Structural order of Tobacco-Mosaic-Virus in aqueous solutions determined by static and dynamic light scattering

Abstract

Aqueous solutions of rodlike tobacco mosaic virus (TMV) (L = 300 nm, d = 18 nm) below and above the overlap concentration c* (c* = 1 particle/length³) are examined by means of dynamic light-scattering techniques (DLS) and compared to static light-scattering (SLS) results. There, samples of very low ionic strength show a liquid-like structure due to the electrostatic interaction of the charged rods, whereas at sufficiently high ionic strength the Coulomb interaction is screened and ordering disappears. The liquid-like structure at minimal ionic strength is examined in the concentration range 0.25 c* – 1.4 c*. A detailed comparison shows differences in the static structure factor S(q) determined by SLS and DLS, respectively. Moreover, the transition from a liquid-like to a gas-like order is shown as a function of the salt concentration, i.e., the ionic strength. For the calculation of S(q) from DLS-data, we have measured the apparent diffusion coefficient of TMV solutions where the Coulomb interaction is screened by added NaCl or Tris-HCl.