Anion directed template synthesis of Cu(II) complexes of a N,N,O donor mono-condensed Schiff base ligand: A molecular scaffold forming highly ordered H-bonded rectangular grids

Anion directed, template syntheses of two dinuclear copper(II) complexes of mono-condensed Schiff base ligand Hdipn (4-[(3-aminopentylimino)-methyl]-benzene-1,3-diol) involving 2,4-dihydroxybenzaldehyde and 1,3-diaminopentane were realized in the presence of bridging azide and acetate anions. Both complexes, [Cu₂(dipn)₂(N₃)₂] (1) and [Cu₂(dipn)₂(OAc)₂] (2) have been characterized by X-ray crystallography. The two mononuclear units are joined together by basal-apical, double end-on azido bridges in complex 1 and by basal-apical, double mono-atomic acetate oxygen-bridges in 2. Both complexes form rectangular grid-like supramolecular structures via H-bonds connecting the azide or acetate anion and the p-hydroxy group of 2,4-dihydroxybenzaldehyde. Variable-temperature (300-2 K) magnetic susceptibility measurements reveal that complex 1 has antiferromagnetic coupling (J = −2.10 cm⁻¹) through the azide bridge while 2 has intra-dimer ferromagnetic coupling through the acetate bridge and inter-dimer antiferromagnetic coupling through H-bonds (J = 2.85 cm⁻¹, J′ = −1.08 cm⁻¹).     

Production of polyhydroxyalkanoates from inexpensive extruded rice bran and starch by Haloferax mediterranei

Low-cost raw materials can be used to reduce significantly the production cost of polyhydroxyalkanoates (PHA). In this study, extruded rice bran (ERB) and extruded cornstarch (ECS) were used as carbon sources to produce PHA by an archaea, Haloferax mediterranei, which cannot use native rice bran or cornstarch as a carbon source. By employing pH-stat control strategy to maintain pH at 6.9–7.1 in a 5-liter jar fermentor using ERB:ECS (1:8 g/g) as the major carbon source, we obtained a cell concentration of 140 g/L, PHA concentration of 77.8 g/L and PHA content of 55.6 wt.% in a repeated fed-batch fermentation. In contrast, when ECS was used as the major carbon source, we obtained 62.6 g/L cell concentration, 24.2 g/L PHA concentration and 38.7 wt.% PHA content. Under a hyper-saline condition and with no nitrogen-limitation restriction, the repeated fed-batch process can be sustained a long time for the mass production of PHA.     

Counting mtDNA molecules in <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis>: sublimons are constantly produced by recombination via short repeats and undergo rigorous selection during substoichiometric shifting

Sublimons are substoichiometric DNA molecules which are generated by recombinations across short repeats, located in main mitochondrial genome of plants. Since short repeats are believed to recombine irreversibly and to be usually inactive, it is unknown how substoichiometric sequences are maintained. Occasionally, sublimons are amplified during substoichiometric shifting (SSS) and take the role of the main genome. Using the Phaseolus vulgaris system, we have addressed the questions concerning accumulation of sublimons, the role of recombination in their maintenance and selective amplification during SSS. We found that sublimons accompanied by parental recombination sequences were maintained by constant recombination across a short 314-bp repeat. The abundance of these sublimons was three orders of magnitude higher than accumulation of those which could not be maintained by recombination because their parental forms were absent from the main genome. As expected for active recombination, two recombination-derived sublimons were equimolar and so were their parental forms. One parental and one substoichiometric form shared the A/C polymorphism indicating their frequent inter-conversion. Only the C variant of the sublimon was amplified during substoichiometric shift implying strong selection of DNA molecules operating during SSS.     

Direct observation of stepped proteolipid ring rotation in E. coli F₀F₁-ATP synthase

Although single‐molecule experiments have provided mechanistic insight for several molecular motors, these approaches have proved difficult for membrane bound molecular motors like the F_oF₁‐ATP synthase, in which proton transport across a membrane is used to synthesize ATP. Resolution of smaller steps in F_o has been particularly hampered by signal‐to‐noise and time resolution. Here, we show the presence of a transient dwell between F_o subunits a and c by improving the time resolution to 10 μs at unprecedented S/N, and by using Escherichia coli F_oF₁ embedded in lipid bilayer nanodiscs. The transient dwell interaction requires 163 μs to form and 175 μs to dissociate, is independent of proton transport residues aR210 and cD61, and behaves as a leash that allows rotary motion of the c‐ring to a limit of ～36° while engaged. This leash behaviour satisfies a requirement of a Brownian ratchet mechanism for the F_o motor where c‐ring rotational diffusion is limited to 36°.     

