Electrostatics in Macromolecular Solutions - Food Colloids: Self-Assembly and Material Science - page 146

Figure 10 The difference in free energy of interaction ( D A) between calbindin and
lysozyme at pH ¼ 4 for a protein model with regulation and one with fixed
charges, where R is the separation between the mass centres of the two
proteins. Symbols denote the simulated difference (see Figure 9), and the solid
line is obtained from Equation (22) with Z calb ¼ 1.16, C calb ¼ 2.23, Z lys ¼
10.2 and C lys ¼ 0.88
Figure 11 Snapshot from an MC simulation of system containing two charged macro-
molecules and an oppositely charged polyelectrolyte
adsorb to both aggregates in order to form bridges (Figure 11) leading to
attractive interactions. For highly charged polyelectrolytes and oppositely
charged macromolecules, bridge formation is usually a very effective way of
destabilization. From simulations and mean field theories, we know that the
attraction is rather short ranged and that it typically only extends over distances
of the order of the monomer-monomer separation. 22-25 Figure 12(a) shows
what happens if a polyelectrolyte salt is added to a solution of two charged
macromolecules. The double-layer repulsion is replaced by a short-range
attraction with a minimum at a surface-to-surface separation of approximately
the monomer-monomer distance.