  Recent experimental studies have shown that amyloid fibril formed by
aggregation of {\beta} peptide exhibits excellent mechanical properties
comparable to other protein materials such as actin filaments and microtubules.
These excellent mechanical properties of amyloid fibrils are related to their
functional role in disease expression. This indicates the necessity to
understand how an amyloid fibril achieves the remarkable mechanical properties
through self-aggregation with structural hierarchy, highlighting the
structure-property-function relationship for amyloids, whereas such
relationship still remains elusive. In this work, we have studied the
mechanical properties of human islet amyloid polypeptide (hIAPP) with respect
to its structural hierarchies and structural shapes by coarse-grained normal
mode analysis. Our simulation shows that hIAPP fibril can achieve the excellent
bending rigidity via specific aggregation pattern such as antiparallel stacking
of {\beta} peptides. Moreover, we have found the length-dependent mechanical
properties of amyloids. This length-dependent property has been elucidated from
Timoshenko beam model that takes into account the shear effect on the bending
of amyloids. In summary, our study sheds light on the importance of not only
the molecular architecture, which encodes the mechanical properties of the
fibril, but also the shear effect on the mechanical (bending) behavior of the
fibril.
