. Adventures in radioisotope research;. Radioactive tracers; Radiobiology. NITROGEN ATOMS IN THE SUNFLOWER 907 T.\BLE 1 Leaves. Nitrofjen content in in{,'m Young Intermediary Old trichloroacetic acid was added, the solution obtained containing 5 per cent of this substance. By this process, the proteins were precipitated. They were filtered off and washed with 5 per cent trichloroacetic acid. We will denote this precipitate as fraction I. The trichloroacetic filtrate was evaporated, supplying fraction II. The residue of the extracted leaves is deno
. Adventures in radioisotope research;. Radioactive tracers; Radiobiology. NITROGEN ATOMS IN THE SUNFLOWER 907 T.\BLE 1 Leaves. Nitrofjen content in in{,'m Young Intermediary Old trichloroacetic acid was added, the solution obtained containing 5 per cent of this substance. By this process, the proteins were precipitated. They were filtered off and washed with 5 per cent trichloroacetic acid. We will denote this precipitate as fraction I. The trichloroacetic filtrate was evaporated, supplying fraction II. The residue of the extracted leaves is denoted as fraction III. All three fractions were kjeldahlized, supplying three ammonia fractions which were neutralized with hydrochloric acid. The total nitrogen content of these samples was determined as ammonium by titration. To obtain the ^^N content of the samples from the ammonia distillates obtained, nitrogen was prepared by the method described by Rittenberg, Keston, Rosebuhy and Schoenheimer. The ^'N content of these samples was determined with the mass-spectrograph. Table 2 Percentiige of old nitro- Leaves •'N content atom per cent gen atom replaced by- new ones, assuming the absence of growth during the experiment New Protein nitrogen Intermediary 76 Old Non-protein nitrogen^ soluble New Intermediary 79 in NaCl solution Old New — Non-extractable nitrogen Intermediary Old 74 ' Containing presumably also nitrogen split off from proteins during drying of tlie Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hevesy, Georg von, 1885-1966. New York, Pergamon Press
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