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相关概念视频

Valence Bond Theory02:42

Valence Bond Theory

Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
Colors and Magnetism03:02

Colors and Magnetism

Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
Rab Proteins01:14

Rab Proteins

Rab proteins constitute the largest family of monomeric GTPases, of which 70 members are present in humans. Rab proteins and their effectors regulate consecutive stages of vesicle transport such as vesicle transport, docking, and fusion to the correct recipient membrane.
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

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...
Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

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. This...
Diamagnetic Shielding of Nuclei: Local Diamagnetic Current01:14

Diamagnetic Shielding of Nuclei: Local Diamagnetic Current

An applied magnetic field causes the electrons present in the molecule to circulate, setting up a local diamagnetic current within the molecule. The local diamagnetic current arising from circulating sigma-bonding electrons induces a magnetic field, Blocal that opposes the applied magnetic field, B0. The effective magnetic field experienced by these nuclei is given by the difference between the applied and local magnetic fields in a phenomenon called local diamagnetic shielding. Essentially,...

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相关实验视频

Updated: Jul 6, 2026

Hyperpolarized Xenon for NMR and MRI Applications
16:20

Hyperpolarized Xenon for NMR and MRI Applications

Published on: September 6, 2012

脱氧血球蛋白在高磁场上的定向:来自溶液中的RDC的结构见解.

Sarata C Sahu1, Virgil Simplaceanu, Qingguo Gong

  • 1Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.

Journal of the American Chemical Society
|May 11, 2006
PubMed
概括
此摘要是机器生成的。

研究人员测量了脱氧血红蛋白A (deoxy-Hb A) 中的旋转-旋转合,这是一种关键的携带氧的蛋白质. 他们发现这些合取决于磁场强度,使得能够精确地确定偏磁蛋白的溶液结构.

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Quantification of Cellular Densities and Antigenic Properties using Magnetic Levitation
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Quantification of Cellular Densities and Antigenic Properties using Magnetic Levitation

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Last Updated: Jul 6, 2026

Hyperpolarized Xenon for NMR and MRI Applications
16:20

Hyperpolarized Xenon for NMR and MRI Applications

Published on: September 6, 2012

Crystal Structure of the N-terminal Domain of Ryanodine Receptor from Plutella xylostella
11:31

Crystal Structure of the N-terminal Domain of Ryanodine Receptor from Plutella xylostella

Published on: November 30, 2018

Quantification of Cellular Densities and Antigenic Properties using Magnetic Levitation
05:25

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科学领域:

  • 生物物理学的生物物理.
  • 结构生物学 结构生物学
  • 蛋白质NMR光谱法 蛋白质NMR光谱法

背景情况:

  • 人类正常成年血红蛋白 (Hb A) 是一个四重蛋白质,对氧气运输至关重要.
  • 没有氧气的形式,脱氧血红蛋白A (deoxy-Hb A),具有对磁性半球 (S=2).
  • 了解deoxy-Hb A在接近生理条件下的结构,动态和功能至关重要.

研究的目的:

  • 在 (15N,2H) 标记的脱氧-Hb A溶液中测量单键旋转-旋转合.
  • 为了研究这些合器的磁场依赖性.
  • 为了证明磁场依赖的剩余二极合 (RDCs) 的实用性,用于确定大型偏磁蛋白的溶液结构.

主要方法:

  • 使用了核磁共振 (NMR) 光谱学.
  • 测量是在 (15N,2H) 标记的脱氧HbA溶液中进行的.
  • 一键旋转-旋转合 (1JNH + 1DNH) 在一系列磁场强度 (11.7到21.1 T) 中进行测量.

主要成果:

  • 在测量的合和磁场强度的正方形之间观察到线性比例.
  • 这种领域依赖性允许提取残余二极合 (RDCs,1DNH).
  • 提取的RDC可以更容易地比较脱氧HbA的溶液和晶体结构.

结论:

  • 磁场依赖的RDC提供了一种强大的方法来确定大型偏磁蛋白的溶液结构.
  • 这种技术对于需要在无氧环境中进行研究的蛋白质尤其有价值.
  • 这些发现增强了我们对deoxy-Hb A的结构功能关系的理解.