A new thermodynamic analysis suggests that 10 of life's 20 amino acids must be common throughout the cosmos
One of the great outstanding questions in biology involves the evolution of the genetic code and the fact it relies on 20 amino acids. How did this system evolve and why use 20 amino acids and not some other number?
We know that amino acids are common in our solar system and beyond. Various first experiments to recreate the conditions in the Earth's early atmosphere have produced 10 of the amino acids found in proteins. Curiously, analyses of meteorite samples have found exactly these same 10 amino acids. Various researchers have noted this link but none have explained it.
They have ranked the amino acids found in proteins according to the thermodynamic likelihood of them forming. This turns out to match the observed abundances in meteorites and in early Earth simulations, more or less exactly
Thermodynamic arguments are as valid on Earth as they are in interstellar gas clouds
clipped from: www.technologyreview.com 