Eur. Phys. J. E (2007) 22: 123-137
https://doi.org/10.1140/epje/e2007-00019-8

Regular Articles

Impact of receptor-ligand distance on adhesion cluster stability

University of Heidelberg, Im Neuenheimer Feld 293, 69120, Heidelberg, Germany

^* e-mail: Ulrich.Schwarz@iwr.uni-heidelberg.de

Received: 18 December 2006
Published online: 9 March 2007

Abstract

Cells in multicellular organisms adhere to the extracellular matrix through two-dimensional clusters spanning a size range from very few to thousands of adhesion bonds. For many common receptor-ligand systems, the ligands are tethered to a surface via polymeric spacers with finite binding range, thus adhesion cluster stability crucially depends on receptor-ligand distance. We introduce a one-step master equation which incorporates the effect of cooperative binding through a finite number of polymeric ligand tethers. We also derive Fokker-Planck and mean field equations as continuum limits of the master equation. Polymers are modeled either as harmonic springs or as worm-like chains. In both cases, we find bistability between bound and unbound states for intermediate values of receptor-ligand distance and calculate the corresponding switching times. For small cluster sizes, stochastic effects destabilize the clusters at large separation, as shown by a detailed analysis of the stochastic potential resulting from the Fokker-Planck equation.