One summer’s day in 1928, Alexan-der Fleming, a physician in the

served that a mould had contaminated an agar plate seeded with Staphylococcus and had apparently dissolved the bac-teria in its vicinity.1 He succeeded in extracting some of the active principle in the mould, gave it the name “peni-cillin ” after its source, Penicillium, and published a series of papers on its an-tibiotic action on a variety of bacterial cultures. He failed in attempts to pu-rify the extract to a quality, or in a quantity, sufficient for animal experi-mentation, much less clinical testing, and finally abandoned this work. Ernst Chain, a biochemist in Howard Flo-rey’s laboratory in Oxford, learned about penicillin from the literature 10 years later, directed all his efforts to-ward its isolation and obtained a greatly purified form in early 1940,2 af-ter only about a year’s work. Chain’s success can be attributed to his experi-ence with the purification of enzymes, the most ephemeral of substances. Fleming, Chain and Florey shared the 1945 Nobel Prize for physiology and medicine