Fluorescence properties of calmodulin-binding peptides reflect alpha-helical periodicity

A basic amphiphilic alpha-helix is a structural feature common to many calmodulin-binding peptides and proteins. A set of fluorescent analogues of a very tight binding inhibitor (dissociation constant of 200 picomolar) of calmodulin has been synthesized. The fluorescent amino acid tryptophan has been systematically moved throughout the sequence of this peptide. The fluorescence properties for the peptides repeat every three to four residues and are consistent with the periodicity observed for an alpha-helix.     

蛴螬抗菌肽的制备及其稳定性研究

使用酶解法制备对金黄色葡萄球菌和大肠杆菌都有抑制活性的小分子抗菌肽,以解决滥用抗生素饲料添加剂导致的抗药性和药物残留问题。实验通过单因素分析法和正交实验法,以加酶量、酶解时间、料液比和酶解pH 4个因素,优化制备蛴螬抗菌肽的条件。结果表明,胰蛋白酶为最适合用于制备蛴螬抗菌肽的蛋白酶,制备抗菌肽的最佳酶解条件为:加酶量50.00 ku/g,酶解时间90 min,料液比1∶10(g/mL)和酶解pH 7.50。酶解产物对金黄色葡萄球菌和大肠杆菌的抑制作用最强,抑菌圈直径分别为11.50、8.70 mm。稳定性实验结果表明,蛴螬抗菌肽的最佳作用pH为6.00,高温环境下具有稳定的抑菌效果,对于不同的实验菌,盐浓度对抗菌肽的抑菌效果影响不同;蛴螬抗菌肽具有较好的胰蛋白酶水解稳定性,但不具有胃蛋白酶水解稳定性。制备得到的蛴螬蛋白酶解产物有抗菌效果,可以在农业、医药、食品、畜牧业等领域发挥重要作用。     

农业结构调整连锁系数分析

应用投入产出模型的连锁系数分析法，对河南１９９２￣１９９７年间农业结构调整的现状及存在问题进行了分析。结果表明，从农业结构分析，农业的感应度系数和影响力系数都在逐年增大，畜牧业、渔业和其他农业的ＦＥ值均大于１，特别是畜牧业值最大，发展畜牧业将会对国民经济产生较强的拉动作用。     

Sulfur dioxide contributions to the atmosphere by volcanoes

The first extensive measurements by remote-sensing correlation spectrometry of the sulfur dioxide emitted by volcanic plumes indicate that on the order of 10(3) metric tons of sulfur dioxide gas enter the atmosphere daily from Central American volcanoes. Extrapolation gives a minimum estimate of the annual amount of sulfur dioxide emitted from the world's volcanoes of about 10(7) metric tons.     

糖基化卵白蛋白结构及其凝胶稳定性关系的研究

糖基化卵白蛋白不但具有优越的凝胶性,还有良好的凝胶稳定性。本项目以天然态卵白蛋白为对照,融球态卵白蛋白为参比,糖基化卵白蛋白为研究对象,探讨了其结构和凝胶稳定性的关系。通过电镜扫描可以看出,糖基化卵白蛋白结构更规则、均匀。拉曼光谱分析结果表明:糖基化卵白蛋白在3 000cm-1左右有个特征峰。基质辅助解析电离飞行质谱图可以看出,糖基出现在质核比在2 500~4 300的区域。     

Three-dimensional structure of yeast phenylalanine transfer RNA: folding of the polynucleotide chain

At 4 A resolution the polynucleotides in yeast phenylalanine transfer RNA are seen in a series of electron dense masses about 5.8 A apart. These peaks are probably associated with the phosphate groups, while lower levels of electron density between segments of adjacent polynucleotide chains are interpreted as arising from hydrogen-bonded purine-pyrimidine base pairs. It is possible to trace the entire polynucleotide chain with only two minor regions of ambiguity. The polynucleotide chain has a secondary structure consistent with the cloverleaf conformation; however, its folding is different from that proposed in any model. The molecule is made of two double-stranded helical regions oriented at right angles to each other in the shape of an L. One end of the L has the CCA acceptor; the anticodon loop is at the other end, and the dihydrouridine and TpsiC loops form the corner.     

