The pH sensitivity of −NH exchange in LnDOTA-tetraamide complexes varies with amide substituent
Identifieur interne : 000527 ( Ncbi/Merge ); précédent : 000526; suivant : 000528The pH sensitivity of −NH exchange in LnDOTA-tetraamide complexes varies with amide substituent
Auteurs : Ana Christina L. Opina [États-Unis] ; Yunkou Wu [États-Unis] ; Piyu Zhao [États-Unis] ; Garry Kiefer [États-Unis] ; A. Dean Sherry [États-Unis]Source :
- Contrast media & molecular imaging [ 1555-4309 ] ; 2011.
Descripteurs français
- KwdFr :
- MESH :
English descriptors
- KwdEn :
- Amides (chemistry), Bismuth (chemistry), Contrast Media (chemistry), Drug Combinations, Glycine (chemistry), Heterocyclic Compounds, 1-Ring (chemistry), Hydrogen-Ion Concentration, Indenes (chemistry), Lanthanoid Series Elements (chemistry), Magnetic Resonance Imaging, Piperazines (chemistry), Propanolamines (chemistry), Protons, Water (chemistry).
- MESH :
- chemical , chemistry : Amides, Bismuth, Contrast Media, Glycine, Heterocyclic Compounds, 1-Ring, Indenes, Lanthanoid Series Elements, Piperazines, Propanolamines, Water.
- chemical : Drug Combinations, Protons.
- Hydrogen-Ion Concentration, Magnetic Resonance Imaging.
Abstract
The amide proton exchange rates in various lanthanide(III) DOTA-tetraamide complexes were investigated by CEST as a function of variable chemical structures and charges on the amide substituents. Comparisons were made between YbDOTA-(gly)4− (Yb-1), YbDOTA-(NHCH2PO3)45− (Yb-2), and YbDOTA-(NHCH2PO3Et2)43+ (Yb-3). The general shapes of the CEST versus pH profiles were similar for the three complexes but they showed maximum CEST intensities at different pH values, pH 8.3, 8.8 and 6.9 for Yb-1, Yb-2 and Yb-3, respectively. This indicates that a more negatively charged substituent on the amide helps stabilize the partial positive charge on the amide nitrogen and consequently more base is required to catalyze proton exchange. The chemical shifts of the −NH protons in Yb-1 and Yb-2 were similar (−17 ppm) while the −NH proton in Yb-3 was at −13 ppm. This shows that crystal field produced by the amide oxygen donor atoms in Yb-3 is substantially weaker than that in the other two complexes. In an effort to expand the useful range of pH values that might be measured using these complexes as CEST agents, the shapes of the CEST versus pH curves were also determined for two thulium(III) complexes with much larger hyperfine shifted −NH proton resonances. The ratio of CEST from −NH exchange in Tm-1 compared to CEST from −NH exchange in Tm-3 was found to be linear over an extended pH range, from 6.3 to 7.4. This demonstrates a potential advantage of using mixtures of lanthanide(III) DOTA-tetraamides for mapping tissue pH by use of ratiometric CEST imaging.
