Centro de Física de Materiales - Material Physics Centre (MPC), CSIC - Universidad del País Vasco (UPV/EHU), Paseo Manuel de Lardizabal 5, 20018, San Sebastian, Spain.
Phys Chem Chem Phys. 2012 Aug 28;14(32):11352-62. doi: 10.1039/c2cp41496a. Epub 2012 Jul 16.
The complex dielectric permittivity of eight different amino acids in water solutions was determined in the frequency range from 0.2 to 20 GHz at room temperature, trying to span the whole range of solubility in each case. Two relaxations were observed at room temperature in this frequency range, which can be mainly assigned to the rotation of amino acids in the aqueous environment, and the reorientational motion of water molecules, respectively. Although the amino acids have a charged (zwitterionic) nature with huge dipole moments, the tendency towards dipolar alignment seems to be very weak, over the investigated concentration ranges. For these small bio-molecules, water screens solute-solute interactions and amino acids remain typically as isolated hydrated monomers. The dielectric results were used to estimate the number of water molecules restrained by each solute molecule. Finally, the comparison between the amino acid relaxation times made it possible to discuss the relationship between rotational dynamics and the structure and hydrodynamic coupling of the amino acid studied.
在室温下，我们测定了 8 种不同氨基酸在水溶液中的复介电常数，频率范围从 0.2 到 20GHz，试图涵盖每种物质的整个溶解度范围。在这个频率范围内，室温下观察到两种弛豫，它们可以主要分配给氨基酸在水环境中的旋转，以及水分子的重取向运动。尽管氨基酸具有带电荷（两性离子）的性质和巨大的偶极矩，但在研究的浓度范围内，偶极对齐的趋势似乎非常微弱。对于这些小分子生物分子，水屏蔽了溶质-溶质相互作用，氨基酸通常保持为孤立的水合单体。介电结果用于估计每个溶质分子约束的水分子数量。最后，通过比较氨基酸的弛豫时间，我们可以讨论旋转动力学与所研究的氨基酸的结构和流体动力耦合之间的关系。
