PURIFICATION OF THE BRAIN HORMONE OF THE SILKWORM BOMBYX MORI

1. The brain hormone extracted from brains of Bombyx mori was purified by use of heating, ammonium sulfate precipitation, Sephadex gel-filtration, and DEAE-cellulose chromatography. On the basis of protein measurement, about 8000-fold purification was achieved. The most purified preparation was active by 0.002 µg. protein when injected into brainless pupae of Samia cynthia ricini. 2. The brain hormone manifested highly heterogeneous molecular forms which were revealed by Sephadex gel-filtration and by DEAE-cellulose chromatography. The molecular weights of the major components were estimated by Sephadex gelfiltration as ranging from 9000 to 31,000.