Model Studies of the Iron-Catalysed Haber-Weiss Cycle and the Ascorbate-Driven Fenton Reaction

Complementary hydroxylation assays and stopped-flow e.s.r. techniques have been employed in the investigation of the effect of various iron chelators (of chemical, biological and clinical importance) on hydroxyl-radical generation via the Haber-Weiss cycle and the ascorbate-driven Fenton reaction.

Chelators have been identified which selectively promote or inhibit various reactions involved in hydroxyl-radical generation (for example, NTA and EDTA promote all the reactions of both the Haber-Weiss cycle and the ascorbate-driven Fenton reaction, whereas DTPA and phytate inhibit the recycling of iron in these reactions). The biological chelators succinate and citrate are shown to be relatively poor catalysts of the Haber-Weiss cycle, whereas they are found to be effective catalysts of ·OH generation in the ascorbate-driven Fenton reaction.

It is also suggested that continuous redox-cycling reactions between iron, oxygen and ascorbate may represent an important mechanism of cell death in biological systems.     

Surface structure of the two porcine low-density lipoprotein subclasses — a spin labelling study

Porcine low-density lipoprotein (LDL) subclasses were spin-labelled at both protein and lipid sites. The surface structures of the two subclasses were compared. E.s.r. spectra of stearic acid spin-labels [I(m/n)] and of androstanol spin-label indicated more restricted motion of the labels in LDL₂ (d = 1.063?1.090 g/ml) than in LDL₁ (d = 1.020?1.063 g/ml). Thermotropic change in the surface structure was found in both subclasses by both protein and lipid spin-labels, but at lower temperature in LDl₁, than in LDL₂. These results indicate the relationship between the size and the dynamics of the lipid components in the surface layer of the LDL subclasses.     

一类生化反应系统极限环的存在唯一性

讨论一类具有二重饱和反应速度的生化反应模型,给出了该系统极限环的不存在性、存在性和唯一性的充分条件,并与具有米氏饱和反应速度的生化模型的定性性质进行比较。     

Heparin in molluscs: chemical, enzymatic degradation and C and H n.m.r. spectroscopical evidence for the maintenance of the structure through evolution

The structural features and anticoagulant activity of heparins isolated from three species of molluscs (Anomalocardia brasilian, Donnax striatus and Tivela mactroides) are reported. It is shown by chemical analyse, type of products formed by action of heparinase and heparitinase II, anticoagulant activity, ¹³C and ¹H n.m.r. spectroscopy, that the mollusc heparins are virtually indistinguishable from heparins present in mammalian tissues. These data, taken as a whole, suggest that heparin has maintained its main structural features through evolution. The implications of these findings are discussed.     

Probing of the porcine serum lipoprotein surfaces by Mn(II) binding: an e.s.r. study

Mn(II) ions were used for probing the surfaces of porcine LDL₁, LDL₂ and HDL. From the intensity of the e.p.r. lines corresponding to the unbound Mn(II) the percentage of the ions bound to the lipoprotein surface is determined. From the titration curves the binding parameters, dissociation constant. K_d, and the number of binding sites, n, in all the three lipoproteins studied have been derived. There are at least two types of binding sites in each lipoprotein class. The ”weak’ binding sites are charaterized by approximately the same value of $\text{K}{}_{\mathrm{<mtext>d</mtext>}}\text{(≈ 6.2 × 10}{}^{\mathrm{?3}}\text{mol l}{}^{\mathrm{?1}}$ and different values for n (n = 114 for LDL₁, n = 135 for LDL₂ and n = 28 for HDL). Similarly, for the ”strong’ binding sites K_d ≈ 1.6 × 10^?4 mol l^?1 and the number of binding sites is 15, 20 and 5 for LDL₁, LDL₂ and HDL respectively. It is concluded that the binding sites are probably located in the protein part of the lipoproteins and that they are mainly associated with the negatively charged amino acids.     

Esr Spin Trapping Studies Into of Nature of the Oxidizing Species Formed in the Fenton Reaction: Pitfalls Associated With of Use Of 5,5-Dimethyl-1-Pyrroline-n-Oxide in the Detection of the Hydroxyl Radical

Several investigators have challenged the widely held view that the hydroxyl radical is the primary oxidant formed in the reaction between the ferrous ion and hydrogen peroxide. In recent studies, using the ESR spin trapping technique, Yamazaki and Piette found that the stoichiometry of oxidant formation in the reaction between Fe²⁺ and H₂O₂ often shows a marked deviation from the expected value of 1:1 (I. Yamazaki and L. H. Piette (1990) J. Am. Chem. Soc. 113, 7588-7593). In order to account for these observations, it was suggested that additional oxidizing species are formed, such as the ferryl ion (FeO²⁺), particularly when iron is present at high concentration and chelated to EDTA.

