Particle accelerators in the hot spots of radio galaxy 3C 445, imaged with the VLT

Hot spots (HSs) are regions of enhanced radio emission produced by supersonic jets at the tip of the radio lobes of powerful radio sources. Obtained with the Very Large Telescope (VLT), images of the HSs in the radio galaxy 3C 445 show bright knots embedded in diffuse optical emission distributed along the post-shock region created by the impact of the jet into the intergalactic medium. The observations reported here confirm that relativistic electrons are accelerated by Fermi-I acceleration processes in HSs. Furthermore, both the diffuse emission tracing the rims of the front shock and the multiple knots demonstrate the presence of additional continuous re-acceleration processes of electrons (Fermi-II).     

X-ray diffraction from magnetically oriented solutions of macromolecular assemblies

A simple system was developed for obtaining x-ray diffraction patterns from magnetically oriented solutions of macromolecular assemblies. A small permanent magnet was designed that produces a magnetic field of 16 kilogauss in a volume of 1 cubic millimeter and is mountable on most x-ray cameras. Many subcellular structures have sufficient diamagnetic anisotropy that they exhibit orientation in dilute solution when placed between the poles of the magnet. Diffraction from solutions oriented in this magnet can provide substantially more structural information than small-angle scattering from isotropic solutions. In favorable cases, such as dilute solutions of filamentous bacteriophages, it is possible to produce oriented fiber diffraction patterns from which intensities along layer lines can be measured to 7-angstrom resolution. The magnetically induced birefringence observed in solutions of other macromolecular assemblies suggests that this technique may have broad applicability to subcellular structures.     

腐殖质化学的光谱研究新进展

腐殖质是一类具有复杂结构的大分子有机化合物,广泛参与各种地球化学循环,并在工农业生产中扮演着及其重要的地位。因此,腐殖质的研究一直是学界关注的重点。近年来,光谱学技术的飞速发展为腐殖质化学的研究提供了有效的研究手段,特别是红外吸收光谱(IR)、核磁共振谱(NMR)、荧光光谱、紫外/可见光谱(UV/vis)、电子顺磁共振谱(EPR)等技术的运用,使得人们对于腐殖质的结构特征、反应机理都有了进一步的认识。综述了腐殖质化学的光谱学最新研究进展,为今后腐殖质化学研究及其在环境污染防治中的应用提供了参考。     

木麻黄优树无性系与其半同胞家系的生长比较

从木麻黄优良种源和优良家系中评选优良单株 ,分别用水培法繁育为无性系 (CL)和用其自由授粉种子繁育为半同胞家系 (HSF) ,得到 3个可比的育种材料 (L- 4、M- 1和 P- 1 9)进行遗传测定 .4a后调查其胸径 (D1.3)、树高 (H)和材积 (V) 3个性状 ,结果表明 :3个生长性状各优良单株无性系都显著优于其相应的半同胞家系 ,前者各性状的平均遗传增益分别为后者的 3.81、 3.56和 441倍 ,说明木麻黄造林更新宜采用源于优良单株无性系苗木 .采用多性状综合评价表明 :各优树的无性系和相应半同胞家系的优劣次序为 L- 4(CL) >M- 1 (CL) >P- 1 9(CL)>P- 1 9(HSF) >M- 1 (HSF) >L- 4(HSF) ,植树造林宜优先采用 L - 4(CL )和 M- 1 (CL) .     

Crystallographic R factor refinement by molecular dynamics

Molecular dynamics was used to refine macromolecular structures by incorporating the difference between the observed crystallographic structure factor amplitude and that calculated from an assumed atomic model into the total energy of the system. The method has a radius of convergence that is larger than that of conventional restrained least-squares refinement. Test cases showed that the need for manual corrections during refinement of macromolecular crystal structures is reduced. In crambin, the dynamics calculation moved residues that were misplaced by more than 3 angstroms into the correct positions without human intervention.     

Progress in modeling of protein structures and interactions

The prediction of the structures and interactions of biological macromolecules at the atomic level and the design of new structures and interactions are critical tests of our understanding of the interatomic interactions that underlie molecular biology. Equally important, the capability to accurately predict and design macromolecular structures and interactions would streamline the interpretation of genome sequence information and allow the creation of macromolecules with new and useful functions. This review summarizes recent progress in modeling that suggests that we are entering an era in which high-resolution prediction and design will make increasingly important contributions to biology and medicine.     

