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In-phase/anti-phase ¹H CEST experiments

Files

You can get the example files from the GitHub ChemEx page: backbone and methyl side-chain sites.

This example demonstrates the analysis of datasets from in-phase/anti-phase ¹H CEST experiments, such scheme has been implemented for studying both backbone (cest_1hn_ip_ap) and methyl side-chain (cest_ch3_1h_ip_ap) sites, which has the advantage of fully suppressing artifacts due to NOE effects. The in-phase/anti-phase CEST scheme requires measuring two sets of CEST profiles for two separate spin states and then take subtraction,1,2 an alternative scheme is to start from in-phase magnetization and detect anti-phase magnetization at the end of CEST period.3 These two schemes are equivalent while the latter scheme achieves higher sensitivity and much time-saving, therefore should be preferred.

info

Note that ¹H chemical shifts provided in parameter files should correspond to the "actual" value in the absence of ¹JHN or ¹JHC, therefore a separate experiment that fully suppresses ¹JHN or ¹JHC during final detection might be required to obtain the correct value.

Footnotes​

  1. T. Yuwen, A. Sekhar, and L. E. Kay. Separating Dipolar and Chemical Exchange Magnetization Transfer Processes in 1H‐CEST. Angew. Chem. Int. Ed. 56, 6122-6125 (2017). https://doi.org/10.1002/anie.201610759 ↩

  2. T. Yuwen, R. Huang, and L. E. Kay, Probing Slow Timescale Dynamics in Proteins Using Methyl ¹H CEST. J. Biomol. NMR 68, 215-224 (2017). https://doi.org/10.1007/s10858-017-0121-x ↩

  3. T. Yuwen, and L. E. Kay, A New Class of CEST Experiment Based on Selecting Different Magnetization Components at the Start and End of the CEST Relaxation Element: An Application to ¹H CEST. J. Biomol. NMR 70, 93-102 (2018). https://doi.org/10.1007/s10858-017-0161-2 ↩