Differentiation of aldohexoses and ketohexoses through collision‐induced dissociation

Abstract

Mass spectrometry has high sensitivity and is widely used for carbohydrate structural determination. However, conventional mass spectrometry is not able to identify anomericity and stereoisomer. In this work, we demonstrate that aldohexose and ketohexose can be distinguished through the collision‐induced dissociation of sodium adducts in an ion trap mass spectrometer. The criterion for the differentiation is the intensity ratio of fragment ion m/z 143 to fragment ion m/z 113. Aldohexoses have an intensity ratio larger than 1.8 and ketohexoses have an intensity ratio less than 0.7. These ratios can be explained using a cross‐ring dissociation mechanism. Although the dissociation mechanism of lithium adducts is similar to that of sodium adducts, differentiation using lithium adducts is not as good as that of sodium adducts because of the large lithiation energies. In addition, a dehydration propensity rule to differentiate anomeric configuration is extended from glucose, galactose, and mannose to allose, altrose, gulose, talose, fructose, and tagatose in this work. Application of this method for the identification of aldohexoses and ketohexoses produced from the collision‐induced dissociation of oligosaccharides in tandem mass spectrometer is demonstrated.

Collision-induced dissociation of Na+-tagged ketohexoses: experimental and computational studies on fructose

“…The results in Fig. 3(c and f) show that βFru p favors the dehydration channel more than αFru p , consistent with the cis / trans argument used in earlier works on hexoses in pyranose form: 32–34 βFru p has its anomeric hydroxyl group (O2) in cis position to the neighboring hydroxyl group at O3, and thus a stronger preference for the dehydration channel is expected than for αFru p which has O2 and O3 in trans position to each other. However, this cis / trans argument does not hold anymore when considering the furanose forms of fructose (Fig.…”

“…Consistent with ref. 32, the four spectra have been assigned by comparing the intensities of the peaks in the HPLC chromatogram with NMR results. [60][61][62][63] However, note that this assignment has been done under the assumption that the four isomers have the same ionization efficiency.…”

“…It has been shown that aldohexoses can be distinguished from ketohexoses by comparing the signal intensities associated with the cross-ring dissociation channels. 32 However, that study also revealed the difficulties when assigning the configuration of the ketohexoses. In this work, we reinvestigate fructose, the most prominent ketohexose, and its dissociation channels.…”

“…26 It has recently been demonstrated that the structural information of oligosaccharides, including stereoisomerism, anomeric configuration, and linkage positions, can be obtained by the so-called logically derived sequence (LODES) tandem mass spectrometry (MS n ) approach. [27][28][29][30][31][32] To correctly interpret the MS results, it is helpful to understand the mechanisms of the different monosaccharides. Along this direction, several mechanistic studies on selected Na +tagged (aldo-)hexoses [33][34][35] and their derivatives 36,37 have been carried out with an integrated approach combining experimental and theoretical analysis.…”

A self-adapting first-principles exploration on the dissociation mechanism in sodiated aldohexose pyranoses assisted with neural network potentials

“…Recently, an experimental investigation on all aldohexoses shown in Scheme 1 has been performed. 38 To have a better understanding of the LODES of aldohexoses, the dissociations of allose (All), altrose (Alt), gulose (Gul), idose (Ido), and talose (Tal) (shown as AH-1 in Scheme 1) should be explored. To explore the huge number of conformers and reduce the risk of missing low-energy TSs, a systematic and efficient TS exploration scheme is necessary.…”