There are two possible arrangements of these three chains, giving a “collagen 1” and a “collagen
M = 30 000
L = 280 nm = 2.80.10-7m.
Diameter = from 1.4 10-9 m to 1.5.10-9 m
The gelatine is a gel made of water dispersed in a network of collagen, which is a solid
continuous phase. Between 60 and 65°C, the collagen splits up and the triple helix is then destroyed and
a big protein network is created. By cooling, the “simple” proteins are connected together and form a
protein network, which keeps a continuous structure.
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A protein is constituted by amino acid (AA). If we know the amino acid length, we can deduct the
length of a protein, in particular, the collagen. Indeed, an amino acid is connected with another one by a
peptidic link. By neglecting the influence of the radical, we can say that an amino acid has the length of a
carbon-carbon link, and of a peptidic link: both of a length of the order of 1,5 Angstrom.
O Figure 37 : Two amino acids connected by a peptidic link
The length of an AA, on a polypeptidique chain is thus of the order of 5 angstroms, is l = 5.10-10m.
By estimate, we can assimilate an essential molecule of collagen to a chain constituted of N = L/l amino
Proteins can have various sizes due to the properties of the radicals of each amino acid. We shall
thus estimate the two extreme shapes that a polypeptidic chain can take; namely a thread for the most
developed shape and a cube of linked amino acids for the most compact shape.
If we take this molecule of its most compact shape, it would have a shape of cube of edge equal
to n. One of the faces of this cube would cover the surface of our air bubble.
Smin = ((n (1/3))*l) 2
Also, the most free shape would form a network of fibres of collagens, like a square of L. of
Smax = 1
The number of molecules of collagen necessary to create a foam bubble is thus:
n(c1b) = Sb
Let Nc be the number of bubbles which can be made using all the molecules of collagen of the