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Robert M. Garrels - One of the best experts on this subject based on the ideXlab platform.
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Calculated aqueous-solution-solid-solution relations in the low-temperature system CaO-MgO-FeO-CO2-H2O
Geochimica et Cosmochimica Acta, 1992Co-Authors: Terri L. Woods, Robert M. GarrelsAbstract:Abstract A method of estimating an aqueous-solution composition from that of solid-solutions believed to be in equilibrium with it is derived. The low-temperature ternary Ca-Fe-Mg phase relations of the rhombohedral carbonates are investigated using this method, and their phase diagrams at 25 and 150°C are calculated. Algebraic manipulations of equilibrium constant equations representing dissolution of the carbonates yield equations for the phase boundaries separating calcite from an ankerite-dolomite solid-solution and an ankerite-dolomite solid-solution from a siderite-magnesite solid-solution. A value for the free energy of formation of ankerite is estimated (−1818.0 ± 0.8 kJ/mol, 25°C) from compositions of natural coexisting carbonates. Necessary compositional information for the carbonates was derived from the relatively unmetamorphosed Early Proterozoic Marra Mamba Banded Iron-Formation of the Hamersley Basin of Western Australia. The method yielded information on the a Fe 2+ a ca 2+ and a Mg 2+ a ca 2+ ratios of the solutions that deposited the carbonates of the Marra Mamba. The method suggests a depositing solution for the carbonates of the Lower Marra Mamba Iron-Formation significantly richer in iron than was likely to have been the case for Early Proterozoic seawater.
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Calculated aqueous-solution-solid-solution relations in the low-temperature system CaO-MgO-FeO-CO2-H2O
Geochimica et Cosmochimica Acta, 1992Co-Authors: Terri L. Woods, Robert M. GarrelsAbstract:Abstract A method of estimating an aqueous-solution composition from that of solid-solutions believed to be in equilibrium with it is derived. The low-temperature ternary Ca-Fe-Mg phase relations of the rhombohedral carbonates are investigated using this method, and their phase diagrams at 25 and 150°C are calculated. Algebraic manipulations of equilibrium constant equations representing dissolution of the carbonates yield equations for the phase boundaries separating calcite from an ankerite-dolomite solid-solution and an ankerite-dolomite solid-solution from a siderite-magnesite solid-solution. A value for the free energy of formation of ankerite is estimated (−1818.0 ± 0.8 kJ/mol, 25°C) from compositions of natural coexisting carbonates. Necessary compositional information for the carbonates was derived from the relatively unmetamorphosed Early Proterozoic Marra Mamba Banded Iron-Formation of the Hamersley Basin of Western Australia. The method yielded information on the a Fe 2+ a ca 2+ and a Mg 2+ a ca 2+ ratios of the solutions that deposited the carbonates of the Marra Mamba. The method suggests a depositing solution for the carbonates of the Lower Marra Mamba Iron-Formation significantly richer in iron than was likely to have been the case for Early Proterozoic seawater.
Terri L. Woods - One of the best experts on this subject based on the ideXlab platform.
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Calculated aqueous-solution-solid-solution relations in the low-temperature system CaO-MgO-FeO-CO2-H2O
Geochimica et Cosmochimica Acta, 1992Co-Authors: Terri L. Woods, Robert M. GarrelsAbstract:Abstract A method of estimating an aqueous-solution composition from that of solid-solutions believed to be in equilibrium with it is derived. The low-temperature ternary Ca-Fe-Mg phase relations of the rhombohedral carbonates are investigated using this method, and their phase diagrams at 25 and 150°C are calculated. Algebraic manipulations of equilibrium constant equations representing dissolution of the carbonates yield equations for the phase boundaries separating calcite from an ankerite-dolomite solid-solution and an ankerite-dolomite solid-solution from a siderite-magnesite solid-solution. A value for the free energy of formation of ankerite is estimated (−1818.0 ± 0.8 kJ/mol, 25°C) from compositions of natural coexisting carbonates. Necessary compositional information for the carbonates was derived from the relatively unmetamorphosed Early Proterozoic Marra Mamba Banded Iron-Formation of the Hamersley Basin of Western Australia. The method yielded information on the a Fe 2+ a ca 2+ and a Mg 2+ a ca 2+ ratios of the solutions that deposited the carbonates of the Marra Mamba. The method suggests a depositing solution for the carbonates of the Lower Marra Mamba Iron-Formation significantly richer in iron than was likely to have been the case for Early Proterozoic seawater.
