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Related Concept Videos

Double Resonance Techniques: Overview01:12

Double 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...
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals01:17

Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals

Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling interactions can occur between the spins of the unpaired electron and any neighboring spin-active nuclei. This hyperfine coupling results in hyperfine splitting, where the EPR signal is split into multiplets. The signals split into 2nI + 1 peaks, where n is the number of equivalent nuclei and I is the nuclear spin. These splitting patterns provide...
Atomic Nuclei: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
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.

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Related Experiment Video

Updated: Jun 3, 2026

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
11:19

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels

Published on: July 4, 2016

Continuous-wave EPR at 275GHz: application to high-spin Fe(3+) systems.

G Mathies1, H Blok, J A J M Disselhorst

  • 1Department of Molecular Physics, Huygens Laboratory, Leiden University, The Netherlands. mathies@physics.leidenuniv.nl

Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|March 30, 2011
PubMed
Summary

A new probe head enhances electron paramagnetic resonance (EPR) spectrometer sensitivity and signal stability for continuous-wave (CW) operation. This allows for high-quality spectra of iron-containing molecules like rubredoxin, improving zero-field splitting parameter accuracy.

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Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo
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Last Updated: Jun 3, 2026

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Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo
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Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo

Published on: September 26, 2016

Area of Science:

  • Spectroscopy
  • Biophysics
  • Quantum Chemistry

Background:

  • The 275 GHz electron paramagnetic resonance (EPR) spectrometer previously reported requires enhanced performance for continuous-wave (CW) operation.
  • High-sensitivity and stable measurements are crucial for analyzing complex biological samples and metal-containing compounds.

Purpose of the Study:

  • To develop and evaluate a new probe head for a 275 GHz EPR spectrometer to improve CW performance.
  • To demonstrate the enhanced sensitivity and signal stability of the upgraded spectrometer using relevant biological and chemical samples.

Main Methods:

  • Designing and implementing a new probe head with a cavity optimized for CW operation.
  • Acquiring 275 GHz CW EPR spectra of a 1mM frozen solution of Fe(III)-ethylenediamine tetra-acetic acid.
  • Acquiring 275 GHz CW EPR spectra of 10mM frozen solutions of rubredoxin from three different organisms.

Main Results:

  • The new probe head significantly enhances sensitivity and signal stability for 275 GHz CW EPR spectroscopy.
  • High-quality spectra were obtained for Fe(III)-ethylenediamine tetra-acetic acid and rubredoxin samples.
  • Zero-field splitting parameters for rubredoxin were determined with an accuracy of 0.5 GHz.

Conclusions:

  • The upgraded 275 GHz EPR spectrometer with the new probe head achieves superior performance for CW measurements.
  • The enhanced absolute sensitivity from the single-mode cavity and improved signal stability are key to the successful approach.
  • This advancement facilitates more accurate analysis of metalloproteins and other paramagnetic species.