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Table 3 Assignments of 13C-1H correlation signals in the HSQC spectrum of lignin samples [26, 27]

From: Effect of alkaline lignin modification on cellulase–lignin interactions and enzymatic saccharification yield

Signals δC/δH Assignments
MeO 55.4/3.72 C-H in methoxyls
A γ 59.5–59.7/3.40–3.63 Cγ-Hγ in β-O-4′ substructures (A)
A α 71.6/4.88 Cα-Hα in β-O-4′ substructures linked to a S unit (A)
Aβ(G), Aβ(S) 82.8–85.7/4.13–4.46 Cβ-Hβ in β-O-4′ substructures linked to a G unit (A) Cβ-Hβ in β-O-4′ substructures linked to a S unit (A)
S2, 6 103.8/6.69 C2,6-H2,6 in etherified syringyl units (S)
S′2, 6 106.4/7.31 C2, 6-H2, 6 in oxidized (Cα= O) phenolic syringyl units (S′)
G5 115.1/6.72 C5-H5 in guaiacyl units (G)
G2 111.0/7.02 C2-H2 in guaiacyl units (G)
G6 119.0/6.77 C6-H6 in guaiacyl units (G)
FA2 110.8/7.35 C2-H2 in FA
FA6 123.1/7.16 C6-H6 in FA
FA7 144.4/7.42 C7-H7 in FA
H2, 6 pCA 127.5/7.23 129.8/7.52 143.9/7.51 C2, 6-H2, 6 in H units (H) C2, 6-H2, 6, p-coumaroylated substructures (pCA) Cα-Hα, p-coumaroylated substructures (pCA)
  115.0/6.24 Cβ-Hβ, p-coumaroylated substructures (pCA)
  1. G: guaiacyl unit; S: syringyl unit; H: p-hydroxyphenyl unit; pCA: p-coumaric acid; FA: ferulic acid