Other Uses
The word guanine derives from the Spanish loanword guano ('bird/bat droppings'), which itself is from the Quechua word huanu or wanu, meaning 'dung.' As the Oxford English Dictionary notes, guanine is "A white amorphous substance obtained abundantly from guano, forming a constituent of the excrement of birds".
In 1656 in Paris, François Jaquin (a rosary maker) extracted from scales of some fishes the so-called pearl essence, crystalline guanine forming G-quadruplexes. In the cosmetics industry, crystalline guanine is used as an additive to various products (e.g., shampoos), where it provides a pearly iridescent effect. It is also used in metallic paints and simulated pearls and plastics. It provides shimmering luster to eye shadow and nail polish. Facial treatments using the droppings, or guano, from Japanese nightingales have been used in Japan and elsewhere, reportedly because the guanine in the droppings produces a clear, "bright" skin tone that users desire. Guanine crystals are rhombic platelets composed of multiple transparent layers, but they have a high index of refraction that partially reflects and transmits light from layer to layer, thus producing a pearly luster. It can be applied by spray, painting, or dipping. It may irritate the eyes. Its alternatives are mica, faux pearl (from ground shells), and aluminium and bronze particles.
Spiders and scorpions convert ammonia, as a product of protein metabolism in the cells, to guanine, as it can be excreted with minimal water loss.
Guanine is found in integumentary system of many fish such as sturgeon. It is also present in the reflective deposits of the eyes of deep-sea fish and some reptiles such as crocodiles.
On August 8, 2011, a report, based on NASA studies with meteorites found on Earth, was published suggesting building blocks of DNA and RNA (guanine, adenine and related organic molecules) may have been formed extraterrestrially in outer space.
Read more about this topic: Guanine