The presence of fast-exchanging proton species in aqueous solutions of paraCEST Agents can impact rate constants measured for slower exchanging species when fitting CEST spectra to the bloch equations

Osasere M. Evbuomwan, Joohwan Lee, Mark Woods, A. Dean Sherry

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

LnDOTA-tetraamide complexes typically exist in solution as a mixture of square-antiprismatic (SAP) and twisted square-antiprismatic (TSAP) coordination isomers. In most cases, the SAP isomer, which is preferred for CEST imaging, predominates, and the presence of the minor TSAP isomer is assumed to have little influence on quantitative measures of the water-exchange rate constant for the SAP isomer. Here, we sought to confirm the validity of this assumption by mixing two chelates with different SAP and TSAP isomer populations while measuring the water-exchange rate constant of the SAP isomer. The results show that an increase in the population of the TSAP isomer in solution results in as much as a 30% overestimation of the water-exchange rate constant for the SAP isomer when CEST spectra are fit to the Bloch equations. This effect was shown to be significant only when the TSAP isomer population exceeded 50%.

Original languageEnglish (US)
Pages (from-to)10012-10014
Number of pages3
JournalInorganic Chemistry
Volume53
Issue number19
DOIs
StatePublished - Oct 6 2014

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exchanging
Isomers
Protons
Rate constants
isomers
aqueous solutions
protons
Water
Population
water
chelates
Imaging techniques

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Medicine(all)

Cite this

The presence of fast-exchanging proton species in aqueous solutions of paraCEST Agents can impact rate constants measured for slower exchanging species when fitting CEST spectra to the bloch equations. / Evbuomwan, Osasere M.; Lee, Joohwan; Woods, Mark; Sherry, A. Dean.

In: Inorganic Chemistry, Vol. 53, No. 19, 06.10.2014, p. 10012-10014.

Research output: Contribution to journalArticle

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abstract = "LnDOTA-tetraamide complexes typically exist in solution as a mixture of square-antiprismatic (SAP) and twisted square-antiprismatic (TSAP) coordination isomers. In most cases, the SAP isomer, which is preferred for CEST imaging, predominates, and the presence of the minor TSAP isomer is assumed to have little influence on quantitative measures of the water-exchange rate constant for the SAP isomer. Here, we sought to confirm the validity of this assumption by mixing two chelates with different SAP and TSAP isomer populations while measuring the water-exchange rate constant of the SAP isomer. The results show that an increase in the population of the TSAP isomer in solution results in as much as a 30{\%} overestimation of the water-exchange rate constant for the SAP isomer when CEST spectra are fit to the Bloch equations. This effect was shown to be significant only when the TSAP isomer population exceeded 50{\%}.",
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AU - Sherry, A. Dean

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N2 - LnDOTA-tetraamide complexes typically exist in solution as a mixture of square-antiprismatic (SAP) and twisted square-antiprismatic (TSAP) coordination isomers. In most cases, the SAP isomer, which is preferred for CEST imaging, predominates, and the presence of the minor TSAP isomer is assumed to have little influence on quantitative measures of the water-exchange rate constant for the SAP isomer. Here, we sought to confirm the validity of this assumption by mixing two chelates with different SAP and TSAP isomer populations while measuring the water-exchange rate constant of the SAP isomer. The results show that an increase in the population of the TSAP isomer in solution results in as much as a 30% overestimation of the water-exchange rate constant for the SAP isomer when CEST spectra are fit to the Bloch equations. This effect was shown to be significant only when the TSAP isomer population exceeded 50%.

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