Tumor cells divide fast. They thus require a high supply of components for their DNA, like purines. The biosynthesis of purines could now be a new point of attack for chemotherapy. However, without a natural model, the search for an inhibitor for a cellular process is like the proverbial search for a needle in a haystack. An American research team has developed a clever way to quickly conjure the desired "needle" out of the hay, presenting several candidates to act as starting points for the design of a purine synthesis inhibitor.