Isolation of “Renaturable” Transfer Ribonucleic Acids

A new type of fractionating step involving gel filtration is introduced for the purification of certain transfer ribonucleic acids (tRNAs). It is based on the increase that occurs in the molecular dimensions of these tRNAs when they are trapped, reversibly, in a denatured state under conditions where the other tRNA components of the mixture are in the native conformation. This step, coupled to countercurrent distribution, is used to obtain in a near homogeneous state a leucine-specific tRNA that cannot be so purified by countercurrent distribution alone, as several other tRNA species have very similar partition coefficients in the two-phase solvent system employed. The applicability of the same techniques for the partial purification of a methionine-, an arginine-, and a glutamine-specific tRNA from yeast is also demonstrated. The potential of this combination of methods for large scale fractionation of tRNA is discussed.