Oxygen-Binding Profile of the Iron Porphyrin Complex Embedded in Polymerized Liposome: Effect of the Polymerized Liposome on the Stability and the Oxygen-Binding Ability of the Iron Porphyrin Complex

1987 ◽  
Vol 24 (3-4) ◽  
pp. 333-341 ◽  
Author(s):  
E. Tsuchida ◽  
H. Nishide ◽  
M. Yuasa
Keyword(s):  
Iron Porphyrin ◽  
Oxygen Binding ◽  
Binding Ability ◽  
Binding Profile ◽  
Porphyrin Complex ◽  
The Stability

Effects of Appended Poly(ethylene glycol) on Electrochemical CO2 Reduction by an Iron Porphyrin Complex

2021 ◽  
Vol 60 (6) ◽  
pp. 3843-3850
Author(s):  
Ashwin Chaturvedi ◽  
Caroline K. Williams ◽  
Nilakshi Devi ◽  
Jianbing “Jimmy” Jiang
Keyword(s):  
Ethylene Glycol ◽  
Co2 Reduction ◽  
Iron Porphyrin ◽  
Poly Ethylene Glycol ◽  
Porphyrin Complex ◽  
Electrochemical Co2 Reduction ◽  
Poly Ethylene

scholarly journals Correlation between composition and activity of gold nanoparticle conjugates with streptococcal protein G

2020 ◽  
Vol 10 (2) ◽  
pp. 4988-4992
Keyword(s):  
Dissociation Constant ◽  
Equilibrium Constants ◽  
Gold Surface ◽  
Binding Activity ◽  
Protein G ◽  
Binding Ability ◽  
Adsorbed Protein ◽  
Streptococcal Protein G ◽  
The Stability ◽  
Nanoparticle Complex

The composition of the conjugates of gold nanoparticles with streptococcal protein G was studied using fluorescence spectroscopy. The method for determining the composition is based on measuring the intrinsic fluorescence of tryptophan as part of the protein. The equilibrium constants of protein binding by the gold surface were determined using the Sketchard method. An increase in the dissociation constant of the protein–nanoparticle complex for increasing the amount of bound protein was demonstrated, and a relationship was established between the stability of the conjugates, their antigen-binding activity, and the dissociation constant. The effectiveness of the conjugates of different compositions in immunochromatographic assay of specific antibodies against the lipopolysaccharide antigen of Brucella abortus was compared. The binding ability of the conjugates increased along with the amount of protein G to ~200 molecules per nanoparticle. A further increase in the amount of adsorbed protein led to a deterioration in the functional activity of the conjugates.

Self-association, cooperativity and supercooperativity of oxygen binding by hemoglobins.

1998 ◽  
Vol 201 (8) ◽  
pp. 1073-1084 ◽  
Author(s):  
A F Riggs
Keyword(s):  
Muscle Tissue ◽  
Buoyant Density ◽  
Fold Increase ◽  
Heme Iron ◽  
Common Mechanism ◽  
Oxygen Binding ◽  
Hypoxic Environment ◽  
Self Association ◽  
The Stability ◽  
O2 Binding

Cooperative ligand binding by tetrameric vertebrate hemoglobins (Hbs) makes possible the delivery of oxygen at higher pressures than would otherwise occur. This cooperativity depends on changes in dimer-dimer interactions within the tetramer and is reflected in a 50 000-fold increase in the tetramer-dimer dissociation constant in human Hb upon oxygenation at pH 7.4, from approximately 2x10(-11)mol l-1 to approximately 10(-6)mol l-1. Hbs that undergo such ligand-dependent changes in association are widespread in non-vertebrates, where the mechanisms are very different from those in vertebrates. Oligomeric Hbs have been identified in organisms in five phyla (molluscs, echinoderms, annelids, phoronids and chordates) that dissociate to subunits upon oxidation of the heme iron and reassociate with the binding of ferric iron ligands such as CN-, N3- or NO2-. Thus, the valence and ligand state of the heme iron control the stability of a critical subunit interface. The broad distribution of this phenomenon suggests a common mechanism of communication between heme and interface that may be almost universal among non-vertebrate Hbs. This interaction may be similar to that known for the homodimeric Hb of the mollusc Scapharca inaequivalvis. Although muscle tissue Hbs or myoglobins (Mbs) are usually monomeric, with non-cooperative O2 binding, the radular muscles of gastropod molluscs and chitons have homodimeric Mbs that bind O2 cooperatively. Cooperative non-muscle tissue Hbs have also been identified. These include the neural Hb of the nemertean worm Cerebratulus lacteus and the Hb of the diving beetle Anisops assimilis, which exhibit deoxygenation-dependent self-association of monomers that is associated with high Hill coefficients. Calculations suggest that the 2-3 mmol l-1 concentration of Hb on a heme basis in the brain of Cerebratulus should substantially extend the time as an active predator in an anaerobic or hypoxic environment. Oxygen from the Hb of Anisops is delivered to a gas bubble and thereby controls the buoyant density. Many Hbs of amphibians, reptiles, birds and some embryonic mammals exhibit a further 'supercooperativity' of O2 binding which depends on reversible deoxygenation-dependent tetramer-tetramer association to form an assemblage with a very low affinity for O2. This phenomenon results in steeper O2-binding curves than exhibited by tetramers alone. The increased cooperativity should result in an increase in the amount of O2 delivered to the tissues and should be especially valuable for avian flight muscles.

