The principal motion of troponin is a hinge-like motion between the two quasi-rigid domains of troponin, NcTnC and the ITC domain . The hinge angle is altered by Ca 2+ activation 32 and is also proposed to be modulated by phosphorylation The simulations indicate that upon phosphorylation the distribution of hinge angles in WT troponin shows an increase in the mean angle with a significant rigidification and decrease of the accessible range. This is consistent with the studies of Hwang et al, who proposed that phosphorylation modified the positioning of NcTnC relative to the ITC domain, based on NMR measurements. It is notable that the C terminus of troponin T (CcTnT), previously not included in molecular dynamics simulations, 20 is located within the interdomain interface where its interactions with NcTnI and cTnC appear to be phosphorylation-dependent, thus possibly accounting for the known role of this peptide in cTn regulation Using the A/B helix angle as our metric for the opening and closing of the hydrophobic patch, we found that, indeed, phosphorylation has a significant effect on the distribution of interhelix angles with an increase from 82% to 99% distribution below 110° which was proposed as the threshold of the 'open' state. In common with the hinge angle, there is a significant rigidification and decrease of the accessible range upon phosphorylation.