Scientists have been striving to develop antibiotics against drug-resistant bacterial strains. Most attempts have been plagued by a lack of molecular tools for manipulating — and ultimately improving — the structure of naturally occurring antibiotics. Harvard Medical School researchers Heather Losey, Christopher T. Walsh, and their colleagues reported in the Dec. 16, 2002 issue of the journal Chemistry & Biology that they harnessed two enzymes, which work by adding sugars to a central molecular core, and used them to create new versions of two potent antibiotics, vancomycin and teicoplanin. It is not clear if the new versions are effective against drug-resistant bacterial strains. “These drugs are not going to go on the market any time soon, but that was not our goal,” said Losey, Harvard Medical School graduate student in biological chemistry and molecular pharmacology. “This is just the first step out of many to find out if we can tweak the molecules.” What surprised Losey and Walsh, the Hamilton Kuhn professor of biological chemistry and molecular pharmacology, and their colleagues was how much tweaking they could do with the enzymes. “This just gives us more tools, more permutations to try,” said Losey.