  We calculate thermodynamic quantities of HP lattice proteins by means of a
multicanonical chain growth algorithm that connects the new variants of the
Pruned-Enriched Rosenbluth Method (nPERM) and flat histogram sampling of the
entire energy space. Since our method directly simulates the density of states,
we obtain results for thermodynamic quantities of the system for all
temperatures. In particular, this algorithm enables us to accurately simulate
the usually difficult accessible low-temperature region. Therefore, it becomes
possible to perform detailed analyses of the low-temperature transition between
ground states and compact globules.
