Synthetic silks silk structures

Asakura, T., Ohgo, K., Ishida, T., Taddei, P., Monti, P., and Kishore, R. (2005). Possible implications of serine and tyrosine residues and intermolecular interactions on the appearance of silk I structure of Bombyx mod silk fibroin-derived synthetic peptides High-resolution 13C cross-polarization/magic-angle spinning NMR study. Biomacromolecules 6, 468-474. 

Nylon was designed to be a synthetic silk, (a) The average molar mass of a batch of nylon 66 is 12,000 g/mol. How many monomer units are there in this sample (b) Which part of nylon s structure is similar to a polypeptide s structure (c) How many different tripeptides (made up of three amino acids) can be formed from the amino acids alanine (Ala), glycine (Gly), and serine (Ser), which account for most of the amino acids in silk ... 

As revealed by studies of silk, structural proteins include regular and random regions in the chain structure which would be expected to give rise to crystalline and amorphous material. In contrast, the amorphous component of synthetic polymers arises from entanglements of the coiled chains that cannot be resolved during the crystallization process. New polymer properties may be achievable once we can design polymer chains with such controlled sequences. 

It is usual to think that plastics are a relatively recent development but in fact, as part of the larger family called polymers, they are a basic ingredient of animal and plant life. Polymers are different from metals in the sense that their structure consists of very long chain-like molecules. Natural materials such as silk, shellac, bitumen, rubber and cellulose have this type of structure. However, it was not until the 19th century that attempts were made to develop a synthetic... 

In general, heterogeneities in structural materials are often the source of mechanical failure, but specific types also provide ways to disperse energy without failure. For example, some silks, at a microscopic and macroscopic level, are able to form structures such as spherulite inclusions that will develop into elongated cavities in the solid fibers (Akai, 1998 Frische et al., 1998 Robson, 1999 Tanaka et al., 2001). Interestingly, Isobe et al. (2000), in a significant but largely overlooked paper, showed that synthetic A/ i 4o produced spherulites that had the essential features of Alzheimer s amyloid senile plaques (Kaminsky et al., 2006). 

The structure of kermisic acid is l,3,4,5-tetrahydroxy-7-carboxy-8-mcrhylanthraquinone. Carminic acid (Cl Natural Red 4 Cl 75470). is a red dye occurring as a glycoside in the body of the cochineal insect Dactylopius coccus of the order Homoptera. family Coecidae, Until the advent of synthetic dyes, the principal use for carminic acid was for dyeing tin-mordanted wool or silk. Its aluminum lake, carmine, finds use in Lhe coloring of foods. The structural formula of carminic acid is (2). 

Synthetic polyamides have a structure similar to those of wool and silk but differ in having a low acid-binding power and in their capacity to dissolve nonpolar compounds. Consequently polyamide materials can be dyed with disperse dyes and with selected acid dyes, including metal-complex dyes [11]. 

In much the same way, natural polymeric fibers like wool, cotton, silk, etc., are often touted as superior to anything that is man-made or synthetic. But is this fair There is no doubt that natural fibers have a unique set of properties that have withstood the test of time (e.g., it is difficult, but not impossible, to match silk s feel or cotton s ability to breathe ). On the other hand, consider Lycra , a completely synthetic fiber produced by DuPont (Figure 1-12) that has a truly amazing set of properties and is the major component of Spandex (a material that keeps string bikinis on ). Or consider the wrinkle-free polyester fibers used in clothing and the stain proof nylon and polyacrylonitrile polymers used in carpets. The point here is that polymers, be they natural" or synthetic, are all macromolecules but with different chemical structures. The challenge is to design polymers that have specific properties that can benefit mankind. 

Our goal here is to have you compare and contrast some synthetic and natural polymers, such as nylon and silk, cotton and polyesters, so we will focus largely on biopolymers that are fibrous in nature and which are used as structural materials in plants and animals. We also aim to illuminate the way nature has married structure to function in such a marvelous fashion. Hopefully you will emerge... 

One can classify fibers in a variety of ways. For example, one may divide the whole field of fibers into apparel and nonapparel fibers, i.e. based upon the final use of fibrous material. The apparel fibers include synthetic fibers such as nylon, polyester, spandex, and natural fibers such as cotton, jute, sisal, ramie, silk, etc. Nonapparel fibers include aramid, polyethylene, steel, copper, carbon, glass, silicon carbide, and alumina. These nonapparel fibers are used for making cords and ropes, geotextiles, and structural applications such as fiber reinforcements... 

In man-made fibres, any stretching will irreversibly alter the crystallinity and there is no control of the lateral size of polymer crystals. Semicrystalline polymer networks typically consist of platelet type crystals whose width exceeds their thickness by several order of magnitudes because only the thickness is controlled by the chain folding [61]. In contrast to synthetic fibres, spider silk does not need any mechanical treatment by external forces the constituents self-assemble directly during the spinning-process. These examples clearly demonstrate the need for more detailed control of the mesoscopic structures for further development of man-made materials. 

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