Reversible oxygen adduct formation in cobalt(II) picket fence porphyrins

Collman, James P.; Gagné, Robert R.; Kouba, J. K.; Ljusberg‐Wahren, Helena

doi:10.1021/ja00828a064

Cited by 68 publications

(28 citation statements)

References 7 publications

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“…The crystal structure of the iron picket fence O 2 adduct was determined as shown in Figure 5. [76][77][78] Many O 2 binding porphyrin models were subsequently prepared and characterized. 64,[76][77][78][79][80][81] (2) The Competitive CO Binding Problem.…”

Section: Synthetic Analogues Of Hemoglobin and Myoglobin Proteinsmentioning

confidence: 99%

Synthetic Models for Hemoglobin and Myoglobin

1999

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1) Myoglobin and Hemoglobin. Dioxygen (O 2 ) binds to certain coordinatively unsaturated transition metal ions, forming O 2 complexes. Biological dioxygen carriers are reversible O 2 complexes in which the extent of binding depends on temperature, partial pressure of oxygen, and pH.Myoglobin (Mb) and hemoglobin (Hb) are the most common reversible O 2 binders in biological systems; they are responsible for the storage and transport of O 2 in most aerobic organisms. Myoglobin and hemoglobin are structurally similar. Myoglobin contains one heme prosthetic group; hemoglobin consists of four Mb-like subunits (2R + 2 ), each containing one heme prosthetic group.Myoglobin stores O 2 in muscles to permit short bursts of metabolism at rates much greater than those which would be allowed by circulatory oxygen transport. In its native deoxy form (Figure 1), the ferrous ion of the heme is in a five-coordinate high-spin state (S ) 2), with the imidazole group (His 93) serving as the axial ligand on the proximal side. Myoglobin reversibly binds molecular oxygen in the sixth, distal, vacant coordination site. Distal amino acid residues (e.g., His 64) control the immediate environment. They can induce polar, hydrophobic, or steric interactions which help regulate the affinities of the bound ligands.Hemoglobin, on the other hand, transports O 2 in blood and adjusts binding affinity to various conditions required for appropriate uptake and release of O 2 through a series of allosteric interactions. 1,2 Through the "allosteric effect", the subsequent gas binding affinity of Hb is made greater in the presence of O 2 or carbon monoxide (CO) than in their absence. Myoglobin, having only one heme site per protein, shows no such effect.(2) Control of Ligand-Binding Thermodynamics. Evidence to date suggests that the amino acid residues on the distal porphyrin face are capable of stabilizing the oxygen adduct while destabilizing the competing complex derived from binding of the endogenous toxic ligand CO. 3 Studies have shown that, in the absence of the globin protein, imidazole-ligated heme has a CO affinity much greater than that of the protein-bound heme, indicating that the protein plays a role in decreasing CO affinity. 4 The most significant distal effect invoked in the stabilization of O 2 in Hb is the hydrogen-bonding interaction between coordinated O 2 and the distal histidine, which was initially proposed by Pauling. 5 Subsequent experiments have provided evidence for H-bonding of ironbound dioxygen with the distal histidine. 6-10 A unique Hb from the bloodworm Ascaris (shown in Figure 2) has a remarkably high affinity for O 2 , nearly 10 4 times that of mammalian Hb. 11,12 The origin of this high O 2 affinity is believed to be (1) a strong H-bond between tyrosine (Tyr

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Section: Synthetic Analogues Of Hemoglobin and Myoglobin Proteinsmentioning

confidence: 99%

Synthetic Models for Hemoglobin and Myoglobin

1999

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“…The pseudofirst-order rate constant was found to increase linearly with an increase in NO pressure in the range 10-180 Torr. These (NO)Co II salen + hν f **(NO)Co II salen (10) **(NO)Co II salen 98 k r Co II salen + NO (11) **(NO)Co II salen 98 k nr (NO)Co II salen (12) φ NO )φ i k r (k r + k nr ) -1 (13) k r ) k r 0 exp(-∆E r /RT)…”

Section: Discussionmentioning

confidence: 99%

Photochemistry of Nitrosyl Metal Complexes. Laser Photolysis Studies of Nitrosylcobalt Schiff Bases in Ethanol and Toluene in the Temperature Range 160−300 K

et al. 1996

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N,N′-Disalicylideneethylenediaminato)cobalt(II), Co II salen, and (N,N′-bis(1-methyl-3-oxobutylidene)ethylenediaminato)cobalt(II), Co II acacen, in both ethanol and toluene react with nitric oxide to give the nitric oxide adducts, (NO)Co II salen and (NO)Co II acacen. The laser photolysis studies revealed that (NO)Co II salen photodissociates NO to yield Co II salen with the quantum yields 1.0 ( 0.1 in ethanol and 0.6 ( 0.1 in toluene at 300 K. The transient product, Co II salen, undergoes the recombination reaction with NO to regenerate (NO)Co II salen with the rate constant 1.1 × 10 9 M -1 s -1 . The quantum yields, φ, for photodissociation of NO from (NO)Co II acacen are obtained as φ ) 1.0 ( 0.1 and φ < 0.01 in toluene and ethanol, respectively. The quantum yields φ for both (NO)Co II salen and (NO)Co II acacen are found to be markedly dependent on temperature: the yield decreases with a decrease in temperature. The photodissociation mechanism of NO from (NO)Co II salen and (NO)Co II acacen is discussed on the basis of the laser photolysis studies carried out in the temperature range 160-300 K. Bunsen absorption coefficients of NO in ethanol and toluene at 300 K were determined from kinetic analysis of the recombination reaction between NO and cobalt(II) Schiff bases.

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“…[1][2][3][4][5][6] Heterocyclic functional groups [7][8][9][10][11][12][13][14][15][16][17][18] including pyridine, imidazole, thiazole, pyrazole, etc., show high affinity for gold, palladium, silver, and mercury. Earlier reports [19][20][21] have shown the usefulness of the chelating resins anchoring heterocyclic functional groups to a solid support in a polymer matrix for the separation of Hg 2þ , Ag þ , Au 3þ , and Pd 2þ in trace quantities from geological, medicinal, and environmental samples.…”

Section: Introductionmentioning

confidence: 99%

Macroporous chelating resins incorporating heterocyclic functional groups via hydrophilic PEG spacer arms. I. Synthesis and characterization

Sun

et al. 2006

J of Applied Polymer Sci

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A series of novel chelating resins were synthesized by incorporating heterocyclic functional groups such as 2-aminopyridine (AP), 2-amino-5-methylthio-1,3,4-thiadizole (AMTZ), 2-amino-5-ethyl-1,3,4-thiadizole (AETZ), and 2-mercaptobenzothiazole (MBZ) into macroporous crosslinked polystyrene via a hydrophilic spacer arm of polyethylene glycol containing sulfur. Structures of the above-mentioned resins were characterized by elemental analysis, Fourier transform-infrared spectra (FTIR), ASAP-2020 surface area and porosity analyzer, and scanning electron microscopy (SEM).

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Reversible oxygen adduct formation in cobalt(II) picket fence porphyrins

Cited by 68 publications

References 7 publications

Synthetic Models for Hemoglobin and Myoglobin

Synthetic Models for Hemoglobin and Myoglobin

Photochemistry of Nitrosyl Metal Complexes. Laser Photolysis Studies of Nitrosylcobalt Schiff Bases in Ethanol and Toluene in the Temperature Range 160−300 K

Macroporous chelating resins incorporating heterocyclic functional groups via hydrophilic PEG spacer arms. I. Synthesis and characterization

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