In the primordial world, inorganic materials came together to form simple organic molecules (amino acid, ribonucleic acids, and monosaccharides) and later complex biomolecules (the polymers of the previously mentioned) in the process of abiogenesis.
Although biologists agree that peptides played an indispensable role in the origins of life, but they are not quite sure about how they come into existence: enzymes are required to catalyze the reaction that links amino acids together to form peptides, but enzymes are themselves peptides.
A group of biochemists at the University College London (UCL) think that they might have stumbled upon a solution to this classic chicken-or-the-egg problem. By using a group of aminonitriles, different precursors other than amino acids, they managed to synthesize peptides.
In their study, the researchers devised a cyclic chain of selective and high-yielding reactions—alpha ligation to polymerize aminonitriles. Other reactants at their disposal are hydrogen sulfide, thioacetate, and ferricyanide or cyanoacetylene, a group of plausible compounds on our prehistoric Earth.
The availability of sulfur and cyanide ions is critical for these reactions. Take cyanide for example, an electron-rich anion that is prime for nucleophilic addition to add nitrogen atoms to carbon-based molecules. Hydrogen cyanide, abundant on young Earth as a result of asteroid bombardment, is postulated as a precursor to amino acids and nucleic acids, which are the basis for peptide and RNA/DNA.
This Molecule Could Explain the Origin of Life (Smithsonian Channel)
The chemistry behind this new peptide synthesis paradigm makes a strong case for energy conservation, a key component of natural processes. The aminonitriles themselves are precursors for amino acids, but the transformation requires strong acid or base, which is harsh and counter-productive for the next step, the production of peptides. Amino acids, before polymerization in a biological environment, must be recharged with energy. The pathway that UCL researchers discovered bypasses both steps and required much less energy, aligning well with nature's tendency to the least energy state (or the path of least resistance in human philosophical thinking).
This study was published as a research letter in the journal Nature in July.
Source: Science Daily
