Nonrandomness in prebiotic peptide synthesis.

We have synthesized and studied the properties of phosphoanhydrides of alanine with guanosine monophosphate, uridine monophosphate, and adenosine monophosphate. This series of compounds allowed us to investigate the specificity of peptide bound formation in a reaction that could have taken place on the prebiotic earth. We asked whether the intrinsic reactivity of the amino acids, the nature of the nucleotide in the anhydride, or the complementary polynucleotide template influences the specificity of the peptide synthesis reaction. We observed that the differential reactivity of the amino acids results in nearest-neighbor preferences during the peptide synthesis, whereas the nature of the nucleotides and the presence of complementary polynucleotides had no influence on the specificity. These results suggest that some peptides would have been more abundant than others on the prebiotic earth and have implications for the study of the origins of the genetic code and protein synthesis.