NEUTRON-SCATTERING EXPERIMENTS ON MAGNETICALLY ALIGNED LIQUID-CRYSTALLINE DNA FRAGMENT SOLUTIONS

Small angle neutron scattering experiments have been performed on liquid crystalline 163 basepair NaDNA fragments in aqueous solution in the concentration range 190-285 mg ml-1. To induce a macroscopic alignment, a magnetic field was applied either parallel (B(parallel-to) configuration) or perpendicular (B(perpendicular-to) configuration) to the incoming neutron beam. The isotropic scattering pattern in the B(parallel-to) configuration and the anisotropic scattering in the B(perpendicular-to) configuration agree with the cholesteric structure of the liquid crystalline solutions. From the anisotropic scattering in the B(perpendicular-to) configuration, information on the orientation ordering can be derived. For this purpose, the experimental data are compared to the form function of a uniform rod including a gaussian orientation distribution. The standard deviation of this distribution is approximately 20-degrees for all concentrations investigated here.