Collagen dimensional stability

Proline represents a unique class of molecules among amino acids (Fig. 1). As pointed out by Adams, the inclusion of the a-amino group within a ring structure bestows a number of special properties (1). With its peptide bond within the pyrrolidone ring, proline confers rigidity and three-dimensional stability to proteins. The high content of proline and hy-droxyproline in collagen contributes to the unique physical properties of this structural protein. Less appreciated but perhaps equally important is... 

When collagen IV prepared from the EHS tumor is incubated at 37°C, it self-assembles, forming aggregates containing polygonal structures. These lateral associations are stabilized by the interaction between the domain NCI and sites that occur along the triple helix and are separated from one another by about 100 nm (Tsilibary and Charonis, 1986). The additional possibility of lateral aggregation of the molecules would lead to a much more complex three-dimensional structure. 

Animal proteins, such as milk casein, whey, albumin, collagen, gelatin, keratin, and myofibrillar, are also proposed as raw materials to form edible films (13-15). Extended stmctures formed by unfolding of protein molecules are required for film formation. Amorphous three-dimensional stmctures formed by noncovalent interactions among protein chains stabilize the films. At high water content, films are produced by casting of viscous solutions, and at low water content, films are produced by extmsion using thermoplastic properties of proteins (13). 

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