Thermodynamic studies of the interaction of phosphatidylinositol phosphate with aminoglycosides antibiotics

In order to investigate the mechanism of the recognition of antibiotics with biomembrane, thermodynamic properties of the phosphoinositides (Pis) interacting with aminoglycoside antibiotics are studied by use of isothermal titration calorimetry. The results suggest different groups in the antibiotics have varied affinity with the Pis and neomycin B has higher affinity with phosphoinositides. PI binding to antibiotics becomes tighter as the concentration of antibiotics increase with more favorable entropy to yield a negative ΔG value, while antibiotics binding to PI become weaker with the increase of the PI concentration, and the enthalpy becomes more negative and the favorable entropic contributions are decreased. This means non-specific interactions, such as hydrogen bonds and van der Waals forces, are mainly involved the binding between antibiotics and Pis.