which is the result obtained by Kirkwood and Shumaker . Our theory is clearly a generalization of the latter in the sense that it takes into account the electrostatic energy of the fluctuating states. Note again that the derivations presented here are general, and F ES can be substituted with any form of electrostatic free energy of a given system. From the definitions of δq 2 and δp 2 it transpires that the pH dependence in both cases is given solely by the correlator δq k δq t . The conclusion would therefore be that both have a similar dependence on pH, the only difference being in the summation over the arclength cos γ kt in Eq. . For a vanishing electrostatic coupling (vanishing ξ kt ), the charge and dipole fluctuations become proportional in the lowest order,