XXXX pituitary thyrotropin. Isolation and recombination of subunit isoforms.

@entity1 @entity535 @entity3787 @entity2975 @entity7287
The alpha and beta subunits of @entity1 pituitary thyrotropin were prepared by a process developed earlier. Each subunit preparation contained four isoforms which were isolated by preparative agarose-suspension electrophoresis. The alpha subunit isoforms were homogeneous upon examination by analytical electrophoresis in @entity2975 gel. Contrarily, the isolated beta subunit isoforms were always to some extent contaminated by the adjacent more acidic component. This was considered to show a transformation of these forms favoured by @entity3787 ions. @entity535 analysis revealed no differences between the alpha isoforms nor between the beta isoforms, and the @entity535 compositions were in very good agreement with those earlier obtained for multi-alpha and multi-beta preparations. Attempts to recombine different alpha and beta isoforms were made at pH 7.0. The activities of recombined @entity7287 (in terms of MRC Research Standard A) ranged from 1.1 unit/mg (recombination of two minor components) to 3.5 units/mg (recombination of two major components). The activities of native and recombined thyrotropins as well as the subunit activities were followed by radioimmunoassays. The activity of native thyrotropin as a function of time was studied under different storage conditions. The subunit activities were also measured. All conditions resulted in a decrease in the thytrotropin activity (about 40% in 10 weeks). This decrease was not due to dissociation as the subunit activities remained approximately constant.