Three-dimensional structures of the TAFII-containing complexes TFIID and TFTC

TBP (TATA-binding protein)-associated factors (TAF(II)s) are components of large multiprotein complexes such as TFIID, TFTC, STAGA, PCAF/GCN5, and SAGA, which play a key role in the regulation of gene expression by RNA polymerase II. The structures of TFIID and TFTC have been determined at 3.5-nanometer resolution by electron microscopy and digital image analysis of single particles. Human TFIID resembles a macromolecular clamp that contains four globular domains organized around a solvent-accessible groove of a size suitable to bind DNA. TFTC is larger and contains five domains, four of which are similar to TFIID.     

Frontiers in crop production: chemical research objectives

The science of chemistry and chemicals will continue to be an integral part of future crop production technologies. In assessing and defining the future role of chemistry three imperatives must be considered: (i) the necessity to preserve natural resources, (ii) the complementary solutions offered by the rapidly advancing biological sciences, and (iii) the specific requirements of developing regions where increasing crop productivity is most important. Chemical research objectives for improving crop protection and crop growth must take into account the perceivable and potential changes in crop production techniques, which, in turn, are dictated by a number of accentuating constraints.     

腐殖质促进植物根和地上部生长的信号传导和串扰机制研究进展

天然高分子异构混合物腐殖质（HS）是陆地生态系统的重要组成部分,其促生作用近年来被广泛研究,其中多条信号通路在 HS 促进植物生长发育过程中起到重要作用。该文综述了 HS 促进植物根和地上部生长发育的信号通路传导及串扰机制。HS 在促进根系生长过程中吲哚乙酸（Indole-3-acetic acid,IAA）、一氧化氮（Nitric oxide,NO）、脱落酸（Abscisic acid,ABA）、活性氧（Reactive oxygen species,ROS）和 Ca2+ 等信号通路传导及相互串扰过程参与其中;HS 在促进地上部生长过程中细胞分裂素（Cytokinin,CTK）、ABA 和硝酸盐信号通路发生复杂的传导和相互串扰过程。HS 通过复杂的代谢网络调控植物生理代谢,调节机制涉及多条复杂信号通路的传导和串扰过程,其中质膜 H+-ATPase 是 HS 促进地下和地上部生长机制研究中的关键节点,多条信号通路通过质膜 H+-ATPase 介导相互级联放大的信号传导。在 HS 调控根系和地上部生长发育过程中,信使 NO 与多条信号通路间发生复杂的串扰过程,是参与 HS 促生作用的重要串扰信号分子。HS 在触发根和地上部生长发育过程中还存在其他信号通路,其中防御信号通路水杨酸（Salicylicacid,SA）和茉莉酸（Jasmonic acid,JA）受到信号通路 IAA、NO、ABA 和 CTK 等的调节。由于 HS 具有分散性、异质性和生物化学研究复杂性的特点,至今尚未明确 HS 对植物生长短期作用机制以及在整个植物生长周期内的整体作用机制,因此需要进一步深入分析揭示促生过程中所涉及到的信号传导、交叉、串扰和整合途径,以及复杂的营养和代谢通路,为 HS 生理活性作用机制和农业生产应用的研究提供理论依据。     

In situ studies of chemistry and structure of materials in reactive environments

Most materials and devices typically operate under specific environmental conditions, many of them highly reactive. Heterogeneous catalysts, for example, work under high pressure of reactants or in acidic solutions. The relationship between surface structure and composition of materials during operation and their chemical properties needs to be established in order to understand the mechanisms at work and to enable the design of new and better materials. Although studies of the structure, composition, chemical state, and phase transformation under working conditions are challenging, progress has been made in recent years in the development of new techniques that operate under a variety of realistic environments. With them, new chemistry and new structures of materials that are only present under reaction conditions have been uncovered.     

Effect of Humulus scandens for Traditional Fiber Sources on Digestion, Diarrhea, and Performance of Growing Rabbits

This work was to determine which concentration of a mixture of fresh Humulus scandens （HS） and fresh alfalfa could be included in diets for rabbits. The fresh forage of three experimental diets is composed of 100% alfalfa, 50% alfalfa ＋ 50% HS, 100% HS, respectively. 30 rabbits [（1.42 ± 0.056） kg] were used to determine nutrient digestibility. A feeding trial was carried out using 90 weaning rabbits [35 d of age; （512±6.5） g]. Increasing content of HS in the diet did not affect digestibility of DM （dry matter）, CF （crude fiber）, CP （crude protein）, GE （gross energy）, and EE （ether extract）. But diarrhea decreased markedly （P〈0.01） compared with the diets that had no HS. ADF1 （average daily feed intake） increased by 4.3% （P 〈 0.05） and 3.6% （P 〈 0.05） when rabbits fed the diet with 100% HS of fresh forage compared with the diets containing 0 and 50% HS, respectively. Feed efficiency improved significantly （P 〈 0.05） by 2.07 and 5.30% when rabbits fed 0 and 50% HS of fresh forage, respectively, compared with 100% HS. There was no effect on ADG （average daily weight gain）. In conclusion, the mixture （50：50） of HS and alfalfa constitutes an alternative source of fiber for fattening rabbits and prevents diarrhea effectively.     

