Solid evidence: Induction of the polymerization of αβ-tubulin dimers into microtubules by epothilones, such as patupilone, by an as yet unknown mechanism leads to the apoptosis of cancer cells. Solid-state NMR spectroscopy of patupilone bound to microtubules has now enabled the identification of atomic positions of the drug that undergo clear chemical-shift changes upon binding (see correlation spectra of free (black) and complexed patupilone (red)).