The Interaction Between Amino Acids, Salts Ions And Biological Membrane Revealed By Sum Frequency Generation

The interactions between protein, salt ions and biological membrane play a key role in a series of physiological processes in the body. The amino acids are the building blocks of protein, which determine the structure and function of protein. A better understanding of the interaction between amino acids and biological membrane helps us to further clarify behaviors mechanism of protein. In this study, sum frequency generation vibrational spectroscopy has been applied to characterize the interaction of binary system between positively charged amino acids, potassium salts and biological membrane supplemented by π-A isotherm compression curve and imaging of Brewster angle microscopy (BAM), and the interaction of ternary system has also been investigated using sum frequency generation vibrational spectroscopy. It is found that both positively amino acids and potassium salts could interact with lipid membrane by analyzing π-A isotherm compression curve and Brewster angle microscopy images of lipid monolayer. The binding strength has an order: arginine>lysine, PBS>KI>KF. According to dynamic spectra changes of CD, PO2-and C=O region during the process of interaction between positively charged amino acids, potassium salts and negatively charged lipid bilayer, we can make some conclusions that both positively charged amino acids and potassium salts can interact with negatively charged lipid bialyer, and perturb the conformation of lipid bilayer. The membrane surface electric property and water dipole phase remain unchanged when positively charged amino acids and KI bind to lipid bilayer, while they change for PBS and KF. Only K+binds to the phosphate and carbonyl group close to the lipid head for PBS and KF, yet both K+and I-bind to the phosphate and carbonyl group for KI. For the positive charged amino acids, arginine interact with the phosphate and carbonyl group at the same time, however, lysine only bind to the phosphate group. The strength order of interaction between positively charged amino acids, potassium salts and negatively charged lipid bilayer is the same as lipid monolayer. We are able to describe a clear and complete picture of interaction between positively charged amino acids, potassium salts and negatively charged lipid membrane based on our result. In addition, on the basis of the study of ternary system, we found that potassium salts don’t promote the interaction between positively charged amino acids and negatively charged lipid bilayer. Results from this study will provide some new ideas for cell membrane fusion, cell regulation, design of new type drug transporter and the treatment of related diseases.