Nucleophilic Trapping Nitrilimine Generated by Photolysis of Diaryltetrazole in Aqueous Phase

Abstract

Abstract:Nitrilimine generated by photolysis of diaryltetrazole in aqueous phase under mild conditions was trapped by nucleophiles including amines and thioalcohols. The representative products were characterized, while products with all 20 natural amino acids and a peptide were observed by MALDI-TOF mass spectroscopy. Competitive studies showed that this reaction also occurred in the presence of acrylamide. These results provided new information for understanding the potential side reactions when tetrazole-alkene pairs were used as a bioorthogonal reaction in labeling proteins and related studies in buffered systems.

Fully degradable protein nanocarriers by orthogonal photoclick tetrazole–ene chemistry for the encapsulation and release

“…Recently, the bioorthogonality of the tetrazole-ene cycloaddition has been doubted, since the nitrile imine intermediate can also react with strong nucleophiles under certain conditions. [34][35][36][37] Nevertheless, the use of highly reactive dipolarophiles such as strained norbornene derivatives and the confinement of the reaction at the interface of two liquids can decrease the probability for cross-reactivity. Since tetrazoles react readily with strained double bonds, 30 we prepared a difunctional norbornene crosslinker (DN1, Fig.…”

Photo-induced conjugation of tetrazoles to modified and native proteins

“…In our case, the reaction appears to be specific to tryptophan and therefore does not seem to be affected by quenching by amines, which are ubiquitously present. We suggest that this may result from the reaction stoichiometry (an excess of nucleophile in the case of Zhao et al versus equimolar or excess amounts of tetrazole in the present study) and the use of aqueous buffer, which is known to accelerate cycloaddition, 17 as a result of the use of fully water soluble PEG-tz. Very likely, the protein environment may play a role as well.…”

“…[11][12][13][14][15][16] The reaction has the additional benefit of giving rise to a fluorescent linker moiety (a pyrazoline) which makes in-vivo reactivity easy to monitor. Although having received some initial attention from different groups, it has lagged behind in types of applications reported, perhaps because it has been shown to be quenched by high concentrations of amines and carboxylic acids, which evidently are ubiquitous in biological systems, as has recently been investigated into some detail by Zhao et al 17 Still, its high rate, photo-inducibility and the fluorescence of the resulting pyrazoline pose some genuine advantages for niche areas where conjugation is difficult to induce and monitor otherwise such as under in-vivo conditions.…”

Tuning Tetrazole Photochemistry for Protein Ligation and Molecular Imaging

“…In conclusion, the experiments provide irrefutable evidence that a direct photochemical conjugation occurs between the light‐induced nitrile imine and the protein. The nature of the conjugate bonds formed remain uncertain but others have reported convincing evidence that carboxylate, amine and sulfhydryl nucleophiles from amino acids including Glu, Asp, Lys and Cys can attack the nitrile imine intermediate (Scheme S9) [17–21] . Tetrazole photochemistry can be adapted for labelling mAbs in the presence of standard formulation buffers (containing high concentrations of trehalose, polysorbate, ascorbic acid, histidine, etc.).…”