Final MD frames of atomistic simulations of membrane-bound conformation B1 with fixed protonated state for all histidines. (A) Low pH T-domain structure with acidic residues set in their standard protonation state. (B) Low pH T-domain structure with acidic residues set in their neutralized state. Helices TH1, TH2, TH4, TH5, TH8, and TH9 are shown in green, cyan, magenta, orange, blue, and brown ribbon representation, respectively. Other helices are shown in gray ribbons. Phosphorus atoms are shown in dark brown space filled representation. Water molecules are not shown.