scholarly journals Unexpected effects of third-order cross-terms in heteronuclear spin systems under simultaneous radio-frequency irradiation and magic-angle spinning NMR

2012 ◽  
Vol 136 (8) ◽  
pp. 084503 ◽  
Author(s):  
Andrew S. Tatton ◽  
Ilya Frantsuzov ◽  
Steven P. Brown ◽  
Paul Hodgkinson
Keyword(s):  
Radio Frequency ◽  
Magic Angle Spinning ◽  
Spin Systems ◽  
Magic Angle ◽  
Third Order ◽  
Cross Terms ◽  
Angle Spinning

scholarly journals Residual dipolar line width in magic-angle spinning proton solid-state NMR

2021 ◽  
Vol 2 (1) ◽  
pp. 499-509
Author(s):  
Matías Chávez ◽  
Thomas Wiegand ◽  
Alexander A. Malär ◽  
Beat H. Meier ◽  
Matthias Ernst
Keyword(s):  
Chemical Shift ◽  
Line Width ◽  
Magic Angle Spinning ◽  
Spin Systems ◽  
Second Order ◽  
Magic Angle ◽  
Line Broadening ◽  
Third Order ◽  
Angle Spinning ◽  
Effective Hamiltonians

Abstract. Magic-angle spinning is routinely used to average anisotropic interactions in solid-state nuclear magnetic resonance (NMR). Due to the fact that the homonuclear dipolar Hamiltonian of a strongly coupled spin system does not commute with itself at different time points during the rotation, second-order and higher-order terms lead to a residual dipolar line broadening in the observed resonances. Additional truncation of the residual broadening due to isotropic chemical-shift differences can be observed. We analyze the residual line broadening in coupled proton spin systems based on theoretical calculations of effective Hamiltonians up to third order using Floquet theory and compare these results to numerically obtained effective Hamiltonians in small spin systems. We show that at spinning frequencies beyond 75 kHz, second-order terms dominate the residual line width, leading to a 1/ωr dependence of the second moment which we use to characterize the line width. However, chemical-shift truncation leads to a partial ωr-2 dependence of the line width which looks as if third-order effective Hamiltonian terms are contributing significantly. At slower spinning frequencies, cross terms between the chemical shift and the dipolar coupling can contribute in third-order effective Hamiltonians. We show that second-order contributions not only broaden the line, but also lead to a shift of the center of gravity of the line. Experimental data reveal such spinning-frequency-dependent line shifts in proton spectra in model substances that can be explained by line shifts induced by the second-order dipolar Hamiltonian.

scholarly journals Residual Linewidth in Magic-Angle Spinning Solid-State NMR

2021 ◽  
Author(s):  
Matías Chávez ◽  
Thomas Wiegand ◽  
Alexander A. Malär ◽  
Beat H. Meier ◽  
Matthias Ernst
Keyword(s):  
Line Width ◽  
Solid State Nmr ◽  
Magic Angle Spinning ◽  
Spin Systems ◽  
Second Order ◽  
Magic Angle ◽  
Line Broadening ◽  
Third Order ◽  
Angle Spinning ◽  
Effective Hamiltonians

Abstract. Magic-angle spinning is routinely used to average anisotropic interactions in solid-state NMR. Due to the fact, that the Hamiltonian of a strongly-coupled spin system does not commute with itself at different time points during the rotation, second-order and higher-order terms lead to a residual line broadening in the observed resonances. Additional truncation of the residual broadening due to isotropic chemical-shift differences can be observed. We analyze the residual line broadening in coupled proton spin systems based on theoretical calculations of effective Hamiltonians up to third order using Floquet theory and compare these results to numerically obtained effective Hamiltonians in small spin systems. We show that at spinning frequencies beyond 50 kHz, second-order terms dominate the residual line width leading to a 1/ωr dependence of the second moment which we use to characterize the line width. However, chemical-shift truncation leads to a partial ωr-2 dependence of the line width which looks as if third-order effective Hamiltonian terms are contributing significantly. We show that second-order contributions not only broaden the line but also lead to a shift of the center of gravity of the line. Experimental data reveals such spinning-frequency dependent line shifts in proton spectra in model substances that can be explained by line shifts induced by the second-order dipolar Hamiltonian.

