Monomers protein-based polymer

Precise control of the sequence of amino acid residues Any protein-based polymer sequence utilizing the 20 naturally occurring monomers can be specified using recombinant DNA technology. This allows for equivalent ease of production of diverse protein-based polymer sequences, many of which would otherwise be quite difficult or essentially impossible to prepare due to problems of chemical synthesis and unfavorable energetics in the final polymer. 

Figure 9.1. Diagram showing the approach whereby recombinant DNA technology was used to construct monomer and multi-mer genes for expression of the elastic protein-based polymer [(GVGVP)io]n(GVGVP). (Reproduced with permission from Woods. )...

Having verified that the repeating sequence of the expressed protein agrees with the sequenced monomer gene, it is now to be determined how many repeating units constitute the expressed protein-based polymer, that is, the... 

The polymers discussed up until now have all been made synthetically, however, polymers also occur naturally and are produced by microorganisms, plants and animals. Polymers that are produced by living organisms are called biopolymers. The monomers in this case can be materials such as sugars, amino acids and nucleic acids and by polymerisation can produce starch based polymers or protein based polymers. We have biopolymers inside us all - nucleic acid which produces our own DNA is a biopolymer. 

Synthetic protein-like polymers containing amino acids find pharmaceutical and biological applications and display self-assembly properties [174], In this aspect, both ROMP and ADMET have been used as tools for the polymerization of amino acid-based monomers. Early ROMP examples date back to 1994 with the synthesis and ROMP of amino acid-derived homochiral norbomene monomers by Coles et al [175], The molybdenum complex [Mo(=CHCMe2Ph)(=NC6H3Pr,2-2,6)(OBu )2]... 

Besides addition polymerization, the other general way to prepare polymers is known as condensation polymerization or step growth polymerization. Much of the pioneering work on condensation polymerization was conducted by Wallace Carothers while he was employed by DuPont. He recognized that many natural polymers are formed from monomers with two reactive functional groups. For example, proteins are polymers of amino acids, which contain both amine and carboxylic acid groups. The formation of amide bonds is used to connect one monomer to another. Carothers s attempts to imitate nature led to a whole industry based on condensation polymerization. 

The repair and replication of cells involves metabolism - interconversions of hundreds of low molecular weight metabolites that ultimately yield the precursors for much larger, more complex macromolecules such as phospholipids (based on phosphatidic. acids or long chain fatty acid esters of glycerol phosphate), polynucleotides such as RNA and DNA (polymers of nucleotide monomers), proteins (polypeptides or amino acid monomers linked by peptide bonds) and polysaccharides (polymers of simple sugars or monosaccharides). 

All strategies for the production of genetically engineered polymers rely on the basic principle of self-figation (concata-merization) of DNA monomers to form concatameric DNA sequences (3,4). These concatamers are then cloned into the appropriate plasmid and introduced into a biological expression system, where they are transcribed and translated by the ceUrdar machinery to produce a protein-based pol3nner. 

The book addresses the most important biopolymer classes like polysaccharides, lignin, proteins and polyhydroxyalkanoates as raw materials for bio-based plastics, as well as materials derived from bio-based monomers like lipids, poly(lactic acid), polyesters, polyamides and polyolefines. Additional chapters on general topics - the market and availability of renewable raw materials, the importance of bio-based content and the issue of biodegradability - will provide important information related to all bio-based polymer classes. 

PEO Is a non-toxic water-soluble polymer which is extensively used for biomedical applications. PEO resists the adsorption of plasma proteins because of their strong hydrophlllcity, chain mobility, and lack of ionic charge [30]. The PEO immobilization on any polymer surface would result in the decrease in the protein adsorption and platelet adhesion. This versatile nature of PEO has led to many studies not only on the preparation of PEO derived surfaces but also on the subsequent uses of these surfaces as biomaterials [31-34]. The PEO layer if adhered on the normal material surface may be washed off because of the absence of any interaction between the two surfaces. Therefore, covalent immobilization of PEO has been carried out either by grafting PEO molecule on a base polymer or by grafting a monomer bearing pendant PEO groups. 

The non-biodegradable and non-renewable nature of plastic packaging has led to a renewed interest in packaging materials based on biopolymers derived from renewable sources. Such biopolymers include naturally occurring proteins, cellulose, starches, and other polysaccharides and those synthesized chemically from naturally derived monomers such as lactic acid. Commercialization of these bio-based polymers has already begun. Naturewoiks, LLC (Minnetonka, MN) manufactures polylactide from... 

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