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Calculated aqueous-solution-solid-solution relations in the low-temperature system CaO-MgO-FeO-CO2-H2O
Geochimica et Cosmochimica Acta, 1992Co-Authors: Terri L. Woods, Robert M. GarrelsAbstract:Abstract A method of estimating an aqueous-solution composition from that of solid-solutions believed to be in equilibrium with it is derived. The low-temperature ternary Ca-Fe-Mg phase relations of the rhombohedral carbonates are investigated using this method, and their phase diagrams at 25 and 150°C are calculated. Algebraic manipulations of equilibrium constant equations representing dissolution of the carbonates yield equations for the phase boundaries separating calcite from an ankerite-dolomite solid-solution and an ankerite-dolomite solid-solution from a siderite-magnesite solid-solution. A value for the free energy of formation of ankerite is estimated (−1818.0 ± 0.8 kJ/mol, 25°C) from compositions of natural coexisting carbonates. Necessary compositional information for the carbonates was derived from the relatively unmetamorphosed Early Proterozoic Marra Mamba Banded Iron-Formation of the Hamersley Basin of Western Australia. The method yielded information on the a Fe 2+ a ca 2+ and a Mg 2+ a ca 2+ ratios of the solutions that deposited the carbonates of the Marra Mamba. The method suggests a depositing solution for the carbonates of the Lower Marra Mamba Iron-Formation significantly richer in iron than was likely to have been the case for Early Proterozoic seawater.
Qi Guan - One of the best experts on this subject based on the ideXlab platform.
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Mineral chemistry and crystallization conditions of the Late Cretaceous Mamba pluton from the eastern Gangdese, Southern Tibetan Plateau
Journal of Earth Science, 2016Co-Authors: Mark Scheltens, Qi GuanAbstract:The Late Cretaceous Mamba granodiorite belongs to a part of the Mesozoic Gangdese continental magmatic belt. No quantitative mineralogical study has been made hitherto, and hence the depth at which it formed is poorly constrained. Here we present mineralogical data for the Mamba pluton, including host rocks and their mafic microgranular enclaves (MMEs), to provide insights into their overall crystallization conditions and information about magma mixing. All amphiboles in the Mamba pluton are calcic, with B(Ca+Na)>1.5, and Si=6.81–7.42 apfu for the host rocks and Si=6.77–7.35 apfu for the MMEs. The paramount cation substitutions in amphibole include edenite type and tschermakite type. Biotites both in the host rocks and the MMEs collectively have high MgO (13.19 wt.%–13.03 wt.%) contents, but define a narrow range of Al apfu (atoms per formula unit) variations (2.44–2.57). The oxygen fugacity estimates are based on the biotite compositions cluster around the NNO buffer. The calculated pressure ranges from 1.2 to 2.1 kbar according to the aluminum-in-hornblende barometer. The computed pressure varies from 0.9 to 1.3 kbar based on the aluminum-in-biotite barometer which corresponds to an average depth of ca. 3.9 km. Besides, the estimates of crystallization pressures vary from 0.8 to 1.4 kbar based on the amphibole barometer proposed by Ridolfi et al. (2010), which can be equivalent to the depths ranging from 3.1 to 5.2 km. The MMEs have plagioclase oscillatory zonings and quartz aggregates, probably indicating the presence of magma mixing. Besides, core-to-rim element variations (Rb, Sr, Ba, and P) for the K-feldspar megacrysts serve as robust evidence to support magma mixing and crystal fractionation. This indicates the significance of the magma mixing that contributes to the formation of K-feldspar megacryst zonings in the Mamba pluton.
