Biosynthesis protein-based polymer

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... 

Biosynthesis of protein-based polymers, however, allows for production of protein-based polymers at cost levels that open a panorama of applications. Nonetheless, if it were not for the chemical syntheses, the design principles for any but the more mundane applications would not yet be in hand. In moving these advanced biomaterials toward the future, bioproduction becomes key. Nevertheless for... 

E.5.1 An Enabling Triumvirate Knowledge of Vital Forces, Capacity for Biosynthesis, and Elastic Protein-based Polymers with Unique Biocompatibility... 

Ferrari, F.A. and Cappello, J. (1997) Biosynthesis of Protein Polymers in Protein-Based Materials, Biorkauser, Boston. 

In one of the early experiments designed to elucidate the genetic code, Marshall Nirenberg of the U.S. National Institutes of Health (Nobel Prize in physiology or medicine, 1968) prepared a synthetic mRNA in which all the bases were uracil. He added this poly(U) to a cell-free system containing all the necessary materials for protein biosynthesis. A polymer of a single amino acid was obtained. What amino acid was polymerized ... 

Protein polymers based on Lys-25 were prepared by recombinant DNA (rDNA) technology and bacterial protein expression. The main advantage of this approach is the ability to directly produce high molecular weight polypeptides of exact amino acid sequence with high fidelity as required for this investigation. In contrast to conventional polymer synthesis, protein biosynthesis proceeds with near-absolute control of macromolecular architecture, i.e., size, composition, sequence, topology, and stereochemistry. Biosynthetic polyfa-amino acids) can be considered as model uniform polymers and may possess unique structures and, hence, materials properties, as a consequence of their sequence specificity [11]. Protein biosynthesis affords an opportunity to completely specify the primary structure of the polypeptide repeat and analyze the effect of sequence and structural uniformity on the properties of the protein network. 

Nucleic acids are polymers of nucleotides ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Although nucleic acids do not survive for geological periods in sediments (the maximum appears to be c.50kyr under favourable conditions) they are very important they control the self-replication of organisms (and hence provide information on evolutionary relationships) and act as the templates for protein biosynthesis. There are four nitrogen-containing bases... 

Non-natural amino acids can be incorporated into peptides and polypeptides via several different methodologies. Solid-phase peptide synthesis (SPPS) is a straightforward method for incorporation of non-natural amino acids and allows the incorporation of essentially any amino acid but is limited by the size of the peptides produced 18). Suppression-based strategies, both in vitro and in vivo, have been developed for site specific incorporation of diverse set non-natural amino acids into natural and synthetic polypeptides 19). Alternatively, auxotrophic expression hosts have been used for multisite incorporation of nonnatural amino acid in protein polymers, where multiple natural amino acids of one type can be replaced with non-natural analogues during protein biosynthesis (20, 21). Multisite incorporation of non-natural amino acids in the synthesis of protein polymeric materials facilitates chemical modification at multiple sites and can modulate the physical properties of the protein polymers (22). 

Other biopolymers useful for synthesis of nanocomposites include (i) gelatin—a water-soluble protein obtained by extracting collagen liom animal skin and bones and thermal denaturation. (ii) PHB—a natural product of biosynthesis performed by bacteria in nature, (iii) Chitosan—a natural polymer widely found in exoskeletons of crustaceans and insects, as well as in the cell walls of microorganisms (Maiti et al. 2003 Zheng et al. 2002 Takegawa et al. 2010). Moreover, the mechanical and water vapor barrier properties of chitosan-based nanocomposites with cellulose nanofibers could be enhanced. 

Nucleic acids Polymers made of phosphate-linked sugars bearing the heterocyclic bases adenine (A), guanine (G), cytosine (C), and thymine (T) in DNA or uracil (U) in RNA contain the genetic code for protein biosynthesis... 

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