scholarly journals Analysis of conformational exchange processes using methyl-TROSY-based Hahn echo measurements of quadruple-quantum relaxation

2021 ◽  
Vol 2 (2) ◽  
pp. 777-793
Author(s):  
Christopher A. Waudby ◽  
John Christodoulou
Keyword(s):  
Chemical Shift ◽  
Chemical Exchange ◽  
Relaxation Dispersion ◽  
Conformational Exchange ◽  
Parameter Estimates ◽  
Relaxation Rates ◽  
Exchange Processes ◽  
Methyl Trosy ◽  
Quantum Transitions ◽  
Order Of Magnitude

Abstract. Transverse nuclear spin relaxation is a sensitive probe of chemical exchange on timescales on the order of microseconds to milliseconds. Here we present an experiment for the simultaneous measurement of the relaxation rates of two quadruple-quantum transitions in 13CH3-labelled methyl groups. These coherences are protected against relaxation by intra-methyl dipolar interactions and so have unexpectedly long lifetimes within perdeuterated biomacromolecules. However, these coherences also have an order of magnitude higher sensitivity to chemical exchange broadening than lower order coherences and therefore provide ideal probes of dynamic processes. We show that analysis of the static magnetic field dependence of zero-, double- and quadruple-quantum Hahn echo relaxation rates provides a robust indication of chemical exchange and can determine the signed relative magnitudes of proton and carbon chemical shift differences between ground and excited states. We also demonstrate that this analysis can be combined with established Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion measurements, providing improved precision in parameter estimates, particularly in the determination of 1H chemical shift differences.

scholarly journals Analysis of Conformational Exchange Processes using Methyl-TROSY-Based Hahn Echo Measurements of Quadruple-Quantum Relaxation

2021 ◽  
Author(s):  
Christopher Andrew Waudby ◽  
John Christodoulou
Keyword(s):  
Chemical Shift ◽  
Chemical Exchange ◽  
Relaxation Dispersion ◽  
Conformational Exchange ◽  
Parameter Estimates ◽  
Relaxation Rates ◽  
Exchange Processes ◽  
Methyl Trosy ◽  
Quantum Transitions ◽  
Order Of Magnitude

Abstract. Transverse nuclear spin relaxation is a sensitive probe of chemical exchange on timescales on the order of microseconds to milliseconds. Here we present an experiment for the simultaneous measurement of the relaxation rates of two quadruple-quantum transitions in 13CH3-labelled methyl groups. These coherences are protected against relaxation by intra-methyl dipolar interactions, and so have unexpectedly long lifetimes within perdeuterated biomacromolecules. However, these coherences also have an order of magnitude higher sensitivity to chemical exchange broadening than lower order coherences, and therefore provide ideal probes of dynamic processes. We show that analysis of the static magnetic field dependence of zero-, double- and quadruple-quantum Hahn echo relaxation rates provides a robust indication of chemical exchange, and can determine the signed relative magnitudes of proton and carbon chemical shift differences between ground and excited states. We also demonstrate that this analysis can be combined with established CPMG relaxation dispersion measurements, providing improved precision in parameter estimates, particularly in the determination of 1H chemical shift differences.

scholarly journals Analysis of Conformational Exchange Processes using Methyl-TROSY-Based Hahn Echo Measurements of Quadruple-Quantum Relaxation

2021 ◽  
Author(s):  
Christopher Andrew Waudby ◽  
John Christodoulou
Keyword(s):  
Chemical Shift ◽  
Excited States ◽  
Chemical Exchange ◽  
Relaxation Dispersion ◽  
Conformational Exchange ◽  
Nuclear Spin Relaxation ◽  
Relaxation Rates ◽  
Exchange Processes ◽  
Methyl Trosy

Transverse nuclear spin relaxation can be a sensitive probe of chemical exchange on timescales on the order of microseconds to milliseconds. Here we present an experiment for the simultaneous measurement of the relaxation rates of two four-spin transitions in selectively protonated methyl groups within perdeuterated biomacromolecules, alongside control experiments for measurement of 1H and 13C chemical shift anisotropies. We show that analysis of the static magnetic field dependence of zero-, double- and quadruple-quantum Hahn echo relaxation rates provides a robust indication of chemical exchange and determines the signed relative magnitudes of proton and carbon chemical shift differences between ground and excited states. The analysis can be combined with CPMG relaxation dispersion measurements to provide improved precision, particularly in the determination of 1H chemical shift differences.

