Reaction of Amino Acids in a Supercritical Water-Flow Reactor Simulating Submarine Hydrothermal Systems

A novel supercritical water flow-reactor was constructed in order to simulate submarine hydrothermal systems. The temperature of fluid inside the reaction tube could be monitored with thermocouples, which was proved to be different from the temperature outside the reaction tube. Oligomers of glycine up to tetraglycine were formed when a 100 mM glycine solution was heated at 200–350 °C for 2 minutes. None of glycine peptides were produced at 400 °C. It was suggested, however, that the formation of glycine condensates at higher temperature, including supercritical conditions of water. The stability of some amino acids under hydrothermal conditions was examined. ω-Amino acids and glutamic acid, which can form intramolecular condensates, showed higher stability than other α-amino acids at higher temperature, including supercritical conditions.