The Synthesis And Self-assembly Of Amphiphiles Before The Origin Of Life

How did life arise? This issue is old,mysterious,and full of challenges.The evolution of life on the early earth follows the process from simple to complex.How to realize this evolutionary process is an unsolved mystery in the current scientific issues.The origin of life can be roughly divided into two stages.First,inorganic molecules gradually evolved into oligopeptides,nucleotides,phospholipids and other ingredients for life.Second,macromolecules carried complex interactions and assembled into primitive cells,that is,the origin of prebiotic chemistry and its transition to simple biology.The most special progress made in scientific research is the emergence of amphiphilic compounds,which is one of the landmark studies from prebiotic synthesis to simple biology.Fatty acids have unique amphiphilic properties,and they can selfassemble into vesicles in aqueous solution.With simpler chemical structure than phospholipids,fatty acids are considered as possible constituents of the protocell membrane.However,vesicles formed by fatty acids are susceptible to environment.The optimum p H value of vesicle formation is their corresponding p Ka value,they would grow into corresponding acid droplets or micelles respectively in more acidic or alkaline conditions.Meanwhile,vesicles formed by carboxylic acid are easily disturbed by salt ion in aqueous solutions.In this paper,we studied the prebiotic synthesis and self-assembly of amphiphiles.Experiments simulated two important kinds of environmental conditions of the early Earth-hydrothermal vents and the evaporation pond model.Long chain primary alcohols and carboxylic acid ester compounds were separately obtained,both of which could enhance the anti-interference capability of fatty acid vesicles.Through the experiments researches,we explored the evolution of protocell membrane in the origin of life.First,we simulated the environment of alkaline hydrothermal vent,explored the synthetic mechanism to long-chain alcohols,and studied its effect on the stability of protocell membrane.Ethanol,a small molecule that may exist on the early earth,is selected,with the presence of copper and its oxides,we detected the formation of butanol,hexanol,octanol,and decanol.Through the analysis of the main products and intermediate products,we deduced that the reaction of ethanol to long chain alcohols underwent the dehydrogenation of ethanol,aldol condensation and hydrogenation reaction.We brought Guerbet Reaction into the hydrothermal system,simulation of marine hydrothermal vent environment,providing a possible new way of the abiotic synthesis to long-chain primary alcohols.It increased the property of fatty acids assembling into membrane structure in a wider p H range.It is of great significance in the process of the origin of cellular life.Second,We realized conversion of decanoic acid to glyceryl decanoates under wetting-drying cycles in simulated evaporation pond model,and studied the encapsulation of organic compounds by vesicles in a rehydration system,besides,the effect of glyceryl decanoates on the stability of decanoic acid vesicles was conducted.Nonenzymatic dehydration reactions of decanoic acid with glycerol has been reported to occur,yielding more evolved membrane precursor compound glyceryl decanoates.Two isomers of glyceryl monodecanoate were the main products after the condensation reactions,and the yield of glyceryl monodecanoates increased to 4.7% with the rising of temperature.The hydration-rehydration system enabled vesicles to encapsulate the organic compounds in the solution during its formation and provided a place for the enrichment and evolution of these organic compounds.The experimental results showed that the formation of trace glycerides obviously decreased the CVC of decanoic acid,and promoted the stability of the mixed system to salt.This part of experimental research has realized the abiotic evolution of carboxylic acid to glyceride alkanoate,It implied that the condensation reaction is plausible for yielding more complex amphiphiles and the appearance of membrane structures to stabilize in the original ocean filled with salt solution.The origin of life could not be reproduced,and we can only trace the evolution of life billions of years ago through the existing environmental system.Through the exploration of the origin of life,we can gradually grasp the law of the occurrence and development of life,so as to make a more comprehensive understanding of the essence of life.This paper mainly studies the abiotic synthesis and self-assembly of amphiphiles on the early earth,and explores another possible way for the origin of cellular life.