Discontinuous spectrocolorimetric titration method for determining stability constants of fulvic acid - iron complexes

Soil Research ◽  
1997 ◽  
Vol 35 (6) ◽  
pp. 1279 ◽  
Author(s):  
S. B. Pandeya ◽  
A. K. Singh
Keyword(s):  
Stability Constant ◽  
Stability Constants ◽  
Aqueous Media ◽  
Poultry Manure ◽  
Fulvic Acids ◽  
Titration Method ◽  
Binding Ability ◽  
Press Mud ◽  
Determining Factors ◽  
The Stability

The stability constants for the complexes formed between iron species existing in ambient soil environment and fulvic acids (FA) extracted from organic wastes like sewage sludge, farm yard manure (FYM), poultry manure, and press mud were determined in aqueous media of pH 5·0 and 8·5 by discontinuous spectrocolorimetric titration method. The values of stability constant (log K) of Fe–FA complexes estimated at pH 5·0 were 6·026, 6·212, 6·270, and 6·342 for FYM, sludge, poultry manure, and press mud, respectively. The respective values at pH 8·5 were 6·145, 6·276, 6·350, and 6·940. The order of the values of log K for different preparations of fulvic acids was press mud > poultry manure > sludge > FYM. The functional group contents, their pH of neutralisation, and electrostatic properties of the FA such as pKINT, pKm, and 0·868 nW, were found to be the determining factors for maximum binding ability of FA for metal cations and the stability constant of Fe–FA for different FA preparations. The basic assumptions and the limitations of the discontinuous spectrocolorimetric estimation of stability constants for Fe–FA are discussed.

Preparation, Photophysical, Electrochemical, and Ion-Binding Properties of Ru(II) Polypyridyl Complexes Containing a Crown Ether Unit

2011 ◽  
Vol 66 (9) ◽  
pp. 923-929 ◽  
Author(s):  
Feixiang Cheng ◽  
Ning Tang ◽  
Jishu Chen ◽  
Fan Wang ◽  
Longhai Chen
Keyword(s):  
Glassy Matrix ◽  
Ion Binding ◽  
Electrochemical Studies ◽  
Binding Properties ◽  
Binding Ability ◽  
Polypyridyl Ligands ◽  
Ligand Charge Transfer ◽  
Hyperchromic Effect ◽  
The Stability ◽  
Absorption And Emission Spectroscopy

Two polypyridyl ligands, 4`-(4,5-diazafluoren-9-ylimino)benzo-15-crown-5 (L1) and 4` -(4,5-diazafluoren- 9-ylimino)benzo-12-crown-4 (L2), and their Ru(II) complexes [(bpy)2RuL1](PF6)2 and [(bpy)2RuL2](PF6)2, respectively, have been synthesized and characterized. The two complexes display metal-to-ligand charge transfer absorptions at around 444 nm in CH3CN solution at r. t. and emission at around 573 nm in an EtOH-MeOH (4 : 1, v/v) glassy matrix at 77 K. Electrochemical studies of the complexes show one Ru(II)-centered oxidation at around 1.33 V and three ligandcentered reductions. The binding ability of the complexes with Na+ and Li+ has been investigated by UV/Vis absorption and emission spectroscopy and electrochemical titrations. Addition of Na+ and Li+ to solutions of the complexes results in a progressive quenching of the emission, a hyperchromic effect of the UV/Vis absorption, and a progressive cathodal shift of the Ru(II)-centered E1/2 potential. The stability constants for the stoichiometric 1 : 1 ratio of the complexes and the cations have been obtained by UV/Vis absorption titration.

scholarly journals Nanorings with copper(ii) and zinc(ii) centers: forcing copper porphyrins to bind axial ligands in heterometallated oligomers

2016 ◽  
Vol 7 (12) ◽  
pp. 6961-6968 ◽  
Author(s):  
Jonathan Cremers ◽  
Sabine Richert ◽  
Dmitry V. Kondratuk ◽  
Tim D. W. Claridge ◽  
Christiane R. Timmel ◽  
...  
Keyword(s):  
Porphyrin Complex ◽  
Axial Ligands ◽  
Copper Porphyrin ◽  
Directed Synthesis ◽  
Copper Zinc ◽  
The Stability

The stability of copper/zinc heterometallated porphyrin complex oligomers provides information on the strength of the copper porphyrin pyridine interaction. Heterometallated nanorings were prepared by template-directed synthesis.

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