A versatile strategy has been developed in the preparation of well-defined and site specific protein-glycopolymer bioconjugates via controlled free radical polymerization. The first step involved the preparation of a biotinylated poly(ethylene oxide) atom transfer radical polymerization macroinitiator. Atom transfer radical polymerization (ATRP) was then carried out to generate well-defined biotinylated glycopolymers (M-w/M-n < 1.35). Protein bioconjugation was then achieved using both wild type and mutated streptavidin protein. The resulting bioconjugates have been assessed by fluorescence, gel permeation chromatography and SDS-PAGE and the data obtained were consistent indicating that higher molecular weights biotinylated glycopolymer bind streptavidin protein at a slower rate as compared to free biotin. It was further noted that higher molecular weight and well-defined biotinylated glycopolymer (M-n = 24 kDa) could on average bind to only two binding pockets on streptavidin protein while sterically blocking the other two binding sites. (c) 2006 Elsevier B.V. All rights reserved.