The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform
Gregory J Kato - One of the best experts on this subject based on the ideXlab platform.
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therapeutic strategies to alter the Oxygen Affinity of sickle hemoglobin
Hematology-oncology Clinics of North America, 2014Co-Authors: Martin K Safo, Gregory J KatoAbstract:The fundamental pathophysiology of sickle cell disease involves the polymerization of sickle hemoglobin in its T-state which develops under low Oxygen saturation. One therapeutic strategy is to develop pharmacologic agents to stabilize the R-state of hemoglobin, which has higher Oxygen Affinity and would be expected to have slower kinetics of polymerization, potentially delaying the sickling of red cells during circulation. This therapeutic strategy has stimulated the laboratory investigation of aromatic aldehydes, aspirin derivatives, thiols and isothiocyanates that can stabilize the R-state of hemoglobin in vitro. One representative aromatic aldehyde agent, 5-hydoxymethyl-2-furfural (5-HMF, also known as Aes-103) increases Oxygen Affinity of sickle hemoglobin and reduces hypoxia-induced sickling in vitro and protects sickle cell mice from effects of hypoxia. It has completed pre-clinical testing and has entered clinical trials. The development of Hb allosteric modifiers as direct anti-sickling agents is an attractive investigational goal for the treatment of sickle cell disease.
Ethan Schonbrun - One of the best experts on this subject based on the ideXlab platform.
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single cell measurement of red blood cell Oxygen Affinity
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Giuseppe Di Caprio, Chris Stokes, John M Higgins, Ethan SchonbrunAbstract:Oxygen is transported throughout the body by hemoglobin (Hb) in red blood cells (RBCs). Although the Oxygen Affinity of blood is well-understood and routinely assessed in patients by pulse oximetry, variability at the single-cell level has not been previously measured. In contrast, single-cell measurements of RBC volume and Hb concentration are taken millions of times per day by clinical hematology analyzers, and they are important factors in determining the health of the hematologic system. To better understand the variability and determinants of Oxygen Affinity on a cellular level, we have developed a system that quantifies the Oxygen saturation, cell volume, and Hb concentration for individual RBCs in high throughput. We find that the variability in single-cell saturation peaks at an Oxygen partial pressure of 2.9%, which corresponds to the maximum slope of the Oxygen–Hb dissociation curve. In addition, single-cell Oxygen Affinity is positively correlated with Hb concentration but independent of osmolarity, which suggests variation in the Hb to 2,3-diphosphoglycerate (2–3 DPG) ratio on a cellular level. By quantifying the functional behavior of a cellular population, our system adds a dimension to blood cell analysis and other measurements of single-cell variability.
Andrea Mozzarelli - One of the best experts on this subject based on the ideXlab platform.
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identification of a small molecule that increases hemoglobin Oxygen Affinity and reduces ss erythrocyte sickling
ACS Chemical Biology, 2014Co-Authors: Akito Nakagawa, Andrea Mozzarelli, Dina Wassaf, Revital Yefidofffreedman, Dominick E Casalena, Michelle Palmer, Jacqueline Meadows, Luca Ronda, Osheiza Abdulmalik, Kenneth D BlochAbstract:Small molecules that increase the Oxygen Affinity of human hemoglobin may reduce sickling of red blood cells in patients with sickle cell disease. We screened 38 700 compounds using small molecule microarrays and identified 427 molecules that bind to hemoglobin. We developed a high-throughput assay for evaluating the ability of the 427 small molecules to modulate the Oxygen Affinity of hemoglobin. We identified a novel allosteric effector of hemoglobin, di(5-(2,3-dihydro-1,4-benzodioxin-2-yl)-4H-1,2,4-triazol-3-yl)disulfide (TD-1). TD-1 induced a greater increase in Oxygen Affinity of human hemoglobin in solution and in red blood cells than did 5-hydroxymethyl-2-furfural (5-HMF), N-ethylmaleimide (NEM), or diformamidine disulfide. The three-dimensional structure of hemoglobin complexed with TD-1 revealed that monomeric units of TD-1 bound covalently to β-Cys93 and β-Cys112, as well as noncovalently to the central water cavity of the hemoglobin tetramer. The binding of TD-1 to hemoglobin stabilized the rel...
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high and low Oxygen Affinity conformations of t state hemoglobin
Protein Science, 2008Co-Authors: Stefano Bruno, Maria Bonaccio, Stefano Bettati, Claudio Rivetti, Cristiano Viappiani, Stefania Abbruzzetti, Andrea MozzarelliAbstract:To understand the interplay between tertiary and quaternary transitions associated with hemoglobin function and regulation, Oxygen binding curves were obtained for hemoglobin A fixed in the T quaternary state by encapsulation in wet porous silica gels. At pH 7.0 and 15°C, the Oxygen pressure at half saturation (p50) was measured to be 12.4 ± 0.2 and 139 ± 4 torr for hemoglobin gels prepared in the absence and presence of the strong allosteric effectors inositol hexaphosphate and bezafibrate, respectively. Both values are in excellent agreement with those found for the binding of the first Oxygen to hemoglobin in solution under similar experimental conditions. The corresponding Hill coefficients of hemoglobin gels were 0.94 ± 0.02 and 0.93 ± 0.03, indicating, in the frame of the Monod, Wyman, and Changeux model, that high and low Oxygen-Affinity tertiary T-state conformations have been isolated in a pure form. The values, slightly lower than unity, reflect the different Oxygen Affinity of α- and β-hemes. Significantly, hemoglobin encapsulated in the presence of the weak effector phosphate led to gels that show intermediate Oxygen Affinity and Hill coefficients of 0.7 to 0.8. The heterogeneous Oxygen binding results from the presence of a mixture of the high and low Oxygen-Affinity T states. The Bohr effect was measured for hemoglobin gels containing the pure conformations and found to be more pronounced for the high-Affinity T state and almost absent for the low-Affinity T state. These findings indicate that the functional properties of the T quaternary state result from the contribution of two distinct, interconverting conformations, characterized by a 10-fold difference in Oxygen Affinity and a different extent of tertiary Bohr effect. The very small degree of T-state cooperativity observed in solution and in the crystalline state might arise from a ligand-induced perturbation of the distribution between the high- and low-Affinity T-state conformations.