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Mineral chemistry and crystallization conditions of the Late Cretaceous Mamba pluton from the eastern Gangdese, Southern Tibetan Plateau
JOURNAL OF EARTH SCIENCE, 2016Co-Authors: Li Xiaowei, Mo Xuanxue, Scheltens Mark, Qi GuanAbstract:The Late Cretaceous Mamba granodiorite belongs to a part of the Mesozoic Gangdese continental magmatic belt. No quantitative mineralogical study has been made hitherto, and hence the depth at which it formed is poorly constrained. Here we present mineralogical data for the Mamba pluton, including host rocks and their mafic microgranular enclaves (MMEs), to provide insights into their overall crystallization conditions and information about magma mixing. All amphiboles in the Mamba pluton are calcic, with (B)(Ca+Na)> 1.5, and Si=6.81-7.42 apfu for the host rocks and Si=6.77-7.35 apfu for the MMEs. The paramount cation substitutions in amphibole include edenite type and tschermakite type. Biotites both in the host rocks and the MMEs collectively have high MgO (13.19 wt.%-13.03 wt.%) contents, but define a narrow range of Al apfu (atoms per formula unit) variations (2.44-2.57). The oxygen fugacity estimates are based on the biotite compositions cluster around the NNO buffer. The calculated pressure ranges from 1.2 to 2.1 kbar according to the aluminum-in-hornblende barometer. The computed pressure varies from 0.9 to 1.3 kbar based on the aluminum-in-biotite barometer which corresponds to an average depth of ca. 3.9 km. Besides, the estimates of crystallization pressures vary from 0.8 to 1.4 kbar based on the amphibole barometer proposed by Ridolfi et al. (2010), which can be equivalent to the depths ranging from 3.1 to 5.2 km. The MMEs have plagioclase oscillatory zonings and quartz aggregates, probably indicating the presence of magma mixing. Besides, core-to-rim element variations (Rb, Sr, Ba, and P) for the K-feldspar megacrysts serve as robust evidence to support magma mixing and crystal fractionation. This indicates the significance of the magma mixing that contributes to the formation of K-feldspar megacryst zonings in the Mamba pluton.We greatly appreciate comments provided by reviewers of the early versions of this manuscript, as well as the kind help of the editors. This study was jointly funded by the National Natural Science Foundation of China; the China Postdoctoral Science Foundation; China University of Geosciences; the Fundamental Research Funds for the Central Universities of China (No.2652015018). We appreciate Guiming Shu, Tingting Shen, Yi Sun and Xiangkun Ge for their kind assistance with elemental analyses. We also thank Zhidan Zhao, Dicheng Zhu, Feng Yu, Min Liu, Wenting Zhao, Liangliang Zhang and Yu HuSCI(E)中国科学引文数据库(CSCD)ARTICLEvividlixiaowei@163.com; moxx@cugb.edu.cn4545-5702
Droctove Laura - One of the best experts on this subject based on the ideXlab platform.
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First vasopressin type 2 receptor antagonist Kunitz toxins : pharmacodynamics study and structure-activity relationships
2018Co-Authors: Droctove LauraAbstract:La Mambaquarétine-1 (MQ-1), une toxine du Mamba vert, est le tout premier peptide Kunitz à bloquer sélectivement l’activité du récepteur de type 2 à la vasopressine (V2R). Celui-ci contrôle la concentration finale des urines dans le rein. Impliqué dans plusieurs pathologies, son inhibition est actuellement considérée comme la meilleure stratégie thérapeutique dans le traitement de la polykystose rénale, une maladie génétique héréditaire. L’étude pharmacodynamique de MQ-1 sur des rats sains a confirmé son activité in vivo qui se traduit par un effet aquarétique dépendant de la dose. L’effet maximum est atteint 2 heures après injection intrapéritonéale et disparait avec un temps de demi-vie biologique variant de 1 à 4 heures selon la dose. L’administration quotidienne d’une faible dose a montré une accumulation de l’effet les trois premiers jours, avant un plateau, suggérant une activité résiduelle au-delà de 24 heures. Le criblage des trois autres venins de Mambas ainsi qu’une analyse comparée des séquences peptidiques les plus proches dans les bases de données ont révélé l’existence d’un groupe phylogénétique de onze toxines Kunitz antagonistes de V2R. Une approche innovante, combinant tests de liaison de variants de MQ-1 et modélisation du complexe MQ-1-V2R, a permis de décrypter une partie du pharmacophore de