Fig. 4: Selected regions of NMR spectra and molecular models of alternative glucosyl-containing trisaccharide repeating units (RU) of SCCs.
From: Structure and mechanism of biosynthesis of Streptococcus mutans cell wall polysaccharide
A 1H,31P-HMBC NMR spectrum of the WT SCC identifying phosphodiester-linked entities. B Spectral region from a 1H,13C-HSQC-TOCSY NMR experiment (mixing time of 200 ms) showing the seven-proton glucosyl spin-system of the α-d-Glcp6P(S)Gro-(1 → 2)-linked side-chain residue in the WT SCC. C Spectral region from a 1H,1H-NOESY NMR experiment at 700 MHz (mixing time of 250 ms) depicting cross-peaks from anomeric protons in the trisaccharide repeating unit (RU) of WT SCC to H2 at ~4.18 ppm of the branched rhamnosyl residue (major) and the corresponding ones at ~4.16 ppm (minor) in which the RU contains an α-d-Glcp6P(S)Gro-(1 → 2)-linked side-chain residue. D Canonical structure of the major RU of WT SCC, where the dashed lines denote partial substitution by side-chain entities. E 1H,13C-HSQC-TOCSY NMR spectrum (τmix 200 ms) showing the spin-system of the β-d-Glcp-(1 → 4)-linked side-chain residue in the ∆sccN SCC. F Spectral region from a 1H,1H-NOESY NMR experiment at 700 MHz (τmix 200 ms) with cross-peaks from anomeric proton of the β-d-Glcp-(1 → 4)-linked side-chain residue in the ∆sccN SCC. The cross-peak at 4.20 ppm originates from H2 of the 2-linked rhamnosyl residue in the backbone of the SCC (cf. the 3D model in Fig. S5). G Canonical structure of the RU containing the β-d-Glcp-(1 → 4)-linked side-chain residue, detected in the ∆sccN SCC. H Spectral region from a 1H,13C-HSQC-TOCSY NMR experiment (τmix 200 ms) showing the seven-proton glucosyl spin-system of the α-d-Glcp-(1 → 4)-linked side-chain residue in the ∆sccM SCC. I Canonical structure of the RU containing the α-d-Glcp-(1 → 4)-linked side-chain residue, detected in the ∆sccM SCC. Sugar residues are depicted in SNFG-format with Rha as a green triangle and Glc as a blue circle.
