Background

Biochemistry of Silk

The mechanical properties of spider silk are a result of its primary amino acid sequence. Although the amino acid sequences for various types of spider silk are well documented, it is still relatively unknown how these amino acids aggregate and contribute to the strength and stability of silk. Silk proteins are composed of repeats of short amino acid sequences (approximately 33 amino acids). These repeats can be referred to as monomers. Each monomer consists of a glycine rich stretch, followed by an alanine rich stretch. It is hypothesized that these hydrophobic alanines form beta sheet crystals with other silk proteins, and contribute to the strength of the silk fibers. The glycine stretches are thought to form alpha helices and contribute to the flexibility of the protein. This monomer sequence is repeated many times in one protein, and allow for strong interactions with other silk proteins. These simple motifs repeated over and over are the key to the formation of one of the strongest materials known to man.

Applications

Silk is a naturally strong and flexible material, and so it is a unique fiber that can be used in applications that require the normally contradicting qualities of tremendous strength and low weight. It could be woven into thick cables for heavy industrial use or into fabrics for ballistic protection. Silk not only has amazing properties in its strength and elasticity, it is a highly versatile material that can exist in many different forms. For example, its ability to exist as a hydrogel combined with its natural biocompatibility and controlled rate of biodegradation make it a good material for use as an in vivo tissue scaffold. Silk scaffolds could also exist as mesh woven from fibers and used for skin grafts and bandages.