1-Anilino-8-naphthalene sulfonate anion-protein binding depends primarily on ion pair formation

Biophys J. 1998 Jan;74(1):422-9. doi: 10.1016/S0006-3495(98)77799-9.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Anilino Naphthalenesulfonates / chemistry*
  • Anilino Naphthalenesulfonates / metabolism
  • Animals
  • Anions
  • Binding Sites
  • Cations
  • Cattle
  • Dialysis
  • Fluorescent Dyes
  • Histidine*
  • Hydrogen-Ion Concentration
  • Kinetics
  • Muramidase / chemistry*
  • Muramidase / metabolism
  • Papain / chemistry*
  • Papain / metabolism
  • Peptides
  • Polylysine
  • Protein Binding
  • Serum Albumin, Bovine / chemistry*
  • Serum Albumin, Bovine / metabolism


  • Anilino Naphthalenesulfonates
  • Anions
  • Cations
  • Fluorescent Dyes
  • Peptides
  • Polylysine
  • polyarginine
  • polyhistidine
  • Serum Albumin, Bovine
  • Histidine
  • 1-anilino-8-naphthalenesulfonate
  • Muramidase
  • Papain