Cellotetraose crystal data

Cellotetraose. Despite several years of steady effort, no single crystal adequate for conventional X-ray crystallography could be grown. Fig 8. shows a powder diffraction photograph the wide angle neutron diffractogram is in Fig. 9. Crystal data are in Table V. Fig. 10 shows both a lamellar fragment of cellotetraose... 

Characteristics of macromolecules are often preserved In oligomeric model compounds. As one example, X-ray powder diffraction patterns (1) and the infrared spectra (2) of the oellodextrins beginning with cellotetraose are very similar to those of cellulose II. Such a similarity implies a close relationship in their molecular structures. While these model compounds should permit more accurate characterization because of their macroscopic, single-crystal domains (3), oellodextrins form non-centrosymmetric crystals and analysis of their diffraction data is a serious challenge. 

The Linked-Atom Least-Squares (LALS) procedure (44) was used to generate molecular models of cellotetraose. The glucose residues were kept in the standard Cj conformation all bond angles cmd bond lengths were fixed at standard values (43). The constrained model of the crystal structure was optimized against both X-ray data and non-covalent interatomic interactions, as described by Smith and Arnott (44). 

More structural data for cellulose-type linkage geometries are available from crystals of proteins that are complexed with either cellulose fragments or molecules that contain a lactose moiety. Figure 15-10 shows a complex of cellotetraose and an endoglucanase (Sakon et al. 1996), as well as the structure of the fragment in more detail. That protein is an enzyme that catalyzes the hydrolysis of cellulose molecules, but it also has nonhydrolytic binding sites. Other proteins do... 

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