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Related Concept Videos

¹H NMR: Complex Splitting01:13

¹H NMR: Complex Splitting

A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
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...
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
Interpreting ¹H NMR Signal Splitting: The (n + 1) Rule01:10

Interpreting ¹H NMR Signal Splitting: The (n + 1) Rule

In the AX proton spin system, proton A can sense the two spin states of a coupled proton X, resulting in a doublet NMR signal with two peaks of equal (1:1) intensity. When proton A is coupled to two equivalent protons (AX2 spin system), the spin states of each X can be aligned with or against the external field, creating three possible scenarios. This results in a 1:2:1  triplet signal, where the central peak corresponds to the chemical shift of A and is twice as large or intense as the others.
¹H NMR Signal Multiplicity: Splitting Patterns01:13

¹H NMR Signal Multiplicity: Splitting Patterns

When protons A and X are coupled, their nuclear spin energy levels are slightly modified. This is because the energy required to excite proton A to a spin state parallel to proton X is slightly different from the energy required for it to become anti-parallel to spin X. Consequently, there are two possible excitation frequencies for A (A1 and A2), depending on the spin state of X, and vice versa. The mutual nature of coupling implies that the difference between frequencies A1 and A2, indicated...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR01:15

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.

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Related Experiment Video

Updated: May 22, 2026

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
10:52

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex

Published on: July 27, 2022

NMR line shapes and multi-state binding equilibria.

Evgenii L Kovrigin1

  • 1Department of Chemistry, Marquette University, PO Box 1881, Milwaukee, WI 53201, USA. evgueni.kovriguine@mu.edu

Journal of Biomolecular NMR
|May 22, 2012
PubMed
Summary

Nuclear magnetic resonance (NMR) line-shape analysis reveals protein-ligand interactions. Computational analysis of three-state models helps interpret complex NMR spectra for understanding protein binding mechanisms.

Area of Science:

  • Biophysics
  • Structural Biology
  • Computational Chemistry

Background:

  • Protein function depends on conformational changes and ligand binding, explained by pre-existing equilibria and induced fit models.
  • Nuclear magnetic resonance (NMR) spectroscopy is sensitive to protein-ligand interactions, with line-shape analysis yielding thermodynamic and kinetic binding data.
  • Interpreting complex NMR line shapes in multi-state systems remains a challenge for broad application of this technique.

Purpose of the Study:

  • To computationally explore protein-ligand binding mechanisms involving conformational changes.
  • To identify signature spectral features for recognizing specific interaction mechanisms in multi-state systems.
  • To provide guidance for interpreting complex NMR line-shape data in biophysical studies.

Main Methods:

More Related Videos

Measuring Interactions of Globular and Filamentous Proteins by Nuclear Magnetic Resonance Spectroscopy (NMR) and Microscale Thermophoresis (MST)
10:28

Measuring Interactions of Globular and Filamentous Proteins by Nuclear Magnetic Resonance Spectroscopy (NMR) and Microscale Thermophoresis (MST)

Published on: November 2, 2018

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

Related Experiment Videos

Last Updated: May 22, 2026

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
10:52

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex

Published on: July 27, 2022

Measuring Interactions of Globular and Filamentous Proteins by Nuclear Magnetic Resonance Spectroscopy (NMR) and Microscale Thermophoresis (MST)
10:28

Measuring Interactions of Globular and Filamentous Proteins by Nuclear Magnetic Resonance Spectroscopy (NMR) and Microscale Thermophoresis (MST)

Published on: November 2, 2018

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

  • Computational exploration of systems where protein isomerization or dimerization is coupled to ligand binding.
  • Extensive analysis of multiple exchange regimes within a family of three-state models.
  • Identification of characteristic spectral patterns indicative of different binding mechanisms.

Main Results:

  • Distinct multi-state models can generate highly similar NMR spectral patterns, complicating interpretation.
  • Signature features were identified to aid experimentalists in recognizing specific protein-ligand interaction mechanisms.
  • Receptor aggregation can mimic three-state line shapes, potentially leading to misinterpretation.

Conclusions:

  • Computational analysis of three-state NMR models provides critical insights into complex protein-ligand interactions.
  • Distinguishing between different binding mechanisms requires careful analysis and complementary experimental approaches.
  • Suggestions for complementary experiments are provided to ensure reliable mechanistic insights and avoid misinterpretation due to aggregation.