Figure : For a given backbone angle cooperativity is maximal for a torsion force constant of 1.333-2.000, as indicated by the smallest sigmoid width and heat capacity fullwidth half-maximum parameters (right). Cooperativity metrics are relatively unaffected by the angle force constant over the range studied. Heat capacity and native contacts curves (left) are shown for an angle force constant of 100/rad 2 . For k t = 0.667 and below, the helix is not sufficiently stable to be able to produce a native contacts curve. For k t = 1.333 and above, the melting point (stability) increases with both angle and torsion stiffness (middle). All uncertainties are estimated using standard deviations from bootstrapping.