Relaxation Analysis of Ligand Binding to the Myoglobin Reconstituted with Cobaltic Heme

Neya, Saburo; Suzuki, Masaaki; Hoshino, Tyuji; Kawaguchi, Akira T.

doi:10.1021/ic400078w

Cited by 6 publications

(22 citation statements)

References 35 publications

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“…It is notable in Table that the imidazole affinity to Co(III) Mb is moderately high, and that the association constant k on of imidazole is much smaller than that of Fe(III) Mb . The same holds for the k on and k off of the ligand in N 3 − , CN − , SCN − , and pyridine . The small k on constant observed for imidazole (Table ) may be explained by the distinct electronic charge of Co(III) ion with six 3d‐electrons, which is one electron larger than the Fe(III) ion with five 3d‐electrons.…”

Section: Discussionmentioning

confidence: 69%

“…A exhibited a Soret band with ε 414 = 124 1/(mM cm) as well as the sharp α and β bands at 552 (ε = 9.5 1/(mM cm)) and 525 (ε = 11.4 1/(mM cm)) nm, respectively. Increase in pH caused a spectral transition with well‐defined isosbestic points to reflect the dissociation of Co(III)‐bound H 2 O to OH ‐ at pH = 8.56 . The latter observation suggests that the Co(III)‐bound H 2 O is hydrogen‐bonded with the distal histidine .…”

Section: Resultsmentioning

confidence: 96%

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Usefulness of Myoglobin Containing Cobalt Heme Cofactor in Designing a Myoglobin-Based Artificial Oxygen Carrier

2014

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The structure and reactivity of cobalt-replaced myoglobin (Mb) were investigated to explore its possible application as an artificial oxygen carrier. Ligand binding analysis with relaxation kinetics revealed that various ligands bind to Co(III) Mb, contrary to the earlier thoughts. The equilibration process, however, was so slow that it proceeded over 90 min. These characteristic profiles of oxidized Co(III) Mb were ascribed to the electronic structure of Co(III) ion which is one electron larger than Fe(III) ion. The oxygen affinity of reduced Co(II) Mb was much smaller than that of Fe(II) Mb indicating that Co(II) Mb has excellent oxygen transport ability. The latter observation, together with the lack of carbon monoxide binding in Co(II) Mb, suggests utility of Co(II) Mb as Mb-based oxygen carriers. The present results on cobalt-substituted Mb are useful in designing myoglobin-based oxygen carriers.

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Section: Discussionmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 96%

Usefulness of Myoglobin Containing Cobalt Heme Cofactor in Designing a Myoglobin-Based Artificial Oxygen Carrier

2014

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“…In general, it is difficult to determine the affinity of cyanide for aqua-Co(III) complexes, because the ligand-exchange process is too slow to detect by conventional titrimetric measurements at 25 °C, pH 7.0 [41]. Thus, the binding constant of cyanide was determined by a relaxation analysis (Fig.…”

Section: Relaxation Analysis Of Cyanide Bindingmentioning

confidence: 99%

“…Thus, the binding constant of cyanide was determined by a relaxation analysis (Fig. 5) [41]. Into a solution of rHRP(Co III (OH)(TDHC)) (10 μM) in 50 mM sodium phosphate buffer at pH 7.0 was added a solution of 0.10 M KCN in the same buffer to control the final concentrations of KCN (0.10, 0.30, 0.6, 0.9 and 1.2 mM) and then UV-Vis spectra were recorded at 25 °C for 30 min.…”

