The Experts below are selected from a list of 3249 Experts worldwide ranked by ideXlab platform
Herbert L. Bonkovsky - One of the best experts on this subject based on the ideXlab platform.
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porphyrin and heme metabolism and the porphyrias
Comprehensive Physiology, 2013Co-Authors: Herbert L. Bonkovsky, Tarun Narang, Ting Li, Manish ThaparAbstract:Porphyrins and Metalloporphyrins are the key pigments of life on earth as we know it, because they include chlorophyll (a magnesium-containing Metalloporphyrin) and heme (iron protoporphyrin). In eukaryotes, porphyrins and heme are synthesized by a multistep pathway that involves eight enzymes. The first and rate-controlling step is the formation of delta-aminolevulinic acid (ALA) from glycine plus succinyl CoA, catalyzed by ALA synthase. Intermediate steps occur in the cytoplasm, with formation of the monopyrrole porphobilinogen and the tetrapyrroles hydroxymethylbilane and a series of porphyrinogens, which are serially decarboxylated. Heme is utilized chiefly for the formation of hemoglobin in erythrocytes, myoglobin in muscle cells, cytochromes P-450 and mitochondrial cytochromes, and other hemoproteins in hepatocytes. The rate-controlling step of heme breakdown is catalyzed by heme oxygenase (HMOX), of which there are two isoforms, called HMOX1 and HMOX2. HMOX breaks down heme to form biliverdin, carbon monoxide, and iron. The porphyrias are a group of disorders, mainly inherited, in which there are defects in normal porphyrin and heme synthesis. The cardinal clinical features are cutaneous (due to the skin-damaging effects of excess deposited porphyrins) or neurovisceral attacks of pain, sometimes with weakness, delirium, seizures, and the like (probably due mainly to neurotoxic effects of ALA). The treatment of choice for the acute hepatic porphyrias is intravenous heme therapy, which repletes a critical regulatory heme pool in hepatocytes and leads to downregulation of hepatic ALA synthase, which is a biochemical hallmark of all forms of acute porphyria in relapse. © 2013 American Physiological Society. Compr Physiol 3:365-401, 2013.
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porphyrin and heme metabolism and the porphyrias
Comprehensive Physiology, 2013Co-Authors: Herbert L. Bonkovsky, Tarun Narang, Juntao Guo, Weihong Hou, Manish ThaparAbstract:Porphyrins and Metalloporphyrins are the key pigments of life on earth as we know it, because they include chlorophyll (a magnesium-containing Metalloporphyrin) and heme (iron protoporphyrin). In eukaryotes, porphyrins and heme are synthesized by a multistep pathway that involves eight enzymes. The first and rate-controlling step is the formation of delta-aminolevulinic acid (ALA) from glycine plus succinyl CoA, catalyzed by ALA synthase. Intermediate steps occur in the cytoplasm, with formation of the monopyrrole porphobilinogen and the tetrapyrroles hydroxymethylbilane and a series of porphyrinogens, which are serially decarboxylated. Heme is utilized chiefly for the formation of hemoglobin in erythrocytes, myoglobin in muscle cells, cytochromes P-450 and mitochondrial cytochromes, and other hemoproteins in hepatocytes. The rate-controlling step of heme breakdown is catalyzed by heme oxygenase (HMOX), of which there are two isoforms, called HMOX1 and HMOX2. HMOX breaks down heme to form biliverdin, carbon monoxide, and iron. The porphyrias are a group of disorders, mainly inherited, in which there are defects in normal porphyrin and heme synthesis. The cardinal clinical features are cutaneous (due to the skin-damaging effects of excess deposited porphyrins) or neurovisceral attacks of pain, sometimes with weakness, delirium, seizures, and the like (probably due mainly to neurotoxic effects of ALA). The treatment of choice for the acute hepatic porphyrias is intravenous heme therapy, which repletes a critical regulatory heme pool in hepatocytes and leads to downregulation of hepatic ALA synthase, which is a biochemical hallmark of all forms of acute porphyria in relapse.
