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相关概念视频

Double Resonance Techniques: Overview01:12

Double Resonance Techniques: Overview

831
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
831
Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

1.3K
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis.
1.3K
Atomic Nuclei: Types of Nuclear Relaxation01:28

Atomic Nuclei: Types of Nuclear Relaxation

1.1K
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
1.1K
Nuclear Overhauser Enhancement (NOE)01:06

Nuclear Overhauser Enhancement (NOE)

1.5K
Irradiation of a spin-active nucleus causes an increase or decrease in the signal intensity of neighboring nuclei that are not necessarily chemically bonded or involved in J-coupling. This phenomenon, called the nuclear Overhauser enhancement (NOE), results from through-space interactions between the nuclear spins. The NOE effect decreases with increasing internuclear distance and is generally not observed beyond 4 angstroms. In NOE, dipole-dipole interactions between neighboring spin-active...
1.5K
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)01:15

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)

1.1K
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...
1.1K
2D NMR: Overview of Homonuclear Correlation Techniques01:16

2D NMR: Overview of Homonuclear Correlation Techniques

754
Homonuclear correlation spectroscopy (COSY) is a powerful technique used in Nuclear Magnetic Resonance (NMR) spectroscopy to study the correlations between nuclei of the same type within a molecule. It provides information about scalar couplings between adjacent nuclei, which helps determine connectivity and structural information. There are several COSY variants, each with its unique strengths and experimental parameters.
COSY90 is the standard two-dimensional (2D) COSY experiment that...
754

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Updated: Mar 10, 2026

Dissolution Dynamic Nuclear Polarization Instrumentation for Real-time Enzymatic Reaction Rate Measurements by NMR
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在固态动态核极化下异质核交叉放松

Diane Daube1,2, Victoria Aladin1,2, Jörg Heiliger1,2

  • 1Institute of Physical and Theoretical Chemistry and Institute of Biophysical Chemistry, Goethe University Frankfurt , Max-von-Laue-Str. 7-9, 60438 Frankfurt am Main, Germany.

Journal of the American Chemical Society
|December 10, 2016
PubMed
概括

我们发现了从质子 (H) 到碳 (C) 的自发偏振转移使用动态核偏振 (DNP) 在100 K. 这种方法增强了C NMR信号,在分子研究中提供了新的应用.

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科学领域:

  • 固态核磁共振 (NMR) 光谱
  • 动态核极化 (DNP)

背景情况:

  • 动态核极化 (DNP) 通过将极化从电子自旋转到核自旋转来增强NMR信号.
  • 超极化技术对于提高NMR灵敏度至关重要,特别是对于像C这样的低马核.

研究的目的:

  • 在100K左右的魔法角旋转过程中,研究自发的极化转移从超极化H到C.
  • 阐明这种极化转移的机制及其潜在应用.

主要方法:

  • 磁角旋转 (MAS) 动态核极化 (DNP) 在大约100K.
  • 使用微波辐射和二氧化极化剂进行超极化.
  • 甲基组内H-C交叉放松和C-C旋转扩散用于极化扩散.

主要成果:

  • 观察到自发的极化转移从H到C,导致反向的CNM信号具有增强的幅度.
  • 达到高达-15的有效C增强因子.
  • 证明Gd(III) 放大了效果,可能是通过加速H放松.
  • 证实了DNP诱导的蛋白质和氨基酸交叉放松的强度.

结论:

  • 由甲基重定向动态驱动的H-C交叉放松,在DNP条件下调解自发的极化转移.
  • 这种DNP增强的交叉放松模仿了核Overhauser效应 (NOE),但利用超极化来增强稳定状态.
  • 这些发现表明在对生物分子和材料的敏感NMR研究中有潜在的应用.