spider silk proteins, microfluidics, and cool stuff that is small

A pair of German groups collaborated to produce an artificial spinarette. They made very small tubes (called Microfluidics by those in the business) into which they injected engineered spider silk proteins produced in bacteria. The obvious cool tings aside (e.g. arachnoweave armor) there are several interesting scientific oddities. The first is in the aggregation of protein eADF3. According to the article, at low concentrations it forms aggregates. But if you add shear flow (like forcing it through a small channel or a spinarette) it makes fibers instead of particles. That’s pretty strange.
Here’s something else. The protein aggregates in salt water under static conditions into tiny particles. These particles unfold and dissolve in pure water. The the fibers made of the same stuff in the same conditions stable in pure water. Something pretty drastic has changed about how those proteins are structured when they assemble under the shear conditions in the flow of that microfluidically confined stream. Indeed, spectroscopy shows a high beta-sheet content of the fibers, although I didn’t see anything about the beta-sheet content of the particles.
But these authors go one step further. A two part mixture of two silk proteins, both found in spiders (the above mentioned eADF3 and another, eADF4) produce a twisted fiber of higher strength and similarity to the natural product of a spider. If you’ve ever watched a nature show and seen a spider at work, you’ll know that they have to pull the silk tightly when they are spinning in order to make it strong; this explains why. The shear forces of the fluid moving through the spider’s little orifice are really important. Maybe that’s another step toward that arachnoweave armor. That and that d3o stuff (like a d3o Hat to protect your head) would make a product fit for Batman.

It’s not recombinant spider silk, but the D3O videos are worth looking at, if you have not already.