Section: Relaxation Analysis Of Cyanide Bindingmentioning

confidence: 99%

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Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

et al. 2017

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Horseradish peroxidase was reconstituted with cobalt tetradehydrocorrin, rHRP(Co(TDHC)), as a structural analog of cobalamin coordinated with an imidazolate-like His residue, which is generally seen in native enzymes. In contrast to the previously reported cobalt tetradehydrocorrin-reconstituted myoglobin, rMb(Co(TDHC)), the HRP matrix was expected to provide strong axial ligation by His170 which has imidazolate character. rHRP(Co(TDHC)) was characterized by EPR and its reaction with reductants indicates a negative shift of its redox potential compared to rMb(Co(TDHC)). Furthermore, aqua- and CN-forms of Co(III) state were prepared. The former species was obtained by oxidation of rHRP(Co(TDHC)) with K[Fe(CN)]. The cyanide-coordinated Co(III) species in the latter was prepared by ligand exchange of rHRP(Co(OH)(TDHC)) with exogenous cyanide upon addition of KCN. The C NMR chemical shift of cyanide in rHRP(Co(CN)(TDHC)) was determined to be 121.8 ppm. IR measurements show that the cyanide of rHRP(Co(CN)(TDHC)) has a stretching frequency peak at 2144 cm. The C NMR and IR measurements indicate strong coordination of cyanide to Co(TDHC) relative to rMb(Co(CN)(TDHC)). Thus, the extent of π-back donation from the cobalt ion to the cyanide ion is relatively high in rHRP(Co(CN)(TDHC)). The pK values of rHRP(Co(OH)(TDHC)) and rHRP(Co(CN)(TDHC)) are the same (pK = 3.2) as determined by a pH titration experiment, indicating that cyanide ligation does not affect Co-His ligation, whereas cyanide ligation weakens the Co-His ligation in rMb(Co(CN)(TDHC)). Taken together, these results indicate that HRP reconstituted with cobalt tetradehydrocorrin is a suitable cobalamin-dependent enzyme model with imidazolate-like His residue.

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Efficient Electrocatalytic H₂ Production by Immobilized Co(III)‐myoglobin

Meglioli,

Di Rocco,

Ranieri

et al. 2024

ChemElectroChem

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The thermodynamics and kinetics of heterogeneous electron transfer (ET) for Co‐substituted horse myoglobin (Co−Mb) and its derivatives with ammonia and imidazole as heme axial ligands were studied with cyclic voltammetry on a pyrolytic graphite electrode along with their ability to mediate the electro‐catalytic production of H2. All the proteins experience a non‐diffusive electrochemical regime as electrode‐bound species. The adsorbed Co−Mb construct carries out the electro‐catalytic reduction of water protons to H2 with a good efficiency under anaerobic conditions thus yielding a simple and tunable system for H2 production. Replacement of H2O as Co axial ligand by ammonia and imidazole significantly lowers the catalytic currents for H3O+/H2O reduction to H2. The E°’ values of the Co(III)/Co(II) redox couple for all species are mainly determined by the enthalpic contribution. Differences were found in the kinetics of ET for the different protein adducts due to changes in the activation enthalpies. However, all species share the same distance of about 14 Å from the electrode surface to the Co(III)/Co(II) center determined using the Marcus model, consistent with a non‐denaturing adsorption of the protein.

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Relaxation Analysis of Ligand Binding to the Myoglobin Reconstituted with Cobaltic Heme

Cited by 6 publications

References 35 publications

Usefulness of Myoglobin Containing Cobalt Heme Cofactor in Designing a Myoglobin-Based Artificial Oxygen Carrier

Usefulness of Myoglobin Containing Cobalt Heme Cofactor in Designing a Myoglobin-Based Artificial Oxygen Carrier

Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

Efficient Electrocatalytic H₂ Production by Immobilized Co(III)‐myoglobin

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Relaxation Analysis of Ligand Binding to the Myoglobin Reconstituted with Cobaltic Heme

Cited by 6 publications

References 35 publications

Usefulness of Myoglobin Containing Cobalt Heme Cofactor in Designing a Myoglobin-Based Artificial Oxygen Carrier

Usefulness of Myoglobin Containing Cobalt Heme Cofactor in Designing a Myoglobin-Based Artificial Oxygen Carrier

Cobalt tetradehydrocorrins coordinated by imidazolate-like histidine in the heme pocket of horseradish peroxidase

Efficient Electrocatalytic H2 Production by Immobilized Co(III)‐myoglobin

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Efficient Electrocatalytic H₂ Production by Immobilized Co(III)‐myoglobin