Structural insight into the transglycosylation step of bacterial cell-wall biosynthesis

Peptidoglycan glycosyltransferases (GTs) catalyze the polymerization step of cell-wall biosynthesis, are membrane-bound, and are highly conserved across all bacteria. Long considered the "holy grail" of antibiotic research, they represent an essential and easily accessible drug target for antibiotic-resistant bacteria, including methicillin-resistant Staphylococcus aureus. We have determined the 2.8 angstrom structure of a bifunctional cell-wall cross-linking enzyme, including its transpeptidase and GT domains, both unliganded and complexed with the substrate analog moenomycin. The peptidoglycan GTs adopt a fold distinct from those of other GT classes. The structures give insight into critical features of the catalytic mechanism and key interactions required for enzyme inhibition.     

膨胀素的基因家族及功能

膨胀素是一类能够诱导植物细胞壁松弛的蛋白。目前发现的膨胀素基因家族共由4个家族组成,分别为α-膨胀素、β-膨胀素、类α-膨胀素和类β-膨胀素。简述了膨胀素基因家族及其进化历史,概括介绍了近年来发现的膨胀素功能,综述了近年来国内外关于膨胀素作用机制的研究进展。     

小崎齿瓢虫属AfidentulaKapur1955的种类及地理分布

小崎齿瓢虫属 Afidentula Kapur 1955自建立以来,迄今该属共有14个种,其中包括我国云南省记载的一新种。本文在概括小崎齿瓢虫属的分类地位、种类及分布的基础上,讨论了小崎齿瓢虫属的区系,色斑类型等问题。列出了已知种的检索表,文后并附种的特征图。     

稻瘟病菌假定的糖基水解酶62家族初步研究

 【目的】了解糖基水解酶62家族细胞壁降解酶系在稻瘟病菌致病中的作用。【方法】通过生物信息学方法对稻瘟病菌基因组中假定的糖基水解酶62家族成员进行基因结构、蛋白分泌特性及系统发育分析,并对其中一个成员MGG_01403.6进行过量表达、基因敲除分析。【结果】该家族共有8个成员,均具有细胞壁降解酶（糖基水解酶62家族）保守结构域,且均为胞外分泌蛋白;系统发育分析可以将这些成员分别聚类在两个进化分支中;成员间在不同侵染阶段表达模式有差异;MGG_01403.6过量表达和基因敲除均不影响稻瘟病菌的致病性。【结论】糖基水解酶62家族可能存在功能冗余作用,进一步的双突变或多突变可能是明确这类多基因家族基因功能的重要方法。     

3种人工培育木材化学成分与纤维形态的研究

对杨树351，黑荆树和喜树木材的化学成分与纤维形态进行了测定及分析，旨在为其用于制造人造板及制浆提供必要的基础数据．研究结果表明：3种木材综纤维素含量高，纤维形态好，纤维长度大，长宽比高，壁腔比小于l；分析认为3种木材均是生产纸浆、纤维板、刨花板的优质原料．     

Intracellular olfactory response of hippocampal neurons in awake, sitting squirrel monkeys

Intracellular recordings of archicortical neurons in a primate have been made and the responses of these neurons in awake, sitting animals have been observed. Electrical stimulation of the olfactory bulbs elicits excitatory postsynaptic potentials in these neurons, which unlike those evoked by septal stimulation, are subliminal for generating spikes. The olfactory and septal pathways may be considered representative of inputs from exteroceptive and interoceptive systems. The findings are discussed in relation to a paradigm for archicortical conditioning.     

Comparative proteomic analysis of cold responsive proteins in two wheat cultivars with different tolerance to spring radiation frost

Spring radiation frost (SRF) is a severe environmental stress which impairs wheat yield and productivity worldwide. To better understand the mechanism of wheat (Triticum aestivum) responding to SRF, a comparative proteomic analysis was performed to analyze the changes of the key proteins in two wheat cultivars Jimai22 and Luyuan301 with high and low tolerance to SRF respectively. A total of 43 differentially expressed proteins (DEPs) which mainly involved in carbohydrate metabolism, amino acid metabolism, resistance proteins and antioxidant enzymes, photosynthesis and cellular respiration proteins, cell-wall related proteins, protein translation/processing/degradation and signal transduction were isolated and identified by two-dimensional electrophoresis and MALDI-TOF-TOF MS. The results revealed that of the 21 DEPs in Jimai22 responding to the SRF, 13 DEPs were upregulated and 8 DEPs were downregulated, and that of the 22 DEPs in Luyuan301, 9 DEPs were upregulated and 13 DEPs were downregulated. These DEPs might be responsible for the stronger cold resistance of Jimai22 compared to Luyuan301. The expression pattern and function analysis of these DEPs were very significant to understanding the mechanism of the SRF responses in wheat.     

