Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate
Autor(a) principal: | |
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Data de Publicação: | 2006 |
Outros Autores: | , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10316/8120 https://doi.org/10.1002/chem.200500551 |
Resumo: | We report the synthesis and characterization of the novel ligand H5EPTPA-C16 ((hydroxymethylhexadecanoyl ester)ethylenepropylenetriaminepentaacetic acid). This ligand was designed to chelate the GdIII ion in a kinetically and thermodynamically stable way while ensuring an increased water exchange rate (kex) on the GdIII complex owing to steric compression around the water-binding site. The attachment of a palmitic ester unit to the pendant hydroxymethyl group on the ethylenediamine bridge yields an amphiphilic conjugate that forms micelles with a long tumbling time (tauR) in aqueous solution. The critical micelle concentration (cmc = 0.34 mM) of the amphiphilic [Gd(eptpa-C16)(H2O)]2- chelate was determined by variable-concentration proton relaxivity measurements. A global analysis of the data obtained in variable-temperature and multiple-field 17O NMR and 1H NMRD measurements allowed for the determination of parameters governing relaxivity for [Gd(eptpa-C16)(H2O)]2-; this is the first time that paramagnetic micelles with optimized water exchange have been investigated. The water exchange rate was found to be = 1.7×108 s-1, very similar to that previously reported for the nitrobenzyl derivative [Gd(eptpa-bz-NO2)(H2O)]2- ( = 1.5×108 s-1). The rotational dynamics of the micelles were analysed by using the Lipari-Szabo approach. The micelles formed in aqueous solution show considerable flexibility, with a local rotational correlation time of = 330 ps for the GdIII segments, which is much shorter than the global rotational correlation time of the supramolecular aggregates, = 2100 ps. This internal flexibility of the micelles is responsible for the limited increase of the proton relaxivity observed on micelle formation (r1 = 22.59 mM-1 s-1 for the micelles versus 9.11 mM-1 s-1 for the monomer chelate (20 MHz; 25 °C)). |
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Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange RateWe report the synthesis and characterization of the novel ligand H5EPTPA-C16 ((hydroxymethylhexadecanoyl ester)ethylenepropylenetriaminepentaacetic acid). This ligand was designed to chelate the GdIII ion in a kinetically and thermodynamically stable way while ensuring an increased water exchange rate (kex) on the GdIII complex owing to steric compression around the water-binding site. The attachment of a palmitic ester unit to the pendant hydroxymethyl group on the ethylenediamine bridge yields an amphiphilic conjugate that forms micelles with a long tumbling time (tauR) in aqueous solution. The critical micelle concentration (cmc = 0.34 mM) of the amphiphilic [Gd(eptpa-C16)(H2O)]2- chelate was determined by variable-concentration proton relaxivity measurements. A global analysis of the data obtained in variable-temperature and multiple-field 17O NMR and 1H NMRD measurements allowed for the determination of parameters governing relaxivity for [Gd(eptpa-C16)(H2O)]2-; this is the first time that paramagnetic micelles with optimized water exchange have been investigated. The water exchange rate was found to be = 1.7×108 s-1, very similar to that previously reported for the nitrobenzyl derivative [Gd(eptpa-bz-NO2)(H2O)]2- ( = 1.5×108 s-1). The rotational dynamics of the micelles were analysed by using the Lipari-Szabo approach. The micelles formed in aqueous solution show considerable flexibility, with a local rotational correlation time of = 330 ps for the GdIII segments, which is much shorter than the global rotational correlation time of the supramolecular aggregates, = 2100 ps. This internal flexibility of the micelles is responsible for the limited increase of the proton relaxivity observed on micelle formation (r1 = 22.59 mM-1 s-1 for the micelles versus 9.11 mM-1 s-1 for the monomer chelate (20 MHz; 25 °C)).2006info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articlehttp://hdl.handle.net/10316/8120http://hdl.handle.net/10316/8120https://doi.org/10.1002/chem.200500551engChemistry - A European Journal. 12:3 (2006) 940-948Torres, SusanaMartins, José A.André, João P.Geraldes, Carlos F. G. C.Merbach, André E.Tóth, Évainfo:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2020-05-25T07:14:59Zoai:estudogeral.uc.pt:10316/8120Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T20:55:44.865309Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate |
title |
Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate |
spellingShingle |
Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate Torres, Susana |
title_short |
Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate |
title_full |
Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate |
title_fullStr |
Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate |
title_full_unstemmed |
Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate |
title_sort |
Supramolecular Assembly of an Amphiphilic GdIII Chelate: Tuning the Reorientational Correlation Time and the Water Exchange Rate |
author |
Torres, Susana |
author_facet |
Torres, Susana Martins, José A. André, João P. Geraldes, Carlos F. G. C. Merbach, André E. Tóth, Éva |
author_role |
author |
author2 |
Martins, José A. André, João P. Geraldes, Carlos F. G. C. Merbach, André E. Tóth, Éva |
author2_role |
author author author author author |
dc.contributor.author.fl_str_mv |
Torres, Susana Martins, José A. André, João P. Geraldes, Carlos F. G. C. Merbach, André E. Tóth, Éva |
description |
We report the synthesis and characterization of the novel ligand H5EPTPA-C16 ((hydroxymethylhexadecanoyl ester)ethylenepropylenetriaminepentaacetic acid). This ligand was designed to chelate the GdIII ion in a kinetically and thermodynamically stable way while ensuring an increased water exchange rate (kex) on the GdIII complex owing to steric compression around the water-binding site. The attachment of a palmitic ester unit to the pendant hydroxymethyl group on the ethylenediamine bridge yields an amphiphilic conjugate that forms micelles with a long tumbling time (tauR) in aqueous solution. The critical micelle concentration (cmc = 0.34 mM) of the amphiphilic [Gd(eptpa-C16)(H2O)]2- chelate was determined by variable-concentration proton relaxivity measurements. A global analysis of the data obtained in variable-temperature and multiple-field 17O NMR and 1H NMRD measurements allowed for the determination of parameters governing relaxivity for [Gd(eptpa-C16)(H2O)]2-; this is the first time that paramagnetic micelles with optimized water exchange have been investigated. The water exchange rate was found to be = 1.7×108 s-1, very similar to that previously reported for the nitrobenzyl derivative [Gd(eptpa-bz-NO2)(H2O)]2- ( = 1.5×108 s-1). The rotational dynamics of the micelles were analysed by using the Lipari-Szabo approach. The micelles formed in aqueous solution show considerable flexibility, with a local rotational correlation time of = 330 ps for the GdIII segments, which is much shorter than the global rotational correlation time of the supramolecular aggregates, = 2100 ps. This internal flexibility of the micelles is responsible for the limited increase of the proton relaxivity observed on micelle formation (r1 = 22.59 mM-1 s-1 for the micelles versus 9.11 mM-1 s-1 for the monomer chelate (20 MHz; 25 °C)). |
publishDate |
2006 |
dc.date.none.fl_str_mv |
2006 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10316/8120 http://hdl.handle.net/10316/8120 https://doi.org/10.1002/chem.200500551 |
url |
http://hdl.handle.net/10316/8120 https://doi.org/10.1002/chem.200500551 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
Chemistry - A European Journal. 12:3 (2006) 940-948 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.source.none.fl_str_mv |
reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
instname_str |
Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
instacron_str |
RCAAP |
institution |
RCAAP |
reponame_str |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
collection |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
repository.name.fl_str_mv |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
repository.mail.fl_str_mv |
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1799133843783942144 |