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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
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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001-es BibID:	BIBFORM010526
Első szerző:	Mani, Tomoyasu
Cím:	Modulation of water exchange in Eu(III) DOTA-tetraamide complexes : considerations for in vivo imaging of PARACEST agents / Tomoyasu Mani, Gyula Tircsó, Osamu Togao, Piyu Zhao, Todd C. Soesbe, Masaya Takahashi, A. Dean Sherry
Dátum:	2009
ISSN:	1555-4309
Megjegyzések:	Modulation of water exchange in lanthanide(III)-DOTA type complexes has drawn considerable attention over the past two decades, particularly because of their application as contrast agents for magnetic resonance imaging. LnDOTA-tetraamide complexes display unusually slow water exchange kinetics and this chemical property offers an opportunity to use these complexes as a new type of contrast agent based upon the chemical exchange saturation transfer (CEST) mechanism. Six new DOTA-tetraamide ligands having side-chain amide arms with varying hydrophobicity and polarity were prepared and the water exchange characteristic of complexes formed with europium(III) complexes were investigated. The results show that introduction of steric bulk into the amide side-chain arms of the europium(III) complexes not only favors formation of the mono-capped twisted square antiprism coordination isomers, the isomer that is generally less favourable for CEST, but also accelerates water exchange in the mono-capped square antiprism isomers. However, converting single methyl groups on these bulky arms to carboxyl or carboxyl ethyl esters results in a rather dramatic decrease in water exchange rates, about 50-fold. Thus, steric bulk, polarity and hydrophobicity of the amide side-chains each contribute to organization of water molecules in the second hydration sphere of the europium(III) ion and this in turn controls water exchange in these complexes. Copyright (C) 2009 John Wiley & Sons, Ltd.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Contrast Media & Molecular Imaging. - 4 : 4 (2009), p. 183-191. -
További szerzők:	Tircsó Gyula (1977-) (vegyész, kémia tanár) Togao, Osamu Zhao, Piyu Soesbe, Todd C. Takahashi, Masaya Sherry, A. Dean
Internet cím:	DOI Intézményi repozitóriumban (DEA) tárolt változat
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001-es BibID:	BIBFORM010527
Első szerző:	Mani, Tomoyasu
Cím:	Effect of the Regiochemistry of Butyl Amide Substituents on the Solution-State Structures of Lanthanide(III) DOTA-Tetraamide Complexes / Tomoyasu Mani, Gyula Tircsó, Piyu Zhao, A. Dean Sherry, Mark Woods
Dátum:	2009
ISSN:	0020-1669
Megjegyzések:	The coordination geometry adopted by the lanthanide complexes of DOTA-tetraamides is a critical factor in determining their water exchange kinetics. Controlling the water exchange kinetics of DOTA-tetraamide complexes, and by extension their coordination geometry, is of particular interest because of the potential application of this class of complex as PARACEST MRI contrast agents. To facilitate the maximum CEST effect at the lowest pre-saturation powers much slower exchange kinetics are required than are commonly observed with these types of chelates. Complexes that adopt the more slowly exchanging square antiprismatic coordination geometry are therefore preferred; however, the factors that govern which coordination geometry is preferred remain unclear. A series of DOTA-tetraamide complexes with butyl amide substituents in different regioisomeric configurations provides some insight into these factors. The population of each coordination geometry was found to vary substantially depending, upon the regiochemistry of the butyl amide substituent. It was observed that the twisted square antiprism coordiniition geometry, usually favored in complexes with the larger lanthanide ions only, is also increasingly favored for certain DOTA-tetraamide complexes with the smaller lanthanides. This is in marked contrast to simple DOTA-tetraamide complexes such as DOTAM. The effect was more prevalent in complexes formed with more bulky and more electron donating amide butyl substituents. It is also associated with loss of an inner-sphere water molecule from the complexes of later lanthanides that adopt the twisted square antiprismatic geometry. The complexes with sec-butyl substituents are inherently more complicated because of the introduction of a stereochemical center into each pendant arm. Unlike chiral complexes with larger amide substituents there is no "locking" effect of the orientation of the pendant arms in these complexes and up to four diastereoisomeric coordination isomers can be observed.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Inorganic Chemistry. - 48 : 21 (2009), p. 10338-10345. -
További szerzők:	Tircsó Gyula (1977-) (vegyész, kémia tanár) Zhao, Piyu Sherry, A. Dean Woods, Mark
Internet cím:	DOI Intézményi repozitóriumban (DEA) tárolt változat
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