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Tissue distribution of zinc-mesoporphyrin in rats: relationship to inhibition of heme oxygenase
The Journal of pharmacology and experimental therapeutics, 1995Co-Authors: Shirley M. Russo, Edward Earl Cable, Joyce A. Pepe, Susan E. Donohue, Richard W. Lambrecht, Herbert L. BonkovskyAbstract:Metalloporphyrins, including heme and others that inhibit heme oxygenase, are agents with expanding therapeutic potential. Recent results from our laboratory showed that a combination of heme and zinc-mesoporphyrin was remarkably effective in ameliorating biochemical features of acute porphyria. The aim of this study was to assess plasma clearance, tissue distribution and persistence, stability, toxicology and metabolic effects of zinc-mesoporphyrin, after its i.v. administration to rats. After administration of 15 mumol/kg b.wt. of zinc-mesoporphyrin (bound to serum albumin in a 1:1 molar ratio) the Metalloporphyrin was rapidly cleared from plasma (half-life 3.6 h) with uptake primarily into liver and spleen, considerably less into the kidney and none detectable into the heart or brain. Hepatic heme oxygenase activity was undetectable for 4 days and less than 50% of control 1 week later. Inhibition of splenic heme oxygenase activity was also substantial but less marked than in the liver. No mortality was observed in any of the treated animals, and there was no detectable effect on gross or microscopic appearance of the liver, spleen, kidneys, heart, lungs or brain. Blood counts and chemistries remained within normal limits. We conclude that single doses of ZnMP-serum albumin are nontoxic, rapidly cleared from the plasma and persist primarily in the liver and spleen where heme oxygenase is inhibited for prolonged periods.
Mark E. Meyerhoff - One of the best experts on this subject based on the ideXlab platform.
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polymeric membrane electrodes with improved fluoride selectivity and lifetime based on zr iv and al iii tetraphenylporphyrin derivatives
Analytica Chimica Acta, 2007Co-Authors: Mariusz Pietrzak, Mark E. Meyerhoff, Elzbieta MalinowskaAbstract:Abstract Novel aluminum(III)- and zirconium(IV)-tetraphenylporhyrin (TPP) derivatives are examined as fluoride-selective ionophores for preparing polymer membrane-based ion-selective electrodes (ISEs). The influence of t -butyl- or dichloro-phenyl ring substituents as well as the nature of the metal ion center (Al(III) versus Zr(IV)) on the anion complexation constants of TPP derivative ionophores are reported. The anion binding stability constants of the ionophores are characterized by the so-called “sandwich membrane” method. All of the Metalloporphyrins examined form their strongest anion complexes with fluoride. The influence of plasticizer as well as the type of lipophilic ionic site additive and their amounts in the sensing membrane are discussed. It is shown that membrane electrodes formulated with the Metalloporphyrin derivatives and appropriate anionic or cationic additives exhibit enhanced potentiometric response toward fluoride over all other anions tested. Since selectivity toward fluoride is enhanced in the presence of both anionic and cationic additives, the Metalloporphyrins can function as either charged or neutral carriers within the organic membrane phase. In contrast to previously reported fluoride-selective polymeric membrane electrodes based on Metalloporphyrins, nernstian or near-nernstian (−51.2 to −60.1 mV decade −1 ) as well as rapid ( t t -butyltetraphenylporphyrin as the ionophore provides fluoride sensors with prolonged (7 months) functional lifetime.
