Relaxation Dispersion NMR Spectroscopy

Multiquantum Chemical Exchange Saturation Transfer NMR to Quantify Symmetrical Exchange: Application to Rotational Dynamics of the Guanidinium Group in Arginine Side Chains

“… 1 , 2 A number of NMR-based approaches for characterizing exchange on these time scales now exist and provide important insights into conformations that are transiently populated, invisible to other high-resolution methods, and also broadened beyond detection in traditional NMR experiments. 3 − 6 Although chemical exchange saturation transfer (CEST) methods have traditionally been used within the MRI field, 7 − 9 CEST approaches have recently emerged as powerful tools also for studying biomolecular dynamics on a time scale from 20 to 200 s –1 . 10 , 11 In these experiments, first developed in the 1960s, 12 saturation of magnetization by a weak pulse is transferred by exchange events within a network of exchanging conformers, and in particular, magnetization is transferred from invisible species to visible species in order to report on chemical shifts and rates of exchange.…”

Rapid Determination of Fast Protein Dynamics from NMR Chemical Exchange Saturation Transfer Data

“…[4] CEST reports on the presence of such ‘excited’ protein states indirectly by measuring the signal of a ground-state resonance in the presence of a variable-offset radio-frequency (rf) B 1 saturation field. When the B 1 field is applied at the frequency of the excited state resonance, saturation is transferred to the ground state via the exchange process(es), which is manifested as a dip in the CEST intensity profile from which kinetic rates ( k ab + k ba = k ex ) together with the population of the excited state (p b ) and its chemical shift can be extracted.…”

A two-dimensional replica-exchange molecular dynamics method for simulating RNA folding using sparse experimental restraints

“…To rule out the R 2 contribution to R 2eff , and obtain information on the exchange process, a train of spin echo pulses can be applied with variable frequency (υ CPMG ) and a relaxation dispersion curve is obtained by plotting R 2eff as a function of υ CPMG . Subsequent deconvolution of exchange parameters (k EX , populations and Δ Ω ) requires collection of datasets at different B 0 fields and solution of analytical expression derived from the Bloch-McConnel equations 109,117 . Due to the nature of 180° pulses, typical schemes to avoid spectroscopic artifacts cannot be implemented in CPMG experiments, making the analysis of RNAs particularly challenging 109 .…”