秦岭山地松栎混交林主要木本植物组成及更新特征

采用样方法对秦岭南坡中段松栎混交林主要木本植物组成及天然更新特征进行了研究.结果表明:(1)松栎混交林乔木层物种共计40种,油松、锐齿槲栎和华山松为优势种,重要值分别为35.19％、31.99％和8.12％,漆树、栓皮栎和楝木为亚优势种.(2)更新层木本植物共计87种,其中乔木幼苗34种,占总数的39.08％,灌木物种也有一定优势地位,优势种有锐齿槲栎、悬钩子和菝葜等,高度级较小的更新苗在群落内占有较大比例.(3)优势乔木更新特征不同,锐齿槲栎幼苗和幼树密度显著高于油松和华山松,且锐齿槲栎幼苗密度显著高于其幼树,但油松幼苗与幼树、华山松幼苗与幼树间无明显差异.(4)混交林内锐齿槲栎径级结构呈近似倒“J”形分布,种群稳定;油松和华山松种群均呈近似正态分布,大径级个体群相对稳定,但林下幼树不足.该研究结果提示,松栎混交林下油松和华山松更新不良,这将不利于其长期存留于群落中,虽然锐齿槲栎从幼苗到幼树的发育过程中存在更新障碍,但并未影响其种群整体更新,若无大规模干扰,锐齿槲栎将维持逆“J”型的更新方式并成为松栎混交林群落中的第一优势种.     

小钻‘白城杨2号’小孢子发生及花粉大小变异

利用醋酸洋红染色压片技术,以温室水培小钻‘白城杨2号’(Populus×xiaozhuanica W.Y.Hsu et Liangcv.‘Baicheng-2’)为材料,对其小孢子发生过程中染色体行为及花粉大小变异进行研究。结果表明:(1)‘白城杨2号’小孢子母细胞减数分裂过程中染色体行为存在一定比例的异常现象,包括终变期单价体、中期Ⅰ染色体提前分离、后期Ⅰ和Ⅱ落后染色体和染色体桥、末期Ⅰ和Ⅱ微核、中期Ⅱ纺锤体定位异常以及胞质分裂异常等,这些异常现象的发生与‘白城杨2号’杂种起源有密切关系。(2)‘白城杨2号’小孢子母细胞减数分裂过程中核仁数目存在动态变化,末期Ⅰ和Ⅱ的子核中最多可看到8个小核仁,可能与杨属树种的多倍体起源有关,其染色体组中可能包含8对具核仁组织者区的染色体。(3)‘白城杨2号’产生空瘪花粉率为3.67%,饱满花粉直径在21.3～52.2μm之间,频率分布总体呈近似高斯分布,0.69%的花粉直径超过37μm,表明其可能产生少量未减数的2n花粉。     

不同品种万寿菊对镉胁迫的生长和生理响应

以6个万寿菊品种为研究对象,研究了不同浓度的重金属镉（Cd）胁迫（0、200、400、600 mg/L）对万寿菊基径、株高以及百叶重、茎叶重和单花质量等生长指标及其质膜透性（丙二醛、相对电导率）、保护酶活性（SOD、POD、CAT、APX）以及光合特性(叶绿素含量、净光合速率、气孔导度、蒸腾速率、水分利用效率)等生理指标的影响。结果显示:(1)低于400 mg/L的Cd胁迫对6个万寿菊品种的基径、株高无明显影响,而百叶重、茎叶重和单花质量却随着Cd浓度的增加显著降低,尤其是‘大英雄’和‘迪阿哥’2个品种表现的抗性较差。(2)随着Cd胁迫浓度的增加,各品种丙二醛（MDA）含量和相对电导率（REC）显著增加,而其保护酶活性不同程度降低。(3)Cd胁迫降低了万寿菊的叶绿素Chl a+b含量和Chl a/b,且抗性差的品种降低的幅度更大;叶片净光合速率（Pⁿ）明显降低,但蒸腾速率(T^r)和气孔导度(G^s)相对降幅较小,对水分利用效率（WUE）影响较小。研究表明,不同品种万寿菊对Cd毒害响应存在明显的差异,且Cd胁迫下生理响应的差异是品种间耐性差异的重要原因之一;抗性差的品种在高浓度Cd胁迫下,光合作用能力降低,抗氧化系统酶的活性受到显著抑制,膜质过氧化加剧,且品种‘珍妮’和‘金门’的抗性强于其他品种,可选择作为Cd污染区栽植植物。     

采用磁微粒分离酶联免疫法构建基于KGN细胞的雌激素生物合成筛选模型

雌激素在机体生长发育中发挥着重要作用,其合成代谢紊乱会导致乳腺癌和骨质疏松等疾病发生.目前,基于细胞的雌激素合成筛选模型需用到放射性底物,对环境污染大,成本较高,限制了具有组织特异性调控雌激素合成的药物筛选.我们以高表达芳香化酶的KGN细胞为检测对象,比较基于聚苯乙烯酶联免疫法和磁微粒分离酶联免疫法的雌二醇ELISA试剂盒的交叉反应和灵敏度,发现相对于聚苯乙烯酶联免疫法,磁微粒分离酶联免疫法能够稳定高效的检测雌激素合成.进一步比较培养基中酚红和底物睾酮对雌二醇检测的影响,成功建立通过磁微粒酶联免疫法检测KGN细胞雌二醇合成的筛选模型.     

