Crystal structure of monomeric hydrated iron(<scp>III</scp>) 5,10,15,20-tetra(N-methyl-4-pyridinio)porphyrin pentachloride; an ionic haem model

Körber, F.; Smith, John R. Lindsay; Prince, Stephen M.; Rizkallah, P.J.; Reynolds, C. D.; Shawcross, David R.

doi:10.1039/dt9910003291

Cited by 22 publications

(14 citation statements)

References 22 publications

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“…Following four rounds of refinement and model fitting, each water moved to a position that is 2.9 Å away from the iron, allowing the water to hydrogen bond to the distal histidine. Although this distance is consistent with that observed in the structure of the aquomet form of Chironomous thummi Hb (55), the water-to-iron distance of chicken Hb D differs from the corresponding values observed both in the structure of horse aquomet Hb (30) and in the high resolution structures of ferric porphyrins complexed with water ligands (56,57). Re-examination of the electron density from a set of simulated annealing 2F o Ϫ F c omit maps suggests that three of the four subunits are ligated to oxygen and the fourth (the ␣ 2 subunit) is ligated to water (Fig.…”

Section: Overall Structure and The Comparison With Humansupporting

confidence: 60%

The Structural and Functional Analysis of the Hemoglobin D Component from Chicken

Knapp

Oliveira

Xie

et al. 1999

Journal of Biological Chemistry

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Oxygen binding by chicken blood shows enhanced cooperativity at high levels of oxygen saturation. This implies that deoxy hemoglobin tetramers self-associate. The crystal structure of an R-state form of chicken hemoglobin D has been solved to 2.3-Å resolution using molecular replacement phases derived from human oxyhemoglobin. The model consists of an ␣ 2 ␤ 2 tetramer in the asymmetric unit and has been refined to a R-factor of 0.222 (R-free ‫؍‬ 0.257) for 29,702 reflections between 10.0-and 2.3-Å resolution. Chicken Hb D differs most from human oxyhemoglobin in the AB and GH corners of the ␣ subunits and the EF corner of the ␤ subunits. Reanalysis of published oxygen binding data for chicken Hbs shows that both chicken Hb A and Hb D possess enhanced cooperativity in vitro when inositol hexaphosphate is present. The electrostatic surface potential for a calculated model of chicken deoxy-Hb D tetramers shows a pronounced hydrophobic patch that involves parts of the D and E helices of the ␤ subunits. This hydrophobic patch is a promising candidate for a tetramer-tetramer interface that could regulate oxygen binding via the distal histidine.The oxygen binding curves of chicken blood samples taken at different stages of development exhibit Hill coefficients which exceed 4.0 (super-cooperativity) at oxygen saturation levels between 70 and 90% oxygenation (1-5). Elevated levels of oxygen-binding cooperativity should be advantageous because such hemoglobins (Hbs) 1 would deliver a greater quantity of oxygen to the tissues under normal physiological conditions. Super-cooperativity has also been observed in the blood and Hbs of several species of amphibians (6 -8), reptiles (9 -10), other birds (1, 11), and embryonic mammals (12-14). Although incomplete oxygen saturation resulted in spuriously high Hill coefficients in much of the early data (see , the data of Lapennas and Reeves (5) on chicken blood and Holland et al.(12-14) on embryonic marsupial blood were obtained at saturating pressures of O 2 .The blood of adult chickens, as in most other birds, is composed of two Hb components that have identical ␤ chains but differ in the sequences of the ␣ subunits. Hb A (␣ The cooperative binding of oxygen by tetrameric Hbs arises from the transition of the Hb from a conformation with a low oxygen affinity (T-state) to a conformation with a high oxygen affinity (R-state) (21,22). Much of our understanding of this process has come from the crystallographic analysis of the unligated (T-state) and ligated (R-state) structures of both human Hb A (23-26) and horse . Although a structural explanation of super-cooperativity requires the crystallographic analysis of both the R-and T-state forms of chicken Hb D, the analysis of intermediate structures are likely to be necessary for understanding the mechanism of cooperativity because knowledge of two thermodynamic states does not itself determine the pathway between them. We report here the structure of an R-state form of chicken Hb D solved with diffraction data to 2.3-Å resolution. Th...

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Section: Overall Structure and The Comparison With Humansupporting

confidence: 60%

The Structural and Functional Analysis of the Hemoglobin D Component from Chicken

Knapp

Oliveira

Xie

et al. 1999

Journal of Biological Chemistry

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“…Only few examples show that crystalline products can be obtained from solution without such sequestering agents: e.g. Na 4 [Sn 9 ](en) n (n ϭ 4, 5, 7) [13], Rb 4 [Ge 9 ](en) [14], and [Li(NH 3 ) 4 ] 4 [E 9 ](NH 3 ) (E ϭ Sn, Pb) [15]. The cations in these compounds are partially coordinated by solvent molecules.…”

Section: Introductionmentioning

confidence: 99%

First Synthesis of Group‐14 Polyanions by Extraction of a Binary Alloy with dmf and a Novel Conformation of the (Ge₉−Ge₉)⁶⁻ Dimer: Crystal Structures of [K₆(Ge₉−Ge₉)](dmf)₁₂, [Rb₆(Ge₉−Ge₉)](dmf)₁₂ and [K_2.5Cs_3.5(Ge₉−Ge₉)](dmf)₁₂.

