Single-molecule kinetics of pore assembly by the membrane attack complex

The membrane attack complex (MAC) is a hetero-oligomeric protein assembly that kills pathogens by perforating their cell envelopes. The MAC is formed by sequential assembly of soluble complement proteins C5b, C6, C7, C8 and C9, but little is known about the rate-limiting steps in this process. Here, we use rapid atomic force microscopy (AFM) imaging to show that MAC proteins oligomerize within the membrane, unlike structurally homologous bacterial pore-forming toxins. C5b-7 interacts with the lipid bilayer prior to recruiting C8. We discover that incorporation of the first C9 is the kinetic bottleneck of MAC formation, after which rapid C9 oligomerization completes the pore. This defines the kinetic basis for MAC assembly and provides insight into how human cells are protected from bystander damage by the cell surface receptor CD59, which is offered a maximum temporal window to halt the assembly at the point of C9 insertion

Effect of Larvae Treated with Mixed Biopesticide Bacillus thuringiensis - Abamectin on Sex Pheromone Communication System in Cotton Bollworm, Helicoverpa armigera

Third instar larvae of the cotton bollworm (Helicoverpa armigera) were reared with artificial diet containing a Bacillus thuringiensis - abamectin (BtA) biopesticide mixture that resulted in 20% mortality (LD(20)). The adult male survivors from larvae treated with BtA exhibited a higher percentage of “orientation” than control males but lower percentages of “approaching” and “landing” in wind tunnel bioassays. Adult female survivors from larvae treated with BtA produced higher sex pheromone titers and displayed a lower calling percentage than control females. The ratio of Z-11-hexadecenal (Z11–16:Ald) and Z-9-hexadecenal (Z9–16:Ald) in BtA-treated females changed and coefficients of variation (CV) of Z11–16:Ald and Z9–16:Ald were expanded compared to control females. The peak circadian calling time of BtA-treated females occurred later than that of control females. In mating choice experiment, both control males and BtA-treated males preferred to mate with control females and a portion of the Bt-A treated males did not mate whereas all control males did. Our Data support that treatment of larvae with BtA had an effect on the sex pheromone communication system in surviving H.armigera moths that may contribute to assortative mating

An Investigation of the Kinetics and Oxidative Thermodegradation Properties of Waste Telephone Pole Samples Treated with Metal Salts

In the present study, combustion mechanisms, activation energy, and exponential constants were investigated for natural pine and acid copper chromate impregnated telephone pole. Oxidative thermodegradation was carried out in air environment at different heating rates by using thermogravimetric analysis. In order to calculate thermal kinetics, the Coats Redfern method was used. There were less flammable products, lower weight losses in the main oxidation region, a decrease in the maximum weight loss temperatures, and more char formation for treated samples as compared to untreated samples. In other words, due to treatment of wood with acid copper chromate, thermal properties of wood changed

Catalytic synthesis of boron nitride nanotubes at low temperatures

KFeO2 is demonstrated for efficiency catalysing the formation of BN nanotubes (BNNT) by thermal chemical vapor deposition (TCVD). This alkali-based catalyst enables the formation of crystalline and high aspect ratio, multi-walled BNNTs at temperatures as low as 750°C, significantly lower than those typical of production by TCVD

Kinetics of hydrogenation of furfural to furfuryl alcohol over copper chromite catalyst and optimum regeneration procedures

The deactivation mechanism of a copper chromite catalyst, used in selective hydrogenation of furfural to furfuryl alcohol, was investigated and the methods to regenerate it were searched. The catalyst deactivation mechanisms was found to be due to the fouling resin macromolecules, formed by side reactions of furfural on the catalyst surface. The optimum catalyst regeneration was by one drying at 110 degrees C for 5 days, heating at 325 degrees C for 18 hours followed by refluxing in cyclohexanol for 4 hours. The conversion to furfuryl alcohol by the regenerated sample in vapor phase hydrogenation was 78 per cent, compared to 79.5 per cent for the fresh catalyst