[Polychromatic kinetics of conformational and spin relaxation of reduced intermediates of myoglobin].
Moessbauer spectroscopy was used to study the relaxation of a non-equilibrium myoglobin state produced at 77 K by reduction of metmyoglobin Fe(III) with thermalized electrons. The intermediate is characterized with the metMb (r) conformation of the protein globule and a low spin heme Fe(II) with a water molecule on the sixth coordination site. The intermediate is stable at 77 K but relaxes with increasing temperature into equilibrium deoxymyoglobin with dissociation of the bond Fe(II)-H2O and the transition of the Iron into the high spin state. In the temperature range 147-195 K the relaxation kinetics is nonexponential in time and can be described in terms of the polychromatic kinetics. A fitting of the kinetics data supposing a gamma-distribution of activation enthalpies of the relaxation shows a shift and a narrowing of the distribution at T > 180 K. The effect of structural rearrangements and equilibrium conformational fluctuations in the protein on the shape of the observed barrier distribution is discussed.
Prusakov
V E
VE
Physics Department, Munich Technical University, Germany.
Parak
F
F
Chekunaev
N I
NI
Gol'danski'
I
I
D000818:Animals; D006801:Humans; D007700:Kinetics; D009211:Myoglobin / Q000737:chemistry*; D010084:Oxidation-Reduction; D011487:Protein Conformation; D013113:Spin Labels
D009211:Myoglobin; D013113:Spin Labels