The Discussion About Two Mathematical Models To Measure The Parameters About The Formation Of Binary Complexes In The Langmuir Monolayer Film And The Experiment Research On The Interaction Between Archaeal Lipids And The Proteins

In this paper, there are two research topics. The first one is that a new method to measure the parameters about the formation of binary complexes in the Langmuir monolayer film was developed. Some important parameters such as the stability constant, the mean molecular areas of binary complexes and unpolymerized molecules, the proportion of molecules which have formed complexes and so on can be got, through which a function about the relationship between the proportion of the amount of the molecules which had polymerized to the total amount of the molecules in the Langmuir monolayer and the ratio of the amounts of two different components was derived for the first time. Dipalmitoylphosphatidylcholine (DPPC) and Stearic acid (SA) were selected as materials to make Langmuir films to validate the new method. Following results were got:mean molecular areas of SA and DPPC are24.0A2molecule-1and63.7A2molecule-1separately, the mean molecular area of dimers is81.3A2molecule-1, the stability constant at room temperature is1.86×107m2/mol, and the proportion of the molecules which have formed complexes reaches its highest value-about84.96%of the total molecules in the Langmuir monolayer have polymerized when the proportion of the amount of SA is49.73%.The second research topic is about the different characters of an archaeal phosphatidyl choline1,2-di-O-phytanyl-sn-glycero-3-phosphocholine (4ME16:0Diether PC), which is the analogue of one kind of membrane lipid of archaeon, and dipalmitoyl-sn-glycero-3-phosphocholine(DPPC), which is one kind of membrane lipid of eukaryotes, when they interact with Gramicidin A (gA), which is a hydrophobic linear polypeptide, in the monolayers. The experimental temperature is room temperature and the subphase is aqueous sodium chloride solution with0.9%mass concentration. The π-A isotherm and A-T isotherm were measured. It was found that both the Langmuir monolayers consisting of DPPC or4ME16:0Diether PC are really steady. The stability of mixed Langmuir monolayers consisting of gA and DPPC or4ME16:0Diether PC is also been studied and the result shows that the mixed Langmuir monolayers consisting of gA and DPPC is still stable but the mixed Langmuir monolayer consisting of gA and4ME16:0Diether PC is unstable. At last, Atomic Force Microscope was used to study the effect of gA on the topography of LB monolayer of DPPC or4ME16:0Diether PC and the adsorption of gA to the LB monolayer of DPPC or4ME16:0Diether PC. It was found that the mixed LB monolayers consisting of gA and4ME16:0Diether PC are defective on the topography and the pattern of aggregation was found on the mixed LB monolayer consisting of gA and DPPC, which may imply gA molecules can insert the monolayer of DPPC and integrate with the DPPC molecules compactly but the gA molecules can’t integrate with4ME16:0Diether PC molecules compactly. In addition, it was found that the gA Langmuir monolayer can be adsorbed on the LB monolayer of DPPC but it can’t be adsorbed on the LB monolayer of4ME16:0Diether PC. All above experiments can illuminate that gA can easily combine with DPPC but rather than4ME16:0Diether PC, which may imply the gA has more strong damage effect on the cell membrance of eukaryotes than on the cell membrance of archaeon.