Development of multiple chemical tools for deoxynucleic acid (DNA) labeling has facilitated wide use of their functionalized conjugates, but significant practical and methodological challenges remain to achievement of site-specific chemical...

Bioconjugation of carbohydrates has advanced the modern chemical biology and medical science research by incorporation of desired functionalities to the oxygen-rich biomolecules. However, the labeling process or selective chemical reaction of carbohydrates have been a challenging task because of their chemical, functional, and structural diversities, and no single chemical modification tool can be universally applicable to all the target substrates in different environments. In this report, we have developed a bioconjugation strategy for labeling of carbohydrate derivatives through a phosphine-mediated three-component coupling reaction in an ionic liquid medium. The multiple characterization methods identified a urea group as the reaction product of the phosphine-mediated coupling through the installation of carbonyl group from carbon dioxide in air and loss of nitrogen gas from the azide group. We have developed purification protocols to facilitate the cleanup and analysis of ionic liquid-based bioconjugation processes, which can be used for a diverse set of carbohydrate derivatives. The phosphine-mediated urea-forming reaction was applied to a variety of amine- and azide-containing carbohydrates such as antibiotics, anti-tumor agent, and polysaccharide with corresponding azide- and amine-based reagent, respectively. The ionic liquid-based bioconjugation was amenable for the chemical modification of the mammalian cell lysate in an azide-dependent manner. Thus, the present report represents not only the advancement of the nonaqueous bioconjugation method for carbohydrate derivatives from the reaction development perspectives, but also their practical utility for creation of carbohydrate conjugates as well as a study tool of the biomolecule through the bioorthogonal chemistry-like reactivity.

Correction for ‘Site-specific DNA functionalization through the tetrazene-forming reaction in ionic liquids’ by Seiya Ishizawa et al., Chem. Sci., 2022, 13, 1780–1788, https://doi.org/10.1039/d1sc05204g.

Development of multiple chemical tools for deoxynucleic acid (DNA) labeling has facilitated wide use of their functionalized conjugates, but significant practical and methodological challenges remain to achievement of site-specific chemical modification of the biomacromolecule. As covalent labeling processes are more challenging in aqueous solution, use of nonaqueous, biomolecule-compatible solvents such as an ionic liquid consisting of a salt with organic molecule architecture, could be remarkably helpful in this connection. Herein, we demonstrate site-specific chemical modification of DNAs through a tetrazene-forming amine-azide coupling reaction using an ionic liquid. This ionic liquid-enhanced reaction process has good functional group tolerance and precise chemoselectivity, and enables incorporation into DNA of various useful functionalities such as biotin, cholesterol and fluorophores which could be incorporated into DNA through this method. A site-specifically labeled single stranded nucleotide, or aptamer interacting with a growth factor receptor (Her2) was successfully used in the fluorescence imaging of breast cancer cell lines. The non-traditional medium-promoted labeling strategy described here provides an alternative design paradigm for future development of chemical tools for applications involving DNA functionalization.

Bioconjugation of carbohydrates have been a challenging task because of their chemical, functional, and structural diversities, and no single chemical modification tool can be universally applicable to all the target...