3 research outputs found
Surface characterization of human serum albumin and sodium perfluorooctanoate mixed solutions by pendant drop tensiometry and circular dichroism
The interfacial behavior of mixed human serum albumin (HSA)/sodium perfluorooctanoate (C8FONa) solutions is examined by using two experimental techniques, pendant drop tensiometry and circular dichroism spectroscopy. Through the analysis of the surface tension of the mixed solutions, surface competitive adsorption at the air-water interface between C8FONa and HSA is detected. The dynamic adsorption curves exhibit the distinct regimes in their time-dependent surface tension. The nature of these regimes is further analyzed in terms of the variation of the molecules surface areas. As a consequence, a compact and dense structure was formed where protein molecules were interconnected and overlapped. Thus, a reduction of the area occupied per molecule from 100 to 0.2 nm2 is interpreted as a gel-like structure at the surface. The presence of the surfactant seems to favor the formation of this interfacial structure. Finally, measurements of circular dichroism suggests a compaction of the protein due to the association with the surfactant given by an increase of α-helix structure in the complexes as compared to that of pure protein.Fil: Messina, Paula Verónica. Universidad de Santiago de Compostela; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Prieto, Gerardo. Universidad de Santiago de Compostela; EspañaFil: Dodero, Veronica Isabel. Universidad de Santiago de Compostela; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Cabrerizo-Vilchez, M.A.. Universidad de Granada. Facultad de Ciencias; EspañaFil: Maldonado Valderrama, J.. Universidad de Granada. Facultad de Ciencias; EspañaFil: Ruso, Juan M.. Universidad de Santiago de Compostela; EspañaFil: Sarmiento, Félix. Universidad de Santiago de Compostela; Españ
Modeling the Corrugation of the Three-Phase Contact Line Perpendicular to a Chemically Striped Substrate
We model an infinitely long liquid bridge confined between two plates
chemically patterned by stripes of same width and different contact angle,
where the three-phase contact line runs, on average, perpendicular to the
stripes. This allows us to study the corrugation of a contact line in the
absence of pinning. We find that, if the spacing between the plates is large
compared to the length scale of the surface patterning, the cosine of the
macroscopic contact angle corresponds to an average of cosines of the intrinsic
angles of the stripes, as predicted by the Cassie equation. If, however, the
spacing becomes of order the length scale of the pattern there is a sharp
crossover to a regime where the macroscopic contact angle varies between the
intrinsic contact angle of each stripe, as predicted by the local Young
equation. The results are obtained using two numerical methods, Lattice
Boltzmann (a diffuse interface approach) and Surface Evolver (a sharp interface
approach), thus giving a direct comparison of two popular numerical approaches
to calculating drop shapes when applied to a non-trivial contact line problem.
We find that the two methods give consistent results if we take into account a
line tension in the free energy. In the lattice Boltzmann approach, the line
tension arises from discretisation effects at the diffuse three phase contact
line.Comment: 17 pages, 6 figures, accepted for publication in Langmui