Enhancement and Inhibitory Activities of Minerals for Alanine Oligopeptide Elongation Under Hydrothermal Conditions

Abstract

In a previous study, we have showed that the elongation of an alanine oligopeptide [L-alanyl-L-alanyl-L-alanyl-L-alanine ((Ala))] to higher oligopeptides is enhanced by calcite and dolomite at 275°C, using a mineral-mediated hydrothermal flow reactor system. However, a problem during the use of hydrothermal flow reactor system was that some of the minerals, such as clay, could not be tested due to their clogging in the reactor. In this article, we attempted to analyze the scope of enhancement for the formation of L-alanyl-L-alanyl-L-alanyl-L-alanyl-L-alanine ((Ala)) and higher oligopeptides with different minerals including clay minerals for the elongation of alanine oligopeptide at 175°C. First, carbonate minerals and some clay minerals showed an enhancement of the formation of (Ala) from (Ala). On the contrary, volcanic products showed strong inhibitory activities. According to the pH dependence on the (Ala) elongations, we confirmed that most enhancement and inhibitory activities are due to the pH influence on the elongation of (Ala). However, the enhancement of montmorillonite (Tsukinuno), sphalerite, apatite, tourmaline, calcite (Nitto Funka), and the inhibitory activities by volcanic ash (Shinmoedake), volcanic ash (Sakurajima), dickite, and pyrophillite are not simply due to the pH change in the presence of these minerals. The difference found between the previous and present studies suggests that the interaction kinetics of the aqueous phase with the mineral phase is also an important factor for the elongation of (Ala). These data imply that the environments with pH near neutral to weak alkaline and with minerals might have been useful for the accumulation of oligopeptides in hydrothermal conditions.

Peptide Synthesis under the Alkaline Hydrothermal Conditions on Enceladus

“…41 In relation to our alkaline hydrothermal system with a high abundance of CO 2 , the presence of carbonate minerals such as calcite and dolomite have been shown to promote peptide formation. 42,43 In our experiment, the formation of calcite was only confirmed under the presence of amino acids (Figure 1), suggesting that mineral−organic interaction has likely taken place.…”

“…Recent studies have shown that magnetite can alter the thermodynamic equilibrium of the system and greatly enhance the formation of the liner dimer while decreasing the amount of the diketopiperazines (DKP) under hydrothermal conditions . In relation to our alkaline hydrothermal system with a high abundance of CO 2 , the presence of carbonate minerals such as calcite and dolomite have been shown to promote peptide formation. , In our experiment, the formation of calcite was only confirmed under the presence of amino acids (Figure ), suggesting that mineral–organic interaction has likely taken place.…”