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ACS Nano. 2012 Dec 21;6(12):11080-7. doi: 10.1021/nn304793z. Epub 2012 Dec 5.

Quantum dot targeting with lipoic acid ligase and HaloTag for single-molecule imaging on living cells.

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  • 1Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 18-496, Cambridge, Massachusetts 02139, USA.


We present a methodology for targeting quantum dots to specific proteins on living cells in two steps. In the first step, Escherichia coli lipoic acid ligase (LplA) site-specifically attaches 10-bromodecanoic acid onto a 13 amino acid recognition sequence that is genetically fused to a protein of interest. In the second step, quantum dots derivatized with HaloTag, a modified haloalkane dehalogenase, react with the ligated bromodecanoic acid to form a covalent adduct. We found this targeting method to be specific, fast, and fully orthogonal to a previously reported and analogous quantum dot targeting method using E. coli biotin ligase and streptavidin. We used these two methods in combination for two-color quantum dot visualization of different proteins expressed on the same cell or on neighboring cells. Both methods were also used to track single molecules of neurexin, a synaptic adhesion protein, to measure its lateral diffusion in the presence of neuroligin, its trans-synaptic adhesion partner.

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