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相关概念视频

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

1.2K
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...
1.2K
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR01:15

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

1.6K
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.
1.6K
Conformations of Cyclohexane02:11

Conformations of Cyclohexane

15.1K
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
15.1K
UV–Vis Spectroscopy of Conjugated Systems01:32

UV–Vis Spectroscopy of Conjugated Systems

8.2K
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in...
8.2K
Properties of Enantiomers and Optical Activity02:24

Properties of Enantiomers and Optical Activity

21.0K
It is essential to understand the difference between chiral and achiral interactions and the implications thereof in optical activity and their applications. Just as our feet, which are chiral, interact uniquely with chiral objects, such as a pair of shoes, but identically with achiral socks, enantiomers of a molecule exhibit different properties only when they interact with other chiral media. An example of a significant implication from this facet is the phenomenon known as optical activity,...
21.0K
UV–Vis Spectroscopy: Molecular Electronic Transitions01:16

UV–Vis Spectroscopy: Molecular Electronic Transitions

2.7K
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
2.7K

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Flexural Rigidity Measurements of Biopolymers Using Gliding Assays
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通过振动光学活动监测的三种聚聚胺酸构造.

Andrii S Kurochka1, Jana Hudecová2, Josef Kapitán2

  • 1Institute of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo Náměstí 2, 16610 Prague, Czech Republic.

Analytical chemistry
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概括

使用振动光学活动研究了聚聚胺酸 (PGA) 折叠. 这种技术与计算方法相结合,提供了一种强大的方法来分析蛋白质结构,包括粉样纤维.

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科学领域:

  • 生物物理学的生物物理.
  • 频谱学是一种光谱学.
  • 计算化学计算化学

背景情况:

  • 聚聚胺酸 (PGA) 作为和蛋白质折叠研究的模型.
  • 振动光学活性 (VOA) 是分析溶液中的分子构成的一个关键技术.

研究的目的:

  • 为了研究不同质子状态的PGA行为.
  • 推进用于蛋白质结构分析的光谱学方法.
  • 为了探索PGA纤维的VOA.

主要方法:

  • 获取红外 (IR),振动圆形二极化 (VCD),拉曼和拉曼光学活动 (ROA) 频谱.
  • 分子动力学 (MD) 和密度函数理论 (DFT) 计算用于光谱解释.
  • 对PGA反体和纤维素的ROA光谱的测量.

主要成果:

  • 对于PGA纤维素,观察到明显的ROA模式,可与两个反体验证.
  • 计算模型成功地将光谱特征与分子几何学联系起来.
  • 模拟的光谱在很大程度上重现了实验数据,尽管纤维 VOA 模拟存在挑战.

结论:

  • VOA与光谱模拟相结合,是研究蛋白质几何学的有效工具,包括像粉样纤维这样的聚合物.
  • 在VOA对粉样纤维的进展可以提高对它们在神经退行性疾病中的生物学作用的理解.