Spider Silk - The Functional Fold: Amyloid Structures in Nature - page 76

There are three more structural silk classes which can be found
among insects such as collagen-like silk, polyglycine II-like structures,
and cuticulin-silk.

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Although all silks display good mechanical properties, spider
dragline silks are superior in combining strength and elasticity,
resulting in an extraordinary toughness which can match with that
of high-performance synthetic polymers such as nylon or Kevlar
(Table 5.2).

Table 5.2 The mechanical properties of different natural and synthetic

high-performance fibres (numbers taken from Gosline . 8 ) et al

Stiffness
E init (GPa)

Strength
σ max (GPa)

Extensibility
ε max

Toughness
MJ m -3 Material

Dragline silk
(Araneus
diadematus)

10 1.1 0.27 160

Cocoon silk
(Bombyx
mori)

7 0.6 0.18 70

Collagen
(Mammalian
tendon)

1.5 0.15 0.12 7.5

Nylon fiber 5 0.95 0.188 80

Kevlar 49
fiber

130 3.6 0.027 50

Carbon fiber 300 4 0.013 25

High-tensile
steel

200 1.5 0.008 6

Dragline silk combines high tensile strength (1.1 GPa) with good
extensibility (0.27) yielding an outstanding toughness (160 MJ/m

3

)
succeeding that of all other displayed materials. Dragline silks
are composed of proteins which are produced in the major

ampullate gland consisting of a long tail and a wide sac reflecting
the compartment where the proteins are stored. Within the glands
extremely high protein concentrations of up to 50% (w/v) exist
forming the so-called spinning dope (Fig. 5.2).

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