Figure 7.

Schematic representation of apparent steric hindrance problems associated with ligand density on the nanocrystal surface. Nanocrystals coated only with biotinylated peptides (A) have difficulty binding strepta-vidin bound to a surface probably because of the surface molecular crowding or high density of ligands. Reducing the amount of surface biotin using 1:1 mixtures of biotinylated peptides and nonbiotinylated peptides of similar length (B) does not improve the binding efficiency, the surface being still too crowded. When smaller peptides such as the PEG-modified peptides 9 are mixed with the biotinylated peptides (C) the resulting better exposure of biotin enables efficient binding to streptavidin on surface.