Studies of Highly-Ordered Heterodiantennary Mannose/Glucose-Functionalized Polymers and Concanavalin A Protein Interactions Using Isothermal Titration Calorimetry

Abstract

Preparations of the highly ordered monoantennary, homofunctional diantennary, and heterofunctional diantennary neoglycopolymers of α-d-mannose and β-d-glucose residues were achieved via ring-opening metathesis polymerization. Isothermal titration calorimetry measurements of these synthetic neoglycopolymers with Concanavalin A (Con A), revealed that heterofunctional diantennary architectures bearing both α-mannose and nonbinding β-glucose units, poly­(Man-Glc), binds to Con A (<i>K</i><sub>a</sub> = 16.1 × 10<sup>6</sup> M<sup>–1</sup>) comparably to homofunctional diantennary neoglycopolymer (<i>K</i><sub>a</sub> = 30 × 10<sup>6</sup> M<sup>–1</sup>) bearing only α-mannose unit, poly­(Man-Man). In addition, poly­(Man-Glc) neoglycopolymer shows a nearly 5-fold increasing in binding affinity compared to monoantennary neoglycopolymer, poly­(Man). Although the exact mechanism for the high binding affinity of poly­(Man-Glc) to Con A is unclear, we hypothesize that the α-mannose bound to Con A might facilitate interaction of β-glucose with the extended binding site of Con A due to the close proximity of β-glucose to α-mannose residues in the designed polymerizable scaffold

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