Silk fibers is formed from the Bombyx mori silkworm with triangular cross section with rounded corners of 5-10 μm wide. The fibroin-heavy chain is composed mostly of beta-sheets with flat surfaces of the fibrils reflect light at many angles to give natural shining appearance to silk. The cross-section from other silkworms may vary in shape and diameter and silkworm fibers are naturally extruded from two silkworm glands as a pair of primary filaments (brin) which are stuck together, with sericin proteins that act like glue to form a bave. Bave diameters for silk can reach up to 65 μm. Silk is one of the strongest natural fibers with good moisture of 11%. Its elasticity is excellent and it is microbial resistant too. However, It can be weakened if exposed to larger exposure of direct sunlight. Silk is a poor conductor of electricity and thus susceptible to static cling. Unwashed silk chiffon may shrink up to 8% due to a relaxation of the fiber macrostructur and occasionally, this shrinkage can be reversed by a gentle steaming with a pressing. Natural and synthetic silk is known to manifest piezoelectric properties in proteins, probably due to its molecular structure.

The construction of silk is called sericulture. The major silk producers are China (54%) and India (14%). Silk consists of two main proteins, sericin and fibroin. Fibroin is structural center of the silk, and serecin surrounds this core as sticky material. Fibroin is made up of the amino acids: Gly-Ser-Gly-Ala-Gly-Ala and forms beta pleated sheets. The high proportion (50%) of glycine is responsible for tight packing which makes the fibers are strong and resistant to breaking. The tensile strength is due to the many interceded hydrogen bonds and when stretched the force is applied to these numerous bonds and they do not break. Silk is resistant to most mineral acids, except for sulfuric acid, which dissolves it. It is yellowed by perspiration. Its low conductivity keeps warm air close to the skin during cold weather as well. It is often used for clothing such as shirts, ties, blouses, formal dresses, high fashion clothes, lingerie, pyjamas, robes, dress suits, sun dresses and Eastern folk costumes. Silk's attractive lustre and drape makes it suitable for many furnishing applications such as for upholstery, wall coverings, window treatments. A special manufacturing process removes the outer irritant sericin coating of the silk, which makes it suitable as non-absorbable surgical sutures.

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*Corresponding author:
Dr. Kirti Rani Sharma,
Assistant Professor (II),
Amity Institute of Biotechnology,
Amity University Uttar Pradesh, Noida
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