对热容量变化在疏水溶解中的新角度进行研究
Kelly R Gallagher1, Kim A Sharp
1Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Journal of the American Chemical Society
|August 9, 2003
概括
对生物结构至关重要的疏水效应涉及水对非极性化合物的独特反应. 这项研究揭示了水的键是如何围绕无极和极地群体结构化,解释了不同的热容量.
科学领域:
- 生物物理化学 生物物理化学
- 水的动力学 水的动力学
- 分子相互作用 分子相互作用
背景情况:
- 极性和非极性群体的可溶性差异通过疏水性和疏水性效应驱动生物结构的自我组装.
- 疏水效应的特点是,在无极化合物水化后,水的热容量增加,与极性化合物所见的下降形成鲜明对比.
- 水围绕溶解物形成结构,显著影响了它们的溶解性和热力学特性.
研究的目的:
- 为了研究在极地和非极地群体周围独特的水结构.
- 阐明在极性和非极性溶液的水化过程中观察到的热容量相反变化的物理基础.
- 提供新的洞察力,了解疏水效应和水在溶液周围的行为.
主要方法:
- 利用从分子模拟中得出的联合辐射/角分布函数.
- 分析键特性,特别是围绕溶解物群的"低角度键".
- 将水结构与热力学特性 (如热容量) 相关联.
主要成果:
- 模拟显示,极地群周围存在"低角度键"的缺陷,而非极地群周围存在过量.
- 与高角度键相比,低角度键的能量波动较大.
- 水结构中的这些差异为相反的热容量变化提供了物理解释.
结论:
- 独特的水化结构,特别是低角度键的不同种群,是疏水效应的关键.
- 这项工作提供了对水在分子相互作用和自我组装中的作用的更深入的了解.
- 这些发现有助于了解溶解热力学和疏水效应的基本知识.
相关概念视频
Specific Heat
The specific heat capacity of a substance refers to the energy required to increase the temperature of one gram of that substance by one degree Celcius. Specific heat capacity is often represented in calories (cal), grams (g), and degrees Celsius (oC), but can also be expressed in joules (J), kilograms (kg), and Kelvin (K), among other units.
For example, increasing the temperature of one gram of water by 1°C requires one calorie of heat energy and can be written as 1 cal/g-°C, or 4186 J/kg/K.
For example, increasing the temperature of one gram of water by 1°C requires one calorie of heat energy and can be written as 1 cal/g-°C, or 4186 J/kg/K.
Constant Volume Calorimetry
Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant (atmospheric) pressure and are convenient to measure heat flow (or enthalpy change) accompanying processes that occur in solution at constant pressure. A different type of calorimeter that operates at constant volume, colloquially known as a bomb calorimeter, is used to measure the energy produced by reactions that yield large amounts of heat and...
Heating and Cooling Curves
When a substance—isolated from its environment—is subjected to heat changes, corresponding changes in temperature and phase of the substance is observed; this is graphically represented by heating and cooling curves.
For instance, the addition of heat raises the temperature of a solid; the amount of heat absorbed depends on the heat capacity of the solid (q = mcsolidΔT). According to thermochemistry, the relation between the amount of heat absorbed or released by a substance, q, and its...
For instance, the addition of heat raises the temperature of a solid; the amount of heat absorbed depends on the heat capacity of the solid (q = mcsolidΔT). According to thermochemistry, the relation between the amount of heat absorbed or released by a substance, q, and its...
Enthalpy of Solution
There are two criteria that favor, but do not guarantee, the spontaneous formation of a solution:
Aqueous Solutions and Heats of Hydration
Water and other polar molecules are attracted to ions. The electrostatic attraction between an ion and a molecule with a dipole is called an ion-dipole attraction. These attractions play an important role in the dissolution of ionic compounds in water.
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
Volatilization
Volatilization gravimetry is an analytical technique that measures the mass lost due to the volatilization of the substance. This technique is used to estimate the amount of volatile material in a sample. To perform this method, heat a known amount of the sample to a high temperature in a crucible or other suitable vessel. The volatile substance in the sample evaporates, and the vapor is completely expelled from the crucible either by heating the sample or bubbling a stream of inert gas through...


