The W. M. Keck Foundation today will announce a gift of $150 million to boost scientific research at USC's medical school and at two affiliated hospitals, adding to the university's recent success in attracting supersized donations. The gift is the single largest in the 57-year history of the Keck Foundation, which has backed many scientific projects, including the famous Keck Observatory and telescopes in Hawaii. For USC, the money marks the third mega-gift since March, for a total of $460 million, as new President C. L. Max Nikias seeks to build the Los Angeles university's endowment. The Keck money will be paid out over 20 years with the goal of raising the academic reputation of USC's medical school now that the university has full authority over USC University Hospital, a 411-bed general care facility, and the 60-bed USC Norris Cancer Hospital, said James Ukropina, a Los Angeles attorney who is a vice president of the Keck Foundation.