It's refreshing as a cold beer at lunch time to be posting again. I think I speak for all the ladies when I say I've been busy, yet these amazing women are outposting me ten to one! I miss the blog, and I must confess it feels less like a cocktail party and more like the bar I sneak away to on my lunch hour when I need to hide from responsibility for a bit. The problem is, my boss reads this blog, so he knows what I've been up to.
About once a week I get to investigate a subject that inspires me almost to the point of conversion. By that I mean I get so excited and interested in the topic that I consider leaving the writing world, going back to school to study science and living out my days doing research. It would be the science writing equivalent of getting married while drunk. Thank goodness I'm not more impulsive.
Anyway, this was one such topic. I was talking to some users at the Stanford Synchrotron Radiation Lightsource, which sees users from so many different disciplines that it's a constant source of amazing stories. Just last week they wrapped up scanning one of the Archaeopteryx fossils, which is an evolutionary link between lizards (maybe dinosaurs) and birds. Archaeopteryx was about as big as a chicken and had feathers, but also had a lizard like tail and teeth. Its body has traits of both birds and lizards, and it's known as one of Darwin's missing links: evolutionary connections between species. This is the first time these fossils have been scanned with this type of X-ray, and it will hopefully reveal some significant elemental trends, indicating what the flesh and feathers of the creature were composed of.
But I digress!
The users I was talking to were investigating a phenomenon that popped up a few years ago: scientists began to find traces of metal in the tips of spider fangs, crab claws, scorpion pincers and ant mandibles. You haven't seen spiders with shiny metal fangs - although who wouldn't want grills for their pet tarantula? - because these metals are only single atoms and are only present in the very tips of the appendages. These tips are what come into contact with the outside world, whether for fighting an enemy, killing prey or just walking, and the metal deposits seem to make the tips stronger and more fracture resistant. Furthermore, they may provide a new evolutionary link between these species.
Let me point out why these scientists were at SSRL. A synchrotron is like a microscope that looks all the way down to the atomic scale. They reveal things you could never see with your eye, but which ultimately provide far more interesting information. To quickly explain how they work, I'm going to steal a metaphor here created by a scientist at SSRL named Apurva Mehta. It's just too perfect to leave alone.
Imagine a truck carrying a full bed of tomatoes and traveling around a tight turn at 40 mph. Some of the tomatoes on the top of the truck will fly off, away from the truck. In a synchrotron, electrons are accelerated around a circular track, up to almost the speed of light, and as a result they emit powerful X-rays. The X-rays are like the tomatoes, flying straight off the curving beam of electrons. These X-rays are more powerful than the ones used to look at your bones. Synchrotron radiation can distinguish individual atoms, and even reveal the way they are bonded together.
Researchers can detect the metal deposits using other techniques such as Proton Induced X-Ray Emission and Scanning Transmission Ion Microscopy. Those techniques can reveal the location and identity of individual elements. A synchrotron can reveal the chemical environment. This refers to the presence of individual atoms (sometimes other techniques aren't sensitive enough to do this), the atoms' ionization states, and hints at the way the metal and non-metal pieces of the appendage are put together. It will take more work to see exactly how these structures are built, but that will be a fascinating breakthrough for engineers, who haven't seen anything quite like this anywhere else in nature.
The image up top (courtesy of Robert Schofield) is a synchrotron scan of the fang of a garden spider. 2 by 2 microns, it reveals that different metals settle in different areas: zinc is often found in the tips of spider fangs while manganese is found in the trunk. The upper right frame shows traces of zinc; the lower left shows manganese; and lower right combines these images - zinc is green and manganese is red.
An economist article from last July reports on zinc deposits found in the jaws of rag worms. These little things look squishy enough but beware when handling. They have curved fangs that serve as jaws, which they use to kill and eat crustaceans. The article begins by saying that it might not be common to look to nature when seeking new building materials, but I beg to differ. Nature is often a model of efficiency and innovation. As the article points out, spider silk is stronger than steel. There are many more instances and subtle ways that nature inspires engineering.
Understanding how these structures are build, and how it is that individual metal atoms can change material properties, might yield uses for humans. Fracture-resistant materials are usually soft and bend or deform under pressure, but the structures in these organisms are hard as well as fracture resistant.
"I don't think that these materials are record holders in any particular category - for example, diamonds will certainly be harder," says researcher Robert Schofield. "It is the mix or properties that is important. It may be that mimicking these materials will lead to man-made materials with an optimum balance of properties for certain small-scale tasks."
On a side note, I never thought about spiders going through puberty, but these metal deposits actually show up as the little guys move into adulthood and begin to molt for the first time. Another question is by what channels they travel through the spider's fangs to end up at the tips and what body changes trigger this.
The scientists, Robert M. S. Schofield of the University of Oregon, Micheal H. Nesson of Oregon State University and Robert A. Scott of the University of Georgia, are not only looking at structure, but are currently performing an evolutionary survey. They're trying to find as many animals as they can that show this trend. So far, the deposits have been found in 136 species of insects, 30 species of arachnids, 12 species of polychaete worms, and four species of centipedes. And there are still thousands of species to examine. Ultimately, researchers hope that understanding this biological pattern will guide the search for a common ancestor. It's fascinating that along with larger physical traits such as tails and teeth, or genetic traits like adapting to dairy products, biomaterials are also a primary marker on the evolutionary road map. Biomaterials can open the door for organisms to develop drastically new characteristics, a powerful edge in the survival game and even lead to the extinction or evolution of a species.
what a load of tosh. next time I suggest you just go for that beer and leave your laptop at home.
Posted by: physics groupie | December 19, 2008 at 09:52 AM
That's pretty interesting. I wonder if the electrical properties of the deposits are connected to some "sensing" that the spider performs.
Posted by: Chris | December 19, 2008 at 01:03 PM
Ah spiders and arachnids, a topic always so dear. The fangs are impressively engineered and apperently metal encrusted like pretty goth jewelry but the venom is the real show stopper. A dazzling array of new to science neurotoxins have been discovered in many spiders of late. The secret to this work has been a Buck Roger's like science instrument called a matric assisted time of flight mass spectrometer or MALDI for short. The Maldi mass spec can resolve mass down to a couple of daltons using a laser to desorb the sample from the matric it was spotted on. This technique has blown open the spider venom's secrets because spiders don't make much venom and the total volume available from your smallish not particulary deadly to man spider is barely visible to the naked eye. But if you are their prey, watch out, as that potent brew of lipopolyamines will render you paralyzed as quickly as any cocktail available at this cocktail party bar. So the next time you see a strange looking girl or guy in your garden crawling around on all fours in a lab coat with glass vials in hand, don't assume they are looking for a missing contact lens, it could be another spider story in the making.
Posted by: David | January 07, 2009 at 07:11 PM