Three separable domains regulate GTP-dependent association of H-ras with the plasma membrane

The microlocalization of Ras proteins to different microdomains of the plasma membrane is critical for signaling specificity. Here we examine the complex membrane interactions of H-ras with a combination of FRAP on live cells to measure membrane affinity and electron microscopy of intact plasma membrane sheets to spatially map microdomains. We show that three separable forces operate on H-ras at the plasma membrane. The lipid anchor, comprising a processed CAAX motif and two palmitic acid residues, generates one attractive force that provides a high-affinity interaction with lipid rafts. The adjacent hypervariable linker domain provides a second attractive force but for nonraft plasma membrane microdomains. Operating against the attractive interaction of the lipid anchor for lipid rafts is a repulsive force generated by the N-terminal catalytic domain that increases when H-ras is GTP loaded. These observations lead directly to a novel mechanism that explains how H-ras lateral segregation is regulated by activation state: GTP loading decreases H-ras affinity for lipid rafts and allows the hypervariable linker domain to target to nonraft microdomains, the primary site of H-ras signaling.

Silica membrane reactors for hydrogen production from water gas shift

This paper presents an analysis of membrane reactor (MR) operation and design for enhanced hydrogen production from the water gas shift (WGS) reaction. It has been established that membrane reactors can enhance an equilibrium limited reaction through product separation. However, the detailed effects of reactor setup, membrane configuration and catalyst volume have yet to be properly analysed for this reaction. This paper investigates new ideas for membrane reactors such as the development of new catalytic films, for improved interaction between the reaction and separation zones. Current membrane reactors utilise a packed bed of catalyst within the membrane tube, utilising a large volume of catalyst to drive reaction. This is still inefficient and provides only limited benefits over conventional WGS reactors. New reactor configurations look to optimise the interactive effects between reaction and separation to provide improved operation. In this paper, thin film catalysts were produced using dip coating and spray coating techniques. This technique produced catalyst coatings with good thickness, though the abrasion strength of the dip coated catalyst was quite low. The catalyst was tested in a packed bed reactor for temperature activity at low temperatures and catalyst activity at varying levels of excess water