Linear-hyperbranched, heterobifunctional alpha,omega(n) telechelic block copolymers consisting of a linear poly(ethylene glycol) (PEG) chain and a hyperbranched polyglycerol (PG) block have been prepared. in five steps, using a protected amino-functional initiator. The polyfunctionality omega(n) (OH groups) can be adjusted by the degree of polymerization (DPn) of the polyglycerol block. Subsequent introduction of-a single biotin unit by amidation in alpha-position permitted noncovalent bioconjugation with avidin.