Glutamic Acid-based Surfactant Molecules Organized Assembly And The Interaction Of Biologically Active Molecules

Recently,the research on green surfactant,which has become safe and biodegradable, is a developing direction of surfactant industry.In this dissertation,glutamic acid-based surfactants with single and double chains were synthesized,and their phase behavior and their interaction with bio-molecules were studied.There studies will contribute to understand the effects of the structure of glutamic acid-based surfactants on their aggregates and the conformation of bio-molecules,and be benefitial to promote the glutamic acid-based surfactants to apply in commercial production.Six parts are included.1.The self-organization properties of n-dodecylammoniumα-glutamate (GDA)/n-C_sH₁₁OH/water systemA biocompatible surfactant—n-dodecylammoniumα-glutamate(GDA) with biodegradable and biocompatible properties was synthesized,and the phase behavior and the structural properties of GDA/n-pentanol/water system were studied by small-angle X-ray diffraction,electron spin resonance(ESR) and freeze-fracture transmission electron microscopy(FF-TEM).In the ternary phase diagram of GDA/n-pentanol/water system,there exist three isotropic regions—O/W,bicontinuous, and W/O structures,and two anisotropic regions—hexagonal liquid crystal(HEX) and lamellar liquid crystal(LLC) regions.UV-irradiation causes the decrease in the interlayer space,d,of lamellar liquid crystal and in the radius,r,of column aggregates of hexagonal liquid crystal,but it has little effect on the structure of O/W and W/O microemulsions.2.The interaction between n-dodecylammoniumα-glutamate(GDA) and hemoglobinThe interaction of hemoglobin with n-dodecylammonium a-glutamate(GDA) is studied by UV-vis spectrometer,the surface tension,isothermal titration microcalorimetry and the steady state fluorescence.The results of experiment show that GDA monomer can make the hemoglobin denatured,and when the concentration of GDA is higher than cmc,heme monomer releases from the hydrophobic cavity of hemoglobin.The TEM images elucidate hemoglobin molecules are aggregated and become much looser with the addition of GDA.The existence of proton in the above system can increase the stability of hemoglobin,while cation has no any effect.3.The interaction between n-dodecylammoniumα-glutamate(GDA) and bovine serum albumin(BSA)The effects of bovine serum albumin(BSA) on the cmc and the aggregation numbers (N) of GDA have been studied by the methods of the surface tension,isothermal titration microcalorimetry and the steady state fluorescence.Furthermore,the effects of GDA on the conformation properties of bovine serum albumin(BSA) are determined by circular dichroism spectroscopy,and TEM images.The results indicate that BSA can increase the cmc of GDA,whereas decrease the aggregation numbers(N).With the increase of the concentration of GDA,the secondary structure changes because of the interaction between BSA and GDA.4.The interaction of hemoglobin with GDA/n-C₅H₁₁OH/water assembliesWe studied the interaction between n-dodecylammoniumα-glutamate (GDA)/n-C₅H₁₁OH/H₂O assembly and methemoglobin by UV-vis spectrometer,X-ray diffractometer,electron spin resonance(ESR) spectrometer,rotational rheometer and freeze-fractured transmission electron microscopy(FF-TEM).It is found that W/O microemulsion forms at a lower n-pentanol content and O/W microemulsion forms at a lower water content with the addition of methemoglobin.The existence of methemoglobin reduces the hexagonal liquid crystal region,while the lamellar liquid crystal region is little changed in the presence of methemoglobin.Moreover,the methemoglobin and GDA/n-C₅H₁₁OH/H₂O assembly can affect each other's structure and properties and the changing behavior is dependent on the content of methemoglobin and the composition and structure of GDA/n-C₅H₁₁OH/H₂O system.The relationship among the changes in the structure and property of GDA/n-C₅H₁₁OH/H₂O assembly,the content of methemoglobin and the composition and structure of GDA/n-C₅H₁₁OH/H₂O assembly may provide some important theoretical information for elucidation of the interaction between methemoglobin and blood cell membrane and may be also helpful for the cure of some blood diseases.5.The self-organization properties of glutamic acid-based gemini surfactant(L₂G₂C_n)A series of glutamic acid-based surfactants have been synthesized from glutarnic acid. They have the same hydrophilic group and hydrophobic group,but the lengths of spacer groups are different.The critical micelle concentration(cmc) and the micelle aggregation number(N) were determined by surface tension measurement,fluorescence spectrum et.al..Experimental results indicate that the length of spacer of glutamic acid-based surfactants can affect on its aggregation behavior in the solution.The cmc and critical surface tension increase with the increase of length of spacer,while aggregation number decreases.In addition,glutamic acid-based surfactants are easy to form vesicles.The effect of surfactant concentration,salt concentration and the length of spacer on vesicle formation were also studied.6.The interaction between glutamic acid-based gemini surfactant(L₂G₂C_n) and hemoglobinThe interactions of hemoglobin with glutamic acid-based gemini surfactants have been studied with isothermal titration microcalorimetry,fluorescence spectroscopy,and circular dichroism.The results indicate that hemoglobin can increase the cmc of L2G2Cn surfactants and the circular dichroism spectra results show that the secondary structure of hemoglobin is possibly stabilized by a small amount of L₂G₂C_n.This result may be related to the double hydrophbic tails of L₂G₂C_n surfactants,which may generate the hydrophobic linkages between the nonpolar residues of hemoglobin.However,with the further addition of L₂G₂C_n,the secondary structure of hemoglobin was unfolded,and the percent of a helix in hemoglobin molecule was decreased.In addition,the L₂G₂C_n surfactant with longer spacer could reduce the denature degree of hemoglobin.