Polymer-tethered ligand–receptor interactions between surfaces

Authors

  • Jeremy I. Martin,

    1. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
    Current affiliation:
    1. Logic Technology Development, Advanced Micro Devices, Austin, Texas 78741
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  • Cheng-Zhong Zhang,

    1. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
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  • Zhen-Gang Wang

    Corresponding author
    1. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
    • Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
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Abstract

We study the interaction between two parallel surfaces having a polymer-tethered ligand on one and a random distribution of receptors on the other. We examine the interplay between the specific ligand–receptor binding and the conformation degrees of freedom of the polymer tether, and address the difference between the cases of mobile (annealed) and immobile (quenched) receptors. The annealed case is solved exactly and the quenched case is treated by both Monte Carlo direct sampling and an analytical density expansion. The combination of the entropic repulsion due to chain confinement at small surface separations, and the attraction due to ligand–receptor binding which can take place at significant chain stretching, results in a minimum in the interaction free energy. For the same set of parameters, stronger binding is obtained for the annealed case than for the quenched case, reflecting the ability of the mobile receptors to migrate into the region of the ligand. In the quenched case, binding is limited by the availability of receptors within the reach of the ligand; for a given receptor density and binding energy, there exists an optimal chain length that yields the lowest minimum in the interaction free energy for the quenched case. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2621–2637, 2006

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