A Methyl‐TROSY‐Based 1 H Relaxation Dispersion Experiment for Studies of Conformational Exchange in High Molecular Weight Proteins

2019 ◽  
Vol 131 (19) ◽  
pp. 6316-6320
Author(s):  
Tairan Yuwen ◽  
Rui Huang ◽  
Pramodh Vallurupalli ◽  
Lewis E. Kay
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Relaxation Dispersion ◽  
Conformational Exchange ◽  
Methyl Trosy ◽  
High Molecular Weight Proteins

Enhancing the Sensitivity of CPMG Relaxation Dispersion to Conformational Exchange Processes by Multiple-Quantum Spectroscopy

2016 ◽  
Vol 128 (38) ◽  
pp. 11662-11666 ◽  
Author(s):  
Tairan Yuwen ◽  
Pramodh Vallurupalli ◽  
Lewis E. Kay
Keyword(s):  
Relaxation Dispersion ◽  
Conformational Exchange ◽  
Multiple Quantum ◽  
Exchange Processes ◽  
Cpmg Relaxation Dispersion

scholarly journals Cross-Peaks in Simple 2D NMR Experiments from Chemical Exchange of Transverse Magnetization

2019 ◽  
Author(s):  
Chris Waudby ◽  
Tom Frenkiel ◽  
John Christodoulou
Keyword(s):  
Chemical Shift ◽  
Chemical Exchange ◽  
Exchange Process ◽  
2D Nmr ◽  
Two Dimensional ◽  
One Dimensional ◽  
Exchange Processes ◽  
Rich Information ◽  
Multiple Chemical

Two-dimensional correlation measurements such as COSY, NOESY, HMQC and HSQC experiments are central to small molecule and biomolecular NMR spectroscopy, and commonly form the basis of more complex experiments designed to study chemical exchange occurring during additional mixing periods. However, exchange occurring during chemical shift evolution periods can also influence the appearance of such spectra. While this is often exploited through one-dimensional lineshape analysis ('dynamic NMR'), the analysis of exchange across multiple chemical shift evolution periods has received less attention. Here we report that chemical exchange-induced cross-peaks can arise in even the simplest two-dimensional NMR experiments. These cross-peaks can have highly distorted phases that contain rich information about the underlying exchange process. The quantitative analysis of such peaks, from a single 2D spectrum, can provide a highly accurate characterization of underlying exchange processes.

scholarly journals 1H R1ρ relaxation dispersion experiments in aromatic side chains

2021 ◽  
Author(s):  
Matthias Dreydoppel ◽  
Roman J. Lichtenecker ◽  
Mikael Akke ◽  
Ulrich Weininger
Keyword(s):  
Chemical Shift ◽  
Active Sites ◽  
Isotope Labeling ◽  
Relaxation Dispersion ◽  
Conformational Exchange ◽  
Side Chains ◽  
Transverse Relaxation Rate ◽  
Spin Lock ◽  
Spin Pairs ◽  
Aromatic Side Chains

AbstractAromatic side chains are attractive probes of protein dynamic, since they are often key residues in enzyme active sites and protein binding sites. Dynamic processes on microsecond to millisecond timescales can be studied by relaxation dispersion experiments that attenuate conformational exchange contributions to the transverse relaxation rate by varying the refocusing frequency of applied radio-frequency fields implemented as either CPMG pulse trains or continuous spin-lock periods. Here we present an aromatic 1H R1ρ relaxation dispersion experiment enabling studies of two to three times faster exchange processes than achievable by existing experiments for aromatic side chains. We show that site-specific isotope labeling schemes generating isolated 1H–13C spin pairs with vicinal 2H–12C moieties are necessary to avoid anomalous relaxation dispersion profiles caused by Hartmann–Hahn matching due to the 3JHH couplings and limited chemical shift differences among 1H spins in phenylalanine, tyrosine and the six-ring moiety of tryptophan. This labeling pattern is sufficient in that remote protons do not cause additional complications. We validated the approach by measuring ring-flip kinetics in the small protein GB1. The determined rate constants, kflip, agree well with previous results from 13C R1ρ relaxation dispersion experiments, and yield 1H chemical shift differences between the two sides of the ring in good agreement with values measured under slow-exchange conditions. The aromatic1H R1ρ relaxation dispersion experiment in combination with the site-selective 1H–13C/2H–12C labeling scheme enable measurement of exchange rates up to kex = 2kflip = 80,000 s–1, and serve as a useful complement to previously developed 13C-based methods.

scholarly journals Revisiting paramagnetic relaxation enhancements in slowly rotating systems: how long is the long range?

2020 ◽  
Author(s):  
Giovanni Bellomo ◽  
Enrico Ravera ◽  
Vito Calderone ◽  
Mauro Botta ◽  
Marco Fragai ◽  
...  
Keyword(s):  
Chemical Exchange ◽  
Protein Structure Determination ◽  
Bulk Water ◽  
Water Proton ◽  
Proton Relaxation ◽  
Relaxation Rates ◽  
Rotating Systems ◽  
Complete Relaxation ◽  
Nuclear Magnetization ◽  
Order Of Magnitude

Abstract. Cross relaxation terms in paramagnetic systems that reorient rigidly with slow tumbling times can increase the effective longitudinal relaxation rates of protons of more than one order of magnitude. This is evaluated by simulating the time evolution of the nuclear magnetization using a complete relaxation matrix approach. The calculations show that the Solomon dependence of the relaxation rates on the metal-proton distance (as r−6) can be incorrect for protons farther than 15 Å from the metal, and thus can originate sizable errors in R1-derived distance restraints used, for instance, for protein structure determination. Furthermore, the chemical exchange of these protons with bulk water protons can enhance the relaxation rate of the solvent protons by far more than expected from the Solomon equation. Therefore, it may contribute significantly to the water proton relaxation rates measured at MRI magnetic fields in the presence of slow-rotating nanoparticles containing paramagnetic ions and a large number of exchangeable surface protons.

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