jz0c01322_si_001.pdf (2.07 MB)
Multiquantum Chemical Exchange Saturation Transfer NMR to Quantify Symmetrical Exchange: Application to Rotational Dynamics of the Guanidinium Group in Arginine Side Chains
journal contribution
posted on 2020-07-02, 14:15 authored by Gogulan Karunanithy, Jochen Reinstein, D. Flemming HansenChemical exchange
saturation transfer (CEST) NMR experiments have
emerged as a powerful tool for characterizing dynamics in proteins.
We show here that the CEST approach can be extended to systems with
symmetrical exchange, where the NMR signals of all exchanging species
are severely broadened. To achieve this, multiquantum CEST (MQ-CEST)
is introduced, where the CEST pulse is applied to a longitudinal multispin
order density element and the CEST profiles are encoded onto nonbroadened
nuclei. The MQ-CEST approach is demonstrated on the restricted rotation
of guanidinium groups in arginine residues within proteins. These
groups and their dynamics are essential for many enzymes and for noncovalent
interactions through the formation of hydrogen bonds, salt-bridges,
and π-stacking interactions, and their rate of rotation is highly
indicative of the extent of interactions formed. The MQ-CEST method
is successfully applied to guanidinium groups in the 19 kDa L99A mutant
of T4 lysozyme.