title: Relaxation of ultralarge VWF bundles in a microfluidic-AFM hybrid reactor.
abstract: The crucial role of the biopolymer "Von Willebrand factor" (VWF) in blood platelet binding is tightly regulated by the shear forces to which the protein is exposed in the blood flow. Under high-shear conditions, VWFs ability to immobilize blood platelets is strongly increased due to a change in conformation which at sufficient concentration is accompanied by the formation of ultra large VWF bundles (ULVWF). However, little is known about the dynamic and mechanical properties of such bundles. Combining a surface acoustic wave (SAW) based microfluidic reactor with an atomic force microscope (AFM) we were able to study the relaxation of stretched VWF bundles formed by hydrodynamic stress. We found that the dynamical response of the network is well characterized by stretched exponentials, indicating that the relaxation process proceeds through hopping events between a multitude of minima. This finding is in accordance with current ideas of VWF self-association. The longest relaxation time does not show a clear dependence on the length of the bundle, and is dominated by the internal conformations and effective friction within the bundle.
authors.affiliation: University of Augsburg, Experimental Physics I, Biological Physics Group, Universitaetstr. 1, D-86159 Augsburg, Germany.
authors.forename: D M
authors.initials: DM
authors.lastname: Steppich
authors.forename: J I
authors.initials: JI
authors.lastname: Angerer
authors.forename: J
authors.initials: J
authors.lastname: Opfer
authors.forename: K
authors.initials: K
authors.lastname: Sritharan
authors.forename: S W
authors.initials: SW
authors.lastname: Schneider
authors.forename: S
authors.initials: S
authors.lastname: Thalhammer
authors.forename: A
authors.initials: A
authors.lastname: Wixforth
authors.forename: A
authors.initials: A
authors.lastname: Alexander-Katz
authors.forename: M F
authors.initials: MF
authors.lastname: Schneider
mesh_terms: D003198:Computer Simulation; D004548:Elasticity; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D018625:Microscopy, Atomic Force / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000648:ultrastructure; D011487:Protein Conformation; D013314:Stress, Mechanical; D014841:von Willebrand Factor / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D046912:Multiprotein Complexes; D014841:von Willebrand Factor