The angle between helix A and B of NcTnC (A/B angle) has previously been identified as a suitable metric for evaluating the effect of Ca 2+ activation upon Troponin . In Figure we illustrate the disposition of the helices relative to each other, using the definition of the angle between them given by Kekenes-Huskey et al. . For all our systems the helix A/B angle is predominantly in the "open" conformation characteristic of Ca 2+ -liganded troponin with the switch peptide docked.