Shigeo Aibara

Differences in fatty acid composition among phosphatidylethanolamine, phosphatidylglycerol and cardiolipin of Escherichia coli

Abstract The fatty acid composition of phosphatidylethanolamine, phosphatidylglycerol and cardiolipin of Escherichia coli B during growth at various temperatures was analyzed. Marked differences in the unsaturated fatty acid content, especially the cis-vaccenic acid content, were observed among the three phospholipids during the exponential growth phase at any given temperature. As the cultures progressed to the stationary growth phase, unsaturated fatty acids decreased.

Effect of changes in fatty acid composition of phospholipid species on the β-galactoside transport system of Escherichia coli K-12

Abstract On lowering the growth temperature of Escherichia coli K-12 from 37 to 17 °C, the cells resumed growth after a lag period of 40 min. During the lag period, the transition points in Arrhenius plots of the preinduced β-galactoside transport system were not changed while the saturated/unsaturated fatty acids ratio decreased gradually in phosphatidylethanolamine, rapidly in phosphatidylglycerol and little in cardiolipin.

Structural and Functional Characterization of Recombinant Human Serum Transferrin Secreted from Pichia pastoris

Serum transferrin is an iron-binding glycoprotein with a bilobal structure. It binds iron ions in the blood serum and delivers them into target cells via transferrin receptor. We identified structural and functional characteristics of recombinant human transferrin which is produced in the yeast Pichia pastoris. Using the signal sequence of the α factor of the yeast Saccharomyces cerevisiae, high-level secretion was obtained, up to 30 mg/l of culture medium. Correct processing at designed sites was confirmed by N-terminal sequence analysis. Carbohydrate modification was determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis after digestion with endo-β-N-acetylglucosaminidase H. Reflecting the secondary structure, the circular dichroism spectrum of the recombinant protein was indistinguishable from that of serum transferrin. Consequently, the recombinant product had an iron binding function just as the serum specimen has: two Fe3+ sites existed in a recombinant transferrin molecule, as estimated by titration analysis using visible absorption, fluorescence spectra, and electrophoretic behavior in urea denaturing polyacrylamide gel electrophoresis (PAGE).

Microstructures of Bread Dough and the Effects of Shortening on Frozen Dough

Three types of straight doughs different in combination of yeast and shortenings (RLS20, FTS20, and FTS80) were prepared, and the structure of the frozen doughs was examined under a microscope after staining protein or lipid droplets. Even after 2 months of frozen storage, distinct changes were not found in the gluten network of FTS80, although significant damages in the dough structures of FTS20 and RLS20 appeared after only one month of frozen storage. These results suggest that the gluten networks loosen and decrease in the water retention ability, and it may be concluded that the lipid is removed from the gluten protein due to the decrease in water in the continuous protein phase. The resulting product from the damage to the gluten matrix gave rise to fusion of lipid droplets and an increase in their size. Because of the difference in fatty acid composition, the lipids of shortening S80 are presumed to interact more strongly with gluten proteins and to keep the gluten matrix from damage in comparison with the lipids of shortening S20.

Preliminary crystallographic study of ω-amino acid: Pyruvate aminotransferase from Pseudomonas sp. F-126

Abstract Large single crystals of ω-amino acid: pyruvate aminotransferase, were prepared by dialysis of the enzyme solution against 2.2 m -ammonium sulphate solution at pH 7.8. X-ray diffraction patterns show that the crystals belong to the orthorhombic space group I222 or I212121 with unit cell dimensions a = 124.1 A , b = 137.9 A , and c = 61.2 A . The asymmetric unit consists of one monomer of molecular weight 43,000.

Effects of High-Voltage Electric Field Treatment on Bread Starch

Bread dough was subjected to a high-voltage electric field (HVEF) during the first fermentation, and the bread firmness and the crystallinity of the starch (intensity of diffraction peak at 17.08° 2θ assigned to 4a; 5.24 Å d-spacing) isolated from the breads, which had been stored at 4 and 20°C, were examined. The HVEF treatment had the effects of reducing the bread firming at both storage temperatures as compared to the untreated bread. In this study, unexpected results were obtained for the crystallinity in the HVEF treated bread starches: while the firmness of the treated bread increased considerably after the first 3 days of storage at both temperatures, the rate of development in crystallinity was retarded at 20°C as compared with that of the untreated bread, but the opposite effect was observed at 4°C; that is, storing the bread at 4°C, the treated bread starch increased in crystallinity. These findings strongly suggest that crumb firming of the bread is involved in its water retention ability, taking into account the fact that the HVEF treatment made it possible to maintain bread softness longer than was possible for untreated bread. We, therefore, concluded that the increase in bread firmness was not closely related to the crystallinity of the bread starch, but was more influenced by the storage temperature.

Crystallization of wheat γ-gliadin under a microgravity environment using space station MIR

Abstract Single crystals of wheat γ-gliadin, which have not been obtained in the ground crystallization experiments, appeared from a PEG8000 solution of 30mM aluminum lactate, pH 3.4, by a hanging-drop method under a microgravity environment aboard space station MIR. The experimental period was 58 days at 20.3 ± 1.5°C, and crystals grew in a rectangular shape. They had a biaxial crystal possibility from the observation of polarizing microscopy.

Purification and characterisation of wheat γ-gliadins

Three γ-gliadin components were separated and purified by reversed-phase and gel-permeation high-performance liquid chromatography after extraction from defatted wheat flour with 70% ethanol. The apparent relative molecular mass (M r s) of the components, termed 8A-1, 8A-2, and 8B were 38,000, 35,000 and 45,000 as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The purified components had amino acid compositions typical of γ-gliadins. Components 8A-1 and 8B were classified as γ 2 - and γ 3 -gliadins, respectively, on the basis of their N-terminal amino acid sequences. The circular dichroism spectrum of component 8 B indicated that it contained α-helical conformations (about 27%) and β-structures (about 32%); the spectrum was characteristic of an α+β type protein with separate α-helix- and β-sheet-rich regions.

Crystal morphology change by magnetic susceptibility force

Abstract We found a change in morphology when lysozyme crystals were grown in a magnetic field. The phenomenon was caused by the magnetic force derived from the magnetic susceptibility gradient. We propose that this force should be called the ‘magnetic susceptibility force’.

Crystal growth of hen egg-white lysozyme using a crystallization vessel produced for a spacelab experiment

Crystallization conditions of hen egg-white lysozyme (mucopeptide N-acetylmuramylhydrolase, EC 3.2.1.17) were investigated at 20°C using an enzyme crystallization vessel designed and produced for a spacelab experiment. Relatively large single crystals of the enzyme grew within 6 days by the batch method under the protein concentration of 28–30 mg/ml and in the limited concentration ranges of 3.2 to 3.6% (w/v) NaCI as the precipitant. The crystals grown on the upper wall of the vessel were large and well-shaped, but those grown on the bottom were not as good. Single crystals more than 3 mm in each dimension appeared in 3 to 4 months under the lower protein concentration, but they had cracks when growing as large as 5 mm and were disrupted.