10:45 AM - 12:15 PM
[MTT38-P04] Formation of long-chain peptides from an amino acid under high pressure_Proposal for a new chemical evolution
Keywords:high pressure, amino acids, peptides
Amino acids are the building blocks of proteins, and oligomerization of amino acids under prebiotic conditions is one of the essential steps for the origin of life. The oligomerization of amino acids has been reported from high-pressure experiments simulating the impact of comets, hydrothermal vents, and diagenesis in sub-seafloor sedimentary environments (e.g., Sugahara and Mimura, 2015; Imai and Honda, 2010; Otake et al., 2011). Our group has focused on the oligomerization of amino acids under static high-pressure conditions at ambient temperature. Pressure-induced oligomerization of alanine occurred to form alanylalanine (dipeptide of alanine) and trialanine (tripeptide of alanine) at pressures of 5-11 GPa and at 25°C for 2 hours starting from alanine powder soaked in its saturated aqueous solution (Fujimoto et al., 2015). In addition, Takahashi et al. (2017) investigated the mechanism of pressure-induced oligomerization of alanine and raised the possibility that freeze concentration by the crystallization of ice VII, a high-pressure phase of ice, may enhance the pressure-induced oligomerization.
In this study, we further investigated the pressure-induced oligomerization reaction. L-alanine powder was loaded into a metallic gasket without an aqueous pressure medium and pressure was applied up to 16 GPa for 1 hour using an opposed-type sintered diamond anvil with a cup diameter of 3 mm. The recovered sample was dissolved in pure water and analyzed using LC-MS (LCMS-8045, Shimadzu). To determine the structures of long-chained alanine peptides, reference samples were synthesized up to the 13-mer by the solid-phase method using the standard Fmoc strategy.
The sample recovered from high pressure contained alanine peptides up to the 11-mer. The content of peptides decreased with increasing the chain length. In the present study, the formation of the cyclic dimer of alanine, DKP, was below the detection limit. This is consistent with a study on thermodynamic calculations showing that the chain dimer is more stable than DKP at room temperature, in contrast to the higher stability of DKP at high temperatures (Shock, 1992). Our results indicate that the pressurization at room temperature promotes the formation of long-chain peptides without producing DKP, which terminates the formation of chain peptides. This study suggests the possibility of the chemical evolution of amino acids inside the ice planet.
In this study, we further investigated the pressure-induced oligomerization reaction. L-alanine powder was loaded into a metallic gasket without an aqueous pressure medium and pressure was applied up to 16 GPa for 1 hour using an opposed-type sintered diamond anvil with a cup diameter of 3 mm. The recovered sample was dissolved in pure water and analyzed using LC-MS (LCMS-8045, Shimadzu). To determine the structures of long-chained alanine peptides, reference samples were synthesized up to the 13-mer by the solid-phase method using the standard Fmoc strategy.
The sample recovered from high pressure contained alanine peptides up to the 11-mer. The content of peptides decreased with increasing the chain length. In the present study, the formation of the cyclic dimer of alanine, DKP, was below the detection limit. This is consistent with a study on thermodynamic calculations showing that the chain dimer is more stable than DKP at room temperature, in contrast to the higher stability of DKP at high temperatures (Shock, 1992). Our results indicate that the pressurization at room temperature promotes the formation of long-chain peptides without producing DKP, which terminates the formation of chain peptides. This study suggests the possibility of the chemical evolution of amino acids inside the ice planet.