Figure 8.

Exposure of C1 and C4 atoms in cellulose chains. (A) Stick and (B) space-filling representations of three cellohexaose molecules of a Cellulose Iβ crystal as presented in Figure 3. Hydrogen atoms are not shown for clarity. C1 and C4 atoms have been colored in blue and yellow, respectively. Due to the opposite orientation of glucose molecules in the cellobiose repeating unit, every other C1–C4 atom pair is exposed to the surface in cellulose chains that are at the top or bottom of the cellulose fibril. Type 1 LPMOs specifically attack C1 atoms (blue), type 2 enzymes specifically attack C4 atoms (yellow), and type 3 enzymes attack both C1 and C4 atoms.¹¹⁰