Odahara Takayuki, Odahara Koji
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central-6, 1-1 Higashi, Tsukuba, Ibaraki, 305-8566 Japan.
Fukuoka Prefectural Association of Agricultural Production and Materials, Fukuoka Prefectural Office, Hakata, Fukuoka, 812-8577 Japan.
Heliyon. 2018 Dec 27;4(12):e01073. doi: 10.1016/j.heliyon.2018.e01073. eCollection 2018 Dec.
Salt/polyethylene glycol (PEG) mixtures are employed as precipitants for biological macromolecules. The dependence of precipitation curves (PCs) on salt species was investigated for integral membrane protein/detergent particles. By relating this dependence to properties of ions dissociated from added salts, the following roles and effects of various ions were clarified. In the presence of ions whose interaction with water is stronger than water-water interaction, the coordination of solvent molecules is rearranged so as to strengthen short-range steric repulsion and hydrophobic attraction. Ions whose interaction with water is weaker than water-water interaction can be a hindrance to hydrophobic-hydrophobic contact. Moreover, strong electric fields of divalent cations can cause an attractive effect between electronegative or polar groups of neighboring particles. The variations of particle-particle and particle-PEG interactions depending on the state of particles and surrounding solvents were correlative. Due to this, the relationship between the horizontal positions of PC and the species of salts added could be formulated as a binary linear function of cationic and anionic species composing the salts.
盐/聚乙二醇（PEG）混合物被用作生物大分子的沉淀剂。针对整合膜蛋白/去污剂颗粒，研究了沉淀曲线（PCs）对盐种类的依赖性。通过将这种依赖性与添加盐解离出的离子性质相关联，阐明了各种离子的以下作用和影响。在与水的相互作用强于水-水相互作用的离子存在下，溶剂分子的配位会重新排列，以增强短程空间排斥和疏水吸引力。与水的相互作用弱于水-水相互作用的离子会阻碍疏水-疏水接触。此外，二价阳离子的强电场可在相邻颗粒的电负性或极性基团之间产生吸引作用。颗粒-颗粒和颗粒-PEG相互作用的变化取决于颗粒状态和周围溶剂，它们是相关的。因此，PC水平位置与添加盐种类之间的关系可以表示为构成盐的阳离子和阴离子种类的二元线性函数。
