ESI-MS differential fragmentation of positional isomers of sulfated oligosaccharides derived from carrageenans and agarans

Abstract

We have prepared a number of isomeric red seaweed galactan-derivative sulfated oligosaccharides to determine whether there were diagnostic differences among the isomeric mass spectra obtained using ESI CID MS/MS (triple quadrupole instrument). Fragmentation of the single or multicharged molecular ions from di-, tetra-, and hexasaccharides indicated that the relative positioning of the sulfate groups and type of monosaccharide unit affect the rate of cleavage of the glycosidic bonds. We also performed a comparative [M-Na] Ϫ fragmentation study of positional isomers of sulfated disaccharides that present all four monosulfation possibilities on the galactopyranosidic ring. In this case, negative-ion ESI CID MS/MS approach gave diagnostic product ions from cross-ring cleavages along with the same main B 1 ion (from sulfated Galp), at m/z 241, for all isomers. The isomeric disaccharides were also submitted to increased spray energy conditions inducing in-source fragmentation; preformed B 1 ions were then fragmented to give similar product ions as those found in [M-Na] Ϫ analysis. [4,5]. It is now recognized that the regiochemistry and stereochemistry of the positions of the sulfates are highly significant for their recognition, the "sulfation code" [6,7]. Thus, the development of diverse tools for the structural determination of sulfated sugars has become extremely important. In this context, a high number of publications have been focused on the study of sulfated sugar-containing macromolecules through the mass spectrometric analysis of their enzymatically or chemically produced oligosaccharides [8 -12]. The earlier studies [13,14] [8,9], and mucopolysaccharides [24] have served as models for the improvement of the knowledge of mass spectrometric methods involving these types of molecules.Many of the aforementioned studies have been dedicated to determine the sulfation position of isomeric oligosaccharides. Evaluation of the losses of monosaccharide units by sequencing mass spectrometry is normally sufficient to determine the sulfation pattern of isomers bearing sulfate groups on different monosaccharide units [10,17]. In cases where the differences are only related to the position occupied by the sulfate groups in the same monosaccharide ring, the determination of the positional isomer is more difficult. Most of the studies carried out with this aim have been performed to determine the location and degree of sulfation for 4-and/or 6-sulfated HexNAc of chondroitin sulfate-oligosaccharides. For this purpose, control of the charge state of the parent ion followed by determination of the relative abundance of the product ions generated from the cleavage of the glycosidic linkage Address reprint requests to Dr. M. D. Noseda,

Production of agaro- and carra-oligosaccharides by partial acid hydrolysis of galactans

“…Galactan oligosaccharides can be obtained through partial acid (Yu et al, 2002;Gonçalves et al, 2010;Ciancia et al, 2005) or enzymatic hydrolysis (Guibet et al, 2006;Young et al, 1978;Rochas et al, 1994). Usually, the partial acid hydrolysis methods (Figure 1) promote the specifi c cleavage of 3,6-anhydro-α-galactosidic bonds to produce the reducing di-or tetrasaccharides 2 and 4, containing the unusual anhydro galactose in hydrated aldehyde form as the terminal unit.…”

Structure and anticancer activity in vitro of sulfated galactofucan from brown alga Alaria angusta

“…However, in case of the ion under study, B-type ion at m/z 225.0 together with A-type ion at m/z 345.04 suggested another variant: Fuc-2-SO 3 − -(1 → 4)-Gal. Some minor ions of A-type also suggested C6 and/or C4 sulfation of Gal residue: m/z 150.97, m/z 180.98, m/z 198.99 (Goncalves, Ducatti, Grindley, Duarte, & Noseda, 2010). These data were supported by methylation analysis (see above).…”

Rapid Mass Spectrometric Analysis of a Novel Fucoidan, Extracted from the Brown AlgaCoccophora langsdorfii

“…The elucidation of the structural features of sulfated oligosaccharides by a negative-ion tandem mass spectrometry was carried out using the following observations, estimated in the former studies of glycosaminoglycan- [30], sulfated galactan- [16, 31, 32], and sulfated fucan-derived fragments [33, 34]. It was shown that the product ion spectra of [M-Na] − (where M represents the sodium salt of oligosaccharides) featured an extensive series of B- and C-type (according to nomenclature, suggested by Domon and Costello [35]) glycosidic cleavages, whereas the Y-type cleavage occurred mainly at the sulfated residues [16, 30].…”

“…Hence, the availability of the proton at glycosidic hydroxyl is essential for the production of the abovementioned ions of A-type. Strong signal of (B 1 -type ion) at m/z 225.0 from the cleavage of sulfated at C-2 α -L-Fuc p residues [31] (with loss of water molecule) along with intensive Y 1 -type ion at m/z 225.0 together with signal from the loss of NaSO 4 − at m/z and small 0,2 X-type signal at m/z 138.9 (indicator of 4-linked and sulfated at C-2 Fuc p residue on the reducing end) suggested that sulfate occupied mostly position C-4 of the reducing 3-linked Fuc p residue. Unfortunately, the reduction with NaBD 4 is a destructive reaction and only major components of the mixture were successfully sequenced.…”