破壁方法对短乳杆菌谷氨酸脱羧酶提取效果的影响

采用不同的破壁方法提取短乳杆菌谷氨酸脱羧酶（GAD）,研究破壁方法对所得GAD活力的影响。结果表明,超声波破壁有利于菌体释放胞内谷氨酸脱羧酶。正交试验结果表明,超声波破壁的最佳工艺条件为：超声功率220 W,工作时间20 min,工作/间歇时间比5 s/10 s。     

用酶法对啤酒酵母细胞破壁优化条件的研究

试验旨以溶菌酶、蜗牛酶对啤酒酵母进行破壁,从中筛选出最佳的破壁条件。以啤酒酵母作为破壁酵母细胞,采用四因素四水平的正交试验设计进行试验。结果表明,酶量10 mg.mL-1,pH 5.0,温度45℃,时间6 h时的破壁率均高于以上各因素的水平。各因素对破壁率的影响顺序为:温度>时间>酶量>pH。蜗牛酶和溶菌酶破壁率差异不显著(P>0.05)。结果揭示本试验条件下溶菌酶、蜗牛酶最佳破壁条件为酶量10 mg.mL-1,pH 5.0,温度45℃,时间6 h。     

玉米小斑病菌T小种毒素诱导对玉米叶片苯丙氨酸解氨酶活性的影响

分别采用低浓度玉米小斑病菌Hel minthospolium maydis T小种毒素(HMT毒素)和玉米小斑病菌T小种培养滤液中的提取蛋白及菌丝细胞壁的提取液,预处理不同玉米品种3叶期叶片后再接种高浓度HMT毒素,在无菌条件下培养5 d后测量叶片病斑大小,并测定玉米叶片内苯丙氨酸解氨酶(PAL)活性变化。结果表明:只有纯化的低浓度HMT毒素能够作为激发子诱导玉米获得系统性广谱抗性,但不同玉米品种所需的最适合浓度有差异;TC103以质量浓度0.025μg/mL毒素预处理效果最好,PAL活性最高;TB37和TMo17 2个自交系,以质量浓度分别为0.025μg/mL和0.050μg/mL的毒素预处理效果最好。     

Raman microprobe evidence for lignin orientation in the cell walls of native woody tissue

Raman microprobe spectra from the secondary wall of earlywood tissue from Picea mariana (black spruce) reveal evidence of the orientation of lignin relative to the plane of the cell wall. In most instances, the aromatic rings of the phenyl propane structural units are parallel to the plane of the cell-wall surface.     

日本落叶松自由授粉家系形质性状遗传变异的研究

该文以 12年生日本落叶松自由授粉家系子代测定林为对象 ,对生长和干形性状的遗传变异、性状间的相关关系进行研究 ,并利用选择指数方法对形质性状进行了综合评价 .结果表明 :胸径、树高、材积、主枝长、皮厚、主枝粗、冠幅、新枝粗和新发枝数家系间变异达显著或极显著水平 ,且受中度或较强的遗传控制 ,具有很大的家系选择潜力 ;家系间圆满度、新枝长、分枝角和活枝下高的差异不显著 ,且遗传力较低 ,开展家系选择的意义不大 ;生长性状之间、生长和形质性状之间表现出极强的正相关 ,且这种相关关系主要受遗传因素控制 ,形质性状中只有新枝数与主枝长两性状相互独立 .     

Old-growth forests can accumulate carbon in soils

Old-growth forests have traditionally been considered negligible as carbon sinks because carbon uptake has been thought to be balanced by respiration. We show that the top 20-centimeter soil layer in preserved old-growth forests in southern China accumulated atmospheric carbon at an unexpectedly high average rate of 0.61 megagrams of carbon hectare-1 year-1 from 1979 to 2003. This study suggests that the carbon cycle processes in the belowground system of these forests are changing in response to the changing environment. The result directly challenges the prevailing belief in ecosystem ecology regarding carbon budget in old-growth forests and supports the establishment of a new, nonequilibrium conceptual framework to study soil carbon dynamics.     

