D.E. Shaw & Co., a New York brokerage firm and hedge fund, will fire 25% of its staff, or 264 people, and sell some businesses as it closes a trading alliance with BankAmerica Corp. The firm, run by former Columbia University computer science professor David Shaw, said it is winding down its alliance, run through D.E. Shaw Securities Trading, after the unit lost $200 million in the first nine months of the year, almost entirely on fixed-income securities. As part of the restructuring, D.E. Shaw is selling a unit to Trimark Securities Inc. that trades exchange-listed stocks over the counter. Neither Trimark nor D.E. Shaw would comment on the sale price. In addition, D.E. Shaw is seeking a buyer for its online brokerage business, FarSight Financial Services.