A Study of the Binding of Estradiol and 8-Isoestradiol to the Estrogen α-Receptor by Molecular Modeling

The complexes of the estrogen -receptor with estradiol and 8-isoestradiol were comparatively analyzed. The computations of ligand–receptor complexes, carried out using the FLEXX program, allowed us to propose a model for the binding of the analogues of 8-isoestradiol. It was found that rings Cand D of estradiol and 8-isoestradiol are similarly arranged in the ligand-binding pocket and coincide upon the superposition of the corresponding ligand–receptor complexes, whereas rings A and B do not coincide. The oxygen functions in position 17 of the estradiol analogues of both series coincide upon superposition, whereas the phenol 3-hydroxyl groups are 0.05 Å apart. A comparison of the predicted biological properties of modified estradiol analogues of the natural and 8-iso-series with the available experimental data revealed their similarity. Synthetic 2-acetyl analogues of 8-isoestrogens were found to have no uterotropic activity, which is also consistent with the proposed model.     

New Triterpene Glycosides from an Ulosa sp. Sponge

New triterpene glycosides, ulososides C, (20S,22S,23R,24S)-3,22,23-trihydroxy-3-O-(-D-glucopyranosyl)-32-nor-24-methyllanost-8(9)-ene-30-oic acid, D, (20S,22S,23R,24S)-3,22,23-trihydroxy-3-O-(-D-N-acetylglucosaminopyranosyl)-32-nor-24-methyllanost-8(9)-ene-30-oic acid, and E, (20S,22S,23R,24S)-3,22,23-trihydroxy-3-O-(-D-glucuronopyranosyl-(1 2)--D-arabinopyranosyl-32-nor-24-methyllanost-8(9)-ene-30-oic acid, were isolated from an Ulosa sp. sponge. Their structures were determined by spectral methods and chemical transformations. Specific features of their structures are discussed.     

A predictive model for the growth rate of Bacillus cereus in broth by response surface methodology

A response surface methodology (RSM) was developed for predicting the growth rate of Bacillus cereus in a tryptic soy broth medium as a function of temperature (10 to 40°C), pH (5.5 to 8.5), and the NaCl concentration (0 to 8%). The primary model showed a good fit (r² = 0.920 to 0.999) to a Gompertz equation to obtain growth rates each condition. The quadratic polynomial model was found to be significant (p < 0.0001) and predicted values were found to be in good agreement with experimental values (R² value of 0.9486). The evaluation of RSM for describing the growth rate of B. cereus used the bias factor (B_f) and the accuracy factor (A_f). Both the B_f value (1.11) and the A_f value (1.50) were within acceptable ranges. This model was provided an efficient and accurate method for predicting the growth of B. cereus as a function of the controlling factors.     

母乳源乳双歧杆菌Probio-M8的遗传特征及基因组差异比较分析

【目的】母乳源乳双歧杆菌（Bifidobacterium animalis subsp. lactis） Probio-M8具有优良的益生特性,本文拟从全基因组水平解析Probio-M8的遗传特征,并与已有益生功效的乳双歧杆菌的基因组进行比较分析。【方法】本研究基于NCBI已公开的21株乳双歧杆菌和1株模式菌株DSM10140^T的基因组数据,构建了核心基因集与泛基因集,解析该群体的系统发育关系,比较分析Probio-M8的遗传特征及功能基因组。【结果】22株乳双歧杆菌的泛基因集包含1 618个基因,其中核心基因1 514个,占泛基因集的93.57%,表明乳双歧杆菌核心基因集高度保守。以1 514个核心基因构建系统发育树,发现22株乳双歧杆菌分为两个分支,AD011单独为一个分支,Probio-M8和其他菌株与模式菌株DSM10140^T聚在同一分支,且Probio-M8与V9、BB-12、Bi-07、HN019的遗传距离极为接近。进一步分析耐药基因和毒力基因,在Probio-M8与V9、BB-12、Bi-07、HN019基因组上均检测到DfrA...     

