Coexistence of dilute and densely packed domains of ligand-receptor   bonds in membrane adhesion
  We analyze the stability of micro-domains of ligand-receptor bonds that mediate the adhesion of biological model membranes. After evaluating the effects of membrane fluctuations on the binding affinity of a single bond, we characterize the organization of bonds within the domains by theoretical means. In a large range of parameters, we find the commonly suggested dense packing to be separated by a free energy barrier from a regime in which bonds are sparsely distributed. If bonds are mobile, a coexistence of the two regimes should emerge, which agrees with recent experimental observations. 
Daniel Schmidt, Timo Bihr, Udo Seifert and Ana-Sun\v{c}ana Smith
cond-mat.soft