Water-insoluble collagen

Thus, the relative ease of grafting monomers onto water-insoluble collagenous substrates using CAN as initiator decreases in the following order ... 

Gelatin is the most widespread water-soluble protein in the body, resulting from partial degradation of water-insoluble collagen. Gelatin has widely... 

Animal glue is the water-soluble product of the hydrolytic degradation of water-insoluble collagen fibers. The products of hydrolysis vary greatly in molecular weight (approx. 10,000 to over 250,000), and measurements of viscosity and gel strength are necessarily average. 

On a larger scale, we have ligaments and cartilage, structures that hold joints together and tie muscle to bone. These too are composed of proteins tough, water-insoluble proteins. Principal among them are the collagens. 

The very first research project Huzella gave me was to study the intercellular substance between plant cells with the latest histological techniques used in his laboratory. He and his associates were concentrating on the study of the substance between the cells in animal tissues. Their primary interest was collagen, the fibrous, water-insoluble protein that is the main building block of the intercellular substance or intercellular matrix, as we call it today. 

A better understanding of this subject is possible when the location and function of the pectic substances in plants are reviewed. The movement of water and plant fluids to the rapidly growing fruits and the retention of form and firmness of fruits are functions of pectin. This intercellular substance in plants is similar in action to the intercellular substance of the vertebrates—collagen (the precursor of gelatin). Protopectin, the water-insoluble precursor of pectin, is abundant in immature fruit tissues. Ripening processes involve hydrolytic changes of protopectin to form pectin and later, as maturity is passed, enzymic demethylation and depolymerization of pectin to form pectates and eventually soluble sugars and acids. 

Collagen, a component of bone and connective tissue, is the most abundant protein in vertebrates. It is organized in water-insoluble fibers of great strength. 

Animal glues are derived by the hydrolysis of the protein constituent collagen of animal hides and bones. Collagen in its natural state is water insoluble and must be conditioned to solubilize the protein. Collagen molecules are triple helices of amino acid sequences and contain both nonpolar and charged acidic and basic side chains. The conversion of... 

Proteins can be classified by the functions just discussed. They can also be classified into two major types, fibrous and globular, on the basis of their structural shape. Fibrous proteins are made up of long rod-shaped or stringlike molecules that can intertwine with one another and form strong fibers. They are water-insoluble and are usually found as major components of connective tissue, elastic tissue, hair, and skin. Examples are collagen, elastin, and keratin (see > Figure 9.4). 

Proteins generally fall into one of two main classes fibrous or globular. Fibrous proteins are animal structural materials and hence are water insoluble. They, in turn, fall into three general categories the keratins, which make up protective tissue, such as skin, hair, feathers, claws, and nails the collagens, which form connective tissue, such as cartilage, tendons, and blood vessels and the silks, such as the fibroin of spider webs and cocoons. 

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