scholarly journals Analysis of oxygen binding by hemoglobin on the basis of mean intrinsic thermodynamic quantities.

2006 ◽  
Vol 53 (3) ◽  
pp. 563-568 ◽  
Author(s):  
Abdol-Khalegh Bordbar ◽  
Sayed Habib-Allah Mousavi ◽  
Hamid Dazhampanah
Keyword(s):  
Binding Affinity ◽  
Compensation Effect ◽  
Cooperative Interaction ◽  
Thermodynamic Quantities ◽  
Oxygen Binding ◽  
Protein Species ◽  
Binding Data ◽  
Hoff Equation ◽  
Binding Curve ◽  
Partial Oxygen

The binding data for oxygenation of human hemoglobin, Hb, at various temperatures and in the absence and presence of 2,3-diphosphoglycerate, DPG, and inositol hexakis phosphate, IHP, were analyzed for extraction of mean intrinsic Gibbs free energy, DeltaGo, enthalpy, DeltaHo, and entropy, DeltaSo, of binding at various partial oxygen pressures. This method of analysis considers all the protein species present such as dimer and tetramer forms which were not considered by Imai et al. (Imai K et al., 1970, Biochim Biophys Acta 200: 189-196), in their analysis which was based on Adair equation. In this regard, the values of Hill equation parameters were estimated with high precision at all points of the binding curve and used for calculation of DeltaGo, DeltaHo and DeltaSo were also calculated by analysis of DeltaGo values at various temperatures using van't Hoff equation. The results represent the enthalpic nature of the cooperativity in Hb oxygenation and the compensation effect of intrinsic entropy. The interpretation of results also to be, into account the decrease of the binding affinity of sites for oxygen in the presence of DPG and IHP without any considerable changes in the site-site interaction (extent of cooperativity). In other words, the interactions between bound ligands, organic phosphates and oxygen, are more due to a decreasing binding affinity and not to the reduction of the cooperative interaction between sites. The results also document the more heterotropic effect of IHP compared to DPG.

scholarly journals Increased blood-oxygen binding affinity in Tibetan and Han Chinese residents at 4200 m

2014 ◽  
Vol 99 (12) ◽  
pp. 1624-1635 ◽  
Author(s):  
T. S. Simonson ◽  
G. Wei ◽  
H. E. Wagner ◽  
T. Wuren ◽  
A. Bui ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Han Chinese ◽  
Oxygen Binding ◽  
Blood Oxygen

scholarly journals LC-MS Analysis of Anti-Sickling Compounds in Cord Blood Derived RBCs Demonstrates Modification of Fetal Hemoglobin and Globin Chain Binding Preferences

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1074-1074
Author(s):  
Benjamin Vieira ◽  
Vu P. Hong ◽  
Kunal Desai ◽  
Martin K. Safo ◽  
David R. Light
Keyword(s):  
Cord Blood ◽  
Binding Affinity ◽  
Oxygen Affinity ◽  
Fetal Hemoglobin ◽  
Oxygen Binding ◽  
Globin Chain ◽  
Employment Equity ◽  
Globin Chains ◽  
N Terminus ◽  
Equity Ownership

