I was reading that hidden surface with a lot of hydrophobic groups is considered an entropic advantage. To expand the question, is it entropic advantage when buried residues are long chained? Is there a quantitative comparison between amino acids?
When two hydrophobic surfaces come together water is expelled into the "bulk phase". When two hydrophilic surfaces come together, as in the formation of a hydrogen bond, water is also expelled into the "bulk phase". In both cases there is some loss of entropy as the interacting surfaces become more "fixed" while there is an increase in entropy as the water gets released. Usually the latter outweighs the former i.e. there is a net gain in entropy due to these desolvation mechanisms. The two types of interaction are different quantum mechanically but the results in terms of entropy are pretty similar.