This article describes a combined experimental, theoretical, and computatio
nal effort to show how the complexity of aqueous hydration can influence th
e structure, folding and aggregation, and stability of model protein system
s. The unification of the theoretical and experimental work is the developm
ent or discovery of effective amino acid interactions that implicitly inclu
de the effects of aqueous solvent. We show that consideration of the full r
ange of complexity of aqueous hydration forces such as many-body effects, l
ong-ranged character of aqueous solvation, and the assumptions made about t
he degree of protein hydrophobicity can directly impact the observed struct
ure, folding, and stability of model protein systems.