Polymerization of nanocrystal quantum dot-tubulin bioconjugates.

Nanocrystal quantum dot (NQD)-tubulin bioconjugates were prepared using a two-step crosslinking procedure. NQD-decorated microtubules were successfully polymerized directly from the NQD-tubulin conjugates to form nonaggregated, full-length (several micrometers) biopolymers. However, polymerization kinetics were slowed in comparison with unmodified tubulin and tubulin modified with small-molecule dyes or biotin. Association with the relatively large nanocrystals, therefore, interferes to some extent with tubulin's ability to polymerize. These results suggest that before NQDs are used extensively as fluorescent labels in studies of biomolecular activity, the impact of NQD bioconjugation must be well understood.