where we have assumed for simplicity a Dirac-like distribution on a sphere, λ → ∞. The electrostatic part ξ kt is thus the one that underpins the difference between the pH dependence of q 2 and p 2 . The stronger the electrostatic coupling in Eq. ( ), the more the fluctuations deviate from locality and exhibit a collective behavior which acts to screen out the details in this dependence.