Friday, February 15, 2013

Spider-Man Science: Stronger Than Steel by Bridget Heos

In the Spider-Man movies, Peter Parker is able to swing from buildings, catch a falling car, and stop a speeding train--all with spider silk 
....The strength of spider silk is not exaggerated in the movies. If anything, spider silk is even stronger. In real life, Peter Parker would stop a 747 airplane with a rope of spider silk just one inch in diameter.

Finer than a hair, incredibly strong, and very flexible--spider silk is the dream material to replace steel bridge cables, titanium or alumninum aircraft skins, or Kevlar protective vests. But how to obtain mass quantities of this material and shape it into what we want it to be is a real scientific challenge.

But in the past two decades the science of bioengineering has arrived at the stage where people can begin to implement their knowledge of genomes, gene manipulation, and animal cloning to procure and use those proteins which give spider silk its phenomenal properties.

Scientists in the field began with the golden orb spider, specifically its dragline silk (used to support and anchor this spider's huge, elaborate webs),  for the task. Unlike that other critter venerated for its fine silk, the silkworm, spiders can't exactly be farmed, because they have the unfortunate tendency to, er, eat each other! So spider farms are definitely out.

The real-life spider-man, Dr. Randy Lewis, and his team saw another way to go. From the golden orb spider, they painstakingly extracted the genes responsible for dragline silk production. These genes were introduced into embryonic goats, some of whom were born both transgenic and female, capable of producing silk protein in their milk. The experiments took time and much careful work, but small quantities of that protein were extracted which could be extruded into strands just like any other man-made fiber.

If enough transgenic goats can be bred to become good milkers, could this source of spider silk's key protein be used in regular manufacturing processes to make that something that would make Peter Parker envious? Scientists are still perfecting their spider-goat milk production and have since branched out into introducing the spider silk gene into silkworms and even alfalfa plants. They already envisage many important products--incredibly thin surgical sutures, lightweight space suits, even aircraft carrier deck cables for Navy fighters' tailhooks--that would benefit from the remarkable tensile strength of spider silk.

Some of the scientists even have a less dramatic plan for the first spider silk product:

It's something that would have interested Randy's fisherman father: a fly tipper. That's the fiber that ties the hook to the fishing line. Spider silk would be stronger but thinner than the fibers currently on the market. The fish would be less likely to see it, bite through it, or break it!

The latest in the notable Scientists in the Field series, Bridget Heos' forthcoming Stronger Than Steel: Spider Silk DNA and the Quest for Better Bulletproof Vests, Sutures, and Parachute Rope (Scientists in the Field Series) (Houghton Mifflin, 2013) doesn't go into deep into caves, slog through swamps, or down beneath the ocean. This field work takes place instead in various cooperating disciplines, from the biology lab to animal husbandry and agronomy to high-tech experiments in manufacturing, all in field research that is every bit as on the edge as any jungle biologist or deep ocean submarine. Instead of daring feats of crook catching, these modern spider-men (and women) dream of results which could make a dramatic difference in human safety and security.

With candid snapshots of orb spiders, even one on a trusting boy's cheek, appealing baby goats, transgenic glow-in-the-dark fish, and silk worms with just a touch of spider genes, this addition to the series takes young science students into new and promising areas of human exploration. Equipped with a first-rate glossary, additional source list, print or web-based, and a complete index, this one has the goods for students producing research reports.

Publishers Weekly gives this significant nonfiction book a starred review, saying, "Move over, Spider-Man. . . . Abundant photographs and a lively narrative make the topic accessible and almost lighthearted, and Heos lays groundwork for readers with a basic introduction to DNA and gene theory."

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