Table 4.

Selected conformational parameters of cellulose III_II compared with those of the other cellulose allomorphs. The conformation of the hydroxymethyl group is defined by two letters, the first referring to the torsion angle χ (O5-C5-C6-O6) and the second to the torsion angle χ′ (C4-C5-C6-O6). Thus the ideal tg and gt conformations would be respectively be defined as sets of two angles (180°, 60°) and (60°, 180°). The glycosidic bond angle, τ is defined by (C1-O4-C4). The glycosidic torsion angle Φ and Ψ, which describe the relative orientation of adjacent glucosyl residues in the same chain are defined by (O5-C1-O1-C4) and (C1-O1-C4-C3), respectively. For cellulose I_α “up” and “down” refer to the relative heights of crystallographically independent and adjacent glucosyl residues in the unit cell.

	Φ	Ψ	τ	χ	χ′	θ
Cellulose IIIII down	−87	85	118	84	−157	5.4
Cellulose IIIII up	−91	91	117	69	−172	3.4
Cellulose IIII	−92	93	116	44	163	10.5
Cellulose II origin	−97	95	116	72	−165	5.0
Cellulose II center	−94	87	115	58	−175	10.2
Cellulose Iα up	−99	95	116	166	−74	6.9
Cellulose Iα down	−98	99	116	167	−75	9.4
Cellulose Iβ origin	−98	90	115	170	−70	10.2
Cellulose Iβ center	−89	94	116	158	−83	6.7