Physicochemical properties of ion pairs of biological macromolecules

Junji Iwahara, Alexandre Esadze, Levani Zandarashvili

Research output: Contribution to journalReview articlepeer-review

29 Scopus citations


Ion pairs (also known as salt bridges) of electrostatically interacting cationic and anionic moieties are important for proteins and nucleic acids to perform their function. Although numerous three-dimensional structures show ion pairs at functionally important sites of biological macromolecules and their complexes, the physicochemical properties of the ion pairs are not well understood. Crystal structures typically show a single state for each ion pair. However, recent studies have revealed the dynamic nature of the ion pairs of the biological macromolecules. Biomolecular ion pairs undergo dynamic transitions between distinct states in which the charged moieties are either in direct contact or separated by water. This dynamic behavior is reasonable in light of the fundamental concepts that were established for small ions over the last century. In this review, we introduce the physicochemical concepts relevant to the ion pairs and provide an overview of the recent advancement in biophysical research on the ion pairs of biological macromolecules.

Original languageEnglish (US)
Article numberA11
Pages (from-to)2435-2463
Number of pages29
Issue number4
StatePublished - 2015


  • Dynamics
  • Electrostatic interactions
  • Electrostriction
  • Entropy
  • Free energy
  • Ion pairs
  • Nucleic acids
  • Proteins
  • Salt bridges

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology


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