Numerical Simulation of Magnetic Resonance Experiments: Concepts and Applications to Static, Rotating and Double Rotating Experiments

1994 ◽  
Vol 49 (1-2) ◽  
pp. 80-88 ◽  
Author(s):  
M. Baldus ◽  
T. O. Levante ◽  
B. H. Meier
Keyword(s):  
Numerical Simulation ◽  
Magnetic Resonance ◽  
Object Oriented ◽  
Magic Angle Spinning ◽  
Spin Systems ◽  
Object Oriented Programming ◽  
Time Dependent ◽  
Magic Angle ◽  
Programming Environment ◽  
Angle Spinning

Abstract An object-oriented programming environment for numerical simulation of magnetic resonance spectra is introduced and applied to NQR and NMR of quadrupolar nuclei. Using a Floquet approach it is possible to perform simulations of spin systems that are described by explicitly time-dependent Hamiltonians in full analogy to simulations of time-independent systems. Applications to magic angle spinning and double rotation are discussed.

Heteronuclear and Homonuclear Finite Pulse Radio Frequency Driven Recoupling

2020 ◽  
Author(s):  
Evgeny Nimerovsky ◽  
Kai Xue ◽  
Kumar Tekwani Movellan ◽  
Loren Andreas
Keyword(s):  
Radio Frequency ◽  
Solid State Nmr ◽  
Magnetization Transfer ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Phase Cycling ◽  
The Past ◽  
Pulse Radio ◽  
Dipolar Truncation ◽  
Angle Spinning

Abstract. Homonuclear finite-pulse radio frequency driven recoupling (fp-RFDR) has been broadly used in multi-dimensional magic-angle spinning (MAS) solid-state NMR experiments over the past 20 years. The theoretical and the simulated descriptions of this method were presented during that time, resulting in an understanding of the influence of chemical shift offset, finite pulse effects, and dipolar truncation. Here we present an operator analysis of both heteronuclear and homonuclear fp-RFDR. By numerical simulation, we show which operators are involved in the longitudinal exchange for both heteronuclear and the well-known homonuclear sequences. This results in a better understanding of the influence of phase cycling of the fp-RFDR pulses, which is typically a variant of XY cycling. We investigate the heteronuclear and homonuclear fp-RFDR signals and evolution of the operators through the fp-RFDR block. We show the convergence of the evolutions of the heteronuclear and homonuclear fp-RFDR signals at even numbers of rotor periods and completely different evolution between them. We demonstrate heteronuclear 1H- 13C and 1H-15N fp-RFDR magnetization transfer using a microcrystalline SH3 sample at 100 kHz MAS.

scholarly journals TmDOTP : An NMR- based Thermometer for Magic Angle Spinning NMR Experiments

2019 ◽  
Author(s):  
Dongyu Zhang ◽  
Boris Itin ◽  
Ann E. McDermott
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Radio Frequency ◽  
Solid State Nmr ◽  
Lanthanide Complex ◽  
Magic Angle Spinning ◽  
Sample Temperature ◽  
Proton Spectrum ◽  
Magic Angle ◽  
Angle Spinning

AbstractSolid state NMR is a powerful tool to probe membrane protein structure and motions in native lipid structures. Sample heating, caused by magic angle spinning and radio frequency irradiation in solid state NMR, produces uncertainties in sample temperature and thermal broadening caused by temperature distributions, which can also lead to sample deterioration. To measure the sample temperature in real time, and to quantify thermal gradients and their dependence on radio frequency irradiation or spinning frequency, we use the chemical shift thermometer TmDOTP, a lanthanide complex. Compared to other NMR thermometers (e.g., the proton NMR signal of water), the proton spectrum of TmDOTP exhibits higher thermal sensitivity and resolution. In addition, the H6 proton in TmDOTP has a large chemical shift (−175 ppm at 275 K) and is well resolved from the rest of the proton spectrum. We identified two populations of TmDOTP, with differing temperatures and dependency on the radio frequency irradiation power, within proteoliposome samples. We interpret these populations as arising from the supernatant and the pellet, which is sedimented from the sample spinning. Our results indicate that TmDOTP is an excellent internal standard for monitoring temperatures of biophysically relevant samples without distorting their properties.

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