Triazole biotin: a tight-binding biotinidase-resistant conjugateCelebrating 300 years of Chemistry at Edinburgh.Electronic supplementary information (ESI) available: Synthesis and characterization of azide 6, complexes 7-9, biotinidase activity assay, enrichment of biotinidase from serum, biotinidase stability assay, HABA displacement and ITC binding assays. See DOI: 10.1039/c3ob41837e

The natural amide bond found in all biotinylated proteins has been replaced with a triazole through CuAAC reaction of an alkynyl biotin derivative. The resultant triazole-linked adducts are shown to be highly resistant to the ubiquitous hydrolytic enzyme biotinidase and to bind avidin with dissociation constants in the low pM range. Application of this strategy to the production of a series of biotinidase-resistant biotin-Gd-DOTA contrast agents is demonstrated. Replacing the biotin amide bond with a triazole gives biotinidase-resistant conjugates with the strongest known binding to avidin.