Thyroxine Crystallization

Properties Optically active, the /-isomer is the natural and physiologically active form, ((//-thyroxine) Needles. Decomposes at 231-233C. Insoluble in water, alcohol, and the common organic solvents soluble in alcohol in the presence of mineral acids or alkalies, (/-thyroxine) Crystals. Decomposes at 235-236C. ((/-thyroxine) Crystals. Decomposes at 237C. 

Figure 28-22 The experimental x-ray crystal structure of prealbumin with bound i-thyroxine. Prealbumin is a letramer with four identical subunits, A, B, C, and D, The four identical subunits form a channel with two bound i-thyroxine molecules. The binding sites have a C2 axis of symmetry.

SIO). TBPA has been crystallized (P8). The binding properties of TBPA for thyroxine are specific, but different from those of TBG. TBPA does not bind Ta (13) but binds the propionic and acetic acid analogs of thyroxine much more strongly than it does thyroxine (Rll). TBPA also binds vitamin A (A9). 

Crystals, dec 236-237. [a] s +21.5 (c — 4.75 in a mixture of ] part N HO + 2 parts ethanol). Possesses 5 times the activity of L-thyrOxine (goiter prevention test in rats). Insol in water, ale, propylene glycol. Sol in dil alkalies with the formation of a brownish. Water-soluble, sodium salt. 

DL -Thyroxine, needle -like crystals. Dec 231-233. Insol in water, in alcohol, and in the other usual organic solvents, but in the presence of mineral acids or alkalies it dissolves in alcohol sol in solns of the alkali hydroxides and in hot solns of the alkali carbonates. When alkali hydroxide solns of thyroxine are satd with sodium chloride, the sodium salt of thyroxine separates. 

Cody V, Hazel J, Langs DA, et al. Molecular structure of thyroxine analogues. Crystal structure of 3,5,3 -triiodothyroacetic and 3,5,3, 5 -tetraoiodothyroacetic acid N-diethanolamine (1 1) complexes. J Med Chem 1977 20 1628-1631. 

The major active principle in thyroid tissue was crystallized by Kendall in 1915, but it was not until 1926 that the chemical structure of thyroxine was determined by Harington. Since then, many studies have been conducted in an attempt to correlate changes in physiological activity of compounds related to thyroxine with changes in their chemical structure. 

In 1914, Kendall, a scientist at the Mayo Clinic in Minnesota, crystallized thyroxin, one of the thyroid hormones. The chemical structure of thyroxin wtis described in 1927 by Harrington and Barger, British university scientists. Harrington synthesized thyroxin, thereby paving the way for a more effective therapeutic agent than thyroid extracts which were variable in biological potency. 

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