Like Hitchings, she started off by hunting for chemicals that could block bacterial growth by inhibiting DNA—but then added her own strategic twist. Instead of sifting through mounds229 of unknown chemicals at random, Elion focused on one class of compounds, called purines. Purines were ringlike molecules with a central core of six carbon atoms that were known to be involved in the building of DNA. She thought she would add various chemical side chains to each of the six carbon atoms, producing dozens of new variants of purine. Elion’s collection of new molecules was a strange merry-go-round
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