la toxine. Les deux partenaires partagent une importante complémentarité ionique impliquant plusieurs boucles extracellulaires du récepteur, et une région hydrophobe de MQ-1 interagit au cœur de V2R à proximité de son site orthostérique supposé. Enfin, une première collaboration avec une industrie pharmaceutique a mis en évidence les points critiques à approfondir pour aboutir au développement thérapeutique de MQ-1.Mambaquaretin-1 (MQ-1), a green Mamba toxin, is the very first Kunitz peptide to selectively hinder the vasopressin type 2 receptor (V2R) activation. This receptor controls the final concentration of urine in kidneys. Involved in a number of pathologies, its inhibition is currently considered as the best therapeutic strategy in the treatment of polycystic kidney disease, a hereditary genetic disease. Pharmacodynamic study of MQ-1 carried out on healthy rats confirmed its in vivo activity which consists in inducing a dose-dependent aquaretic effect. Maximum effect is reached 2 hours after an intraperitoneal injection and disappears in a biological half-life ranging from 1 to 4 hours according to the dose. The daily injection of small quantities pointed to a cumulative effect over the first three days, leading to a plateau, which suggests a residual activity exceeding 24 hours. The screening of the three other Mamba venoms along with a comparative analysis of the closest peptide sequences reported in databases revealed the existence of a phylogenetic group of eleven V2R antagonist Kunitz toxins. An innovative approach combining binding assays on MQ-1 variants and the modelling of the MQ-1-V2R complex has led to a partial deciphering of the pharmacophore of the toxin. The two partners share a significant ionic complementarity involving a number of extracellular loops of the receptor, and a hydrophobic region of MQ-1 interacts within V2R in the vicinity of its supposed orthosteric site. Lastly, a collaboration initiated with a pharmaceutical company brought out the need for the closer scrutiny of some crucial points to succeed in a therapeutic development of MQ-1
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Premières toxines Kunitz antagonistes du récepteur de type 2 à la vasopressine : étude pharmacodynamique et relations structure-activité
HAL CCSD, 2018Co-Authors: Droctove LauraAbstract:Mambaquaretin-1 (MQ-1), a green Mamba toxin, is the very first Kunitz peptide to selectively hinder the vasopressin type 2 receptor (V2R) activation. This receptor controls the final concentration of urine in kidneys. Involved in a number of pathologies, its inhibition is currently considered as the best therapeutic strategy in the treatment of polycystic kidney disease, a hereditary genetic disease. Pharmacodynamic study of MQ-1 carried out on healthy rats confirmed its in vivo activity which consists in inducing a dose-dependent aquaretic effect. Maximum effect is reached 2 hours after an intraperitoneal injection and disappears in a biological half-life ranging from 1 to 4 hours according to the dose. The daily injection of small quantities pointed to a cumulative effect over the first three days, leading to a plateau, which suggests a residual activity exceeding 24 hours. The screening of the three other Mamba venoms along with a comparative analysis of the closest peptide sequences reported in databases revealed the existence of a phylogenetic group of eleven V2R antagonist Kunitz toxins. An innovative approach combining binding assays on MQ-1 variants and the modelling of the MQ-1-V2R complex has led to a partial deciphering of the pharmacophore of the toxin. The two partners share a significant ionic complementarity involving a number of extracellular loops of the receptor, and a hydrophobic region of MQ-1 interacts within V2R in the vicinity of its supposed orthosteric site. Lastly, a collaboration initiated with a pharmaceutical company brought out the need for the closer scrutiny of some crucial points to succeed in a therapeutic development of MQ-1.La Mambaquarétine-1 (MQ-1), une toxine du Mamba vert, est le tout premier peptide Kunitz à bloquer sélectivement l’activité du récepteur de type 2 à la vasopressine (V2R). Celui-ci contrôle la concentration finale des urines dans le rein. Impliqué dans plusieurs pathologies, son inhibition est actuellement considérée comme la meilleure stratégie thérapeutique dans le traitement de la polykystose rénale, une maladie génétique