Nienhaus

Hoffmann

Fässler

2006

Zeitschrift anorg allge chemie

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Crystals of the title compounds [K 6 (Ge 9 ϪGe 9 )](dmf) 12 (1) and [Rb 6 (Ge 9 ϪGe 9 )](dmf) 12 (2) have been synthesized by dissolving binary phases of the formal composition K 4 Ge 9 and Rb 4 Ge 9 , respectively, in N,N-dimethylformamide (dmf) and subsequent cooling to Ϫ36°C. [K 2.5 Cs 3.5 (Ge 9 ϪGe 9 )](dmf) 12 (3) was obtained as a by-product during the reaction of K 2 Cs 2 Ge 9 with sulphur in dmf. Single crystal structure analyses of 1, 2 and 3 show that all compounds contain dimeric [Ge 9 ϪGe 9 ] 6Ϫ units. The dimers are connected via the alkali metal atoms in form of [(A ϩ ) 3 (µ 2 Ϫdmf) 6 ] chains and build a two-dimensional square net of the composition 2 ϱ {A 6 (dmf) 12 [Ge 9 ϪGe 9 ]} with A ϭ K and Rb for 1 and 2, respectively. [(Cs ϩ ϪK ϩ ϪCs ϩ )(µ 2 Ϫdmf) 6 ] linkages bridge the dimers in 3 under formation of 2 ϱ {K 2.5 Cs 3.5 (dmf) 12 [Ge 9ϪGe 9 ]}. 1 crystallized in the tetragonal space group I4 with a ϭ b ϭ 34.003(5), c ϭ

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“…Both optimized structures do not display significant distortion of the porphyrin plane from planarity, as experimentally found in several isolated MT4 species. 16 We interpret the observed distortion in the crystal as an effect arising from the interorbital interactions within the porphyrin stack. DFT calculations suggest that orbital interactions 17 among stacked porphyrins do contribute to stabilizing the observed supramolecular architecture.…”

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Assembly of Positively Charged Porphyrins Driven by Metal Ions: A Novel Polymeric Arrangement of Cationic Metalloporphyrin

et al. 2004

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Crystallization and crystal structure analysis of chlorohydrates of either tri- or tetracationic copper porphyrins, namely copper(5,10,15-tris(N-methyl-pyridinium-4-yl)-20-pyridine-porphyrinato) (1) and copper(5,10,15,20-tetrakis(N-methyl-pyridinium-4-yl)-porphyrinato), respectively, have been performed. Two crystalline forms, 2 and 3, of the latter have been obtained under different preparation conditions. A novel kind of slipped stack chains of these cationic porphyrins has been detected. The pronounced saddle conformation of the porphyrin reveals pi-like interactions between the peripheral pyrrole Cb-Cb- "double bond" and the metal center. DFT calculations on the isolated porphyrins clearly show the HOMO orbitals with the correct topology to yield a bonding interaction among the stacked porphyrin units. To our knowledge, a slipped stack chain of positively charged porphyrins has never been previously reported, if the arrangement of faced units of monocationic metalloporphyrins or phthalocyanins is excluded.

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Crystal structure of monomeric hydrated iron(III) 5,10,15,20-tetra(N-methyl-4-pyridinio)porphyrin pentachloride; an ionic haem model

Cited by 22 publications

References 22 publications

The Structural and Functional Analysis of the Hemoglobin D Component from Chicken

The Structural and Functional Analysis of the Hemoglobin D Component from Chicken

First Synthesis of Group‐14 Polyanions by Extraction of a Binary Alloy with dmf and a Novel Conformation of the (Ge₉−Ge₉)⁶⁻ Dimer: Crystal Structures of [K₆(Ge₉−Ge₉)](dmf)₁₂, [Rb₆(Ge₉−Ge₉)](dmf)₁₂ and [K_2.5Cs_3.5(Ge₉−Ge₉)](dmf)₁₂.

Assembly of Positively Charged Porphyrins Driven by Metal Ions: A Novel Polymeric Arrangement of Cationic Metalloporphyrin

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Crystal structure of monomeric hydrated iron(III) 5,10,15,20-tetra(N-methyl-4-pyridinio)porphyrin pentachloride; an ionic haem model

Cited by 22 publications

References 22 publications

The Structural and Functional Analysis of the Hemoglobin D Component from Chicken

The Structural and Functional Analysis of the Hemoglobin D Component from Chicken

First Synthesis of Group‐14 Polyanions by Extraction of a Binary Alloy with dmf and a Novel Conformation of the (Ge9−Ge9)6− Dimer: Crystal Structures of [K6(Ge9−Ge9)](dmf)12, [Rb6(Ge9−Ge9)](dmf)12 and [K2.5Cs3.5(Ge9−Ge9)](dmf)12.

Assembly of Positively Charged Porphyrins Driven by Metal Ions: A Novel Polymeric Arrangement of Cationic Metalloporphyrin

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First Synthesis of Group‐14 Polyanions by Extraction of a Binary Alloy with dmf and a Novel Conformation of the (Ge₉−Ge₉)⁶⁻ Dimer: Crystal Structures of [K₆(Ge₉−Ge₉)](dmf)₁₂, [Rb₆(Ge₉−Ge₉)](dmf)₁₂ and [K_2.5Cs_3.5(Ge₉−Ge₉)](dmf)₁₂.