Bioorthogonal chemistry can be used for the selective modification of biomolecules without interfering with any other functionality present in the cell. The tetrazine ligation is very suitable as a bioorthogonal reaction because of its selectivity and high reaction rates with several alkenes and alkynes. Recently, we described vinylboronic acids (VBAs) as novel hydrophilic bioorthogonal moieties that react efficiently with dipyridyl- s-tetrazines and used them for protein modification in cell lysate. It is not clear, however, whether VBAs are suitable for labeling experiments in living cells because of the possible coordination with, for example, vicinal carbohydrate diols. Here, we evaluated VBAs as bioorthogonal reactants for labeling of proteins in living cells using an irreversible inhibitor of the proteasome and compared the reactivity to that of an inhibitor containing norbornene, a widely used reactant for the tetrazine ligation. No large differences were observed between the VBA and norbornene probes in a two-step labeling approach with a cell-penetrable fluorescent tetrazine, indicating that the VBA gives little or no side reactions with diols and can be used efficiently for protein labeling in living cells.

中文翻译：

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乙烯基硼酸作为有效的生物正交反应物，可在活细胞中进行四嗪的标记。

生物正交化学可用于生物分子的选择性修饰，而不会干扰细胞中存在的任何其他功能。四嗪连接非常适合作为生物正交反应，因为它的选择性和与几种烯烃和炔的高反应速率。最近，我们将乙烯基硼酸（VBA）描述为新型的亲水生物正交基部分，可与二吡啶基s-四嗪有效反应并将其用于细胞裂解物中的蛋白质修饰。但是，尚不清楚VBA是否适合在活细胞中进行标记实验，因为它可能与例如邻位碳水化合物二醇配合使用。这里，我们使用不可逆的蛋白酶体抑制剂评估了VBAs作为生物正交反应物，用于标记活细胞中的蛋白质，并将其反应性与含有降冰片烯的抑制剂的反应性进行了比较，降冰片烯是广泛用于四嗪连接的反应物。在两步标记方法中，可穿透细胞的荧光四嗪标记在VBA和降冰片烯探针之间未观察到较大的差异，这表明VBA与二醇的副反应很少或没有副反应，可有效用于活细胞中的蛋白质标记。