Amino acid homochirality may be linked to the origin of phosphate-based life

Phosphorylation has to have been one of the key events in prebiotic evolution on earth. In this article, the emergence of phosphoryl amino acid 5'-nucleosides having a P-N bond is described as a model of the origin of amino acid homochirality and Genetic Code. It is proposed that the intramolecular interaction between the nucleotide base and the amino acid side-chain influences the stability of particular amino acid 5'-nucleotides, and the interaction also selects for the chirality of amino acids. The differences between L: - and D: -conformation energies (DeltaE (conf)) are evaluated by DFT methods at the B3LYP/6-31G(d) level. Although, as expected, these DeltaE (conf) values are not large, they do give differences in energy that can distinguish the chirality of amino acids. Based on our calculations, the chiral selection of the earliest amino acids for L: -enantiomers seems to be determined by a clear stereochemical/physicochemical relationship. As later amino acids developed from the earliest amino acids, we deduce that the chirality of these late amino acids was inherited from that of the early amino acids. This idea reaches far back into evolution, and we hope that it will guide further experiments in this area.