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相关概念视频

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 of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
¹H NMR: Long-Range Coupling01:27

¹H NMR: Long-Range Coupling

The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
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.

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相关实验视频

Updated: Jul 7, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
14:44

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

Published on: December 16, 2013

质子选择性17O-1H距离测量在快速魔力旋转角固态NMR光谱中用于确定键长度.

Andreas Brinkmann1, Arno P M Kentgens

  • 1Physical Chemistry/Solid State NMR, Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands. a.brinkmann@science.ru.nl

Journal of the American Chemical Society
|November 16, 2006
PubMed
概括
此摘要是机器生成的。

我们开发了一种新的固态核磁共振方法,用于测量材料中的特定氧-17到质子-1H距离. 这种技术精确地确定了键之间的距离,即使是附近的质子.

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NMR 15N Relaxation Experiments for the Investigation of Picosecond to Nanoseconds Structural Dynamics of Proteins

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

Published on: December 16, 2013

High-Speed Magnetic Tweezers for Nanomechanical Measurements on Force-Sensitive Elements
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NMR 15N Relaxation Experiments for the Investigation of Picosecond to Nanoseconds Structural Dynamics of Proteins
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科学领域:

  • 固态核磁共振 (NMR) 光谱学 固态核磁共振 (NMR) 光谱学
  • 材料科学 材料科学 材料科学
  • 生物物理学的生物物理.

背景情况:

  • 确定核间距离对于理解分子结构和相互作用至关重要.
  • 固态NMR是研究材料的强大工具,但选择性距离测量可能具有挑战性.
  • 在复杂的系统中区分短距离和中距离需要先进的技术.

研究的目的:

  • 提出一种用于测量17O-1H核间距离的新型质子选择方法.
  • 为了能够选择性地确定键之间的中程17O...1H距离.
  • 为了克服在干扰质子信号的情况下解决特定距离的局限性.

主要方法:

  • 使用了快速魔法角度旋转 (MAS) 固态NMR光谱.
  • 使用一种新开发的基于对称性的射频脉冲序列 (SR%@mt;sys@%4%@sx@%1%@be@%2%@sxx@%%@mx@%) 进行质子复合.
  • 应用高静态磁场 (18.8 T) 和快速MAS (50 kHz) 来提高质子光谱分辨率.
  • 同时脱的同核质子双极相互作用.

主要成果:

  • 成功演示了用于确定17O-1H距离的质子选择方法.
  • 实现了特定 (17O,1H) 旋转对之间的核间距离的选择性测量.
  • 启用了通过键的中程17O...1H距离的估计.
  • 在同一个17O地点与短距离17O-1H接触区分了中程距离.

结论:

  • 提出的方法为固体材料中特定地点的17O-1H距离测定提供了可靠的方法.
  • 该技术适用于有机,生物和仿生系统.
  • 该方法增强了固态NMR光谱学的结构阐明能力.