A polarized and depolarized dynamic light scattering study of the tRNA^phe conformation in solution

Authors:

• Adam Patkowski,
• W. Eimer,
• Th. Dorfmüller

Abstract

The dynamics of tRNA^phe from brewer's yeast in solution was studied over a broad concentration and temperature range by polarized and depolarized dynamic light scattering. It is shown that measurements of the depolarized Rayleigh spectrum with a high‐resolution confocal Fabry‐Perot interferometer provide very accurate values for the rotational diffusion coefficient of the biopolymer. The translational diffusion coefficient was determined by polarized photon correlation spectroscopy. A combination of both transport coefficients allows one to calculate the hydrodynamic size of tRNA^phe using the Perrin equations for an biaxial ellipsoid. Within a temperature range from 9 to 45°C, the tRNA^phe molecule adopts a nearly spherical shape. The dimensions are similar to the previously proposed U‐shaped structure. In the melting region a second relaxation process was observed that is attributed to the collective reorientation of the bases. The concentration dependence of the rotational diffusion coefficient of tRNA^phe in the concentration range of 2–75 mg/mL exhibits a slightly positive slope, in agreement with previous experimental findings and in contradiction to the theoretical predictions based on hydrodynamic interactions in solution. Copyright © 1990 John Wiley & Sons, Inc.