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Issue 17, 2009
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Binding cooperativity of membrane adhesion receptors

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The adhesion of cells is mediated by receptors and ligands anchored in apposing membranes. A central question is how to characterize the binding affinity of these membrane-anchored molecules. For soluble molecules, the binding affinity is typically quantified by the binding equilibrium constant K3D in the linear relation [RL] = K3D[R][L] between the volume concentration [RL] of bound complexes and the volume concentrations [R] and [L] of unbound molecules. For membrane-anchored molecules, it is often assumed by analogy that the area concentration of bound complexes [RL] is proportional to the product [R][L] of the area concentrations for the unbound receptor and ligand molecules. We show here (i) that this analogy is only valid for two planar membranes immobilized on rigid surfaces, and (ii) that the thermal roughness of flexible membranes leads to cooperative binding of receptors and ligands. In the case of flexible membranes, the area concentration [RL] of receptor–ligand bonds is proportional to [R]2[L]2 for typical lengths and concentrations of receptors and ligands in cell adhesion zones. The cooperative binding helps to understand why different experimental methods for measuring the binding affinity of membrane-anchored molecules have led to values differing by several orders of magnitude.

Graphical abstract: Binding cooperativity of membrane adhesion receptors

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Publication details

The article was received on 30 Jan 2009, accepted on 21 May 2009 and first published on 03 Jul 2009

Article type: Paper
DOI: 10.1039/B902036E
Soft Matter, 2009,5, 3354-3361

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    Binding cooperativity of membrane adhesion receptors

    H. Krobath, B. Różycki, R. Lipowsky and T. R. Weikl, Soft Matter, 2009, 5, 3354
    DOI: 10.1039/B902036E

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