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Related Concept Videos

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...
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.
Newman Projections02:06

Newman Projections

Different notations are used to represent the three-dimensional structure of molecules on two-dimensional surfaces. One of the most commonly used representations is the dash-wedge formula. The dashed wedges, solid wedges, and the plane lines indicate the groups situated behind the plane, coming out of the plane, and in the plane, respectively.
The organic molecules rotate across the single bonds leading to numerous temporary three-dimensional structures of varying energy known as conformers.
Chemical Shift: Internal References and Solvent Effects01:17

Chemical Shift: Internal References and Solvent Effects

In an NMR sample, precise measurement of the absolute absorption frequencies of nuclei is difficult. A standard internal reference compound is added, and the frequency difference between the reference signal and sample signals is measured.
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
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.
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...

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Updated: Jul 11, 2026

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

Helix conformations in 7TM membrane proteins determined using oriented-sample solid-state NMR with multiple

Thomas Vosegaard1, Miya Kamihira-Ishijima, Anthony Watts

  • 1Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus, Aarhus, Denmark. tv@chem.au.dk

Biophysical Journal
|September 11, 2007
PubMed
Summary

This study introduces a novel solid-state NMR method to determine membrane protein helix structures in native environments. The technique accurately maps the orientation of transmembrane helices, aiding in understanding protein function.

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Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins
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Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins

Published on: December 27, 2016

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Last Updated: Jul 11, 2026

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

Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins
12:47

Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins

Published on: December 27, 2016

Area of Science:

  • Biophysics
  • Structural Biology
  • Membrane Protein Chemistry

Background:

  • Determining the structure and conformation of large membrane proteins in their native lipid bilayers is crucial for understanding their biological functions.
  • Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy offers a powerful approach for studying proteins in membrane environments.

Purpose of the Study:

  • To develop and demonstrate a robust method for determining the conformational arrangement of transmembrane helices in large membrane proteins within native membranes.
  • To establish constraints on the orientation of helices relative to the membrane bilayer normal.

Main Methods:

  • Utilizing oriented solid-state NMR spectroscopy with site-specific (15)N labeling (methionine, valine, glycine).
  • Performing extensive numerical analysis of 2D (1)H-(15)N heteronuclear correlation spectra, focusing on dipole-dipole couplings and chemical shifts.
  • Applying the method to bacteriorhodopsin reconstituted in native purple membranes.

Main Results:

  • Successfully established combined constraints on the orientation of bacteriorhodopsin's seven transmembrane helices.
  • Demonstrated the method's applicability to proteins in native membrane environments.
  • Validated the robustness of the technique against non-ideal sample alignment.

Conclusions:

  • The proposed solid-state NMR approach is a versatile tool for analyzing large membrane protein structures in native membranes.
  • The method's independence from specific resonance assignments and tolerance to sample imperfections make it broadly applicable.
  • This technique facilitates the study of conformational dynamics and function-induced changes in integral membrane proteins.