Human thyrotropin and its α and β subunits

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Abstract
A new procedure is described for the isolation of human thyrotropin using ion exchange chromatography and gel nitration only Thyroid stimulating activity of the final preparation of our human thyrotropin amounted to 0.5 IU/mg by bioassay The α and β subunit of the hormone were also obtained by a new procedure. In this method the native hormone was incubated in an acidified 8 m urea solution and the chains were then separated by ion exchange chromatography and gel filtration The amino-terminal residues of the α and β chains were valine and phenylalanine respectively The β chain appears shorter at its carboxy-terminal end by one methionine residue than its bovine counterpart Cross-contamination of the subunit preparations were measured by radioimmunoassay. The β chain exhibited a contamination of about 3 percent of the α subunit by weight. The α subunit is contaminated by about one percent of the β chain by weight