In this paper it is shown that secondary reactions, involving the redox cycling of iron and the oxidation of the hydroxyl radical adduct of the spin trap 5,5-dimethyl-1-pyrroline-N-oxide(DMPO) by iron, operate under the reaction conditions employed by Yamazaki and Piette. Consequently, the stoichiometry of oxidant formation can be rationalized without the need to envisage the formation of oxidizing species other than the hydroxyl radical. It is also demonstrated that the iron(III) complex of DETAPAC can react directly with DMPO to form the DMPO hydroxyl radical adduct (DMPO/OH) in the absence of hydrogen peroxide. Therefore, to avoid the formation of (DMPO/OH) as an artefact, it is suggested that DETAPAC should not be used as a reagent to inactivate containating adventitious iron in experiments using DMPO.     

固定化金霉素产生菌原生质体转化林可霉素反应模型的研究

建立了固定化金霉素产生菌金色链霉菌(Streptomyces aurofaciens)原生质体转化林可霉素反应动力学模型并模拟计算了反应过程,模型计算与实验结果有好的一致性。讨论了各反应参数对转化反应的影响,给出了转化率与反应时间的关系式和最大转化率计算式,还对转化反应动力学模型进一步应用进行了讨论。     

Experimental Studies of the Life Cycle of Leucocytozoon simondi in Ducks in Norway*

SYNOPSIS. Pekin ducks were infected naturally and experimentally. The life cycle of Leucocytozoon simondi was followed in the ducks and the vector, a new species of Simulium, close to Simulium dogieli. The prepatent period in the ducks was 4–5 days and developing megaloschizonts appeared in 6–7 days. Schizonts were found in liver, spleen, brain, and kidney. In the kidneys they were located in the glomeruli. Sporogony in some individuals was completed in 7 days at 13–14 C, other individuals developed more slowly, as ookinetes were found in flies 8 days after feeding. The rapid asexual cycle combined with a sporogonic cycle, in which some ookinetes develop rapidly and others more slowly, favors the maintenance of the parasite in an environment with relatively low daily temperatures. This and the size of the megaloschizonts indicate differences between this strain of the parasite and the one occurring in North America.     

Model for the Part Manufacturing and Vehicle Assembly Component of the Vehicle Life Cycle Inventory

A model is presented for calculating the environmental burdens of the part manufacturing and vehicle assembly (VMA) stage of the vehicle life cycle. The model is based on a process‐level approach, accounting for all significant materials by their transformation processes (aluminum castings, polyethylene blow molding; etc.) and plant operation activities (painting; heating, ventilation, and air conditioning [HVAC], etc.) germane to VMA. Using quantitative results for these material/transformation process pairings, a percent‐by‐weight material/transformation distribution (MTD) function was developed that permits the model to be applied to a range of vehicles, both conventional and advanced (e.g., hybrid electric, light weight, aluminum intensive). Upon consolidation of all inputs, the model reduces to two terms: one proportional to vehicle mass and a plant overhead per vehicle term. When the model is applied to a materially well‐characterized conventional vehicle, reliable estimates of cumulative energy consumption (34 gigajoules/vehicle) and carbon dioxide (CO₂) emissions (2 tonnes/vehicle) with coefficients of variation are computed for the VMA life cycle stage. Due to the more comprehensive coverage of manufacturing operations, our energy estimates are on the higher end of previously published values. Nonetheless, they are still somewhat underestimated due to a lack of data on overhead operations in part manufacturing facilities and transportation of parts and materials between suppliers and vehicle manufacturing operations. For advanced vehicles, the material/transformation process distribution developed above needs some adjusting for different materials and components. Overall, energy use and CO₂ emissions from the VMA stage are about 3.5% to 4.5% of total life cycle values for vehicles.     

C solution state and solid state n.m.r. of wheat gluten

¹³C solid state and solution state, high resolution n.m.r. spectra have been used to characterize wheat gluten both as dry solid and hydrated mass. Most peaks in the spectra have been satisfactorily assigned. Four different environments within the material have been distinguished corresponding to rigid immobile protein, mobile hydrophobic side chains, mobile lipid and a mobile protein fraction apparent in the hydrated material.     

Room temperature, low-field C-n.m.r. spectra of degraded carrageenans. Part II. On the specificity of the autohydrolysis reaction in kappa/iota and mu/nu structures

A kappa/iota carrageenan from Gigartina skottsbergii and a partially cyclized mu/nu carrageenan from Iridaea undulosa were submitted to autohydrolysis. The ¹³C-n.m.r. spectra of the degraded products give structural information on the polysaccharides and show clearly that besides the known splitting of 3,6-anhydrogalactosidic linkages, the linkage between - -galactose 2,6-disulphate and β- -galactose 4-sulphate is cleaved with similar specific reaction rate.     

