Theoretical study of steric effects in electrolyte solutions: Toward thorough understanding of Hofmester effect

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K03562
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13040:Biophysics, chemical physics and soft matter physics-related
• Research Institution: Okayama University
• Principal Investigator: Okamoto Ryuichi 岡山大学, 異分野基礎科学研究所, 特任講師 (10636385)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 電解質溶液 / 排除体積効果 / イオン / 静電相互作用 / 溶媒誘起相互作用

Outline of Final Research Achievements

In dilute electrolyte solutions, there exist universal laws such as the Debye-Huckel law of the activity coefficient. As the ion concentration increases, ion-specificity becomes more noticeable; ion-specificity means ions with the same valence numbers have different effects on the properties of solutions. The two major achievements are as follows. (i) we showed that the ion-specificities in the ion activity coefficient, osmotic coefficient, and salt partial volume are explained as a result of combination of steric effects of the ions and the solvent and the electrostriction of ions. (ii) For solutions of hydrophobic molecules, we found a simple relationship between the ion effects on the solubility and the hydrophobic interaction. The latter is relevant to the conformation of macromolecules, e.g., DNAs, proteins in salt solutions.

Free Research Field

化学物理，ソフトマター物理

Academic Significance and Societal Importance of the Research Achievements

近年，計算機の発展とともにイオン固有性の分子的詳細の様々な側面が明らかになってきた．反面，シンプルな物理的描像による理論的理解は(それが可能であるかどうかも含めて)得られていなかった．この成果は今後の理論のみならず，計算機による分子的詳細の研究，実験研究にも指針を与えると期待される．特に，塩溶液中における疎水性分子の溶解度と疎水性相互作用の間の単純な関係式は今後の計算機シミュレーションによる検証が待たれる．また，タンパク質やDNA溶液への塩効果のようなは生物学や化学工学において重要な研究の端緒となることが期待できる．