The Ultra Small Amphiphilic Molecules Vesicles Self Assembly Formation And Mechanism Study

Molecular self-assembly is a common phenomenon in nature,and has been a hot research field for many years.Molecular self-assembly is the basis for the realization of many biological activities and biological functions.In 2013,the Nobel Prize was granted for the great found about vesicle trafficking,since then the study on the mechanism of vesicle trafficking is becoming more and more popular.The cell membrane consists of lipid bilayer and membrane protein,and the structure of biofilm directly affects on the transport of substances inside and outside cells.The vesicles can control of molecular transfer accurately controlled through the fusion of vesicles and membrane.The precise controlled release has attracted extensive attention in the fields of medical,food and life science.In recent years,the research about self-assembly mainly fouse on materials science,drug delivery system,bioengineering and other research fields,such as the assembly of polymer materials science;vesicle lipid encapsulated drug as a carrier and so on.The development of life science and materials science has promoted the study of the interaction between molecules.In the organism,many molecules are combined in a highly ordered manner,so as to have certain functions.For example,an essential part of the metabolic process like the formation of a highly ordered array of phospholipids and cholesterol in the cell membrane.The interaction of vesicles with channel proteins and membrane phospholipids can change the structure and fluidity of membrane phospholipids,which may cause cell membrane integrity,barrier function,cell differentiation and maturation.The membrane not only regulates and controls the exchange of material inside and outside the cell,but also forms the membrane vesicles by the membrane to realize the material transport,for example the absorption of nutrients by small intestinal epithelial cells.The cells can secreted vesicles into the extracellular environment with a diameter of about 100-1000nm,those vesicles are rich in glycerol phosphate esters,saturated fatty acyl chains,cholesterol,etc,carrying specific proteins,lipids,RNA and DNA,signaling molecules in cells.The protein interacts with the phospholipid polar head by its charged amino acid or group.At the same time,the composition of membrane fatty acid plays an important role in membrane fluidity.Electric field induced by positive and negative charges.The external electric field can affect the ion pump on the membrane,membrane mechanical properties and bound water molecule,which can changes cell morphology and cell membrane potential.Recently,the Science and the Journal of biological fields published a series of articles and articles related to vesicles,it is indicated that the important role of the vesicles in physiological activities is being strengthenedAt present,the international research about vesicles mainly focus on two aspects.The first one is the study on the dynamic properties of single chain surfactant aggregation structure and the theory of pH induced transformation,just like a large number of biomaterials have been produced by the use of noncovalent interactions through a multi-level self-assembly process.The second one,the vesicle was used as the primary cell model to study the transformation process from monomer to sphere.The primary vesicles were saturated or unsaturated long-chain fatty acids,such as oleic acid,linoleic acid.In our research,we have found that small organic molecules can also self-assembled to form vesicles,such as fatty acids,natural amino acids and other small molecules,through changing the the protonation/ionization of carboxyl terminus.The ultra-small amphiphilic molecules with specific structure,such as the linear non-natural amino acid,can form the ordered and stable structure aggregates by the intermolecular noncovalent bond force.In particular,fatty acids and amino acids are widely distributed in body.Under certain conditions,those small molecules are self-assembled to form vesicle structure.At the same time,such vesicles and apoptotic bodies secreted by the cells into the extracellular environment have a similar hollow spherical structure with diameters in the 200nm range.Therefore,the studies of the formation conditions and mechanism of fatty acids,amino acids and other small molecules will help us to understand the phenomenon of life activities.To our best knowledge the study of small molecules self-assembly,especially ultra-small amphiphilic molecules has not been reported.It is generally believed that the chain length Cn<8 is not easy assemble to form a stable vesicle structure.In our study we found that the chain length of fatty acid in ultra-small single stranded 5<Cn<8 can also self-assembly form stable spherical vesicle structure under certain conditions.Through experiment of the aggregation morphology with different chain length of single stranded molecule in aqueous solution.We mainly focused on the formation of the vesicles in the aqueous phase by the self-polymerization of the shortest chain saturated fatty acids,the natural amino acids,the non-linear single chain amino acids.Thus,we also discussed the formation mechanism,stability and the relationship between structure and properties,and so on.Using infrared spectroscopy(FT-IR),ultraviolet visible spectroscopy(UV-vis),particle size analyzer,confocal laser scanning microscope(CLSM),transmission electron microscopy(TEM)and cryogenic transmission electron microscopy(Cryo-TEM)to study the self-assembly and surface morphology.The particle size and dispersion coefficient were measured by Zetapals potential analyzer.Moreover,we design of pH change,chain length relationship,solvent interface and other self-assembly control methods to investigate the concentration,temperature,pH and other biological intermediates in order to release the mechanism of self-assembly in biological metabolism.We also developed a set of methods based on the interaction between the vesicles and fluorescent probes.The membrane potential sensitive fluorescent probe Di-8-ANEPPS was used to label the surface of cell membrane.The intensity of fluorescence reflected the change of cell membrane potential.When the cells were polarized,the membrane potential increased,while the fluorescence intensity of Di-8-ANEPPS increased.On the contrary,the fluorescence intensity of Di-8-ANEPPS decreased with the membrane potential decreased.The changes of fluorescence intensity of Di-8-ANEPPS labeled cell membrane were observed by fluorescence microscopy.The feature of this method is that the cells are not damaged,can realize the nondestructive,accurate measurement,and fast and dynamic response of the membrane potential changes caused by environmental changes.So the method can effectively reflect the cell structure and physiological changes caused by the interaction between the vesicles and cells.Based on the process and regulation of the ultra-small amphiphilic molecules ordered self-assembly were analyzed,determine the reasonable self-assembly conditions.Study on the mechanism of ultra-small amphiphilic molecules self-assembly from the point of view of biophysical chemistry,which is helpful understand the phenomenon of vesicle aggregation and the exploration of its mechanism.Starting from the simple model membrane,we try to reveal the physical and chemical laws corresponding to the biofilm function.In particular,the understanding of the formation and the mechanism of the ultra-small amphiphilic molecules assembly,which can provide scientific theoretical basis and research value in the field of food nutrition absorption,drug loading system,biomedicine and so on.