Biophysical properties of RNA from turnip yellow mosaic virus

Physical studies were carried out on RNA isolated from turnip yellow mosaic virus by extraction with phenol in the presence of sodium dodecyl sulfate and bentonite. Its molecular weight from sedimentation and viscosity measurements is about 1·9 × 10⁶, corresponding to one RNA molecule per virus particle. The RNA, immediately after isolation, was relatively compact, and unfolded to a less compact but stable form upon heating or alcohol-precipitation and subsequent dialysis. The RNA molecules exhibited a smaller hydrodynamic volume upon lowering the temperature without any significant change in the extinction coefficient. Under acidic conditions, the RNA molecules become more compact and less susceptible to temperature-induced unfolding; this has been ascribed to the formation of poly C-like structures. Polyamines such as bis(3-aminopropyl)-amine and spermine effected a marked reduction in the hydrodynamic volume of the RNA and increased its resistance to temperature-induced unfolding. Denaturation treatments were carried out on the RNA to detect hidden breaks and the possible presence of subunits. It was concluded that the RNA does not have subunits, although occasionally discrete degradation components were obtained.