title: Fluid shear induces conformation change in human blood protein von Willebrand factor in solution.
abstract: Many of the physiological functions of von Willebrand Factor (VWF), including its binding interaction with blood platelets, are regulated by the magnitude of applied fluid/hydrodynamic stress. We applied two complementary strategies to study the effect of fluid forces on the solution structure of VWF. First, small-angle neutron scattering was used to measure protein conformation changes in response to laminar shear rates (G) up to 3000/s. Here, purified VWF was sheared in a quartz Couette cell and protein conformation was measured in real time over length scales from 2-140 nm. Second, changes in VWF structure up to 9600/s were quantified by measuring the binding of a fluorescent probe 1,1'-bis(anilino)-4-,4'-bis(naphthalene)-8,8'-disulfonate (bis-ANS) to hydrophobic pockets exposed in the sheared protein. Small angle neutron scattering studies, coupled with quantitative modeling, showed that VWF undergoes structural changes at G < 3000/s. These changes were most prominent at length scales <10 nm (scattering vector (q) range >0.6/nm). A mathematical model attributes these changes to the rearrangement of domain level features within the globular section of the protein. Studies with bis-ANS demonstrated marked increase in bis-ANS binding at G > 2300/s. Together, the data suggest that local rearrangements at the domain level may precede changes at larger-length scales that accompany exposure of protein hydrophobic pockets. Changes in VWF conformation reported here likely regulate protein function in response to fluid shear.
authors.affiliation: Chemical and Biological Engineering, State University of New York, Buffalo, New York, USA.
authors.forename: Indrajeet
authors.initials: I
authors.lastname: Singh
authors.forename: Efrosyni
authors.initials: E
authors.lastname: Themistou
authors.forename: Lionel
authors.initials: L
authors.lastname: Porcar
authors.forename: Sriram
authors.initials: S
authors.lastname: Neelamegham
mesh_terms: D000817:Anilino Naphthalenesulfonates; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D009502:Neutrons; D011487:Protein Conformation; D012542:Scattering, Radiation; D013314:Stress, Mechanical; D014841:von Willebrand Factor / Q000737:chemistry*
chemical_list: D000817:Anilino Naphthalenesulfonates; D014841:von Willebrand Factor; C035763:5,5'-bis(8-(phenylamino)-1-naphthalenesulfonate)