Abstract
By means of Brownian hydrodynamics simulations we show that the tension distribution along the contour of a single collapsed polymer in shear flow is inhomogeneous and above a threshold shear rate exhibits a double-peak structure when hydrodynamic interactions are taken into account. We argue that the tension maxima close to the termini of the polymer chain reflect the presence of polymeric protrusions. We establish the connection to shear-induced globule unfolding and determine the scaling behavior of the maximal tensile forces and the average protrusion length as a function of shear rate, globule size, and cohesive strength. A quasi-equilibrium theory is employed in order to describe the simulation results. Our results are used to explain experimental data for the shear-sensitive enzymatic degradation of von Willebrand factor.
Highlights
The study of the dynamics of polymers in solution has become an important aspect for understanding non-equilibrium processes in biopolymeric systems [1]
By means of Brownian hydrodynamics simulations we show that the tension distribution along the contour of a single collapsed polymer in shear flow is inhomogeneous and above a threshold shear rate exhibits a double-peak structure when hydrodynamic interactions are taken into account
Our results suggest domain opening to be the cleavage rate limiting factor rather than the ADAMTS13 concentration, since the KM is below the physiological value of the ADAMTS13 concentration, which is about CA ≈ 5 nM [30]
Summary
The study of the dynamics of polymers in solution has become an important aspect for understanding non-equilibrium processes in biopolymeric systems [1]. The binding of VWF to exposed collagen at sites of vascular injuries and the simultaneous VWFmediated adhesion of platelets are central steps in primary hemostasis [2,3,4] In this context, the presence of shear or elongational flow constitutes a crucial ingredient as it activates the functional conformation of VWF multimers by inducing a transition from globular to unfolded conformations [5,6,7] and facilitates adhesion to the extracellular matrix [8, 9]. Previous simulation studies elucidated the dynamics and the VWF adsorption behavior [9, 10] and revealed that VWF must exhibit finely adjusted, longlived bonds in order to resist hydrodynamic forces and to allow for shear-induced adhesion [11, 12]. We compare our results with laser tweezer experiments [13] on single A2 domains and argue that the domain opening in shear flow might not be equivalent to the domain unfolding probed by external stretching forces
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