1-Anilino-8-naphthalene sulfonate anion-protein binding depends primarily on ion pair formation.
The ANS- (1-anilino-8-naphthalene sulfonate) anion is strongly, dominantly bound to cationic groups of water-soluble proteins and polyamino acids through ion pair formation. This mode of ANS- binding, broad and pH dependent, is expressed by the quite rigorous stoichiometry of ANS- bound with respect to the available summed number of H+ titrated lysine, histidine, and arginine groups. By titration calorimetry, the integral or overall enthalpies of ANS- binding to four proteins, bovine serum albumin, lysozyme, papain, and protease omega, were arithmetic sums of individual ANS(-)-polyamino acid sidechain binding enthalpies (polyhistidine, polyarginine, polylysine), weighted by numbers of such cationic groups of each protein (additivity of binding enthalpies). ANS- binding energetics to both classes of macromolecules, cationic proteins and synthetic cationic polyamino acids, is reinforced by the organic moiety (anilinonaphthalene) of ANS-. In a much narrower range of binding, where ANS- is sometimes assumed to act as a hydrophobic probe, ANS- may become fluorescent. However, the broad overall range is sharply dependent on electrostatic, ion pair formation, where the organic sulfonate group is the major determinant of binding.
Matulis
D
D
Biochemistry Department, University of Minnesota, St. Paul 55108, USA. dmatulis@biosci.cbs.umn.edu
Lovrien
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R
D000817:Anilino Naphthalenesulfonates / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D000838:Anions; D001665:Binding Sites; D002412:Cations; D002417:Cattle; D003956:Dialysis; D005456:Fluorescent Dyes; D006639:Histidine; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009113:Muramidase / Q000737:chemistry* / Q000378:metabolism; D010206:Papain / Q000737:chemistry* / Q000378:metabolism; D010455:Peptides; D011107:Polylysine; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism
D000817:Anilino Naphthalenesulfonates; D000838:Anions; D002412:Cations; D005456:Fluorescent Dyes; D010455:Peptides; D011107:Polylysine; C015462:polyarginine; C033223:polyhistidine; D012710:Serum Albumin, Bovine; D006639:Histidine; C027132:1-anilino-8-naphthalenesulfonate; D009113:Muramidase; D010206:Papain