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gallium iii and indium iii octaethylporphyrin dimeric complexes with a single μ hydroxo bridge synthesis structure and stability in anion containing organic media
Inorganica Chimica Acta, 2003Co-Authors: Elzbieta Malinowska, Pawel G Parzuchowski, Jeff W Kampf, Ewa Roźniecka, Yevgeniy Kondratenko, Mark E. MeyerhoffAbstract:Abstract The synthesis and single-crystal X-ray structures of the hydroxo-bridged complexes (μ-hydroxo)-bis(octaethylporphinato)gallium(III)perchlorate {[Ga(OEP)]2OH}ClO4 and (μ-hydroxo)-bis(octaethylporphinato)indium(III)tetrakis[3,5-bis-(trifluoromethyl)phenyl]borate {[In(OEP)]2OH}TFPB are reported. These complexes are prepared by the titration of monomeric Metalloporphyrin species in dichloromethane with diluted perchloric acid or by the addition of stoichiometric amounts of the tetraphenylborate derivative salt. The structures show that complexes of two Metalloporphyrins are joined by a single protonated metaloxygenmetal bridge with a nearly 150° bridge angle. The porphyrin rings of the dimers form dihedral angles of 15° Ga(III) and 23° In(III). In contrast to previously reported analogous dimeric Mn(III) and Fe(III) structures, the porphyrin rings of the present dimers are twisted by a much greater torsion angle of nearly 22°. In dichloromethane, high stability of the dimers is observed in the presence of perchlorate, but dissociation of the dimer species to monomers is found with increasing concentrations of halogen anions. This corresponds well with the observed anion selectivities recently reported for both electrochemical and optical anion sensors prepared with the respective Ga(III) and In(III) octaethylporphyrins in polymeric films.
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anion selective membrane electrodes based on Metalloporphyrins the influence of lipophilic anionic and cationic sites on potentiometric selectivity
Talanta, 1994Co-Authors: Eric Bakker, Elzbieta Malinowska, Robert D Schiller, Mark E. MeyerhoffAbstract:The role of lipophilic anionic and cationic additives on the potentiometric anion selectivities of polymer membrane electrodes prepared with various Metalloporphyrins as anion selective ionophores is examined. The presence of lipophilic anionic sites (e.g. tetraphenylborate derivatives) is shown to enhance the non-Hofmeister anion selectivities of membranes doped with In(III) and Sn(IV) porphyrins. In contrast, membranes containing Co(III) porphyrins require the addition of lipophilic cationic sites (e.g. tridodecylmethylammonium ions) in order to achieve optimal anion selectivity (for nitrite and thiocyanate) as well as rapid and reversible Nernstian response toward these anionic species. These experimental results coupled with appropriate theoretical models that predict the effect of lipophilic anion and cation sites on the selectivities of membranes doped with either neutral or charged carrier type ionophores may be used to determine the operative ionophore mechanism of each Metalloporphyrin complex within the organic membrane phase.
Lei Wang - One of the best experts on this subject based on the ideXlab platform.
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high performance p type organic thermoelectric materials based on Metalloporphyrin single walled carbon nanotube composite films
Journal of Power Sources, 2019Co-Authors: Yan Zhou, Yijia Liu, Xiaoyan Zhou, Yuan Gao, Chunmei Gao, Lei WangAbstract:Abstract Single-walled carbon nanotube/organic small molecule based thermoelectric materials have attracted significant scientific attention in recent years. However, up to now, no detailed thermoelectric study reported is focused on the single-walled carbon nanotube/organometallic complex composite films. By considering the excellent properties of tetraphenylporphyrin (such as its π-conjugated system, versatile structure and stability) and the important roles of metal ions in improving thermoelectric properties, Metalloporphyrins manifest great potential as composites for single-walled carbon nanotubes. Hence, in this work, we first propose a convenient strategy to obtain high-performance thermoelectric composites containing Metalloporphyrin molecules and single-walled carbon nanotubes. It is found that the single-walled carbon nanotube/ZnTPP composite film demonstrates the best thermoelectric performance with a maximum power factor of 247.2 μWm−1K−2 at 340 K, which is perhaps one of the highest thermoelectric power factors reported for single-walled carbon nanotube/organic small molecule-based p-type materials. Three p-type materials exhibit outstanding electric conductivities with a maximum of 1028.7 S cm−1 (single-walled carbon nanotube/CuTPP at 340 K). Furthermore, the produced thermoelectric materials manifest outstanding air stability and thermostability. Therefore, our proposed method can be a promising reference for fabricating novel p-type high-performance thermoelectric materials using Metalloporphyrin-based building blocks.
Manish Thapar - One of the best experts on this subject based on the ideXlab platform.
