Issue
EPL
Volume 83, Number 2, July 2008
Article Number 28007
Number of page(s) 6
Section Interdisciplinary Physics and Related Areas of Science and Technology
DOI http://dx.doi.org/10.1209/0295-5075/83/28007
Published online 05 July 2008
EPL, 83 (2008) 28007
DOI: 10.1209/0295-5075/83/28007

Mean encounter times for cell adhesion in hydrodynamic flow: Analytical progress by dimensional reduction

C. B. Korn and U. S. Schwarz

University of Heidelberg, Bioquant 0013, Im Neuenheimer Feld 267 - D-69120 Heidelberg, Germany, EU

Ulrich.Schwarz@bioquant.uni-heidelberg.de

received 26 March 2008; accepted in final form 3 June 2008; published July 2008
published online 5 July 2008

Abstract
For a cell moving in hydrodynamic flow above a wall, translational and rotational degrees of freedom are coupled by the Stokes equation. In addition, there is a close coupling of convection and diffusion due to the position-dependent mobility. These couplings render calculation of the mean encounter time between cell surface receptors and ligands on the substrate very difficult. Here we show for a two-dimensional model system how analytical progress can be achieved by treating motion in the vertical direction by an effective reaction term in the mean first passage time equation for the rotational degree of freedom. The strength of this reaction term can either be estimated from equilibrium considerations or used as a fit parameter. Our analytical results are confirmed by computer simulations and allow to assess the relative roles of convection and diffusion for different scaling regimes of interest.

PACS
82.39.-k - Chemical kinetics in biological systems.
47.15.G- - Low-Reynolds-number (creeping) flows.
05.10.Gg - Stochastic analysis methods (Fokker-Planck, Langevin, etc.).

© EPLA 2008