Pex are created to extract numeric and string descriptions of protein struc
tures from PDB files. This concerns covalent bond lengths and angles, secon
dary structures, residues in interaction, H-bond lengths and geometry, etc.
Several kinds of Pex are generated: (1) general feature (GF-Pex); (2) H-bo
nd (H-Pex); and (3) accessible surface (AS-Pex) and force potential (FP-Pex
). We describe the general principles of Pex and detail the GF-Pex files. U
sing the GF-Pex of 131 proteins, we analyze the mean residue frequencies, t
he phi/psi distribution and the major kinds of secondary structures in prot
eins. Thomas et al. (this issue) analyzes the main chain H-bonds in those p
roteins. The GF-Pex and H-Pex files of the 131 proteins can be down loaded
from the CBMN site (http://www.fsagx.ac.be/bp/). Proteins 2001;43:28-36. (C
) 2001 Wiley Liss, Inc.