Improved excitation pulse bandwidths using shaped pulses, with application to heteronuclear half filters in macromolecular NMR.
The advantageous use of sinc-shaped pulses in heteronuclear half filters is explored for studying biological macromolecules. The typical square, or hard, pulse used in half-filter pulse sequences for heteronuclear excitation results in suboptimal suppression of unwanted resonances due to incomplete inversion of spins. The novel use of short-duration shaped pulses applied at high power achieves more uniform excitation profiles over the extended frequency ranges often needed for heteronuclear filtering. This approach is used in the development of a double-tuned omega 1, omega 2-double-half-filtered, double-quantum-filtered COSY experiment. The efficiency of this experiment incorporating sinc pulses compares favorably with that obtained with square pulses in a mixture of 13C-labeled and unlabeled amino acids. Sinc-pulse-filtered spectra of the 24 kDa methionine repressor protein dimer MetJ, uniformly 13C-labeled expect at two unlabeled methionine residues, were also obtained to demonstrate the utility of this approach in biomacromolecular studies.
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Department of Biochemistry, Duke University, Durham, North Caroline 27710, USA.
Spicer
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D001426:Bacterial Proteins / Q000032:analysis; D002247:Carbon Isotopes; D004578:Electron Spin Resonance Spectroscopy; D006639:Histidine / Q000032:analysis; D006859:Hydrogen; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods*; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008715:Methionine / Q000032:analysis; D009587:Nitrogen Isotopes; D012097:Repressor Proteins / Q000032:analysis; D013912:Threonine / Q000032:analysis; D014443:Tyrosine / Q000032:analysis; D014633:Valine / Q000032:analysis
D001426:Bacterial Proteins; D002247:Carbon Isotopes; D046911:Macromolecular Substances; D009587:Nitrogen Isotopes; D012097:Repressor Proteins; C060486:methionine repressor protein, Bacteria; D013912:Threonine; D014443:Tyrosine; D006639:Histidine; D006859:Hydrogen; D008715:Methionine; D014633:Valine