Pressure Effects on the Abiotic Polymerization of Glycine

Abstract

Polymerization experiments were performed using dry glycine under various pressures of 5-100 MPa at 150 degrees C for 1-32 days. The series of experiments was carried out under the assumption that the pore space of deep sediments was adequate for dehydration polymerization of pre-biotic molecules. The products show various colors ranging from dark brown to light yellow, depending on the pressure. Visible and infrared spectroscopy reveal that the coloring is the result of formation of melanoidins at lower pressures. High-performance liquid chromatography and mass spectrometry analyses of the products show that: (1) glycine in all the experimental runs oligomerizes from 2-mer to 10-mer; (2) the yields are dependent on pressure up to 25 MPa and decrease slightly thereafter; and (3) polymerization progressed for the first 8 days, while the amounts of oligomers remained constant for longer-duration runs of up to 32 days. These results suggest that pressure inhibits the decomposition of amino acids and encourages polymerization in the absence of a catalyst. Our results further imply that abiotic polymerization could have occurred during diagenesis in deep sediments rather than in oceans.

Hydration–dehydration interactions between glycine and anhydrous salts: Implications for a chemical evolution of life

“…An absorption band at 338 nm and a small shoulder band around 460 nm were observed, and these intensities increased with time. These band positions are under typical absorption region of Mailard products Pongor et al, 1984;Ohara et al, 2007). The other Gly-salt mixtures also showed the similar UV-Vis absorption bands, whereas each intensity was different.…”

“…These products are major decomposition products of Gly (Klingler et al, 2007). The other cause would be formations of melanoidins from Gly and its decomposition products through Maillard reaction (Ohara et al, 2007). Fig.…”

Role of Clay Minerals in Chemical Evolution and the Origins of Life

“…As a result, the concentration of organic molecules would increase, promoting their polymerization [47]. The synthesis of glycine peptides with montmorillonite under trench-like hydrothermal conditions (5−100 MPa pressure; 150 C temperature) has been reported by Ohara et al (2007) who obtained up to 10-mers of glycine [48].…”

Survivability and reactivity of glycine and alanine in early oceans: effects of meteorite impacts

“…During the decomposition process, a large amount of deketopierazine was detected in the products from glycine. The amount of diketopierazine produced from dry glycine at 150°C and 5-100 MPa increased gradually in~10 days with increasing reaction time [18]. We did not analyze diglycine and diketopierazine, but according to the previous studies [43,46], they might have been formed in our products.…”

“…Through studies on glycine at high pressure and temperature under dry conditions, high pressure has been shown to have a significant effect on stability [17] as well as polymerization [18,19]. High temperature and high pressure induced by meteorite impacts may have fatal changes to amino acids [20,21].…”