Electrodeposited defect chemistry superlattices

Nanometer-scale layered structures based on thallium(III) oxide were electrodeposited in a beaker at room temperature by pulsing the applied potential during deposition. The conducting metal oxide samples were superlattices, with layers as thin as 6.7 nanometers. The defect chemistry was a function of the applied overpotential: High overpotentials favored oxygen vacancies, whereas low overpotentials favored cation interstitials. The transition from one defect chemistry to another in this nonequilibrium process occurred in the same potential range (100 to 120 millivolts) in which the rate of the back electron transfer reaction became significant. The epitaxial structures have the high carrier density and low electronic dimensionality of high transition temperature superconductors.     

A thiosulfate shunt in the sulfur cycle of marine sediments

The oxidation of sulfide, generated by bacterial sulfate reduction, is a key process in the biogeochemistry of marine sediments, yet the pathways and oxidants are poorly known. By the use of (35)S-tracer studies of the S cycle in marine and freshwater sediments, a novel shunt function of thiosulfate (S(2)O(3)(2-)) was identified. The S(2)O(3)(2-) constituted 68 to 78 percent of the immediate HS(-)-oxidation products and was concurrently (i) reduced back to HS(-), (ii) oxidized to SO(4)(2-), and (iii) disproportionated to HS(-) + SO(4)(2-). The small thiosulfate pool is thus involved in a dynamic HS(-) - S(2)O(3)(2-) cycle in anoxic sediments. The disproportionation of thiosulfate may help account for the large difference in isotopic composition ((34)S/(32)S) of sulfate and sulfides in sediments and sedimentary rocks.     

Mammalian brain morphogenesis and midline axon guidance require heparan sulfate

Heparan sulfate (HS) is required for morphogen signaling during Drosophila pattern formation, but little is known about its physiological importance in mammalian development. To define the developmental role of HS in mammalian species, we conditionally disrupted the HS-polymerizing enzyme EXT1 in the embryonic mouse brain. The EXT1-null brain exhibited patterning defects that are composites of those caused by mutations of multiple HS-binding morphogens. Furthermore, the EXT1-null brain displayed severe guidance errors in major commissural tracts, revealing a pivotal role of HS in midline axon guidance. These findings demonstrate that HS is essential for mammalian brain development.     

农业院校应用化学专业学生的能力培养问题及对策

提出农业院校应用化学专业学生的能力培养所存在的问题，全面分析当今农业院校应用化学专业学生的能力培养的制约因素，并提供相关的解决对策。     

Chemical composition and in vitro fermentation characteristics of high sugar forage sorghum as an alternative to forage maize for silage making in Tarim Basin,China

The chemical composition, mineral profile and in vitro fermentation characteristics of maize(MZ), high sugar forage sorghum(HS) and forage sorghum(FS), and silages made from each forage type were measured. The MZ and MZ silage(MZS) had higher crude protein, starch and ether extract contents than both sorghum forages and sorghum silages. HS had higher ash and water-soluble carbohydrate concentrations than FS and MZ. MZ, MZS, HS and HS silage(HSS) had lower neutral detergent fibre, acid detergent fibre and acid detergent lignin than FS and FS silage(FSS). FSS had higher dry matter(DM) and p H than MZS and HSS. HSS contained higher concentrations of P and K than FSS and MZS. MZS and HSS had higher in vitro dry matter and organic matter digestibility, CH4 production, total volatile fatty acids, acetate and propionate than FSS. p H was higher for FSS than for HSS, and ammonia was lower for HSS than for MZS and FSS. HSS had higher gas production than MZS and FSS after 2, 4, 6 and 8 h incubation. MZS had higher gas production than HSS and FSS after 26 and 28 h of incubation. The results indicate that HS may substitute for MZ to make good quality silage. However, animal studies are needed to assess the acceptability and feeding values of HSS vs. MZS for ruminant production.     

