Isolation and characterization of a flocculating protein from Moringa oleifera Lam.

A flocculating protein from the seeds of Moringa oleifera Lam. was isolated by extraction with phosphate buffer followed by cation exchange chromatography. The molecular mass of the protein determined by SDS-PAGE was about 6.5 kDa, the isoelectric point was above pH 10. Amino acid analysis and sequencing showed high contents of glutamine, arginine and proline, and a total of 60 residues. The amino terminus is blocked by pyroglutamate. The flocculant capacity, determined in glass powder suspension, is comparable to that of a cationic polymer on polyacrylamide basis. Flocculation activity may be explained by the patch charge mechanism due to low molecular weight and high charge density.

Some physico-chemical parameters that influence proteinase K resistance and the infectivity of PrPSc after high pressure treatment.

Crude brain homogenates of terminally diseased hamsters infected with the 263 K strain of scrapie (PrP Sc) were heated and/or pressurized at 800 MPa at 60 degrees C for different times (a few seconds or 5, 30, 120 min) in phosphate-buffered saline (PBS) of different pH and concentration. Prion proteins were analyzed on immunoblots for their proteinase K (PK) resistance, and in hamster bioassays for their infectivity. Samples pressurized under initially neutral conditions and containing native PrP Sc were negative on immunoblots after PK treatment, and a 6-7 log reduction of infectious units per gram was found when the samples were pressurized in PBS of pH 7.4 for 2 h. A pressure-induced change in the protein conformation of native PrP Sc may lead to less PK resistant and less infectious prions. However, opposite results were obtained after pressurizing native infectious prions at slightly acidic pH and in PBS of higher concentration. In this case an extensive fraction of native PrP Sc remained PK resistant after pressure treatment, indicating a protective effect possibly due to induced aggregation of prion proteins in such buffers.

Pasteurization of food by hydrostatic high pressure: chemical aspects.

Food pasteurized by hydrostatic high pressure have already been marketed in Japan. There is great interest in this method also in Europe and USA. Temperature and pressure are the essential parameters influencing the state of substances including foods. While the influence of temperature on food has been extensively investigated, effects of pressure, also in combination with temperature, are attracting increasing scientific attention now. Processes and reactions in food governed by Le Chatelier's principle are of special interest; they include chemical reactions of both low- and macromolecular compounds. Theoretical fundamentals and examples of pressure affected reactions are presented.

Constituents of Justicia pectoralis Jacq. 2. Gas chromatography/mass spectrometry of simple coumarins, 3-phenylpropionic acids and their hydroxy and methoxy derivatives.

The analysis of extracts from the South American plant Justicia pectoralis Jacq. permitted the identification, among other compounds, of coumarin, dihydrocoumarin, umbelliferone and 3-(2-hydroxyphenyl)propionic acid by gas chromatography/mass spectrometry (GC/MS); the acids and phenolic compounds were derivatized with diazomethane. GC/MS of simple coumarins, phenylpropionic acids and their hydroxylated isomers was performed after derivatization through methylation and trimethylsilylation; these results may be useful for the identification and quantification of these compounds in other biological materials.

Pressure effects on the stability of lipoxygenase: Fourier transform-infrared spectroscopy (FT-IR) and enzyme activity studies.

Fourier transform infrared spectroscopy (FT-IR) studies of lipoxygenase at pressures of up to 1.2 GPa have shown changes in the amide I' band which correlate to structural changes of the enzyme. The shift of the frequency maximum of the amide I' band at about 600 MPa suggests a cooperative change in the secondary structure of the protein. Studies of the changes in band width have shown the structural changes at 600 MPa to be irreversible. This has been confirmed by studies of enzyme activity after pressure treatment: exposure to 600 MPa for 30 min (40 degrees C) clearly reduced the activity of lipoxygenase. Anodic gel electrophoresis under non-denaturating conditions revealed a decrease in native protein parallel to the activity loss. A pressure-temperature-phase diagram for soybean lipoxygenase was established.

Some physico-chemical parameters that influence proteinase K resistance and the infectivity of PrP Sc after high pressure treatment

Crude brain homogenates of terminally diseased hamsters infected with the 263 K strain of scrapie (PrP Sc) were heated and/or pressurized at 800 MPa at 60°C for different times (a few seconds or 5, 30, 120 min) in phosphate-buffered saline (PBS) of different pH and concentration. Prion proteins were analyzed on immunoblots for their proteinase K (PK) resistance, and in hamster bioassays for their infectivity. Samples pressurized under initially neutral conditions and containing native PrP Sc were negative on immunoblots after PK treatment, and a 6-7 log reduction of infectious units per gram was found when the samples were pressurized in PBS of pH 7.4 for 2 h. A pressure-induced change in the protein conformation of native PrP Sc may lead to less PK resistant and less infectious prions. However, opposite results were obtained after pressurizing native infectious prions at slightly acidic pH and in PBS of higher concentration. In this case an extensive fraction of native PrP Sc remained PK resistant after pressure treatment, indicating a protective effect possibly due to induced aggregation of prion proteins in such buffers.