Figure 4.

Protein backbone structural change in response to the external forces coupled to the CO transitions between DP and Xe4. Backbone traces of the average structure of the unperturbed deoxy Mb and of displaced structures undergoing the protein conformational changes in response to the external force are depicted in tube representation colored in blue and orange, respectively. Arrows in red along with labels of the helices indicate directions of the large conformational changes. To see the protein response easily, the protein response is depicted to be three times as large as the one shown in Fig 3. The protein backbone structure changes coupled to the CO transitions between Xe4 and Xe2, and Xe2 and Xe1, are shown in Fig. S6.