Aldehyde- and ketone-functionalized proteins are promising new substrates for the development of chemically modified biotherapeutics and protein-based materials. Their reactive carbonyl groups are typically conjugated with a-effect nucleophiles, such as substituted hydrazines and alkoxyamines, to generate hydrazones and oximes, respectively. However, the resulting C═N linkages are susceptible to hydrolysis under physiologically relevant conditions, which limits their utility in biological systems. Here we introduce a Pictet-Spengler ligation that is based on the classic Pictet-Spengler reaction of aldehydes and tryptamine nucleophiles. The ligation exploits the bioorthogonal reaction of aldehydes and alkoxyamines to form an intermediate oxyiminium ion; this intermediate undergoes intramolecular C—C bond formation with an indole nucleophile to form an oxacarboline product that is hydrolytically stable. The reaction was utilized for site-specific chemical modification of glyoxal- and formylglycine-functionalized proteins, including an aldehyde-tagged variant of the therapeutic monoclonal antibody Herceptin. In conjunction with techniques for site-specific introduction of aldehydes into proteins, the Pictet-Spengler ligation offers a new means to generate stable bioconjugates for medical and materials applications.
醛和酮官能团化的蛋白质是开发
化学修饰
生物治疗药物和基于蛋白质的材料的有前途的新底物。它们的反应性羰基基团通常与a-效应亲核试剂(如取代的
肼和烷氧胺)共轭,分别生成
肼和
肟。然而,所得到的C═N键在生理条件下易于
水解,这限制了它们在
生物系统中的实用性。在这里,我们介绍了一种基于经典的醛和
色胺亲核试剂的Pictet-Spengler连接反应。该连接反应利用了醛和烷氧胺的
生物正交反应形成中间体氧
肟离子;该中间体通过与
吲哚亲核试剂的分子内C—C键形成,形成一个
水解稳定的氧杂
环丙烷产物。该反应被用于对
丙二醛和甲酰甘
氨酸官能化的蛋白质进行位点特异性
化学修饰,包括治疗性单克隆
抗体Herceptin的醛标记变体。结合蛋白质内醛的位点特异性引入技术,Pictet-Spengler连接反应为生成稳定的
生物共轭物提供了一种新的手段,用于医学和材料应用。