|French, Alfred - Al|
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/27/2009
Publication Date: 4/23/2009
Citation: 2009. DIFFRACTION FROM MODEL CRYSTALS. National Cotton Council Beltwide Cotton Conference. p.1407-1409. Interpretive Summary: Although the characterization as a crystalline material is a surprise to many non-specialists, cotton fibers have a number of traits in common with other crystalline materials. One of these traits is the ability to cause diffraction of a beam of X-rays. Compared to patterns from a crystal of table sugar, the cotton diffraction patterns contain much less information, but there are still a number of issues that can be addressed based on this data. These issues concern the size and perfection of the crystalline materials. Those parameters are primary factors in determining the performance of the fiber in physical tests, in relationships to moisture, and in chemical reactions. Although calculation of the diffraction patterns based on normal crystals is a widely available capability, determinations of the changes based on the very small crystals of cotton and their computerized molecular models requires different software that has not been previously applied to cotton. The present work presents the results of calculating diffraction patterns from new software, some of which was written specifically for this work. It is chiefly of interest to scientists who are trying to understand the structure of cotton fiber for the purposes of genetic improvement or chemical modification.
Technical Abstract: Although calculating X-ray diffraction patterns from atomic coordinates of a crystal structure is a widely available capability, calculation from non-periodic arrays of atoms has not been widely applied to cellulose. Non-periodic arrays result from modeling studies that, even though started with atomic coordinates in periodic arrays, degenerate into coordinates that do not retain exact crystallinity. Being able to calculate the diffraction pattern enables comparison with the observed patterns from practical samples such as cotton fibers to attempt to understand the true nature of the cellulose in that environment.