Genetic algorithm optimized triply compensated pulses in NMR spectroscopy

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9 Scopus citations

Abstract

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 π and π/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-13C, 15N NAVL peptide as well as U-13C, 15N microcrystalline ubiquitin. GA optimization of NMR pulse sequences opens a window for improving current experiments and designing new robust pulse sequences.

Original languageEnglish (US)
Pages (from-to)136-143
Number of pages8
JournalJournal of Magnetic Resonance
Volume260
DOIs
StatePublished - Nov 1 2015

Bibliographical note

Funding Information:
This research is supported by the National Institute of Health GM 64742 and GM 72701 to G.V. The authors would like to thank Dr. T. Gopinath for critical reading of the manuscript. The MATLAB® routine to find the 99fidelity rectangle and the pulse shapes are available at http://www.chem.umn.edu/groups/veglia/downloads.htm .

Keywords

  • Composite pulses
  • Genetic algorithm
  • Pulse imperfections
  • RF inhomogeneity
  • Resonance offset
  • Triply compensated pulses
  • zz interactions

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