Xanthophyll Cycle and Inactivation of Photosystem Ⅱ Reaction Centers Alleviating Reducing Pressure to Photosystem Ⅰ in Morning Glory Leaves under Short-term High Irradiance

Under 30-min high irradiance （1500μmol m^-2 s^-1）, the roles of the xanthophyll cycle and D1 protein turnover were investigated through chlorophyll fluorescence parameters in morning glory （Ipomoea setosa） leaves, which were dipped into water, dithiothreitol （DTT） and lincomycin （LM）, respectively. During the stress, both the xanthophyll cycle and D1 protein turnover could protect PSI from photoinhibition. In DTT leaves, non-photochemical quenching （NPQ） was inhibited greatly and the oxidation level of P700 （P700^＋） was the lowest one. However, the maximal photochemical efficiency of PSII （Fv/Fm） in DTT leaves was higher than that of LM leaves and was lower than that of control leaves. These results suggested that PSI was more sensitive to the loss of the xanthophyll cycle than PSII under high irradiance. In LM leaves, NPQ was partly inhibited, Fv/Fm was the lowest one among three treatments under high irradiance and P700^＋ was at a similar level as that of control leaves. These results implied that inactivation of PSII reaction centers could protect PSI from further photoinhibition. Additionally, the lowest of the number of active reaction centers to one inactive reaction center for a PSII cross-section （RC/CSo）, maximal trapping rate in a PSll cross-section （TRo/CSo）, electron transport in a PSll cross-section （ETo/CSo） and the highest of 1-qP in LM leaves further indicated that severe photoinhibition of PSII in LM leaves was mainly induced by inactivation of PSII reaction centers, which limited electrons transporting to PSh However, relative to the LM leaves the higher level of RC/CSo, TRo/CSo, Fv/Fm and the lower level of 1-qP in DTT leaves indicated that PSI photoinhibition was mainly induced by the electron accumulation at the PSI acceptor side, which induced the decrease of P700^＋ under high irradiance.     

Solution structure of the COMMD1 N-terminal domain

COMMD1 is the prototype of a new protein family that plays a role in several important cellular processes, including NF-kappaB signaling, sodium transport, and copper metabolism. The COMMD proteins interact with one another via a conserved C-terminal domain, whereas distinct functions are predicted to result from a variable N-terminal domain. The COMMD proteins have not been characterized biochemically or structurally. Here, we present the solution structure of the N-terminal domain of COMMD1 (N-COMMD1, residues 1-108). This domain adopts an alpha-helical structure that bears little resemblance to any other helical protein. The compact nature of N-COMMD1 suggests that full-length COMMD proteins are modular, consistent with specific functional properties for each domain. Interactions between N-COMMD1 and partner proteins may occur via complementary electrostatic surfaces. These data provide a new foundation for biochemical characterization of COMMD proteins and for probing COMMD1 protein-protein interactions at the molecular level.     

Contributions to the Life Cycle of Peneroplis planatus (Fichtel and Moll) Montfort

Direct observations of schizonts and agamonts releasing megalospheres clarified the asexual phase of the life cycle of Peneroplis planatus and made it most probable that this species has a paratrimorphic life cycle. Specimens with maximum lengths between 837 and 3,503 μm released about 500 to 1,500 megalospheric juveniles, which possessed two chambers (proloculi and flexostyles) prior to emergence from the parental shell. The presence of gamonts was not shown and was only implied by the occurrence of the agamonts. Since agamonts and schizonts have been found from December to May and since asexual reproduction occurs in spring in Elat, sexual reproduction probably occurs at another time of year (June to December). More detailed studies of this species need to be conducted throughout the year to improve our knowledge of the life cycle of this species.     

军标菌株生活史中各阶段生长发育时间的研究

为了更好地研究军标菌在其应用中的实验周期问题 ,采用插片培养法和载片培养法对军标中 5株实验菌的生活史中各阶段生长发育所需时间进行了研究。结果表明 ,5株菌的各时期生长发育所需时间有所不同。整个生活史最长的 4940min ,如AS 3 .42 5 4。最短的 3 888min ,如AS 3 .3 95 0。孢子萌发阶段所需时间也各不相同 ,最长的需 1 5 2 0min ,如AS 3 .3 885。最短的需 640min ,如AS 3 .3 95 0。这一研究为军标中霉菌试验周期 ,即 2 8d过长而且完全可缩短试验周期的观点 ,提供了有力的证据。     

