Modulation of haemocyanin oxygen affinity: properties and physiological implications in a changing world

2001 ◽  
Vol 204 (5) ◽  
pp. 1021-1032 ◽  
Author(s):  
C.R. Bridges
Keyword(s):  
Oxygen Affinity ◽  
Inorganic Ions ◽  
Bohr Effect ◽  
Allosteric Modulators ◽  
Oxygen Release ◽  
Changing Environment ◽  
Flexible Response ◽  
New Findings ◽  
Inorganic And Organic ◽  
Changing World

Crustacean haemocyanin oxygen affinity may be modified through changes in concentration of various inorganic and organic allosteric modulators. These may act in both positive and negative directions, increasing or decreasing haemocyanin oxygen affinity, and assist both in oxygen loading at the gills and oxygen release in the tissues. Inorganic ions, except for Mg(2+), do not normally influence cooperativity or the Bohr effect, whereas most of the organic modulators decrease cooperativity without affecting the Bohr coefficient. Several new findings on the influence of sulphide and thiosulphate are reviewed together with evidence for unidentified factors that decrease haemocyanin oxygen affinity. The physiological implications of all these findings are discussed in the context of maintaining a flexible response to a changing environment.

Influence of carbon monoxide on hemoglobin-oxygen binding

1976 ◽  
Vol 41 (6) ◽  
pp. 893-899 ◽  
Author(s):  
M. P. Hlastala ◽  
H. P. McKenna ◽  
R. L. Franada ◽  
J. C. Detter
Keyword(s):  
Carbon Monoxide ◽  
Oxygen Affinity ◽  
Co2 Concentration ◽  
Bohr Effect ◽  
Oxygen Binding ◽  
Dissociation Curve ◽  
Low Oxygen ◽  
Oxygen Dissociation ◽  
Initial Binding ◽  
Fixed Acid

The oxygen dissociation curve and Bohr effect were measured in normal whole blood as a function of carboxyhemoglobin concentration [HbCO]. pH was changed by varying CO2 concentration (CO2 Bohr effect) or by addition of isotonic NaOH or HCl at constant PCO2 (fixed acid Bohr effect). As [HbCO] varied through the range of 2, 25, 50, and 75%, P50 was 26.3, 18.0, 11.6, and 6.5 mmHg, respectively. CO2 Bohr effect was highest at low oxygen saturations. This effect did not change as [HbCO] was increased. However, as [HbCO] was increased from 2 to 75%, the fixed acid Bohr factor increased in magnitude from -0.20 to -0.80 at very low oxygen saturations. The effect of molecular CO2 binding (carbamino) on oxygen affinity was eliminated at high [HbCO]. These results are consistent with the initial binding of O2 or CO to thealpha-chain of hemoglobin. The results also suggest that heme-heme interaction is different for oxygen than for carbon monoxide.

Oxygen-linked CO2 transport in sheep blood

1975 ◽  
Vol 229 (2) ◽  
pp. 334-339 ◽  
Author(s):  
R Bauman ◽  
C Bauer ◽  
EA Haller
Keyword(s):  
Whole Blood ◽  
Oxygen Affinity ◽  
Hemoglobin Concentration ◽  
Cell Suspensions ◽  
Bohr Effect ◽  
Carbon Dioxide Exchange ◽  
Red Cell ◽  
Sheep Blood ◽  
Sheep Hemoglobin ◽  
Binding Curves

We have analyzed oxygen-linked carbamate formation in sheep hemoglobin B by measuring a) the effect of CO2 on oxygen affinity and Bohr effect in red cell suspensions and dilute (1.3 mM Hb4) and concentrated (5 mM Hb4) hemoglobin solutions at 37 degrees C and b) CO2 binding curves of deoxygenated and oxygenated whole blood and hemoglobin solutions, respectively, at the same temperature. In the presence of CO2 both the Bohr effect and oxygen affinity were significantly lower in 1.3-mM Hb4 solutions than in either red cell suspensions or 5-mM Hb4 solutions, while in the absence of CO2 Bohr effect and oxygen affinity did not differ significantly in those preparations. Likewise, the fraction of oxygen-linked carbamate obtained from CO2 binding curves was found to be higher in 1.3-mM Hb4 (0.156 M HbCO2/M HbO2) solutions than in 5-mM Hb4 solutions (0.12 M HbCO2/M HbO2) at pH 7.2. We conclude that hemoglobin concentration affects formation of oxygen-linked carbamate. Total oxygen-linked CO2 in sheep whole blood amounted to 0.18 M CO2/M O2 of which 70% is oxygen-linked carbamate. Assuming a respiratory quotient of 0.85, the contribution of oxygen-linked CO2 to carbon dioxide exchange in sheep blood was computed to be 21%.

