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¹Hᴺ COS-CEST experiment

Files

You can get the example files from the GitHub ChemEx page.

This example demonstrates the analysis of datasets from ¹Hᴺ COS-CEST experiment (coscest_1hn_ip_ap, which is based on in-phase/anti-phase scheme while the excitation element is replaced with cos-modulated excitation fields. Similar to D-CEST scheme, COS-CEST performs multiple excitations, leading to significant time-savings compared to regular CEST. Cos-modulated excitation fields offer some advantages over the DANTE sequence in systems where the probe spins in question are dipolar or scalar coupled to like spins that can therefore be simultaneously perturbed by the broad-banded nature of the DANTE element. An important application is ¹Hᴺ COS-CEST for the study of slow chemical exchange processes in fully protonated proteins.1

info

Since COS-CEST requires numerical integration for cos-shaped pulses with multiple time steps, the fitting speed could be much slower than other experiment modules. The cos_res key in experiment files should not be set too large, and typically should be much smaller than actually used experimentally so long as reasonable fitting results can be achieved. Similar to the requirement in other in-phase/anti-phase CEST experiments, ¹H chemical shifts provided in parameter files should correspond to the "actual" value in the absence of ¹JHN.

Footnotes​

  1. T. Yuwen, G. Bouvignies, and L. E. Kay. Exploring Methods to Expedite the Recording of CEST Datasets Using Selective Pulse Excitation J. Magn. Reson. 292, 1-7 (2018). https://doi.org/10.1016/j.jmr.2018.04.013 ↩