(770g) Complexation in Globular Protein and Polyelectrolyte Mixtures: Effect of Charge Regulation and Patchiness

Globular proteins are known to phase separate with like charged polyelectrolytes. This
phenomenon has been observed in experiments and contented to occur due to two
main reasons. One of the explanation is charge regulation i.e. the dissociation of protein
in presence of the polyelectrolyte is such that it favors their association. The other
explanation depends on charge anisotropy i.e. presence of a local oppositely charge
patch on the protein which drives association with the polyelectrolyte. Evidences of such
a phenomenon exists in previous experimental and theoretical works. However they
pertain to very specific proteins. Motivated by the lack of general understanding of the
phenomenon, we present here the adsorption and bridging characteristics of a protein in
presence of multiple polyelectrolytes with the help of spherical particle models of
globular proteins with uniform and patches of pH-dependent charges. We used a hybrid
computational method of single chain in mean field theory with solution of Poison’s
equation and constant pH method in a semi-grand canonical framework to address the
local dissociation of annealed charges. We studied the effect of strength of dissociation
of proteins and polyelectrolytes (pH-pK_A ), concentration of polyelectrolytes and the net
charge of them in the realm of electrostatic interactions. We have considered both
oppositely charged and same charged protein and polyelectrolyte systems.
Understanding gained our study can also be extended to explore assembly of weakly
charged spherical nanoparticles and polyelectrolyte solution.