Fig. 7

Partial 2D HSQC NMR spectra. Enzymatic lignins from the two MYB42 and the one MYB31 transgenic sugarcane bagasse, along with the GFP control in DMSO-d₆/pyridine-d₅ (4:1). The top row shows the aliphatic region, with color-coded assignments of the main lignin to the same-colored corresponding structures. The bottom row shows the aromatic and double-bond region showing the lignin polymer H, G, and S structural units along with ferulates (mainly from feruloylated arabinoxylan polysaccharides) and p-coumarates (on both lignin and polysaccharides); again, contour coloration matches that of the structures shown. The aromatic unit quantification values are from volume integration, on an S + G = 100 % basis; accuracy is generally good for the H:G:S units, but p-coumarate and ferulate end groups are severely overestimated, so their integrals should be used only for comparative purposes [17]