ChemInform Abstract: MODELS FOR THE ACTIVE SITE OF OXYGEN‐BINDING HEMOPROTEINS. DIOXYGEN BINDING PROPERTIES AND THE STRUCTURES OF (2‐METHYLIMIDAZOLE)‐MESO‐TETRA(α,α,α,α‐O‐PIVALAMIDOPHEN# YL)PORPHYRINATOIRON(II)‐ETHANOL AND ITS DIOXYGEN ADDUCT

Jameson, G. B.; Molinaro, Frank S.; Ibers, James A.; Collman, James P.; Brauman, J. I.; Rose, Éric; Suslick, Kenneth S.

doi:10.1002/chin.198030086

Cited by 4 publications

(9 citation statements)

References 1 publication

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“…In contrast methylation at the 4‐position would not be expected to directly perturb the proximal hydrogen bond. Methylation at the 2‐position is expected to impede heme binding through steric clash with the porphyrin skeleton 11–15…”

Section: Resultsmentioning

confidence: 99%

“…One reason for high specificity for the 24dimeimd tautomer may be that binding of the 1H tautomer would place both methyl groups in ortho positions relative to the heme. Although placing a single Methyl group adjacent to the coordinating nitrogen does not appear to significantly destabilize low‐spin ferrous meimd•porphyrin complexes,11–15 it seems likely that placing a second methyl group in the other ortho position may destabilize the porphyrin‐imd complex. High‐resolution structures of 2meimd•Fe 2+ porphyrin complexes show that the 2meimd ligand tips to increase the separation between the porphyrin plane and the 2‐methyl group,15 perhaps relieving some of the 2‐methyl porphyrin strain.…”

Section: Discussionmentioning

confidence: 97%

“…The intensities of the two exchangeable peaks differ by about two‐ to three‐fold, but since it is not clear which tautomeric form gives rise to which peak, the tautomer that is in excess cannot be assigned. Although methyl groups that are positioned ortho with respect to the coordinating nitrogen are destabilizing in low‐spin iron porphyrin complexes, little to no destabilization is produced in high‐spin ferrous deoxy complexes 11–15. In the following paper, the energetic consequences of 2‐methylation are estimated in a variety of contexts; the most relevant may be that which results from comparing 4meimd and 24dimeimd binding to H93G deoxyMb, since proximal hydrogen bonding is expected for both these ligands in both tautomeric forms.…”

Section: Discussionmentioning

confidence: 99%

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Trans-substitution of the proximal hydrogen bond in myoglobin: I. Structural consequences of hydrogen bond deletion

Barrick

Dahlquist

2000

Proteins

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The structural role of a side-chain to side-chain protein hydrogen bond is examined using trans-substitution of the proximal histidine of myoglobin with methylimidazoles (Barrick, Biochemistry 1994;33:6546-6554). Modification of the chemical structure of exogenous ligands allows this hydrogen bond to be disrupted. Comparison of the crystal structures of H93G myoglobin complexed 4-methylimidazole (4meimd; methylation at carbon 4) and 1-methylimidazole (1meimd; methylation at the adjacent nitrogen, preventing hydrogen bonding between the imidazole ligand and the protein) shows that the polypeptide, heme, and methylimidazole orientations are the same within error. For 4meimd there appear to be major and minor conformations corresponding to different tautomeric states of the ligand. Conformational heterogeneity is also seen in the hyperfine-shifted region of the NMR spectrum of 4meimd complexed with high-spin H93G deoxyMb. The major conformation of the 4meimd ligand and the 1meimd ligand, as seen in the respective crystal structures, are quite similar except that the proximal ligand NH-to-Ser92-OH hydrogen bond is eliminated in the 1meimd complex, and instead the proximal ligand CH is adjacent to the Ser92-OH. Thus, this system provides a means to eliminate the Mb proximal hydrogen bond in a chemically and structurally conservative way.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

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Trans-substitution of the proximal hydrogen bond in myoglobin: I. Structural consequences of hydrogen bond deletion

Barrick

Dahlquist

2000

Proteins

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“…Since this work, numerous 5C iron(II)-porphyrinate complexes have been generated and isolated following different methodologies, some of which have been characterized structurally. 56,72,79,412,417,418 Furthermore, despite being synthetically more demanding, several examples with porphyrinates with tethered axial bases have also been reported as an approach for generating stable 5C iron(II) complexes. 79,419–423 Due to the intramolecular iron-base coordination, these systems produce 5C Fe II complexes with greater yield and purity as compared to systems which require an exogenous base.…”

Section: Heme/dioxygen Interactions: From Biology To Model Systemsmentioning

confidence: 99%

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function

et al. 2018

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Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e− reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper–O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme–Cu models, evaluating experimental and computational results, which highlight important fundamental structure–function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.

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“…Hemoglobin (Hb), a necessary vehicle for oxygen carriage in the body, has the same natural quaternary structure as the enzyme. It contains four polypeptide subunits and each polypeptide chain contains a heme group that may be able to serve as the active center . In a recent paper, Hb was used as a mimetic enzyme for HRP because they have similar spatial structure and Hb is cheaper and more stable than HRP .…”

Section: Introductionmentioning

confidence: 99%

Determination of selenium via the fluorescence quenching effect of selenium on hemoglobin‐catalyzed peroxidative reaction

2014

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A new method for the determination of selenium based on its fluorescence quenching on the hemoglobin-catalyzed reaction of H2 O2 and l-tyrosine has been established. The effect of pH, foreign ions and the optimization of variables on the determination of selenium was examined. The calibration curve was found to be linear between the fluorescence quenching (F0 /F) and the concentration of selenium within the range of 0.16-4.00 µg/mL. The detection limit was 1.96 ng/mL and the relative standard deviation was 3.14%. This method can be used for the determination of selenium in Se-enriched garlic bulbs with satisfactory results.

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ChemInform Abstract: MODELS FOR THE ACTIVE SITE OF OXYGEN‐BINDING HEMOPROTEINS. DIOXYGEN BINDING PROPERTIES AND THE STRUCTURES OF (2‐METHYLIMIDAZOLE)‐MESO‐TETRA(α,α,α,α‐O‐PIVALAMIDOPHEN# YL)PORPHYRINATOIRON(II)‐ETHANOL AND ITS DIOXYGEN ADDUCT

Cited by 4 publications

References 1 publication

Trans-substitution of the proximal hydrogen bond in myoglobin: I. Structural consequences of hydrogen bond deletion

Trans-substitution of the proximal hydrogen bond in myoglobin: I. Structural consequences of hydrogen bond deletion

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function

Determination of selenium via the fluorescence quenching effect of selenium on hemoglobin‐catalyzed peroxidative reaction

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