(713e) Elongation of Alanine Induced by Discharged Plasma Under Hydrothermal Condition

It is well known that some essential organic compounds such as amino acids are synthesized and composed in deep sea due to natural occurrence of supercritical water conditions in volcanic and hydrothermal vents. Elongation of amino acids under hydrothermal conditions had also been reported, however, the yields of the direct formation of oligopeptides from amino acid monomers in these systems were very low at 0.1-1%. Other than the hydrothermal vent system, there could be other factors responsible for the more efficient generation of oligopeptides. Discharge plasmas which can be naturally generated during lightning could be one likely reason for this. In this study, experiments on amino acids in subcritical water as a reaction media and the effects of various parameters of pulsed high-voltage arc discharge plasmas were carried out. The possibility for elongation of amino acids and oligopeptides was also evaluated. Such plasma applied under hydrothermal conditions generates high-energy electrons, ions, and radicals, which in turn may generate new reaction fields, leading to effective organic compounds oxidation for both homogeneous and heterogeneous reactions. On the other hand, from the viewpoint of the demand for environmentally harmless organic synthetic processes, the efficient preparation of oligopeptides without organic solvent is attractive.

Reactors made of SUS316 (50 mL) were used for plasma generation experiment. Two sapphire windows were installed in the reactor to monitor the performance of plasma production. The electrodes were set up at the center of the reactors. 0.1 mol/L of alanine monomer solution was used as a starting material. Reactions by using discharged plasma in hydrothermal and pressurized conditions were carried out at various temperatures and pressures up to 523K and 25MPa, respectively. After the reaction, liquid products were analyzed by high performance liquid chromatography (HPLC) and Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOFMS). Results showed that oligopeptides could be obtained via elongation of amino acid monomer.