✍ Scribed by EugÉNe Fredericq
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The binding of picrate, tropeolin, flavianate, naphthol orange, indigo di‐, tri‐and tetrasulphonate anions by serum albumin at pH 4.7 and 3.5 was determined by dialysis at 25°. It is shown that the experimental curves cannot be interpreted by the Scatchard equation and the Debye‐Hückel theory. The charge effect is always much lower than that predicted by the theory. It is proposed to include in the binding equation a term for the Van der Waals energy of interaction. By a consideration of experimental affinities of association, it is possible to estimate the contributions of different energies: electrostatic interactions of charged groups (3,500‐4,500 cal.) and Van der Waals energy increment provided by —CH~2~—(350 cal.), benzene (1000 cal.) and naphthalene (2,500 cal.) rings. The effect of substituents in the aromatic nuclei is also explained by the consideration of Van der Waals energy and hydrogen bonds.
Association constants of anions and serumalbumin or insulin are determined in mixed solvents at pH 3.5 and 6.6. In all cases the association constants strongly weaken in 20% dioxane and practically vanish in 40% dioxane. These facts are in agreement with the hypothesis that electrostatic interactions are greatly exceeded by Van der Waals forces arising between proteins, large anions and solvent molecules.
📜 SIMILAR VOLUMES
The influence of serum albumin, ovalbumin and insulin on the absorption spectra of organic anions in solution is investigated in the visible range. The spectra of azo-dyes, phthaleins, indigosulphonates and anthraquinone dyes are affected in the same way by the three proteins: there is a general dep
## Interactions de protbines et d'ions en solution 1. Influences de structure dans les associations entre prot6ines et anions organiques par EugBne FREDERICQ (Likge) SUMMARY. -The binding of aromatic anions by bovine serum albumin at pH 6,6 and 3,5 and by insulin at pH 5,5, in 0.1 N phcsphate bu