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Production of Superoxide from Hemoglobin-Bound Oxygen Under Hypoxic Conditions
By low temperature electron paramagnetic resonance we have detected the formation of a free radical signal during incubation of partially oxygenated hemoglobin at 235 K. The observed signal has g ∥ = 2.0565 and g ⊥ = 2.0043, consistent with the previously reported values for superoxide. The presence...
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Published in: | Biochemistry (Easton) 1996-05, Vol.35 (20), p.6393-6398 |
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creator | Balagopalakrishna, Chavali Manoharan, Periakarupan T Abugo, Omoefe O Rifkind, Joseph M |
description | By low temperature electron paramagnetic resonance we have detected the formation of a free radical signal during incubation of partially oxygenated hemoglobin at 235 K. The observed signal has g ∥ = 2.0565 and g ⊥ = 2.0043, consistent with the previously reported values for superoxide. The presence of additional EPR signals for oxygen-17 bound hemoglobin, with (O17-O17) A ⊥= 63 G and (O17-O16) A ⊥ = 94 G under identical conditions, confirms the presence of a radical containing two nonequivalent oxygens as required for a superoxide in magnetically inequivalent environments. The superoxide radical has not previously been directly detected during hemoglobin autoxidation because of its rapid dismutation. Our ability to follow the formation of superoxide for more than 15 min is attributed to its production in the hydrophobic heme pocket where dismutation is slow. The enhanced production of this free radical at intermediate oxygen pressures is shown to coincide with enhanced rates of hemoglobin autoxidation for partially oxygenated intermediates. The formation of superoxide in the heme pocket under these conditions is attributed to enhanced heme pocket flexibility. Greater flexibility facilitates distal histidine interactions which destabilize the iron−oxygen bond resulting in the release of superoxide radical into the heme pocket. |
doi_str_mv | 10.1021/bi952875+ |
format | article |
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The observed signal has g ∥ = 2.0565 and g ⊥ = 2.0043, consistent with the previously reported values for superoxide. The presence of additional EPR signals for oxygen-17 bound hemoglobin, with (O17-O17) A ⊥= 63 G and (O17-O16) A ⊥ = 94 G under identical conditions, confirms the presence of a radical containing two nonequivalent oxygens as required for a superoxide in magnetically inequivalent environments. The superoxide radical has not previously been directly detected during hemoglobin autoxidation because of its rapid dismutation. Our ability to follow the formation of superoxide for more than 15 min is attributed to its production in the hydrophobic heme pocket where dismutation is slow. The enhanced production of this free radical at intermediate oxygen pressures is shown to coincide with enhanced rates of hemoglobin autoxidation for partially oxygenated intermediates. The formation of superoxide in the heme pocket under these conditions is attributed to enhanced heme pocket flexibility. Greater flexibility facilitates distal histidine interactions which destabilize the iron−oxygen bond resulting in the release of superoxide radical into the heme pocket.</description><identifier>ISSN: 0006-2960</identifier><identifier>EISSN: 1520-4995</identifier><identifier>DOI: 10.1021/bi952875+</identifier><identifier>PMID: 8639585</identifier><language>eng</language><publisher>United States: American Chemical Society</publisher><subject>Cell Hypoxia - physiology ; Electron Spin Resonance Spectroscopy ; Erythrocytes - metabolism ; Free Radicals - chemistry ; Heme - chemistry ; Hemoglobins - chemistry ; Hemoglobins - metabolism ; Humans ; In Vitro Techniques ; Oxidation-Reduction ; Oxygen - blood ; Oxygen - metabolism ; Protein Binding ; Superoxides - blood ; Superoxides - chemistry ; Superoxides - metabolism</subject><ispartof>Biochemistry (Easton), 1996-05, Vol.35 (20), p.6393-6398</ispartof><rights>Copyright © 1996 American Chemical Society</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><cites>FETCH-LOGICAL-a306t-2aa455809568fa8ee206484c7742955bb4f205ffd23138d50d3076ec5634d9683</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,776,780,27903,27904</link.rule.ids><backlink>$$Uhttps://www.ncbi.nlm.nih.gov/pubmed/8639585$$D View this record in MEDLINE/PubMed$$Hfree_for_read</backlink></links><search><creatorcontrib>Balagopalakrishna, Chavali</creatorcontrib><creatorcontrib>Manoharan, Periakarupan T</creatorcontrib><creatorcontrib>Abugo, Omoefe O</creatorcontrib><creatorcontrib>Rifkind, Joseph M</creatorcontrib><title>Production of Superoxide from Hemoglobin-Bound Oxygen Under Hypoxic Conditions</title><title>Biochemistry (Easton)</title><addtitle>Biochemistry</addtitle><description>By low temperature electron paramagnetic resonance we have detected the formation of a free radical signal during incubation of partially oxygenated hemoglobin at 235 K. The observed signal has g ∥ = 2.0565 and g ⊥ = 2.0043, consistent with the previously reported values for superoxide. The presence of additional EPR signals for oxygen-17 bound hemoglobin, with (O17-O17) A ⊥= 63 G and (O17-O16) A ⊥ = 94 G under identical conditions, confirms the presence of a radical containing two nonequivalent oxygens as required for a superoxide in magnetically inequivalent environments. The superoxide radical has not previously been directly detected during hemoglobin autoxidation because of its rapid dismutation. Our ability to follow the formation of superoxide for more than 15 min is attributed to its production in the hydrophobic heme pocket where dismutation is slow. The enhanced production of this free radical at intermediate oxygen pressures is shown to coincide with enhanced rates of hemoglobin autoxidation for partially oxygenated intermediates. The formation of superoxide in the heme pocket under these conditions is attributed to enhanced heme pocket flexibility. Greater flexibility facilitates distal histidine interactions which destabilize the iron−oxygen bond resulting in the release of superoxide radical into the heme pocket.</description><subject>Cell Hypoxia - physiology</subject><subject>Electron Spin Resonance Spectroscopy</subject><subject>Erythrocytes - metabolism</subject><subject>Free Radicals - chemistry</subject><subject>Heme - chemistry</subject><subject>Hemoglobins - chemistry</subject><subject>Hemoglobins - metabolism</subject><subject>Humans</subject><subject>In Vitro Techniques</subject><subject>Oxidation-Reduction</subject><subject>Oxygen - blood</subject><subject>Oxygen - metabolism</subject><subject>Protein Binding</subject><subject>Superoxides - blood</subject><subject>Superoxides - chemistry</subject><subject>Superoxides - metabolism</subject><issn>0006-2960</issn><issn>1520-4995</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>1996</creationdate><recordtype>article</recordtype><recordid>eNplkE1Lw0AURQdRaq0u_AFCFiKCRCfznaUWtWJpi23dDpPMpESbTJxJoP33pqR24-rxuId74QBwGcH7CKLoIcljigSnd0egH1EEQxLH9Bj0IYQsRDGDp-DM-6_2JZCTHugJhmMqaB9MZs7qJq1zWwY2C-ZNZZzd5NoEmbNFMDKFXa1tkpfhk21KHUw325Upg2WpjQtG26pl02BoS53vKvw5OMnU2puL_R2A5cvzYjgKx9PXt-HjOFQYsjpEShFKBYwpE5kSxiDIiCAp5wTFlCYJyRCkWaYRjrDQFGoMOTMpZZjomAk8ADddb-XsT2N8LYvcp2a9VqWxjZdcwLYekRa87cDUWe-dyWTl8kK5rYyg3LmTf-5a9Grf2SSF0Qdw76rNwy7PfW02h1i5b8k45lQuZnP5iaMP9j6Zyd30dcer1Msv27iyNfJ_9heXxoKk</recordid><startdate>19960521</startdate><enddate>19960521</enddate><creator>Balagopalakrishna, Chavali</creator><creator>Manoharan, Periakarupan T</creator><creator>Abugo, Omoefe O</creator><creator>Rifkind, Joseph M</creator><general>American Chemical Society</general><scope>BSCLL</scope><scope>CGR</scope><scope>CUY</scope><scope>CVF</scope><scope>ECM</scope><scope>EIF</scope><scope>NPM</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7X8</scope></search><sort><creationdate>19960521</creationdate><title>Production of Superoxide from Hemoglobin-Bound Oxygen Under Hypoxic Conditions</title><author>Balagopalakrishna, Chavali ; Manoharan, Periakarupan T ; Abugo, Omoefe O ; Rifkind, Joseph