Figure 1.

Non-selective bioconjugation reaction scheme of carboxylated QDs (QD-COOH) to amine-containing proteins. This two-step reaction involves a) the activation of QD-COOH with EDC/sulfo-NHS, resulting in a semi-stable active ester (QD-NHS), and b) the nucleophilic reaction between the QD-NHS and amine-containing protein, forming a QD-protein conjugate via a stable amide bond.