RENEWED EVALUATION OF FIBRE DIFFRACTION DATA OF CELLULOSE II
L.M.J. Kroon-Batenburg, A.M.M. Schreurs and J. Kroon
Department of Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
Keywords: cellulose, fibre diffraction
Diffraction patterns of crystalline fibres are characterized by diffuse spots that occupy a large volume in reciprocal space. Recently a procedure (EVAL-14) was developed [1] that predicts reflection contours given a few simple physical parameters, like focus dimensions, crystal size, mosaic spread etc. This method has been extended and used to predict fibre diffraction spots and to integrate the intensities for regenerated cellulose II fibres and perform proper background subtraction. The data were obtained with a Nonius kCCD. Afterwards data reduction leads to |F|2's that can be used in structural refinement. The methods used will be discussed and illustrated.
Independent of the diffraction data, MD simulations of possible cellulose II models were carried out [2] with the GROMOS program. For ordered low- energy models the structures were refined against the newly obtained data by the SHELXL97 program [3]. The so-called anti-parallel packing of cellulose II with all hydroxymethyl groups in the gt conformation gave the lowest R-value.
These investigations are supported in part by the Netherlands Foundation of Chemical Research (SON) with financial aid from the Netherlands Technology Foundation (STW; grant no 349-4431)