Dendrimer-Mediated Molecular Sieving on Avidin

Decoration of proteins and enzymes with well-defined polymeric structures allows precise decoration of protein surfaces, enabling controlled modulation of activity. Here, the impact of dendronization on the interaction between avidin and biotin was investigated. A series of generation 3-7 bis(2,2-hydroxymethyl)propionic acid (bis-MPA) dendrons were coupled to either biotin or avidin to yield a library of dendronized avidin and biotin structures. The thermodynamics of binding each biotinylated generation to a library of avidin conjugates was probed with isothermal titration calorimetry (ITC). Dissociation constants of high-generation biotin-dendrons (G5 and G6) with higher-generation avidin-dendron conjugates (Av-G6) increased from ∼10^-15 M (for the native structures) to ∼10^-6 M, and binding was found to be weaker than that of the Avidin-HABA complex. Avidin-G5 and Avidin-G6 were highly size-selective for biotinylated ligands; both prevented the binding of aprotinin (6.9 kDa), bovine serum albumin (BSA), and PEG₃₄₀₀ while forming fractional complexes with smaller biotinylated dendrons.