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相关概念视频

¹H NMR: Complex Splitting01:13

¹H NMR: Complex Splitting

A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
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...
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: Distortionless Enhancement by Polarization Transfer (DEPT)01:20

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
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.
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...

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相关实验视频

Updated: Jul 12, 2026

Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins
12:47

Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins

Published on: December 27, 2016

在U-(13) C,(15) N标记中确定多重扭转角约束:3D (1) H-(15) N-(13) C-(1) H双极化学转移NMR光谱在旋转的固体中.

Chad M Rienstra1, Morten Hohwy, Leonard J Mueller

  • 1Department of Chemistry, Center for Magnetic Resonance, Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Journal of the American Chemical Society
|October 3, 2002
PubMed
概括

这项研究引入了一种新的3D核磁共振 (NMR) 技术,以精确确定和蛋白质构造. 该方法使用双极化学转移来限制分子扭转角度,推进结构生物学研究.

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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

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

Published on: November 1, 2024

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Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins
12:47

Nuclear Magnetic Resonance Spectroscopy for the Identification of Multiple Phosphorylations of Intrinsically Disordered Proteins

Published on: December 27, 2016

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

NMR 15N Relaxation Experiments for the Investigation of Picosecond to Nanoseconds Structural Dynamics of Proteins
09:25

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

Published on: November 1, 2024

科学领域:

  • 结构生物学 结构生物学
  • 生物物理化学 生物物理化学
  • 核磁共振 (NMR) 光谱学 核磁共振 (NMR) 光谱学

背景情况:

  • 确定和蛋白质构成对于理解它们的功能至关重要.
  • 传统的核磁共振方法在精确地限制脊柱和侧链结构方面存在局限性.
  • 扭转角 (phi,psi,chi1) 是定义分子构造的关键参数.

研究的目的:

  • 开发和演示一种新的3D核磁共振实验,用于对的高精度构造分析.
  • 为了同时限制多个骨干和侧链扭转角度.
  • 在固体三系统上验证方法.

主要方法:

  • 使用了3D (1) H- ((15) N- ((13) C- ((1) H双极化学转移神奇角度旋转的NMR实验.
  • 采用特定交叉极化用于极化转移和平均哈密尔顿理论用于光谱分析.
  • 结合了来自多个NMR实验的数据,以最大限度地减少构造模两可.

主要成果:

  • 在固体三 (N-formyl-Met-Leu-Phe-OH) 中成功约束了八个扭转角度 (phi,chi1,psi).
  • 证明了光谱线形状对分子扭转角度的强烈依赖.
  • 实现了高灵敏度和动态范围,使精确的形状确定成为可能.

结论:

  • 开发的3D核磁共振方法为骨和侧链构造提供了准确的约束.
  • 这种技术为更大的和蛋白质的结构阐明提供了一个强大的工具.
  • 这种方法提高了固态NMR结构研究的精度.