Cucurbit[6]uril-Promoted Click Chemistry for Protein Modification

Abstract

Azide-alkyne cycloaddition is a powerful reaction for the formation of bioconjugates. When catalyzed by Cu(I) or strain promotion, this cycloaddition is considered to be a "click" reaction with many applications in chemical biology and materials science. We report a new type of azide-alkyne click chemistry for the synthesis of protein conjugates using cucurbit[6]uril (CB6) supramolecular chemistry. CB6-promoted azide-alkyne cycloaddition has been previously used for the synthesis of rotaxanes but has not been applied to the development of complex bioconjugates. By developing new substrates for CB6 click that do not contain any cross-reactive functional groups and by optimizing reaction conditions, we converted CB6 click chemistry from a rotaxane synthesis tool into a useful bioconjugation technique. Using these new parameters, we synthesized a series of protein conjugates including protein-peptide, protein-DNA, protein-polymer, and protein-drug conjugates. We further demonstrated that CB6 click can be used in conjunction with strain-promoted azide-alkyne cycloaddition to generate distinct bioconjugates in protein mixtures. CB6 click is a promising new reaction for the development of protein conjugates and can be applied toward the synthesis of complex biomaterials for a wide range of applications.

Kinetics Inside, Outside and Through Cucurbiturils

“…[35,116] Since the seminal work by Mock and coworkers in 1989 describing [3 + 2] alkyne-azide cycloadditions catalyzed with CB [6] [117] and subsequent applications, [77,118,119] a large number of studies have shown the potential of the CB[n] family members to promote reactions within their cavity or at their portal, and a majority of those propose solid rationales for the observed rate changes. [120] Recent and thorough reviews by Scherman [101] and Nau, [23] as well as ours a few years earlier [100] cover CB[n]-promoted reactions in detail. [120] Recent and thorough reviews by Scherman [101] and Nau, [23] as well as ours a few years earlier [100] cover CB[n]-promoted reactions in detail.…”

“…We take the advantage here to highlight the remarkable and very recent functionalization of proteins by Francis and coworkers, who managed to prepare protein À DNA, protein À peptide, protein À polymer, and protein À drug conjugates using the CB[6]-catalyzed alkyne-azide cycloaddition. [120] Recent and thorough reviews by Scherman [101] and Nau, [23] as well as ours a few years earlier [100] cover CB[n]-promoted reactions in detail. Those include (1) CB [7]-catalyzed [4 + 4] photodimerizations [121] (2) [2 + 2] cycloadditions of stilbene derivatives, [122][123][124] coumarins [125] and styryl dyes [126] inside CB [8], (3) [4 + 4] cycloadditions of anthracene derivatives inside CB [8]; [127][128][129] (4) the photodimerization of 2naphthalene-carbonitriles [130] and naphthoates; [131] (5) the photoreaction of diazabicylo[2.2.2]alk-2-enes inside CB [7], whose outcomes is strongly influenced by metal cations interacting 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 with the rim of the macrocycle;…”

Probing Reversible Guest Binding with Hyperpolarized 129Xe-NMR: Characteristics and Applications for Cucurbit[n]urils

“…The TMV-rotaxane conjugate (final concentration of 1 µM) was suspended in the supernatant solution and the H2O2 mediated cleavage reaction was monitored by 129 Xe HyperCEST over several hours. Untreated cells (TNF−) remained in the 'turn-off' state even after 8 h, while a stable 'turn-on' response was observed for TNF+ cells after 2 h and lasted until 24 h. This rotaxane-based approach could monitor the low micromolar H2O2 levels in cells using 129 Xe HyperCEST NMR [191,192].…”

Synthesis and Characterization of Cucurbit[6]uril Supported Copper Oxide Nanoparticles, CuO@CB[6]: Application as Nanocatalyst for the Synthesis of 2H‐indazoles

“…It has served as ideal support or as a capping agent for metal nanoparticles . The catalytic activity of CB[6] has been explored elegantly in alkyne‐azide cycloaddition reactions (Click chemistry) for modifications of proteins . Immobilized palladium nanoparticles (CB[6]‐Pd) have been reported as efficient heterogeneous catalysts for Suzuki and Heck reactions, aerobic oxidation of alcohol, and hydrogenation reactions .…”