Helix gelatin

In gelatin, when the triple helixes are heated in water, they open up. Some of the hydrolyzed ends fray out to tangle with other ropes,... 

Relationship between triple-helix content and mechanical properties of gelatin films. Biomaterials, 25, 5675—5680. 

The usual alkali employed is lime. The raw material for gelatine is tropocollagen, which is present in the original hides or bones. This protein consists of three polypeptide chains arranged in a triple helix. In contrast, gelatine consists of several free or interassociated chains, ranging in molecular weight from around ten thousand to several hundred thousand. On extraction, monomers (a-chains MW 100 000), dimers (P-chains) and trimers ( -chains) and some lower order peptides are released. 

When the collagen rod can be extracted in the native form it is soluble in acidic solutions, at room temperature. If the solutions are heated, the collagen is denaturated the chains lose their helical conformation. The characteristic temperature of this helix —> coil transition is around 36 C. The solution then contains principally single chains, but also some double and triple chains which were initially covalently bound and some sub-units of the single chains. This product is gelatin. 

Nature often uses cystine knots of variable complexity to assemble polypeptide chains in the correct order and to stabilize the structure of the resulting proteins. Classical examples are proteins of the extracellular matrix with collagens and gelatines as the main components. This simple cystine-knot approach has been applied to synthetic constructs to ligate in a desired order helix bundles. [166 170 194-1%] It has also been used to mimic natural multiple-chain containing proteins like collagen.[83 1691971... 

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