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ORCID

https://orcid.org/0009-0009-4476-812X

Access Type

Open Access Thesis

Document Type

thesis

Embargo Period

2-23-2024

Degree Program

Biomedical Engineering

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2024

Month Degree Awarded

February

Abstract

Von Willebrand factor (VWF) is one of the largest and most complex glycoproteins. It is the main player in maintaining hemostasis at injury sites in the blood vessels as it bridges the interaction between blood platelets and the extracellular matrix (ECM). VWF acts as a mechanosensor in high-shear surroundings, leading to a conformational change in its domains. VWF is a mosaic protein with many different domains that are receptors to the proper ligands on the blood platelets. The A1 domain is the initial point of contact between the VWF and the blood platelets as it binds to the glycoprotein 1b- α (GPIbα), followed by the binding between the C4 domain and the GP2b3a. Intermolecular interactions between the A1 domain and the surrounding mucinlike linkers modulate the interaction between the A1 and the GPIb-α. Here, we present the effect of C- and the N-linkers on the A1 vs. GPIb- α interactions. Using atomic force microscopy, we proved that removing the sialic acid in the AIM enhances the binding frequency, strengthens the bond, and changes its conformation. We also verified that botrocetin hinders the effect of the AIM on this binding. We demonstrated that N-linked iv glycans in the A2 domain affect the stability of the bond by decreasing the bond strength, although it increases the binding frequency when using the A1A2A3 fragment. In contrast, the sialic acid in the C-linker does not affect the binding frequency but decreases the bond strength. The interaction between the C4 domain and the GP2b3a is the final step to ensure the formation of the platelet plug in bleeding. We proved that the bond formed is affected by the arginine-glycine-aspartic (RGD) sequence near the GP2b3a binding site in the C4 domain. The point mutations in the RGD sequence (F2561T &F2561S) enhance the conformation change of the VWF by exposing the GP2b3a binding epitope in the C4 domain, leading to increasing the binding frequency between the C4 in a VWF dimer and the GP2b3a.

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