ROTATIONAL AND TRANSLATIONAL DIFFUSION OF SHORT RODLIKE MOLECULES IN SOLUTION - OLIGONUCLEOTIDES

Rotational and translational diffusion coefficients in aqueous solution of series of three B duplex oligonucleotides 8, 12, and 20 base pairs in length are measured by depolarized and polarized dynamic light scattering, respectively. Theoretical relations for the diffusion coefficients of short rods by Tirado and Garcia de la Torre are used in combination with the experimental data to obtain the dimensions of the molecules. The theoretical relations are self-consistent through the series and give a hydrodynamic diameter for DNA of 20 +/- 1.5 angstrom. The results, furthermore, show that the combination of depolarized and polarized dynamic light scattering provides a powerful method for obtaining hydrodynamic dimensions of short rodlike particles and may therefore be used in applications which follow molecular sizes and size changes.