Understanding the Effects of Molecular Dopant on n‐Type Organic Thermoelectric Properties

Molecular doping is a powerful method to fine‐tune the thermoelectric properties of organic semiconductors, in particular to impart the requisite electrical conductivity. The incorporation of molecular dopants can, however, perturb the microstructure of semicrystalline organic semiconductors, which complicates the development of a detailed understanding of structure–property relationships. To better understand how the doping pathway and the resulting dopant counterion influence the thermoelectric performance and transport properties, a new dimer dopant, (N‐DMBI)₂, is developed. Subsequently, FBDPPV is then n‐doped with dimer dopants (N‐DMBI)₂, (RuCp*mes)₂, and the hydride‐donor dopant N‐DMBI‐H. By comparing the UV–vis–NIR absorption spectra and morphological characteristics of the doped polymers, it is found that not only the doping mechanism, but also the shape of the counterion strongly influence the thermoelectric properties and transport characteristics. (N‐DMBI)₂, which is a direct electron‐donating dopant with a comparatively small, relatively planar counterion, gives the best power factor among the three systems studied here. Additionally, temperature‐dependent conductivity and Seebeck coefficient measurements differ between the three dopants with (N‐DMBI)₂ yielding the best thermoelectric properties. The results of this study of dopant effects on thermoelectric properties provide insight into guidelines for future organic thermoelectrics.     

320例腹泻患者病原菌分离及流行病学分析

目的了解广州市2009年至2010年肠道门诊就诊的细菌性腹泻患者病原谱的分布情况,为制定针对重点人群肠道传染病防治策略提供依据。方法收集2009年5月至2010年5月暨南大学附属第一医院腹泻患者的粪便标本,使用卡-布运送培养基,增菌培养后,采用生化反应和氧化酶试验进行菌株鉴定,并用梅里埃API生化板条进行验证,用病原菌诊断血清进行细菌分型。结果从320份粪便标本中分离到38株菌株,其中沙门菌15株,产毒大肠埃希菌12株,致病大肠埃希菌6株,志贺菌2株,出血性大肠埃希菌、霍乱弧菌、气单胞菌各1株。0—20岁年龄段高发,以1岁以内婴幼儿为主;7—10月为发病高峰期。结论来该院肠道门诊就诊的细菌性腹泻患者,其病原体以沙门菌为主,其次为产毒大肠埃希菌。因此．广州地区细菌件腹泻的预防．廊右针对件的面向雷占人群和重占病厢莴．     

无细胞蛋白质合成系统的研究进展

无细胞蛋白质合成系统是一种以外源mRNA或DNA为模板 ,通过在细胞抽提物的酶系中补充底物和能源物质来合成蛋白质的体外系统 .与传统的体内重组表达系统相比 ,体外无细胞合成系统具有多种优点 ,如可表达对细胞有毒害作用或含有非天然氨基酸 (如D 氨基酸 )的特殊蛋白质 ,能够直接以PCR产物作为模板同时平行合成多种蛋白质 ,开展高通量药物筛选和蛋白质组学的研究等 .本文综述了无细胞蛋白质合成系统的发展历史、系统中合成蛋白质所需的能量供应、遗传模板的稳定性和微型无细胞生物反应器等多方面的研究 ,并探讨了无细胞蛋白质合成系统中存在的难点、研究方向和广泛的应用前景     

Structural Basis of Lipid Binding for the Membrane-embedded Tetraacyldisaccharide-1-phosphate 4′-Kinase LpxK

The membrane-bound tetraacyldisaccharide-1-phosphate 4′-kinase, LpxK, catalyzes the sixth step of the lipid A (Raetz) biosynthetic pathway and is a viable antibiotic target against emerging Gram-negative pathogens. We report the crystal structure of lipid IV_A, the LpxK product, bound to the enzyme, providing a rare glimpse into interfacial catalysis and the surface scanning strategy by which many poorly understood lipid modification enzymes operate. Unlike the few previously structurally characterized proteins that bind lipid A or its precursors, LpxK binds almost exclusively to the glucosamine/phosphate moieties of the lipid molecule. Steady-state kinetic analysis of multiple point mutants of the lipid-binding pocket pinpoints critical residues involved in substrate binding, and characterization of N-terminal helix truncation mutants uncovers the role of this substructure as a hydrophobic membrane anchor. These studies make critical contributions to the limited knowledge surrounding membrane-bound enzymes that act upon lipid substrates and provide a structural template for designing small molecule inhibitors targeting this essential kinase.     

Genotypic alteration and competitive nodulation of Mesorhizobium muleiense against exotic chickpea rhizobia in alkaline soils

Mesorhizobium muleiense, Mesorhizobium mediterraneum and Mesorhizobium ciceri are chickpea (Cicer arietinum L.) rhizobia that share a high similarity of the symbiotic genes nodC and nifH, but they have different geographic distributions. M. muleiense has been isolated and found only in alkaline soils of Xinjiang, China, whereas the other two strains have been found in the Mediterranean and India. To investigate the species stability of M. muleiense during natural evolution and its capability of competitive nodulation against the other two exotic species, re-sampling of nodules in the field and competition experiments between the three species were conducted. The results showed that the predominant microsymbiont associated with chickpea grown in Xinjiang was still M. muleiense, but the predominant genotypes of M. muleiense had changed significantly during the four years since a previous survey. The data also showed that M. mediterraneum and M. ciceri were more competitive than the residential strain of M. muleiense CCBAU 83963^T in sterilized vermiculite or soils from Xinjiang. However, in non-sterilized soils, M. muleiense was the predominant nodule occupier. These results indicated that natural or adapting evolution of M. muleiense was occurring in fields subjected to changing environmental factors. In addition, the biogeography and symbiotic associations of rhizobia with their host legumes were also influenced by biological factors in the soil, such as indigenous rhizobia and other organisms.     

The ecological potential of a restored abandoned quarry ecosystem in Mt. Mufu, Nanjing, China

In order to conserve the remaining rare dolomite rocks and restore Mt. Mufu, a forest restoration program has been implemented over ten years. Emergy analysis was used to evaluate the current status of the restored ecosystem, in addition, the ecological potential of the fully developed system was predicted and analyzed. Four main emergy indices of the two systems, EYR, EIR, ELR, and ESI, were calculated and compared. In addition, a relatively new emergy index, PYR, was used to evaluate the restored forest system's ecological potential. The results revealed that the current restored forest system was still in the initial stage of ecological restoration but it has already resulted in several positive effects, such as richness of plant biodiversity and improving air condition. The value of the predicted system's PYR is as great as 201.53, demonstrating that the restored forest system has a great potential for ecological development in the future.