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allosteric effectors do not alter the Oxygen Affinity of hemoglobin crystals
Protein Science, 2008Co-Authors: Andrea Mozzarelli, Claudio Rivetti, G L Rossi, William A Eaton, Eric R HenryAbstract:In solution, the Oxygen Affinity of hemoglobin in the T quaternary structure is decreased in the presence of allosteric effectors such as protons and organic phosphates. To explain these effects, as well as the absence of the Bohr effect and the lower Oxygen Affinity of T-state hemoglobin in the crystal compared to solution, Rivetti C et al. (1993a, Biochemistry 32:2888-2906) suggested that there are high- and low-Affinity subunit conformations of T, associated with broken and unbroken intersubunit salt bridges. In this model, the crystal of T-state hemoglobin has the lowest possible Oxygen Affinity because the salt bridges remain intact upon Oxygenation. Binding of allosteric effectors in the crystal should therefore not influence the Oxygen Affinity. To test this hypothesis, we used polarized absorption spectroscopy to measure Oxygen binding curves of single crystals of hemoglobin in the T quaternary structure in the presence of the "strong" allosteric effectors, inositol hexaphosphate and bezafibrate. In solution, these effectors reduce the Oxygen Affinity of the T state by 10-30-fold. We find no change in Affinity (< 10%) of the crystal. The crystal binding curve, moreover, is noncooperative, which is consistent with the essential feature of the two-state allosteric model of Monod J, Wyman J, and Changeux JP (1965, J Mol Biol 12:88-118) that cooperative binding requires a change in quaternary structure. Noncooperative binding by the crystal is not caused by cooperative interactions being masked by fortuitous compensation from a difference in the Affinity of the alpha and beta subunits. This was shown by calculating the separate alpha and beta subunit binding curves from the two sets of polarized optical spectra using geometric factors from the X-ray structures of deOxygenated and fully Oxygenated T-state molecules determined by Paoli M et al. (1996, J Mol Biol 256:775-792).
Martin K Safo - One of the best experts on this subject based on the ideXlab platform.
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therapeutic strategies to alter the Oxygen Affinity of sickle hemoglobin
Hematology-oncology Clinics of North America, 2014Co-Authors: Martin K Safo, Gregory J KatoAbstract:The fundamental pathophysiology of sickle cell disease involves the polymerization of sickle hemoglobin in its T-state which develops under low Oxygen saturation. One therapeutic strategy is to develop pharmacologic agents to stabilize the R-state of hemoglobin, which has higher Oxygen Affinity and would be expected to have slower kinetics of polymerization, potentially delaying the sickling of red cells during circulation. This therapeutic strategy has stimulated the laboratory investigation of aromatic aldehydes, aspirin derivatives, thiols and isothiocyanates that can stabilize the R-state of hemoglobin in vitro. One representative aromatic aldehyde agent, 5-hydoxymethyl-2-furfural (5-HMF, also known as Aes-103) increases Oxygen Affinity of sickle hemoglobin and reduces hypoxia-induced sickling in vitro and protects sickle cell mice from effects of hypoxia. It has completed pre-clinical testing and has entered clinical trials. The development of Hb allosteric modifiers as direct anti-sickling agents is an attractive investigational goal for the treatment of sickle cell disease.
Griffin P Rodgers - One of the best experts on this subject based on the ideXlab platform.
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inhaled nitric oxide augments nitric oxide transport on sickle cell hemoglobin without affecting Oxygen Affinity
Journal of Clinical Investigation, 1999Co-Authors: Mark T Gladwin, Alan N Schechter, James H Shelhamer, Lewis K Pannell, Deirdre A Conway, Borys W Hrinczenko, James S Nichols, Margaret E Peasefye, Constance Tom Noguchi, Griffin P RodgersAbstract:Nitric oxide (NO) inhalation has been reported to increase the Oxygen Affinity of sickle cell erythrocytes. Also, proposed allosteric mechanisms for hemoglobin, based on S-nitrosation of β-chain cysteine 93, raise the possibilty of altering the pathophysiology of sickle cell disease by inhibiting polymerization or by increasing NO delivery to the tissue. We studied the effects of a 2-hour treatment, using varying concentrations of inhaled NO. Oxygen Affinity, as measured by P50, did not respond to inhaled NO, either in controls or in individuals with sickle cell disease. At baseline, the arterial and venous levels of nitrosylated hemoglobin were not significantly different, but NO inhalation led to a dose-dependent increase in mean nitrosylated hemoglobin, and at the highest dosage, a significant arterial-venous difference emerged. The levels of nitrosylated hemoglobin are too low to affect overall hemoglobin Oxygen Affinity, but augmented NO transport to the microvasculature seems a promising strategy for improving microvascular perfusion.
