Sasaki Mitsuru, Miyagawa Yuji, Nonaka Kouki, Miyanomae Ryota, Quitain Armando T, Kida Tetsuya, Goto Motonobu, Honma Tetsuo, Furusato Tomohiro, Kawamura Kunio
Institute of Industrial Nanomaterials, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
Faculty of Advanced Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
Naturwissenschaften. 2022 Jun 10;109(4):33. doi: 10.1007/s00114-022-01803-y.
Conventional oligopeptide synthesis techniques involve environmentally harmful procedures and materials. In addition, the efficient accumulation of oligopeptides under Hadean Earth environments regarding the origin of life remains still unclear. In these processes, the formation of diketopiperazine is a big issue due to the strong inhibition for further elongation beyond dipeptides. Hydrothermal media enables environmentally friendly oligopeptide synthesis. However, hydrothermal oligopeptide synthesis produces large amounts of diketopiperazine (DKP), due to its thermodynamic stability. DKP inhibits dipeptide elongation and also constitutes an inhibitory pathway in conventional oligopeptide synthesis. Here, we show an efficient pathway for oligopeptide formation using a specially designed experimental setup to run both thermal and non-thermal discharge plasma, generated by nano-pulsed electric discharge with 16-23 kV voltage and 300-430 A current within ca. 500 ns. DKP (14%) was converted to dipeptides and higher oligopeptides in an aqueous solution containing alanine-DKP at pH 4.5, after 20 min of 50 pps thermal plasma irradiation. This is the first study to report efficient oligopeptide synthesis in aqueous medium using nano-pulsed plasma (with thermal plasma being more efficient than non-thermal plasma) via DKP ring-opening. This unexpected finding is implicative to evaluate the pathway how the oligopeptides could have accumulated in the primitive Earth with high-energy plasma sources such as thunder as well as to facilitate the green synthesis of oligopeptides.
传统的寡肽合成技术涉及对环境有害的程序和材料。此外，关于生命起源，在冥古宙地球环境下寡肽的有效积累仍不清楚。在这些过程中，由于二酮哌嗪对二肽以上进一步延伸的强烈抑制作用，其形成是一个大问题。水热介质能实现环境友好型寡肽合成。然而，由于其热力学稳定性，水热寡肽合成会产生大量二酮哌嗪（DKP）。DKP抑制二肽延伸，并且在传统寡肽合成中也构成一条抑制途径。在此，我们展示了一种高效的寡肽形成途径，使用专门设计的实验装置来运行热放电等离子体和非热放电等离子体，该等离子体由纳米脉冲放电产生，电压为16 - 23 kV，电流为300 - 430 A，持续时间约500 ns。在pH 4.5的含有丙氨酸 - DKP的水溶液中，经过20分钟50 pps的热等离子体照射后，14%的DKP转化为二肽和更高的寡肽。这是第一项报道通过DKP开环在水介质中使用纳米脉冲等离子体（热等离子体比非热等离子体更有效）进行高效寡肽合成的研究。这一意外发现对于评估寡肽在原始地球上如何通过雷电等高能等离子体源积累的途径以及促进寡肽的绿色合成具有启示意义。
