Impact of receptor-ligand distance on adhesion cluster stability |
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Authors: | T Erdmann U S Schwarz |
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Institution: | (1) University of Heidelberg, Im Neuenheimer Feld 293, 69120 Heidelberg, Germany |
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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. |
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Keywords: | PACS" target="_blank">PACS 87 15 -v Biomolecules: structure and physical properties 82 39 -k Chemical kinetics in biological systems 05 10 Gg Stochastic analysis methods (Fokker-Planck Langevin etc ) |
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