甘南黄河流域4种典型林分土壤C、N、P化学计量特征

土壤碳（C）、氮（N）、磷（P）是参与植物光合作用和影响生态系统初级生产力的主要元素。甘南高原是黄河流域重要的生态屏障,为了解该区不同林分土壤养分状况的差异,选取该区4种典型林分：云杉林、华北落叶松林、巴山冷杉林以及岷江冷杉糙皮桦混交林为研究对象,研究土壤C、N、P化学计量特征。结果表明：（1）岷江冷杉及糙皮桦混交林土壤C、N含量最高,云杉林土壤N、P含量最低。不同林分间P含量差异显著（P<0.05）,不同土层间C、N含量差异均显著（P<0.05）。（2）云杉林土壤C ： N值显著高于其他林分,岷江冷杉及糙皮桦混交林土壤N ： P及C ： P高于其他林分。（3）海拔、土壤pH、容重与土壤含水量是影响土壤养分的重要因素。土壤C含量与N、P含量均显著相关（P<0.05）。总体来说,不同林分土壤化学计量特征具有显著差异,混交林土壤养分状况较纯林好,未来森林管理和植被建设中,可以通过选择合适的树种和提高树种多样性有效改善森林土壤质量。     

鼠李糖乳杆菌LV108及其发酵乳免疫调节作用的比较

目的探讨鼠李糖乳杆菌LV108及其发酵乳对免疫抑制小鼠免疫功能的调节作用。方法将BALB/c小鼠随机分为5组,每组10只,即空白组(正常小鼠)、模型组(免疫抑制小鼠)、药物组(免疫抑制小鼠食物中添加左旋咪唑)、LV108菌悬液组(免疫抑制小鼠食物中添加LV108菌悬液)和LV108发酵乳组(免疫抑制小鼠食物中添加LV108发酵乳),除空白组外其余组构建免疫抑制小鼠模型。干预4周后,分别测定各组小鼠体质量和脏器指数,血清中白细胞介素2(IL2)、肿瘤坏死因子α(TNFα)和免疫球蛋白G(IgG)含量,血清溶血素含量、耳肿胀度和肝、脾巨噬细胞吞噬能力。结果相比模型组,LV108菌悬液组和LV108发酵乳组小鼠体质量增长速度、脏器指数、血清IL2与IgG水平、血清溶血值、耳肿胀度和巨噬细胞吞噬能力显著升高(均P<0.05);在脾脏指数、血清IL2与TNFα水平、血清溶血素含量和耳肿胀度免疫指标上,LV108菌悬液组与LV108发酵乳组之间比较差异具有统计学意义(均P<0.05)。结论LV108菌体及发酵乳对免疫抑制小鼠具备较全面的免疫调节作用,均可提高小鼠的自身免疫力;LV108发酵乳对小鼠的免疫调节作用强于LV108菌体。     

Non-empirical study of the phosphorylation reaction catalyzed by 4-methyl-5-β-hydroxyethylthiazole kinase: relevance of the theory of intermolecular interactions

