  We report 10 successfully folding events of trpzip2 by molecular dynamics
simulation. It is found that the trizip2 can fold into its native state through
different zipper pathways, depending on the ways of forming hydrophobic core.
We also find a very fast non-zipper pathway. This indicates that there may be
no inconsistencies in the current pictures of beta-hairpin folding mechanisms.
These pathways occur with different probabilities. zip-out is the most probable
one. This may explain the recent experiment that the turn formation is the
rate-limiting step for beta-hairpin folding.
