Advances in Tandem Mass Spectrometry Approaches for the Structural Characterization of Sulfated Glycosaminoglycans

Glycosaminoglycans (GAGs) are complex linear carbohydrates that participate in a broad range of biological processes.1 Their structural analysis is challenging, and there has been considerable research into tandem MS approaches. Electron activation methods such as electron detachment dissociation (EDD) produce glycosidic fragments and an abundance of cross-ring fragmentation, but this approach is confined to FTICR mass spectrometers. EDD has been shown to accurately identify sulfate position of GAG oligosaccharides and can distinguish C-5 uronic acid stereochemistry in some cases.2 We have investigated other activation methods that can produce EDD-like fragmentation behavior. Negative electron transfer dissociation (NETD), charge transfer dissociation (CTD), and ultraviolet photodissociation (UVPD) have great potential for the analysis of sulfated GAGs.

NETD produces higher abundant fragmentations and slightly more cross-ring fragmentations at a faster timescale than EDD. NETD also has a higher efficiency for converting precursor into informative fragment ions.3, 4 CTD has the ability to determine structurally significant modifications in GAG samples. Current data shows the ability for CTD to produce EDD like fragmentation in an ion trap instrument. UVPD has been shown to produce a higher cross-ring abundance than EDD and more informative fragmentation than CID.5 Here, we investigate purified GAG standards specifically looking for the ability for UVPD to identify C-5 uronic acid stereochemistry. These techniques produce EDD-like fragmentation, are faster, use more easily produced precursor ions and can be implemented on a broader range of instruments.

1. Chi, L.; Amster, J.; Linhardt, R. J., Mass Spectrometry for the Analysis of Highly Charged Sulfated Carbohydrates. Current Analytical Chemistry 2005, 1 (3), 223-240.

2. Leach, F. E.; Arungundram, S.; Al-Mafraji, K.; Venot, A.; Boons, G.-J.; Amster, I. J., Electron detachment dissociation of synthetic heparan sulfate glycosaminoglycan tetrasaccharides varying in degree of sulfation and hexuronic acid stereochemistry. International Journal of Mass Spectrometry 2012, 330-332, 152-159.

3. Leach, F. E.; Riley, N. M.; Westphall, M. S.; Coon, J. J.; Amster, I. J., Negative Electron Transfer Dissociation Sequencing of Increasingly Sulfated Glycosaminoglycan Oligosaccharides on an Orbitrap Mass Spectrometer. Journal of The American Society for Mass Spectrometry 2017, 28 (9), 1844-1854.

4. Huang, Y.; Yu, X.; Mao, Y.; Costello, C. E.; Zaia, J.; Lin, C., De novo sequencing of heparan sulfate oligosaccharides by electron-activated dissociation. Anal Chem 2013, 85 (24), 11979-86.

5. Klein, D.; Leach, F. I.; Amster, I.; Brodbelt, J., Structural Characterization of Glycosaminoglycan Carbohydrates using Ultraviolet Photodissociation. Analytical chemistry 2019