Dynamics of guanosine self-assembled aggregates in the hexagonal columnar phase by quasielastic neutron scattering

Guanosine, one component of the nucleic acids, presents a simple model system to study the self-assembling process and the properties of columnar liquid-crystalline phases. In a recent x-ray study we investigated the structure of the aggregates at medium concentrations and explored the phase-diagram as a function of salt concentration in the solution. A microscopic model has been presented describing the size and distribution of the rod-shaped aggregates consisting of stacked guanosine tetramers. Here we present a first study of the dynamics of guanosine in the two-dimensional hexagonal phase. Inelastic neutron scattering gives further evidence for the ''persistent-flexible-hard-rod'' model; displacements in the hexagonal plane are found to be extremely high. To a detection limit of 0.04 meV we find no evidence for propagating phonon modes. The quasielastic signal measured is attributed to relaxational motions that is extremely overdamped motions of the guanosine rods.