PBL教学法在医学微生物学中的应用探索与体会

在医学微生物学教学改革实践中,对传统讲授式教学与PBL教学进行比较。结果显示PBL法教学组学生的分析题成绩、理论成绩、总成绩均比传统讲授教学组好,差异有高度显著性(P<0.01)。在PBL实践过程中发现影响其教学效果的主要因素有:教师和学生角色转变的困难;学生易受非重要问题的困扰;时间和硬件设备的缺乏;考核方式不完善。由此,提出相应的对策,以获得更好的教学效果。     

应用Coriolus vericolor 菌丝球脱色染料及印染废水的研究

对白腐真菌（Coriolus vericolor）产生漆酶进行了研究。发现该菌产漆酶的最适初始pH值为4．5。提高微量元素浓度或添加藜芦醇都可使C.versiclor的产酶能力增加,添加Tween80会有一定的抑制作用。采用C.versicolor菌丝球进行重复分批产酶试验,结果表明菌丝球的稳定性很好,同一批菌丝球可连续利用14次,平均每批酶活力可保持在6．72U／mL,产酶能力优于聚氨酯泡沫固定化菌丝。将粗酶液用要料的脱色降解试验,在酶活力为3．3IU／mL,酸性橙浓度为500mg/L条件下,经过24h反应,脱色率达到98．5％;对含弱酸大红和卡布龙红的印染废水进行脱色试验,脱色率也达到了93％。     

The strength of negative plant–soil feedback increases from the intraspecific to the interspecific and the functional group level

One of the processes that may play a key role in plant species coexistence and ecosystem functioning is plant–soil feedback, the effect of plants on associated soil communities and the resulting feedback on plant performance. Plant–soil feedback at the interspecific level (comparing growth on own soil with growth on soil from different species) has been studied extensively, while plant–soil feedback at the intraspecific level (comparing growth on own soil with growth on soil from different accessions within a species) has only recently gained attention. Very few studies have investigated the direction and strength of feedback among different taxonomic levels, and initial results have been inconclusive, discussing phylogeny, and morphology as possible determinants. To test our hypotheses that the strength of negative feedback on plant performance increases with increasing taxonomic level and that this relationship is explained by morphological similarities, we conducted a greenhouse experiment using species assigned to three taxonomic levels (intraspecific, interspecific, and functional group level). We measured certain fitness‐related aboveground traits and used them along literature‐derived traits to determine the influence of morphological similarities on the strength and direction of the feedback. We found that the average strength of negative feedback increased from the intraspecific over the interspecific to the functional group level. However, individual accessions and species differed in the direction and strength of the feedback. None of our results could be explained by morphological dissimilarities or individual traits. Synthesis. Our results indicate that negative plant–soil feedback is stronger if the involved plants belong to more distantly related species. We conclude that the taxonomic level is an important factor in the maintenance of plant coexistence with plant–soil feedback as a potential stabilizing mechanism and should be addressed explicitly in coexistence research, while the traits considered here seem to play a minor role.     

棕背伯劳羽色多态现象探讨

羽色多态现象的研究对了解物种的遗传、变异和进化有着重要意义。棕背伯劳(Lanius schach)具有典型的羽色多态现象。结合华南濒危动物研究所馆藏标本和2005年4月—2007年1月间的野外调查,分析棕背伯劳棕色型和黑色型在形态和地理分布上的差异性后,得到的结果如下:1)广东可能存在与棕色型、黑色型相区别的一种新色型——黑色白边型,该色型全身以黑色为主,但具多枚白色飞羽;2)棕色型与黑色型各身体量度均无显著性差异(P>0.05);3)野外种群中棕色型为优势色型,黑色型多集中于沿海地区而山区未有发现,黑色白边型仅在沿海的海丰县被发现。据此认为新色型的出现说明沿海可能是黑色型分化的重要地区,且色型的分化仍在进行中。     

人脐带间充质干细胞静脉输注小鼠的安全性

目的探讨C57／BL6J小鼠重复多次尾静脉输注人脐带间充质干细胞后的免疫反应和毒性。方法将SPF级别的32只C57／BL6J小鼠随机分为阴性对照组、细胞移植组,每组16只,雌雄各半,细胞移植组小鼠尾静脉注射分离培养的第5代人脐带间充质干细胞,一次5×10。／只,每周注射一次,连续注射4周;阴性对照组每次注射相同容积的PBS。注射后后观察小鼠的一般症状,末次注射后i周、4周进行血细胞计数、血生化、免疫反应指标、脏器质量测定和组织病理学检查。结果细胞移植组小鼠血细胞计数、血生化、脏器重量和脏器系数与对照组无显著性差异（P〉0．05）,脏器组织病理学在光镜下检查结果与对照组无形态学差别,以及免疫结果测定（T细胞亚群CD3＋、CD4＋、CD8＋及CD4＋／CD8＋）与对照组无显著性差异（P〉0．05）。结论人脐带间充质干细胞重复多次尾静脉输注C57／BL6J小鼠是安全可行的,对受者无明显免疫反应和毒副作用。     

连栽杉木林的根系研究

 本文通过对福建三明连栽杉木林的根系进行了调查研究。结果表明：连栽林地上的根系重量、组成、形态和分布发生较大的差异,第一代杉木林地的单株根量分别比第二代、第三代高出24.93%、49.69%,全林分别为31.93%、55.22%;第一代的杉木林根系的组成和分布较合理,营养空间大,利于杉木的生长发育。