Abstract Sickle cell disease (SCD) is a genetic hemoglobinopathy driven largely by a single codon mutation of the β-globin gene resulting in polymerization of hemoglobin S (HbS). Anti-sickling approaches that involve increasing the oxygen affinity of HbS to treat SCD are under development and offer the potential to directly prevent HbS polymerization and its downstream pathophysiology. Two such compounds, 5-hydroxymethylfurfural (5HMF) and voxelotor (GBT440) have entered clinical trials for SCD with promising results and exert their therapeutic effects by modifying the N-terminus of HbS α-globin chains to form a reversible Schiff base. Formation of this N-terminal adduct stabilizes the oxygen-bound R-state (in the R2 conformation) that increases the oxygen affinity of the altered HbS and delaying the polymerization of HbS. In addition, genetic and small molecule therapies designed to increase fetal hemoglobin (HbF) expression hold great potential for the treatment of SCD. Increasing the percentage of HbF in RBCs significantly slows sickling kinetics without affecting oxygen delivery. Combination approaches of high-O2-Hb modification with HbF inducing therapies clinically could result in increased efficacy in the treatment of SCD, but the impact of hemoglobin modifiers on fetal hemoglobin has not been reported. Our present studies investigated the effects of 5HMF and voxelotor in HbF-rich umbilical cord blood derived RBCs. HbF-rich (60-90%) RBCs were isolated from cord blood and incubated with commercially available 5HMF and voxelotor synthesized in-house. The effect of these compounds on hemoglobin oxygen affinity was determined by measuring the p50 of the oxygen saturation curve in whole cells. Sites of modification were determined directly by incubating compounds with the purified RBC lysate, stabilizing the N-terminal adduct by reduction to the amine, and analysis of the resulting modification by LC-MS. Similar to the reported p50 shifts with normal adult hemoglobin (HbA) and HbS, 5HMF and voxelotor increased the oxygen-binding affinity of HbF with an EC50 of 7.9 mM and 560 mM respectively. 1 mM voxelotor lowered cord RBC p50 to 4 mmHg in vitro. LC-MS analysis showed that 5HMF exclusively modified the N-terminus of the α-globin chain, with no modification of b-globin and g-globin chains. Unexpectedly, the α-globin, β-globin and γ-globin chains were all modified by voxelotor following incubation with cord blood. Voxelotor was also shown to modify both α-globin and the β-globin or βS-globin chains on purified HbA or HbS, respectively. These data contrast with published crystallography data demonstrating that voxelotor selectively modifies a single α-globin chain in CO-ligated HbS (Oksenberg et al 2016). Although anti-sickling aromatic aldehydes have similar effects on the oxygen binding affinity of HbA, HbS and HbF, they can vary in their selectivity for modification of the α-globin and beta-like chains of HbF, HbA, and HbS (Abraham et al. 1995). To further investigate our data with voxelotor and increase our understanding of this class of molecules, other hemoglobin modifying aldehyde molecules such as 5-formylsalicyclic acid (5FSA), tucaresol and velaresol (BW12C) will be examined. Disclosures Vieira: Bioverativ a Sanofi Company: Employment. Hong:Bioverativ a Sanofi Company: Employment, Equity Ownership. Desai:Bioverativ a Sanofi Company: Employment, Equity Ownership. Safo:Bioverativ a Sanofi Company: Consultancy; Virginia Commonwealth University: Employment. Light:Bioverativ a Sanofi Company: Employment, Equity Ownership.

scholarly journals Graphic representation of pharmacology: Development of an alternative model

2017 ◽  
Vol 7 (5) ◽  
pp. 201-206 ◽  
Author(s):  
Stephen R. Saklad
Keyword(s):  
Binding Affinity ◽  
Receptor Binding ◽  
Functional Data ◽  
Binding Affinities ◽  
Inverse Agonists ◽  
Receptor Sites ◽  
Binding Data ◽  
And Function ◽  
Pie Chart

Abstract Introduction: Providing clinicians with an easy to grasp and understandable representation of pharmacology is important to allow optimal clinical decisions to be made. Two of the most clinically relevant dimensions are receptor binding affinity and functional activity. The binding affinity for an agonist is described by the dissociation constant (KA), and an antagonist by the inhibition constant (Ki). Functionally, medications can act as superagonists, agonists, partial agonists, antagonists, partial inverse agonists, or inverse agonists at several receptor sites, transporters, or ion channels. Comprehending the differences between agents is complicated by the number and types of binding sites. Methods: Binding and functional data are obtained from primary literature, product labels, human cloned receptor binding, and other sources. Binding affinities are converted into ratios relative to the putative primary receptor for that category of agent. Antipsychotic binding is referenced to dopamine type 2 long (D2L) receptor binding. Binding affinity ratios (BARs) generate a 6-spoked diagram, with D2L as the hub. The most avidly bound sites are the spokes, and the disk diameter represents the BAR. Where functional data are available, they are shown as a pie chart shading the binding site's disk. Results: Binding and function diagrams are shown for the antipsychotics where binding data are available and are compared to previous methods of pharmacologic comparisons of antipsychotics. Discussion: Use of graphic models of psychotropic pharmacology improves clinician comprehension and may serve as an aid to improve rational therapeutics and patient outcomes.

