Proteoglycan-specific molecular switch for RPTPσ clustering and neuronal extension

Heparan and chondroitin sulfate proteoglycans (HSPGs and CSPGs, respectively) regulate numerous cell surface signaling events, with typically opposite effects on cell function. CSPGs inhibit nerve regeneration through receptor protein tyrosine phosphatase sigma (RPTPσ). Here we report that RPTPσ acts bimodally in sensory neuron extension, mediating CSPG inhibition and HSPG growth promotion. Crystallographic analyses of a shared HSPG-CSPG binding site reveal a conformational plasticity that can accommodate diverse glycosaminoglycans with comparable affinities. Heparan sulfate and analogs induced RPTPσ ectodomain oligomerization in solution, which was inhibited by chondroitin sulfate. RPTPσ and HSPGs colocalize in puncta on sensory neurons in culture, whereas CSPGs occupy the extracellular matrix. These results lead to a model where proteoglycans can exert opposing effects on neuronal extension by competing to control the oligomerization of a common receptor.     

Polar lightning and decadal-scale cloud variability on Jupiter

Although lightning has been seen on other planets, including Jupiter, polar lightning has been known only on Earth. Optical observations from the New Horizons spacecraft have identified lightning at high latitudes above Jupiter up to 80 degrees N and 74 degrees S. Lightning rates and optical powers were similar at each pole, and the mean optical flux is comparable to that at nonpolar latitudes, which is consistent with the notion that internal heat is the main driver of convection. Both near-infrared and ground-based 5-micrometer thermal imagery reveal that cloud cover has thinned substantially since the 2000 Cassini flyby, particularly in the turbulent wake of the Great Red Spot and in the southern half of the equatorial region, demonstrating that vertical dynamical processes are time-varying on seasonal scales at mid- and low latitudes on Jupiter.     

Effect of deamidation on stability for the collagen to gelatin transition

Deamidation of amide residues, Asn and Gln, in collagen occurs during the manufacture of B-type gelatin and could affect the performance of B-type gelatins as it may affect the refolding of triple-helical junctional domains that are formed during gelation. Host-guest peptides of the form acetyl-(Gly-Pro-Hyp)3-Gly-Xaa-Yaa-(Gly-Pro-Hyp)4-Gly-Gly-amide, where the X- and Y-positions of the guest peptide are varied, have been used to examine the effect of changing Asn to Asp and Gln to Glu on triple-helix stability. This paper reports the stability of host-guest peptides containing the guest triplets Gly-Ala-Asn, Gly-Asn-Ala, Gly-Asn-Lys, Gly-Gln-Ala, Gly-Glu-Glu, and Gly-Leu-Glu. In combination with previous data, these now provide 15 pairs of peptides in which the effect of deamidation can be compared. These comparisons show that the deamidation of Asn to Asp, regardless of whether it occurred in either the X- or Y-position, always gave a stabilizing effect; deamidation of Gln in the X-position also led to an increase in stability. In contrast, deamidation of Gln in the Y-position was quite distinct, leading to destabilization. The higher observed frequency of Gln in the Y-position compared with other amides may account for the slight destabilization of collagen following deamidation.     

Creaming in black tea

Tea cream is the precipitate formed as tea cools. Its formation has been studied by X-ray scattering, and it is shown that a higher tea concentration leads to earlier onset of creaming and larger particles and that addition of theaflavin and calcium promotes creaming. Association constants between the major components of black tea have been obtained using NMR and show that calcium and glucose enhance the self-association of caffeine, polyphenols, and theaflavin but have little effect on hetero-association. Glycosylation of a polyphenol reduced self-association and reduced binding to caffeine. We conclude that theaflavin is important for the initiation of creaming, forming nanoclusters of typically 3 nm diameter, whereas caffeine acts more to fill in the gaps within the clusters and thus adds to the bulk of tea cream without being necessary for its initiation. Tea creaming may be reduced by increasing the solubility of the polyphenols (i.e., by glycosylation) or by removing calcium. Tea cream; theaflavin; caffeine; small-angle X-ray scattering; NMR; colloid.     

