Regiochemistry controlled interfacial recognition of arabinoxylans on cellulose

Arabinoxylan (AX)-cellulose interactions are central to plant cell wall architecture and biomass recalcitrance. Here, six AX variants differing in the extent and placement of arabinose (Ara) substitutions at O2, O3, and both O2/O3 are examined using molecular dynamics simulations. AX-native (5 Ara groups) reveals a marked surface-dependent variation in its interactions, displaying greater interfacial association with the (110) hydrophilic cellulose than with the (100) hydrophobic cellulose surface. Similarly, AXO3-all, characterized by O3 Ara substitution reveals comparatively reduced association with hydrophilic cellulose, while AXO2 with O2 and O2/O3 substituted Ara exhibit enhanced association with the hydrophobic cellulose through increased interfacial contacts and hydrogen bonding. Notably, all AX variants predominantly retain a 3-fold conformation upon association with cellulose, irrespective of their substitution pattern. Interaction energy analysis further reveals distinct surface-dependent energetic contributions: Coulombic interactions dominate the AX interaction on hydrophilic cellulose, whereas both electrostatic and dispersive interactions contribute substantially at the hydrophobic interface. These findings demonstrate that Ara substitution pattern and regiochemistry, together with cellulose surface chemistry modulate backbone accessibility, contact continuity, and interfacial organization of AX on cellulose, thereby shifting the mechanistic paradigm from substitution-dependent conformational organization in acetylated xylans to interface-driven networking in arabinoxylans.