A variety of long term studies on animals have simultaneously beerj in progress to determine the potentialities of irradiated cells with respect to glahdular function, to nuclear structure, to changes in capacity for cell division, to neopfasm formation, and to the life of the cell that is crippled by radiation. These obs ations have led to information useful in recent national population studies on Tjexposure. The various studies supported by this contract are briefly described in the paragraphs = that follow: The Development and Use of Column Chromatography for the Separation of Amino Acids [odinated A method for measuring the formation and disappearance of iodinate in thyroids was desirable not only to study the normal steps in the syn thyroid hormone but to observe the effects of radiation on those steps and on thyroid function in general. synthesis When starch column chromatography of amino acids was first describe Stein and Moore in 1948, the principal investigator, while still in Boston, attempted to modify this technique so that it might be applied to the quantitative of iodinated amino acids. It was about the time that this method of sejaration, of chuematomraphic separation was tested ina large variety of experime the absolute identification of the iodinated amino acids, the completene separation of the compounds and the reproducibility of the separations. There iodine aLat lengthy period of study on the possibility of interchange of [the i took place. a erent deal of tine and offort was then devoted to toying of inhibiting this interchange without otherwise altering the nature of samples. © find means Sodium thiosulfate proved to be an effective inhibitor of iodifhe interchange. This was later supplanted by thiouracil, but in the process of exploring] these problems the entire solvent system was changed to an alkaline medium whifh when used with starch columns proved to be a more satisfactory but extremely laborjous method of separating iodinated compounds. By careful adjustment of the ratios ff the constituents of the solvent and the addition of a small amount of the ucing agent, it was possible to separate thyroxine, iodide, monoidotyrosine and diiodbtyrosine quite effectively and interchange of the label did not occur during fracfionation. See attached Figure 1. Collection of eluent in 2 ml volumes from starch}colums permitted the separation of the compounds by as much as 20 milliliters of solvent. The reproducibility of the separation on starch columns wes preven by reruming single labeled compourdis, previously recovered, with other unlabeled compounds fo determine under what circumstances complete recover failed or interchange of the Jsotopic iodine in compounds occurred. By using this method, two unknown compounds were repeatedly found ig thyroid tissue. Formore than 2 years efforts were made to identify the largest]and seemingly most important of the 2 unknowns which was repeatedly found on each frac#ionation of thyroid tissue. When Gross and Pitt-Rivers described 3, 5, 3-triiodofhyronine on paper chromatograms, our "Unknown #1" proved to be this compound.