scholarly journals Partial oxygen-dissociation of crystalline giant hemoglobin

2014 ◽  
Vol 70 (a1) ◽  
pp. C474-C474 ◽  
Author(s):  
Nobutaka Numoto ◽  
Taro Nakagawa ◽  
Akiko Kita ◽  
Nobutoshi Ito ◽  
Yoshihiro Fukumori ◽  
...  
Keyword(s):  
Structural Changes ◽  
Quaternary Structure ◽  
Oxygen Binding ◽  
Nitrogen Gas ◽  
Soaking Time ◽  
Allosteric Mechanism ◽  
Oxygen Dissociation ◽  
Intermediate States ◽  
Complete Dissociation ◽  
Partial Oxygen

Allosteric oxygen-binding of hemoglobin (Hb) has been widely discussed based on the quaternary structural changes elucidated by the crystal structures of the oxygenated and deoxygenated states. However, it remains to be determined the structure of intermediate states between the oxy and deoxy forms without any artificial modification of the Hb molecule. A tubeworm, Lamellibrachia satsuma has extracellular giant hemoglobins with a molecular mass of about 400 and 3,600 kDa. Recently, we have determined the crystal structure of the 400 kDa Hb (V2Hb) in the oxy state, and then we successfully obtained the deoxygenated crystals of V2Hb from oxy crystals by the soaking methods [1]. These findings encourage us to initiate structural studies for the intermediate states between the oxy and deoxy forms of V2Hb, which should provide a more accurate understanding of the allosteric mechanism of Hbs. The deoxy crystals of V2Hb were obtained from oxy crystals through the soaking in a solution containing 50 mM sodium hydrosulfite, and incubated for a few minutes. We tested various soaking times from 3 s to 180 s and then immediately flash-frozen under a nitrogen gas stream. The obtained structures reveal that in the case of the soaking time was longer than 10 s, the electron densities of the oxygen molecules at some heme pockets (oxygen binding sites) were very week or disappeared. These `intermediate' structures show almost the same quaternary structure as that of the oxy structure. This fact suggests that quaternary rearrangement of V2Hb might arise just before a complete dissociation of all the oxygen molecules from all the subunits.

scholarly journals Intraspecific variation and plasticity in mitochondrial oxygen binding affinity as a response to environmental temperature

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Dillon J. Chung ◽  
P. R. Morrison ◽  
H. J. Bryant ◽  
E. Jung ◽  
C. J. Brauner ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Intraspecific Variation ◽  
Environmental Temperature ◽  
Oxygen Binding

scholarly journals Delayed Addition of Template Molecules Enhances the Binding Properties of Diclofenac-Imprinted Polymers

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1178 ◽  
Author(s):  
Laura Anfossi ◽  
Simone Cavalera ◽  
Fabio Di Nardo ◽  
Giulia Spano ◽  
Cristina Giovannoli ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Polymerization Process ◽  
Template Molecule ◽  
Imprinted Polymer ◽  
Binding Selectivity ◽  
Binding Properties ◽  
Imprinted Polymers ◽  
Binding Data ◽  
Binding Isotherms ◽  
The Stability

It has been reported that in the molecular imprinting technique, the use of preformed oligomers instead of functional monomers increases the stability of the non-covalent interactions with the template molecule, providing a sharp gain in terms of binding properties for the resulting imprinted polymer. Based on this theory, we assumed that the delayed addition of template molecules to a polymerization mixture enhances the binding properties of the resulting polymer. To verify this hypothesis, we imprinted several mixtures of 4-vinylpyridine/ethylene dimethacrylate (1:6 mol/mol) in acetonitrile by adding diclofenac progressively later from the beginning of the polymerization process. After polymerization, the binding isotherms of imprinted and non-imprinted materials were measured in acetonitrile by partition equilibrium experiments. Binding data confirm our hypothesis, as imprinted polymers prepared by delayed addition, with delay times of 5 and 10 min, showed higher binding affinity (Keq = 1.37 × 104 L mol−1 and 1.80 × 104 L mol−1) than the polymer obtained in the presence of template at the beginning (Keq = 5.30 × 103 L mol−1). Similarly, an increase in the imprinting factor measured vs. the non-imprinted polymer in the binding selectivity with respect to mefenamic acid was observed. We believe that the delayed addition approach could be useful in prepar imprinted polymers with higher binding affinity and increased binding selectivity in cases of difficult imprinting polymerization.

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