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Myoglobin rate constants

In Ref. [279] the technique of protein modification was used to study the dependence of the rate of photoinduced electron tunneling on the distance between TZnP and Ru(III) sites in modified myoglobins. The modified proteins were prepared by substitution of zinc mesoporphyrin IX diacid for the heme in four various pentaammineruthenium (III) derivatives of sperm whale myoglobin (NH3)5Ru(His-48)Mb, (NH3)5Ru(His-12)Mb, (NH3)5Ru(His-116)Mb and (NH3)5Ru(His-81)Mb. Metal-to-metal distance between ZnP and (NH3)5Ru(His) ranges in this seria from 16.1-18.8 A for His-48 to 27.8-30,5 for His-12. The rate constant of electron tunneling decreases in this series in accordance with Eq. (1) with ve = 7.8 x 10s s 1 and ae = 2.2 A at T = 298 K. [Pg.71]

Figure 2.8. The Gibbs energy optimized ET rate vs. edge-to-edge distance relationship for intraprotein electron transfer. The bacteria RC rate constants are shown as circles and excited heme-ruthenium ET in modified myoglobin and cytochrome c are shown as triangles (Moser and Dutton, 1992). Reproduced with permission. Figure 2.8. The Gibbs energy optimized ET rate vs. edge-to-edge distance relationship for intraprotein electron transfer. The bacteria RC rate constants are shown as circles and excited heme-ruthenium ET in modified myoglobin and cytochrome c are shown as triangles (Moser and Dutton, 1992). Reproduced with permission.
Figure 4.2. Temperature dependence of the rate constant of electron transfer (Icet) in myoglobin modified covalently by donor-acceptor groups (a) and the deviation of various dynamic quantities from normal harmonic behaviour obtained by molecular dynamic simulation, inelastic neutron scattering, MOssbauer spectroscopy and spectral broadening analysis (b). (Likhtenshtein et al., 2000). Reproduced with permission. Figure 4.2. Temperature dependence of the rate constant of electron transfer (Icet) in myoglobin modified covalently by donor-acceptor groups (a) and the deviation of various dynamic quantities from normal harmonic behaviour obtained by molecular dynamic simulation, inelastic neutron scattering, MOssbauer spectroscopy and spectral broadening analysis (b). (Likhtenshtein et al., 2000). Reproduced with permission.
In the synthetic iron porphyrin, O2 affinity mainly depends on the strengths of the <7-donation from the lone pair of O2 to the heme-iron dz orbital and 7r-back donation from the d/r orbital on the iron to the Jt orbital of 2. To evaluate the O2 affinity and/or O2 binding dynamics in myoglobin and hemoglobin, O2 - protein interaction is a further important factor. For example, the O2 dissociation rate constant for oxymyoglobin is relatively smaller than those of O2 complexes... [Pg.1874]

The stabilization of the photogenerated redox products in the eosin-functionalized, Co(ll)-protoporphyrin IX-reconstituted myoglobin, Eo -Mb-Co(I), (slow charge recombination proceeds with the rate constant k = 1.4 x 10 ) allowed the tai-... [Pg.2560]

In this context, the control of O2 affinity by the distal environment of the heme group in hemoproteins can be probed by comparison of wild-type compounds with mutants which do not contain distal histidine [105]. Replacement of distal histidine by glycine results in a 10-fold decrease in O2 affinity. Within the hemoproteins themselves, the lack of distal histidine in aplysia myoblobin compared to horse myoglobin increases the dissociation rate constant by a factor of six, whereas the association rate constants are identical for both systems. The data are again consistent with the stabilization of bound O2 via hydrogen-bonding in horse myoglobin. [Pg.178]


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