  Mechanical unfolding of the fourth domain of Distyostelium discoideum filamin
(DDFLN4) was studied in detail using the C$_{\alpha}$-Go model. We show that
unfolding pathways of this protein depend on the pulling speed. The agreement
between theoretical and experimental results on the sequencing of unfolding
events is achieved at low loading rates. The unfolding free energy landscape is
also constructed using dependencies of unfolding forces on pulling speeds.
