St. Jude Children's Research Hospital is creating a $412 million research center, the largest project ever on the Memphis hospital's campus. The center, slated to break ground this spring and open in 2021, is a major component of the hospital's previously announced $1 billion campus expansion — itself a piece of a $7 billion spend to expand the hospital's efforts to cure childhood diseases. The 625,000-square-foot, eight-story center is designed to attract the best scientists and clinicians from…