Analytical ultracentrifugation for characterizing nanocrystals and their bioconjugates

Analytical ultracentrifugation (AU) provides a general way to probe the polydispersity of nanoparticles and the formation of bioconjugates in solution. Unconjugated gold nanocrystals show sedimentation coefficient distributions that are in agreement with size distributions as measured by TEM. AU is sensitive to the size/shape changes elicited by conjugation, in this case to lactose repressor (Lad). AU data reveal saturating protein concentrations for conjugates that correspond to the measured stoichiometry of the complex under these conditions.