Studies on rationally designed, allosteric, coagulation inhibitors

Heparin is a natural allosteric modulator, with numerous structural and conformational variations leading to many reports of bleeding complications and variations in anticoagulant effects. A flurry of research has been directed towards understanding this puzzle. This work entails the utilization of three unique strategies to further our understanding of this complex issue. Traditional synthetic, biosynthetic and biophysical approaches have failed to conquer the GAG-protein complexity. Computational analysis however could serve as a powerful approach to decipher this dilemma. A dual filter algorithm was incorporated to identify unique hexasaccharide sequences for HCII and AT. Our experimental studies exhibit a good correlation with our computational findings in addition, to the discovery of the first reported heparin based hexasaccharide sequence (HX1) as a potent activator of HCII and AT. In contrast to the enormity of GAG sequences, there appears to be a pattern where rare sequences have been identified to modulate characteristic functions in proteins. Our search led us to a biosynthetically rare GAG residue 2-O-sulfated glucuronic acid (GlcAp2S). Our computational studies indicated elements of selective recognition with coagulation enzymes propelling us towards synthesizing a polymer, HS2S2S enriched in GlcAp2S and GlcNp2S saccharides. Our biological studies indicate its potential in activating AT and HCII in addition to a previously unobserved inhibition of thrombin but not FXa, which is corroborated by our computational studies. These studies therefore showcase the importance of studying rare sequences to further our understanding of differential recognition of proteins of the coagulation cascade. An alternate anticoagulant strategy involves utilization of upstream enzymes like FXIa. Consequently, we devised a rational strategy, which targets the differential hydrophobic domain near the heparin binding sites of proteins through the design of molecules termed as sulfated allosteric modulators. Our endeavor led to the discovery of a library of quinazolin4-(3H)ones) dimers as selective inhibitors of FXIa. We recognized the linker length and geometry to be an important element affecting potency and selectivity. We therefore synthesized a library of 18 dimers using simple reaction schemes. Our inhibition studies do highlight a 9-fold improvement in potency.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Pharmaceutical Sciences

Year dc:date.available

2014

Author dc:creator

• Boothello, Rio

Contributors dc:contributor

• Umesh Desai

• Medicine and Health Sciences
• Pharmacy and Pharmaceutical Sciences

Statement dc:rights

• © The Author

Identifier

https://scholarscompass.vcu.edu/etd/622

OAI identifier oai:identifier

oai:scholarscompass.vcu.edu:etd-1621