Tetrazine-containing biotinylation reagents can be used for the labeling of cyclooctene (e.g. TCO) via Cu(I)-free Click Chemistry.
Two Tetrazine versions with different reactivities and stability characteristics are available to meet specific application requirements. Tetrazine reagents are the ideal choice if a rapid reaction kinetic is the key aspect whereas 6-Methyl-Tetrazine reagents are ideally suited if an improved chemical stability is required . Both biotinylation reagents contain a PEG linker for increased molecule solubility and optimal streptavidin binding.
 Karver et al. (2011) Synthesis and Evaluation of a Series of 1,2,4,5-Tetrazines for Bioorthogonal Conjugations. Am. Chem. Soc. 22:2263.