Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
Department of Environmental Health Sciences, University of Georgia, Athens, Georgia 30602, United States.
J Am Soc Mass Spectrom. 2021 Jul 7;32(7):1759-1770. doi: 10.1021/jasms.1c00119. Epub 2021 Jun 6.
Glycosaminoglycans (GAGs) are linear polysaccharides that participate in a broad range of biological functions. Their incomplete biosynthesis pathway leads to nonuniform chains and complex mixtures. For this reason, the characterization of GAGs has been a difficult hurdle for the analytical community. Recently, ultraviolet photodissociation (UVPD) has emerged as a useful tool for determining sites of modification within a GAG chain. Here, we investigate the ability for UVPD to distinguish chondroitin sulfate epimers and the effects of UVPD experimental parameters on fragmentation efficiency. Chondroitin sulfate A (CS-A) and chondroitin sulfate B (CS-B), commonly referred to as dermatan sulfate (DS), differ only in C-5 uronic acid stereochemistry. This uronic acid difference can influence GAG-protein binding and therefore can alter the specific biological function of a GAG chain. Prior tandem mass spectrometry methods investigated for the elucidation of GAG structures also have difficulty differentiating 4- from 6- sulfation in chondroitin sulfate GAGs. Preliminary data using UVPD to characterize GAGs showed a promising ability to characterize 4- sulfation in CS-A GAGs. Here, we look in depth at the capability of UVPD to distinguish chondroitin sulfate C-5 diastereomers and the role of key experimental parameters in making this distinction. Results using a 193 nm excimer laser and a 213 nm solid-state laser are compared for this study. The effect of precursor ionization state, the number of laser pulses (193 or 213 nm UVPD), and the use of the low-pressure versus high-pressure trap are investigated.
糖胺聚糖（GAGs）是参与广泛生物功能的线性多糖。它们不完全的生物合成途径导致了非均一的链和复杂的混合物。因此，GAGs 的特征描述一直是分析界的一个难题。最近，紫外光解（UVPD）已成为确定 GAG 链中修饰位置的有用工具。在这里，我们研究了 UVPD 区分硫酸软骨素差向异构体的能力以及 UVPD 实验参数对碎片化效率的影响。硫酸软骨素 A（CS-A）和硫酸软骨素 B（CS-B）通常被称为硫酸皮肤素（DS），仅在 C-5 糖醛酸立体化学上有所不同。这种糖醛酸差异会影响 GAG-蛋白结合，从而改变 GAG 链的特定生物学功能。用于阐明 GAG 结构的先前串联质谱方法也难以区分硫酸软骨素 GAG 中的 4-和 6-硫酸化。使用 UVPD 对 GAGs 进行特征描述的初步数据表明，其具有表征 CS-A GAGs 中 4-硫酸化的良好能力。在这里，我们深入研究了 UVPD 区分硫酸软骨素 C-5 差向异构体的能力以及关键实验参数在实现这一区分中的作用。本研究比较了使用 193nm 准分子激光器和 213nm 固态激光器的结果。研究了前体电离态、激光脉冲数（193nm 或 213nm UVPD）以及使用低压与高压阱的影响。
