A shekara ta 1929, Northrop ya ware kuma ya yi amfani da enzyme na ciki pepsin kuma ya ƙayyade cewa shi furotin ne.
Tabbas, mafi rikitarwa na jumla shine "A cikin 1929, ya ware kuma ya bayyana enzyme na ciki pepsin kuma ya ƙayyade cewa furotin ne kuma a cikin 1938 ya ware kuma ya bayyana farkon bacteriophage (ƙaramar ƙwayoyin cuta da ke kai hari ga ƙwayoyin cuta), kuma ya ƙayyade cewa nucleoprotein ne. "