CF® dye with methyltetrazine reacts with cyclooctene (TCO, methylcyclopropene) containing molecules via copper free click chemistry. This copper free bioorthogonal reaction is useful for labeling live cells, or when there are concerns about native protein function loss with copper in cell extracts. Methyltetrazine has improved chemical stability compared to tetrazine. CF® dyes are Biotium's line of next-generation fluorescent dyes with advantages in brightness, photostability, and conjugate specificity compared to other fluorescent dyes. • Green fluorescent CF®488A dye has excitation/emission at 490/515 nm. • CF®500-Methyltetrazine has excitation/emission at 500/510 nm, and is designed for intracellular copper-free reaction with azide. • Orange fluorescent CF®532 dye has excitation/emission at 527/558 nm. • Orange-red fluorescent CF®555 dye has excitation/emission at 555/565 nm. • Red fluorescent CF®568 dye has excitation/emission at 562/583 nm. • Deep-red fluorescent CF®594 dye has excitation/emission at 593/614 nm. • Far-red fluorescent CF®640R dye has excitation/emission at 642/662 nm. • Far-red fluorescent CF®647 dye has excitation/emission at 650/665 nm. • CF®650-Methyltetrazine has excitation/emission at 650/670 nm, and is designed for intracellular copper-free reaction with azide. • Far-red/near-IR fluorescent CF®680 dye has excitation/emission at 681/698 nm. • Far-red/near-IR fluorescent CF®680R dye has excitation/emission at 680/701 nm.