Microscopic simulations of macroscopic dielectric constants of solvated proteins

Microscopic simulation of solvated proteins are used to evaluate the relationship between the macroscopic field and macroscopic polarization, thus providing the corresponding dielectric constant, e. This parameter is evaluated by two different methods which are first examined and calibrated by calculating the dielectric constant of bulk water. These calculations indicate that the reaction field, which represents the effect of the missing solvent around the given explicit region, must be included in the simulations in order to obtain a reasonable value for e. The corresponding effect is not related to the reduction of the effective interactions between charges in the reference region but to the intrinsic value of e in that region. This means that vacuum calculations of e in proteins might underestimate its actual value. Or in other words, calculations of e in proteins must include the effect of the reaction field or a sufficiently large number of surrounding solvent molecules. Having included the surr...