héréditaire. L’étude pharmacodynamique de MQ-1 sur des rats sains a confirmé son activité in vivo qui se traduit par un effet aquarétique dépendant de la dose. L’effet maximum est atteint 2 heures après injection intrapéritonéale et disparait avec un temps de demi-vie biologique variant de 1 à 4 heures selon la dose. L’administration quotidienne d’une faible dose a montré une accumulation de l’effet les trois premiers jours, avant un plateau, suggérant une activité résiduelle au-delà de 24 heures. Le criblage des trois autres venins de Mambas ainsi qu’une analyse comparée des séquences peptidiques les plus proches dans les bases de données ont révélé l’existence d’un groupe phylogénétique de onze toxines Kunitz antagonistes de V2R. Une approche innovante, combinant tests de liaison de variants de MQ-1 et modélisation du complexe MQ-1-V2R, a permis de décrypter une partie du pharmacophore de la toxine. Les deux partenaires partagent une importante complémentarité ionique impliquant plusieurs boucles extracellulaires du récepteur, et une région hydrophobe de MQ-1 interagit au cœur de V2R à proximité de son site orthostérique supposé. Enfin, une première collaboration avec une industrie pharmaceutique a mis en évidence les points critiques à approfondir pour aboutir au développement thérapeutique de MQ-1
Alice M. Luther - One of the best experts on this subject based on the ideXlab platform.
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In vivo neutralization of dendrotoxin-mediated neurotoxicity of black Mamba venom by oligoclonal human IgG antibodies
Nature Communications, 2018Co-Authors: Andreas H. Laustsen, Aneesh Karatt-vellatt, Edward W. Masters, Ana Silvia Arias, Cecilie Knudsen, Saioa Oscoz, Peter Slavny, Daniel T. Griffiths, Alice M. Luther, Rachael A. LeahAbstract:Current anti-venoms against black Mamba ( Dendroaspis polylepis ) bites are animal-derived and associated with several limitations. Here, Laustsen and colleagues develop an experimental recombinant anti-venom based on oligoclonal human IgG antibodies and establish its potential protective value in neutralizing dendrotoxin-mediated neurotoxicity using venom challenge in vivo models. The black Mamba ( Dendroaspis polylepis ) is one of the most feared snake species of the African savanna. It has a potent, fast-acting neurotoxic venom comprised of dendrotoxins and α-neurotoxins associated with high fatality in untreated victims. Current antivenoms are both scarce on the African continent and present a number of drawbacks as they are derived from the plasma of hyper-immunized large mammals. Here, we describe the development of an experimental recombinant antivenom by a combined toxicovenomics and phage display approach. The recombinant antivenom is based on a cocktail of fully human immunoglobulin G (IgG) monoclonal antibodies capable of neutralizing dendrotoxin-mediated neurotoxicity of black Mamba whole venom in a rodent model. Our results show the potential use of fully human monoclonal IgGs against animal toxins and the first use of oligoclonal human IgG mixtures against experimental snakebite envenoming.
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In vivo neutralization of dendrotoxin-mediated neurotoxicity of black Mamba venom by oligoclonal human IgG antibodies.
Nature communications, 2018Co-Authors: Andreas H. Laustsen, Aneesh Karatt-vellatt, Edward W. Masters, Ana Silvia Arias, Cecilie Knudsen, Saioa Oscoz, Peter Slavny, Daniel T. Griffiths, Urska Pus, Alice M. LutherAbstract:The black Mamba (Dendroaspis polylepis) is one of the most feared snake species of the African savanna. It has a potent, fast-acting neurotoxic venom comprised of dendrotoxins and α-neurotoxins associated with high fatality in untreated victims. Current antivenoms are both scarce on the African continent and present a number of drawbacks as they are derived from the plasma of hyper-immunized large mammals. Here, we describe the development of an experimental recombinant antivenom by a combined toxicovenomics and phage display approach. The recombinant antivenom is based on a cocktail of fully human immunoglobulin G (IgG) monoclonal antibodies capable of neutralizing dendrotoxin-mediated neurotoxicity of black Mamba whole venom in a rodent model. Our results show the potential use of fully human monoclonal IgGs against animal toxins and the first use of oligoclonal human IgG mixtures against experimental snakebite envenoming.
