ANALYSIS OF DISORDER IN BIOPOLYMER FIBERS

X-ray diffraction patterns from oriented polycrystalline fibers of som e biopolymers show that the molecules are disordered within the microc rystallites. Quantifying the disorder in such specimens is a necessary step for the use of their diffraction patterns for accurate structure determination. Theory and algorithms for calculating diffraction patt erns from such fibers have recently been described [Stroud & Millane ( 1995). Acta Cryst. A51, 000-000]. Here the application of these method s to determining the kind and degree of disorder in two polynucleotide fibers is described. The more ordered system shows random screw disor der accompanied by small lattice distortions, and the more disordered system shows larger lattice distortions and significant rotational dis order. These results show the potential of these methods for determini ng disorder in polycrystalline fibers; uniqueness of the solutions and implications for structure determination are discussed.