Copper‐Chelating Azides for Efficient Click Conjugation Reactions in Complex Media

Abstract

The concept of chelation-assisted copper catalysis was employed for the development of new azides that display unprecedented reactivity in the copper(I)-catalyzed azide-alkyne [3+2] cycloaddition (CuAAC) reaction. Azides that bear strong copper-chelating moieties were synthesized; these functional groups allow the formation of azide copper complexes that react almost instantaneously with alkynes under diluted conditions. Efficient ligation occurred at low concentration and in complex media with only one equivalent of copper, which improves the biocompatibility of the CuAAC reaction. Furthermore, such a click reaction allowed the localization of a bioactive compound inside living cells by fluorescence measurements.

A highly sensitive protocol for microscopy of alkyne lipids and fluorescently tagged or immunostained proteins

“…Thus, the characteristics of the azide detection reagent are likely to have a direct influence on labeling sensitivity. For labeling of cell surface proteins or biomolecules inside the cell (31,32), the introduction of copper-chelating moieties into the azide reporter have greatly enhanced the reaction rate of CuAAC and thus increased its sensitivity. This approach also represents a promising strategy for alkyne lipid detection in membranes.…”

“…Recently, other groups have used picolyl-containing biotin-azide reporters (31,46) or other multidentate chelators (32) for the highly sensitive labeling of various alkynebearing biomolecules and a further development of copper chelators can be expected. It has been shown that a copper ion that is bound very tightly to the azide reporter, and thereby shielded to prevent the generation of reactive oxygen species [see (30)], can be introduced as a complex into living cells (32). This development could potentially pave the way for CuAAC application in live cell imaging.…”

Triazolyl‐Based Molecular Gels as Ligands for Autocatalytic ‘Click’ Reactions

“…[10] Examples of efficientp olytriazole ligands include the tris[(1-benzyl-1H-1,2,3-triazol-4-yl)-methyl]amine (TBTA) or its analogueb earing bulky tert-butyl groups,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 (BTTES), which is described as one of the most efficient ligands for the copper-catalyzeda zide-alkyne cycloaddition (CuAAC) reported so far. [11] TBTAh as also been investigated as ah eterogeneous catalyst for CuAAC after being anchored onto aN ovaSyn TG aminor esin. [9] Polymer solid supports containing Amberlist or terpyridine, silica-supported Cu I catalysts, metal organic frameworks( MOF), or coppero nc harcoal (Cu/C) are othere xamples testedi nh eterogeneousC uAAC.…”

Development of fluorescent cholesterol derivatives for the exogenous introduction of proteins to the plasma membrane

“…tris(triazolylmethyl)amines) were developed. 146,[151][152][153] When these ligand accelerated CuAAC reactions were used in vitro, live cells showed normal functions after the treatment evidencing their applicability in living systems. 146,[151][152][153] The reaction time of CuAAC reaction with these accelerator ligands was optimized for 5-10 min, because in longer reaction time significant cell death was observed.…”

“…146,[151][152][153] When these ligand accelerated CuAAC reactions were used in vitro, live cells showed normal functions after the treatment evidencing their applicability in living systems. 146,[151][152][153] The reaction time of CuAAC reaction with these accelerator ligands was optimized for 5-10 min, because in longer reaction time significant cell death was observed. 146,147,151,154 In Kennedy's work L-histidine (His) was used as accelerator ligand that resulted in a two-to threefold slower reaction as compared to other ligands (e.g.…”