title: Ion hydration: Implications for cellular function, polyelectrolytes, and protein crystallization.
abstract: Only oppositely charged ions with matching absolute free energies of hydration spontaneously form inner sphere ion pairs in free solution [K.D.Collins, Ions from the Hofmeister series and osmolytes: effects on proteins in solution and in the crystallization process, Methods 34 (2004) 300-311.]. We approximate this with a Law of Matching Water Affinities which is used to examine the issues of (1) how ions are selected to be compatible with the high solubility requirements of cytosolic components; (2) how cytosolic components tend to interact weakly, so that association or dissociation can be driven by environmental signals; (3) how polyelectrolytes (nucleic acids) differ from isolated charges (in proteins); (4) how ions, osmolytes and polymers are used to crystallize proteins; and (5) how the "chelate effect" is used by macromolecules to bind ions at specific sites even when there is a mismatch in water affinity between the ion and the macromolecular ligands.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Maryland Medical School, 108 N. Greene Street, Baltimore, MD 21201-1503, USA. kcollins@umaryland.edu
authors.forename: Kim D
authors.initials: KD
authors.lastname: Collins
mesh_terms: D003460:Crystallization; D003600:Cytosol / Q000378:metabolism; D007477:Ions / Q000737:chemistry*; D009696:Nucleic Acids / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D007477:Ions; D009696:Nucleic Acids; D011506:Proteins; D014867:Water