CRYSTAL-STRUCTURE OF VALONIA CELLULOSE I-BETA

The crystal structure of Valonia cellulose I beta is determined by X-r ay fiber diffraction analysis. A careful reanalysis of two existing X- ray diffraction data sets for Valonia cellulose I leads to a consisten t, definitive structure of the beta-phase. The results resolve ambigui ties in existing X-ray analyses between ''parallel up'' and ''parallel down'' packing of the cellulose sheets in native Valonia cellulose. T he molecular and sheet structures are essentially identical to those p reviously determined, but these results define precisely the packing o f the sheets. The sheet packing is discussed in terms of the energy an d density of the crystal structure. The structure of the beta-phase ha s specific implications for the packing of the alpha-phase of Valonia cellulose I.