Sinorhizobium meliloti ExoR is the target of periplasmic proteolysis

Sinorhizobium meliloti ExoR regulates the production of succinoglycan and flagella through the ExoS/ChvI two-component regulatory system. ExoR has been proposed to inhibit the ExoS sensor through direct interaction in the periplasm. To understand how ExoR suppression of ExoS is relieved, which is required for the expression of ExoS/ChvI-regulated symbiosis genes, we characterized wild-type ExoR and ExoR95 mutant proteins. In addition to the previously identified precursor and mature forms of ExoR (designated ExoR(p) and ExoR(m), respectively), we detected a 20-kDa form of ExoR (designated ExoR(c20)) derived from the wild-type ExoR protein, but not from the ExoR95 mutant protein. ExoR(c20) was isolated directly from S. meliloti periplasm to identify its N-terminal amino acids and the site of the proteolysis, which is highly conserved among ExoR homologs. ExoR(c20) retains the C terminus of the wild-type ExoR. When expressed directly, ExoR(c20) did not complement the exoR95 mutation, suggesting that ExoR(c20) does not function directly in the ExoR-ExoS/ChvI regulatory pathway and that ExoR(m) is the functional form of ExoR. A single-amino-acid change (ExoRL81A) at the site of ExoR periplasmic proteolysis resulted in the reduction of the amount of ExoR(m) and the loss of the regulatory function of the ExoR protein. These findings suggest that ExoR(m) is a target of periplasmic proteolysis and that the amount of ExoR(m) could be reduced through effective proteolysis to relieve its suppression of ExoS.     

Identification of histone deacetylase 3 as a biomarker for tumor recurrence following liver transplantation in HBV-associated hepatocellular carcinoma

Background

Recent studies have shown that high expression levels of class I histone deacetylases (HDACs) correlate with malignant phenotype and poor prognosis in some human tumors. However, the expression patterns and prognostic role of class I HDAC isoforms in hepatocellular carcinoma (HCC) remain unclear.

Methodology/Principal Findings

The expression patterns and clinical significance of class I HDAC isoforms were assessed by immunohistochemistry in a cohort of 43 hepatitis B virus-associated HCC patients treated with liver transplantation. In addition, the effects of HDAC inhibition on HCC cell behavior were investigated by knockdown of the HDAC isoform with short interfering RNA. Class I HDACs were highly expressed in a subset of HCCs with positivity for HDAC1 in 51.2%, HDAC2 in 48.8%, and HDAC3 in 32.6% of cases. The expression levels of HDAC isoforms were significantly associated with the proliferation index of HCC. Kaplan-Meier curves showed that a high expression level of HDAC2 or HDAC3 implicated significantly reduced recurrence-free survival. Cox proportional hazards model analysis revealed HDAC3 overexpression was an unfavorable independent prognostic factor (P = 0.002; HR 3.907). In vitro, inhibition of HDAC2 and HDAC3, but not HDAC1, suppressed proliferation and the invasiveness of liver cancer cells.

Conclusions/Significance

Our findings demonstrate that HDAC3 plays a significant role in regulating tumor cell proliferation and invasion, and it could be served as a candidate biomarker for predicting the recurrence of hepatitis B virus-associated HCC following liver transplantation and a potential therapeutic target.     

