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Boulange L.,Center Detudes Et Of Recherches | Sterczynskia F.,Center Detudes Et Of Recherches
Journal of Adhesion Science and Technology | Year: 2012

Our objectives were first to develop new physico-chemical methods to characterise the aggregate, the bitumen, and the bitumen emulsion surfaces, then to compare the properties of the new sustainable emulsifiers with those currently used in the road industry, and finally to explain the role of the bitumen/aggregate interactions in the bitumen emulsion breakdown. It was possible by using a Drop Shape Analysis System to determine the surface tension of complex liquids such as bitumen, surfactant containing aqueous phase, and bitumen emulsions. The interfacial phenomena between a bitumen emulsion and an aggregate are driven by the polar and dispersion interactions. The polar interactions play a major role in the emulsion adhesion to the aggregate and also in the emulsion breakdown. © 2012 Copyright Taylor and Francis Group, LLC. Source

Boulange L.,Center Detudes Et Of Recherches | Bonin E.,CPE Lyon | Saubot M.,Center Detudes Et Of Recherches
Road Materials and Pavement Design | Year: 2013

Our objective was to relate the fundamentals of bitumen-aggregate adhesion to practical engineering properties. The first step was dedicated to develop new physicochemical methods to characterise the bitumen-aggregate interface. Then, a relation was established between the physicochemical characterisations of the bitumen-aggregate interface and the water sensitivity of the asphalt. It was possible, by using the Drop Shape Analysis System, to apply the theory on the wetting of the textured surfaces distinguishing a one-scale roughness to a two-scale roughness on aggregate surfaces. Finally, a porosity effect corresponding to the smallest scale roughness leads to a better resistance to stripping phenomena. In addition, a chemical effect at the interface bitumen-aggregate, due to the addition of adhesion promoters in bitumen, improved the water sensitivity of the asphalt explained by an increase of the aromatics/resins ratio. © 2013 Copyright Taylor and Francis Group, LLC. Source

Ballet T.,Grenoble Institute of Technology | Ballet T.,Becton Dickinson | Brukert F.,Grenoble Institute of Technology | Mangiagalli P.,Becton Dickinson | And 6 more authors.
Biochemistry | Year: 2012

We have developed a multiwell-based protein aggregation assay to study the kinetics of insulin adsorption and aggregation on hydrophobic surfaces and to investigate the molecular mechanisms involved. Protein-surface interaction progresses in two phases: (1) a lag phase during which proteins adsorb and prefibrillar aggregates form on the material surface and (2) a growth phase during which amyloid fibers form and then are progressively released into solution. We studied the effect of three bacterial chaperones, DnaK, DnaJ, and ClpB, on insulin aggregation kinetics. In the presence of ATP, the simultaneous presence of DnaK, DnaJ, and ClpB allows good protection of insulin against aggregation. In the absence of ATP, DnaK alone is able to prevent insulin aggregation. Furthermore, DnaK binds to insulin adsorbed on hydrophobic surfaces. This process is slowed in the presence of ATP and can be enhanced by the cochaperone DnaJ. The peptide LVEALYL, derived from the insulin B chain, is known to promote fast aggregation in a concentration- and pH-dependent manner in solution. We show that it also shortens the lag phase for insulin aggregation on hydrophobic surfaces. As this peptide is also a known DnaK substrate, our data indicate that the peptide and the chaperone might compete for a common site during the process of insulin aggregation on hydrophobic surfaces. © 2012 American Chemical Society. Source

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