A piece of the mold that led to the discovery of penicillin drew an unexpected $25,300 at auction Friday in London. The buyer was the Science Museum. Alexander Fleming, who discovered the antibiotic properties of the mold in 1928, presented the sample to Douglas MacLeod, a gynecologist and colleague at St. Mary’s Hospital in London. MacLeod died in 1970, and the specimen was auctioned by his son. Fleming’s discovery came into widespread use following studies at Oxford in 1940. Fleming died in 1955.