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Related Concept Videos

Atomic Nuclei: Nuclear Spin01:08

Atomic Nuclei: Nuclear Spin

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All atomic particles possess an intrinsic angular momentum, or 'spin'. Electrons, protons, and neutrons each have a spin value of ½, although protons and neutrons in nuclei may have higher half-integer spins owing to energetic factors.
Atomic nuclei have a net nuclear spin, , which can have an integer or half-integer value. In atomic nuclei, the spins of protons are paired against each other but not with neutrons, and vice versa. Consequently, an even number of protons does not...
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Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)01:15

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Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) is an advanced Nuclear Magnetic Resonance (NMR) technique specifically designed to detect and enhance the signals of low-abundance nuclei, such as carbon-13 and nitrogen-15, in small molecules. The fundamental principle behind INEPT is the transfer of polarization from a more abundant and highly polarizable nucleus, typically hydrogen-1, to the low-abundance nucleus of interest. This process effectively boosts the NMR signal of the...
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Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic Nuclei: Nuclear Spin State Overview

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NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of...
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Interpreting ¹H NMR Signal Splitting: The (n + 1) Rule01:10

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

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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...
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Atomic Nuclei: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

1.2K
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
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Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

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The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
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Updated: Sep 19, 2025

Millisecond Hydrogen/Deuterium-Exchange Mass Spectrometry for the Study of Alpha-Synuclein Structural Dynamics Under Physiological Conditions
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A Fast Neural Network for Isotopic Charge State Assignment.

John G Pavek1, Nicholas E Bollis2, Josiah Grimes1

  • 1Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States.

Journal of the American Chemical Society
|June 10, 2025
PubMed
Summary
This summary is machine-generated.

A new neural network algorithm, IsoDec, rapidly and accurately assigns charge states in mass spectrometry, improving proteomic analysis. This advancement enhances feature identification and proteoform-spectrum matching in complex datasets.

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Area of Science:

  • Analytical Chemistry
  • Biochemistry
  • Computational Biology

Background:

  • Electrospray ionization (ESI) mass spectrometry is crucial for chemical analysis.
  • Accurate charge state assignment of analytes is vital for identification in ESI-MS.
  • Current charge state assignment methods lack optimal speed and accuracy.

Purpose of the Study:

  • To develop a fast and accurate algorithm for charge state assignment in ESI mass spectrometry.
  • To evaluate the performance of the developed algorithm, IsoDec, on top-down proteomics data.
  • To demonstrate the utility of IsoDec in large-scale proteomic data analysis.

Main Methods:

  • Development of a fast neural network for isotopic envelope charge assignment.
  • Testing IsoDec on top-down proteomics spectra from diverse instruments.
  • Comparison of IsoDec performance against existing software tools.
  • Application of IsoDec to large top-down proteomics datasets for database searching.

Main Results:

  • IsoDec demonstrates improved speed and accuracy in charge state assignment compared to existing tools.
  • The neural network approach directly contributes to IsoDec's performance enhancement.
  • Database searching with IsoDec output yields superior proteoform-spectrum matches in terms of coverage and accuracy.
  • IsoDec correctly assigns more features on complex individual spectra.

Conclusions:

  • IsoDec offers a significant advancement in mass spectrometry data analysis.
  • Lightweight neural networks show great potential for improving ESI-MS techniques.
  • IsoDec enhances the identification and characterization of proteoforms in complex biological samples.