Abstract
Metalla-bis-dicarbollides, such as the COSAN anion [Co(C2B9H11)2]-, have attracted much attention in biology but a deep understanding of their interactions with cell-components is still missing. For this PhD work, we first studied the interactions of COSAN with glucose moiety, a neutral chemical function that is ubiquitous at biological interfaces. Octyl-glucopyranoside surfactant (C8G1) was chosen as a model as it self-assembles in water into micelles and creates a hydrated glucose-covered interface. Using complementary scattering and spectroscopic techniques, we have deduced from experiments that at low COSAN content and below the critical micellar concentration (CMC) of C8G1, COSAN binds to C8G1 monomers through the hydrophobic effect. Above the CMC of C8G1, COSAN adsorbs onto C8G1 micelles through the superchaotropic effect. At high COSAN concentrations, COSAN disrupts C8G1 micelles and the assemblies become similar to COSAN micelles but with small amount of solubilized C8G1. Therefore, COSAN binds in a versatile way to C8G1 upon either the hydrophobic or the superchoatropic effect depending on their relative concentrations. Then we extended this study to another type of interface, a compressed Langmuir monolayer containing glycolipids over a subphase containing various concentration of COSAN and also other types of nano-ions such as polyoxometalates. Varying the headgroup chemistry (one or two galactoside functions) and the alkyl chain saturation we observed different behaviour of nano-ion in interaction with the subsurface of the glycolipids and this as a function of the surface pressure. Using synchrotron techniques, we found superchaotrope nano-ions interact preferentially with species in gas or in the liquid expended phases than with the solid phase whose crystalline structure is not affected. Lower the charge density of the nano-ions and weaker the interaction between the sugar head groups, stronger is the interaction between the nano-ions and the glycolipids. Finally, in a last part, more complex interfaces were considered and investigated such as protein’s. Using electrophoretic methods, we observed some preferential interaction of COSAN with proteins characterized by various secondary structures, a research opening that will be explored for another PhD subject.