Multiphoton Absorption of Myoglobin–Nitric Oxide Complex: Relaxation by D-NEMD of a Stationary State

ABSTRACT:The photodissociation and geminate recombination of nitric oxide inmyoglobin, under continuous illumination, is modeled computationally. Therelaxation of the photon energy into the protein matrix is also considered in asingle simulation scheme that mimics a complete experimental setup. The dynamicapproach to non-equilibrium molecular dynamics is used, starting from a steadystate, to compute its relaxation to equilibrium. Simulations are conducted for thenative form of sperm whale myoglobin and for two other mutants, V68W and L29F,illustrating a fair diversity of spatial and temporal geminate recombination processes.Energy flow to the heme and immediate protein environment provide hints toallostery. In particular, a pathway of energy flow between the heme and the FG loopis illustrated. Although the simulations were conducted for myoglobin only, the thermal fluctuations of the FG corner are inagreement with the large structural shifts of FG during the allosteric transition of tetrameric hemoglobin.