期刊
JOURNAL OF MAGNETIC RESONANCE
卷 260, 期 -, 页码 136-143出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jmr.2015.09.010
关键词
Triply compensated pulses; Composite pulses; Genetic algorithm; RF inhomogeneity; zz interactions; Resonance offset; Pulse imperfections
资金
- National Institute of Health [GM 64742, GM 72701]
Sensitivity and resolution in NMR experiments are affected by magnetic field inhomogeneities (of both external and RF), errors in pulse calibration, and offset effects due to finite length of RF pulses. To remedy these problems, built-in compensation mechanisms for these experimental imperfections are often necessary. Here, we propose a new family of phase-modulated constant-amplitude broadband pulses with high compensation for RF inhomogeneity and heteronuclear coupling evolution. These pulses were optimized using a genetic algorithm (GA), which consists in a global optimization method inspired by Nature's evolutionary processes. The newly designed pi and pi/2 pulses belong to the 'type A' (or general rotors) symmetric composite pulses. These GA-optimized pulses are relatively short compared to other general rotors and can be used for excitation and inversion, as well as refocusing pulses in spin-echo experiments. The performance of the GA-optimized pulses was assessed in Magic Angle Spinning (MAS) solid-state NMR experiments using a crystalline U-C-13, N-15 NAVL peptide as well as U-C-13, N-15 microcrystalline ubiquitin. GA optimization of NMR pulse sequences opens a window for improving current experiments and designing new robust pulse sequences. (C) 201 5 Elsevier Inc. All rights reserved.
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