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porphyrin and heme metabolism and the porphyrias
Comprehensive Physiology, 2013Co-Authors: Herbert L. Bonkovsky, Tarun Narang, Ting Li, Manish ThaparAbstract:Porphyrins and Metalloporphyrins are the key pigments of life on earth as we know it, because they include chlorophyll (a magnesium-containing Metalloporphyrin) and heme (iron protoporphyrin). In eukaryotes, porphyrins and heme are synthesized by a multistep pathway that involves eight enzymes. The first and rate-controlling step is the formation of delta-aminolevulinic acid (ALA) from glycine plus succinyl CoA, catalyzed by ALA synthase. Intermediate steps occur in the cytoplasm, with formation of the monopyrrole porphobilinogen and the tetrapyrroles hydroxymethylbilane and a series of porphyrinogens, which are serially decarboxylated. Heme is utilized chiefly for the formation of hemoglobin in erythrocytes, myoglobin in muscle cells, cytochromes P-450 and mitochondrial cytochromes, and other hemoproteins in hepatocytes. The rate-controlling step of heme breakdown is catalyzed by heme oxygenase (HMOX), of which there are two isoforms, called HMOX1 and HMOX2. HMOX breaks down heme to form biliverdin, carbon monoxide, and iron. The porphyrias are a group of disorders, mainly inherited, in which there are defects in normal porphyrin and heme synthesis. The cardinal clinical features are cutaneous (due to the skin-damaging effects of excess deposited porphyrins) or neurovisceral attacks of pain, sometimes with weakness, delirium, seizures, and the like (probably due mainly to neurotoxic effects of ALA). The treatment of choice for the acute hepatic porphyrias is intravenous heme therapy, which repletes a critical regulatory heme pool in hepatocytes and leads to downregulation of hepatic ALA synthase, which is a biochemical hallmark of all forms of acute porphyria in relapse. © 2013 American Physiological Society. Compr Physiol 3:365-401, 2013.
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porphyrin and heme metabolism and the porphyrias
Comprehensive Physiology, 2013Co-Authors: Herbert L. Bonkovsky, Tarun Narang, Juntao Guo, Weihong Hou, Manish ThaparAbstract:Porphyrins and Metalloporphyrins are the key pigments of life on earth as we know it, because they include chlorophyll (a magnesium-containing Metalloporphyrin) and heme (iron protoporphyrin). In eukaryotes, porphyrins and heme are synthesized by a multistep pathway that involves eight enzymes. The first and rate-controlling step is the formation of delta-aminolevulinic acid (ALA) from glycine plus succinyl CoA, catalyzed by ALA synthase. Intermediate steps occur in the cytoplasm, with formation of the monopyrrole porphobilinogen and the tetrapyrroles hydroxymethylbilane and a series of porphyrinogens, which are serially decarboxylated. Heme is utilized chiefly for the formation of hemoglobin in erythrocytes, myoglobin in muscle cells, cytochromes P-450 and mitochondrial cytochromes, and other hemoproteins in hepatocytes. The rate-controlling step of heme breakdown is catalyzed by heme oxygenase (HMOX), of which there are two isoforms, called HMOX1 and HMOX2. HMOX breaks down heme to form biliverdin, carbon monoxide, and iron. The porphyrias are a group of disorders, mainly inherited, in which there are defects in normal porphyrin and heme synthesis. The cardinal clinical features are cutaneous (due to the skin-damaging effects of excess deposited porphyrins) or neurovisceral attacks of pain, sometimes with weakness, delirium, seizures, and the like (probably due mainly to neurotoxic effects of ALA). The treatment of choice for the acute hepatic porphyrias is intravenous heme therapy, which repletes a critical regulatory heme pool in hepatocytes and leads to downregulation of hepatic ALA synthase, which is a biochemical hallmark of all forms of acute porphyria in relapse.
Elzbieta Malinowska - One of the best experts on this subject based on the ideXlab platform.
