Synthetic Fibers Made from Proteins

Synthetic Fibers Made from Proteins Harold P. Lundgren... 

The requirement of crystallinity can be met by other forms, e.g., the extended /3-configuration. Further, it is not necessary that the fiber be completely crystalline in order that this model be applicable. All that is required is partial crystallinity and preferential orientation of crystallites along the fiber axis. This requirement is met by numerous fibrous proteins and also by synthetic fibers made from globular proteins. 

The first really successful artificial material used in the manufacture of synthetic blood vessels was Dacron , a polyester fiber made from polyethylene terephthalate (PET). The material is woven or knitted into thin tubes with dimensions similar to those of a natural blood vessel. The tubes are then treated with coagulated blood or with albumin, an important blood protein, to block the tiny holes in the fabric of which they are made. Over time, cells migrate into the blood or albumin trapped within the Dacron matrix and deposit collagen. As the blood or albumin degrades, it is replaced by the collagen, producing a vessel with some properties similar to those of natural blood vessels. 

Pichia pastoris [79], and plants [80, 81]. A complete protocol for the artificial spinning of fibers made from recombinant proteins based on chimeric or native synthetic spider siLk-Uke sequences produced through genetic engineering in E. coli was described by Teule et al. in 2009 [82]. Two examples of the genetic engineering methods are outbned here. 

Mention has already been made of two polymers that can be obtained naturally from living animals silk (from the silkworm) and wool (from sheep). They are proteins made of various amino acids both are used in textiles. Other biologically derived polymers are also familiar such as wood, starch, and some sugars. We will not cover these in detail here. However, certain cellulosics we will discuss briefly since they are compared to synthetic fibers later. Cellulose is the primary substance of which the walls of vegetable cells are constructed and is largely composed of glucose residues. It may be obtained from wood or derived in very high purity from cotton fibers, which are about 92% pure cellulose. 

A term more general than polymer is that of macromolecule. Macromolecules are chemical compounds formed from at least one thousand atoms linked by covalent bonds. They are common as natural substances like cellulose, proteins, lignin, etc., and also as synthetic compounds including plastics, fibers, elastomers, coatings, and adhesives. Many synthetic and some natural macromolecules have repetitive structures and are known as polymers. For example, cellulose is made from p-D-glucose residues interconnected by p-glucoside (1->4) links, polystyrene is made from 1-phenylethylidene units, etc. 

For the purpose of discussion of the chemistry and technology of man-made, fiber-forming polymers, the term "synthetic fiber" will be used to denote all man-made fibers manufactured from noncellulosic raw materials. The term "cellulosics" will apply to those man-made fibers that are manufactured from cellulosic raw materials. The term "man-made fibers" will apply to all fibers except the naturally occurring cellulosic and protein fibers. 

Polymers can be classified in different ways. From the forensic perspective, a reasonable starting point is to divide pol)Tmers into biologically derived polymers (biopol3rmeis) and synthetic organic polymers. Biopolymers are extracted from natural sources such as plants or animals. Even though proteins and DNA are biopolymers of unquestioned importance in forensic science, their analysis resides in the context of forensic biology. The biopolymer we will concentrate on is cellulose, the base material in paper and cotton fibers. Historically and chemically, semisynthetic polymers fall between naturally derived and synthetic polymers. Rayon and cellophane are made from regenerated... 

HoUow fibers are widely used for filtration, utilizing the semipermeable nature of their capillary walls. In the medical industry, hollow fiber bioreactors are often made from cellulose and synthetic polymers. Cellulose acetate and cuprammonium rayon are the widely used ceUulose-based hollow fibers, while synthetic hollow fibers are often made from polysulfone, polyamide, and polyacrylonitrile. Modifications can be made to these materials to improve their functions by using polymers based on phospholipid, a substance found in the human cell membrane. 2-methaCTyloyloxyethyl phosphoryl-choline (MPC) is a methacrylate monomer with a phospholipid polar group. When MPC-based copolymers are used as additives for polysulfone, protein adsorption and platelet adhesion can be effectively reduced, thereby improving blood compatibility. Cellulose acetate hollow fiber membranes can also be modified with MPC-based copolymers by means of blending or surface coating to obtain improved permeability. 

Textile fibers are normally broken down into two main classes, natural and man-made fibers. All fibers which come from natural sources (animals, plants, etc.) and do not require fiber formation or reformation are classed as natural fibers. Natural fibers include the protein fibers such as wool and silk, the cellulose fibers such as cotton and linen, and the mineral fiber asbestos. Man-made fibers are fibers in which either the basic chemical units have been formed by chemical synthesis followed by fiber formation or the polymers from natural sources have been dissolved and regenerated after passage through a spinneret to form fibers. Those fibers made by chemical synthesis are often called synthetic fibers, while fibers regenerated from natural polymer sources are called regenerated fibers or natural polymer fibers. In other words, all synthetic fibers and regener-... 

Manufactured protein fibers, often called azlons, are man-made fibers produced from animal or plant proteins. Examples of protein sources are milk, chicken feathers, soy beans, peanuts, corns, etc. Traditionally, most manufactured protein fibers were made directly from proteins dissolved in solvents. Recent trends in the research and development of manufactured protein fibers include the use of biochemistry to modify the source proteins and the introduction of synthetic polymers such as polyvinyl alcohol and polyacrylonitrile to improve the fiber mechanical properties. Antibacterial agents are often being added during the fiber formation process to provide health benefits to the manufactured protein fibers. As a result, the chemical structure of manufactured protein fibers is becoming more complex. 

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