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Related Concept Videos

Carbon-13 (¹³C) NMR: Overview01:10

Carbon-13 (¹³C) NMR: Overview

Carbon-13 is a naturally occurring NMR-active isotope of carbon with a low natural abundance of 1.1%. In contrast, carbon-12 is the most abundant isotope of carbon with zero nuclear spin. Therefore, it is NMR inactive. The gyromagnetic ratio of carbon-13 is smaller than that of protons. As a result, carbon-13 resonance is about 6000 times weaker than proton resonance. For a given magnetic field strength, the resonance frequency of carbon-13 is about one-fourth of the resonance frequency for...
¹³C NMR: ¹H–¹³C Decoupling01:04

¹³C NMR: ¹H–¹³C Decoupling

The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
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...
NMR Spectroscopy Of Amines01:19

NMR Spectroscopy Of Amines

In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is broad and...
Applications Of NMR In Biology01:25

Applications Of NMR In Biology

Nuclear magnetic resonance (NMR) spectroscopy is a very valuable analytical technique for researchers. It has been used for more than 50 years as an analytical tool. F. Bloch and E. Purcell formulated NMR in 1946 and won the 1952 Nobel Prize in Physics  for their work. Biological macromolecules such as proteins, nucleic acids, lipids, and organic molecules including pharmaceutical compounds, can be studied using this versatile tool that exploits the magnetic properties of certain nuclei.
The...
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...

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Related Experiment Video

Updated: Jul 7, 2026

Paramagnetic Relaxation Enhancement for Detecting and Characterizing Self-Associations of Intrinsically Disordered Proteins
07:24

Paramagnetic Relaxation Enhancement for Detecting and Characterizing Self-Associations of Intrinsically Disordered Proteins

Published on: September 23, 2021

Performance validation of neural network based (13)c NMR prediction using a publicly available data source.

K A Blinov1, Y D Smurnyy, M E Elyashberg

  • 1Advanced Chemistry Development, Moscow Department, 6 Akademik Bakulev Street, Moscow 117513, Russian Federation.

Journal of Chemical Information and Modeling
|February 26, 2008
PubMed
Summary

This study validates a neural network algorithm for predicting 13C NMR chemical shifts using the NMRShiftDB database. The algorithm achieved a mean error of 1.59 ppm, demonstrating its predictive accuracy.

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Paramagnetic Relaxation Enhancement for Detecting and Characterizing Self-Associations of Intrinsically Disordered Proteins
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15N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the µs-ms Timescale
08:09

15N CPMG Relaxation Dispersion for the Investigation of Protein Conformational Dynamics on the µs-ms Timescale

Published on: April 19, 2021

Area of Science:

  • Computational Chemistry
  • Spectroscopy
  • Machine Learning

Background:

  • 13C NMR spectroscopy is crucial for chemical structure elucidation.
  • Accurate prediction of 13C NMR chemical shifts aids in spectral assignment and structure determination.
  • Neural network algorithms offer a promising approach for chemical shift prediction.

Purpose of the Study:

  • To validate the performance of a neural network-based 13C NMR prediction algorithm.
  • To assess prediction accuracy using a large, open-source chemical shift database (NMRShiftDB).
  • To compare algorithm performance with and without overlap between training and test data.

Main Methods:

  • Validation of a neural network algorithm using NMRShiftDB (ca. 214,000 chemical shifts).
  • Analysis of performance on two subsets: 'included shift set' (ca. 121,000 shifts) and 'excluded shift set' (ca. 93,000 shifts).
  • Comparison of results with Robien's CNMR Neural Network Predictor.

Main Results:

  • The algorithm achieved a mean error of 1.59 ppm across the entire NMRShiftDB.
  • Mean deviations were 1.47 ppm for the 'included shift set' and 1.74 ppm for the 'excluded shift set'.
  • Performance was comparable to other reported algorithms.

Conclusions:

  • The neural network algorithm demonstrates reliable performance for 13C NMR chemical shift prediction.
  • The validation using NMRShiftDB provides a robust assessment of the algorithm's accuracy.
  • This tool can aid researchers in spectral analysis and structure elucidation.