Rapid Identification of Common Hexapyranose Monosaccharide Units by a Simple TOCSY Matching Approach

Abstract

Solution NMR spectroscopy is a well established technique for non-destructive characterization of the structures and conformations of complex oligo- and polysaccharides. One of the key experiments involves the use of 2D TOCSY to collect the 1H spins into groups that can be associated with the individual saccharide units that are present in the molecule under study. It is well known that the magnetization transfer rate through the 1H spin system during the TOCSY spin lock period is sensitive to the intervening 3J(H,H) scalar couplings, and therefore also to the saccharide stereochemistry. Here, we have investigated the potential to extract information on the stereochemistry of hexapyranose monosaccharide units directly from TOCSY spectra. Through a systematic experimental investigation of the magnetization transfer initiated from the anomeric 1H resonance in D-glucose, D-galactose and D-mannose it is shown that a 100 ms spin lock time provides optimal spectroscopic discrimination between these three commonly occurring building blocks. A simple matching scheme is proposed as a new tool for rapid attribution of the TOCSY traces originating from the anomeric 1H resonances towards the underlying monosaccharide type. The scheme appears robust with regard to structural variations and fairly tolerant to incidental overlap. Its application provides useful guidance during the subsequent NMR assignment process, as demonstrated with the PS7F polysaccharide from Streptococcus pneumonia. In addition, we show that our scheme affords a clear-cut distinction between the alpha- and beta-epimers of D-mannose-type units, which can be difficult to discriminate by NMR analysis. Application to the N-glycan 100.2 demonstrates the potential and wide applicability of this new discrimination approach.

Unusual C,O-Fused Glycosylapigenins from Serjania marginata Leaves

“…Individual sugar units were identified by 1D-TOCSY and 1D-ROESY experiments involving selective excitation of each anomeric proton. 30 Selective 1D-TOCSY experiments on the signal at δ 5.12 showed a typical spin system of a β-glucopyranosyl moiety. The NOE associations observed in the 1D-ROESY experiment between the anomeric proton and H-3 and H-5 were consistent with the structure of this sugar.…”

From lab to market: An integrated bioprocess design approach for new‐to‐nature biosurfactants produced by Starmerella bombicola

“…APT, 13 C, COSY, and HSQC spectra were acquired through the standard sequences available in the Bruker pulse program library. Custom settings were used for HMBC (32 scans), TOCSY (100 ms MLEV spinlock, 0.1 s mixing time, 1.27 s relaxation delay, 16 scans), and H2BC (21.8 ms mixing time, 1.5 s relaxation delay, 16 scans), according to literature (Conrath, ; Gheysen, Mihai, Conrath, & Martins, ; Petersen et al, ).…”

Mandelalides A–D, Cytotoxic Macrolides from a New Lissoclinum Species of South African Tunicate

“…The following designation was applied to depict intensity of peaks; grey ovals indicate intensity or signal greater than 1.5% of intensity measured for the signal of the anomeric proton, white ovals indicate intensity of at least 0.5% but no more than 1.5% intensity measured for the anomeric 1 H signal. 16 …”