大型海藻对海水水族箱生态微宇宙结构及稳定性的影响

稳定高效的多营养层级景观生态系统构建是近年来水族行业的发展热门,为探究海水水族箱在引入大型海藻后微宇宙生态系统结构和稳定性的变化,分别对不同处理组进行水质指标、浮游生物及细菌群落结构分析。结果表明：（1）有藻组水体溶解氧（DO）含量和pH上升趋势高于无藻组,并可维持亚硝态氮（NO2--N）含量在较低水平,实验结束时磷酸盐（PO43--P）及铵态氮（NH4+-N）含量显著低于无藻组（P < 0.05）。（2）有藻组细菌多样性及均匀度指数显著低于无藻组（P < 0.05）;浮游生物群落均匀度指数存在显著组间差异（P < 0.05）。（3）细菌群落结构分析结果显示,无藻及有藻组第一、二优势菌门均为变形菌门（Proteobacteria）、放线菌门（Actinobacteria）,无生物对照组分别为变形菌门和厚壁菌门（Firmicutes）;各处理组浮游生物群落的第一优势门均为硅藻门（Bacillariophyta）,至少占样品中浮游生物群落丰度的40%以上,第一优势属均为直链藻属（Melosira）。（4）CCA结果显示,无藻组微生物优势种丰度与营养盐含量呈正相关关系,与溶解氧（DO）及pH负相关,有藻组则相反。通过以上结果可推测,不同营养层级的微宇宙系统浮游生物及细菌群落组成不同,培养针叶蕨藻（Caulerpa sertularioides）能有效改善生态水族箱水质环境并影响水体微宇宙结构,有利于构建稳定高效并美观的海水景观生态系统。     

水铁矿结构稳定性及对砷固定研究与展望

水铁矿是砷污染土壤和水体修复中最常用、最有效的钝化剂。水铁矿等铁氧化物对砷的赋存形态和生物有效性具有显著影响,并对环境中的砷具有很强的固定作用;但水铁矿在环境中容易转化,极大地影响了其对砷固定的效果。基于此,本文从水铁矿的结构及影响其稳定性因素的分析入手,综述了水铁矿与砷的交互作用,探讨其在修复砷污染土壤方面的可行性,旨在为利用水铁矿修复砷污染土壤提供理论依据。同时,从降低农田中砷有效性等角度,对砷污染农田修复和安全利用技术与方法等进行了讨论。     

我国荔枝供应链结构与物流模式分析

物流模式对荔枝的销售乃至荔枝产业的发展有着非常重要的影响。在理论分析和实际调研的基础上,分析了我国新鲜荔枝的供应链结构和特征,比较了常温物流模式、"土法"冷链物流模式和冷藏保温冷链物流模式等3种主要的荔枝物流模式,提出了我国荔枝物流存在的主要问题,包括荔枝冷链物流体系不完善、荔枝冷链物流技术落后、荔枝物流成本较高。最后,提出了加强荔枝供应链管理,推动农产品冷链物流补贴、减免费用和政策倾斜,完善荔枝冷链物流系统等建议。     

论李大钊对图书馆事业发展的卓越贡献

从图书馆社会教育职能、图书馆专业人才培养、读者服务工作等方面,阐述了李大钊的图书馆学理论及实践对图书馆事业发展的影响。

     

略论建国初期的“一边倒”外交政策

1949年6月30日,以毛泽东同志为核心的党中央宣布新中国将会奉行“一边倒“外交政策。这一政策的形成有着极为深刻的历史原因。它对新中国的发展具有重要影响。一方面,它对新中国人民民主政权的巩固和国民经济的恢复起了积极作用,另一方面,它也给我们留下了丰富的经验和教训。分析其成因并对其作出科学评价,从而吸取经验教训,这对我们今后外交政策的取向具有重要意义。     

A brief history of Drosophila's contributions to genome research

The sequence of the Drosophila melanogaster genome presented in this issue of Science is the latest milestone in nine decades of research on this organism. Genetic and physical mapping, whole-genome mutational screens, and functional alteration of the genome by gene transfer were pioneered in metazoans with the use of this small fruit fly. Here we look at some of the instances in which work on Drosophila has led to major conceptual or technical breakthroughs in our understanding of animal genomes.     

