부산대학교 도서관

Summary The α and β forms of the pregnancy-associated protein, SP1 which have been previously identified in late pregnancy serum were found to be also present in the placenta. The α form was somewhat more difficult to extract, requiring the use of detergents in the extracting buffer. The two variants can be separated by ion exchange chromatography or by gel filtration and distinguished by the different shapes of the precipitation rockets on immunoelectrophoresis. The α variant appears to be the larger molecule on gel filtration. When solutions of SP1 are acidified to pH 2.5 the β form is rapidly converted to the α form and the latter is slowly destroyed. It is suggested that SP1α represents the combination of SP1β with some other protein present in the placenta and in the serum.