Neoglycoconjugates Based on Dendrimer Poly(aminoamides)

Neoglycoconjugates containing 4, 8, 32, and 64 terminal residues of B-disaccharide (B_DI) or N-acetylneuraminic acid (Neu5Ac) attached to poly(aminoamide)-type dendrimers (PAMAMs) were synthesized. The ability of B_DI conjugates to bind natural xenoantibodies (anti-B_DI antibodies) and the ability of Neu5Ac conjugates to inhibit the hemagglutinin-mediated adhesion of influenza virus were studied. The biological activity of PAMAM conjugates turned out to be higher than that of free carbohydrate ligands, but less than that of multivalent glycoconjugates based on other types of synthetic polymeric carriers. A conformational analysis of PAMAM matrices and resulting conjugates was performed to determine the statistical distances between carbohydrate ligands. The computations revealed the tendency of the PAMAM chains toward compaction and formation of dense globules. The process results in a decrease in the distances between the carbohydrate ligands in the conjugates and, hence, could affect the ability of glycoconjugates to efficiently bind the polyvalent carbohydrate-recognizing proteins.     

The use of immunological tolerance to investigate B lymphocyte replacement kinetics in chickens

A simple mathematical model has been derived, describing the irreversible inactivation of immature B cells by high doses of antigen during induction of tolerance, and the antigen-independent replacement of B cells by differentiation of their precursors. The latter leads to recovery from tolerance, the rate of which can be used to assess the rate of B cell replacement in experiments. The model has been compared with experimental tolerance to human albumin in newly hatched chickens.(1) It has been shown that this tolerance cannot be explained only by elimination of B cells but (2) the computed rate of B cell replacement agreed with the experimental rate assessed by immunization of tolerant chickens with a cross-reacting antigen. (3) In order to further verify the model, additional experiments to test the rate of B cell replacement were suggested by the model.     

Cloning and identification of partial DNA fragment for the <Emphasis Type="Italic">B</Emphasis> mating-type factor in <Emphasis Type="Italic">Lentinula edodes</Emphasis> using degenerate PCR

The edible fungus Lentinula edodes is a heterothallic homobasidiomycete whose mating is controlled by a bifactorial incompatibility mating system determined by two unlinked factors (the A and B mating-type factors). Although this mechanism is well accepted, there is a lack of understanding about its molecular basis, as the incompatibility factors have not been cloned and sequenced. In this study, by means of degenerate PCR we obtained one 773 bp DNA fragment cosegregating with B ₂ mating-type factor in L. edodes stock HL01. Sequencing analysis revealed that it belonged to a pheromone receptor, suggesting that the genetic basis for B factor in L. edodes is the same as in the two model mushroom species, Schizophyllum commune and Coprinus cinereus, the structure and function of whose B incompatibility factors have been studied in detail. So far as we know, this is the first report about the cloning of B mating factor in L. edodes.     

The −689/+197 region of the maize protease inhibitor gene directs high level,wound-inducible expression of the cry1B gene which protects transgenic rice plants from stemborer attack

To investigate the activity of the regulatory region of the maize (Zea mays L.) proteinase inhibitor (mpi) gene, we transferred into rice (Oryza sativa L.) plants the –689/+197 (C1) fragment of the mpi genomic clone fused to either theuidA gene or a synthetic Bacillus thuringiensis cry1B gene. Although uidA and cry1B encode very different proteins consistent results were obtained from their respective histochemical and fluorometric and immunoblot detections in T₃ transgenic rice lines. In response to mechanical wounding, a 4–5 fold increase in GUS activity and a Cry1B accumulation reaching 0.1–0.2% of total soluble proteins were observed from basal and undetectable levels respectively in leaf tissue. The establishment of the time-course of wound response in both systems revealed a maximum induction level 12–16 h after treatment. From both systems we also deduced that the C1 region is not active in pollen and seed endosperm. Three independent transformation events expressing cry1B under the control of the C1 region exhibited protection against striped stem borer damage and showed 100% mortality of second instar larvae 8 days after release. These results illustrate the first evidence that wound-inducible expression of a Bacillus thuringiensis endotoxin gene affords full protection to transgenic rice plants.     

