Three‐Stage Inter‐Orthorhombic Evolution and High Thermoelectric Performance in Ag‐Doped Nanolaminar SnSe Polycrystals

The ultrahigh thermoelectric performance of SnSe‐based single crystals has attracted considerable interest in their polycrystalline counterparts. However, the temperature‐dependent structural transition in SnSe‐based thermoelectric materials and its relationship with their thermoelectric performance are not fully investigated and understood. In this work, nanolaminar SnSe polycrystals are prepared and characterized in situ using neutron and synchrotron powder diffraction measurements at various temperatures. Rietveld refinement results indicate that there is a complete inter‐orthorhombic evolution from Pnma to Cmcm by a series of layer slips and stretches along the a‐ and b‐axes over a 200 K temperature range. This phase transition leads to drastic enhancement of the carrier concentration and phonon scattering above 600 K. Moreover, the unique nanolaminar structure effectively enhances the carrier mobility of SnSe. Their grain and layer boundaries further improve the phonon scattering. These favorable factors result in a high ZT of 1.0 at 773 K for pristine SnSe polycrystals. The thermoelectric performances of polycrystalline SnSe are further improved by p‐type and n‐type dopants (i.e., doped with Ag and SnCl₂, respectively), and new records of ZT are achieved in Ag_0.015Sn_0.985Se (ZT of 1.3 at 773 K) and SnSe_0.985Cl_0.015 (ZT of 1.1 at 773 K) polycrystals.     

The UBC Domain Is Required for BRUCE to Promote BRIT1/MCPH1 Function in DSB Signaling and Repair Post Formation of BRUCE-USP8-BRIT1 Complex

BRUCE is implicated in the regulation of DNA double-strand break response to preserve genome stability. It acts as a scaffold to tether USP8 and BRIT1, together they form a nuclear BRUCE-USP8-BRIT1 complex, where BRUCE holds K63-ubiquitinated BRIT1 from access to DSB in unstressed cells. Following DSB induction, BRUCE promotes USP8 mediated deubiquitination of BRIT1, a prerequisite for BRIT1 to be released from the complex and recruited to DSB by binding to γ-H2AX. BRUCE contains UBC and BIR domains, but neither is required for the scaffolding function of BRUCE mentioned above. Therefore, it remains to be determined whether they are required for BRUCE in DSB response. Here we show that the UBC domain, not the BIR domain, is required for BRUCE to promote DNA repair at a step post the formation of BRUCE-USP8-BRIT1 complex. Mutation or deletion of the BRUCE UBC domain did not disrupt the BRUCE-USP8-BRIT1 complex, but impaired deubiquitination and consequent recruitment of BRIT1 to DSB. This leads to impaired chromatin relaxation, decreased accumulation of MDC1, NBS1, pATM and RAD51 at DSB, and compromised homologous recombination repair of DNA DSB. These results demonstrate that in addition to the scaffolding function in complex formation, BRUCE has an E3 ligase function to promote BRIT1 deubiquitination by USP8 leading to accumulation of BRIT1 at DNA double-strand break. These data support a crucial role for BRUCE UBC activity in the early stage of DSB response.     

The effect of interleukin-2 on experimental emotional hypertension]

The effect of human recombinant interleukin-2, one of the potent mediators of the immune system, on the course of emotional hypertension in non-linear white rats has been investigated. A significant and prolonged hypotensive action of a single injection of interleukin-2 in hypertensive rats has been revealed. The data obtained can be a new evidence of participation of immune system in the development of hypertension in experimental animals.     

An eight-nucleotide sequence in the potato virus X 3' untranslated region is required for both host protein binding and viral multiplication.

Gel retardation and UV-cross-linking techniques were used to demonstrate that two tobacco proteins, with approximate molecular masses of 28 and 32 kDa, bind to a site within the 3' region of potato virus X (PVX) genomic RNA. The protein binding is specific, in that a 50-fold excess of unlabeled probe prevents formation of the complexes but no reduction is observed with a 2,000-fold molar excess of yeast tRNA. Complex formation is inhibited by poly(U) but is relatively unaffected by poly(A), poly(G), or poly(C-I). PVX RNA-host protein complex formation occurs in vitro at salt concentrations up to 400 mM. Deletion mapping indicates that the proteins bind within the 3' untranslated region (UTR) of PVX genomic RNA and that an 8-nucleotide U-rich sequence (5'-UAUUUUCU) is required for the binding. Deletion of the 8-nucleotide U-rich region from the 3' UTR of a sensitive PVX reporter virus that carries the luciferase gene in place of the PVX coat protein gene results in a more than 70,000-fold reduction in luciferase expression in tobacco protoplasts. RNA probes carrying the sequence GCGC in place of the central four contiguous uridines of the 8-nucleotide U-rich motif fail to bind host protein at detectable levels, and the same mutation, when introduced into the PVX reporter virus, eliminates viral multiplication. Mutations of 1 or 2 nucleotides within the same four uridines reduced both binding of host proteins and replication of reporter virus. These results indicate that the 8-nucleotide U-rich motif within the PVX 3' UTR is important for some aspect of viral multiplication and suggest that host protein binding plays a role in the process.     

城市景观生态风险评估框架与实践——以北京天坛地区为例

当前，城市景观生态风险研究缺少科学合理、方便实用的评估框架。作者基于景观生态风险评估基本范式，明确了城市景观生态服务价值的测算方法，分析了引起生态损害的自然因素和人类活动因素，形成了城市景观生态风险评估的技术框架和参数体系；继而以北京天坛地区为研究区，开展了典型城市景观生态风险的定量评估。结果表明：（1）天坛地区景观生态价值总量约为2.41亿元。区域的历史文化价值最高，教育和美学景观价值紧随其后。（2）城市景观生态受损概率呈现"北高南低"的空间分布格局。生态受损概率的高值区面积占整个区域总面积的22.2%，主要分布在珠市口、磁器口和崇文门附近区域。（3）城市景观生态风险呈现"北低南高"的空间分布格局。高风险区主要分布在天坛公园内的文物建筑周边。本研究提供了一个可参考的城市景观生态风险评估应用框架，对生态风险评估中的不确定性进行了讨论，研究针对天坛案例区的具体结论有助于城市管理者避免潜在的风险。     

gacS基因插入失活对绿针假单胞菌G-05的两种胞外次生代谢物合成的影响

一株来自大棚温室甜椒根际的绿针假单胞菌Pseudomonas chlororaphis G-05，可分泌抗生物质吩嗪-1-羧酸，并具有抑制辣椒疫霉的生物防治功效。【目的】为了系统研究该菌株的生物防治功能及抗生物质合成与分泌机制。【方法】首先通过生化法和16S rDNA同源比对法对该菌株进行系统分类的初步鉴定，再根据基因的同源性从G-05基因组DNA中克隆长1.4 kb的gacS基因的部分保守区段，采用抗庆大霉素基因（gentamycin resistance cassette, aacC1）插入失活的策略构建了该基因突变株G-05S。【结果】在King’ s B（KMB）或PPM培养基中，突变株G-05S合成吩嗪-1-羧酸的能力受到明显抑制。然而，突变株G-05S分泌的吲哚乙酸与野生株相比无显著差异。互补实验表明，gacS基因的表达可以使突变株G-05S的吩嗪-1-羧酸的合成恢复到野生株水平。【结论】由此推测，GacS(Global activator sensor )对不同次生代谢物的调控具有特异性。