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Related Concept Videos

2D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)01:19

2D 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...
NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences01:17

NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences

A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.
2D NMR: Overview of Heteronuclear Correlation Techniques01:18

2D 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.
NMR Spectrometers: Overview01:20

NMR Spectrometers: Overview

NMR spectrometers consist of a strong magnet, a radiofrequency transmitter, and a detector attached to a computer console for recording spectra of samples containing NMR-active nuclei. In first-generation NMR instruments called continuous-wave spectrometers, the resonance frequencies of the nuclei are determined by frequency-sweep or field-sweep methods. The magnetic field strength is fixed and the rf signal is swept in the former, while the radiofrequency signal is fixed and the magnetic field...
2D NMR: Overview of Homonuclear Correlation Techniques01:16

2D 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...
High-Resolution Mass Spectrometry (HRMS)01:15

High-Resolution Mass Spectrometry (HRMS)

The resolution of a mass spectrometer depends on the efficiency of separating ions with different ion masses. The mass of an atom is approximated to the sum of the masses of protons and neutrons inside, considering the masses of protons and neutrons as equal. However, the masses of the proton (1.6726 × 10−24 g) and neutron (1.6749 × 10−24 g) are not truly equal. There is a minor error in the expression of atomic masses relative to the simplest atom of hydrogen. For example, the mass of helium...

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Frequency-swept HMQC sequences for high-throughput NMR analysis.

Timothy D Spitzer1, Randy D Rutkowske, George F Dorsey

  • 1GlaxoSmithKline, 5 Moore Drive, Research Triangle Park, NC 27707, USA. timothy.d.spitzer@gsk.com

Magnetic Resonance in Chemistry : MRC
|April 5, 2008
PubMed
Summary
This summary is machine-generated.

New DEPT phase-encoded Heteronuclear Multiple Quantum Coherence (HMQC) experiments offer enhanced sensitivity and robust performance. These advancements utilize frequency-swept pulses for improved signal optimization and accuracy in nuclear magnetic resonance spectroscopy.

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Area of Science:

  • Nuclear Magnetic Resonance (NMR) Spectroscopy
  • Structural Biology
  • Organic Chemistry

Background:

  • The Heteronuclear Multiple Quantum Coherence (HMQC) experiment is a cornerstone technique in NMR spectroscopy for determining molecular structures.
  • Traditional HMQC sequences can suffer from signal loss due to pulse miscalibration and limitations in optimizing for a wide range of coupling constants.
  • Developing more sensitive and robust NMR pulse sequences is crucial for analyzing complex molecules.

Purpose of the Study:

  • To introduce novel versions of the DEPT phase-encoded HMQC experiment.
  • To enhance the performance, sensitivity, and robustness of HMQC experiments.
  • To address signal loss issues associated with pulse miscalibration and optimize signal strength across various heteronuclear coupling constants.

Main Methods:

  • Implementation of frequency-swept proton and carbon pulses within the DEPT phase-encoded HMQC sequence.
  • Inclusion of 'J compensation' to optimize signal intensity over a spectrum of heteronuclear coupling constants.
  • Construction of sequences incorporating both 90-degree and 180-degree frequency-swept pulses.

Main Results:

  • The new sequences demonstrate robust performance and significantly improved sensitivity compared to standard HMQC experiments.
  • Frequency-swept pulses minimize signal loss from miscalibrated pulses, leading to more reliable data.
  • An approximate 10% signal gain was observed compared to well-calibrated hard-pulse experiments due to the combined use of proton and carbon-swept pulses.

Conclusions:

  • The developed DEPT phase-encoded HMQC sequences provide a substantial improvement in sensitivity and robustness for NMR spectroscopy.
  • Frequency-swept pulses effectively mitigate signal loss and optimize signal strength, enhancing the utility of HMQC experiments.
  • These advancements facilitate more accurate and efficient structural elucidation of complex molecules using NMR.