Dating silk and other chiral activities

There’s an interesting article in the February issue of Smithsonian about a new process to date silk artifacts accurately. There’s a short article on the Smithsonian’s website summarizing the technique. Basically, the amino acids in silk come in two types. The silk starts out as all one type, but slowly over time turns into the other type. You can calculate the age of the item based on the ratio of these two types, and scientists at the Smithsonian have figured out how to do it with a much smaller sample, which means that silk artifacts in museums can be tested without destroying a large piece.

I thought it was fitting that this technique came back around to fibers and cloth, because it’s what inspired the name of my blog, and I don’t think I’ve ever explained it here. Chirality is a certain kind of symmetry in molecules, like the amino acids in silk. Most amino acids, the building blocks of proteins, are chiral, as well as sugars manufactured by the body, and in some pharmaceuticals. In fact, it’s fairly common in some classes of drugs that one version of the drug molecule is active in the body, and the other one doesn’t do anything at all, because the shape of the molecule has to fit the body’s receptor in order to work.

Chiral symmetry is seen when an object is not superimposable on its mirror image, and the most common examples of this in everyday life are human hands. If you look at your left and right hands, you can tell that they are similar, but they are not identical and you can’t lay one on top of the other and make them the same, no matter how you flip them.

I was a chemistry major, even though I don’t use my training much these days, so “Chiral Craft” is a result of my chem geek-dom and the fact that chirality is informally known as handedness, and I’m writing about sewing and other “handicrafts”. So now you know how much of a geek I am the story.


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