Url:
DOI: 10.1002/cmmi.445
PubMed: 22144023
PubMed Central: 3233223
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Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Sherry, A Dean" sort="Sherry, A Dean" uniqKey="Sherry A" first="A. Dean" last="Sherry">A. Dean Sherry</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation><affiliation wicri:level="1"><nlm:aff id="A2">Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas 75390-8568, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas 75390-8568</wicri:regionArea><wicri:noRegion>Texas 75390-8568</wicri:noRegion></affiliation></author></analytic><series><title level="j">Contrast media & molecular imaging</title><idno type="ISSN">1555-4309</idno><idno type="eISSN">1555-4317</idno><imprint><date when="2011">2011</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>Amides (chemistry)</term><term>Bismuth (chemistry)</term><term>Contrast Media (chemistry)</term><term>Drug Combinations</term><term>Glycine (chemistry)</term><term>Heterocyclic Compounds, 1-Ring (chemistry)</term><term>Hydrogen-Ion Concentration</term><term>Indenes (chemistry)</term><term>Lanthanoid Series Elements (chemistry)</term><term>Magnetic Resonance Imaging</term><term>Piperazines (chemistry)</term><term>Propanolamines (chemistry)</term><term>Protons</term><term>Water (chemistry)</term></keywords><keywords scheme="KwdFr" xml:lang="fr"><term>Amides ()</term><term>Association médicamenteuse</term><term>Bismuth ()</term><term>Composés hétéromonocycliques ()</term><term>Concentration en ions d'hydrogène</term><term>Eau ()</term><term>Glycine ()</term><term>Imagerie par résonance magnétique</term><term>Indènes ()</term><term>Lanthanides ()</term><term>Pipérazines ()</term><term>Produits de contraste ()</term><term>Propanolamines ()</term><term>Protons</term></keywords><keywords scheme="MESH" type="chemical" qualifier="chemistry" xml:lang="en"><term>Amides</term><term>Bismuth</term><term>Contrast Media</term><term>Glycine</term><term>Heterocyclic Compounds, 1-Ring</term><term>Indenes</term><term>Lanthanoid Series Elements</term><term>Piperazines</term><term>Propanolamines</term><term>Water</term></keywords><keywords scheme="MESH" type="chemical" xml:lang="en"><term>Drug Combinations</term><term>Protons</term></keywords><keywords scheme="MESH" xml:lang="en"><term>Hydrogen-Ion Concentration</term><term>Magnetic Resonance Imaging</term></keywords><keywords scheme="MESH" xml:lang="fr"><term>Amides</term><term>Association médicamenteuse</term><term>Bismuth</term><term>Composés hétéromonocycliques</term><term>Concentration en ions d'hydrogène</term><term>Eau</term><term>Glycine</term><term>Imagerie par résonance magnétique</term><term>Indènes</term><term>Lanthanides</term><term>Pipérazines</term><term>Produits de contraste</term><term>Propanolamines</term><term>Protons</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en"><p id="P1">The amide proton exchange rates in various lanthanide(III) DOTA-tetraamide complexes were investigated by CEST as a function of variable chemical structures and charges on the amide substituents. Comparisons were made between YbDOTA-(gly)<sub>4</sub><sup>−</sup> (Yb-1), YbDOTA-(NHCH<sub>2</sub>PO<sub>3</sub>)<sub>4</sub><sup>5−</sup> (Yb-2), and YbDOTA-(NHCH<sub>2</sub>PO<sub>3</sub>Et<sub>2</sub>)<sub>4</sub><sup>3+</sup> (Yb-3). The general shapes of the CEST versus pH profiles were similar for the three complexes but they showed maximum CEST intensities at different pH values, pH 8.3, 8.8 and 6.9 for Yb-1, Yb-2 and Yb-3, respectively. This indicates that a more negatively charged substituent on the amide helps stabilize the partial positive charge on the amide nitrogen and consequently more base is required to catalyze proton exchange. The chemical shifts of the −NH protons in Yb-1 and Yb-2 were similar (−17 ppm) while the −NH proton in Yb-3 was at −13 ppm. This shows that crystal field produced by the amide oxygen donor atoms in Yb-3 is substantially weaker than that in the other two complexes. In an effort to expand the useful range of pH values that might be measured using these complexes as CEST agents, the shapes of the CEST versus pH curves were also determined for two thulium(III) complexes with much larger hyperfine shifted −NH proton resonances. The ratio of CEST from −NH exchange in Tm-1 compared to CEST from −NH exchange in Tm-3 was found to be linear over an extended pH range, from 6.3 to 7.4. This demonstrates a potential advantage of using mixtures of lanthanide(III) DOTA-tetraamides for mapping tissue pH by use of ratiometric CEST imaging.