Self-Assembly of Synthetic and Biological Polymeric Systems of ...

The physical and chemical properties of proteins are an attractive alternative for the
construction of nanoestructured materials, providing an extraordinary array of functionalities
that could be exploited in fields such as biomedicine, biotechnology, materials science, and
nanotechnology (145). Protein amyloids are excellent candidates for the fabrication of
molecular nanobiomaterials, such wires, layers, gels, scaffolds, templates, and liquid crystals,
using the bottom-up strategy as a result of their outstanding physico-chemical properties
(great stiffness, stable against heat and denaturants, resistant to proteases, amongst others)
structural compatibility, nanoscale dimensions and efficient assembly into well-defined
ultrastructures (146)(147).
On the other hand, metal nanoparticles (NP) have received considerable attention during last
decade because of their particular optical, electronic, magnetic and catalytic properties and
their important applications in many fields such as nanosensors, catalysis, biomedicine,
biological, labelling, and surface-enhanced Raman scattering (SERS). To optimize and extend
the applications of metal NPs, methods must be developed to control the assembly and
organization of these nanomaterials. NPs in ordered arrays provide optical and electronic
properties that are distinct compared to individual particles or disorganized macroscale
agglomerations. In this way, the supramolecular structure of amyloid fibrils can be used to
organize nanoparticles into predefined, topologically intricate nanostructures, or synthesize
miscellaneous materials in order to control the properties of nanoparticle assemblies for
potential applications in electronic, optical, and chemical devices. In particular, functionalizing
one-dimensional (1D) supporting biomaterials with metal NPs that combine the properties of
two functional materials, such as the high conductivity, surface area or the precise chemical
functionality of the biotemplate, and the unique plasmonic or catalytic properties of the metal
NPs widen their range of applications and, therefore, their important role in nanoscience and
nanotechnology (148)-(151).
5.5.1 Hen egg-white lysozyme
Hen egg-white lysozyme (HEWL) is a relatively small globular, monomeric protein. HEWL
consist of a polypeptide chain with 129 amino acid residues with four disulfide bonds, and it
folds into two structural domains, the α and β ones. The α domain contains a core of
hydrophobic side chains that are packed closely together (152); this domain consists of three
long helices A (5-15), B (25-35) and C (89-99) (153). In contrast, the β domain of the protein
does not display a similar hydrophobic core; instead, hydrogen bonds and a number of small
hydrophobic clusters appear to be responsible for defining its tertiary fold, and there is also an
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