PreSSAPro is a software, available to the scientific community as a free web 
service designed to provide predictions of secondary structures starting from 
the amino acid sequence of a given protein. Predictions are based on our 
recently published work on the amino acid propensities for secondary structures 
in either large but not homogeneous protein data sets, as well as in smaller but 
homogeneous data sets corresponding to protein structural classes, i.e. 
all-alpha, all-beta, or alpha-beta proteins. Predictions result improved by the 
use of propensities evaluated for the right protein class. PreSSAPro predicts 
the secondary structure according to the right protein class, if known, or gives 
a multiple prediction with reference to the different structural classes. The 
comparison of these predictions represents a novel tool to evaluate what 
sequence regions can assume different secondary structures depending on the 
structural class assignment, in the perspective of identifying proteins able to 
fold in different conformations. The service is available at the URL 
http://bioinformatica.isa.cnr.it/PRESSAPRO/.