Chemical Modification of Proteins

Proteins have been utilized commercially from ancient times, either in their naturally occurring form or modified in some manner. Use of silk and wool fibers, for instance, goes back a very long time. Many animal glues, prepared from bones and hides of cattle or sheep, have also been around for a very long time. Today such glues are being replaced rapidly by synthetic materials. Those that are still    manufactured are usually formed by steaming the bones and the hides under pressure and then treating them with hot water in several cycles. This degrades the collagen and make is soluble. The aqueous solution is concentrated by vacuum evaporation of the water. The material that gels is dried and pulverized. Milder hydrolysis yields gelatin that is used commercially in foods. Casein, the milk protein (less readily available casein from vegetable sources is hardly ever used), is also used in adhesives. Here too, synthetics are gradually taking over. At one time it was used to produce a fiber and a plastic that was formed by cross-linking with formaldehyde. The cross-linking reaction was carried out by immersing the proteins in a formaldehyde solution (4–5%) at 55–65C for long periods of time, such as days and even months, depending upon the size of the article. The cross-linking reaction involved pendant amino groups and is quite similar to the reactions of urea- and melamine-formaldehyde resins (see Chap. 7). Some condensation and formation of methylene bridges may also involve amide nitrogens. It does not appear likely that casein fibers or plastics are still being produced anywhere. Extensive research work has gone into modification of proteins, not for commercial applications but for academic reasons. Thus, for instance, Frances et al. developed a new reaction that introduces single reactive ketones or aldehydes at the N-terminal groups of protein when the proteins are mixed with pyridoxal phosphate [44]. The researchers also developed a palladium-catalyzed allylic alkylation that attaches long lipid tails to proteins, a process that can be used to customize the solubility of enzymes, antibodies, viral capsids, and other proteins.

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مواضيع ذات صلة

Polyalkanoates

Synthetic Methods for the Preparation of Nucleic Acids

DNA and RNA

Nucleic Acids

Synthetic Methods for the Preparation of Polypeptides

Structures and Chemistry of Proteins

Proteins

Polyisoprene

Lignin

Derivatives of Cellulose

Regenerated Cellulose

Cellulose