  We introduce a model of proteins in which all of the key atoms in the protein
backbone are accounted for, thus extending the Freely Rotating Chain model. We
use average bond lengths and average angles from the Protein Databank as input
parameters, leaving the number of residues as a single variable. The model is
used to study the stretching of proteins in the entropic regime. The results of
our Monte Carlo simulations are found to agree well with experimental data,
suggesting that the force extension plot is universal and does not depend on
the side chains or primary structure of proteins.
