Recent advances in endocrinology / by A.T. Cameron.

  • Alexander Thomas Cameron
Date:
1935
Catalogue details

Licence: In copyright

Credit: Recent advances in endocrinology / by A.T. Cameron. Source: Wellcome Collection.

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    0 to 1-7 per cent. Successive extractions of the same thyroid material yield preparations with diminishing iodine content, suggesting that the thyroglobulin present is a mixture of molecules containing different amounts of iodine (158). The amount present in the thyroid varies considerably. Wiener (1909) found that five dog’s thyroids contained amounts (based on dry weight) varying from 14 to over 60 per cent. (It is doubtful, however, if the higher figure is correct.) Diiodotyrosine was isolated by Drechsel in 1896 from the horny axial skeleton of a gorgonian coral. Its constitution was established by Wheeler as I H C—C / \ C—CH2—CH(NH2)—COOH. H—O—C I H It is a dextro-rotatory colourless crystalline compound, containing 58-7 per cent, of iodine. It is only very slightly soluble in cold water (1 part in 347 at 15° C.), but recrystal¬ lizes from hot water in needles resembling crystalline tyrosine. It is easily soluble in dilute ammonia, alkalies and acids. It gives a positive xanthoproteic, but a negative Millon’s test. Silver nitrate precipitates it, but does not split off iodine from it. Oswald (1910-11) could only isolate it from gorgonin of coral and spongin of sponges to the extent of 7 and 15 per cent, of the total iodine content of these materials respectively. When iodine is allowed to react with solutions of proteins, such as egg-white or casein, it combines with the protein molecule. Oswald showed that subsequent hydrolyses of such iodized proteins liberated amounts of diiodotyrosine of the same order as those obtained from gorgonin and
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