</p></div></front></TEI><double pmid="22144023"><pmc><TEI><teiHeader><fileDesc><titleStmt><title xml:lang="en">The pH sensitivity of −NH exchange in LnDOTA-tetraamide complexes varies with amide substituent</title><author><name sortKey="Opina, Ana Christina L" sort="Opina, Ana Christina L" uniqKey="Opina A" first="Ana Christina L." last="Opina">Ana Christina L. Opina</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Wu, Yunkou" sort="Wu, Yunkou" uniqKey="Wu Y" first="Yunkou" last="Wu">Yunkou Wu</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Zhao, Piyu" sort="Zhao, Piyu" uniqKey="Zhao P" first="Piyu" last="Zhao">Piyu Zhao</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Kiefer, Garry" sort="Kiefer, Garry" uniqKey="Kiefer G" first="Garry" last="Kiefer">Garry Kiefer</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Sherry, A Dean" sort="Sherry, A Dean" uniqKey="Sherry A" first="A. Dean" last="Sherry">A. Dean Sherry</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation><affiliation wicri:level="1"><nlm:aff id="A2">Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas 75390-8568, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas 75390-8568</wicri:regionArea><wicri:noRegion>Texas 75390-8568</wicri:noRegion></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">PMC</idno><idno type="pmid">22144023</idno><idno type="pmc">3233223</idno><idno type="url">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3233223</idno><idno type="RBID">PMC:3233223</idno><idno type="doi">10.1002/cmmi.445</idno><date when="2011">2011</date><idno type="wicri:Area/Pmc/Corpus">000217</idno><idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Corpus" wicri:corpus="PMC">000217</idno><idno type="wicri:Area/Pmc/Curation">000217</idno><idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Curation">000217</idno><idno type="wicri:Area/Pmc/Checkpoint">000238</idno><idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Checkpoint">000238</idno></publicationStmt><sourceDesc><biblStruct><analytic><title xml:lang="en" level="a" type="main">The pH sensitivity of −NH exchange in LnDOTA-tetraamide complexes varies with amide substituent</title><author><name sortKey="Opina, Ana Christina L" sort="Opina, Ana Christina L" uniqKey="Opina A" first="Ana Christina L." last="Opina">Ana Christina L. Opina</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Wu, Yunkou" sort="Wu, Yunkou" uniqKey="Wu Y" first="Yunkou" last="Wu">Yunkou Wu</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Zhao, Piyu" sort="Zhao, Piyu" uniqKey="Zhao P" first="Piyu" last="Zhao">Piyu Zhao</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Kiefer, Garry" sort="Kiefer, Garry" uniqKey="Kiefer G" first="Garry" last="Kiefer">Garry Kiefer</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Sherry, A Dean" sort="Sherry, A Dean" uniqKey="Sherry A" first="A. Dean" last="Sherry">A. Dean Sherry</name><affiliation wicri:level="2"><nlm:aff id="A1">Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, 800 W. Campbell Road, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation><affiliation wicri:level="1"><nlm:aff id="A2">Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas 75390-8568, UNITED STATES</nlm:aff><country xml:lang="fr" wicri:curation="lc">États-Unis</country><wicri:regionArea>Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas 75390-8568</wicri:regionArea><wicri:noRegion>Texas 75390-8568</wicri:noRegion></affiliation></author></analytic><series><title level="j">Contrast media & molecular imaging</title><idno type="ISSN">1555-4309</idno><idno type="eISSN">1555-4317</idno><imprint><date when="2011">2011</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en"><p id="P1">The amide proton exchange rates in various lanthanide(III) DOTA-tetraamide complexes were investigated by CEST as a function of variable chemical structures and charges on