The Interacton Study Between Palmitic Acid And Lipid Molecule As Well As Bovine Insulin

The study of the structure and function of biomembrane has become one of the most interesting hot fields in the molecular biology and biological medicine in recent years. It was reported that the occurrence of a variety of diseases affiliated with the induction of palmitic acid and the resistance of insulin. So the study of interaction between palmitic acid and lipid as well as bovine insulin has been become the core and key points of research of occurrence and development rule of a variety of diseases. The research has an important biological significance and reference value for understanding and treating the diseases which were correlated with the induction of palmitic acid and the resistance of insulin. The best method was lipid monolayer technology (that is, the Langmuir-Blodgett (LB) membrane technology) for the study of the interaction between palmitic acid and lipid as well as bovine insulin. In this paper, it was simulated study the interactions between palmitic acid with lipid molecules as well as bovine insulin in Langmuir monolayer.The two aspects were mainly studied as follow in this paper.(1)The physicochemical property and AFM study of the interaction of palmitic acid with DPPE in Langmuir monolayer. In this paper, the thermodynamic characteristic and morphology feature of the binary mixed PA/DPPE monolayer spreading on the water of pH6.2and3have been investigated by the combination Langmuir technique with AFM. The LB technique was used to prepare the PA/DPPE mixed monolayer. The π-A isotherm of mixed monolayer was obtained in two kinds of subphase. The excess molecular area, excess Gibbs energy, interaction parameter and activity coefficient and so on which were calculated based on the π-A isotherm. The miscibility, stability and structure characteristics as well as molecular mechanism of the PA/DPPE mixed monolayer were discussed. The surface morphology of PA/DPPE mixed monolayer was observed by using AFM. The two dimensional molecular arrangement model diagrams were showed. The results showed that:①The π-A isotherm of mixed monolayer regularly arranged between the two kinds of pure components as the adding of the mole fraction of PA in two kinds of subphase.②The mean molecular area of mixed monolayer decreased with the increment of XPA and surface pressures in the two kinds of subphase.③The excessive molecular area obtained maximum value for XpA=0.7with suphase pH6.2and for XPA=0.5with suphase pH3. It means that the intermolecular interactions between PA and DPPE strengthen and intermolecular repulsive forces enlarge with the increasing of mole fraction of PA.④As the surface pressure increasing, the values of△Gex and interaction parameter became larger and showed changes regularly at subphase pH of6.2and3, but the maximums value of AGex showed different, namely:the maximum at XPA=0.7and XPA=0.5. It could be concluded that incorporating PA into the DPPE monolayer caused a significant influence to the monolayer stability and intermolecular interaction.⑤The coefficient f1showed an opposite trend at subphase pH3corresponding with the coefficient f1at subphase pH6.2. However, coefficient f1showed a similar trend at subphase pH3corresponding with the coefficient f1at subphase pH6.2.⑥The surface morphology of different proportion mixed monolayer was observed in two pH subphase condition. The results showed that the some degree of aggregation appeared in different proportion of mixed monolayer under two pH subphase condition. Comparing with the pH6.2subphase condition, the defects in pure and mixed components monolayer increased and the change trend of the surface roughness of mixed monolayer has changed under pH3subphase condition.(2) The interaction between bovine insulin with DPPC as well as palmitic acid in monolayer. The DPPC and PA were used to investigate its affecting the surface phase behavior, stability and adsorption characteristic as well as compressibility to INS monolayer. The π-A isotherms, π-T curves and AFM have been applied to characterize the surface behaviors and morphologies of INS monolayer, INS/DPPC and INS/PA mixed monolayer. It was found that:①The behavior and lateral assembling of mixed monolayer depended on the interaction between polar head groups of lipid, hydrophobic tail chains and lipid molecules with INS.②The INS/DPPC mixed monolayer was more stable than INS/PA mixed system in100mins.③INS adsorbing to monolayer strongly depended on the composition and packing density of mononlayer.④The surface morphologies of INS. DPPC. PA and INS/DPPC as well as INS/PA were observed by AFM. The PA molecules in monolayer were more easily to induce INS molecules to aggregate in high surface pressure.⑤The surface morphologies of INS monolayer which were under different pH condition (pH=2,5.3and10) were also observed. It was found that the aggregation of INS molecules was induced by the presence of lipid molecules in the monolayer or by nonspecific interaction with hydrophobic environment.