ABSTRACT
A major advantage in the assembly of natural biological materials
is their self-assembly from building blocks that allows for efficient
and precise assembly processes under non-aggressive conditions,
such as ambient temperatures and aqueous environments. This is
demonstrated in numerous examples in Nature: complex macro-
molecular assemblies such as bacterial flagella, or microtubules of
the cytoskeleton are built through the orchestrated assembly of
protein subunits [1, 2]. Viral capsids, either fibrous or icosahedral,
result from the precise packaging of hundreds or thousands of
protein subunits with exquisite precision and efficiency [3, 4].
Natural fibrous materials, such as collagen, elastin, silk, and spider
silks are proteins of big molecular mass and are most often built
from amino acid sequence repeats within the same polypeptide
chain [5-7]. Two basic “modules” of structure are at the basis
of protein architecture: the alpha-helix and the beta-sheet. In the
alpha-helix, the polypeptide chain adopts a spiral-like conformation,
stabilized with hydrogen bonds between the CO groups of the amino
acid i with the NH group of the amino acid i+ 4. In the beta-sheet conformation the chain adopts an elongated conformation and is
stabilized by hydrogen bonds between amino acids that could be far
apart in the primary sequence.
