Figure 4.

Comparison of the ¹³C chemical shifts of plant primary wall cellulose with crystalline cellulose of algae and animals. (a) ¹³C chemical shift RMSD values between the Arabidopsis primary wall interior cellulose a-e and literature Cladophora and tunicate cellulose, which represent the Iα and Iβ allomorphs, respectively. Each allomorph shows two types of chemical shifts. For ease of inspection, the twenty (5×4) discrete RMSD values are connected by contour lines, thus positions between the twenty points do not have physical meaning. (b) Differences of individual ¹³C chemical shifts between primary wall celluloses and crystalline Iα and Iβ celluloses. Two similarly good assignments are each found for cellulose a, b and c, but neither assignment is satisfactory, as shown by chemical shift differences of more than 1.5 ppm for some of the carbons. For cellulose e, good agreement with Iα-A’ is found. Cellulose d has large chemical shift differences from all known allomorphs, indicating that the cellulose d structure does not exist in the algal and animal celluloses.