Degradation and Utilization of Xylans by the Rumen AnaerobePrevotella bryantii(formerlyP. ruminicolasubsp.brevis) B14

Freshly harvested whole cells from cultures ofP. bryantiiB₁4 grown with oat spelt xylan (OSX) as an energy source showed less than 25% of the enzyme activity against OSX, and less than 15% of the activity against birchwood xylan (BWX) and carboxymethylcellulose, that was detectable in sonicated cell preparations. This indicates that much of this hydrolytic activity is either periplasmic, membrane-associated or intracellular and may be concerned with the processing of transported oligosaccharides.P. bryantiiB₁4 cultures were able to utilise up to 45% and 51% of the total pentose present in OSX and BWX, respectively, after 24 h, but could utilize 84% of a water-soluble fraction of BWX. Analysis of the xylan left undegraded after incubation withP. bryantiishowed that while xylose and arabinose were removed to a similar extent, uronic acids were utilized to a greater extent than xylose. Predigestion of xylans with two cloned xylanases from the cellulolytic rumen anaerobeRuminococcus flavefaciensgave little increase in overall pentose utilization suggesting that externalP. bryantiixylanases are as effective as the clonedR. flavefaciensenzymes in releasing products that can be utilised byP. bryantiicells. The xylanase system ofP. bryantiiis able to efficiently utilise not only xylo-oligosaccharides but also larger water-soluble xylan fragments.     

Biosynthesis of vitamin B12

Radioactivity from [1-¹⁴C]riboflavin was incorporated into the 5,6-dimethylbenzimidazole moiety of Vitamin B₁₂ in the aerobes Bacillus megaterium, Nocardia rugosa and Streptomyces sp. as well as in the aerotolerant anaerobe Propionibacterium freudenreichii, but not in the anaerobe Eubacterium limosum.As recently published for E. limosum, also in the anaerobe Clostridium barkeri radioactivity from [1-¹⁴C]glycine and [2-¹⁴C]glycine was found in the 5,6-dimethylbenzimidazole moiety, but not in the corrin moiety. The addition of l-[methyl-¹⁴C]methionine to C. barkeri led to the labeling of the corrin moiety and the 5,6-dimethylbenzimidazole moiety, showing that the seven extra methyl groups in the corrin ring as well as the two methyl groups of the base part originate from this precursor.In Clostridium thermoaceticum, forming the vitamin B₁₂ analog 5-methoxybenzimidazolylcobamide, [1-¹⁴C]glycine and [2-¹⁴C]glycine were also incorporated into the 5-methoxybenzimidazole moiety, but not into the corrin ring.In E. limosum l-[U-¹⁴C]glutamate led to the labeling of the corrin ring of vitamin B₁₂, but not of its base moiety.There results together with data from the literature indicate that a common biosynthetic pathway might exist for the corrinoid biosynthesis in aerobic microorganisms, and in those aerotolerant anaerobes like the Propionibacteria, which form the 5,6-dimethylbenzimidazole moiety of vitamin B₁₂ only under aerobic conditions. They also show that this pathway differs from the pathway found in anaerobic bacteria.     

Boron translocation in coffee trees

Boron deficiency in coffee trees (Coffea arabica) is widespread, however, responses to B fertilizer have been erratic, depending on the year, method, and time of application. A better understanding of B uptake, distribution, and remobilization within the plant is important in developing a rational fertilization program. Field and greenhouse experiments were conducted to study B distribution and remobilization in coffee trees. Boron was provided either in the nutrient solution or sprayed on the leaves of trees grown under adequate or transient B deficiency. There was clear evidence for B translocation via symplast (remobilization) to coffee grains, even in well-nourished plants. When ¹⁰B was present in the nutrient solution during most part of fruit filling, from 33 to 40% of the B found in coffee fruits was absorbed during this period, depending on the timing and duration of the B deficiency treatment. In the field, when B was sprayed once on the leaves, around 4% of the fruit B was derived from the foliar fertilizer. Boron remobilization within coffee trees is limited in well nourished plants, but it can be significant during periods of temporary B deficiency in plants otherwise well nourished with B. The implications of these findings for B fertilization practice, are discussed.     

Vitamin B12 transport in Escherichia coli K12 does not require the btuE gene of the btuCED operon

Summary Transport of vitamin B₁₂ across the cytoplamic membrane ofEscherichia coli requires the products ofbtuC andbtuD, two genes in thebtuCED operon. The role ofbtuE, the central gene of this operon, was examined. Deletions withinbtuE were constructed by removal of internal restriction fragments and were crossed onto the chromosome by allelic replacement. In-frame deletions that removed 20% or 82% of thebtuE coding region did not affect expression of the distalbtuD gene. These nonpolar deletions had little effect on vitamin B₁₂ binding (whole cells or periplasmic fraction) and transport. They did not affect the utilization of vitamin B₁₂ or other cobalamins for methionine biosynthesis, even in strains with decreased outer membrane transport of vitamin B₁₂. ThebtuE mutations did not impair adenosyl-cobalamin dependent catabolism of ethanolamine or repression ofbtuB expression. Thus, despite its genetic location in the transport operon, thebtuE product plays no essential role in vitamin B₁₂ transport.     

