Among an infinite number of possible folds, nature has chosen only about 1000 distinct folds to form protein structures. Theoretical studies suggest that selected folds are intrinsically more designable than others; these selected folds are unusually stable, a property called the designability...

Many experiments done on neutral lipid bilayers in pure water show weak repulsions. These weak forces prevent vesicles from adhering and are generally overcome by adding some salt in the aqueous medium. They also appear as stray repulsions in surface forces measurements made on lipid bilayers....