Customer publications

Concentration-Induced Association in a Protein System Caused by a Highly Directional Patch Attraction

Li, Weimin; Persson, Björn A.; Lund, Mikael; Bergenholtz, Johan; Zackrisson Oskolkova, Malin

By 12 March 2019No Comments

The Journal of Physical Chemistry B, 2016, vol 120, 34, pp. 8953-8959



Self-association of the protein lactoferrin is studied in solution using small-angle X-ray scattering techniques. Effective static structure factors have been shown to exhibit either a monotonic or a nonmonotonic dependence on protein concentration in the small wavevector limit, depending on salt concentration. The behavior correlates with a nonmonotonic dependence of the second virial coefficient on salt concentration, such that a maximum appears in the structure factor at a low protein concentration when the second virial coefficient is negative and close to a minimum. The results are interpreted in terms of an integral equation theory with explicit dimers, formulated by Wertheim, which provides a consistent framework able to explain the behavior in terms of a monomer–dimer equilibrium that appears because of a highly directional patch attraction. Short attraction ranges preclude trimer formation, which explains why the protein system behaves as if it were subject to a concentration-dependent isotropic protein–protein attraction. Superimposing an isotropic interaction, comprising screened Coulomb repulsion and van der Waals attraction, on the patch attraction allows for a semiquantitative modeling of the complete transition pathway from monomers in the dilute limit to monomer–dimer systems at somewhat higher protein concentrations.

Visit the full article

Back to the overview