Phosphorus compounds in the cell. 3. The incorporation of radioactive phosphorus into the ribonucleotide fraction of liver tissue

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Abstract
In expts. with P32 the use of the procedure of ionophoresis on paper makes it possible to obtain nucleotides free from all traces of contaminating inorganic phosphate. When the ribonucleotide fraction obtained by the procedure of Schmidt and Thannhauser (Jour. Biol. Chem. 161 83. 1945) from the tissues of an animal receiving p32 is submitted to ionophoresis, at least 6 non-nucleotide phosphate derivatives can be detected as well as the 4 ribonucleotides. Their presence can conveniently be demonstrated by making autoradiographs of the ionophoretic run. One of these 6 concomitants is inorganic phosphate derived from phosphoprotein. The other 5 are organic phosphates. Two hrs. after admn. of P32 to rats and rabbits the concomitants all have higher specific activities than the nucleotides. This accounts for the abnormally high specific activity of the Schmidt -Thannhauser fraction. A modified Schmidt-Thannhauser procedure involving partial isolation of the ribonucleic acid is descr. which, in combination with inophoresis, gives a true picture of the specific activities of the ribonucleotides. Ribonucleotides comprise only about 75% of the total P in the ribonucleotide fraction obtained from tissues by the Schmidt -Thannhauser procedure.