1090. The effect of co-ordination on ionization. Part IV. Imidazole and its ferrimyoglobin complex

George, Pascal; Hanania, G. I. H.; Irvine, D. H.; Abu-Issa, I.

doi:10.1039/jr9640005689

Cited by 60 publications

(40 citation statements)

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“…We have found similar results with horse metMb [6]. The imidazolate anion does not contribute to the observed rate of binding in metMb but bound imidazole ionizes to the imidazolate form with an apparent pK a of 10.34 [18]. …”

Section: Introductionsupporting

confidence: 64%

“…Interestingly, the reported K D values for the imidazole complexes of these two classes span about the same range of affinities. The low end of the affinity range is exemplified by sperm whale metmyoglobin and horse cytochrome c with K D values of 26 and 34 mM for their imidazole complexes, respectively [18,39], and the high end exemplified by Chironomus plumosus metHb and Rhodobacter sphaeroides cytochrome c 1 , with K D values of 29 and 33 μM for their imidazole complexes, respectively [40,41]. The binding affinity for each class spans about three orders of magnitude.…”

Section: Discussionmentioning

confidence: 99%

“…The estimated pK a values are of 7.4 ± 0.2 and 8.2 ± 0.5 for the yCcP and rCcP imidazole complexes, respectively. These pK a values are about 7 and 6 units lower than that of free imidazole, Scheme 1, and about 3 and 2 units lower than the equivalent pK a values for metMb and metHb [18, 50]. The most acidic of all heme-bound imidazoles is that of soybean legHb, with a reported pK a of between 6.5 and 7.0 [51].…”

Section: Discussionmentioning

confidence: 99%

“…The most extensive studies of imidazole binding to heme proteins have been carried out using metMb [6,7,9-18]. The binding of imidazole is pH dependent with maximum affinity near pH 8.…”

Section: Introductionmentioning

confidence: 99%

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Binding of imidazole, 1-methylimidazole and 4-nitroimidazole to yeast cytochrome c peroxidase (CcP) and the distal histidine mutant, CcP(H52L)

Erman

Chinchilla

Studer

et al. 2015

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics

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Imidazole, 1-methylimidazole and 4-nitroimidazole bind to yeast cytochrome c peroxidase (yCcP) with apparent equilibrium dissociation constants (KDnormalapp) of 3.3 ± 0.4, 0.85 ± 0.11, and ~0.2 M, respectively, at pH 7. This is the weakest imidazole binding to a heme protein reported to date and it is about 120 times weaker than imidazole binding to metmyoglobin. Spectroscopic changes associated with imidazole and 1-methylimidazole binding to yCcP suggest partial ionization of bound imidazole to imidazolate. The pKa for ionization of bound imidazole is estimated to be 7.4 ± 0.2, about 7 units lower than that of free imidazole and about 3 units lower than imidazole bound to metmyoglobin. Equilibrium binding of imidazole to CcP(H52L) is biphasic with low- and high-affinity phases having KDnormalapp values of 9.5 ± 4.5 and 0.13 ± 0.04 M, respectively. CcP(H52L) binding of 1-methylimidazole is monophasic with an affinity similar to those of yCcP and rCcP. Binding of 1-methylimidazole to rCcP is associated with two kinetic phases, the initial binding complete within 10 s, followed by a process that is consistent with 1-methylimidazole binding to a cavity created by movement of Trp-191 from the interior of the protein to the surface. Both the equilibrium binding and kinetics of 1-methylimidazole binding to yCcP are pH dependent. yCcP has a four-fold increase in 1-methylimidazole binding affinity on decreasing the pH from 7.5 to 4.0, an observation that is unique among the many studies on binding of imidazole and imidazole derivatives to heme proteins.

