Identification and characterization of an {alpha}-mannosidase from Trypanosoma cruzi

In this report we describe the first purification and characterizationof the acid -mannosidase from the human parasite Trypanosomacruzi. The purified enzyme exhibited a native mol. wt of 240000 Da and is apparently composed of four identical subunitsof mol. wt 58 000 Da. Each of the four subunits contains oneN-linked high-mannose-type oligosaccharide. The -mannosidaseexhibited a pH optimum of 3.5 and a pI of 5.9. This low pH optimumand the ability of swainsonine to inhibit its activity suggestthat the -mannosidase is a lysosomal enzyme. Antibodies againstthe T.cruzi enzyme did not react with mammalian lysosomal -mannosidaseand, conversely, antibody against a rat lysosomal -mannosidasedid not react with the T.cruzi enzyme. Thus, the T.cruzi enzymeappears to be distinct from its mammalian counterpart. -mannosidase lysosomal enzyme Trypanosoma cruzi     

Feeding and growth of larval herring,Clupea harengus,in relation to density of copepod nauplii

Synopsis Feeding and growth rates of 1–3 wk old herring larvae from four different stocks were compared in laboratory experiments (8°C). For most of the larval groups, feeding rate was saturated at nauplii (Acartia tonsa, nauplii stages 3–5) densities over 301^–1 (5 g d.w. 1^–1). Specific growth rate increased asymptotically with nauplii density, and reached about 6% d^–1 at densities over 120 nauplii 1^–1. The growth rates attained in the laboratory were similar to field measured growth rates of similarly aged herring larvae at comparable food densities. Since food particles were homogenously distributed in the laboratory tanks, patches of dense plankton concentrations are, thus, apparently not necessary for larval growth and survival in the sea. Growth efficiency differed between larval groups, with large sized larvae being the most efficient in transforming ingested matter into growth. The difference probably relates to different sizes rather than to the different geographical origins of the larvae.     

Tubular Transport Maxima of PAH and Diodrast Measured Individually in the Aglomerular Kidney of Lophius, and Simultaneously as Competitors Under Conditions of Equimolar Loading

The maximal tubular transfer rates (Tm) of both p-aminohippurate (PAH) and diodrast (3,5-diiodo-4-pyridone-N-acetic acid or iodopyracet) were found to be fixed and reproducible when measured separately in Lophius (goosefish) under standard laboratory conditions. Expressed on a molar basis Tm_PAH was four times Tm_D. However, when these transport competitors were presented simultaneously in equimolar concentrations with the plasma levels of each sufficiently high enough to saturate the carrier system, the relative rates of excretion were reversed with the diodrast transfer rate then four times that of PAH. The combined rate of excretion was far below Tm_PAH alone, and roughly equal to Tm_D. Interaction with a common carrier was indicated by the gradations in degree of inhibition which resulted when plasma concentration ratios of diodrast to PAH were extended from 0.1 to 3.2, and PAH transfer rates expressed as percentage of Tm_PAH were correspondingly depressed from 17 to 1.0 per cent respectively. These observations again point up the inverse relationship between transfer rate and competitive effectiveness which exists for members of a series of substances actively transported by a common mechanism. It appears that carrier affinity and dissociation characteristics may be quite different for various compounds in a series, and also that these parameters may vary significantly from species to species.     

Biochemical Studies on Amphibian Metamorphosis : I. The effect of thyroxine on protein synthesis in the tadpole

Thyroxine has been shown to accelerate the synthesis of carbamyl phosphate synthetase in the liver of Rana catesbeiana. Stimulation of carbamyl phosphate synthetase synthesis by thyroxine appears to be relatively specific because of the following observations: (1) succinoxidase activity decreased during the time that carbamyl phosphate synthetase increased; (2) liver catalase responded more slowly than carbamyl phosphate synthetase to thyroxine; (3) the ratio of biochemical changes/morphological changes was greatly altered during thyroxine-induced metamorphosis. The relationships between the concentration of thyroxine and (1) temperature; (2) duration of exposure of the tadpole to thyroxine; and (3) the activity of carbamyl phosphate synthetase during the induced synthesis of carbamyl phosphate synthetase by thyroxine are discussed. Chloramphenicol and thiouracil partly counteracted the effect of thyroxine on the synthesis of carbamyl phosphate synthetase.     