the amide substituents. Comparisons were made between YbDOTA-(gly)<sub>4</sub><sup>−</sup> (Yb-1), YbDOTA-(NHCH<sub>2</sub>PO<sub>3</sub>)<sub>4</sub><sup>5−</sup> (Yb-2), and YbDOTA-(NHCH<sub>2</sub>PO<sub>3</sub>Et<sub>2</sub>)<sub>4</sub><sup>3+</sup> (Yb-3). The general shapes of the CEST versus pH profiles were similar for the three complexes but they showed maximum CEST intensities at different pH values, pH 8.3, 8.8 and 6.9 for Yb-1, Yb-2 and Yb-3, respectively. This indicates that a more negatively charged substituent on the amide helps stabilize the partial positive charge on the amide nitrogen and consequently more base is required to catalyze proton exchange. The chemical shifts of the −NH protons in Yb-1 and Yb-2 were similar (−17 ppm) while the −NH proton in Yb-3 was at −13 ppm. This shows that crystal field produced by the amide oxygen donor atoms in Yb-3 is substantially weaker than that in the other two complexes. In an effort to expand the useful range of pH values that might be measured using these complexes as CEST agents, the shapes of the CEST versus pH curves were also determined for two thulium(III) complexes with much larger hyperfine shifted −NH proton resonances. The ratio of CEST from −NH exchange in Tm-1 compared to CEST from −NH exchange in Tm-3 was found to be linear over an extended pH range, from 6.3 to 7.4. This demonstrates a potential advantage of using mixtures of lanthanide(III) DOTA-tetraamides for mapping tissue pH by use of ratiometric CEST imaging.</p></div></front></TEI></pmc><pubmed><TEI><teiHeader><fileDesc><titleStmt><title xml:lang="en">The pH sensitivity of -NH exchange in LnDOTA-tetraamide complexes varies with amide substituent.</title><author><name sortKey="Opina, Ana Christina L" sort="Opina, Ana Christina L" uniqKey="Opina A" first="Ana Christina L" last="Opina">Ana Christina L. Opina</name><affiliation wicri:level="2"><nlm:affiliation>Department of Chemistry, University of Texas at Dallas, Richardson, TX 75083-0688, USA.</nlm:affiliation><country xml:lang="fr">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Wu, Yunkou" sort="Wu, Yunkou" uniqKey="Wu Y" first="Yunkou" last="Wu">Yunkou Wu</name></author><author><name sortKey="Zhao, Piyu" sort="Zhao, Piyu" uniqKey="Zhao P" first="Piyu" last="Zhao">Piyu Zhao</name></author><author><name sortKey="Kiefer, Garry" sort="Kiefer, Garry" uniqKey="Kiefer G" first="Garry" last="Kiefer">Garry Kiefer</name></author><author><name sortKey="Sherry, A Dean" sort="Sherry, A Dean" uniqKey="Sherry A" first="A Dean" last="Sherry">A Dean Sherry</name></author></titleStmt><publicationStmt><idno type="wicri:source">PubMed</idno><date when="????"><PubDate><MedlineDate>2011 Nov-Dec</MedlineDate></PubDate></date><idno type="doi">10.1002/cmmi.445</idno><idno type="RBID">pubmed:22144023</idno><idno type="pmid">22144023</idno><idno type="wicri:Area/PubMed/Corpus">000399</idno><idno type="wicri:explorRef" wicri:stream="PubMed" wicri:step="Corpus" wicri:corpus="PubMed">000399</idno><idno type="wicri:Area/PubMed/Curation">000399</idno><idno type="wicri:explorRef" wicri:stream="PubMed" wicri:step="Curation">000399</idno><idno type="wicri:Area/PubMed/Checkpoint">000399</idno><idno type="wicri:explorRef" wicri:stream="Checkpoint" wicri:step="PubMed">000399</idno></publicationStmt><sourceDesc><biblStruct><analytic><title xml:lang="en">The pH sensitivity of -NH exchange in LnDOTA-tetraamide complexes varies with amide substituent.</title><author><name sortKey="Opina, Ana Christina L" sort="Opina, Ana Christina L" uniqKey="Opina A" first="Ana Christina L" last="Opina">Ana Christina L. Opina</name><affiliation wicri:level="2"><nlm:affiliation>Department of Chemistry, University of Texas at Dallas, Richardson, TX 75083-0688, USA.