RH

The flow properties of sodium caseinate (NaCAS) film-forming dispersions were studied as a function of protein and glycerol concentration. Apparent viscosity vs. concentration profiles showed a disruption at about 10% (wt/wt) NaCAS. This was interpreted in terms of protein-water and protein-protein interactions. The presence of glycerol in the NaCAS film-forming suspensions reduced the viscosity of aqueous NaCAS as a consequence of decreasing protein-protein and protein-solvent interactions through the hydrogen bonding formation between the glycerol, the polypeptide chain of NaCAS, and water molecules. For higher concentration of glycerol, viscosity of NaCAS dispersions increased as a result of increasing total solid content. The glass transition temperature for solid films of 10% (wt/wt) NaCAS decreased with the glycerol content. The glycerol-protein interactions reduced the protein-protein interaction and, thus, increased the intermolecular spacing, leading to higher protein chain...

Using a spatially resolved sampling technique, the catalytic partial oxidation of CH4 to synthesis gas was investigated over 80 ppi α-Al2O3 foams coated with three catalytic formulations: 5 wt% Rh, 5 wt% Rh/2 wt% γ-Al2O3 washcoat and 5 wt% Rh–2 wt% Ce/2 wt% γ-Al2O3 washcoat. Experiments were performed at atmospheric pressure and ∼8 millisecond contact time, with 20% v/v CH4 and C/O ratio equal to 1. Data show that the length of the oxidative zone (∼2 mm) is unaffected by the composition of the catalyst. The addition of γ-Al2O3 washcoat to Rh coated monoliths allows the reaction to reach adiabatic equilibrium by increasing the rates of steam reforming and water gas shift. Additionally, both the maximum and the gradients in the temperature profiles decrease significantly with the addition of washcoat. Data collected on Rh–Ce/washcoat show that the adiabatic equilibrium composition is reached through a different kinetic route: the consumption of CH4 becomes slower, the production of CO2 exhibits a maximum, and the production of H2O is drastically moderated, suggesting that Ce has an active role in the CPO reaction kinetics. The features presented could be detected exclusively with spatially resolved measurements.

Integral membrane proteins are involved in virtually every cellular process. Precisely regulating these machineries would allow controlling many human and vertebrate diseases. Embedded into cellular membranes, membrane proteins establish molecular interactions that sensitively react to environmental changes and to molecular compounds, such as ligands or inhibitors. We applied atomic force microscopy (AFM) to image the Na+/H+ antiporter MjNhaP1 from Methanococcus jannaschii, and single-molecule force spectroscopy (SMFS) to probe molecular interactions that drive the protein structure-function relationship. High-resolution AFM topographs showed the dimeric assembly of MjNhaP1 being reconstituted into a lipid bilayer. SMFS of MjNhaP1 unraveled molecular interactions stabilizing individual structural domains. Transmembrane domains exhibited certain probabilities to unfold individually or cooperatively with other domains resulting in different unfolding pathways. Helices VIII and X established pH sensitive interactions altering significantly upon MjNhaP1 activation, while removal of the ligand (Na+) destabilized the entire antiporter except helix VIII. It is assumed that Asp234/235 of helix VIII are involved in the ligand-binding site and that helix X plays a functional role in the activation of the transporter.