Spider Silk from Goats Milk?????

Matthew and I both work in the Lewis Lab where they are doing a project with spider silk. I only wash the dishes for the lab, but Matthew actually gets his hands dirty and works in the research and works with the goats. He has been able to help in the process of the birth of the baby goats. He has really enjoyed it. To make the story short they are making spider silk out of goats milk. But here is an article that I found on uwyo.edu that talks more about the project for all who are interested.



Untangling spider silk's structural mysteries
THE 6,000 LB OF GOAT MILK sitting in Randolph V. Lewis' laboratory freezer at the University of Wyoming takes up a lot of space. But it's only one part of the biochemistry professor's effort to understand spider silk and replicate its remarkable properties.
Of course, the caprine concoction is no ordinary goat milk. It comes from Montreal-based Nexia Biotechnologies, a company that made headlines a few years ago when it announced it had created genetically modified goats that produce milk laden with spider silk proteins. And understanding the chemistry and biophysics behind spider silk's remarkable properties has been at the heart of Lewis' research for nearly two decades (Chem. Rev. 2006, 106, 3762).
Courtesy of Randy Lewis
Polypeptide Zipper Antiparallel strands of helices made up of GGX repeats come together like a zipper.
To begin with, spiders don't make just one type of silk, Lewis noted. The ingenious arachnids produce silk in up to six varieties of varying strength and elasticity. Of these, Lewis said, dragline silk has attracted the most commercial interest.
Spun by orb-web-weaving spiders for their web's framework and for the spiders to catch themselves during a fall, dragline silk is about as strong as the bulletproof polymer Kevlar. Unlike Kevlar, however, dragline silk is also extremely elastic, which is why it takes 10 times more energy to break dragline silk than it does to break Kevlar.
Spider silk is made almost entirely of protein, so from a molecular standpoint, what is it that makes dragline silk so strong and also so elastic?
Thanks to fiber diffraction studies, scientists have long known that spider silk proteins possess crystalline regions of β-sheets. "The problem is that almost all the information we get is on those crystalline regions," Lewis explained. Although those β-sheets are important, they don't tell the whole story. The protein structure that gives spider silk its amazing elasticity is still something of a mystery.
Courtesy of Randy Lewis
Protein Nanospring Repeating β-turns take the shape of a springy β-spiral.
Because spider silk is insoluble in all but a few organic solvents, scientists can't use traditional protein characterization methods, such as X-ray crystallography and nuclear magnetic resonance spectroscopy, to suss out its structure. So Lewis' team decided to see what they could learn from examining the silk protein's amino acid sequence.
Lewis pointed out that one of dragline silk's proteins contains stretches of polyalanine of up to seven residues alternating with repeating sequences of three residues: two glycines (GG) and a third amino acid (X) that is either tyrosine, leucine, or glutamine.
On the basis of computer modeling, Lewis thinks this repeating GGX motif forms a helical arrangement in which each triplet makes a complete turn in the helix. In that structure, all the X residues extend outward from one side of the helix. The models also show that if two antiparallel strands of this helix come together, their X residues can interdigitate like a zipper. "We believe this is a key factor in terms of tensile strength," Lewis said.
The modeling studies have also led Lewis' group to propose that dragline silk's elasticity comes from a pentapeptide motif of glycine-proline-glycine (GPG) and two other amino acids (XX). This GPGXX sequence is thought to form a β-turn, and multiple β-turns from GPGXX take the shape of a springy β-spiral. "Looking at the structure," Lewis said, "you can imagine that if you pull, that spiral stretches."
Comparing the sequences of a variety of natural spider silks, Lewis noted that proteins lacking this GPGXX elastic segment can't be stretched beyond 5% of their original length. If a silk protein has nine of the elastic segments, however, its elasticity is 20 to 30%. And if the protein has 60 GPGXX repeats, its elasticity is more than 200%.
To test these computational models experimentally, Lewis' group, including postdoc Florence Teulé and undergraduate Alyssa Cooper, has made 18 different variations on the dragline silk protein. They tweak amino acids to see which factors are the most important in terms of strength and elasticity in spun fibers.