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Golden Silk

We stopped in at the American Museum of Natural History in New York over the weekend to see the one-of-a-kind tapestry woven in Madagascar from the silk of Nephila madagascariensis, one of the golden orb weavers. Weaving was a highly developed art in Madagascar through the middle of the 20th century, and Europeans marveled at Malagasy creations in raffia, silk, and cotton, but especially silk. Malagasy royalty gave silk textiles to foreign leaders as they tried to establish or cement strategic alliances.

But that was silkworm silk. Weaving textiles from spider silk has never been practical, even in Madagascar, where giant golden orb weavers abound. When the tapestry was unveiled last autumn, The New York Times explained how Simon Peers, who has partnered with Malagasy weavers over the last two decades to revive their traditional art, put into play a plan to create the world's largest--and certainly most beautiful--piece of spider silk cloth. And the AMNH made a film, which you can see here. But if you can, get to the AMNH yourself to see this almost incredible piece of work. I dare you to keep your fingers off the case--they'll want to reach in and feel those wandering fringes where the silk looks still untamed.  Read More 
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Silk: From Liquid to Solid

A group of scientists in Norway and Sweden reported in the journal Nature last month that they've figured out something new about how spider silk self-assembles. Spider silk, which is a protein, starts out as liquid dope in spiders' silk glands. A protein molecule is a chain of amino acid molecules. As the amino acids up and down the chain interlock with each other in characteristic patterns, the liquid dope transforms into fibers.

The timing of this self-assembly is crucial. If it happened too soon, a spider would be left with balls of silk fiber clogging up its silk glands--useless. Why do the same molecules form a liquid in the glands but form fibers as they emerge from the spinnerets?

Like all proteins, silk protein molecules have two ends and a middle. One end is known as the C-terminus. The middle of silk protein molecules is made up of repeating sequences of amino acids that interlock to form the fiber. And the other end is known as the N-terminus. Silk scientists have known for a while that the C-terminus plays an important role in ensuring correct fiber self-assembly. The new report indicates that the N-terminus determines the timing of self-assembly.

As silk molecules move through the ducts leading from silk glands to spinnerets, they encounter gradually decreasing pH levels--that is, their surroundings become more acidic. The molecular structure of the N-terminus makes it sensitive to such a change, and it in turns influences how the middle, repeating segment of the silk molecule twists back and forth on itself. The researchers found that the N-terminus actually inhibits fiber formation in basic or neutral environments and hastens it at the levels of acidity found out in the spinnerets. So spider silk fibers self-assemble right on time.

One more example of how spider silk proteins may help us understand all sorts of other proteins. Read More 
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