还少丹对老年小鼠脂褐素含量和 DNA分子结构稳定性的影响

〔摘要〕目的研究还少月一对老龄小鼠脂褐素含量和DNA分子结构稳定性的影响、方法将36只昆明种老年 小鼠(20月龄),按体质量随机分为3组,另设12只2月龄同种小鼠作为青年对照组,共4组:①老年对照组;②老 年还少月一组;③老年维生素E(VE)组;④青年对照组〔连续喂养10周后,采用荧光分光光度法测定脑组织的脂褐素 水平和肝组织DNA双链解旋剩余率;用紫外分光光度法测定肝组织DNA碱变性增色效应、结果青年对照组、老 年还少月一组、老年VE组的脂褐素含量明显低于老年对照组,差异有统计学意义(P<0.05;与老年对照组比较,青年 对照组和老年还少月一组的DNA碱变性增色效应明显降低,而DNA双链解旋剩余率显著增高,差异均具有统计学 意义(P<0.05,而老年VE组的差异无统计学意义(P>0.05、结论还少月一能有效降低脂褐素的含量,保护DNA结 构的稳定性,达到延缓衰老的目的、     

From the genome to the proteome: uncovering peptides in the Apis brain

Neuropeptides, critical brain peptides that modulate animal behavior by affecting the activity of almost every neuronal circuit, are inherently difficult to predict directly from a nascent genome sequence because of extensive posttranslational processing. The combination of bioinformatics and proteomics allows unprecedented neuropeptide discovery from an unannotated genome. Within the Apis mellifera genome, we have inferred more than 200 neuropeptides and have confirmed the sequences of 100 peptides. This study lays the groundwork for future molecular studies of Apis neuropeptides with the identification of 36 genes, 33 of which were previously unreported.     

框架边梁的抗扭计算与设计

根据Ｈｓｕ等人的研究结果，结合我国《检结构设计规范》（ＧＢＪ１０－８９），提出了框架边梁的附加扭矩计算公式，并明确了塑性设计法所确定的附加扭矩的含义，还给出了塑性状态下常用梁断面的附加扭矩值，以及结构构造要求，以供设计参考。     

Greenhouse gases in intensive agriculture: contributions of individual gases to the radiative forcing of the atmosphere

Agriculture plays a major role in the global fluxes of the greenhouse gases carbon dioxide, nitrous oxide, and methane. From 1991 to 1999, we measured gas fluxes and other sources of global warming potential (GWP) in cropped and nearby unmanaged ecosystems. Net GWP (grams of carbon dioxide equivalents per square meter per year) ranged from 110 in our conventional tillage systems to -211 in early successional communities. None of the annual cropping systems provided net mitigation, although soil carbon accumulation in no-till systems came closest to mitigating all other sources of GWP. In all but one ecosystem, nitrous oxide production was the single greatest source of GWP. In the late successional system, GWP was neutral because of significant methane oxidation. These results suggest additional opportunities for lessening the GWP of agronomic systems.     

Mammoth hair: stability of alpha-keratin structure and constituent proteins

Hair from a woolly mammoth (Mammuthus primigenius, age about 32,000 years) retains the ordered structure characteristic of alpha-keratins, but the proteins of this hair differ in composition from and are smaller than similar proteins isolated from other keratins, for example, elephant hair. It is suggested that these changes have been caused by limited proteolysis.     

Pollution aerosol in the northeast: northeastern-midwestern contributions

In recent years, atmospheric scientists have been endeavoring to determine the relative contributions of local and distant sources to pollution aerosol in eastern North America. Elemental analysis of aerosol from various sites in the northeastern United States has revealed a persistent northeastern "foreground" upon which pulses of midwestern aerosol are superimposed every few days, in response to large-scale meteorological features. Regional apportionment of tracer element and sulfate in summer and winter samples from Narragansett, Rhode Island, and Underhill, Vermont, shows that most of the elements come predominantly from northeastern sources. Notable exceptions include arsenic and indium, for which Canadian nonferrous smelters are important sources, and sulfur and selenium, for which the Midwest is an important source. During 1982 and 1983, the Northeast and the Midwest contributed comparably to aerosol sulfate at Narragansett and Underhill, in spite of the fact that the emissions of sulfur dioxide in the Midwest were ten times those in the Northeast; Canadian smelters accounted for less than 10 percent of the total sulfate. During a major pollution episode in July 1982, northeastern and midwestern sources produced comparable sulfate concentration in Rhode Island, whereas midwestern sources dominated northeastern sources in Vermont. Thus, although distant midwestern sources affect the quantity of pollution aerosol in the Northeast and may dominate episodically, nearer northeastern sources are comparably important on the long term.