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Related Concept Videos

NMR Spectrometers: Resolution and Error Correction01:14

NMR Spectrometers: Resolution and Error Correction

When magnetic nuclei in a sample achieve resonance and undergo relaxation, the signal detected in NMR is an approximately exponential free induction decay. Fourier transform of an exponential decay yields a Lorentzian peak in the frequency domain. Lorentzian peaks in an NMR spectrum are defined by their amplitude, full width at half maximum, and position, where the peak width is governed by the spin-spin relaxation time alone. In real experiments, however, the applied magnetic field is rendered...
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...
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 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.
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...

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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
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Variable reference alignment: an improved peak alignment protocol for NMR spectral data with large intersample

Neil MacKinnon1, Wencheng Ge, Amjad P Khan

  • 1Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, USA.

Analytical Chemistry
|May 24, 2012
PubMed
Summary
This summary is machine-generated.

This study introduces a novel prealignment protocol for metabolomic and metabonomic studies to improve spectral data alignment. The method enhances the accuracy of (1)H NMR profiles, especially those with significant compositional variations.

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Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

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Last Updated: May 22, 2026

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
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Published on: September 17, 2017

A Strategy for Sensitive, Large Scale Quantitative Metabolomics
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Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

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Area of Science:

  • Metabolomics and Metabonomics
  • Nuclear Magnetic Resonance (NMR) Spectroscopy
  • Bioinformatics and Computational Biology

Background:

  • Metabolomic and metabonomic studies often face challenges with variable spectral correspondence across large sample cohorts.
  • Existing spectral alignment methods may struggle with datasets exhibiting significant intersample compositional variation (e.g., pH, ionic strength).
  • A single reference spectrum is often insufficient for accurate alignment in diverse datasets.

Purpose of the Study:

  • To develop and validate a prealignment protocol for improving spectral alignment in metabolomic/metabonomic studies.
  • To address the variable correspondence problem by generating spectral segments with a common target spectrum.
  • To enable automatic definition of spectral segments, a feature lacking in many current alignment methods.

Main Methods:

  • Developed a prealignment protocol focusing on local alignment corrections within spectral regions.
  • Assumed that spectral regions share a common 'most similar' spectrum for targeted corrections.
  • Applied the protocol to two NMR datasets (cell line extracts and human urine) using recursive segment-wise peak alignment and interval correlated shifting algorithms.

Main Results:

  • The protocol successfully generated spectral segments sharing common target spectra, improving alignment quality.
  • Demonstrated enhanced alignment for (1)H NMR datasets with substantial intersample compositional variation.
  • Successfully applied to diverse datasets, including 15 aqueous cell line extracts and 20 human urine samples.

Conclusions:

  • The proposed prealignment protocol offers a significant improvement over single-reference spectrum alignment methods.
  • It effectively handles spectral variations common in large-scale metabolomic studies.
  • The protocol can be appended to existing alignment algorithms, offering broad applicability.