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polymeric membrane electrodes with improved fluoride selectivity and lifetime based on zr iv and al iii tetraphenylporphyrin derivatives
Analytica Chimica Acta, 2007Co-Authors: Mariusz Pietrzak, Mark E. Meyerhoff, Elzbieta MalinowskaAbstract:Abstract Novel aluminum(III)- and zirconium(IV)-tetraphenylporhyrin (TPP) derivatives are examined as fluoride-selective ionophores for preparing polymer membrane-based ion-selective electrodes (ISEs). The influence of t -butyl- or dichloro-phenyl ring substituents as well as the nature of the metal ion center (Al(III) versus Zr(IV)) on the anion complexation constants of TPP derivative ionophores are reported. The anion binding stability constants of the ionophores are characterized by the so-called “sandwich membrane” method. All of the Metalloporphyrins examined form their strongest anion complexes with fluoride. The influence of plasticizer as well as the type of lipophilic ionic site additive and their amounts in the sensing membrane are discussed. It is shown that membrane electrodes formulated with the Metalloporphyrin derivatives and appropriate anionic or cationic additives exhibit enhanced potentiometric response toward fluoride over all other anions tested. Since selectivity toward fluoride is enhanced in the presence of both anionic and cationic additives, the Metalloporphyrins can function as either charged or neutral carriers within the organic membrane phase. In contrast to previously reported fluoride-selective polymeric membrane electrodes based on Metalloporphyrins, nernstian or near-nernstian (−51.2 to −60.1 mV decade −1 ) as well as rapid ( t t -butyltetraphenylporphyrin as the ionophore provides fluoride sensors with prolonged (7 months) functional lifetime.
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gallium iii and indium iii octaethylporphyrin dimeric complexes with a single μ hydroxo bridge synthesis structure and stability in anion containing organic media
Inorganica Chimica Acta, 2003Co-Authors: Elzbieta Malinowska, Pawel G Parzuchowski, Jeff W Kampf, Ewa Roźniecka, Yevgeniy Kondratenko, Mark E. MeyerhoffAbstract:Abstract The synthesis and single-crystal X-ray structures of the hydroxo-bridged complexes (μ-hydroxo)-bis(octaethylporphinato)gallium(III)perchlorate {[Ga(OEP)]2OH}ClO4 and (μ-hydroxo)-bis(octaethylporphinato)indium(III)tetrakis[3,5-bis-(trifluoromethyl)phenyl]borate {[In(OEP)]2OH}TFPB are reported. These complexes are prepared by the titration of monomeric Metalloporphyrin species in dichloromethane with diluted perchloric acid or by the addition of stoichiometric amounts of the tetraphenylborate derivative salt. The structures show that complexes of two Metalloporphyrins are joined by a single protonated metaloxygenmetal bridge with a nearly 150° bridge angle. The porphyrin rings of the dimers form dihedral angles of 15° Ga(III) and 23° In(III). In contrast to previously reported analogous dimeric Mn(III) and Fe(III) structures, the porphyrin rings of the present dimers are twisted by a much greater torsion angle of nearly 22°. In dichloromethane, high stability of the dimers is observed in the presence of perchlorate, but dissociation of the dimer species to monomers is found with increasing concentrations of halogen anions. This corresponds well with the observed anion selectivities recently reported for both electrochemical and optical anion sensors prepared with the respective Ga(III) and In(III) octaethylporphyrins in polymeric films.
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anion selective membrane electrodes based on Metalloporphyrins the influence of lipophilic anionic and cationic sites on potentiometric selectivity
Talanta, 1994Co-Authors: Eric Bakker, Elzbieta Malinowska, Robert D Schiller, Mark E. MeyerhoffAbstract:The role of lipophilic anionic and cationic additives on the potentiometric anion selectivities of polymer membrane electrodes prepared with various Metalloporphyrins as anion selective ionophores is examined. The presence of lipophilic anionic sites (e.g. tetraphenylborate derivatives) is shown to enhance the non-Hofmeister anion selectivities of membranes doped with In(III) and Sn(IV) porphyrins. In contrast, membranes containing Co(III) porphyrins require the addition of lipophilic cationic sites (e.g. tridodecylmethylammonium ions) in order to achieve optimal anion selectivity (for nitrite and thiocyanate) as well as rapid and reversible Nernstian response toward these anionic species. These experimental results coupled with appropriate theoretical models that predict the effect of lipophilic anion and cation sites on the selectivities of membranes doped with either neutral or charged carrier type ionophores may be used to determine the operative ionophore mechanism of each Metalloporphyrin complex within the organic membrane phase.