The Science Behind Silk
Today, traveling 6,000 miles by airplane could take 15 to 18 hours. A few thousand years
ago, making a journey of that same distance overland could take longer than a year to complete.
The Silk Road, stretching from China to the Mediterranean, was a key aspect of the early global economy, connecting the East and West and facilitating the trade of valuable goods for centuries.
Silk, the route’s namesake, was one of the most highly sought-after goods. (Kurin 2002)
Silk is an ancient material produced by silkworms and spiders for webs and cocoons
(Andersson et al. 2016). Being an animal fiber, silk is composed of protein – primarily the amino acids glycine, serine, and alanine (Zafar, Samadani 2014). Silk is organized in pleated sheets of protein chains with R groups extending from each bend. These crinkled structures can be closely packed against each other (Couteur, Burreson 2004).
The pleated sheet assembly of the molecules in silk keeps it from stretching and the tight
arrangement of the similarly sized layers accounts for silk’s even surface. The uniformity within silk’s structure is what makes the fiber’s ‘shininess’ possible, as the material’s even exterior is smooth and well-suited for reflecting light. (Couteur, Burreson 2004).
While the pleated protein sheets are mostly uniform, there are some small imperfections.
Irregularities in the chains mean that light can be broken up and reflected from the silk (creating a sparkly look). Furthermore, the small percentage of silk’s structure that is not made up of G, S, and A consists of other amino acids, a few of which have a strong ability to absorb dyes. These traits are part of the reason why silk was desirable thousands of years ago and still is today. (Couteur, Burreson 2004).
The unique chemical properties of silk have not only made it a valued commodity for its
feel and appearance in the fashion and design industries, but also for its toughness and versatility within STEM areas. Efforts to create synthetic silk resulted in the creation of the ‘artificial silks’ rayon and nylon. Silk’s biodegradability and non-immunogenicity make it especially useful in engineering and biomedical fields. (Ebrahimi 2015).
Silk played an important role in connecting different parts of the world and expanding
cultural reach in the early and Middle Ages through trade. Over the course of centuries, the one-of-a-kind material has fueled economic growth, inspired the synthesis of similar materials, and blossomed into a worldwide industry that is still growing today.
1) True or False: The characteristic shine, sparkle, and smoothness of silk can be attributed to its unique chemical composition and structure. (Answer - True)
2) Which is not one of the 3 primary amino acids found in silk?
1) Kurin, R “The Silk Road: Connecting People and Cultures” Smithsonian 2002.
2) ‘Napoleon’s Buttons’ by Jay Burreson and Penny Le Couteur, 2004.
3) Zafar, M. and Samadani, K “Potential use of natural silk for bio-dental applications”
Journal of Taibah University Medical Sciences 2014.
4) Andersson, M. et al. “Silk Spinning in Silkworms and Spiders” International Journal of
Molecular Sciences 2016.
5) Ebrahimi, D. et al. “Silk−Its Mysteries, How It Is Made, and How It Is Used” ACS
Biomaterials Science & Engineering 2015.