Experimental and Computational Simulation of the Prebiotic Peptide Bond Formation Driven by Wet-Dry Cycles and Gamma Ionizing Radiation: An Insight into Molecular Evolution.

The origin of life through prebiotic chemistry and molecular evolution processes is a significant and unresolved issue in science. A key part of this process is how simple molecules, such as amino acids, transition into functional polymers, like peptides, which can store information and facilitate reactions. During this transition, wet-dry cycles and the interaction with ionizing radiation are essential mechanisms for increasing molecular complexity. This process involves the repeated hydration and dehydration of organic compounds, promoting the formation of peptide bonds that connect amino acids into longer chains. On a faster-spinning ancient Earth, these cycles might have been more relevant for the shorter days. In this scenario, a faster rotation rate affected the climate, tidal forces, and evaporation rates. The transition from simple amino acids to functional peptides remains a central question in understanding the complexation of molecules that led to life's origins. This work investigates how hydration-dehydration cycles impact solid-state gamma irradiated (40 kGy) DL-glutamic acid oligomerization. Infrared spectroscopy analysis confirms the presence of the characteristic amide I and II bands (approximately 1700 -1500 cm⁻¹), indicating an apparent change in peptide bond formation in gamma-irradiated samples. DSC and TGA thermal analysis reveal a contrasting difference in the thermograms from the control and gamma-irradiated samples. Thermal analyses demonstrate enhanced thermal stability in irradiated samples, agreeing with HyperChem computer simulations. The increase in stability in the oligomerization process. These findings support the model where cosmic ionizing radiation synergized with more frequent wet-dry cycles to promote prebiotic peptide synthesis. Our preliminary results substantiate the possibility that dry-wet cycles and ionizing irradiation on ancient Earth might have had planetary conditions to drive the molecular evolution towards abiotic synthesis of peptides.