Fig 3. Fitted binding isotherms of polyphenols titrated with increasing levels of salivary mucin.

The mole fraction of polyphenol bound to mucin is plotted against the protein concentration. The concentration of EC (a), EGC (b), ECG (c), EGCG (d), methyl gallate (e), and rutin (f) was kept constant (2.5 mmol/L), whereas salivary mucin was titrated from 0 to 2.5 μmol/L or until the bound mole fraction of the ligand reached a plateau. The approximate mucin content of human whole saliva is marked by an arrow. The intercept of the fitted binding isotherm with the horizontal gray line marks the half-maximum binding concentration of the protein (BC₅₀). Error bars denote the standard deviation obtained from integrating all the distinct, non-overlaid proton signals of each compound (see methods for a list of consulted proton resonance signals). For methyl gallate only one discrete ¹H resonance signal is available for integration. *Error bars in (e) denote the technical error of two independent measurements. Data points behind means are provided in S1 Table. Binding isotherms, the BC₅₀ value, and the shape parameter α were fitted with the Gnuplot software (Version 5.0).