000862748 001__ 862748 000862748 005__ 20210130001605.0 000862748 0247_ $$2doi$$a10.1002/mrm.27778 000862748 0247_ $$2ISSN$$a0740-3194 000862748 0247_ $$2ISSN$$a1522-2594 000862748 0247_ $$2altmetric$$aaltmetric:59313246 000862748 0247_ $$2pmid$$apmid:31004385 000862748 0247_ $$2WOS$$aWOS:000485077600007 000862748 0247_ $$2Handle$$a2128/24234 000862748 037__ $$aFZJ-2019-02990 000862748 082__ $$a610 000862748 1001_ $$0P:(DE-HGF)0$$aStabinska, Julia$$b0$$eCorresponding author 000862748 245__ $$aProton exchange in aqueous urea solutions measured by water‐exchange (WEX) NMR spectroscopy and chemical exchange saturation transfer (CEST) imaging in vitro 000862748 260__ $$aNew York, NY [u.a.]$$bWiley-Liss$$c2019 000862748 3367_ $$2DRIVER$$aarticle 000862748 3367_ $$2DataCite$$aOutput Types/Journal article 000862748 3367_ $$0PUB:(DE-HGF)16$$2PUB:(DE-HGF)$$aJournal Article$$bjournal$$mjournal$$s1567760564_26832 000862748 3367_ $$2BibTeX$$aARTICLE 000862748 3367_ $$2ORCID$$aJOURNAL_ARTICLE 000862748 3367_ $$00$$2EndNote$$aJournal Article 000862748 520__ $$aPURPOSE:To characterize the proton exchange in aqueous urea solutions using a modified version of the WEX II filter at high magnetic field, and to assess the feasibility of performing quantitative urea CEST MRI on a 3T clinical MR system.METHODS:In order to study the dependence of the exchange-rate constant ksw of urea as a function of pH and T, the WEX-spectra were acquired at 600 MHz from urea solutions in a pH range from 6.4 to 8.0 and a temperature range from T=22∘C to 37∘C . The CEST experiments were performed on a 3T MRI scanner by applying a train of 50 Gaussian-shaped pulses, each 100-millisecond long with a spacing of 100 milliseconds, for saturation. Exchange rates of urea were calculated using the (extended) AREX metric.RESULTS:The results showed that proton exchange in aqueous urea solutions is acid and base catalyzed with the rate constants: ka=(9.95±1.1)×106 l/(mol·s) and kb=(6.21±0.21)×106 l/(mol·s), respectively. Since the urea protons undergo a slow exchange with water protons, the CEST effect of urea can be observed efficiently at 3T. However, in neutral solutions the exchange rate of urea is minimal and cannot be estimated using the quantitative CEST approach.CONCLUSIONS:By means of the WEX-spectroscopy, the kinetic parameters of the proton exchange in urea solutions have been determined. It was also possible to estimate the exchange rates of urea in a broad range of pH values using the CEST method at a clinical scanner. 000862748 536__ $$0G:(DE-HGF)POF3-551$$a551 - Functional Macromolecules and Complexes (POF3-551)$$cPOF3-551$$fPOF III$$x0 000862748 588__ $$aDataset connected to CrossRef 000862748 7001_ $$0P:(DE-Juel1)144510$$aNeudecker, Philipp$$b1$$ufzj 000862748 7001_ $$0P:(DE-HGF)0$$aLjimani, Alexandra$$b2 000862748 7001_ $$0P:(DE-HGF)0$$aWittsack, Hans‐Jörg$$b3 000862748 7001_ $$0P:(DE-HGF)0$$aLanzman, Rotem Shlomo$$b4 000862748 7001_ $$0P:(DE-HGF)0$$aMüller‐Lutz, Anja$$b5 000862748 773__ $$0PERI:(DE-600)1493786-4$$a10.1002/mrm.27778$$gp. mrm.27778$$n3$$p935-947$$tMagnetic resonance in medicine$$v82$$x1522-2594$$y2019 000862748 8564_ $$uhttps://juser.fz-juelich.de/record/862748/files/Stabinska_et_al-2019-Magnetic_Resonance_in_Medicine.pdf$$yRestricted 000862748 8564_ $$uhttps://juser.fz-juelich.de/record/862748/files/Stabinska_et_al-2019-Magnetic_Resonance_in_Medicine.pdf?subformat=pdfa$$xpdfa$$yRestricted 000862748 8564_ $$uhttps://juser.fz-juelich.de/record/862748/files/Autorenmanuskript%20Proton%20exchange%20in%20aqueous%20urea%20solutions%20measured%20by%20.._.pdf$$yPublished on 2019-04-19. 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