We discuss the thermodynamics of DS 0 and SO 4 CH - 2 binding to the AWI and the ACWI in Sec. III B, and discuss the effect of turning on the tail interactions (i.e. SO 4 CH - 2 → DS -) in Sec. III D, and the effect of turning on el (i.e. DS 0 → DS -) in Sec. III E. However we first discuss general two-step solvation in terms of unspecified intermediate states a and b with U = a⊕b. To do this, we introduce independent Kirkwood coupling parameters: