Characterization of ß-lactoglobulin adsorption on silica membrane pore surfaces and its impact on membrane emulsification processes.

Protein adsorption plays a key role in membrane fouling in liquid processing, but the specific underlying molecular mechanisms of ß-lactoglobulin adsorption on ceramic silica surfaces in premix membrane emulsification have not been investigated yet. In this study, we aimed to elucidate the ß-lactoglobulin adsorption and its effect on the premix membrane emulsification of ß-lactoglobulin-stabilized oil-in-water emulsions. In particular, the conformation, molecular interactions, layer thickness, surface energy of the adsorbed ß-lactoglobulin and resulting droplet size distribution are investigated in relation to the solvent properties (aggregation state of ß-lactoglobulin) and the treatment of the silica surface (hydrophilization). The ß-lactoglobulin adsorption is driven by attractive electrostatic interactions between positively charged amino acid residues, i.e., lysin and negatively charged silanol groups, and is stabilized by hydrophobic interactions. The strong negative charges of the treated silica surfaces result in a high apparent layer thickness of ß-lactoglobulin. Although the conformation of the adsorbed ß-lactoglobulin layer varies with membrane treatment and the solvent properties, the ß-lactoglobulin adsorption offsets the effect of hydrophilization of the membrane so that the surface energies after ß-lactoglobulin adsorption are comparable. The resulting droplet size distribution of oil-in-water emulsions produced by premix membrane emulsification are similar for treated and untreated silica surfaces.

Spin in organics: a new route to spintronics.

New developments in the nascent field of organic spintronics are discussed. Two classes of phenomena can be discerned. In hybrid organic spin valves (OSVs), an organic semiconducting film is sandwiched between two ferromagnetic (FM) thin films, aiming at magnetoresistive effects as a function of the relative alignment of the respective magnetization directions. Alternatively, organic magnetoresistance (OMAR) is achieved without any FM components, and is an intrinsic property of the organic semiconductor material. Some of the exciting characteristics of OMAR, in both electrical conductance and photoconductance, are presented. A systematic, combined experimental-theoretical study of sign changes between positive and negative magnetoresistance is shown to provide important insight about the underlying mechanisms of OMAR. A simple explanation of experimental observations is obtained by combining a 'spin-blocking' mechanism, an essential ingredient in the recently proposed bipolaron model, with specific features of the device physics of space charge limited current devices in the bipolar regime. Finally, we discuss possible links between the physics relevant for OMAR and that for OSVs. More specifically, weak hyperfine fields from the hydrogen atoms in organic materials are thought to be crucial for a proper understanding of both types of phenomena.