Localization of the Major Allergen Bet V 1 in Betula Pollen Using Monoclonal Antibody Labelling

The major allergen Bet ver 1 of Betula pendula (= B. verrucosa) pollen grains has been localized by gold labelling with monoclonal antibodies. The allergen is located predominantly in the starch grains and to a slight extent in the exine and intine. The possibility that environmental factors might influence the liberation of allergenic compounds present in birch pollen grains is discussed.     

Geographical variation in the spatial synchrony of a forest-defoliating insect: isolation of environmental and spatial drivers

Despite the pervasiveness of spatial synchrony of population fluctuations in virtually every taxon, it remains difficult to disentangle its underlying mechanisms, such as environmental perturbations and dispersal. We used multiple regression of distance matrices (MRMs) to statistically partition the importance of several factors potentially synchronizing the dynamics of the gypsy moth, an invasive species in North America, exhibiting outbreaks that are partially synchronized over long distances (approx. 900 km). The factors considered in the MRM were synchrony in weather conditions, spatial proximity and forest-type similarity. We found that the most likely driver of outbreak synchrony is synchronous precipitation. Proximity played no apparent role in influencing outbreak synchrony after accounting for precipitation, suggesting dispersal does not drive outbreak synchrony. Because a previous modelling study indicated weather might indirectly synchronize outbreaks through synchronization of oak masting and generalist predators that feed upon acorns, we also examined the influence of weather and proximity on synchrony of acorn production. As we found for outbreak synchrony, synchrony in oak masting increased with synchrony in precipitation, though it also increased with proximity. We conclude that precipitation could synchronize gypsy moth populations directly, as in a Moran effect, or indirectly, through effects on oak masting, generalist predators or diseases.     

Marked host specificity and lack of phylogeographic population structure of Campylobacter jejuni in wild birds

Zoonotic pathogens often infect several animal species, and gene flow among populations infecting different host species may affect the biological traits of the pathogen including host specificity, transmissibility and virulence. The bacterium Campylobacter jejuni is a widespread zoonotic multihost pathogen, which frequently causes gastroenteritis in humans. Poultry products are important transmission vehicles to humans, but the bacterium is common in other domestic and wild animals, particularly birds, which are a potential infection source. Population genetic studies of C. jejuni have mainly investigated isolates from humans and domestic animals, so to assess C. jejuni population structure more broadly and investigate host adaptation, 928 wild bird isolates from Europe and Australia were genotyped by multilocus sequencing and compared to the genotypes recovered from 1366 domestic animal and human isolates. Campylobacter jejuni populations from different wild bird species were distinct from each other and from those from domestic animals and humans, and the host species of wild bird was the major determinant of C. jejuni genotype, while geographic origin was of little importance. By comparison, C. jejuni differentiation was restricted between more phylogenetically diverse farm animals, indicating that domesticated animals may represent a novel niche for C. jejuni and thereby driving the evolution of those bacteria as they exploit this niche. Human disease is dominated by isolates from this novel domesticated animal niche.     

Heterometallic [AgFe3S4] ferredoxin variants: synthesis, characterization, and the first crystal structure of an engineered heterometallic iron–sulfur protein

Heterometallic [AgFe₃S₄] iron–sulfur clusters assembled in wild-type Pyrococcus furiosus ferredoxin and two variants, D14C and D14H, are characterized. The crystal structure of the [AgFe₃S₄] D14C variant shows that the silver(I) ion is indeed part of the cluster and is coordinated to the thiolate group of residue 14. Cyclic voltammetry shows one redox pair with a reduction potential of +220 mV versus the standard hydrogen electrode which is assigned to the [AgFe₃S₄]^2+/+ couple. The oxidized form of the [AgFe₃S₄] D14C variant is stable in the presence of dioxygen, whereas the oxidized forms of the [AgFe₃S₄] wild type and D14H variants convert to the [Fe₃S₄] ferredoxin form. The monovalent d ¹⁰ silver(I) ion stabilizes the [Fe₃S₄]^+/0 cluster fragment, as opposed to divalent d ¹⁰ metal ions, resulting in more than 0.4 V difference in reduction potentials between the silver(I) and, e.g., zinc(II) heterometallic [MFe₃S₄] ferredoxins. The trend in reduction potentials for the variants containing the [AgFe₃S₄] cluster is wild type ≤ D14C < D14H and shows the same trend as reported for the variants containing the [Fe₃S₄] cluster, but is different from the D14C < D14H < wild type trend reported for the [Fe₄S₄] ferredoxin. The similarity in the reduction potential trend for the variants containing the heterometallic [AgFe₃S₄] cluster and the [Fe₃S₄] cluster can be rationalized in terms of the electrostatic influence of the residue 14 side chains, rather than the dissociation constant of this residue, as is the case for [Fe₄S₄] ferredoxins. The trends in reduction potentials are in line with there being no electronic coupling between the silver(I) ion and the Fe₃S₄ fragment.     

Studies on Respiratory Enzymes in Rice Kernel

Rice embryo peroxidase 556 was purified to the extent as indicated by the absorbance ratio, RZ greater than 4.0. The enzyme was found to be major basic component among isoenzymes of rice embryo. The preparation was homogeneous as examined by sedimentation analysis, and the sedimentation coefficient, s°_20,w, was 3.76 S. The prosthetic group of the enzyme was identified as protohematin and its content was 1.36%. The minimum molecular weight was calculated to be 46,700. From the typical spectra of ligand-enzyme compounds, peroxidase 556 was found to react with carbon monoxide, cyanide, fluoride, and azide. However, at neutral pH, neither fluoride nor azide reacted with the enzyme. The high affinity of the enzyme to ammonia was one of the most remarkable characteristics of the enzyme. The hydrogen peroxide compounds I and II have been observed in the enzymic reaction, and therefore rice embryo peroxidase 556 is also concluded to follow the common reaction mechanism of plant peroxidases. Overall results show the close resemblance of rice embryo peroxidase 556 with wheat germ peroxidase 556 and hemoprotein 550.     

Isoenzymes of Japanese-radish Peroxidase

Japanese-radish root contained eighteen isoenzymes of peroxidase distinguishable on polyacrylamide gel electropherograms. The isoenzymes were found to be quite similar to those of horseradish peroxidase, although their quantities were different between two plants. The acidic components were the major isoenzyme in Japanese-radish peroxidase, while the neutral ones were the major one in horseradish. The chromatographic purification of the isoenzymes was performed on CM- and DEAE-Sephadex columns to characterize the components. The components in the preparations purified by the previously reported procedures of Morita et al. were also identified.     

Study on the Correlation of Chemical Structure and Ovicidal Activities of 2-Bromoethylthiobenzenes

Formation of a sulfonium-like intermediate was assumed in the hydrolysis of the 2-bromoethylthiobenzenes. A linear free energy relationship was found between the hydrolysis rate of a certain substituted 2-bromoethylthiobenzene and the molar fraction of water in the solvent. The effect of the substituent on the rate constant was attributed not only to the activation energy but also to the entropy change of activation. The negative ρ-value in the formation of the sulfonium-like intermediate in aqueous solution was comparable with that obtained in the ρ-σ-π analysis for ovicidal activity of the compounds.

For the reaction of the substituted 2-bromoethylthiobenzenes with highly excess amount of 4-(p-nitrobenzyl)-pyridine, the ρ-value was found to be negative, which means that the formation of the sulfonium-like intermediate is a rate determining step. Whichever might be more important, the hydrolysis or alkylation, as to the ovicidal action of the compounds, the formation of the sulfonium-like intermediate, could be considered to be an essential step.