Identification and preliminary evaluation of viriditoxin, a metabolite of Paecilomyces varioti, as an insecticide for sheep blowfly, Lucilia cuprina (Wied.)

Solvent extracts of cultures of the fungus Paecilomyces varioti are toxic to sheep blowfly, Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae). Different components of the culture extracts were isolated and bioassayed with L. cuprina. The component with most toxicity was purified and identified from its proton magnetic resonance spectrum as viriditoxin, a known antibiotic metabolite of the fungus. The insecticidal properties of viriditoxin were then evaluated. Mean LCso values for first instar larvae of organophosphate susceptible and resistant strains of L. cuprina were 7.5 and 8.4 ppm respectively. Pilot implant trials in sheep demonstrated that the compound provided protection for 9-17 weeks against both strains of L. cuprina. No adverse effects on the trial sheep were detected.

Chemical synthesis and structure elucidation of bovine K-casein (1-44)

The caseins (αs1, αs2, β, and κ) are phosphoproteins present in bovine milk that have been studied for over a century and whose structures remain obscure. Here we describe the chemical synthesis and structure elucidation of the N-terminal segment (1–44) of bovine κ-casein, the protein which maintains the micellar structure of the caseins. κ-Casein (1–44) was synthesised by highly optimised Boc solid-phase peptide chemistry and characterised by mass spectrometry. Structure elucidation was carried out by circular dichroism and nuclear magnetic resonance spectroscopy. CD analysis demonstrated that the segment was ill defined in aqueous medium but in 30% trifluoroethanol it exhibited considerable helical structure. Further, NMR analysis showed the presence of a helical segment containing 26 residues which extends from Pro8 to Arg34. This is the first report which demonstrates extensive secondary structure within the casein class of proteins.