title: A study of selective adsorption of Na+ and other alkali-metal ions on isolated proteins: a test of the salt-linkage hypothesis.
abstract: According to the salt-linkage hypothesis (a part of the association-induction hypothesis), the binding of alkali-metal ions on isolated proteins may be low as a result of the masking of cation-binding fixed anionic groups by the formation of "salt linkages" between them and fixed cationic groups. This hypothesis has been verified in a quantitative manner by the measurement of free and adsorbed Na+ in solutions of bovine hemoglobin titrated with increasing concentration of NaOH. In addition this communication presents data indicating (1) wide variability in the extent of Na+ adsorption among different isolated proteins and even among different samples of the same protein, (2) auto-cooperativity in the pH titration and Na+ adsorption, and (3) selectivity of the liberated fixed anionic groups for different alkali-metal ions in the rank order Na greater than Li greater than K greater than Rb, Cs.
mesh_terms: D000327:Adsorption; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D008954:Models, Biological; D011485:Protein Binding; D012964:Sodium / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D008670:Metals; D012964:Sodium