Preparation of radioactive biochemicals by use of yeast

Abstract

AbstractSugar molasses of high specific activity is prepared by photosynthesizing C14O2 into sugar in a leaf of the Canna plant and then extracting the sugar. When T. utilis is grown in such a medium about 45% of the radioactivity is incorporated into the yeast cell; the remaining radioactivity is carbon dioxide and volatile organic compounds. The cells are now randomly labeled in all carbon compounds. Distribution of C14 in the major cell components, such as protein, polysaccharide, and nucleic acids is shown.Nucleic acid is extracted from the cells and subject to chemical and enzyme action, for the preparation of randomly labeled ribonucleotides. Proteins are isolated and hydrolyzed to yield high specific activity amino acids, up to 150 mc. per millimole. Similarly polysaccharides are also isolated and from them high specific activity glucose and mannose are obtained by acid hydrolysis.By growing T. utilis in a medium containing C14‐8‐adenine and C14‐2‐uracil, these bases are about 90% incorporated into the nucleic acids of the cell. Using the same methods described for the uniformly labeled nucleic acid only base labeled nucleosides and nucleotides are prepared.Preparative procedures for the isolation of some of these compounds are discussed. The latest biochemical techniques for their purification are described. Methods for assaying for radiochemical purity and problems concerining stability of high specific activity compounds are discussed.