Rapid and specific labeling of recombinant proteins with
tetrazine–fluorophore
conjugates. (a) Specific labeling of sfGFP bearing 1, 2, or 4 with 11 (10 equiv) demonstrated
by SDS-PAGE and in-gel fluorescence. (b) Quantitative labeling of
sfGFP-1 with 11 demonstrated by ESI-MS.
Before bioconjugation (blue): found, 28018.1 Da; calcd, 28017.6 Da.
After bioconjugation (red): found, 28824.2 Da; calcd, 28823.2 Da.
(c) Quantitative labeling of sfGFP-2 with 11 demonstrated by ESI-MS. Before bioconjugation (blue): found, 27993.2
Da; calcd, 27992.8 Da. After bioconjugation (red): found, 28799.4
Da; calcd, 28799.1 Da. (d) No labeling with 11 of sfGFP-His6 expressed in the presence of 3 could be detected
by MS. (e) Very rapid labeling of proteins containing 1 or 2.