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相关概念视频

Nuclear Overhauser Enhancement (NOE)01:07

Nuclear Overhauser Enhancement (NOE)

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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...
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Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)01:15

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)

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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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Double Resonance Techniques: Overview01:12

Double Resonance Techniques: Overview

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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...
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Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

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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.
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¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)01:20

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

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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...
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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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Hyperpolarized 13C Metabolic Magnetic Resonance Spectroscopy and Imaging
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直接结合的双子子增加X核的超极化使用动态核极化.

Catriona H E Rooney1, Ayelet Gamliel2,3, David Shaul2,3

  • 1Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.

Chemphyschem : a European journal of chemical physics and physical chemistry
|July 11, 2023
PubMed
概括

化增强了X核直接与子结合的固态动态核极化 (DNP). 与质子结合相比,这种Deuteron效应显著增加了极化,提供了新的DNP应用.

关键词:
2 - 脱氧 - D - 葡萄糖2 - 脱氧 - D - 葡萄糖D-葡萄糖是D-葡萄糖中的一种.酸盐和酸盐的使用方法固态极化是固态极化的一种.尿素 urea 的使用方法

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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
  • 动态核极化 (DNP) 增强增强
  • 在磁共振中同位素效应.

背景情况:

  • 动态核极化 (DNP) 显著提高了NMR信号的灵敏度.
  • 同位素替代 (化) 对DNP极化水平的影响需要进一步研究.
  • 了解特定站点的DNP增强对于优化NMR实验至关重要.

研究的目的:

  • 调查化对X核 (C-13和N-15) 固态DNP极化水平的影响.
  • 为了确定与质子相比,与子的直接结合是否增强了DNP极化.
  • 探索周围核环境在DNP增强中的作用.

主要方法:

  • 固态动态核极化 (DNP) 实验是在3.35特斯拉进行的.
  • 分析了D-葡萄糖,2-脱氧-D-葡萄糖,[N-15]尿素和[N-15]酸盐的化和质子化样本.
  • 对C-13和N-15核的极化水平进行了比较,比较了化和质子化位点之间的极化水平.

主要成果:

  • 糖类中的化C-13位点显示DNP水平比质子化位点高6.3至17.5倍.
  • 与可交换质子结合的化N-15位点显示极化增加了1.3倍.
  • 对于与质子或子不结合的N-15位点,没有观察到显著的DNP增强.

结论:

  • 与质子相比,X核与子的直接结合显著增强了固态DNP极化.
  • 这种由deuteron介导的DNP增强效应独立于溶剂质子化.
  • 这些发现表明,DNP增强的新机制适用于各种分子系统.