Adenine from outer space

A major goal of origin-of-life studies is to determine potential mechanisms for the prebiotic synthesis of nucleic acid bases, such as adenine. Possible adenine precursors are known to exist in space, and adenine has been observed in asteroids and comets. Rainer Glaser of the University of Missouri, Columbia, and coworkers now have used a theoretical model of gas-phase chemistry to predict mechanisms for adenine production in space (Astrobiology 2007, 7, 455). The most likely pathway is a four-step cyclization of the precursor aminoimidazolecarbonitrile (shown, left) to adenine (right). The key reaction step requires no catalyst, has essentially no activation barrier, and is irreversible. The mechanism implies that "it's adenine's destiny to accumulate," Glaser says. "This might explain why it eventually became a central molecule in life processes." If adenine formation occurs throughout space, "life everywhere might have started out pretty much the same way," he adds.