Fig. 1: Structure of wood hemicelluloses and their incorporation in BC-H model networks.

a Schematic illustration of the polymeric network in a model BC-H system mimicking the secondary cell walls of softwoods and hardwoods prior to lignification. b Average molecular structure of major repeating motifs of wood hemicelluloses. Softwood O-acetyl-galactoglucomannan (acGGM, from spruce) comprises a main chain of β-(1→4)-linked d-mannose (Man) and d-glucose units (Glc) partially substituted by α-(1→6)-linked d-galactose units (Gal) exclusively on the Man units and partial acetylation at the C2 and C3 hydroxyl groups of Man⁶⁸. Hardwood O-acetyl-glucomannan (acGM) has similar structure as acGGM without Gal substitutions. Softwood arabino-4-O-methylglucuronoxylan (AGX, from spruce) consists of a backbone of β-(1→4)-linked d-Xyl with partial substitution by both α-(1→2)-linked mGlcA and α-(1→3)-linked l-arabinofuranose (Ara)^10,16. Hardwood O-acetyl-4-O-methylglucuronoxylan (acGX, from birch) consists of a backbone of β-(1→4)-linked d-xylose units (Xyl) with partial substitution of α-(1→2)-linked 4-O-d-methylglucuronic acids (mGlcA) and O-acetylation (OAc) at some of the C2 and C3 units of Xyl^13,22. c Oligomeric mass profiling (OLIMP) by mass spectrometry of the wood hemicelluloses (AGX, acGX, and acGGM) after enzymatic hydrolysis. Note: P refers to a pentose (Xyl or Ara), H refers to a hexose (Man, Gal or Glc), Ac refers to an acetyl group, and mU refers to mGlcA. Source data provided as a Source Data file.