Differentiation of disaccharide isomers via a combination of IR and UV photodissociation mass spectrometry

Abstract

Rationale The challenge of glycan identification due to their structural complexity and diversity has profited enormously from recent developments in mass spectrometry (MS)‐related methods. For photodissociation MS, infrared (IR) and ultraviolet (UV) lasers can generate complementary fragment ions, so an effective combination of the two methods may provide rich and valuable fragmentation patterns for glycan analysis. Methods A 7.0 T Fourier transform ion cyclotron resonance (FTICR) mass spectrometer equipped with a double‐beam laser system was applied for the experiments. 3,5‐Diiodo‐L‐tyrosine was selected as the assistant molecule to form complex ions with ten isomeric disaccharides through electrospray ionization. The complex ions were further isolated and irradiated by IR and UV lasers separately or continuously in the FTICR cell. Results By combining the two complementary fragment spectra generated from the IR and UV lasers, a clear identification of all the ten isomers was achieved using their binary codes based on their fragmentation patterns. The double‐beam method simplifies the experiment by introducing the two lasers sequentially in one experiment, providing richer fragmentation patterns and making the full discrimination easier. Conclusions This study demonstrates the capabilities of the combination of IR and UV photodissociation MS in the identification of diverse glycan isomers. The double‐beam photodissociation method described here distinguished compositional, configurational and connectivity disaccharide isomers successfully. Compared with the data accumulation method based on separate IR and UV experiments, this method is simpler, faster, more flexible and also characterized by richer fragmentation patterns.

An identification method to distinguish monomeric sugar isomers on glycopeptides

“…In general, these methods rely on the differential stability of each isoform in a particular reaction. [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] For example, all 24 isomers of aldohexoses and ketohexoses have been distinguished using the fixed ligand kinetic method. 28,29,[44][45][46] The fixed ligand kinetic method involves the formation of a divalent metal-bound trimeric ion complex via ESI and subsequent fragmentation through collision induced dissociation.…”

Influence of Metal Coordination on the Gas-Phase Chemistry of the Positional Isomers of Fluorobenzoate Complexes

“…Isomer discrimination is of significant importance and well-acknowledged to be a challenging problem. Direct mass spectrometry (MS)-based methods, albeit with the merits of sensitivity and efficiency, are generally not suitable for this purpose because of the identical mass of the isomers, but it is possible to overcome such obstacles with the aid of liquid and gas chromatography, − ion mobility spectrometry, − and ultraviolet as well as infrared spectroscopy. − Additionally, tandem MS has evolved as another crucial means for isomer discrimination on the basis of the diagnostic ratio of fragment ions. − …”