螺旋在未溶解中展开
B S Kinnear1, M R Hartings, M F Jarrold
1Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Journal of the American Chemical Society
|June 14, 2001
概括
该研究使用离子流动性检查了形状. 一个仍然是一个球体,而另一个呈现出一个阿尔法螺旋,展开成一个长寿的中间结构.
科学领域:
- 化学物理 化学物理
- 生物物理化学 生物物理化学
- 分子动力学分子动力学
背景情况:
- 了解质结构对于生物功能至关重要.
- 形状可以受到序列和环境的影响.
- 离子流动性是研究气相结构的强大技术.
研究的目的:
- 为了研究两个特定的温度依赖性构造:Ac-K (((AGG) ((5) + H (((+)) 和Ac- ((AGG) ((5) K + H ((+)).
- 描述螺旋结构的展开路径和动力学.
- 在展开过程中识别潜在的中间构造.
主要方法:
- 离子流动性测量是在广泛的温度范围 (150-410 K) 上进行的.
- 用速率常数进行了螺旋展开的动力分析.
- 用分子动力学模拟来探索构造性景观.
主要成果:
- 在所有测试温度中,Ac-K ((AGG) ((5) + H ((+)) 保持了球体构造.
- 在低温下,Ac-(AGG) ((5) K+H(+) 呈现出阿尔法螺旋和球体形式.
- 阿尔法螺旋的展开发生在毫秒的时间尺度上,产生了38.2kJ/mol的激活能量.
- 在螺旋体和球体状态之间观察到一种长期存在的中间形状.
结论:
- 酸Ac-K ((AGG) ((5) + H ((+)) 是作为球体的结构稳定.
- 酸Ac- ((AGG) ((5) K+H ((+)) 经历温度诱导的展开从一个阿尔法螺旋.
- 一个独特的,稳定的中间结构可能会促进从螺旋体到球体的过渡.
- 分子动力学模拟支持这种中间体作为部分未扭曲的螺旋体的存在.
相关概念视频
Solvents
A solvent is a substance, most often a liquid, that can dissolve other substances. Here, the substance being dissolved is called a solute. When a solvent and a solute combine, they form a solution - a homogenous mixture of both the solvent and the solute. Water is a universal biological solvent. Its polar structure allows it to dissolve many other polar compounds. The ability of water to dissolve is governed by a balance between water molecules binding to each other and binding to the solute.
A...
A...
Molecular Shape and Polarity
Dipole Moment of a Molecule
Intermolecular Forces
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen bonds, and dispersion...
Intermolecular Forces in Solutions
The formation of a solution is an example of a spontaneous process, a process that occurs under specified conditions without energy from some external source.
When the strengths of the intermolecular forces of attraction between solute and solvent species in a solution are no different than those present in the separated components, the solution is formed with no accompanying energy change. Such a solution is called an ideal solution. A mixture of ideal gases (or gases such as helium and argon,...
When the strengths of the intermolecular forces of attraction between solute and solvent species in a solution are no different than those present in the separated components, the solution is formed with no accompanying energy change. Such a solution is called an ideal solution. A mixture of ideal gases (or gases such as helium and argon,...
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...
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...


