Nitrilotriacetic acid-derivatized quantum dots for simple purification and site-selective fluorescent labeling of active proteins in a single step.

We demonstrate that QDs coated with nitrilotriacetic acid (NTA) bound to Ni (2+) can be used to reversibly and selectively bind, purify, and fluorescently label His 6-tagged (N-terminal) glutathione S-transferase (GST) in one step with retention of enzymatic activity. We find binding to be less effective in the absence of the His 6-tag or Ni (2+) ions.