The 1,2-glucans produced by bacteria are important in invasion, survival and
The 1,2-glucans produced by bacteria are important in invasion, survival and immunomodulation in infected hosts be they mammals or plants. from fungal-type glucans (Brown and Gordon, 2001; Brown et al. 2003), established that (i) dectin-1 is a calcium-independent carbohydrate-binding protein and (ii) linear 1,3-linked glucose sequences with degrees of polymerization (DP) 10 or longer are required for buy Presapogenin CP4 detection of binding. Using the designer approach, in conjunction with a novel high-sensitivity mass spectrometric (MS) sequencing method, we recently generated a glucome microarray of sequence-defined oligosaccharide probes derived from glucan polysaccharides of fungal, bacterial and herb origins in order to use as a high-throughput screening tool for characterizing glucan recognition systems of mammals and bacteria (Palma et al. 2015). The probes in the microarray encompassed linear sequences with a single linkage type: 1,2-, 1,3-, 1,4- or 1,6- with or configurations; and mixed multiple linkage types: 1,3-, 1,4 or 1,6-; also branched oligosaccharide sequences with 1,3 and 1,6-linkages with different DPs. Binding of the dendritic cell-specific C-type lectin receptor (CLR) DC-SIGN was noted to NGL probes from 1,2-linked gluco-oligosaccharides DP 2C13, derived from the cyclic 1,2-glucan (CG) of the bacterial pathogen invasion and survival (Arellano-Reynoso et al. 2005) and a potent activator of mouse and human dendritic cells (Martirosyan et al. 2012). This raised the possibility that DC-SIGN interacts with CG was analyzed by MALDI-MS, and the spectrum indicated complete removal of the succinyl side chains and preservation of the cyclic glucan chains which consisted of DP 16C23, with DP 17 (MNa+ at 2777) being the most abundant component (Physique?1). Fig.?1. MALDI mass spectrum of CG extracted from after removal of the succinyl side chains by moderate alkaline treatment. In the exploratory small-scale experiments, hydrolysis of the CG with 0.01 M HCl at 100C was assessed by monitoring the products at different reaction occasions by gel filtration (Physique?2). For monitoring of the reaction, the reagent HCl was not removed prior to analysis, and therefore an artefactual peak related to HCl occurred at 30 min. This has not interfered with the evaluation of the progress of the hydrolysis. The reaction time of 120 min (Physique?2D) was selected for large-scale experiments to obtain oligosaccharides with DPs ranging from 2 to 13 (Physique?3A). The fractions obtained by gel filtration were analyzed by HPTLC (Physique?3B). The identities of the major components in the higher oligosaccharide fractions with DPs 5 were determined by MALDI-MS and of the lower oligosaccharide fractions with DPs 4 by negative-ion ESI-MS. buy Presapogenin CP4 As shown in the MALDI spectra of fractions DP 7, 10 and 13 (Physique?4ACC, respectively) as representative, each fraction contains adjacent overlapping components in addition to the main component. For example, in fraction DP 7 (Physique?4A), oligosaccharides with DP 6 and 8 were present as minor components in addition to the main component DP 7 at 1175.2 (MNa+), due to incomplete separation by gel filtration chromatography. Fig.?2. Analysis of hydrolysis products of CG at different reaction time by gel filtration chromatography. (A) 0 min, (B) 30 min, (C) 60 min, (D) 120 min, (E) 180 min and (F) 210 min. Acid hydrolysis was carried out with 0.01 M HCl at 100C in … Fig.?3. Preparation of CG oligosaccharide fragments. (A) Bio-Gel P4 profile of CG hydrolysate and (B) HPTLC analysis of aliquots from each collected fractions. Fig.?4. MALDI mass spectra of selected CG oligosaccharides and their NGLs. (A) Heptasaccharide, (B) decasaccharide, (C) tridecasaccharide, (D) NGL of heptasaccharide, (E) NGL of decasaccharide and (F) NGL of tridecasaccharide. Linkage and anomeric configuration for the DP 7 fraction were investigated by negative-ion ESI-CID-MS/MS and 1H NMR. In the product-ion spectrum (Physique?5A), the neutral losses of 18 Da (e.g. 1133 and 971) and 120 Da (e.g. 1031 and 869) derived from dehydration and 0,2A-cleavage (Domon and Costello 1988), Rabbit Polyclonal to ALPK1 respectively, of the [M ? H]? and glycosidic C-type ions (Domon and Costello 1988) are characteristic of 1 1,2-linkage of gluco-oligosaccharides (Palma et al. 2015). The -anomeric configuration could be readily assigned by 1H NMR from the major anomeric doublet at 4.88 ppm with a coupling constant of 8.3 Hz; both – and -anomeric signals from the reducing end monosaccharide could also be identified (Determine?5B). Fig.?5. Sequence analysis of CG heptasaccharide by negative-ion ESI-CID-MS/MS (A) and 1H NMR buy Presapogenin CP4 (B). The heptasaccharide structure is shown to indicate fragmentation (A). The major doublet at 4.88 ppm with a coupling constant of 8.3 Hz was used to assign … Preparation of 1 1,2-gluco-oligosaccharide NGLs Preparation of the NGLs of glucan oligosaccharides with DP > 7 using the conventional method of reductive-amination (Chai et al. 2003) has been difficult and the yield extremely low (not shown). For the higher oligomers of gluco-oligosaccharides even with the relatively more efficient reaction in oxime-ligation (Liu et al. 2007).