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Section: Introductionsupporting

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…The most extensive studies of imidazole binding to heme proteins have been carried out using metMb [6,7,9-18]. The binding of imidazole is pH dependent with maximum affinity near pH 8.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Binding of imidazole, 1-methylimidazole and 4-nitroimidazole to yeast cytochrome c peroxidase (CcP) and the distal histidine mutant, CcP(H52L)

Erman

Chinchilla

Studer

et al. 2015

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics

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“…The calculated energies show that Complex 3 is more stable than Complex 2, because of the internal hydrogen-bonding stabilization. The outstanding stabilization of Complex 4 in gas-phase is thought to be a result of a resonance effect in the deprotonated imidazole ring structures [26]. The resonance effect of the deprotonated imidazole ring is indirectly indicated by the similar five bond lengths of the Complex 4 imidazole ring, as listed in Table 3.…”

Section: Resultsmentioning

confidence: 99%

A DFT study of the [Cu2+—(GlyGlyHis – 3H+)]−1 ion complex structure

Kim¹,

Kim²

2008

Journal of Molecular Structure: THEOCHEM

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Geometric and Electronic Structures of Phenoxyl Radicals Hydrogen Bonded to Neutral and Cationic Partners

Orio

Jarjayes

Philouze

et al. 2012

Chemistry A European J

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Two di-tert-butylphenols incorporating an N-methylbenzimidazole moiety in the ortho or para position have been synthesised ((Me)OH and (pMe)OH, respectively). Their X-ray structures evidence a hydrogen bond between the phenolic proton and the iminic nitrogen atom, whose nature is intra- and intermolecular, respectively. The present studies demonstrate that (Me)OH is readily oxidised by an intramolecular PET mechanism to form the hydrogen-bonded phenoxyl-N-methylbenzimidazolium system ((Me)OH)(.+) , whereas oxidation of (pMe)OH occurs by intermolecular PET, affording the neutral phenoxyl benzimidazole ((pMe)O)(.) system. The deprotonations of (Me)OH and (pMe)OH yield the corresponding phenolate species ((Me)O)(-) and ((pMe)O)(-), respectively, whilst that of the previously reported (H)OH (analogous to (Me)OH but lacking the N-methyl group) produces an unprecedented hydrogen-bonded phenol benzimidazolate species, as evidenced by its X-ray structure. The latter is believed to be in equilibrium in solution with its tautomeric phenolate form, as suggested by NMR, electrochemistry and DFT studies. The one-electron oxidations of the anions occur by a simple ET process affording phenoxyl radical species, whose electronic structure has been studied by HF-EPR spectroscopy and DFT calculations. In particular, analysis of the g(1) tensor shows the order 2.0079>2.0072>2.0069>2.0067 for ((Me)O)(.), ((H)O)(.), ((Me)OH)(.+) and ((H)OH)(.+), respectively. ((Me)O)(.) exhibits the largest g(1) tensor (2.0079), consistent with the absence of intramolecular hydrogen bond. The g(1) tensor of ((H)O)(.) is intermediate between those of ((Me)OH)(.+) and ((Me)O)(.) (g(1)=2.0072), indicating that the phenoxyl oxygen is hydrogen-bonded with a neutral benzimidazole partner.

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1090. The effect of co-ordination on ionization. Part IV. Imidazole and its ferrimyoglobin complex

Abstract: Thermodynamic data have been obtained for the acid ionization in dilute aqueous solution of the imino =NH group in imidazole and in its complex with sperm-whale ferrimyoglobin. For the ionization in free imidazole at 25",

Cited by 60 publications

References 0 publications

Binding of imidazole, 1-methylimidazole and 4-nitroimidazole to yeast cytochrome c peroxidase (CcP) and the distal histidine mutant, CcP(H52L)

Binding of imidazole, 1-methylimidazole and 4-nitroimidazole to yeast cytochrome c peroxidase (CcP) and the distal histidine mutant, CcP(H52L)

A DFT study of the [Cu2+—(GlyGlyHis – 3H+)]−1 ion complex structure

Geometric and Electronic Structures of Phenoxyl Radicals Hydrogen Bonded to Neutral and Cationic Partners

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