Spectral reflectance indices as proxies for yield potential and heat stress tolerance in spring wheat: heritability estimates and marker-trait associations

The application of spectral reflectance indices (SRIs) as proxies to screen for yield potential (YP) and heat stress (HS) is emerging in crop breeding programs. Thus, a comparison of SRIs and their associations with grain yield (GY) under YP and HS conditions is important. In this study, we assessed the usefulness of 27 SRIs for indirect selection for agronomic traits by evaluating an elite spring wheat association mapping initiative (WAMI) population comprising 287 elite lines under YP and HS conditions. Genetic and phenotypic analysis identified 11 and 9 SRIs in different developmental stages as efficient indirect selection indices for yield in YP and HS conditions, respectively. We identified enhanced vegetation index (EVI) as the common SRI associated with GY under YP at booting, heading and late heading stages, whereas photochemical reflectance index (PRI) and normalized difference vegetation index (NDVI) were the common SRIs under booting and heading stages in HS. Genome-wide association study (GWAS) using 18704 single nucleotide polymorphisms (SNPs) from Illumina iSelect 90K identified 280 and 43 marker-trait associations for efficient SRIs at different developmental stages under YP and HS, respectively. Common genomic regions for multiple SRIs were identified in 14 regions in 9 chromosomes: 1B (60–62 cM), 3A (15, 85–90, 101– 105 cM), 3B (132–134 cM), 4A (47–51 cM), 4B (71– 75 cM), 5A (43–49, 56–60, 89–93 cM), 5B (124–125 cM), 6A (80–85 cM), and 6B (57–59, 71 cM). Among them, SNPs in chromosome 5A (89–93 cM) and 6A (80–85 cM) were co-located for yield and yield related traits. Overall, this study highlights the utility of SRIs as proxies for GY under YP and HS. High heritability estimates and identification of marker-trait associations indicate that SRIs are useful tools for understanding the genetic basis of agronomic and physiological traits.     

耕作方式对小麦抗氧化酶和产量的影响

通过田间试验研究耕作方式对小麦根系、叶片抗氧化酶和产量的影响。试验设置耕翻+镇压（HS）、旋耕+镇压（RS）和旋耕（R）3个处理。结果表明,在拔节期、孕穗期和花后10 d HS处理叶片和根系超氧化物歧化酶（SOD）活性均显著高于其他2个耕作处理;在拔节期、抽穗期和花后5 d HS处理根系过氧化物酶（POD）活性均显著高于RS和R处理;在越冬期、孕穗期至花后5 d,HS处理叶片过氧化氢酶（CAT）活性均显著高于RS和R处理;除拔节期和孕穗期,HS处理叶片丙二醛（MDA）含量均显著低于RS和R处理。相关分析表明小麦产量和叶片CAT活性呈极显著正相关性（R=0.930,P＜0.01）,与叶片MDA含量呈显著负相关（R=-0.774,P＜0.05）。HS处理可以通过提高小麦有效穗数、穗粒数和千粒重从而提高产量,产量分别比RS和R处理高出5%和8%。综上表明,耕翻+镇压可提高小麦根系和叶片抗氧化酶活性,降低叶片MDA含量,延长小麦灌浆期实现小麦高产。     

茶叶化学研究中的方法与问题

就红茶发酵机理与色素形成、茶叶香气、茶叶有效成分的获取和利用及其他研究中所涉及的技术与思想方法、观点与争议进行了回顾和讨论 ,认为 :(1)作为实验性专业理论学科 ,茶叶化学进展一直受益于对“方法与问题”的关注 ;(2 )香气研究面临的理论与实践问题已不是缺乏对有关成分种类、含量、比例的认识 ,而是这些成分转化的化学机理及其获取的途径和方法 ;(3)酶学干预、苦涩味物质降解、鲜叶质量补救以及茶叶有效成分的提取、转化和添加是解决茶叶生产繁琐、成本偏高、质量波动及开发新型茶饮的关键技术之一     

镉胁迫下泥鳅肝脏的红外光谱研究

[目的]研究镉胁迫对泥鳅肝脏的影响。[方法]使用FTIR-NEXUSTM傅立叶变换红外光谱仪在1 800~400 cm-1范围内对泥鳅肝脏组织样品进行红外光谱扫描,将采集的红外光谱进行去卷积和曲线拟合处理后,分析Cd2+胁迫下泥鳅肝脏组织中相应大分子化合物特征基团的变化趋势。[结果]在Cd2+胁迫作用下,蛋白质、核酸的结构及合成途径都发生了明显变化。[结论]FTIR技术在动物抗逆研究及环境监测方面具有广泛的应用价值。