Many vertebrates are capable of changing color for camouflage, communication, and thermoregulation.
One such vertebrate, the Madagarcar panther chameleon, achieves these feats through its iridophores, which are an iridescent class of the pigment cells chromatophores. Vertebrates that change color using iridophores have cells that undergo structural changes, such as generating iridescent proteins or altering the lattice structure of nanocrystals within iridophores . This is the mechanism through which Madagascar panther chameleons are able to alter their pigment, using neural and hormonal signals to change the spacing between guanine nanocrystal layers in their iridophores. The increase in nanocrystal spacing shifts the reflectivity of the cells from short to long wavelengths, creating a blue/green to red/yellow color change. Multiple types of iridophores have been identified as a result of studying the Madagascar panther chameleon: S-iridophores, responsible for color change in the visible light spectrum, and a thicker layer D-iridophores, which reflect near-infrared light .
Effectively developing and employing guanine nanocrystal lattices for human use suggests multiple possibly beneficial applications. Two examples include textiles and paints. Materials and clothing integrated with guanine nanocrystals can be used for camouflage and thermal regulation. Paints infused with brick-shaped, more disorganized guanine nanocrystals, similar to those found in D-iridophores, can be used to reflect sunlight on buildings to decrease the amount of energy used in air conditioning units. Ease of synthesizing guanine, one of the four main nucleobases found in DNA, makes especially appealing the prospect of developing this nanotechnology at scale .
Male chameleons in relaxed and excited states exhibiting color change.
(Source: Teyssier et al., 2015)
- Teyssier, Jérémie, Suzanne V. Saenko, Dirk Marel, and Michel C. Milinkovitch. "Photonic Crystals Cause Active Colour Change in Chameleons." Nature(2015): n. pag. Web. 27 Mar. 2015.
- Levy, Matthew, Stanley L. Miller, and John Oró. "Production of Guanine from NH4CN Polymerizations." Journal of Molecular Evolution 49.2 (1999): 165-68. Web.
- "Guanine Toxicity Reports, Review - Hazard Potential, Risk." Bibra, Toxicology Advice and Consulting, 1998. Web. 27 Mar. 2015.
Using Transmission Electron Microscopy (TEM), researchers have identified the mechanisms through which Madagascar panther chameleons change color for camouflage, communication, and thermoregulation. The iridophores (iridescent pigment cells) of these reptiles utilize guanine nanocrystal layers to make structural changes to their cells, producing a color change. Neural and hormonal signals excite the nanocrystals and shift them farther apart within the iridophores, causing a change in wavelength reflectivity from short to long, or blue/green to red/yellow. The guanine nanocrystals in the iridophores can potentially be manufactured and used to create sustainable building materials and color changing, temperature regulating clothing.
Guanine, one of the four main nucleobases found in DNA, is also the by-product of the polymerization (chemical reaction of monomers to form a polymer) of ammonium cyanide monomers. The ability to artificially synthesize guanine nanocrystals allows for their mass production for use in sustainable building materials or color changing, temperature regulating clothing . Guanine nanocrystals can also be manipulated to change color in the presence of other organic materials, allowing the nanocrystals to be utilized as indicators of blood sugars levels in diabetic testing strips or used in oil spill detection .
Chromosomal damage to human and mouse cell cultures was evidenced upon exposure to guanine. No kidney damage or foetal deformities were evidenced as a result of guanine exposure .