Abstract: news & views-to break disulfide bonds, thus reverting to a system that is significantly easier to comprehend from a chemical point of view, but, as it turns out, poses a new question.In the same fashion as before, the polyprotein is expanded in basic solution (Fig. 1).Analysis of the response to different forces reveals two different regimes of reactivity.Up to forces of about 500 pN the rate of disulfide cleavage grows quickly.At higher tensile forces, however, a significantly slower growth of the reaction rate is observed.The authors correctly emphasize the difficulty in directly deriving an explanation from experiment only.Nevertheless, as a very plausible mechanism they propose a planarization of the reactive disulfide under higher tensile load.The carbon-sulfursulfur-carbon dihedral angle, which initially is about 90 degrees, changes to 180 degrees, bringing these four atoms into a plane.This leads to an elongation of the chain and causes the sulfur atoms to be more exposed to the basic solution.The resulting anne PIcHon