Mold Filling and Prevention of Gas Entrapment in High-pressure Die-casting

This paper presents some results of direct observation of mold filling in a specially designed die-casting by X-ray diffraction, including comparison with numerical simulation. Based on such work the authors discuss how to prevent gas entrapment and propose new methods.     

Importance of the Ca2+-binding sites in the N-catalytic domain of a family I.3 lipase for activity and stability

A family I.3 lipase from Pseudomonas sp. MIS38 (PML) contains three Ca(2+)-binding sites (Ca1-Ca3) in the N-catalytic domain. Of them, the Ca1 site is formed only in an open conformation. To analyze the role of these Ca(2+)-binding sites, three mutant proteins D157A-PML, D275A-PML and D337A-PML, which are designed to remove the Ca1, Ca2 and Ca3 sites, respectively, were constructed. Of them, the crystal structures of D157A-PML and D337A-PML in a closed conformation were determined. Both structures are nearly identical to that of the wild-type protein, except that the Ca3 site is missing in the D337A-PML structure. D157A-PML was as stable as the wild-type protein. Nevertheless, it exhibited little lipase and very weak esterase activities. D275A-PML was less stable than the wild-type protein by approximately 5 degrees C in T(1/2). It exhibited weak but significant lipase and esterase activities when compared with the wild-type protein. D337A-PML was also less stable than the wild-type protein by approximately 5 degrees C in T(1/2) but was fully active. These results suggest that the Ca1 site is required to make the active site fully open by anchoring lid 1. The Ca2 and Ca3 sites contribute to the stabilization of PML. The Ca2 site is also required to make PML fully active.     

Glycosylceramides obtain from the starfish Asterias amurensis Lütken

Complex lipids in the starfish Asterias amurensis were characterized and the influence of sphingoid bases on human colon carcinoma Caco-2 cells was also investigated. Lipid content of gonad and viscera were 3.3% and 6.8%, respectively, in wet basis. The main lipid class in gonad was ceramide monohexoside (CMH) while triglyceride (TG) was predominant in the viscera. The most abundant fatty acid in the polar lipid was eicosapentaenoic acid (EPA, C20:5n-3), with the gonad and viscera samples having the highest proportion of 41.5% and 32.7%, respectively, of total fatty acids. Starfish internal organ contained enormous amount (0.7% in wet base) of glycosylceramide. Sphingoid bases of the glycosylceramide were mainly consisted of d22:2, d22:1 and d18:3. This sphingoid base exerted an apoptotic activity on Caco-2 cells. Thus, starfish could be used as a potential source of precious and useful complex lipids.     

Characterization of N-linked oligosaccharides attached to recombinant human antithrombin expressed in the yeast Pichia pastoris

We studied the structures of four N-linked oligosaccharide chains of the recombinant human antithrombin (rAT) expressed in the yeast Pichia pastoris. rAT was fully glycosylated at Asn 96 and Asn 155, whereas the glycosylation on Asn 135 and Asn 192 was partial. The glycosylation level on Asn 135 was only 12% and this reduction is assumed to be one of the reasons for a higher heparin-binding affinity of rAT than plasma-derived human antithrombin (pAT). In order to determine the sizes and electrostatic charges of the N-linked oligosaccharides, rAT was treated with PNGase F, and the reduced ends were labelled by pyridylamination followed by analysis using anion exchange and amide adsorption columns. The N-linked oligosaccharides were 78% neutral and 22% phosphomannosylated. The neutral oligosaccharides were thought to be Man(9-12)GlcNAc(2) as their major components. The phosphomannosylated oligosaccharides were then subjected to mild acid hydrolysis and/or digestion with alkaline phosphatase, and their charge shifts were analysed by the affinity to an anion exchange column. Among phosphomannosylated oligosaccharides, monophosphate diester type was predominant, whereas negatively charged diphosphate diester and monophosphate monoester types were minor components. The mannose residues at the non-reducing end(s) of Man(9-12)GlcNAc(2) were phosphomannosylated or phosphorylated and these are the major components. Because rAT is less negatively charged than pAT, which has disialyl biantennary N-glycans, it might be less repulsive to pentasaccharide-bearing anticoagulantly active heparan sulphate proteoglycan molecules exposed on the surface of the damaged vascular vessels.     

Effect of soy protein isolate on gel properties of Alaska pollock and common carp surimi at different setting conditions

The effects of soy protein isolate (SPI) on the gel properties of different grade Alaska pollock and common carp surimi at different setting conditions were evaluated and compared. Breaking force and distance of gels decreased with increasing SPI concentrations in direct cook (85 °C for 30 min) and in cook after setting at 30 °C for 60 min conditions. The effect of SPI on gel strength of common carp surimi was less than in Alaska pollock surimi. The breaking force obtained for addition of 10% SPI to Alaska pollock surimi was higher than for surimi alone when cooked after incubation at 50 °C for 60 min. Addition of SPI decreased the whiteness and increased the yellowness of the gel. The gel structure showed that the addition of SPI modified the microstructure of the fish protein gel, thus resulting in surimi with different gelling properties. Copyright © 2004 Society of Chemical Industry     

A Fluorescence‐Based Method for Cyanate Analysis in Ethanol/Water Media: Correlation between Cyanate Presence and Ethyl Carbamate Formation in Sugar Cane Spirit