Impact of Updated Material Production Data in the GREET Life Cycle Model

The Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model developed by Argonne National Laboratory quantifies the life cycle energy consumption and air emissions resulting from the production and use of light‐duty vehicles in the United States. GREET is comprised of two components: GREET 1 represents the fuel cycle of various energy carriers, including automotive fuels, and GREET 2 represents the vehicle cycle, which accounts for the production of vehicles and their constituent materials. The GREET model was updated in 2012 and now includes higher‐resolution material processing and transformation data. This study evaluated how model updates influence material and vehicle life cycle results. First, new primary energy demand and greenhouse gas (GHG) emissions results from GREET 2 for steel, aluminum, and plastics resins are compared herein with those from the previous version of the model as well as industrial results. A part of the comparison is a discussion about causes of differences between results. Included in this discussion is an assessment of the impact of the new material production data on vehicle life cycle results for conventional internal combustion engine (ICE) vehicles by comparing the energy and GHG emission values in the updated and previous versions of GREET 2. Finally, results from a sensitivity analysis are presented for identifying life cycle parameters that most affect vehicle life cycle estimates.     

Structural basis of DNA recognition by the alternative sigma-factor, sigma54

The sigma subunit of bacterial RNA polymerase (RNAP) regulates gene expression by directing RNAP to specific promoters. Unlike sigma(70)-type proteins, the alternative sigma factor, sigma(54), requires interaction with an ATPase to open DNA. We present the solution structure of the C-terminal domain of sigma(54) bound to the -24 promoter element, in which the conserved RpoN box motif inserts into the major groove of the DNA. This structure elucidates the basis for sequence specific recognition of the -24 element, orients sigma(54) on the promoter, and suggests how the C-terminal domain of sigma(54) interacts with RNAP.     

濒危植物峨眉黄连的生活史和繁殖特性及生态特征

峨眉黄连（Coptis omeiensis（Chen）C.Y.Cheng）是一种药用价值较高的国家二级保护植物。采用野外观察与室内解剖的方法,详细描述和分析了峨眉黄连的生活史、繁殖特性及生态特征,并寻找致危因子。结果表明：峨眉黄连从种子萌发至自然死亡,其生活史可分为4个时期,寿命长达15年以上。峨眉黄连行有性繁殖,无侧生无性繁殖枝;顶生芽是一个混合芽,由侧生花序和1个定芽组成;花的各部分均发育正常,花瓣原基和雄蕊原基同源;花粉粒直径16-24μm,有刺状雕纹。种子腹面有窄翼状突起,胚后熟,翌年萌发。海拔1100-1700m的阴湿岩壁是其最适生长环境,降雨量、温度、湿度和光照等因素对其生存与分布至关重要。     

Eimeria Meleagrimitis Tyzzer In Turkeys: the Life Cycle and Effects of Inoculum Size and Time On Severity of Infection and Intestinal Distribution

Developmental stages of Eimeria meleagrimitis Tyzzer were found throughout the intestine and ceca of turkeys given inocula ranging from 10⁴ to 7.5 × 10⁵ sporulated oocysts/bird. Infection initially occurred in the duodenum and upper jejunum but later moved down the intestine and into the ceca. the speed with which the infection moved into these areas was roughly proportional to the inoculum size. Heaviest infections were in the ileum, neck of the cecum, and large intestine. the life cycle consisted of 5 asexual generations before gametogony, a 6th asexual generation developing simultaneously with gametogony. First- and 2nd-generations were located along the sides of villi in the upper intestine rather than in the crypts of Lieberkühn, as previously described in England for this species. Transitory first-generation stages that were abnormally large and usually degenerate were found in the neck of the cecum.     

Structure-function relationship of [2Fe2S] ferredoxins and design of a model molecule

[2Fe2S] ferredoxins isolated from various plants and algae comprise 93–99 amino acid residues and resemble each other not only in sequences, but also in physiological functions. One of them isolated from Spirulina platensis was subjected to X-ray analysis and its three dimensional structure is now known. [2Fe2S] ferredoxins of a different type are found in halobacteria and comprise 128 amino acid residues. Both types of the [2Fe2S] ferredoxins exhibit low redox potentials. By comparing the amino acid sequences of 28 [2Fe2S] ferredoxins and the tertiary structure of S. platensis ferredoxin we predicted a common three-dimensional structure to the [2Fe2S] ferredoxins and proposed a molecular surface area to be interacting with FNR. An artificial small molecule composed of 20 amino acid residues is designed on the basis of the tertiary structure of S. platensis ferredoxin. The amino acid sequence was predicted to be ProTyrSerCysArgAlaGlyAlaCysSerThrCysAlaGly ProLeuLeuThr CysVal which should have a [2Fe2S] cluster with a low redox potential