External parameters-namely, salt concentration and protein background dielectric constant-influence the fluctuations to various degrees. In general, changes in either of the two do not modify the pH dependence of the fluctuations to a significant extent, as can be seen from Figs. S6 and S7 in the SI on the examples of βlactoglobulin and lysozyme, respectively. Changes in salt concentration tend to lead to somewhat larger changes in the magnitude of the fluctuations compared to changes in protein dielectric constant (Fig. ), although the difference depends on the protein in question (Fig. ). Moreover, while charge fluctuations depend only on the dimensionless parameter κR (through the electrostatic coupling ] for all four proteins studied. System parameters are ε∞ = 4 and n0 = 100 mM. matrix ξ ik ), dipole fluctuations are in comparison more sensitive to the choice of the protein radius, as they feature an explicit quadratic dependence on R in the lowest order [Eq. ( )].