Ear-rot fungi and mycotoxins in South African corn of the 1989 crop exported to Taiwan

A shipment of South African corn (1989) exported to Taiwan, was analyzed for various ear-rot fungi andFusarium mycotoxins. Two sets of samples, one from the points of origin in South Africa prior to shipment, and the other from the end-point distributors in Taiwan, were studied. Surface-sterilized kernels were plated onto two different agar media and the fungal colonies identified. High Performance Liquid Chromatography was used to analyze mycotoxin levels. The predominant ear-rot fungi, in decreasing order of isolation frequency, wereFusarium subglutinans, F. moniliforme, Diplodia maydis andF. graminearum. Aspergillus flavus andA. parasiticus were not isolated from samples prior to export, but a small number ofA. flavus isolates were found after shipment. The predominant mycotoxins were fumonisins B₁ (0–865 ng/g) and B₂ (0–250 ng/g). Low levels of moniliformin (390 ng/g) were detected in some samples before shipment. Zearalenone (25 ng/g), and nivalenol (120 ng/g) were detected in two out of 32 samples taken in Taiwan. The samples contained no detectable levels of either aflatoxins (>0.5 ng/g) or deoxynivalenol (>100 ng/g) before or after shipment.Abbreviations RSA South Africa(n) - FB₁ fumonisin B₁ - FB₂ fumonisin B₂ - ETVL eastern Transvaal - WTVL western Transvaal     

Induction of tumor clones in D. melanogaster wts/+ heterozygotes with chemical carcinogens

Ten chemicals were assessed for blastomogenic activity in adult wts/+ heterozygotes of D. melanogaster. All of the strong mammalian carcinogens tested (benzo(a)pyrene (B(a)P), pyrene, aflatoxin B₁, 2-acetylaminofluorene (2-AAF) and cis-dichlorodihydroxydiamminoplatinum IV) were also shown to be strong Drosophila blastomogens. They induced several times more tumors than their counterparts that are less carcinogenic for mammals (4-acetylaminofluorene (4-AAF), aflatoxins B₂ and G₂) and 4-(methylnitrosamino)-1-(-3-pyridine)-1-butanone (NNK). Benzo(e)pyrene (B(e)P) and pyrene demonstrated minor effects. Most tumors were localized on the wing and notum, which are the derivatives of the wing disc. Humeri derived from dorsal prothoracic disc and the abdominal tergites and sternites had the lowest number of tumors. The tumor frequency in the cross of the wild type females with wts^P2/TM6B males was different from that in the reciprocal cross. The former type of cross exhibited consistently higher tumor frequency both in the experimental and control series.     

沉默大豆GmWRKY33B基因导致大豆抗病性降低

WRKY转录因子基因家族是植物特有的转录因子,在防御中起着重要作用。通过生物信息学分析,本研究在古四倍体大豆(Glycine max)基因组中找到一对同源性高达93%的WRKY33同源基因,并将其命名为GmWRKY33B。从GmWRKY33B的两个同源基因保守区域选取一个315 bp片段构建至菜豆豆荚斑驳病毒(bean pod mosaic virus, BPMV)沉默载体(BPMV-VIGS)上,以期同时沉默上述2个GmWRKY33B基因。结果表明,同时沉默2个GmWRKY33B基因并不显著改变沉默植株的表型,但却显著降低了大豆对大豆斑点病菌以及大豆花叶病毒的抗性,说明GmWRKY33B在大豆免疫反应中起正调控作用。激酶分析表明,GmWRKY33B沉默植株中flg22诱导的GmMPK6的磷酸化水平较空载体BPMV-0植株显著降低,说明GmWRKY33B可以通过调控GmMPK6的激酶活性而参与大豆的免疫反应。抗毒素为大豆中主要起防御作用的植保素,而大豆异黄酮类特异性异戊烯基转移酶(prenyltransferase, PT)基因家族是参与大豆抗毒素生物合成的主要基因,许多PT基因启动子区含有与WRKY特异性结合的W-box序列。在丁香假单胞菌pv.甘氨酸(Pseudomonas syringae pv. glycinea, Psg)侵染条件下,4个PT基因的表达水平在沉默株系中显著降低,说明GmWRKY33B参与PT基因的转录激活。综上所述,GmWRKY33B通过调控GmMPK6的激活以及调控大豆抗毒素生物合成途径中关键酶编码基因的表达而参与免疫反应。     

