title: The efficiency of different salts to screen charge interactions in proteins: a Hofmeister effect?
abstract: Understanding the screening by salts of charge-charge interactions in proteins is important for at least two reasons: a), screening by intracellular salt concentration may modulate the stability and interactions of proteins in vivo; and b), the in vitro experimental estimation of the contributions from charge-charge interactions to molecular processes involving proteins is generally carried out on the basis of the salt effect on process energetics, under the assumption that these interactions are screened out by moderate salt concentrations. Here, we explore experimentally the extent to which the screening efficiency depends on the nature of the salt. To this end, we have carried out an energetic characterization of the effect of NaCl (a nondenaturing salt), guanidinium chloride (a denaturing salt), and guanidinium thiocyanate (a stronger denaturant) on the stability of the wild-type form and a T14K variant of Escherichia coli thioredoxin. Our results suggest that the efficiency of different salts to screen charge-charge interactions correlates with their denaturing strength and with the position of the constituent ions in the Hofmeister rankings. This result appears consistent with the plausible relation of the Hofmeister rankings with the extent of solute accumulation/exclusion from protein surfaces.
authors.affiliation: Facultad de Ciencias, Departamento de Quimica Fisica, Universidad de Granada, 18071 Granada, Spain.
authors.forename: Raul
authors.initials: R
authors.lastname: Perez-Jimenez
authors.forename: Raquel
authors.initials: R
authors.lastname: Godoy-Ruiz
authors.forename: Beatriz
authors.initials: B
authors.lastname: Ibarra-Molero
authors.forename: Jose M
authors.initials: JM
authors.lastname: Sanchez-Ruiz
mesh_terms: D000465:Algorithms; D002942:Circular Dichroism; D004926:Escherichia coli / Q000737:chemistry; D019791:Guanidine / Q000494:pharmacology*; D006146:Guanidines / Q000494:pharmacology*; D008958:Models, Molecular; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology*; D055672:Static Electricity; D013816:Thermodynamics; D013861:Thiocyanates / Q000494:pharmacology*; D013879:Thioredoxins / Q000737:chemistry*
chemical_list: D006146:Guanidines; D013861:Thiocyanates; D012965:Sodium Chloride; D013879:Thioredoxins; C054436:guanidine thiocyanate; D019791:Guanidine