A Comparison of Diphosphonoglyceric Acid and Diphosphoglyceric Acid as Allosteric Effectors for Hemoglobin

1973 ◽  
Vol 51 (7) ◽  
pp. 1120-1122 ◽  
Author(s):  
Ruth E. Benesch ◽  
Reinhold Benesch ◽  
Suzanna Yung ◽  
Erich Baer ◽  
Ranga Robinson
Keyword(s):  
Binding Site ◽  
Oxygen Affinity ◽  
Glyceric Acid ◽  
Oxygen Release ◽  
Allosteric Effectors ◽  
Oxygen Affinity Of Hemoglobin

2,3-Diphosphoglycerate is the major intraerythrocytic cofactor for oxygen release by hemoglobin. The phosphono analogue, 2,3-diphosphono-DL-glyceric acid, has only minimal effects on the oxygen affinity of hemoglobin. This finding is readily understood in terms of the electrostatic and spatial requirements of the binding site in deoxyhemoglobin.

scholarly journals Sea salt aerosols as a reactive surface for inorganic and organic acidic gases in the Arctic troposphere

2015 ◽  
Vol 15 (19) ◽  
pp. 11341-11353 ◽  
Author(s):  
J. W. Chi ◽  
W. J. Li ◽  
D. Z. Zhang ◽  
J. C. Zhang ◽  
Y. T. Lin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Optical Properties ◽  
Sea Salt ◽  
The Arctic ◽  
Amorphous Coating ◽  
Acidic Gases ◽  
Sea Salt Aerosols ◽  
New Findings ◽  
Arctic Atmosphere ◽  
Inorganic And Organic

Abstract. Sea salt aerosols (SSA) are dominant particles in the Arctic atmosphere and determine the polar radiative balance. SSA react with acidic pollutants that lead to changes in physical and chemical properties of their surface, which in turn alter their hygroscopic and optical properties. Transmission electron microscopy with energy-dispersive X-ray spectrometry was used to analyze morphology, composition, size, and mixing state of individual SSA at Ny-Ålesund, Svalbard, in summertime. Individual fresh SSA contained cubic NaCl coated by certain amounts of MgCl2 and CaSO4. Individual partially aged SSA contained irregular NaCl coated by a mixture of NaNO3, Na2SO4, Mg(NO3)2, and MgSO4. The comparison suggests the hydrophilic MgCl2 coating in fresh SSA likely intrigued the heterogeneous reactions at the beginning of SSA and acidic gases. Individual fully aged SSA normally had Na2SO4 cores and an amorphous coating of NaNO3. Elemental mappings of individual SSA particles revealed that as the particles ageing Cl gradually decreased, the C, N, O, and S content increased. 12C- mapping from nanoscale secondary ion mass spectrometry indicates that organic matter increased in the aged SSA compared with the fresh SSA. 12C- line scan further shows that organic matter was mainly concentrated on the aged SSA surface. These new findings indicate that this mixture of organic matter and NaNO3 on particle surfaces likely determines their hygroscopic and optical properties. These abundant SSA as reactive surfaces adsorbing inorganic and organic acidic gases can shorten acidic gas lifetime and influence the possible gaseous reactions in the Arctic atmosphere, which need to be incorporated into atmospheric chemical models in the Arctic troposphere.

scholarly journals The Bohr/Haldane effect: a model-based uncovering of the full extent of its impact on O2 delivery to and CO2 removal from tissues

2018 ◽  
Vol 125 (3) ◽  
pp. 916-922 ◽  
Author(s):  
Hans Malte ◽  
Gunnar Lykkeboe
Keyword(s):  
Oxygen Affinity ◽  
Model System ◽  
Bohr Effect ◽  
Co2 Removal ◽  
Acid Base ◽  
Oxygen Equilibrium ◽  
Hemoglobin Oxygen Affinity ◽  
Bohr Factor ◽  
O2 Delivery ◽  
Oxygen Equilibrium Curve

For a century, the influence of the Bohr effect on the utilization of blood-borne oxygen has been deemed secondary to its influence on the uptake of carbon dioxide by the blood. Here, we show that the opposite is the case. Using a simple two-ligand, two-state formulation, we modeled the simultaneous oxygen and proton binding to hemoglobin, as well as the resulting acid-base changes of the surrounding solution. Blocking of the Bohr effect in this model system results in a dramatic increase in the oxygen affinity, as expressed by the oxygen partial pressure at half saturation, the P50. It also becomes clear that the P50 and the Bohr factor (a measure of the size of the Bohr effect) are not independent but directly related. Thus, everything else being equal, varying the number of Bohr groups from 0 to 8 per tetramer results in an increase in the Bohr factor from 0 to −0.9 and an increase in P50 from 6 to 46 mmHg at a constant Pco2 of 40 mmHg. Therefore, changes in hemoglobin structure that lead to changes in the Bohr factor will inevitably also change hemoglobin oxygen affinity. NEW & NOTEWORTHY Using a mathematical model, we show that the Bohr effect has a more profound effect on gas exchange than is evident when comparing oxygen equilibrium curves measured in the laboratory at different constant values of Pco2 or pH. Protons preloaded on the Bohr groups, as well as the protons taken up during oxygen unloading, dramatically decrease oxygen affinity of the physiological oxygen equilibrium curve. Therefore, the Bohr effect is instrumental in setting the oxygen affinity.

