A DYNAMIC LIGHT-SCATTERING STUDY OF 4 DNA RESTRICTION FRAGMENTS

Dynamic light scattering time correlation functions from dilute solutions of linear, monodisperse DNA restriction fragments, ranging in size from 367 to 2311 base pairs (molecular weight from 0.24 to 1.5 million), were measured at 20 °C, in 100 mM NaCl, 10 mM Tris.HCl, and 1 mM EDTA (pH 8). The correlation functions were analyzed by using CONTIN, a constrained inverse Laplace transform program. At scattering angles of 16 and 22°, the correlation functions are consistent with single exponential decays representing the translational motion of the DNAs. At higher angles, the correlation functions generally exhibit two or more relaxation modes reflecting the internal dynamics in addition to the translational diffusion of the DNAs. The distribution of relaxation times is consistent with theoretical simulations based on the Rouse-Zimm free draining model for a flexible coil with experimental input parameters for the radius of gyration and translational diffusion coefficient. The translational diffusion coefficients are predicted well by the Yamakawa and Fujii theory for the dynamics of wormlike chains. The diffusion coefficients vary with the molecular weights to the 0.68 power. The rotational or first internal decay time is consistent with the Rouse-Zimm model in the free draining limit. The persistence length from a comparison of experimental diffusion coefficients with the predicted diffusion coefficients based on the theories of Yamakawa and Fujii, Yamakawa and Yoshizaki, or Hagerman and Zimm does not show a clear dependence on the contour length of the DNAs. The general results are consistent with transient electric birefringence experiments performed previously on the same fragments. © 1990, American Chemical Society. All rights reserved.