The subject of this study was an analysis of the role of active site residues in the phosphoryl transfer reaction catalyzed by 4-methyl-5-β-hydroxyethylthiazole kinase (ThiK). The ThiK-catalyzed reaction is of special interest due to the lack of a highly conserved aspartate residue serving as a catalytic base. ONIOM(B3LYP:PM3) models of stationary points along the reaction pathway consisted of reactants, two magnesium ions and several highly conserved ThiK active site residues. The results indicate that an S_N2-like mechanism of ThiK, with γ-phosphate acting as an alcohol-activating base is reasonable. Geometries of substrates, transition state and products were utilized in the non-empirical analysis of the physical nature of catalytic interactions taking place in the ThiK active site. The role of particular residues was investigated in terms of their ability to preferentially stabilize the transition state relative to substrates (differential transition state stabilization, DTSS) or products (differential product stabilization, DPS). It seems that Mg2, Glu126 and Cys198 play a major catalytic role, whereas Mg1 and the same Cys198 are responsible for product release. It is remarkable that no dominant role of an electrostatic term in the interactions involved in catalytic activity is observed for product release. Determination of catalytic fields expressing differential electrostatic potential of the transition state with respect to substrates revealed the optimal electrostatic features of an ideal catalyst for the studied reaction. The predicted catalytic environment is in agreement with experimental data showing increased catalytic activity of ThiK upon mutation of Cys198 to aspartate. Figure Catalytic fields for ThiK-catalyzed reaction juxtaposed with the positions of active site residues of a model system. Magnesium ions are considered part of the transition state/reactants. The surface of constant electronic density is colored according to differential electrostatic potential of transition state with respect to reactants. The sign of the differential potential reflects the electrostatic properties of a complementary molecular environment. Red (green) color denotes regions where a negative (positive) charge would be optimal for catalytic activity     

Sequence-selectivity of 5,11-dimethyl-5H-indolo[2,3-b]quinoline binding to DNA. Footprinting and molecular modeling studies

Indolo[2,3-b]quinolines are a new family of the DNA intercalators showing significant cytotoxic activity. The mechanism of their action is based on the inhibition of DNA topoisomerase II activity. It depends on their ability to induce and stabilize drug-topII-DNA cleavable complexes. Site-specific intercalation of 5,11-dimethyl-5H-indolo[2,3-b]quinoline (DiMIQ) was analyzed in vitro by DNaseI footprinting and by molecular modeling. To model the DNA-intercalator complex, use was made of the CVFF and ESFF force fields implemented in Insight 97.0 software. Experimental results were verified using a simple statistical model. The DiMIQ molecule was found to bind preferentially to the pBR322 DNA plasmid in the 5'-TGCTAACGC-3' region between adjacent adenine bases.     

中国环境管理分区:方法与方案

我国生态环境可持续性及其影响因素的区域差异显著,各地区环境管理面临的主要挑战和需要优先解决的生态环境问题不同。进行环境管理分区,根据各地区生态环境特征及其影响因素的差异性,制定有针对性的环境管理政策,将有效促进我国区域生态环境的整体优化。采取定性和定量分析相结合的方法进行我国环境管理分区。首先,在我国3大自然区的基础上,根据我国的自然地理格局和已有的相关区划成果,把我国划分为4个环境管理大区,包括:南部季风区、北部季风区、西北干旱区和青藏高寒区。其次,通过建立的包含13个指标的环境管理分区指标体系,采用一维化欧式距离法分析各环境管理大区下相邻省级行政区环境特征的相似性,把环境特征相似性大的相邻地区划分到同一分区,得到以省级行政区为基本单元的我国环境管理分区方案。然后,结合地区间历史渊源和区域未来发展趋势分析,对基于相似性分析的初步分区方案进行调整,把我国划分为8个以省级行政区为基本单元环境管理区。最后,根据相关调整原则和方法,对以省级行政区为基本单元的分区方案的边界线进行调整,得到以地级行政区为基本单元的分区方案,把我国划分为东北地区、华北平原区、华北山地与高原区、东南沿海地区、长江流域中游地区、西南地区、西北干旱区和青藏高寒区8个环境管理区。     

超高浓度培养基条件下酵母细胞生长及酒精生成的准稳态动力学研究

在1．5L搅拌式发酵罐中,使用葡萄糖质量浓度分别为120、200、280g／L的培养基进行酿酒酵母Saccharomyces cerevisiae连续发酵生成酒精的动力学研究。研究发现,当培养基中葡萄糖浓度为200和280g／L时,发酵液中残糖浓度、酒精浓度以及菌体生物量从小幅度波动的准稳态发展到大幅度波动的振荡状态。提出了伴有周期性振荡现象准稳态过程的概念,并针对该过程,建立了兼有底物和产物抑制的酵母细胞生长和产物酒精生成动力学模型。