scholarly journals Allosteric Modulators for GPCRs as a Therapeutic Alternative with High Potential in Drug Discovery

2020 ◽  
Author(s):  
Arfaxad Reyes-Alcaraz ◽  
Emilio Y. Lucero Garcia-Rojas ◽  
Richard A. Bond ◽  
Bradley K. McConnell
Keyword(s):  
Drug Discovery ◽  
Signaling Pathways ◽  
Therapeutic Benefit ◽  
High Potential ◽  
Screening Methods ◽  
Allosteric Modulators ◽  
Endogenous Ligand ◽  
New Findings ◽  
Multiple Signaling ◽  
G Protein Coupled

The superfamily of G protein-coupled receptors (GPCRs) consists of biological microprocessors that can activate multiple signaling pathways. Most GPCRs have an orthosteric pocket where the endogenous ligand(s) typically binds. Conversely, allosteric ligands bind to GPCRs at sites that are distinct from the orthosteric binding region and they modulate the response elicited by the endogenous ligand. Allosteric ligands can also switch the response of a GPCR after ligand binding to a unique signaling pathway, these ligands are termed biased allosteric modulators. Thus, the development of allosteric ligands opens new and multiple ways in which the signaling pathways of GPCRs can be manipulated for potential therapeutic benefit. Furthermore, the mechanisms by which allosteric ligands modulate the effects of endogenous ligands have provided new insights into the interactions between allosteric ligands and GPCRs. These new findings have a high potential to improve drug discovery and development and, therefore, creating the need for better screening methods for allosteric drugs to increase the chances of success in the development of allosteric modulators as lead clinical compounds.

The Bohr effect related to blood and erythrocyte pH

1963 ◽  
Vol 205 (2) ◽  
pp. 337-340 ◽  
Author(s):  
Peter Hilpert ◽  
Renate Gislinde Fleischmann ◽  
Doris Kempe ◽  
Heinz Bartels
Keyword(s):  
Oxygen Pressure ◽  
Ph Value ◽  
Oxygen Affinity ◽  
Bohr Effect ◽  
Red Cell ◽  
Oxygen Dissociation Curve ◽  
Dissociation Curve ◽  
Oxygen Dissociation ◽  
Constant Cell ◽  
The Right

The Bohr effect of the blood and the red cell hemolysates of adult and newborn humans, goats and kids, and sheep and lambs were determined and the physiological significance is discussed. Similar determinations were made on blood from an African elephant, yak, camel, Dybowski deer, and llama. The strong displacement to the right of the oxygen dissociation curve which occurs in kids and lambs during the first 5 days of life can be largely explained by a change in the pH value within the erythrocytes. When the oxygen affinity is expressed by the oxygen pressure necessary for half saturation (T50) at a constant cell pH, considerable differences exist between species.

scholarly journals SULFHYDRYL GROUPS AND THE STRUCTURE OF HEMOGLOBIN

1956 ◽  
Vol 39 (4) ◽  
pp. 585-605 ◽  
Author(s):  
Austen F. Riggs ◽  
Robert A. Wolbach
Keyword(s):  
Mercuric Chloride ◽  
Methyl Mercury ◽  
Oxygen Affinity ◽  
Sulfhydryl Groups ◽  
Bohr Effect ◽  
Sh Groups ◽  
Protein Architecture ◽  
Mechanism Of Interaction

1. Addition of 2 moles of mersalyl, mercuric chloride, p-chloromercuribenzoate (PCMB), or methyl mercury hydroxide per mole of hemoglobin greatly reduces heme-heme interactions (n), yet these substances have quite different effects on the oxygen affinity (-log p50). Mersalyl and mercuric chloride at this concentration each increase the oxygen affinity, while PCMB and methyl mercury have little or no effect on the oxygen affinity. These effects are primarily associated with the binding of —SH groups, and are largely reversed on the addition of glutathione. —SH groups do not appear to be responsible for the Bohr effect. 2. Evidence is presented for the belief that the two hemes of each half-molecule of horse hemoglobin are situated on either side of a cluster of—SH groups. 3. The mechanism of interaction between the hemes is discussed. It is concluded that the reorganization of the protein architecture which accompanies oxygenation plays a central role in this interaction, in agreement with the views of Pauling and Wyman.

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