中国稻谷可培养真菌群落组成及多样性

真菌生长导致粮食品质下降及真菌毒素污染,是造成粮食损失的主要原因。我们采用形态学与分子系统发育分析相结合的方法,对中国13个省78份稻谷样品的真菌群落组成及多样性进行研究。结果表明,本次共分离622株真菌,经初步鉴定分属于17属73个物种。南北方因气候条件差异较大,稻谷真菌数量和物种组成都存在很大差异。南方稻谷表面真菌数量（10 ⁴cfu/g）明显高于北方（10 ³cfu/g）。北方收获期的优势种主要属于枝孢属Cladosporium,南方收获期的优势种为黄曲霉Aspergillus flavus、黑曲霉Aspergillus niger和阿姆斯特丹曲霉Aspergillus amstelodami等。进入储藏期后,由于中国仓储管理要求较高,储藏环境相对稳定（aw≤0.75）,耐旱真菌阿姆斯特丹曲霉和多育曲霉Aspergillus proliferans（占比40%以上）成为优势种,这类真菌可作为储藏期粮堆异常的早期预警指示菌。南方收获期感染的黄曲霉和黑曲霉进入储藏期后仍保持优势比例,导致储藏期间毒素污染风险必然增加,因此南方稻谷收储环节均应加强监管。本研究通过分析南北方收获和储藏环节稻谷真菌群落组成差异及产毒真菌的分布规律,以期为中国粮库在稻谷收储环节的真菌毒素防控提供依据。     

Steroidal saponins with antimicrobial activity from stems and leaves of Paris polyphylla var. yunnanensis

Rhizoma Paridis, the root of Paris polyphylla var. yunnanensis (Trilliaceae), is a Chinese traditional medicine, which resources become less and less. However, the aerial parts of this herb, which can regenerate every year, were discarded. In order to expand the resources, detailed chemical investigation on the stems and leaves of Paris polyphylla var. yunnanensis led to isolation of one sapogenin and 24 steroidal saponins (1-25), including 6 new glycosides, named chonglouosides SL-1-SL-6 (1-6). Their structures were elucidated on the basis of detailed analyses of their 1D and 2D NMR spectra and acid hydrolysis. Among them, compounds 3 and 4 are the first 23,27-dihydroxydiosgenin saponin having a sugar chain attached to C-23 or C-27, while compound 6 is the first 27-hydroxyruscogenin glycoside bearing 1, 27-di-O-sugar chains. The known compounds 10, 12, 14, 19, 20, 22, and 25 were isolated from the genus Paris for the first time. Antimicrobial testing activities of the selected compounds showed that compound 2, 3, 6, 8, 9, 11, 13, 17, 18, 21, and 24 were active against Propionibacterium acnes with MIC values of 62.5, 62.5, 3.9, 16.5, 17.2, 7.8, 39.0, 17.2, 31.3, 62.5, and 31.3μg/ml, respectively.     

Cytotoxicity of cardenolides and cardenolide glycosides from Asclepias curassavica

A new cardenolide, 12β,14β-dihydroxy-3β,19-epoxy-3α-methoxy-5α-card-20(22)-enolide (6), and a new doubly linked cardenolide glycoside, 12β-hydroxycalotropin (13), together with eleven known compounds, coroglaucigenin (1), 12β-hydroxycoroglaucigenin (2), calotropagenin (3), desglucouzarin (4), 6′-O-feruloyl-desglucouzarin (5), calotropin (7), uscharidin (8), asclepin (9), 16α-hydroxyasclepin (10), 16α-acetoxycalotropin (11), and 16α-acetoxyasclepin (12), were isolated from the aerial part of ornamental milkweed, Asclepias curassavica and chemically elucidated through spectral analyses. All the isolates were evaluated for their cytotoxic activity against HepG2 and Raji cell lines. The results showed that asclepin (9) had the strongest cytotoxic activity with an IC₅₀ value of 0.02 μM against the two cancer cell lines and the new compound 13 had significant cytotoxic activity with IC₅₀ values of 0.69 and 1.46 μM, respectively.     