</nlm:affiliation><country xml:lang="fr">États-Unis</country><wicri:regionArea>Department of Chemistry, University of Texas at Dallas, Richardson, TX 75083-0688</wicri:regionArea><placeName><region type="state">Texas</region></placeName></affiliation></author><author><name sortKey="Wu, Yunkou" sort="Wu, Yunkou" uniqKey="Wu Y" first="Yunkou" last="Wu">Yunkou Wu</name></author><author><name sortKey="Zhao, Piyu" sort="Zhao, Piyu" uniqKey="Zhao P" first="Piyu" last="Zhao">Piyu Zhao</name></author><author><name sortKey="Kiefer, Garry" sort="Kiefer, Garry" uniqKey="Kiefer G" first="Garry" last="Kiefer">Garry Kiefer</name></author><author><name sortKey="Sherry, A Dean" sort="Sherry, A Dean" uniqKey="Sherry A" first="A Dean" last="Sherry">A Dean Sherry</name></author></analytic><series><title level="j">Contrast media & molecular imaging</title><idno type="eISSN">1555-4317</idno></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>Amides (chemistry)</term><term>Bismuth (chemistry)</term><term>Contrast Media (chemistry)</term><term>Drug Combinations</term><term>Glycine (chemistry)</term><term>Heterocyclic Compounds, 1-Ring (chemistry)</term><term>Hydrogen-Ion Concentration</term><term>Indenes (chemistry)</term><term>Lanthanoid Series Elements (chemistry)</term><term>Magnetic Resonance Imaging</term><term>Piperazines (chemistry)</term><term>Propanolamines (chemistry)</term><term>Protons</term><term>Water (chemistry)</term></keywords><keywords scheme="KwdFr" xml:lang="fr"><term>Amides ()</term><term>Association médicamenteuse</term><term>Bismuth ()</term><term>Composés hétéromonocycliques ()</term><term>Concentration en ions d'hydrogène</term><term>Eau ()</term><term>Glycine ()</term><term>Imagerie par résonance magnétique</term><term>Indènes ()</term><term>Lanthanides ()</term><term>Pipérazines ()</term><term>Produits de contraste ()</term><term>Propanolamines ()</term><term>Protons</term></keywords><keywords scheme="MESH" type="chemical" qualifier="chemistry" xml:lang="en"><term>Amides</term><term>Bismuth</term><term>Contrast Media</term><term>Glycine</term><term>Heterocyclic Compounds, 1-Ring</term><term>Indenes</term><term>Lanthanoid Series Elements</term><term>Piperazines</term><term>Propanolamines</term><term>Water</term></keywords><keywords scheme="MESH" type="chemical" xml:lang="en"><term>Drug Combinations</term><term>Protons</term></keywords><keywords scheme="MESH" xml:lang="en"><term>Hydrogen-Ion Concentration</term><term>Magnetic Resonance Imaging</term></keywords><keywords scheme="MESH" xml:lang="fr"><term>Amides</term><term>Association médicamenteuse</term><term>Bismuth</term><term>Composés hétéromonocycliques</term><term>Concentration en ions d'hydrogène</term><term>Eau</term><term>Glycine</term><term>Imagerie par résonance magnétique</term><term>Indènes</term><term>Lanthanides</term><term>Pipérazines</term><term>Produits de contraste</term><term>Propanolamines</term><term>Protons</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">The amide proton exchange rates in various lanthanide(III) DOTA-tetraamide complexes were investigated by CEST as a function of variable chemical structures and charges on the amide substituents. Comparisons were made between YbDOTA-(gly)(4)(-) (Yb-1), YbDOTA-(NHCH(2)PO(3))(4 (5-) (Yb-2) and YbDOTA-(NHCH(2)PO(3)Et(2))(4)(3+) (Yb-3). The general shapes of the CEST vs pH profiles were similar for the three complexes but they showed maximum CEST intensities at different pH values, pH 8.3, 8.8 and 6.9 for Yb-1, Yb-2 and Yb-3, respectively. This indicates that a more negatively charged substituent on the amide helps stabilize the partial positive charge on the amide nitrogen and consequently more base is required to catalyze proton exchange. The chemical shifts of the -NH protons in Yb-1 and Yb-2 were similar (-17 ppm) while the -NH proton in Yb-3 was at -13 ppm. This shows that the crystal field produced by the amide oxygen donor atoms in Yb-3 is substantially weaker than that in the other two complexes. In an effort to expand the useful range of pH values that might be measured using these complexes as CEST agents, the shapes of the CEST vs pH curves were also determined for two thulium(III) complexes with much larger hyperfine shifted -NH proton resonances. The ratio of CEST from -NH exchange in Tm-1 compared with CEST from -NH exchange in Tm-3 was found to be linear over an extended pH range, from 6.3 to 7.4. This demonstrates a potential advantage of using mixtures of lanthanide(III) DOTA-tetraamides for mapping tissue pH by use of ratiometric CEST imaging.</div></front></TEI></pubmed></double></record>Pour manipuler ce document sous Unix (Dilib)
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