Liselotte I. Hecht

The measurement of amino acid specificity of transfer ribonucleic acid

Abstract 1. 1. Although it is generally accepted that a particular s-RNA molecule is specific for a particular amino acid, it is not known how effectively “wrong” amino acids are excluded from “right” s-RNAs. It is difficult to measure the relative rates of aminoacylation of s-RNA using conventional methods. 2. 2. The competition method of Ingold and Shaw has been applied to the determination of the relative rates of aminoacylation of mammalian s-RNA by leucine, isoleucine, valine and alloisoleucine. 3. 3. Alloisoleucine may substitute for isoleucine once in 20 times; for valine once in 300 times. 4. 4. The natural amino acids substitute for each other less than once in 10 000 times.