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Journal of Biomolecular NMR

, Volume 36, Issue 4, pp 251–257 | Cite as

Sensitivity improvement for correlations involving arginine side-chain Nε/Hε resonances in multi-dimensional NMR experiments using broadband 15N 180° pulses

  • Junji Iwahara
  • G. Marius CloreEmail author
Article

Abstract

Due to practical limitations in available 15N rf field strength, imperfections in 15N 180° pulses arising from off-resonance effects can result in significant sensitivity loss, even if the chemical shift offset is relatively small. Indeed, in multi-dimensional NMR experiments optimized for protein backbone amide groups, cross-peaks arising from the Arg guanidino 15Nε (~85 ppm) are highly attenuated by the presence of multiple INEPT transfer steps. To improve the sensitivity for correlations involving Arg Nε–Hε groups, we have incorporated 15N broadband 180° pulses into 3D 15N-separated NOE-HSQC and HNCACB experiments. Two 15N-WURST pulses incorporated at the INEPT transfer steps of the 3D 15N-separated NOE-HSQC pulse sequence resulted in a ~1.5-fold increase in sensitivity for the Arg Nε–Hε signals at 800 MHz. For the 3D HNCACB experiment, five 15N Abramovich-Vega pulses were incorporated for broadband inversion and refocusing, and the sensitivity of Arg1Hε-15Nε-13Cγ/13Cδ correlation peaks was enhanced by a factor of ~1.7 at 500 MHz. These experiments eliminate the necessity for additional experiments to assign Arg 1Hε and 15Nε resonances. In addition, the increased sensitivity afforded for the detection of NOE cross-peaks involving correlations with the 15Nε/1Hε of Arg in 3D 15N-separated NOE experiments should prove to be very useful for structural analysis of interactions involving Arg side-chains.

Keywords

arginine guanidino group broadband 15N 180 pulse off-resonance pulse imperfection sensitivity improvement 

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Notes

Acknowledgments

This work was supported by funds from the Intramural Program of the NIH, NIDDK and in part by the AIDS Targeted Antiviral program of the Office of the Director of the NIH (to G.M.C.).

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Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  1. 1.Laboratory of Chemical Physics, Building 5, National Institute of Diabetes and Digestive and Kidney DiseaseNational Institutes of HealthBethesdaUSA

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