Protein-based materials produced

From the latter comes the fated promise to replace the finite petroleum reserves and to prepare products in an environmentally Mendly manner to sustain an increasingly complex society. It is now possible, by genetic engineering, to produce proteins that evolution has never called upon nature to prepare and to produce protein-based materials for addressing primary problems required for sustaining our society. 

Protein-based polymers have the potential to surpass the polyesters and other polymers because they can be directly produced in microorganisms and plants by recombinant DNA technology resulting in the capacity for diverse and precisely controlled composition and sequence. This is not possible with any other polymer, and it increases range of properties and the numbers of applications. Remarkably, with the proper design of composition, protein-based materials can be thermoplastics, melting at temperatures as much as 100°C below their decomposition temperatures. Therefore, they can be molded, extruded, or drawn into shapes as desired. Aspects of protein-based materials as plastics is also considered below. 

As introduced in Chapter 1, the present chapter constitutes Assertion 4 The Applications Assertion of the book. Production and purification are first addressed, as they obviously make up the initial enabling steps in moving toward applications of any materials. The most surefooted path toward materials applications of protein-based polymers, however, intertwines issues of production and purification through a combination of the two methods of preparation—chemical synthesis and biosynthesis. Chemical synthesis proved the biocompatibility of elastic protein-based polymers and therefore opened the door to medical applications. Demonstration of the biocompatibility of the chemically synthesized product made clear the purification required of elastic protein-based polymers produced by E. coli if unlimited medical applications were to be possible. Chemical synthesis also provided a faster route to diverse polymer compositions, which allowed... 

The properties and physico-chemical characteristics of proteins in an aqueous solvent system depend on the pH conditions. Many protein-based materials are sensitive to pH variations, which could be linked with the relatively high proportion of ionised polar amino acids in protein raw materials (Table 11.7). Zein and keratin materials can, for example, be produced within a broad pH range because these proteins (which have a low ionised polar amino acid content, 10% and 10.7%, respectively), are not very sensitive to pH variations [69]. Conversely, the high content of ionised polar amino acids in soy proteins (25.4%) limits film-forming applications to within a narrow pH range [148]. 

One frozen dessert is made with Simplesse, a protein-based fat mimetic that contains no fat (37). Other dairy product developments include a fat flavor, produced by encapsulating milk fatty acids in maltodextrins (38) fat-free cottage cheeses and 2% fat milk, prepared by steam stripping cream with partial fat addback, with a cholesterol level about 60% lower than the starting material (39). 

In order to reduce the time required to confirm the accumulation of a given recombinant protein, we have developed a cell culture system in which transgenic alfalfa callus material produced at the proliferation step of Agrobacterium-based transformation is used to initiate cell cultures. These cell suspensions can be subcultured to sustain batch production of modest protein amounts. The protein blot shown in Fig. 1.2 demonstrates our ability to detect a recombinant protein in total... 

Table 1.2 Some pharmaceuticals that were traditionally obtained by direct extraction from biological source material. Many of the protein-based pharmaceuticals mentioned are now also produced by genetic engineering...

Despite the undoubted advantages of recombinant production, it remains the case that many protein-based products extracted directly from native source material remain on the market. In certain circumstances, direct extraction of native source material can prove equally/more attractive than recombinant production. This may be for an economic reason if, for example, the protein is produced in very large quantities by the native source and is easy to extract/purify, e.g. human serum albumin (HSA Chapter 12). Also, some blood factor preparations purified from donor blood actually contain several different blood factors and, hence, can be used to treat several haemophilia patient types. Recombinant blood factor preparations, on the other hand, contain but a single blood factor and, hence, can be used to treat only one haemophilia type (Chapter 12). 

Figure 1.1 The structure of DNA is illustrated here. DNA is the genetic material of the cell. Through the processes of transcription and translation, the DNA sequence is used to produce first an RNA copy of the gene and then a protein based on the gene sequence.

Although the amino acid sequence as well as the secondary structure of fibroin differs from those of spidroin, the fibers spun from these proteins, that is, silkworm silk and spider silk have comparable mechanical properties. These may be attributed to the structural characteristics, both at the molecular and filament level. The superior mechanical properties of silk-based materials, such as films, coatings, scaffolds, and fibers produced using reconstituted or recombinant silk proteins, are determined by their condensed structures. 

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