Yes folks, it’s the post you’ve been waiting for at long last! Spider-man was my first inspiration for making this blog because he’s such an obvious model for biomimetics. I had heard long ago that scientists were trying to harness the strength of spider silk for commercial production of bullet proof vests and other materials, and even longer before that everyone who read Marvel comics knew Peter Parker had already achieved that feat. Those of you more familiar with the Tobey Maguire/Sam Raimi Spider-Man franchise (2002-2007) might be questioning my choice of phrase. “But he was just a genetic mutant that created spider silk through a freak accident, he didn’t engineer anything!” In the original comic story, and recreated in the 2012 movie The Amazing Spider-Man, Peter Parker designs and manufactures his own synthetic web shooters. He IS a physics prodigy after all, he might as well put that genius to work! My first forays into researching spider silk on the web (all puns intended) taught me that this product is FAR more complicated than I had first imagined. First I thought, “Why not just domesticate spiders for mass silk production? That makes sense.” When humans decided we liked meat and milk, we fattened up a bunch of docile cows and concentrated them in a small area. This is how we get natural silk now from silkworms, the only domesticated insect. So let’s grab a bunch of spiders, put them in a room with enough insects to keep them happily fed, then sit back and reel in the silk. Well that’s not going to work out. Spiders are territorial and aggressive first of all, and secondly there’s a reason humans almost never domesticate carnivorous animals. It takes too much effort on its own to feed them, and when they get hungry they can eat each other! There have been examples of people harvesting enough silk straight from spiders to make some beautiful clothing, but it takes impractical amounts of time, money, and patience. For instance, this cape was made entirely from golden orb weaver spider silk (which is naturally golden, nothing was dyed). It’s just one cape, that can’t take too long to make, right? WRONG. A whopping eight years and 1.2 million spiders were invested into this one exquisite item of clothing. [new approach needed] In the last few decades we have a new tool available to us to combine desirable attributes of different organisms: splicing genes! Spider silk is just made of protein, so the instructions are directly coded into the DNA. This should be an easy solution to our farming problem, cut and paste the dragline silk gene into something docile like a bacterium, goat, or silkworm. What could possibly go wrong? Yes spider silk is composed of just protein, but it’s one really big protein. So big that the other organisms we’ve engineered can’t express the full protein before giving up. Part of the problem is that the spider silk gene is composed of a lot of repeated amino acid sequences, like having dozens of glycines in a row. Spider cells are prepared for this repetition, but other cells run out of the required tRNAs, truncating translation prematurely. We’ve made progress over the decades, but we haven’t quite gotten a domesticated animal to fully produce the desired quality and quantity of silk. There’s also an informativeTED Talk about spider silk that covers the different varieties of silk and some of the problems we’ve run into with genetic engineering. We already have some good substitute composites for spider silk, namely nylon and Kevlar. These materials have great resilience and strength, but the problem comes from the harsh chemicals and solvents needed for their production. The hope is that spider silk will inspire us to find a more natural, environmentally-friendly production method. So why do we keep trying to nail down this slippery substance? Because it’s still one of the coolest materials out there! To demonstrate, remember this scene from Spider-Man 2? Some very cool scientists went ahead and calculated if this would be possible using spider silk attached to a human-sized spool of silk. It would take 300,000N of force, and Darwin’s bark spider produces dragline silk with such a capacity for stopping trains.
Clearly, comic-based science is a growing field. Can we set up a conference for this? Reference: Chung, H., Kim, T. Y., & Lee, S. Y. (2012). Recent advances in production of recombinant spider silk proteins. Current Opinion in Biotechnology, (0). Elsevier Ltd.
0 Comments
|
Alanna DurkinExploring the realm of biologically inspired design one superhero example at a time, with some other natural sciences mixed in. Archives
September 2016
Categories
All
|