Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 22: Cell Mechanics

BP 22.3: Talk

Thursday, February 28, 2008, 11:00–11:15, PC 203

Dynamic states of rolling adhesion: dependance on rates for formation and rupture of molecular bonds — •Christian B. Korn and Ulrich S. Schwarz — University of Heidelberg, Im Neuenheimer Feld 267, D-69120 Heidelberg, Germany

Motivated by rolling adhesion of white blood cells in the vasculature, we study how cells move in linear shear flow above a wall to which they can adhere via specific receptor-ligand bonds. We perform computer simulations based on a Langevin equation accounting for hydrodynamic interactions, thermal fluctuations and adhesive interactions. In contrast to earlier approaches, we resolve both receptor and ligand positions. We identify five different dynamic states of motion in regard to the translational and angular velocities of the cell. We express these states in a state diagram for the parameter subspace spanned by the dynamic rates for bond formation and rupture. In particular, we show that if on- and off-rates are sufficiently balanced the cell’s translational and angular velocities become sychronized. This corresponds to rolling in a macroscopic sense while otherwise the cell is slipping.

In order to analyze the generic interplay between bond formation and rupture, we also define and analytically solve a simple model system based on a one-step master equation. The analytical results show qualitative agreement with the mean velocity data obtained from the computer simulations.