Formation and stability of nanofibers from a milk-derived peptide

The objective of the present work was to investigate the physicochemical conditions that trigger the self-assembly of peptide β-lg f1-8 and therefore lead to nanofibers and hydrogel formation. Nanostructures formed by self-assembly of peptide β-lg f1-8 in the pH range of 2.0-11.0 were studied by transmission electron microscopy (TEM). Hydrogel formation was studied as a function of pH and resulted in evidence of a link between hydrogel formation and the charge distribution carried by the peptide structure. Finally, circular dichroism (CD) spectroscopy was used to characterize the effects of peptide concentration (0.4-2.0 mg/mL), ionic strength (0-1 M NaCl), and temperature (20-80 °C) on the secondary structure of peptide β-lg f1-8. Hydrogels were obtained at peptide concentrations above 2.5 mg/mL. Peptide concentration and pH adjustment were shown to trigger self-assembly of β-lg f1-8, but increasing ionic strength had no effect. Heating to 80 °C induced a stronger CD signal intensity due to an increase in solubility of the peptide, whereas only slight changes in CD pattern were found upon cooling to 20 °C. Overall, results emphasize the role of particular molecular interactions in β-sheet self-assembly of peptide β-lg f1-8 and pH-dependent electrostatic interactions occurring between β-lg f1-8 units, which can explain its propensity to self-assembly.     

Physical and genomic characteristics identify chicken proventricular necrosis virus (R11/3 virus) as a novel birnavirus

Chicken proventricular necrosis virus (CPNV), isolate R11/3, previously was isolated from transmissible viral proventriculitis-affected chickens and was determined to be the likely etiology of this disease. CPNV was identified as a birnavirus on the basis of virion size and morphology (icosahedral, approximately 75 nm in diameter, nonenveloped); buoyant density in cesium chloride (1.32 g/ml); a genome comprising bisegmented, double-stranded RNA (approximately 3.8 and 3.4 kilobase pairs); and nucleotide sequence analyses. Nucleotide sequencing of CPNV RNA, segment B, identified a single large open reading frame that encodes a 903-amino acid protein. The 903-amino acid protein was identified as the putative VP1, the viral RNA-dependent RNA polymerase (RdRp), on the basis of sequence homologies with other birnavirus VP1 proteins. The CPNV VP1 possessed the unique permuted RdRp sequence motif arrangement characteristic of birnaviruses; however, phylogenetic analyses based on VP1 demonstrated that CPNV is deeply divergent from other birnaviruses.     

Bombus terrestris as pollinator‐and‐vector to suppress Botrytis cinerea in greenhouse strawberry

BACKGROUND: Bombus terrestris L. bumblebees are widely used as commercial pollinators, but they might also be of help in the battle against economically important crop diseases. This alternative control strategy is referred to as pollinator‐and‐vector technology. The present study was designed to investigate the capacity of B. terrestris to fulfil this role in greenhouse strawberry flowers, which were manually inoculated with a major plant pathogen, the grey mould Botrytis cinerea Pers.: Fr. A model microbiological control agent (MCA) product Prestop‐Mix was loaded in a newly developed two‐way bumblebee dispenser, and, in addition, the use of the diluent Maizena‐Plus (corn starch) was tested. RESULTS: Importantly, loading of the MCA caused no adverse effects on bumblebee workers, with no loss of survival or impairment of flight activity of the workers during the 4 week flowering period. Secondly, vectoring of Prestop‐Mix by bumblebees resulted in a higher crop production, as 71% of the flowers developed into healthy red strawberries at picking (preharvest yield) as compared with 54% in the controls. In addition, these strawberries were better protected, as 79% of the picked berries remained free of B. cinerea after a 2 day incubation (post‐harvest yield), while this percentage was only 43% in the control. Overall, the total yield (preharvest × post‐harvest) was 2–2.5 times higher than the total yield in the controls (24%) in plants exposed to bumblebees vectoring Prestop‐Mix. Thirdly, the addition of the diluent Maizena‐Plus to Prestop‐Mix at 1:1 (w/w) resulted in a similar yield to that of Prestop‐Mix used alone, and in no negative effects on the bumblebees, flowers and berries. CONCLUSIONS: This greenhouse study provides strong evidence that B. terrestris bumblebees can vector a MCA to reduce B. cinerea incidence in greenhouse strawberries, resulting in higher yields. Similar yields obtained in the treatments with Prestop‐Mix and Prestop‐Mix + Maizena‐Plus suggest an equally efficient dissemination of the biocontrol agent into the flowers with only half the initial concentration of Prestop‐Mix, which illustrates the importance of the diluent. Copyright © 2011 Society of Chemical Industry