Investigation On Vesiculation Of Conjugated Linoleic Acid Driven By Phospholipid-like Amphiphiles At Near-neutral PH

Metabolic machinery,membrane compartment and genetic / template mechanisms are three main interdependent components of life.One of recent researchs of origin of life and model protocell membrane has focused on single-chain fatty acid vesicles(FAV).Long chain fatty acids are life essential,and have many other features such as molecular structure simplicity and self-organization activity,so it is generally accepted by scholars as a molecular block of self-organized FAV,which is one of the most possibility of the origin of lipid compartments related to abiogenesis.However,FAV can only self-organized and self-replicated within the alkaline scope,and whether in modern or prehistoric earth near-neutral water environment and the objective condition that no pre-existing FAV template are contradictory with pH sensitivity of FAV,leading to the current study of prehistoric membrane model can't explain the hand of god of how the first FAV spontaneous formed in prehistoric environment.Therefore,FAV are restricted not only in the field of simulating the phenomenon of prehistoric lipid compartment but also in cosmetics and drug delivery fields as a modern embedding slow-released system.Lecithin is recognized as main composition of modern membrane,but in the absence of modern replication mechanism or strong interference from outside environment,the strong hydrophobicity given by its double-chain lead to vesicles cannot self-organized;and its strong hydrophobicity of vesicle surface caused the lack of dynamic features and Darwinian evolution between membrane leafs,thus vesicles are unable to self-replicate.This paper will study whether mixture of phospholipid analogues and fatty acids could self-organize together to simulate prehistoric membrane model or not.The details are on the follwing: I.Phospholipid analogues drive conjugated linoleic acid construct the model of protocell membranes at near-neutral pHAs mentioned above,phospholipid vesicles cannot self-organize,so phosphatidylcholine(PC)was blended with conjugated linoleic acid(CLA)to study the possibility of vesiculation at prehistoric near-neutral pH,the result showed that vesicles could formed in absence of template and shear force,but the pH window for vesiculation couldnot enlarged.Lysophosphatidylcholine(LPC)is a natural phospholipid-like amphiphile,it may be the precursor molecules of phospholipids in prehistoric evolution.The pH window for vesiculation and the particles sizes of CLA vesicles driven by LPC were measured by dynamic light scattering(DLS),then the images of aggregates were acquired by transmission electron microscopy(TEM).Results showed that self-organized vesicles of CLA formed driven by 3 % molar content of LPC,within the scope of pH 6.4 to 8.2,and pH window width for vesiculation can span 3.6 units with the increasing amount of LPC.Various charged species of CLA and LPC with pH variation were investigated by pH titration curve and conductivity curve,the impetus driving vesiculation of CLA driven by LPC in the weakly acidic to neutral pH range was illustrated as the formation of hydrogen bonding and ion-dipole effect.This model will support the speculation that protocellular membrane models based on fatty acids vesicles.Lysophospholipid acid(LPA)is a kind of anionic phospholipid-like amphiphile without choline molecular,so it may be appear earlier than LPC in the prehistoric period,and may be formed at the same time or later with fatty acids.It also has important theoretical significance that investigation of vesiculation for CLA driven by LPA at neutral pH.It was found that the pH window for vesiculation is 6.5-8.5 when the LPA molar content was 5 %.Although the pH window was migrated to neutral pH driven by few LPA,LPA exhibits a low efficiency compared with LPC.LPC exhibits excellent efficiency because the terminal N+ of LPC increases the stability of vesicle structure.II.Vesiculation for conjugated linoleic acid driven by synthetic surfactants at near-neutral pHTo compare the efficiency of vesiculation with natural amphiphilic molecules in the second chapter at neutral pH,synthetic surfactants dodecyl hydroxypropyl phosphate betaine(DHPB),cocoamidopropyl betaine(CAB)and monolauryl phosphate(MLP)were blended with conjugated linoleic acid.The results showed the natural phospholipid-like amphiphiles had higher efficiency.In addition,pH windows for vesiculation of CLA driven by MLP were paid more attention,the impetus driving vesiculation of CLA in the weakly acidic to neutral pH range was illustrated as the formation of hydrogen bonding or ion-dipole effect.Preliminary practical performances of hybrid FAV were evaluated in this paper.Based on the drug slow-release of CLA-LPC system,it was found that CLA vesicles driven by LPC have good slow-release performance.Solubilization and foam properties of CLA-CAB system were studied to find more application fields of FAV,it was found that solubilising power of vesicle solution is better than micelle solution.