Figure 7

Functional bioconjugation in a protein-QD system observed by AFM imaging. Reprinted with permission from [21], copyright 2008 American Chemical Society. (A) The arrows indicate single protein molecules of HA-tagged UvrB and primary HA antibody (blue) attached to the surface of a secondary antibody coated quantum dot (white). (B) Functionality of QD-conjugated UvrB can be examined from the effect of the conjugation on protein-DNA binding, which is directly visualized by AFM imaging (amount of UvrB bound per DNA fragment). The arrow indicates a QD-protein-DNA complex. Images are 300 nm × 300 nm. Importantly, the relatively large and hard quantum dots (semiconductor spheres with 6 nm core diameter) clearly stand out in the topography. These images thus demonstrate that QDs can serve as a molecular marker to unambiguously identify the presence and location of a labeled protein in AFM images.