Comparative studies on S-adenosyl-l -methionine binding sites of protein N-methyltransferases, using 8-azido-S-adenosyl-l -methionine as photoaffinity probe

Employing a photoaffinity labeling procedure with 8-azido-S-adenosyl-l-[methyl-³H]methionine (8-N₃-Ado[methyl-³H]Met), the binding sites for S-adenosyl-l-methionine (AdoMet) of three protein N-methyltransferases [AdoMet:myelin basic protein-arginine N-methyltransferase (EC2.1.1.23); AdoMet:histone-arginin N-methyltransferase (EC2.1.1.23); and AdoMet:cytochromec-lysine N-methyltransferase (EC2.1.1.59)] have been investigated. The incorporation of the photoaffinity label into the enzymes upon UV irradiation was highly specific. In order to define the AdoMet binding sites, the photolabeled enzymes were sequentially digested with trypsin, chymotrypsin, and endoproteinase Glu-C. After each proteolytic digestion, radiolabeled peptide from each enzyme was resolved on HPLC first by gradient elution and further purified by an isocratic elution. Retention times of the purified radiolabeled peptides from the three enzymes from the corresponding proteolysis were significantly different, indicating that their sizes and compositions were different. Amino acid composition analysis of these peptides confirmed further that the AdoMet binding sites of these protein N-methyltransferases are quite different.     

Oxide-Based Solid-State Batteries: A Perspective on Composite Cathode Architecture

The garnet-type phase Li₇La₃Zr₂O₁₂ (LLZO) attracts significant attention as an oxide solid electrolyte to enable safe and robust solid-state batteries (SSBs) with potentially high energy density. However, while significant progress has been made in demonstrating compatibility with Li metal, integrating LLZO into composite cathodes remains a challenge. The current perspective focuses on the critical issues that need to be addressed to achieve the ultimate goal of an all-solid-state LLZO-based battery that delivers safety, durability, and pack-level performance characteristics that are unobtainable with state-of-the-art Li-ion batteries. This perspective complements existing reviews of solid/solid interfaces with more emphasis on understanding numerous homo- and heteroionic interfaces in a pure oxide-based SSB and the various phenomena that accompany the evolution of the chemical, electrochemical, structural, morphological, and mechanical properties of those interfaces during processing and operation. Finally, the insights gained from a comprehensive literature survey of LLZO–cathode interfaces are used to guide efforts for the development of LLZO-based SSBs.     

Lipase-catalyzed synthesis of lysophosphatidic acid in a solvent free system

Summary The direct, lipase-catalyzed esterifications of glycerol-3-phosphate in an organic solvent system and in a solvent free system were carried out. In a solvent free system only, LPA synthesis could be achieved within the acceptable reaction time. Open reaction system was preferable to closed reaction system for LPA synthesis. Yield of LPA isolated by silica gel column chromatography was 32.3%.     

Inhibition of Taq DNA polymerase by seaweed extracts from British Columbia, Canada and Korea

Fifty-nine species of marine macrophytes from the coasts of British Columbia, Canada and Korea have been screened for the presence of PCR inhibitors, namely inhibitors of Taq DNA polymerase. Eleven of the species displayed some inhibitor activity. At the concentration of 5 μg of methanol extract in 25μL reaction mixture of PCR containing 1.5 unit of Taq DNA polymerase, one (Ulva sp.) of 8 Chlorophyta, eight (Colpomenia bullosa, Ecklonia cava, Endarachne binghamiae, Fucus distichus, Hizikia fusiformis, Sargassum confusum, Sargassum sagamianum, and Sargassum thunbergii) of 28 Phaeophyta, and one (Symphyocladia latiuscula) of 34 Rhodophyta showed inhibition in PCR amplification. In the case of the water extract, two (Cladophora columbiana, Ulva sp.) Chlorophyta, seven (Endarachne binghamiae, Fucus distichus, Hizikia fusiformis, Sargassum confusum, Sargassum sagamianum, Sargassum horneri, Scytosiphon dotyi) Phaeophyta, no Rhodophyta and one (Phyllospadix scouleri) seagrass showed inhibition in PCR amplification. the methanol fraction of Sargassum confusum and the water fraction of Fucus gardneri (mid–intertidal) have been found to inhibit PCR at level as low as 0.5 μg in 25μL of PCR reaction mixture. This revised version was published online in August 2006 with corrections to the Cover Date.     

