Department of Chemistry , University of California, Riverside , 501 Big Springs Road , Riverside , California 92521 , United States.
Department of Molecular Physics , Fritz Haber Institute of the Max Planck Society , Faradayweg 4-6 , 14195 Berlin , Germany.
Anal Chem. 2018 Oct 2;90(19):11581-11588. doi: 10.1021/acs.analchem.8b02958. Epub 2018 Sep 17.
Glycans are fundamental biological macromolecules, yet despite their prevalence and recognized importance, a number of unique challenges hinder routine characterization. The multiplicity of OH groups in glycan monomers easily afford branched structures and alternate linkage sites, which can result in isomeric structures that differ by minute details. Herein, radical chemistry is employed in conjunction with mass spectrometry to enable rapid, accurate, and high throughput identification of a challenging series of closely related glycan isomers. The results are compared with analysis by collision-induced dissociation, higher-energy collisional dissociation, and ultraviolet photodissociation (UVPD) at 213 nm. In general, collision-based activation struggles to produce characteristic fragmentation patterns, while UVPD and radical-directed dissociation (RDD) can distinguish all isomers. In the case of RDD, structural differentiation derives from radical mobility and subsequent fragmentation. For glycans, the energetic landscape for radical migration is flat, increasing the importance of the three-dimensional structure. RDD is therefore a powerful and straightforward method for characterizing glycan isomers.
糖是基本的生物大分子，但尽管它们普遍存在且具有公认的重要性，但仍有一些独特的挑战阻碍了其常规的特征描述。糖单体中多个 OH 基团很容易形成支链结构和不同的连接位点，从而导致仅在细微细节上有所不同的同分异构体结构。在此，自由基化学与质谱相结合，可用于快速、准确、高通量地鉴定一系列具有挑战性的密切相关的聚糖同分异构体。结果与碰撞诱导解离、更高能量的碰撞解离和 213nm 下的紫外光解（UVPD）的分析进行了比较。一般来说，基于碰撞的激活难以产生特征性的碎裂模式，而 UVPD 和自由基定向解离（RDD）可以区分所有异构体。对于糖来说，自由基迁移的能量景观是平坦的，这增加了三维结构的重要性。因此，RDD 是一种用于表征糖异构体的强大而直接的方法。
