A mesh microcontactor for 2-phase reactions.

The design, fabrication and use of mesh microcontactor structures is described. These allow contact between immiscible fluid phases (liquid/liquid or gas/liquid) enabling mass transfer and reaction between and within the phases. The phases are not mixed and are removed separately for subsequent use or analysis. The structures were designed for kinetic studies on biphasic reactions with the ability to handle sequential samples without excessive sample dispersion. Mass transport conditions are defined by fluid layer depths of 100 microm and the volume for each phase contacting in the reaction region was selected at 100 microl as sufficient for a range of analytical techniques. Micromeshes with pore diameter, depth, and spacing each of approximately 5 microm were formed by electrodeposition of nickel onto substrates with defined photoresist layers, and released by etching a copper sub-layer. Reactor enclosures defining chambers on each side of the mesh were formed from milled glass and metal components. The assembled structures have been used in flow-through and static fluid modes. System function has been demonstrated for both liquid/liquid and gas/liquid reactions. Test chemistries selected for ease of optical monitoring were hydrolysis of colourless fluorescein diacetate in toluene with transfer as fluorescein anion to aqueous alkali, and oxygen absorption into aqueous alkaline pyrogallol solution generating a coloured product, purpurogallin.

Experimental results of a residential house fire test on tenability: temperature, smoke, and gas analyses.

A fire experiment conducted in a British 1950s-style house is described. Measurements of temperature, smoke, CO, CO2 , and O2 were taken in the Lounge, stairwell, and front and back bedrooms. The front bedroom door was wedged open, while the door to the back bedroom was wedged closed. Contrary to expectations and despite the relatively small fire load, analysis and hazard calculations show permeation of toxic fire gases throughout the property with lethal concentrations of effluent being measured at each sampling point. A generally poor state of repair and missing carpets in the upper story contributed to a high degree of gas and smoke permeation. The available egress time was calculated as the time before the main escape route became impassable. Given known human responses to fire, such an incident could have caused fatalities to sleeping or otherwise immobile occupants.

Expression and evolution of the mammalian brain gene Ttyh1.

Homologues of the Drosophila melanogaster tweety (tty) gene are present in mammals and Caenorhabditis elegans. The encoded proteins have five predicted membrane-spanning regions and recent findings suggest that some family members may be chloride channels. Phylogenetic analysis of the tty family including novel members from slime mould Entamoeba and plants has revealed the occurrence of independent gene duplication events in different lineages. expressed sequence tag data indicate that expression of the mammalian Ttyh1 gene is restricted mainly to neural tissue and is up-regulated in astrocytoma, glioma and several other cancers. In this study, mammalian expression vectors were used to investigate the subcellular localization and the effect of over-expression of Ttyh1 in human epithelial kidney cells. The results confirm that Ttyh1 is a membrane protein and show that it is deposited on the substratum along the migration paths of motile cells above the alpha5beta1-integrin complex. The ectopic expression of Ttyh1 also induced long filopodia, which were branched and dynamic in both stationary and migratory cells. The filopodia contained F-actin and occurred at the ends of microtubules which were polarized towards the membrane. Upon contact with nearby cells some filopodia stabilized and filled with F-actin, whereas Ttyh1 was highly concentrated at the cell-cell interface. Ttyh1 N- and C-terminal antipeptide antibodies detected Ttyh1 along the axons of neurones in primary rat hippocampal cell cultures, and in situ in whole rat brain slices around the hippocampus and occasionally between cells. These data suggest a role for Ttyh1 in process formation, cell adhesion and possibly as a transmembrane receptor.

Enzymological and physiological consequences of restructuring the lipoyl domain content of the pyruvate dehydrogenase complex of Escherichia coli.

The core-forming lipoate acetyltransferase (E2p) subunits of the pyruvate dehydrogenase (PDH) complex of Escherichia coli contain three tandemly repeated lipoyl domains although one lipoyl domain is apparently sufficient for full catalytic activity in vitro. Plasmids containing IPTG-inducible aceEF-IpdA operons which express multilip-PDH complexes bearing one N-terminal lipoyl domain and up to seven unlipoylated (mutant) domains per E2p chain, were constructed. Each plasmid restored the nutritional lesion of a strain lacking the PDH complex and expressed a sedimentable PDH complex, although the catalytic activities declined significantly as the number of unlipoylated domains increased above four per E2p chain. It was concluded that the extra domains protrude from the 24-meric E2p core without affecting assembly of the E1p and E3 subunits, and that the lipoyl cofactor bound to the outermost domain can participate successfully at each of the three types of active site in the assembled complex. Physiological studies with two series of isogenic strains expressing multilip-PDH complexes from modified chromosomal pdh operons (pdhR-aceEF-IpdA) showed that three lipoyl domains per E2p chain is optimal and that only the outermost domain need be lipoylated for optimal activity. It is concluded that the reason for retaining three lipoyl domains is to extend the reach of the outermost lipoyl cofactor rather than to provide extra cofactors for catalysis.