  We study the folding thermodynamics of a beta-hairpin and two three-stranded
beta-sheet peptides using a simplified sequence-based all-atom model, in which
folding is driven mainly by backbone hydrogen bonding and effective hydrophobic
attraction. The native populations obtained for these three sequences are in
good agreement with experimental data. We also show that the apparent native
population depends on which observable is studied; the hydrophobicity energy
and the number of native hydrogen bonds give different results. The magnitude
of this dependence matches well with the results obtained in two different
experiments on the beta-hairpin.
