  Single molecule manipulation techniques reveal that the mechanical resistance
of a protein depends on the direction of the applied force. Using a lattice
model of polymers, we show that changing the pulling direction leads to
different phase diagrams. The simple model proposed here indicates that in one
case the system undergoes a transition akin to the unzipping of a $\beta$
sheet, while in the other case the transition is of a shearing (slippage)
nature. Our results are qualitatively similar to experimental results. This
demonstrates the importance of varying the pulling direction since this may
yield enhanced insights into the molecular interactions responsible for the
stability of biomolecules.
