390
The mechanical properties of the resulting IFs-based network determine the
functional properties of hagfi sh slime. Recent works on the mechanical properties
of fi bres isolated from hagfi sh slime (Fudge et al. 2003 , 2005 ; Lim et al. 2006 ;
Hearle 2008 ) suggest that these unique fi brillar constructs may one day be replicated in a way that is economically viable and environmentally sustainable. Ewoldt
et al. ( 2011 ) reported “the fi rst experimental measurements of nonlinear rheological
material properties of hagfi sh slime as a hydrated biopolymer/biofi ber network, and
developed a microstructural constitutive model to explain the observed nonlinear
viscoelastic behavior. The linear elastic modulus of the network is observed to be G′
about 0.02 Pa for timescales 0.1–10 s, making it one of the softest elastic biomaterials known,” (Ewoldt et al. 2011 ). “Furthermore, the peculiar nature of hagfi sh slime
inspires the possibility of a bio-inspired ultra-dilute elastic network which can be
similarly deployed as a defensive mechanism for engineered systems,” (Ewoldt
et al. 2011 ).
Recently, hagfi sh slime threads have been proposed as “a biomimetic model for
high performance protein fi bres,” (Fudge et al. 2010 ) in contrast to silk-like proteins. Douglas Fudge described the state of the art concerning this scientifi c direction as follow:
“The genes for these nanofi brous proteins, are far smaller than spidroin genes
and not repetitive, making them more suitable for expression in bacteria. Another
feature that makes them an attractive model is that they self-assemble from soluble
precursors into 10 nm fi laments in aqueous buffers. The key to the high strength and
toughness of spider silk and hagfi sh threads is the β-sheet crystallites that simultaneously cross-link the protein molecules and arrange them into a structure in which
‘sacrifi cial bonds’ increase the energy required to break the material. The α → β
transition occurs far more readily in hagfi sh slime threads than it does in hard
α-keratins, because slime threads lack elastomeric matrix proteins. In α-keratins
resist these proteins swelling in water, and also provide a restoring force during and
after longitudinal extension. Future work will focus on a more detailed characterization of the effects of cross-linking and annealing on fi ber mechanics and structure,
both in native slime threads and those that are produced from recombinant or
isolated protein,” (Fudge et al. 2010 ; see also Fudge and Gosline 2004 ; Koch et al.
1991 , 1994 , 1995 ).
11.3 Whale Baleen
Mysticeti and Odontoceti are the two suborders of the Cetacea order, which includes
such marine mammals as dolphins, porpoises, and whales (Uhen 2010 ).
Representatives of Mysticeti and Odontoceti whales differ from each other due to
their feeding mechanism. The Mysticeti possess a special baleen-based fi ltration
system, however the Odontoceti are equipped with teeth to tear their food (Werth
2001 ). “Cladistic analyses of living and extinct mysticetes support the hypothesis
that mineralized teeth were lost in the common ancestor of crown Mysticeti,”
11 Marine Keratins
The mechanical properties of the resulting IFs-based network determine the
functional properties of hagfi sh slime. Recent works on the mechanical properties
of fi bres isolated from hagfi sh slime (Fudge et al. 2003 , 2005 ; Lim et al. 2006 ;
Hearle 2008 ) suggest that these unique fi brillar constructs may one day be replicated in a way that is economically viable and environmentally sustainable. Ewoldt
et al. ( 2011 ) reported “the fi rst experimental measurements of nonlinear rheological
material properties of hagfi sh slime as a hydrated biopolymer/biofi ber network, and
developed a microstructural constitutive model to explain the observed nonlinear
viscoelastic behavior. The linear elastic modulus of the network is observed to be G′
about 0.02 Pa for timescales 0.1–10 s, making it one of the softest elastic biomaterials known,” (Ewoldt et al. 2011 ). “Furthermore, the peculiar nature of hagfi sh slime
inspires the possibility of a bio-inspired ultra-dilute elastic network which can be
similarly deployed as a defensive mechanism for engineered systems,” (Ewoldt
et al. 2011 ).
Recently, hagfi sh slime threads have been proposed as “a biomimetic model for
high performance protein fi bres,” (Fudge et al. 2010 ) in contrast to silk-like proteins. Douglas Fudge described the state of the art concerning this scientifi c direction as follow:
“The genes for these nanofi brous proteins, are far smaller than spidroin genes
and not repetitive, making them more suitable for expression in bacteria. Another
feature that makes them an attractive model is that they self-assemble from soluble
precursors into 10 nm fi laments in aqueous buffers. The key to the high strength and
toughness of spider silk and hagfi sh threads is the β-sheet crystallites that simultaneously cross-link the protein molecules and arrange them into a structure in which
‘sacrifi cial bonds’ increase the energy required to break the material. The α → β
transition occurs far more readily in hagfi sh slime threads than it does in hard
α-keratins, because slime threads lack elastomeric matrix proteins. In α-keratins
resist these proteins swelling in water, and also provide a restoring force during and
after longitudinal extension. Future work will focus on a more detailed characterization of the effects of cross-linking and annealing on fi ber mechanics and structure,
both in native slime threads and those that are produced from recombinant or
isolated protein,” (Fudge et al. 2010 ; see also Fudge and Gosline 2004 ; Koch et al.
1991 , 1994 , 1995 ).
11.3 Whale Baleen
Mysticeti and Odontoceti are the two suborders of the Cetacea order, which includes
such marine mammals as dolphins, porpoises, and whales (Uhen 2010 ).
Representatives of Mysticeti and Odontoceti whales differ from each other due to
their feeding mechanism. The Mysticeti possess a special baleen-based fi ltration
system, however the Odontoceti are equipped with teeth to tear their food (Werth
2001 ). “Cladistic analyses of living and extinct mysticetes support the hypothesis
that mineralized teeth were lost in the common ancestor of crown Mysticeti,”
11 Marine Keratins