Identification of three genetic loci controlling leaf senescence in Arabidopsis thaliana

Four mutants that show the delayed leaf senescence phenotype were isolated from Arabidopsis thaliana . Genetic analyses revealed that they are all monogenic recessive mutations and fall into three complementation groups, identifying three genetic loci controlling leaf senescence in Arabidopsis . Mutations in these loci cause delay in all senescence parameters examined, including chlorophyll content, photochemical efficiency of photosystem II, relative amount of the large subunit of Rubisco, and RNase and peroxidase activity. Delay of the senescence symptoms was observed during both age-dependent in planta senescence and dark-induced artificial senescence in all of the mutant plants. The results indicate that the three genes defined by the mutations are key genetic elements controlling functional leaf senescence and provide decisive genetic evidence that leaf senescence is a genetically programmed phenomenon controlled by several monogenic loci in Arabidopsis . The results further suggest that the three genes function at a common step of age-dependent and dark-induced senescence processes. It is further shown that one of the mutations is allelic to ein2-1 , an ethylene-insensitive mutation, confirming the role of ethylene signal transduction pathway in leaf senescence of Arabidopsis .     

Methanogenesis in thermophilic biogas reactors

Methanogenesis in thermophilic biogas reactors fed with different wastes is examined. The specific methanogenic activity with acetate or hydrogen as substrate reflected the organic loading of the specific reactor examined. Increasing the loading of thermophilic reactors stabilized the process as indicated by a lower concentration of volatile fatty acids in the effluent from the reactors. The specific methanogenic activity in a thermophilic pilot-plant biogas reactor fed with a mixture of cow and pig manure reflected the stability of the reactor. The numbers of methanogens counted by the most probable number (MPN) technique with acetate or hydrogen as substrate were further found to vary depending on the loading rate and the stability of the reactor. The numbers of methanogens counted with antibody probes in one of the reactor samples was 10 times lower for the hydrogen-utilizing methanogens compared to the counts using the MPN technique, indicating that other non-reacting methanogens were present. Methanogens that reacted with the probe againstMethanobacterium thermoautotrophicum were the most numerous in this reactor. For the acetate-utilizing methanogens, the numbers counted with the antibody probes were more than a factor of 10 higher than the numbers found by MPN. The majority of acetate utilizing methanogens in the reactor wereMethanosarcina spp. single cells, which is a difficult form of the organism to cultivatein vitro. No reactions were observed with antibody probes raised againstMethanothrix soehngenii orMethanothrix CALS-1 in any of the thermophilic biogas reactors examined. Studies using 2-¹⁴C-labeled acetate showed that at high concentrations (more than approx. 1 mM) acetate was metabolized via the aceticlastic pathway, transforming the methyl-group of acetate into methane. When the concentration of acetate was less than approx. 1 mM, most of the acetate was oxidized via a two-step mechanism (syntrophic acetate oxidation) involving one organism oxidizing acetate into hydrogen and carbon dioxide and a hydrogen-utilizing methanogen forming the products of the first microorganism into methane. In thermophilic biogas reactors, acetate oxidizing cultures occupied the niche ofMethanothrix species, aceticlastic methanogens which dominate at low acetate concentrations in mesophilic systems. Normally, thermophilic biogas reactors are operated at temperatures from 52 to 56° C. Experiments using biogas reactors fed with cow manure showed that the same biogas yield found at 55° C could be obtained at 61° C after a long adaptation period. However, propionate degradation was inhibited by increasing the temperature.