GDP-Fucose-Tz (GDP-Fucose-Am-Tz) is a click chemistry reagent, it contains a Tetrazine group that can undergo an inverse electron demand Diels-Alder reaction (iEDDA) with molecules containing TCO groups. GDP-fucose-Am-Tz and TCO-ssDNA were reacted at a ratio of 1:1 to obtain the final product GDP-fucose-ssDNA.