Quantitative analysis of complex proteins is a challenging task in modern bioanalytical chemistry. Commonly available isotope labels are still suffering from limitations and drawbacks, whereas new metal labels open numerous possibilities in mass spectrometric analyses. In this work, we have developed a new metal labeling strategy to tag glycan structures of proteins, more particularly antibodies. The oligosaccharide glycans were selectively trimmed to the last N-acetylglucosamine to which an artificial azide containing galactose residue was bound. This azide can be used for subsequent cycloaddition of an alkyne. Therefore, we developed a lanthanide-containing macrocyclic reagent to selectively connect to this azido galactose. In summary, the glycan structures of an antibody can be labeled with a metal functionality using this approach. Furthermore, the functionality of the antibodies can be fully maintained by labeling the Fc glycans instead of using labeling reagents that target amino or thiol groups. This approach enables the possibility of using elemental, besides molecular mass spectrometry, for quantitative analyses or imaging experiments of antibodies in complex biological samples.

Open image in new window

复杂蛋白质的定量分析是现代生物分析化学中的一项艰巨任务。常用的同位素标记仍在局限和缺点中，而新的金属标记在质谱分析中开辟了许多可能性。在这项工作中，我们开发了一种新的金属标记策略来标记蛋白质（尤其是抗体）的聚糖结构。将寡糖聚糖选择性修剪至最后一个N-乙酰基葡糖胺，其结合有含半乳糖残基的人工叠氮化物。该叠氮化物可用于随后的炔烃的环加成。因此，我们开发了一种含镧系元素的大环试剂，可以选择性地连接到这个叠氮半乳糖。总之，可以使用这种方法用金属官能团标记抗体的聚糖结构。此外，可以通过标记Fc聚糖而不是使用靶向氨基或硫醇基的标记试剂来完全保持抗体的功能。除了分子质谱分析法外，这种方法还可以将元素用于复杂生物样品中抗体的定量分析或成像实验。

在新窗口中打开图像