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001-es BibID:	BIBFORM047919
Első szerző:	Mani, Tomoyasu
Cím:	The stereochemistry of amide side chains containing carboxyl groups influences water exchange rates in EuDOTA-tetraamide complexes / Tomoyasu Mani, Ana Christina L. Opina, Piyu Zhao, Osasere M. Evbuomwan, Nate Milburn, Gyula Tircso, Cemile Kumas, A. Dean Sherry
Dátum:	2014
ISSN:	0949-8257
Megjegyzések:	Many Eu(III) complexes formed with DOTAtetraamide ligands (where DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) have sufficiently slow water exchange kinetics to meet the slow-to-intermediate condition required to serve as chemical exchange saturation transfer (CEST) contrast agents for MRI. This class of MRI contrast agents offers an attractive platform for creating biological sensors because water exchange is exquisitelysensitive to subtle ligand stereochemistry and electroniceffects. Introduction of carboxyl groups or carboxyl ethyl ester groups on the amide substituents has been shown to slow water exchange in these complexes, but less is known about the orientation or position of these side-chain groups relativeto the inner-sphere Eu(III)-bound water molecule. In thisstudy, a series of Eu(III) complexes having one or more carboxylgroups or carboxyl esters at the d-position of the pendantamide side chains were prepared. Initial attempts toprepare optically pure EuDOTA-[(S)-Asp]4 resulted in achemically pure ligand consisting of a mixture of stereochemical isomers. This was traced to racemization of (S)-aspartate diethyl ester during the synthetic procedure. Nevertheless, NMR studies of the Eu(III) complexes of this mixture revealed that each isomer had a different water exchange rate, differing by a factor of 2 or more. A second controlled synthesis and CEST study of EuDOTA-[(S)-Asp]4 and cis-EuDOTA-[(S)-Asp]2[(R)-Asp]2 confirmed that the water exchange rates in these diastereomeric complexes are controlled by the axial versus equatorial orientation of the carboxyl groups on the amide side chains. These observations provide new insights toward the development of even more slowly water exchanging systems which will be necessary for practical in vivo applications.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk Lanthanide complexes Macrocyclic conformations MRI contrast agents Water exchange
Megjelenés:	Journal Of Biological Inorganic Chemistry. - 19 (2014), p. 161-171. -
További szerzők:	Opina, Ana Christina L. Zhao, Piyu Evbuomwan, Osasere M. Milburn, Nate Tircsó Gyula (1977-) (vegyész, kémia tanár) Kumas, Cemile Sherry, A. Dean
Pályázati támogatás:	K-84291 OTKA TÁMOP-4.2.2.A-11/1/KONV-2012-0043 TÁMOP
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