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. Author manuscript; available in PMC: 2013 Jan 18.
Published in final edited form as: J Am Chem Soc. 2012 Jan 5;134(2):792–795. doi: 10.1021/ja209325n

Figure 1.

Figure 1

Two-step, site-specific fluorescence labeling of proteins using lipoic acid ligase (LplA) and Diels-Alder cycloaddition. (A) Optimized labeling scheme. In the first step, the Trp37→Val mutant of LplA ligates transcyclooctene TCO2 onto LplA acceptor peptide (LAP), which is fused to the protein of interest. In the second step, ligated trans-cyclooctene is chemoselectively derivatized with a fluorophore conjugated to Tz1 tetrazine. (B) Three transcyclooctenes synthesized and evaluated in this study. (C) Two tetrazines used in this study.