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April 29 ALIEN BIOLOGYIt is arsenic, but not as we know it. Author : Michael Reilly A deadly poison, arsenic is best known for snuffing out life. But could it (have) played a role in the origins of life on earth ? Felisa Wolfe-Simon of Harvard University thinks so, because the toxin behaves so similarly to Phosphorus, an essential ingredient in nearly all living things. Much more, Arsenic would have been available in (the) Earth's primordial oceans than Phosphorus (would have been). While microbial activity was necessary later to unlock phosphorus from the rocks, Arsenic could have dissolved in water from hydrothermal vents. Phosphorus binds to four oxygen atoms to form a negatively charged Phosphate ion that is used to build the backbone of (the) DNA's double helix. Phosphate is also key in Adenosine Triphosphate (ATP), the "universal energy currency" that supplies energy to most (of) life on Earth. Wolfe-Simon and Paul Davies of Arizona State University in Tempe think Arsenic could do the same jobs. Just as Phosphorus forms Phosphate ions, so Arsenic readily forms Arsenate ions. Arsenate is not suitable for life (on Earth) today, because it tends to latch onto Adenosine Diphosphate molecules, blocking the production of ATP. However, without much Phosphorus available, the first life (on Earth) might have evolved to make use of the next best thing, Wolfe-Simon says. , the "A" letter in (the) DNA code of A, C, G and T, Wolfe-Simon says. If early life did use Arsenate, (then) single-celled organisms with Arsenate based DNA may still be around today wherever Phosphorus is scarce. The only stumbling block to the idea is that Arsenic based DNA tends to break down quickly."You do not want to build your DNA out of a compound with a half-life in the order of a couple of minutes," points out Steve Benner of the Foundation for Applied Molecular Evolution in Gainesville, Florida. However, he points out that it could be a good thing in extreme cold, where chemical reactions move very slowly. Microbes living in Antarctica or on Saturns moon Titan might find Phosphate based DNA (to be) too sluggish to work with and (thus) have evolved to take advantage of (the) faster-reacting Arsenate instead.Source : NEW SCIENTIST 26 April 2008 Pg 10. Grammar corrections inserted by independent editor DEEPBLUESKY (tm).
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