It is a pleasure to acknowledge Professor S.G. Sligar and Dr. Yi Lu at University of Illinois at Urbana-Champaign, for their kind gift of Mb gene. NAMD and VMD were developed by the Theoretical Biophysics Group in the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign. This work was supported by the National Natural Science Foundation of China, NSFC (No. 21101091 ), Hunan Provincial Natural Science Foundation (No. 11JJ4017 ), Hunan Provincial Education Foundation (No. 11B105 ), and the initial foundation for oversea scholar return to University of South China (No. 2011XQD16 ).