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Computer-generated pulse sequences for 1H-15N and 1Hα-13Cα separated local-field experiments
Joel Lapin1, Alexander A Nevzorov1
1Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, NC 27695-8204, USA.
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|July 28, 2020
Summary
A new computational approach, ROULETTE, optimizes solid-state NMR pulse sequences for sharper 1H-15N and 13C-1H resonances, improving structural determination accuracy.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
- Structural biology and materials science.
Background:
- High-resolution separated local field (SLF) experiments in solid-state NMR are crucial for measuring angular-dependent heteronuclear dipolar couplings, aiding structure determination.
- Traditional analytical methods for designing SLF pulse sequences focus on phase and duration optimization to cancel homonuclear dipolar terms.
- Previous computational approaches, like ROULETTE, showed promise in optimizing linewidths for 1H-15N dipolar resonances using GPU acceleration.
Purpose of the Study:
- To improve the performance of 1H-15N SLF experiments by enhancing the ROULETTE algorithm.
- To extend the de novo optimization approach to new SLF experiments, including 13C-1H.
- To develop more reliable and broadly applicable pulse sequences for structure determination.
Main Methods:
- An improved ROULETTE algorithm was developed, incorporating optimization of radiofrequency irradiation application schemes (on/off) in addition to pulse durations and phases.
- The algorithm performs true de novo optimization, considering all aspects of pulse sequence design.
- The enhanced algorithm was applied to 1H-15N and 13C-1H SLF experiments, utilizing GPU acceleration for spectral simulations.
Main Results:
- A new 1H-15N pulse sequence, ROULETTE-2.0, achieved 32% sharper mean linewidths compared to SAMPI4 for an N-acetyl Leucine (NAL) crystal.
- ROULETTE-2.0 is a windowless pulse sequence, unlike previous methods.
- A new 13C-1H pulse sequence, ROULETTE-CAHA, demonstrated 17% sharper mean linewidths than PISEMA.
- The improved algorithm showed enhanced reliability, reducing false positives.
Conclusions:
- The enhanced ROULETTE algorithm significantly improves the performance of SLF NMR experiments for structure determination.
- The de novo optimization approach is broadly applicable to various NMR experiments and spin systems.
- ROULETTE-2.0 and ROULETTE-CAHA represent advancements in pulse sequence design for solid-state NMR.
Keywords:
AutomationDipolar couplingsGPU computingNMR pulse sequence designPISEMAROULETTESAMPI4Separated local field experimentsSimulated annealingMore Related Videos
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