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Related Concept Videos

Mass Spectrometry: Isotope Effect01:13

Mass Spectrometry: Isotope Effect

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Most elements exist in nature as a mixture of isotopes. The isotopes differ in weight due to their respective number of neutrons. The molecular weight of a molecule is different depending on the specific isotope of its elements involved. As a result, the mass spectrum of the molecule exhibits peaks from the same fragment at multiple positions. The positions of these mass signals depend on the difference between the molecular mass. Furthermore, the intensity of these signals is dependent on the...
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Isotopes and Radioisotopes01:28

Isotopes and Radioisotopes

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In the early 1900s, English chemist Frederick Soddy realized that an element could have atoms with different masses that were chemically indistinguishable. These different types are called isotopes — atoms of the same element that differ in mass. Isotopes differ in mass because they have different numbers of neutrons but are chemically identical because they have the same number of protons. Soddy was awarded the Nobel Prize in Chemistry in 1921 for this discovery.
An isotope containing...
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¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons01:03

¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons

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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...
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Isotopes01:12

Isotopes

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Elements have a set number of protons that determines their atomic number (Z). For example, all atoms with eight protons are oxygen; however, the number of neutrons can vary for atoms of the same element. The sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are called isotopes. Elements can have multiple isotopes, for example, carbon-12, carbon-13, and carbon-14.
An element's atomic mass, or weight,...
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Isomerism02:43

Isomerism

18.4K
Isomers are molecules with the same molecular formula but different structural arrangements. Isomers can be further classified into constitutional isomers and stereoisomers. Constitutional isomers differ in the connectivity of their constituent atoms. For example, 2-butanol and diethyl ether are constitutional isomers, as they have the same chemical formula, C4H10O, but differ in the connectivity of the carbon and oxygen atoms. Constitutional isomers have different physical and chemical...
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High-Resolution Mass Spectrometry (HRMS)01:15

High-Resolution Mass Spectrometry (HRMS)

1.3K
The resolution of a mass spectrometer depends on the efficiency of separating ions with different ion masses. The mass of an atom is approximated to the sum of the masses of protons and neutrons inside, considering the masses of protons and neutrons as equal. However, the masses of the proton (1.6726 × 10−24 g) and neutron (1.6749 × 10−24 g) are not truly equal. There is a minor error in the expression of atomic masses relative to the simplest atom of hydrogen. For...
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Updated: Jun 26, 2025

Cellular Lipid Extraction for Targeted Stable Isotope Dilution Liquid Chromatography-Mass Spectrometry Analysis
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InChI isotopologue and isotopomer specifications.

Hunter N B Moseley1, Philippe Rocca-Serra2, Reza M Salek3

  • 1Department of Molecular & Cellular Biochemistry, University of Kentucky, Lexington, KY, USA. hunter.moseley@uky.edu.

Journal of Cheminformatics
|May 14, 2024
PubMed
Summary
This summary is machine-generated.

This study proposes an extension to the International Chemical Identifier (InChI) standard for representing isotopically-resolved chemical entities. This innovation enhances data annotation for analytical chemistry, promoting FAIR data principles and Open Science.

Keywords:
Chemical annotationInChIInternational chemical identifierIsotope-resolvedIsotopologueIsotopomer

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Area of Science:

  • Chemical informatics
  • Analytical chemistry
  • Data science

Background:

  • The International Union of Pure and Applied Chemistry (IUPAC) International Chemical Identifier (InChI) is a standard for chemical structure representation.
  • Current InChI limitations exist in fully representing isotopically-resolved chemical entities, especially with ambiguous isotope localization.
  • Accurate chemical identification is crucial for analytical instrumentation like NMR and mass spectrometry.

Purpose of the Study:

  • To propose an extension to the InChI standard for improved representation of isotopically-resolved chemical entities.
  • To enhance the interpretation of the existing isotopic layer and introduce a new isotopologue layer.
  • To support unique identification of chemical features detected in analytical measurements.

Main Methods:

  • Development of an extended InChI standard specification.
  • Incorporation of an improved isotopic layer interpretation.
  • Introduction of a novel isotopologue layer for ambiguous isotope localization.

Main Results:

  • A proposed extension to the InChI standard capable of representing isotopically-resolved chemical entities with varying ambiguity.
  • Enhanced capability for unique identification of chemical features from analytical data.
  • Improved support for annotating analytical datasets.

Conclusions:

  • The proposed InChI extension facilitates better characterization of chemical entities in analytical data.
  • This advancement supports the FAIR data principles (Findable, Accessible, Interoperable, Reusable) for chemical datasets.
  • The extension promotes Open Science practices within the chemistry community.