Organogenic elements and compounds in surface samples from the sea of tranquillity

Organogenic elements, mainly carbon, nitrogen, phosphorus, and sulfur are present in the particulate material and in a breccia rock from Tranquillity Base in amounts ranging from 5 to 4200 parts per million. The major compounds of carbon released by heating are carbon monoxide and carbon dioxide; the former predominates. Small amounts of other compounds of carbon have also been observed. Sulfur can be released as hydrogen sulfide by treatment with acid. The carbon isotopic delta(13L)C values are definitely nonterrestrial (+ 13 to + 18.5 per mil).     

Blood cells preserved in a mummy 2000 years old

Structures resembling red blood cells have been seen in mummies, but have been considered by some to be artifacts or molds. The finding of these structures, admixed with white blood cells, in the blood vessels of a mummified American Indian, confirms the original interpretation of preserved red blood cells.     

Genetic technologies. Bioengineered food--safety and labeling

The safety and labeling of genetically engineered foods are two areas that have elicited considerable public concern and debate. This Policy Forum provides a legal analysis of these issues in the context of two bills that have been recently proposed in The U.S. Congress, the Genetically Engineered Food Safety Act and the Genetically Engineered Food Right to Know Act. Most transgenic components of foods currently on the market are plant-incorporated protectants or their inert ingredients. Therefore, they have been evaluated for safety by the Environmental Protection Agency (as well as the Food and Drug Administration), and their disclosure in labeling should not be required. If plant-incorporated protectants are considered safer than chemical pesticides, and chemical pesticides do not have to be disclosed in labels, then bioengineered foods should not be subject to stricter regulation, nor should they be required to be labeled. The two bills are inconsistent, in many respects, with well-established principles of food regulation.     

Natural abundance carbon-13 nuclear magnetic resonance spectra of human serum lipoproteins

Human serum lipoproteins have been studied by Fourier transform nuclear magnetic resonance of carbon-13 in natural abundance. Spectra of highdensity, low-density, and very-low-density lipoproteins were recorded and partly assigned. The prominent features of these spectra reflect the qualitative and quantitative composition of the lipid moiety of these complexes. The results suggest that carbon-13 nuclear magnetic resonance will be a useful technique for studies of the structural and dynamic parameters of lipoproteins.     

中国松针锈病病原菌—鞘锈菌研究现状及问题

中国松针锈病病原菌——鞘锈菌(Coleosporium Le′v.) 已知有48种,除一种短循环型生活史的偃松鞘锈菌(C.pini-pumilae Azb.)外,其余均为长循环型生活史,夏孢子、冬孢子寄主涉及到单子叶和双子叶植物的13个科,57个属。中国鞘锈菌只有9个种的寄主关系和生活史已明确,其余都未经过人工接种,锈孢子寄主关系及生活史未知。由于鞘锈菌对寄主选择不太严格,相近种的寄主又有重叠,使人们对鞘锈菌按形态定属名,按寄主定种的传统分类方法是否完全合理产生了怀疑。我们认为确定鞘锈菌种,不仅要考虑孢子形态等特征,还要考虑不同地区鞘锈菌对寄主范围,从优选择和限定选择等多种情况,通过人工接种试验,结合野外调查,对鞘锈菌进行深入的研究,扭转当今分类上的混乱局面,为综合防治提供理论依据。     

小麦抗赤霉病新品系的选育

本文概述了60085等13个小麦抗赤霉病新品系的选育经过、鉴定结果及其利用价值。这些新品系于1981年经全国小麦赤霉病研究协作组联合鉴定,在3万多份品种资源材料中抗病性表现突出。尤其是60085、60006和50002三个品系, 已作为重要的抗源材料保存。作者认为,利用现有抗源进行杂交育种,转移和累加抗病性,是培育抗赤霉病新品种的重要途径。为了选育抗病性强而稳定的新品种,育种过程必须强调抗病性鉴定和多代连续选择。     

Global control of dimorphism and virulence in fungi

Microbial pathogens that normally inhabit our environment can adapt to thrive inside mammalian hosts. There are six dimorphic fungi that cause disease worldwide, which switch from nonpathogenic molds in soil to pathogenic yeast after spores are inhaled and exposed to elevated temperature. Mechanisms that regulate this switch remain obscure. We show that a hybrid histidine kinase senses host signals and triggers the transition from mold to yeast. The kinase also regulates cell-wall integrity, sporulation, and expression of virulence genes in vivo. This global regulator shapes how dimorphic fungal pathogens adapt to the mammalian host, which has broad implications for treating and preventing systemic fungal disease.