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Related Concept Videos

NMR Spectroscopy: Chemical Shift Overview01:15

NMR Spectroscopy: Chemical Shift Overview

The position of the absorption signal of a sample is reported relative to the position of the signal of tetramethylsilane (TMS), which is added as an internal reference while recording spectra. The difference between the absorption frequencies of the sample and TMS (in Hz) is divided by the spectrometer operating frequency (in MHz) to obtain a dimensionless quantity called the chemical shift. It is reported on the δ (delta) scale and expressed in parts per million.
For instance, the proton...
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 Chemical Shift Equivalence: Homotopic and Heterotopic Protons01:03

¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons

Protons in identical electronic environments within a molecule are chemically equivalent and have the same chemical shift. The replacement test is a useful tool to identify chemical equivalence and predict NMR spectra. A substituent replaces each of the protons being examined and the resulting molecules are compared. If the same molecule is obtained, the protons are equivalent or homotopic. Replacement of any hydrogens in ethane by chlorine yields chloroethane because all six protons are...
Propagation of Uncertainty from Systematic Error01:10

Propagation of Uncertainty from Systematic Error

The atomic mass of an element varies due to the relative ratio of its isotopes. A sample's relative proportion of oxygen isotopes influences its average atomic mass. For instance, if we were to measure the atomic mass of oxygen from a sample, the mass would be a weighted average of the isotopic masses of oxygen in that sample. Since a single sample is not likely to perfectly reflect the true atomic mass of oxygen for all the molecules of oxygen on Earth, the mass we obtain from this particular...
¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons00:58

¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons

Replacing each alpha-hydrogen in chloroethane by bromine (or a different functional group) yields a pair of enantiomers. Such protons are called prochiral or enantiotopic and are related by a mirror plane. Enantiotopic protons are chemically equivalent in an achiral environment. Because most proton NMR spectra are recorded using achiral solvents, enantiotopic hydrogens yield a single signal.
In chiral compounds such as 2-butanol, replacing the methylene hydrogens at C3 produces a pair of...
Proton (¹H) NMR: Chemical Shift01:07

Proton (¹H) NMR: Chemical Shift

Organic molecules primarily contain carbon and hydrogen atoms. While all the hydrogen isotopes are NMR-active, protium or hydrogen-1 is the most abundant. It has a significant energy separation between its nuclear spin states due to its large gyromagnetic ratio. As per Boltzmann's distribution, an increase in the energy separation implies a greater excess population of nuclei available for excitation, resulting in a strong NMR absorption signal.
Absorption signals of all the protium nuclei in a...

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Related Experiment Video

Updated: Jun 6, 2026

Pure Shift Nuclear Magnetic Resonance: a New Tool for Plant Metabolomics
13:16

Pure Shift Nuclear Magnetic Resonance: a New Tool for Plant Metabolomics

Published on: July 31, 2021

Genetic algorithm for shift-uncertainty correction in 1-D NMR-based metabolite identifications and quantifications.

F-M Schleif1, T Riemer, U Börner

  • 1Department of Computer Science, University of Bielefeld, Bielefeld, Germany. schleif@informatik.uni-leipzig.de

Bioinformatics (Oxford, England)
|December 3, 2010
PubMed
Summary
This summary is machine-generated.

Extended Targeted Profiling (ETP) automates the analysis of (1)H NMR spectra by estimating shift uncertainties. This method significantly improves metabolite identification and quantification, reducing manual effort for high-throughput biological and clinical analysis.

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Last Updated: Jun 6, 2026

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Identification and Quantification of Deranged Metabolites in Critically Ill Patients Using NMR-Based Metabolomics
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Identification and Quantification of Deranged Metabolites in Critically Ill Patients Using NMR-Based Metabolomics

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Area of Science:

  • Metabolomics
  • Biotechnology
  • Analytical Chemistry

Background:

  • Metabolic process analysis is crucial for understanding biological systems and diseases.
  • Nuclear Magnetic Resonance (NMR) spectroscopy quantifies metabolite concentrations but faces challenges with complex biological spectra.
  • Current methods like Targeted Profiling (TP) struggle with spectral shift uncertainties, necessitating time-consuming manual adjustments.

Purpose of the Study:

  • To develop an automated approach for processing complex (1)H NMR spectra.
  • To address the challenge of shift uncertainties in NMR spectral fitting.
  • To improve the accuracy and efficiency of metabolite identification and quantification.

Main Methods:

  • Developed Extended Targeted Profiling (ETP), an automated method combining a genetic algorithm (GA) and least squares optimization (LSQO).
  • ETP estimates and corrects shift uncertainties in (1)H NMR data.
  • The approach preserves the functional structure of NMR spectra, avoiding simplistic binning strategies.

Main Results:

  • ETP significantly enhances the accuracy of metabolite identification and quantification compared to standard TP.
  • The automated ETP approach yields results comparable to manual expert analysis.
  • Simultaneous shift uncertainty correction and least squares fitting improve (1)H NMR data analysis.

Conclusions:

  • ETP offers a reliable and automated solution for analyzing complex NMR spectra.
  • The method reduces the need for manual intervention, enabling high-throughput analysis.
  • ETP advances the application of NMR spectroscopy in clinical and biological research.