Enhanced protein steering: cooperative electrostatic and van der Waals forces in antigen-antibody complexes.

We study the association of the cationic protein lysozyme with several almost neutral protein fragments but with highly uneven charge distributions. Using mesoscopic protein models, we show how electrostatic interactions can align or steer protein complexes into specific constellations dictated by the specific charge distributions of the interacting biomolecules. Including van der Waals forces significantly amplifies the electrostatically induced orientational steering at physiological solution conditions, demonstrating that different intermolecular interactions can work in a cooperative way in order to optimize specific biochemical mechanisms. Individually, the electrostatic and van der Waals interactions lead only to a relatively weak intermolecular alignment, but when combined, the effect increases significantly.