The effect of buffer concentration on the dynamic/equilibrium surface tension of bovine serum albumin solution

Abstract

The effect of phosphate buffer (Na2HPO4 and NaH2PO4) concentration on the dynamic and equilibrium surface tension (ST) of bovine serum albumin (BSA) solutions was examined in this study. A pendant bubble tensiometer was utilized for measuring the ST relaxation of BSA solutions in varying buffer concentration (0, 0.01–300 mM). The data showed: (i) an initial increase in buffer concentration (Cbuff < 0.3 mM) resulted in a slower ST relaxation and a notable rise in the equilibrium ST; (ii) a further rise in buffer concentration (Cbuff > 0.3 mM) resulted in a faster ST relaxation and a progressive decrease in the equilibrium ST; and (iii) despite an increase in BSA concentration from 2 to 15 (10−10 mol/cm3), the dynamic ST of BSA solutions always relaxed the slowest at Cbuff = 0.3 mM. The equilibrium ST of BSA solutions in 10 and 44 mM buffer [C = 0.1–15 (10−10 mol/cm3)] was also obtained and the data confirmed the near-constant equilibrium ST of purely aqueous BSA solutions [Le et al., J.Mol.Liq (2022) 118305] to not be an anomalous behavior but, observable irrespective of the solvent formulation.