  The free energy of a weakly curved, isolated macroion embedded in a symmetric
1:1 electrolyte solution is calculated on the basis of linear Debye-H\"uckel
theory, thereby accounting for non-electrostatic Yukawa pair interactions
between the mobile ions and of the mobile ions with the macroion surface,
present in addition to the electrostatic Coulomb potential. The Yukawa
interactions between anion-anion, cation-cation, and anion-cation pairs are
independent from each other and serve as a model for solvent-mediated
ion-specific effects. We derive expressions for the free energy of a planar
surface, the spontaneous curvature, the bending stiffness, and the Gaussian
modulus. It is shown that a perturbation expansion, valid if the Yukawa
interactions make a small contribution to the overall free energy, yields
simple analytic results that exhibit good agreement with the general free
energy over the range of experimentally relevant interaction parameters.
