Amino acids are fundamental to life as the building blocks with which cells construct proteins according to genetic instructions. However, the 20 amino acids of the standard genetic code represent a tiny fraction of the number of amino acid chemical structures that could plausibly play such a role, both from the perspective of natural processes by which life emerged and evolved, and from the perspective of human-engineered genetically coded proteins.

Until now, efforts to describe the structures comprising this broader set, or even estimate their number, have been hampered by the complex properties of organic molecules. In a new study astrobiologists used computer software based on graph theory and constructive combinatorics to search for the chemical structures implied by two careful and precise definitions of the amino acids relevant to biological proteins.

Their results include two virtual libraries of amino acid structures corresponding to these different approaches, and suggest a simple approach to exploring much larger libraries of interest.