Based on the fluorescence properties of 2,4‐(1H,3H)‐quinazolinedione, a product of the reaction between cyanate and 2‐aminobenzoic acid, a simple, sensitive, selective, and reproducible method for the cyanate analysis in aqueous ethanolic media is proposed. In this method, λ_exc and λ_em are 310 and 410 nm, respectively, and the limits of detection and quantification are 2.2 × 10^?7 and 6.7 × 10^?7 mol/L, respectively. Under optimal conditions (pH = 4.5, 40% ethanol), a concentration of 5.0 × 10^?6 mol/L cyanate can be determined in a single measurement, at a 95% level of confidence, with an uncertainty of ± 0.13 × 10^?6 mol/L. Cyanide, thiocyanate, chloride, nitrate, and sulfate ions, as well as urea and urethane in concentrations 1 × 10³ higher than that of cyanate do not interfere with the measurement. The methodology was applied to cyanate analyses in the different fractions of the sugarcane distillate and the data strongly suggest a correlation between the presence of urea in wine, and the cyanate and ethyl carbamate concentrations in the spirit.     

Efficient production of L-lactic acid from xylose by a recombinant Candida utilis strain

Efficient L-lactic acid production from xylose was achieved using a pyruvate decarboxylase-deficient Candida utilis strain expressing an L-lactate dehydrogenase, an NADH-preferring mutated xylose reductase (XR), a xylitol dehydrogenase and a xylulokinase. The recombinant strain showed 53% increased L-lactic acid production compared with the reference strain expressing native XR (NADPH-preferring).     

Production of lactic acid from xylose and wheat straw by Rhizopus oryzae

Rhizopus oryzae NBRC 5378 was the best among 56 strains of R. oryzae for the production of lactic acid from xylose. This strain produced lactic acid from wheat straw powder by a simultaneous saccharification and fermentation process, with a yield of 0.23 g/g from cellulose and hemicellulose in wheat straw.     

Year-round high arachidonic acid levels in herbivorous rabbit fish Siganus fuscescens tissues

To identify a stable resource of 20∶4 n−6 (arachidonic acid, AA) in marine fish tissues, the lipid profiles of Siganus fuscescens organs (muscle, liver, and other viscera) and stomach contents were examined throughout the year. Crude total lipid (TL) contents in respective organs showed seasonal variations and were high in winter and low in summer. The main FA in TL were 16∶0, 18∶0, 16∶1n−7, 18∶1n−9, AA, and 22∶6n−3 (DHA). These FA were those generally observed in marine fish lipids, except for comparatively high levels of AA. In TL of muscle and liver, AA showed relatively high values during the period from late May to August (muscle, 4.6–13.1%; liver, 4.5–9.1%), compared with other seasons (muscle, 4.3–9.5%; liver, 3.6–8.4%). The AA levels in TL of other viscera and stomach contents fluctuated (other viscera, 2.0–10.7%; stomach contents, 7.6–26.7%). Regardless of the fishing season, each organ contained a higher level of AA in polar lipids (PL) than in neutral lipids. It was concluded that the fish contain comparatively high levels of AA in their TL throughout the year, and they accumulate AA characteristically in their tissue PL, probably from dietary food sources. Moreover, it was suggested that S. fuscescens has potential utility as a natural marine source of nutritional lipids, because the fish contain comparatively high levels of DHA and AA.     

Effects of Elevated Carbon Dioxide and Ozone on Foliar Proanthocyanidins in Betula platyphylla, Betula ermanii, and Fagus crenata Seedlings

Proanthocyanidins (PAs) or condensed tannins are a major group of phenolic compounds in the leaves of birch trees and many other woody and herbaceous plants. These compounds constitute a significant allocation of carbon in leaves and are involved in plant responses to environmental stress factors, such as pathogens or herbivores. In some plants, PA concentrations are affected by atmospheric carbon dioxide (CO₂) and ozone (O₃) levels that may influence, for example, species fitness, community structure, or ecosystem nutrient cycling. Therefore, a study on the quantitative response of PAs to elevated concentrations of carbon dioxide (CO₂) and ozone (O₃) was undertaken in seedlings of Betula platyphylla, Betula ermanii, and Fagus crenata. Seedlings were exposed to ambient or elevated O₃ and CO₂ levels during two growing seasons in the Kanto district in Japan. Ten open-top chambers were used for five different treatments with two replicates: filtered air (FA), ambient air (ambient O₃, 43 ppb; ambient CO₂, 377 ppm), elevated O₃ (1.5 × ambient O₃, 66 ppb), elevated CO₂ (1.5 × ambient CO₂, 544 ppm), and elevated O₃ and CO₂ combined. In addition, seedlings growing in natural conditions outside of chambers were studied. Leaf samples were analyzed for total PA concentrations by butanol–HCl assay and for polymeric PA concentrations by normal-phase high-performance liquid chromatography. Total PA concentrations in leaves of all species were similarly affected by different treatments. They were significantly higher in seedlings treated with elevated CO₂ and O₃ combined, and in seedlings growing outside chambers compared with the FA controls. F. crenata contained only traces of polymeric PAs, but significant species × treatment interaction was observed in the polymeric PA concentrations in B. ermanii and B. platyphylla. In B. platyphylla, leaves treated with elevated CO₂ + O₃ differed significantly from all other treatments. It was suggested that the strongest effect of elevated CO₂ and O₃ combined on leaf PA contents resulted from the additive effect of these environmental factors on phenolic biosynthesis.