"Please see that my brain is given to the NFL's brain bank." So read the suicide note left by former Chicago Bears safety Dave Duerson, a four-time Pro Bowler and an integral part of the 1985 Bears championship team. Duerson, 50, shot himself in the chest on Feb. 17 after texting several family members with the request that his brain be given to science. Duerson, who retired from the NFL in 1993, had suspected he was suffering from chronic traumatic encephalopathy, a degenerative brain disease associated with years of repeated blows to the head playing football. Scientists at a Boston University brain center will make the final diagnosis in coming months.