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Updated: Jul 17, 2026

15N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the µs-ms Timescale
Published on: April 19, 2021
Aqueous urea as a model system for bi-exponential relaxation
1Department of Biomedical Engineering, Vanderbilt University School of Engineering, Nashville, TN 37232-2310, USA.
Object:
To evaluate the utility of aqueous urea, doped inner- and outer-sphere relaxation agents, as an adjustable two-component model system.
Materials And Methods:
T2 was measured from 12 molal urea mixtures at pH 7.0 with varying amounts of the MnCl2 and FeO(1.44) (Feridex, Berlex Inc, Montville, NJ).
Results:
Bi-exponential relaxation was observed, with rates that were bilinearly related to [MnCl2] and [FeO(1.44)]. FeO(1.44) had comparable relaxivities on both urea and water, while MnCl2 relaxivity was > 15x larger for water than for urea.
Conclusion:
Aqueous urea, doped with inner- and outer-sphere contrast agents, is a two-compartment model system, which can be exhibit a wide range of different T2s and signal fractions.
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