the adhesion process. Simply stated: “rigid” bodies have limited ability to adhere (unless they fit together perfectly), whereas “flaccid” or easily deformed bodies can form large contact areas with little energy expense. In this chapter, a brief outline of the mechanical properties of membranes will be given first, followed by a description of the detailed mechanics of cell membrane-membrane adhesion.