The integration of materials science and nanotechnology with biological sciences and medicine is expected to result in major advances in basic science research and it is expected to yield novel therapeutics. With extensive training in biomaterial synthesis, isolation and characterization (polymers, proteins and blood components), I intend to develop a research program at the interface of materials science and bioengineering. The overall goal is to apply engineering principles, chemical synthesis tools, and physicochemical measurements along with biochemical assays to gain new insight in the field of biomedical sciences. Potential application areas will lie in the fields of cardiovascular research and drug delivery. To this end, the investigation of the detailed structure of biomaterials and its stability or possible conformational changes under different physiological conditions is mandatory. As an example, in this poster, I describe the development of new tools that can be used to examine conformational changes in protein solution structure. The focus is on a single polymeric blood protein called von Willebrand Factor (VWF).

VWF is a large soluble protein in blood. This protein plays an important role in arterial thrombosis, a major cause of death worldwide. The protein plays a key role in this disease processes by aiding platelet deposition at sites of vascular injury. Structural changes in VWF regulate the physiological and pathological function of this protein. We applied two complementary strategies to study the effect of fluid forces on the solution structure of VWF: small angle neutron scattering (SANS) and fluorescence methods. Here, we present a fluorescence study performed in VWF solutions by using the fluorescence probe 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid dipotassium salt (bis-ANS) that partitions into protein hydrophobic domains. We demonstrate that shear-dependent VWF conformational changes in solution are accompanied by exposure of hydrophobic domains within the protein. A marked increase was obtained in bis-ANS binding at shear rates greater than 2300-6000/s and shear times greater than 1min. VWF protein relaxation was observed in those studies over the course of minutes following shear stoppage. In our higher resolution SANS studies structural changes in VWF were detected at shear rates below 3000/s and at length scales less than 10nm.

Overall, the data collected by these studies suggest that local rearrangements at the domain level under physiological shear rates likely precede unfolding of the protein and changes at larger length scales in higher shear rates that accompany exposure of protein hydrophobic pockets. This study introduces new tools to assess structural changes and stability of soluble biomaterials, a major regulator of the function of these molecules.