蛋白质糖基化是最重要的翻译后修饰之一，糖蛋白的糖链末端广泛存在着唾液酸。唾液酸在参与分子识别、机体免疫等生理活动及重大疾病的发生发展中起着极其重要作用。然而，不同连接唾液酸糖链在生理病理过程中功能差异显著，因此，唾液酸糖链的精细结构解析具有重要意义。目前尚缺乏全面精准大规模区分不同连接唾液酸的方法，为了突破该技术瓶颈，本项目拟发展基于稳定同位素标记的高灵敏高选择解析不同连接唾液酸质谱新方法，通过对α-2,3与α-2,6连接唾液酸分别进行稳定同位素标记，可保证不同连接唾液酸糖链在相同离子化效率和相同色谱流出时间窗口内，利用同位素质量差异实现α-2,3与α-2,6连接唾液酸的区分，并通过衍生提高唾液酸糖链质谱分析的离子化效率和抗干扰能力。最终建立不同连接唾液酸糖链精准解析新方法，为挖掘大肠癌等重大疾病候选糖链生物标志物提供有效方法和翔实数据。

Protein glycosylation is one of the most important post-translational modifications, and sialic acids are prevalent at the terminal of glycans. Sialic acids are not only associated with various physiological progress such as molecular recognition and immunity, but also serve important roles in diseases development. However, sialic acid linkage isomers play different roles in physiological and pathological conditions. Therefore, it is of great significance to elucidate the fine structure of sialic acid-containing glycans. Currently, methods for comprehensive and accurate discrimination of sialic acid linkages are still lacking. In this project, new approaches based on stable isotope labeling with high-sensitivity and high-specificity would be developed for identifying sialic acid linkage isomers, through linkage-specific derivatization, α-2,3 and α-2,6 sialic acid could be discriminated by mass shift generated from isotope tag with the same ionization efficiency and in the same chromatographic elution window. We will also further develop the derivatization method to enhance the ionization efficiency and improve the interference tolerance of sialic acid-containing glycans. Finally, a new method for comprehensive and accurate identification of sialic acid linkages would be established, which could provide efficient methods and solid data for the discovery of glycan biomarker candidates of diseases such as colorectal cancer.