Roll out the barrel: By using singlemolecule force spectroscopy, a ß-barrelforming outer-membrane protein is unfolded for the first time. OmpC from E coli shows a surprising unfolding behavior: Singleβ, strands do not unfold individually but as β hairpins. These ß hairpins unfold one after another until the entire β-barrel membrane protein is unfolded (see structural representation).