Production of extracellular enzymes and aflatoxins in solid substrate fermentation with aflatoxigenic<Emphasis Type="Italic">Aspergillus</Emphasis> spp.

AflatoxigenicAspergillus flavus andAspergillus parasiticus were subjected to solid substrate fermentation process for 6 days to determine the formation of aflatoxins and production of extracellular enzymes (amyloglucosidase, cellulase, invertase and proteinase). Both organisms produced enzymes which generally increased with fermentation.Aspergillus flavus produced four enzymes whereasA. parasiticus produced three with no proteinase activity.Aspergillus parasiticus produced aflatoxins B₁, B₂ and G₁ but no G₂ andA. flavus produced aflatoxins B₁ and B₂. Invertase showed the highest activity withA. parasiticus and that corresponded with the highest total toxin produced. The enzyme activities were higher withA. parasiticus thanA. flavus although total toxins produced byA. parasiticus were lower than total toxins produced byA. flavus under the same environmental conditions.     

辣椒镰孢根腐病防病促生细菌的筛选及其效应

【目的】筛选辣椒(Capsicum annuum L.)根腐病防病促生细菌并明确其防病促生效应。【方法】采集健康辣椒根围土壤样品,以辣椒根腐病病原真菌茄镰孢(Fusarium solani)和尖镰孢(Fusarium oxysporum)为指示菌,采用平板对峙法筛选生防细菌,采用选择性培养基筛选溶无机磷、溶有机磷、固氮菌和解钾菌等促生菌,钼锑抗比色法测定溶磷量,凯氏定氮法测定固氮量,火焰原子吸收光谱法测定解钾量。对特性良好组合的菌株进行16S rDNA序列分析鉴定并制作菌剂,最后采用盆栽法测定菌剂防病促生效果。【结果】共筛选得到323株特性良好的功能菌株,拮抗菌78株,溶有机磷菌87株,溶无机磷菌107株,固氮菌128株,解钾菌123株,部分菌株同时具有多个功能特性。互作组合得到6个特性良好的菌株组合,包括8株功能菌株,鉴定发现XP271和XP181为枯草芽胞杆菌(Bacillus subtilis),XP125为特基拉芽胞杆菌(Bacillus tequilensis),XP236为耐盐芽胞杆菌(Bacillus halotolerans),XP79为巨大芽胞杆菌(Bacillus ...     

Impact of oxygen supply on rtPA expression in <Emphasis Type="Italic">Escherichia coli</Emphasis> BL21 (DE3): ammonia effects

A phytase with high activity at neutral pH and typical water temperatures (∼25°C) could effectively hydrolyze phytate in aquaculture. In this study, a phytase-producing strain, Pedobacter nyackensis MJ11 CGMCC 2503, was isolated from glacier soil, and the relevant gene, PhyP, was cloned using degenerate PCR and thermal asymmetric interlaced PCR. To our knowledge, this is the first report of detection of phytase activity and cloning of phytase gene from Pedobacter. PhyP belongs to beta-propeller phytase family and shares very low identity (∼28.5%) with Bacillus subtilis phytase. The purified recombinant enzyme (r-PhyP) from Escherichia coli displayed high specific activity for sodium phytate of 24.4 U mg⁻¹. The optimum pH was 7.0, and the optimum temperature was 45°C. The K _m, V _max, and k _cat values were 1.28 mM, 71.9 μmol min⁻¹ mg⁻¹, and 45.1 s⁻¹, respectively. Compared with Bacillus phytases, r-PhyP had higher relative activity at 25°C (r-PhyP (>50%), B. subtilis phytase (<8%)) and hydrolyzed phytate from soybean with greater efficacy at neutral pH. These characteristics suggest that r-PhyP might be a good candidate for an aquatic feed additive in the aquaculture industry.