Hydrothermal Synthesis Of Biomicromolecule In The Chemical Evolution

In this study, we focus on the hydrothermal synthesis of organicmicromolecule in the process of the origin of life, and examine the effect of thecatalyst by the use of other metals and zeolites under the same conditions. By theresearch of the kinetic experiment for the reaction, we discuss the mechanisms ofthe reaction and the interaction between organic molecules and metal catalysts.These data provide a feasible route of chemical evolution in the primordial earth.1. Hydrothermal synthesis of phenol from carbon dioxide. It has beenproposed that CO2 is vented to the surface or atmosphere to be carbon sources andinto the magma ocean or mantle to be sinks;the relevant sinks turned to becarbonates as CaCO₃ or MgCO₃ by the alteration of shallow rocks near the ambientocean temperature. Subsequent reactions of CaCO₃, MgCO₃ and CO2 in theprimeval watery environments, producing amino acids or their fragments, musthave a clear implication for the abiotic synthesis of complex organic molecules inthe origin of life. Since sodium hydrogen carbonate can be translated into CO2, thissimulates the ocean environments of the primordial earth in a certain geologicaltime interval. We carry out study on the reactions of sodium hydrogen carbonatewith water in the presence of iron powder based on the well-established mildhydrothermal method. The results indicate that only phenol was formed after thehydrothermal reactions. Products were identified by gas chromatography-massspectroscopy (GC-MS). Formation of phenol involves complicated hydrothermalreactions of sodium hydrogen carbonate with water at the surface of powder metaliron, but basically via oxidative coupling reactions and rearrangements. The yieldof phenol is 0.8 % in mole according to NaHCO3. Though the yield is too low, ourstudy on the hydrothermal reactions from sodium hydrogen carbonate to phenolprovides a new synthesis route based on the inactive CO2 molecule, which isimportant to form prebiotic organic molecules2. By the methods of hydrothermal synthesis, we carry out the reactions offormaldehyde with water in the presence of metal iron powder under hydrothermalconditions, obtain at least six main products were identified by mass spectroscopy(MS) as formic acid (HCOOH), acetic acid (CH3COOH), propionic acid(C2H5COOH), methyl acetate (C3H6O2), propyl propionate (C6H12O2) and propylisobutyrate (C7H14O2), analyze and discuss mechanisms of the reaction base on thesynthesis. We examine the effect of the catalyst by the use of other metals andzeolites under the same conditions. In order to examine the yields of main productsat certain reaction time, we carry out kinetic experiments. We also carry out theexperiments of filling capacity of reactor, which is related to reaction pressure.We continued our experiments with adding ammonia into the reaction systems.During the reaction of ammonia with acetic acid or propionic acid, we witnessedthe formation of two amino acids, namely glycine and racemic D, L-alanine in thepresence of Fe2O3, as indicated by high pressure liquid chromatography (HPLC)spectra.The formation of the racemic amino acids gives us an impetus to detectwhether chirality could be stabilized in the formation of peptide in hydrothermalsystems. We carried out the synthesis of peptide from amino acids based on ourprevious experiments. Oligopeptides were found even without any catalyst asindicated by LC-MS/MS.Because peptide bond is of paramount relevance for the stability and structuralfeatures of all known proteins, so we propose that the formation of dipeptideprovides a feasible route of the formation of protein in the process of the origin oflife.From above results, we realize that, though make a process in hydrothermalsynthesis of chemical evolution, much work should be done further to establish themechanisms completely and the synthesis of biomolecule (e.g. nucleic acid andprotein). Furthermore, the observation that the yield of DD-or LL-dialanine washigher than that of DL-or LD-dialanine not only gives us a plausible explanationfor the formation of these biopolymers from hydrothermal systems, but also makesus interested in the origin of homochirality in chemical evolution of early life.