Covalent quantum dot receptor linkage via the acyl carrier protein for single-molecule tracking, internalization, and trafficking studies.

Here we describe a labeling technique for the covalent linkage of quantum dots to transmembrane receptors for single-molecule tracking. Our method combines the acyl carrier protein (ACP) technique with coenzyme A (CoA)-functionalized quantum dots to covalently attach quantum dots to ACP fusions of receptor proteins. The advantages of this approach include: (i) the use of a smaller attachment linker than in many other quantum dot-labeling systems; (ii) the ability to achieve a reliable 1:1 fluorophore-to-receptor labeling stoichiometry; (iii) the specificity of the method; and (iv) the covalent nature of the quantum dot linkage. We demonstrate the general suitability of this technique in single-molecule tracking, internalization, and trafficking studies by imaging two different transmembrane receptors in living cells.