Brilliant Whiteness of Strange Beetle Explained

Forget bleach: this bug may be the key to whiter whites

By JR Minkel

Image: COURTESY OF PETE VUKUSIC/EXETER UNIVERSITY WHITE AS A BEETLE: An unusually white beetle sports a bright color despite having extremely thin scales compared with other white materials. Your walls, clothes and teeth not white enough for you? Good news: scientists have identified the source of the dazzling whiteness of a beetle called Cyphochilus, and harnessing that knowledge could help make everything from paints to t-shirts more blindingly white. It turns out that the bug's scales contain a porous network of random protein fibers that scatter all wavelengths of light strongly, the prerequisite for an intense white color. The beetle might not stand out against the brilliant blue of a butterfly, but "in terms of sheer design ingenuity, for me this is my favorite," says optical physicist Pete Vukusic of Exeter University in England, who has studied the bright coloring of dragonflies and butterflies.

Vukusic knew he was on to something when he saw Cyphochilus on an insect collector's Web site. "Something this amazingly bright and white had to be coming from something very thin," meaning its thin coat of scales, he says. "That in itself is quite interesting. Any industry can make something very white that's thick." The more layers a material has, he says, the stronger it can scatter light and the brighter its color can be. In this week's Science Vukusic and his colleagues report that the bug's five-micrometer-thick scales were whiter than a child's baby tooth, which is encased in a millimeter-thick layer of white enamel. They used an international standard to assess the beetle's relative whiteness. Electron microscopy revealed the scales are made of a tangle of seemingly randomly oriented filaments, each about 250 nanometers wide. A random microscopic structure is key to producing a white color, which results when all wavelengths of light scatter equally from a surface. If the surface contains any repeating pattern, it will reflect light of the wavelengths that match that pattern.

Image: COURTESY OF PETE VUKUSIC/EXETER UNIVERSITY WHITE STANDS OUT: White coloring is unusual in nature because it requires a surface to reflect all wavelengths of light strongly. To confirm the randomness of the filaments, the researchers took a cross-section image of the filament network and performed a mathematical technique called a Fourier transform, which reveals any repetition in a shape. They also shined a laser beam through one of the scales and projected the resulting pattern onto a curved surface. Any repetition in the scale's internal structure would show up in the pattern of projected light. Neither technique turned up any signs of nonrandomness, the group reports. Vukusic says the brightness of the color results from gaps of air between the filaments. Light scatters every time it passes between two materials that differ greatly in the speed of light through them, also called their refractive index. Like facets in a diamond, the more places light can scatter, the brighter the ultimate color. "If you separate the scattering centers, but not by too much, then you actually improve the efficiency at which the whole light spectrum is scattered," Vukusic says. If manufacturers can learn how to harness this effect, he says, they might be able to whiten just about anything that's white.

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The Incredible, Medical Egg

Genetically modified chickens that produce medicines in their eggs may be the drug factories of the future

By David Biello

Image: COURTESY OF ROSLIN INSTITUTE CHICKEN OR THE EGG: A genetically modified rooster has produced a flock of hens that make medicines inside the whites of their eggs. The chicken egg has a storied history in medicine. Even today, millions of ordinary fertilized eggs are each punctured with a drill and injected with flu virus to make vaccines. Now, scientists at the same research institute that cloned Dolly the sheep have produced a genetically modified rooster whose female descendants lay eggs that produce medicines in place of a protein in egg whites. Helen Sang of the Roslin Institute in Edinburgh, Scotland, and her colleagues used lentivirus to introduce a gene into freshly fertilized chicken embryos that trigger the production of various drugs rather than the protein ovalbumin, which normally makes up roughly 54 percent of egg whites. The researchers screened the resultant cockerels for one that produced the new gene in its semen. They then bred him with normal hens to produce a flock of chickens that carried the inserted gene thereby producing medicines in their egg's whites.

Tests of the flocks' eggs showed that they could produce either miR24--a monoclonal antibody used in treating melanoma--or interferon b-1a--an immune system protein used against multiple sclerosis, among other things--depending on which gene was inserted. The chickens produce 15 to 50 micrograms per milliliter of egg white, the researchers found, and though this is not as efficient as the expression of ovalbumin, it is efficient enough to allow for subsequent purification into therapeutic drugs. "We would expect the transgene not to be as efficient as the endogenous gene it was based on as only some of the regulatory elements were used and the transgene may be inserted in the chromosome at a position that does not favor anywhere near maximal expression," notes Roslin's Adrian Sherman, who also participated in the research. "I'm sure there is potential for improvement."

Chicken eggs may prove a better way to producepharmaceuticals than other genetically modified products (such as goat milk) that have been previously explored. Chickens are easy to raise, produce numerous eggs, and are cheap to keep. And, after raising five generations of the modified birds, the researchers have observed no adverse health effects, according to the paper published online January 15 in Proceedings of the National Academy of Sciences USA. Even though the therapeutic proteins worked as intended during in vitro assays, it will be years before the process is ready to be used to produce drugs for human consumption, researchers say. Roslin's chickens join a similar effort using stem cells developed by Origen Therapeutics. Regardless of which "biofactory" delivers drugs first, a new medicinal use for the venerable egg is now apparent.

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