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Quantitative two-dimensional HSQC experiment for high magnetic field NMR spectrometers
Harri Koskela1, Outi Heikkilä, Ilkka Kilpeläinen
1VERIFIN, University of Helsinki, Helsinki, Finland. Harri.T.Koskela@helsinki.fi
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|October 27, 2009
Summary
Broadband pulses improve quantitative proton-carbon correlation NMR experiments. The novel Q-OCCAHSQC method enhances accuracy, with peak intensity variation below 6% across a wide chemical shift range for high-field NMR magnets.
Area of Science:
- Nuclear Magnetic Resonance (NMR) Spectroscopy
- Analytical Chemistry
- Biophysical Chemistry
Background:
- Proton-carbon correlation experiments in NMR suffer from non-uniform cross-peak intensity due to limited RF power on the carbon channel.
- Broadband pulses, including adiabatic and phase-modulated types, are known to mitigate these intensity variations over a wide spectral range.
- Quantitative analysis in NMR is crucial for accurate metabolite profiling and biomolecular studies.
Purpose of the Study:
- To investigate the efficacy of broadband pulses (adiabatic and phase-modulated) in enhancing quantitative heteronuclear single quantum coherence (HSQC) experiments.
- To evaluate the performance of a novel quantitative, offset-compensated, CPMG-adjusted HSQC (Q-OCCAHSQC) experiment at high magnetic field strengths.
- To demonstrate the application of this improved NMR technique for quantitative analysis of biological samples.
Main Methods:
- Theoretical and experimental evaluation of broadband pulses in quantitative HSQC experiments.
- Implementation and testing of the quantitative, offset-compensated, CPMG-adjusted HSQC (Q-OCCAHSQC) experiment.
- Assessment of peak intensity variations across a wide carbon chemical shift range at 22.3 T.
Main Results:
- The proposed Q-OCCAHSQC experiment demonstrated significant improvements in offset performance.
- (13)C offset-dependent standard deviation of peak intensity was reduced to below 6% within a +/-20 kHz offset range.
- This performance covers approximately 150 ppm of the carbon chemical shift range relevant for protonated carbons (excluding aldehydes) at 22.3 T.
Conclusions:
- Broadband pulses, particularly the Q-OCCAHSQC method, substantially improve the quantitative accuracy of HSQC NMR experiments at high magnetic fields.
- The developed method offers robust quantitative analysis over a broad spectral width, crucial for complex biological samples.
- The study successfully demonstrated the quantitative analysis of a human blood plasma sample, highlighting the practical utility of the technique.
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