气温和空气相对湿度对森林地表细小死可燃物平衡含水率和时滞的影响

以落叶松(Larix gmelinii)叶片、白桦(Betula platyphylla)叶片、落叶松-白桦叶片混合物为例, 初步研究了气温和空气相对湿度对地表细小死可燃物平衡含水率和时滞的影响, 对这3种可燃物在不同气温、不同空气相对湿度条件下(共20个温湿度组合)失水过程中的含水率进行了测定。通过统计软件建立了相应条件下3种类型可燃物含水率时间动态方程, 并利用此方程估算了3种可燃物平衡含水率和时滞, 同时用估算值分别建立了3种可燃物的平衡含水率-气温模型、平衡含水率-湿度模型、时滞-气温模型、时滞-湿度模型等4种模型。并用已知的4个可燃物平衡含水率模型拟合了该研究得到的平衡含水率数据, 其中, 用Van Wanger模型得到的平均绝对误差和均方根误差均不超过0.01, 拟合效果最好; Nelson模型的拟合效果最差。对气温和空气相对湿度对3种可燃物平衡含水率和时滞的影响的研究结果表明: 气温和空气相对湿度对3种可燃物的平衡含水率和时滞有显著影响, 气温与平衡含水率和时滞呈负相关关系, 而空气相对湿度与二者均呈正相关关系。其中, 时滞-湿度模型高估了可燃物的时滞。该研究具有一定的局限性与不确定性, 在未来的工作中, 应选择在更宽的可燃物类型范围内, 结合更全面的影响因子进行研究。     

茉莉花的化学成分

从药用植物茉莉花(Jasminum sambac(L．)Ait．)花蕾中分离到9个化合物,通过波谱分析并与已知化合物数据对照,分别鉴定为：苄基-O-β-D-葡萄吡喃糖甙(1),苄基-O-β-D-木吡喃糖基(1→6)-β-D-葡萄吡喃糖甙(2),tetraol(3),molihuaoside D(4),sarnhcoside A(5),sambacoside E(6),芦丁(rutin)(7),山奈酚-3-O-α-L鼠李吡喃糖基(1-2)[α-L鼠李吡喃糖基(1-6)]-β-D半乳吡喃糖甙(8),斛皮素-3-O-α-L鼠李吡喃糖基(1→2)[α-L鼠李吡喃糖基(1→6)]-β-D-半乳吡喃糖甙(9)。     

低自旋氰配位紫色震颤菌血红蛋白血红素及其周围质子的核磁共振研究

报道了低自旋氰配位紫色震颤菌血红蛋白 (VtHb CN)血红素及其周围质子的核磁共振谱 .通过MCOSY ,NOESY ,1DNOE和TOE ,以及SUPERWEFT实验对VtHb -CN的¹H核磁共振谱进行识别 .已识别了血红素和配位组氨酸的几乎所有共振峰 ,获得了这些共振峰的自旋 晶格弛豫时间和它们的化学位移随温度的变化关系 ,由此可分别获得这些质子到血红素Fe³⁺ 的距离和抗磁化学位移 .通过化学位移的pH滴定 ,得到了配位组氨酸 (His 85 )的咪唑环的电离平衡常数pK_a( =4.95 ) .这一较低的pK_a 值 ,归因于带正电的Fe³⁺ 以及His 85与血红素Fe³⁺   的配位 .     

Phytochemicals from the Leaves of Cyclocarya paliurus and their 11β-HSD1 Enzyme Inhibitory Effects

Two new dammarane-type triterpenoid saponins, 3β-(α-l -arabinopyranosyloxy)-24,25-dihydroxydammar-20-en-12α-yl 6-deoxy-β-d -glucopyranoside ( 1 ) and (24R)-3β-[(4-O-acetyl-α-l -arabinopyranosyl)oxy]-25-hydroxy-20,24-epoxydammaran-12β-yl 6-deoxy-β-d -glucopyranoside ( 2 ), and fourteen known triterpenoids were isolated from the 70 % MeOH extract of the leaves of Cyclocarya paliurus. Their structures were established based on analyses of spectroscopic data. All compounds were tested for their inhibitory activities against the 11β-HSD1 enzyme. Hederagenin ( 13 ) exhibited moderate inhibitory effect for mouse 11β-HSD1 with an IC₅₀ value of 0.16±0.04 μM.