Electrostatics in Macromolecular Solutions - Food Colloids: Self-Assembly and Material Science - page 138

Figure 6 Interaction between an smMLCK peptide and a fragment of calmodulin. The net

charge of smMLCK is +7e and the calmodulin fragment has a charge of 8e.
(a) The salt concentration is 4 mM. The solid thick line is the simulated-free
energy of interaction, while the thin line is the corresponding screened Coulomb
interaction. The thin line with filled circles is the simulated total energy of
interaction. (b) The effect of added salt on the free energy of interaction

where for convenience we have introduced the Bjerrum length, l B ¼ e 2 /
4 pe 0 e r kT. Note that A(r)isafree energy. Figure 5 shows that the screened
Coulomb potential is a good approximation, and it is semi-quantitatively
correct at both salt concentrations.
The results presented here for these particular peptides is generic; it is found in
many cases with charged macromolecules or particles. The geometry is not