On the conformation of yeast transfer RNA

Abstract

The scattered X-ray intensities from dilute solutions of a mixture of yeast transfer RNA's in 0.1 m-KCl, 0.02 m-Tris-HCl (pH 7.42) buffer at 22.5 °C have been measured. The X-ray data cover a range of small angles where the scattering is a function mainly of the over-all size and shape of the molecule. Comparisons are made with scattering curves calculated for a number of conformations of the molecule which have been suggested. Many of the more open conformations are eliminated. The Holley cloverleaf model is examined in some detail. Agreement with experiment is not obtained unless the arms are folded rather tightly together, in groups of two pointing up and two down, or three up and one down. The former configuration gives slightly better agreement. Less extensive data were taken at 45 °C, at which temperature the molecule appears about 10% larger in linear dimensions than at 22.5 °C, but no major change in shape occurs.