Structural formulae of tris(triazolylmethyl)amine-based ligands and BARAC-biotin. BTTAA=2-[4-({bis[(1-tert-butyl-1H-1,2,3-triazol-4-yl)methyl]amino}methyl)-1H-1,2,3-triazol-1-yl]acetic acid, BTTES=2-[4-({bis[(1-tert-butyl-1H-1,2,3-triazol-4-yl)methyl]amino}methyl)-1H-1,2,3-triazol-1-yl]ethyl hydrogen sulfate, TBTA=tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine, THPTA=tris[(1-hydroxypropyl-1H-1,2,3-triazol-4-yl)methyl]amine, BARAC=biarylazacyclooctynone