M</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-a306t-2aa455809568fa8ee206484c7742955bb4f205ffd23138d50d3076ec5634d9683</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>1996</creationdate><topic>Cell Hypoxia - physiology</topic><topic>Electron Spin Resonance Spectroscopy</topic><topic>Erythrocytes - metabolism</topic><topic>Free Radicals - chemistry</topic><topic>Heme - chemistry</topic><topic>Hemoglobins - chemistry</topic><topic>Hemoglobins - metabolism</topic><topic>Humans</topic><topic>In Vitro Techniques</topic><topic>Oxidation-Reduction</topic><topic>Oxygen - blood</topic><topic>Oxygen - metabolism</topic><topic>Protein Binding</topic><topic>Superoxides - blood</topic><topic>Superoxides - chemistry</topic><topic>Superoxides - metabolism</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Balagopalakrishna, Chavali</creatorcontrib><creatorcontrib>Manoharan, Periakarupan T</creatorcontrib><creatorcontrib>Abugo, Omoefe O</creatorcontrib><creatorcontrib>Rifkind, Joseph M</creatorcontrib><collection>Istex</collection><collection>Medline</collection><collection>MEDLINE</collection><collection>MEDLINE (Ovid)</collection><collection>MEDLINE</collection><collection>MEDLINE</collection><collection>PubMed</collection><collection>CrossRef</collection><collection>MEDLINE - Academic</collection><jtitle>Biochemistry (Easton)</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Balagopalakrishna, Chavali</au><au>Manoharan, Periakarupan T</au><au>Abugo, Omoefe O</au><au>Rifkind, Joseph M</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Production of Superoxide from Hemoglobin-Bound Oxygen Under Hypoxic Conditions</atitle><jtitle>Biochemistry (Easton)</jtitle><addtitle>Biochemistry</addtitle><date>1996-05-21</date><risdate>1996</risdate><volume>35</volume><issue>20</issue><spage>6393</spage><epage>6398</epage><pages>6393-6398</pages><issn>0006-2960</issn><eissn>1520-4995</eissn><abstract>By low temperature electron paramagnetic resonance we have detected the formation of a free radical signal during incubation of partially oxygenated hemoglobin at 235 K. The observed signal has g ∥ = 2.0565 and g ⊥ = 2.0043, consistent with the previously reported values for superoxide. The presence of additional EPR signals for oxygen-17 bound hemoglobin, with (O17-O17) A ⊥= 63 G and (O17-O16) A ⊥ = 94 G under identical conditions, confirms the presence of a radical containing two nonequivalent oxygens as required for a superoxide in magnetically inequivalent environments. The superoxide radical has not previously been directly detected during hemoglobin autoxidation because of its rapid dismutation. Our ability to follow the formation of superoxide for more than 15 min is attributed to its production in the hydrophobic heme pocket where dismutation is slow. The enhanced production of this free radical at intermediate oxygen pressures is shown to coincide with enhanced rates of hemoglobin autoxidation for partially oxygenated intermediates. The formation of superoxide in the heme pocket under these conditions is attributed to enhanced heme pocket flexibility. Greater flexibility facilitates distal histidine interactions which destabilize the iron−oxygen bond resulting in the release of superoxide radical into the heme pocket.</abstract><cop>United States</cop><pub>American Chemical Society</pub><pmid>8639585</pmid><doi>10.1021/bi952875+</doi><tpages>6</tpages></addata></record> |
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source | American Chemical Society:Jisc Collections:American Chemical Society Read & Publish Agreement 2022-2024 (Reading list) |
subjects | Cell Hypoxia - physiology Electron Spin Resonance Spectroscopy Erythrocytes - metabolism Free Radicals - chemistry Heme - chemistry Hemoglobins - chemistry Hemoglobins - metabolism Humans In Vitro Techniques Oxidation-Reduction Oxygen - blood Oxygen - metabolism Protein Binding Superoxides - blood Superoxides - chemistry Superoxides - metabolism |
title | Production of Superoxide from Hemoglobin-Bound Oxygen Under Hypoxic Conditions |
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