Development of bioorthogonal reactions and their applications in bioconjugation

Abstract

Biomolecule labeling using chemical probes with specific biological activities has played important roles for the elucidation of complicated biological processes. Selective bioconjugation strategies are highly-demanded in the construction of various small-molecule probes to explore complex biological systems. Bioorthogonal reactions that undergo fast and selective ligation under bio-compatible conditions have found diverse applications in the development of new bioconjugation strategies. The development of new bioorthogonal reactions in the past decade has been summarized with comments on their potentials as bioconjugation method in the construction of various biological probes for investigating their target biomolecules. For the applications of bioorthogonal reactions in the site-selective biomolecule conjugation, examples have been presented on the bioconjugation of protein, glycan, nucleic acids and lipids.

Scheme 1

Staudinger ligation.

Scheme 2

Copper-catalyzed alkyne-azide cycloaddition (CuAAC).

Scheme 3

Strain-promoted alkyne-azide cycloaddition (SPAAC).

Scheme 4

Tetrazine ligations between tetrazine and trans-cyclooctene (A), norbornene (B), cyclopropene (C).

Scheme 5

Photo-click reaction.

Scheme 6

Site-specific labeling of proteins by genetic coding of cyclopropene and photoclick reaction. Reproduced from reference [38]. CpKRS, CpK-specific aminoacyl-tRNA synthetase; MbtRNA_CUA, methanosarcina barkeri tRNA(CUA).

Scheme 7

(A) Strategy for tissue-specific glycan labeling via protease activation. (i) Ac3ManNAz was released by protease cleavage of caged azidosugar. (ii) The azidosugar was then metabolized into cell-surface glycans. (iii) The azide-modified glycans were then fluorescently labeled through SPAAC; (B) Cleavage process of caged azidosugar. Reproduced from reference [54] (an open-access article by ACS author choice. This is an unofficial adaptation of an article that appeared in an ACS publication. ACS has not endorsed the content of this adaptation or the context of its use).

Scheme 8

Labeling DNA with alkyne (A) or alkene (B) modified nucleotides through CuAAC or tetrazine ligation, respectively.

Figure 1

Cellular DNA were imaged simultaneously by VdU and EdU, reproduced from reference [63]. DAPI stained cellular nucleus; AF-azide stained alkyne-modified DNA; Tamra-Tz stained alkene-modified DNA; Merge means the overlay of these images. Scale bar, 50 µm.