Of Weizmann's fifteen siblings, ten made aliyah. Two also became chemists; Anna (Anushka) Weizmann worked in his Daniel Sieff Research Institute lab, registering several patents in her name. His brother, Moshe Weizmann, was the head of the Chemistry Faculty at the Hebrew University of Jerusalem. Two siblings remained in the Soviet Union following the Russian Revolution: a brother, Shmuel, and a sister, Maria (Masha). Shmuel Weizmann was a dedicated Communist and member of the anti-Zionist Bund movement. During the Stalinist "Great Purge", he was arrested for alleged espionage and Zionist activity, and executed in 1939. His fate became known to his wife and children only in 1955. Maria Weizmann was a doctor who was arrested as part of Stalin's fabricated "Doctors' plot" in 1952 and was sentenced to five years' imprisonment in Siberia. She was released following Stalin's death in 1953, and was permitted to emigrate to Israel along with her husband in 1956. During World War I, another sister, Minna Weizmann, was the lover of a German spy (and later Nazi diplomat), Kurt Prüfer, and worked as a spy for Germany in Cairo, Egypt (then a wartime British protectorate) in 1915. Minna was outed as a spy during a trip to Italy, and deported back to Egypt to be sent to a British POW camp. Back in Cairo, she successfully persuaded the consul of the Russian Czar to provide her safe passage out, and en route to Russia, she managed to reconnect with Prüfer via a German consulate. Minna was never formally charged with espionage, survived the war, and would eventually return to Palestine to work for the medical service of the Zionist women's organization, Hadassah.