Simulating Lost City Hydrothermal Field:Study On The Relationship Between Prebiotic Peptide Synthesis And The Origin Of The Genetic Code

The genetic code controls biological processes such as organism growth and reproduction.Therefore,the origin of the genetic code has naturally become one of the most fundamental problems in the origin of life.Based on chemical and archeological studies on the origin of life,the Lost City hydrothermal vent(pH 9-11)has been considered as a potential site of origin of life on earth.It is worth noting that the role of genetic code is only in the process of peptide biosynthesis.We supposed that the origin of the genetic code might be somehow associated with prebiotic peptide synthesis.Based on the regulation of prebiotic peptide synthesis by trimetaphosphate(P3m),therefore,in this paper,the Lost City hydrothermal vent conditions(temperature,pH and pressure)were simulated for the relevant researches.The details were as follows:1)A study on the correlation between peptide synthesis and the origin of the genetic code:Prebiotic peptide synthesis and the origin of the genetic code are central issues concerning the origin of life,and the question of how they are possibly correlated in the Hadean environment remains perplexing.Aminoacyladenylates(5'-aa-AMPs)are the key intermediates involving in peptide synthesis,but the pity is that their formation under prebiotic conditions is still unknown.Here we report the generation of nucleotide amidates(aa-N-NMPs),analogs of 5'-aa-AMPs,that obtained from amino acids,nucleosides and trimetaphosphate under alkaline condition simulating the Lost City hydrothermal vent.Fifty-six aa-N-NMPs were detected and identified by high performance liquid chromatography-electron spray ionization-high resolution MS(HPLC-ESI-HRMS).Significantly,dipeptides were detected from above reactions and the yields of dipeptides varied with different nucleosides through the formation of different aa-N-NMPs.This model provides both prebiotic peptides and the primordial version of the genetic code in parallel through reactions occurred under potentially prebiotic conditions.2)Prebiotic formation of cyclic dipeptides.Cyclic dipeptides,also known as 2,5-diketopiperazines(DKPs),represent the simplest peptides that were first completely characterized.DKPs can catalyze the chiral selection of reactions and are considered as peptide precursors.The origin of biochemical chirality and synthesis of peptides remains abstruse problem believed to be essential precondition to origin of life.Therefore,it is reasonable to believe that the DKPs play a key role in the origin of life.How the formation of the DKPs through the condensation of unprotected amino acids in simulated prebiotic conditions has been unclear.Herein,it was found that cyclo-Pro-Pro could be formed directly from unprotected proline in the aqueous solution of trimetaphosphate(P3m)under mild condition with the yield up to 97%.Other amino acids were found to form proline-containing DKPs under the same conditions in spite of lower yield.During the formation process of these DKPs,P3m promotes the formation of linear dipeptides in the first step of the mechanism.The above findings are helpful and significant for understanding the prebiotic formation of DKPs and provid the possibility for DKPs to play a role in the process of chemical evolution of life.3)Effect of high hydrostatic pressure on prebiotic dipeptide formation.Prebiotic peptide synthesis is a central issue concerning life's origins.Many studies considered that life might come from Hadean deep-sea environment,that is,under high hydrostatic pressure conditions.However,the properties of prebiotic peptide synthesis under high hydrostatic pressure conditions have seldom been mentioned.Here we report that the yields of dipeptides increase with raising pressure.Significantly,effect of pressure on the formation of dipeptide were obvious at relatively low temperature.Considering that the deep sea is of high hydrostatic pressure,the pressure may serve as one of the key factors in prebiotic peptide synthesis under Hadean deep-sea environment.The high hydrostatic pressure should be considered as one of the significant factors in studying the origin of life.