Prebiotic Peptide Synthesis

摘要

About four billion years ago on the primitive Earth, chemical processes yielded molecules that had the ability to make copies of themselves (self-replicate). Over evolutionary time, these replicating molecules developed into the deoxyribonucleic acid (DNA) protein-replicating system of modem life. Although the DNA molecule has a structure that makes it an excellent self-replicating molecule, its structure is too complex to have been synthesized by chemical processes on the early prebiotic Earth. This difficulty with the prebiotic synthesis of DNA has led to a search for simpler replicating molecules. One of the best candidates for a primitive replicating molecule is a small protein, called a peptide. Peptides are considered good candidates because they are constructed from very simple building blocks-activated amino acid molecules-that could have been made by chemical processes on the primitive Earth. To understand the prebiotic processes on the early Earth that could have generated replicating molecules, such as peptides, this study has examined plausible prebiotic chemical processes that have the potential to yield peptides and other replicating molecules from very simple chemical ingredients such as formaldehyde and derived sugars, and analyzed the thermodynamics of carbon chemistry to establish which types of organic reactions are energetically favorable or unfavorable under mild aqueous conditions.