Many reagents have been developed for cysteine-specific protein modification. However, few of them allow for multi-functionalization of a single Cys residue and disulfide bridging bioconjugation. Herein, we report 3-bromo-5-methylene pyrrolones (3Br-5MPs) as a simple, robust, and versatile class of reagents for cysteine-specific protein modification. These compounds can be facilely synthesized via a one-pot mild reaction and they show comparable tagging efficiency but higher cysteine specificity than the maleimide counterparts. The addition of cysteine to 3Br-5MPs generates conjugates that are amenable to secondary addition by another thiol or cysteine, making 3Br-5MPs valuable for multi-functionalization of a single cysteine and disulfide bridging bioconjugation. The labeling reaction and subsequent treatments are mild enough to produce stable and active protein conjugates for biological applications.

中文翻译：

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半胱氨酸特定的蛋白质多功能化和使用3-溴-5-亚甲基吡咯烷酮的二硫键桥接。

已经开发出许多用于半胱氨酸特异性蛋白质修饰的试剂。然而，它们中很少有允许单个Cys残基的多功能化和二硫键桥接生物缀合。在这里，我们报告3-溴5亚甲基吡咯烷酮（3Br-5MPs）作为一种简单，健壮和通用的半胱氨酸特异性蛋白修饰试剂。这些化合物可以通过一锅温和的反应轻松合成，并且显示出可比的标记效率，但半胱氨酸特异性高于马来酰亚胺。向3Br-5MPs中添加半胱氨酸可产生适合于另一硫醇或半胱氨酸二次添加的缀合物，使3Br-5MP对于单个半胱氨酸的多功能化和二硫键桥接生物缀合具有重要意义。