Specificity of codling moth (Lepidoptera: Tortricidae) for the host plant kairomone, ethyl (2E,4Z)-2,4-decadienoate: field bioassays with pome fruit volatiles, analogue, and isomeric compounds

Codling moth, Cydia pomonella (L.), is a severe pest of apples, pears, and walnuts worldwide, and new approaches for precise monitoring and management would be beneficial. Ninety-two pome fruit volatiles were formulated in 23 distinct blends, of which a single 4-component blend of 10-carbon esters showed the only significant attraction of moths in field bioassays conducted in both walnut and apple orchards. A single constituent of this blend, ethyl (2E,4Z)-2,4-decadienoate--the "pear ester", was the major contributing attractant. The pear ester attracted both male and female moths in combined numbers that were comparable to the attractiveness of conspecific sex pheromone. Structure-activity tests were conducted in a series of orchard trials to determine the specificity of attraction of codling moths to the pear ester kairomone. No analogue 10-carbon alcohols, aldehydes, acetates, or other esters elicited significant moth capture responses. Tests with various analogue esters with alcohol chain length moiety substitutions of the (2E,4Z)-2,4-decadienoic acid elicited differential capture responses, with the ethyl exceeding the propyl, methyl, butyl, and hexyl analogues. The (E,Z) geometric isomers of this series of (2E,4Z)-2,4-decadienoic acid esters far exceeded the attractiveness of the (E,E) isomers. The pear ester is a potent attractant of both males and females, and codling moths are highly discriminating and specific in their structure-activity-based attraction to this pear-derived kairomone. These specificity attributes should allow this host plant kairomone to contribute to new abilities for female monitoring and the potential of development of novel and highly selective control practices that should decrease the current dependence on the use of broad-spectrum insecticides.     

Fertilization and Bioaugmentation for Oil Biodegradation in Salt Marsh Mesocosms

Biodegradation of crude oil is often dependent on the population sizes and metabolic activity of hydrocarbon-degrading microorganisms in addition to nutrient supply. Fertilization with N and P and bioaugmentation of oil-contaminated soil with hydrocarbon-degrading microorganisms may serve to enhance oil biodegradation rates. Glasshouse experiments were conducted to determine the impacts of fertilization and commercial bioremediation products on crude oil biodegradation and on changes in nutrient concentrations and populations of hydrocarbon-degrading microorganisms in salt marsh mesocosms growing Spartina alterniflora. Experiments were conducted under continuously-flooded and alternately-flooded/drained conditions with and without N and P fertilization. MaxBac, a slow-release fertilizer, was applied at a rate of 100 kg N ha^-1 and 20 kg P ha^-1, while additional P was applied at 20 kg P ha^-1. Commercial products failed to enhance total oil or total petroleum hydrocarbon (TPH) degradation under either continuously or alternately-flooded conditions. An average of 62% of TPH was degraded by 33 d under continuously-flooded conditions, while 59% was degraded by 41 d after oil application under alternately-flooded conditions. Products generally did not increase population sizes of heterotrophs orhydrocarbon-degrading microorganisms. Concentrations of NH₄ ⁺ and P decreased during experimentation, and fertilization with N and P stimulated total oil and TPH degradation under continuously-flooded, but not under alternately-flooded conditions.     

The biochemical mechanisms of resistance to insecticides with especial reference to the housefly,Musca domestica and aphid,Myzus persicae

The mechanisms by which insects chemically modify and thereby resist insecticides, and the techniques used to study this metabolism arc described. The enzymes associated with the endoplasmic reticulum of the cell (the microsomal enzymes) play a major and ubiquitous role in this metabolism which can produce molecules either more or less toxic than the insecticide applied. “Soluble” enzymes in the cytoplasm of the cell also metabolise insecticides, and it is the balance between these types of metabolism and such factors as the rate of penetration of the insecticide and the susceptibility of the target which determines the tolerance of an insect to a particular insecticide. A very small change in one of these factors can cause a large change in the dose of insecticide required to kill an insect.