Biomedical Engineering Reference
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(a)
Helical
Oligoleucine
Charged
Polylysine
(b)
fibril
axis
End-on view
with polylysine chains
Fig. 14. Drawings showing (a) representation of a block copolypeptide chain and (b) proposed
packing of block copolypeptide amphiphiles into twisted fibrillar tapes, with helices packed
perpendicular to the fibril axes. Polylysine chains were omitted from the fibril drawing for clarity.
Adapted from [126].
4. Conclusion and Outlook
Polypeptide-based block copolymers are an attractive and promising class of
block copolymer structures with a proven ability to mimic some of the basic
properties of proteins. The most notable difference between peptide-based block
copolymers and their fully synthetic and amorphous analogues is their
hierarchical solid-state organization. In contrast to most synthetic amorphous
block copolymers (which typically exhibit structural order only over a single
length scale) peptide-based block copolymers can form hierarchically organized
nanoscale structures that cover several different length scales. At the smallest
length scale, peptide sequences fold into regular secondary structures, such as α-
helices or β-strands. At the next level, peptide α-helices and β-strands can
assemble into hexagonal superstructures and β-sheets, respectively. Finally,
phase separation between the peptide and synthetic blocks leads to the formation
of ordered domains with the largest characteristic length scales. This behavior is
very similar to that of proteins for which the primary structure controls the
secondary, tertiary and quaternary structures.
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