We present a synthetic approach toward soft, glycooligomer-functionalized microgel particles mimicking carbohydrate presenting cell surfaces and analyze their specific binding to a model lectin (Concanavalin A, ConA). Focusing on multivalent presentation, a series of sequence-controlled glycooligomers with varying spacing and number of mannose units was synthesized and analyzed for the resulting glycooligomer-ConA affinity. Both direct binding and inhibition studies show a higher affinity with increasing the number of sugar moieties, but they level off for higher valent systems, indicating steric hindrance. Furthermore, the results suggest that increasing the scaffold length tends to decrease binding due to entropic repulsion, which could be compensated by larger scaffolds able to address multiple ConA binding sites. These findings were consistent in all assays (adhesion, fluorescence, and ITC) regardless of binding partner immobilization, demonstrating that flexible ligands exert similar binding modes in solution and when attached to polymer networks, which is relevant for designing glyco-functionalized materials.
Binding of mannose presenting macromolecules to the protein receptor concanavalin A (ConA) is investigated by means of single‐molecule atomic force spectroscopy (SMFS) in combination with dynamic light scattering and molecular modeling. Oligomeric (Mw ≈ 1.5–2.5 kDa) and polymeric (Mw ≈ 22–30 kDa) glycomacromolecules with controlled number and positioning of mannose units along the scaffolds accessible by combining solid phase synthesis and thiol–ene coupling are used as model systems to assess the molecular mechanisms that contribute to multivalent ConA–mannose complexes. SMFS measurements show increasing dissociation force from monovalent (≈57 pN) to pentavalent oligomers (≈75 pN) suggesting subsite binding to ConA. Polymeric glycomacromolecules with larger hydrodynamic diameters compared to the binding site spacing of ConA exhibit larger dissociation forces (≈80 pN), indicating simultaneous dissociation from multiple ConA binding sites. Nevertheless, although simultaneous dissociation of multiple ligands could be expected for such multivalent systems, predominantly single dissociation events are observed. This is rationalized by strong coiling of the macromolecules' polyamide backbone due to intramolecular hydrogen bonding hindering unfolding of the coil. Therefore, this study shows that the design of glycopolymers for multivalent receptor binding and clustering must consider 3D structure and intramolecular interactions of the scaffold.
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