Variations and evolution of polyubiquitin genes from ciliates

Polyubiquitin genes from seven ciliate species were amplified, cloned and sequenced. It is estimated that Strombidium sulcatum, Euplotes vannus, E. rariseta and Anteholosticha manca have a polyubiquitin gene of 3 repeats, and A. parawarreni, Paramecium caudatum and Pseudokeronopsis flava 4 repeats. The newly obtained ubiquitins mostly differ from that of humans by 1–5 residues in amino acid sequences. A neighbor-joining tree constructed based on monomeric ubiquitin genes supports the monophyly of an assemblage comprising the litostomateans and some oligohymenophoreans, but not the class Spirotrichea. The monomers from the same species are generally placed together and highly supported for the class Litostomatea, the genera Paramecium and Ichthyophthirius, but not for other species. The non-synonymous/synonymous rate ratio (dN/dS) at the protein level are less than 1, and the synonymous nucleotide differences per synonymous site (p_S) from intraspecific comparisons are fairly high (0.02–0.72). These results indicate that ciliates have not only the conserved, but also some quite divergent, polyubiquitin genes and confirm that the polyubiquitin genes in ciliates evolve according to the birth-and-death mode of evolution under strong purifying selection.     

Altitudinal variation in growth, photosynthetic capacity and water use efficiency of Abies faxoniana Rehd. et Wils. seedlings as revealed by reciprocal transplantations

Altitudinal variation in morphological, physiological and biochemical characteristics between two provenances of Abies faxoniana Rehd. et Wils. from contrasting elevations (3,500 and 2,850 m) was investigated by reciprocal transplantations in the eastern Qinghai-Tibetan Plateau. From each altitude, 54 seedlings were selected, of which 27 seedlings were simply transplanted at their original altitude, while the other 27 seedlings were reciprocally transplanted to another altitude. The results showed that there is evident altitudinal variation in growth, photosynthetic capacity and water use efficiency among A. faxoniana seedlings. Transplantation of seedlings to a lower altitude decreased the leaf pigment content, leaf N content and water use efficiency, but increased CE, P _n, LMR and PNUE, consequently promoting NAR, the biomass accumulation and branchlet length increment. Besides, the increase in the C/N ratio reduced the risk of pathogen attack. Based on the substantial plasticity in the responses of the seedlings, we infer that the ongoing climate warming might facilitate the growth of A. faxoniana seedlings at high altitudes.     

Triple mutated antibody scFv2F3 with high GPx activity: insights from MD, docking, MDFE, and MM-PBSA simulation

By combining computational design and site-directed mutagenesis, we have engineered a new catalytic ability into the antibody scFv2F3 by installing a catalytic triad (Trp²⁹–Sec⁵²–Gln⁷²). The resulting abzyme, Se-scFv2F3, exhibits a high glutathione peroxidase (GPx) activity, approaching the native enzyme activity. Activity assays and a systematic computational study were performed to investigate the effect of successive replacement of residues at positions 29, 52, and 72. The results revealed that an active site Ser⁵²/Sec substitution is critical for the GPx activity of Se-scFv2F3. In addition, Phe²⁹/Trp–Val⁷²/Gln mutations enhance the reaction rate via functional cooperation with Sec⁵². Molecular dynamics simulations showed that the designed catalytic triad is very stable and the conformational flexibility caused by Tyr¹⁰¹ occurs mainly in the loop of complementarity determining region 3. The docking studies illustrated the importance of this loop that favors the conformational shift of Tyr⁵⁴, Asn⁵⁵, and Gly⁵⁶ to stabilize substrate binding. Molecular dynamics free energy and molecular mechanics-Poisson Boltzmann surface area calculations estimated the pK _a shifts of the catalytic residue and the binding free energies of docked complexes, suggesting that dipole–dipole interactions among Trp²⁹–Sec⁵²–Gln⁷² lead to the change of free energy that promotes the residual catalytic activity and the substrate-binding capacity. The calculated results agree well with the experimental data, which should help to clarify why Se-scFv2F3 exhibits high catalytic efficiency.     

A New Natural Quinone, 2-Methyl-3-II,III,VIII,IX-octahydromultiprenyl9-1,4-naphthoquinone Isolated from Streptomyces albus

Purification of the precipitates obtained from the juice oil of Citrus hassaku by chromatography afforded 7-geranyloxycoumarin (aurapten) and two compounds (mp 43~45°C and 122~124°C), whose structures were determined to be epoxyaurapten and marmin on the basis of spectral evidence. These compounds were isolated from Citrus hassaku for the first time. The spasmolytic activity was tested of aurapten, epoxyaurapten, marmin and their related compounds, which were synthesized from aurapten and marmin, on the small intestine removed from a male guinea pig. Epoxyaurapten exhibited the highest activity among them against the small intestine’s contraction induced by BaCl₂.     

Characterization of saponins and phenolic compounds: antioxidant activity and inhibitory effects on α-glucosidase in different varieties of colored quinoa (Chenopodium quinoa Willd)

ABSTRACT

This study investigated the contents of saponins and phenolic compounds in relation to their antioxidant activity and α-glucosidase inhibition activity of 7 colored quinoa varieties. The total saponin content was significantly different among 7 varieties and ranged from 7.51 to 12.12 mg OAE/g DW. Darker quinoa had a higher content of phenolic compounds, as well as higher flavonoids and antioxidant activity than that of light varieties. Nine individual phenolic compounds were detected in free and bound form, with gallic acid and ferulic acid representing the major compounds. The free and bound phenolic compounds (gallic acid and ferulic acid in particular) exhibited high linear correlation with their corresponding antioxidant values. In addition, the free phenolic extracts from colored quinoa exhibited higher inhibitory activity against α-glucosidase than the bound phenolic extracts. These findings imply that colored quinoa with abundant bioactive phytochemicals could be an important natural source for preparing functional food.