Berne L. Jones

Toxicity of purothionin and its homologues to the tobacco hornworm, Manduca sexta (L.) (lepidoptera: sphingidae)

Purothionin from wheat or homologues from barley and rye were injected into the hemocoel of larvae of Manduca sexta and caused 50% mortality at doses of 17–46 μg/g. Applications at 2–50 μg purothionin to a Manduca moth nerve-flight muscle preparation produced a rapid, dose-dependent depolarization of the muscle-fiber membrane. The α-isopeptides were two- to threefold more toxic than the β-forms. Alkylation of the cysteine residues of the peptides abolished both activities.

Purification of the insecticidal toxin from the parasporal crystal of Bacillus thuringiensis subsp. kurstaki.

Abstract The insecticidal toxin of Bacillus thuringiensis subsp. kurstaki was isolated from parasporal crystals. The toxin, which is stable for several months, is a glycoprotein with an apparent molecular weight of 68,000 that is generated upon solubilization and activation of a higher molecular weight protoxin (MWapp = 1.3 × 105) at alkaline pH. The toxin was purified by gel filtation and anion exchange chromatography and its molecular weight was established by gel filtration chromatography and SDS polyacrylamide gel electrophoresis.

Purification and Characterization of a New Class of Insect α-Amylase Inhibitors from Barley

ABSTRACT Barley seeds contain proteins that apparently protect them against attack by microorganisms and insects. Studies of these barley defensive proteins may lead to the development of barleys with improved natural resistance to pests. We have purified two low molecular weight proteins, designated BIα1 and BIα2, from barley grain, using ion-exchange chromatography and reversed-phase and gel-permeation high-performance liquid chromatography (HPLC). Both BIα1 and BIα2 inhibited insect (yellow meal worm, Tenebrio molitor) α-amylase activities. For the T. molitor α-amylase, the IC50 values of BIα1 and BIα2 were 80 μg/mL (12.5 μM) and 34 μg/mL (6.8 μM), respectively. Neither protein inhibited either human salivary α-amylase, barley α-amylase, or trypsin activities. N-terminal amino acid sequences of the inhibitors were highly homologous with those of the plant proteins called defensins. The first 20 N-terminal amino acids of BIα2 were identical to those of γ-hordothionin, but neither BIα1 nor BIα2 protein s...

Polymorphism of Aspartic Proteinases in Resting and Germinating Barley Seeds

ABSTRACT Both resting and germinated barley seeds (Hordeum vulgare L. ‘Morex’) contain aspartic endopeptidase activities, and the activities increase during germination. We have extracted and partially purified aspartic endopeptidases from both resting seeds and green malt (four-day germinated barley). Six aspartic proteinase activities were found in resting barley seeds while only four activities were detected in green malt. All of the aspartic proteinases had similar pH activity optima (pH 3.5–4.5) and pI values (≈4.5). The purified green malt aspartic proteinases selectively digested a group of barley seed proteins, postulated to serve as defensive proteins, that are coded by the amylase-trypsin inhibitor super gene family. The aspartic proteinases that bound to a pepstatin A affinity column at pH 4.5 cross-reacted with antiserum raised against aspartic proteinases purified from barley seed. However, those that did not bind the affinity column also did not cross-react with the antiserum, indicating tha...

Detecting Corn Syrup in Barley Malt Extracts

ABSTRACT Methods for detecting corn syrup in barley (Hordeum vulgare L.) malt extract were evaluated. Twelve samples representative of commercially available 2-rowed and 6-rowed malting barleys were malted. Extracts prepared from the finely ground malts were analyzed for 13C/12C ratios, expressed as δ13C, and concentrations of protein and sugars. The 13C/12C ratios were sufficiently different to distinguish corn syrup from malt extract. By calculating the mean values for the barleys, it was determined that a δ13C > -24.3‰ indicated that the malt extract had been adulterated with corn syrup (99% confidence). Protein concentrations <4.5% (2-rowed malt) or <5.0% (6-rowed malt) of the extracts also indicated probable adulteration with corn syrup, which is devoid of protein. Because of differences in sugar concentrations between the malt extracts and corn syrup, carbohydrate analysis also indicated probable mixtures. These findings were confirmed by analysis of extracts from composite 2-rowed and 6-rowed barle...