Related Experiment Video
Updated: May 9, 2026
09:55
Troubleshooting and Quality Assurance in Hyperpolarized Xenon Magnetic Resonance Imaging: Tools for High-Quality Image Acquisition
Published on: January 5, 2024
"Perfect echo" HMQC: sensitivity and resolution enhancement by broadband homonuclear decoupling
Bikash Baishya1, C L Khetrapal, Krishna Kishor Dey
1Center of Biomedical Magnetic Resonance, SGPGIMS Campus, Raebareli Road, Lucknow 226 014, India. bikashbaishya@gmail.com
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|July 11, 2013
Summary
This study introduces perfect echo heteronuclear multiple-bond correlation (HMQC) spectroscopy. This new method improves spectral resolution and sensitivity by reducing signal overlap in crowded nuclear magnetic resonance (NMR) spectra.
Area of Science:
- Nuclear Magnetic Resonance (NMR) Spectroscopy
- Organic Chemistry
- Biophysical Chemistry
Background:
- Homonuclear (1)H-(1)H J-modulation causes J-multiplets in 2D (1)H-(13)C HMQC spectra.
- This spectral complexity hinders unambiguous signal assignment in overcrowded (13)C spectra.
Purpose of the Study:
- To develop a method for broadband homonuclear decoupling during the indirect t1 evolution period.
- To enhance resolution and sensitivity in 2D (1)H-(13)C HMQC spectra.
Main Methods:
- Incorporation of perfect echo blocks into the indirect t1 evolution period.
- Application of the perfect echo HMQC (pe-HMQC) method to Cyclosporine.
Main Results:
- The pe-HMQC method demonstrated improved resolution and sensitivity compared to conventional HMQC.
- Efficient refocusing of geminal couplings in -(13)CH2 groups was observed.
- Partial refocusing of vicinal couplings in -(13)CH and -(13)CH3 groups was also achieved.
- F1 linewidths in pe-HMQC were significantly narrower than HMQC and comparable to HSQC for CH2 groups.
Conclusions:
- The perfect echo HMQC technique effectively reduces spectral crowding and improves signal assignment in NMR.
- This method offers a valuable advancement for analyzing complex organic molecules like Cyclosporine.
Related Concept Videos
01:12Double Resonance Techniques: Overview
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Spin decoupling is usually achieved by...
01:182D NMR: Overview of Heteronuclear Correlation Techniques
Heteronuclear correlation spectroscopy is an analytical technique that investigates the coupling between different types of nuclei, often a proton and an X-nucleus, such as carbon-13 or nitrogen-15. This method is commonly used in nuclear magnetic resonance (NMR) spectroscopy to gain insights into complex chemical compounds' structural and compositional aspects. A typical heteronuclear correlation spectrum displays X-nucleus chemical shifts on one axis and a proton spectrum on the other axis.
01:162D NMR: Overview of Homonuclear Correlation Techniques
Homonuclear correlation spectroscopy (COSY) is a powerful technique used in Nuclear Magnetic Resonance (NMR) spectroscopy to study the correlations between nuclei of the same type within a molecule. It provides information about scalar couplings between adjacent nuclei, which helps determine connectivity and structural information. There are several COSY variants, each with its unique strengths and experimental parameters.
COSY90 is the standard two-dimensional (2D) COSY experiment that...
COSY90 is the standard two-dimensional (2D) COSY experiment that...
01:04¹³C NMR: ¹H–¹³C Decoupling
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
01:192D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)
Heteronuclear single-quantum correlation spectroscopy (HSQC) is a 2D NMR technique that reveals one-bond correlations between hydrogen and a heteronucleus. The HSQC experiment is similar to the heteronuclear correlation experiment (HETCOR) but is more sensitive. In the HSQC spectrum, the proton chemical shift is plotted on the horizontal F2 axis, while the 13C chemical shift is plotted on the vertical F1 axis. The corresponding proton and 13C spectra are also shown. The HSQC contour plot does...
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...