S-腺苷甲硫氨酸合成酶对埃博霉素生物合成的影响

【目的】研究S-腺苷甲硫氨酸合成酶(SAMs)对埃博霉素生物合成的影响。【方法】通过向发酵培养基中添加抑制剂和促进剂,比较分析纤维堆囊菌中SAMs的活性变化以及埃博霉素的产量变化。【结果】在埃博霉素的合成期,SAMs的活性较高。加入抑制剂吲哚乙酸(IAA)之后,SAMs的活性和埃博霉素的产量都不同程度的降低,而加入促进剂对甲苯磺酸钠(p-TSA-Na)之后,SAMs的活性和埃博霉素的产量在不同程度上都有提高。在纤维堆囊菌的次级代谢中,SAMs活性与埃博霉素的生物合成量呈正相关。【结论】S-腺苷甲硫氨酸合成酶在纤维堆囊菌的埃博霉素生物合成过程中发挥了重要的作用。     

埃博霉素B小试发酵罐发酵条件研究

研究了纤维堆囊菌(Sorangium cellulosum)So F5-76在5 L发酵罐水平上发酵生产埃博霉素B的基本工艺参数,具体考察了接种量、搅拌转速、通气量、添加消泡剂及补糖等5个工艺参数对埃博霉素B发酵产量的影响。最后确定发酵罐基本发酵条件为接种量9%,搅拌转速180 r/min,空气流量3.5 L/min,消泡剂种类选择Antifoam B聚醚类消泡剂,补糖控制在发酵液糖浓度为0.2 g/L,在此条件下埃博霉素B的产量可达25.6 mg/L。     

纤维堆囊菌SoF5-76产埃博霉素B分批发酵动力学研究

埃博霉素发酵生产体系复杂,且生产菌株较难操作,导致发酵参数测定困难,迄今为止未见关于埃博霉素发酵动力学方面的报道。利用5 L发酵罐,对纤维堆囊菌(Sorangium cellulosum)产埃博霉素B(Epothilone B)的分批发酵动力学进行了研究,整个发酵过程中维持温度30℃、p H7.4。发酵结束时,菌体干重达3.00 g/L,埃博霉素B产量达18.20 mg/L,葡萄糖含量为0.049g/L。基于Logistic方程和Luedking-Piret方程,利用MATLAB软件对其进行非线性拟合,构建了菌体生长、埃博霉素B合成和葡萄糖消耗的动力学模型。结果表明,该组模型能较好的拟合发酵过程。     

响应面法优化纤维堆囊菌SoF5-76产埃博霉素B发酵培养基

以纤维堆囊菌SOF5-76为试验菌株,用响应面分析法对其产埃博霉素B的培养基进行优化,以提高埃博霉素B的产量。在单因素试验的基础上,利用Plackett-Burman筛选出对埃博霉素B产量有显著影响的3个因素为马铃薯淀粉、脱脂奶粉和无水氯化钙,在此基础上通过最陡爬坡试验逼近最佳响应面区域;再运用Box-Behnken试验设计和响应面分析法进行回归分析,确定重要因素的最优浓度。得到最佳发酵培养基为:马铃薯淀粉3.9 g/L、脱脂奶粉2.2 g/L、无水氯化钙1.3 g/L、葡萄糖1 g/L,豆饼粉1.5g/L,七水硫酸镁2.5 g/L,EDTA-Fe3+3 mL/L,微量元素(TE)0.5 mL/L,VB121 mL/L。在此最优条件下发酵埃博霉素B的产量为29.95 mg/L,与模型预测值接近,发酵产量比优化前提高了1.1倍。     

培养基组成对纤维堆壤菌产埃博霉素的影响

埃博霉素(Epothilone)是粘细菌纤维堆壤菌(Sorangium cellulosum)产生的具有抗肿瘤活性的次级代谢产物。为了提高埃博霉素A和B的产量,以及B/A的比率,以G52培养基为基础培养基,研究了黄豆粉、酵母粉、酪蛋白胨和丙酸钠对纤维堆壤菌产埃博霉素的影响。结果表明:低脂黄豆粉和酪蛋白胨作为氮源,同时加入6.25 mmol/L丙酸钠作为前体物质,埃博霉素A和B的产量分别比原始条件平均提高1.47倍和2.88倍,B/A的比率比原始条件平均提高了1.97倍。     

埃博霉素（Epothilones）的PKS/NRPS杂合基因簇

埃博霉素是由粘细菌纤维堆囊菌产生的一类具有促微管聚合活性的大环内酯类化合物。埃博霉素生物合成的多酶复合体是一个由多个功能模块组成,同时含有多聚酮合酶（PKS）和非核糖体肽合成酶（NRPS）的大操纵子。根据同位素标记试验结果和合成酶全基因簇功能的推测,埃博霉素的生物合成包括聚酮链的引发、链合成的起始和噻唑环的形成、链的延伸和转移、链合成的终止释放和环化、及产物的后修饰5个阶段。埃博霉素的PKS/NRPS杂合基因簇是开展组合生物合成研究的良好材料。     

利用异源正调控基因acyB2构建埃莎霉素Ⅰ高产菌株

必特螺旋霉素(bitespiramycin,BT)是以异戊酰螺旋霉素(简称为埃莎霉素)Ⅰ、Ⅱ和Ⅲ为主要成分的多组分抗生素。通过阻断3-O-酰基转移酶基因(sspA),获得了只产埃莎霉素Ⅰ的WSJ-2菌株,但其发酵产物中含有大量螺旋霉素,而埃莎霉素Ⅰ含量较低。为提高4″-异戊酰基转移酶基因(ist)在WSJ-2中的表达水平,从而提高埃莎霉素Ⅰ的产量,首先构建了含有ist基因和其正调控基因acyB2连锁片段的重组质粒pSET152-ia,然后将其导入到埃莎霉素Ⅰ产生菌WSJ-2中,通过具有阿普拉霉素(apramycin)抗性标记的链霉菌整合型载体pSET152整合到WSJ-2的染色体上,获得新的埃莎霉素Ⅰ产生菌WSJ-IA。在不同发酵时间定量检测ist的表达水平,WSJ-IA中ist的表达量要明显高于WSJ-2。WSJ-IA高产菌株的发酵单位从(280±20)μg/ml提高至(1160±108)μg/ml,较原始菌株WSJ-2提高了314%,而且在WSJ-IA发酵产物中埃莎霉素Ⅰ与螺旋霉素Ⅰ含量的比值是WSJ-2的2.4倍左右,说明在引入acyB2基因的同时提高了菌株的发酵单位和埃莎霉素Ⅰ的产量。     

青纶纤维接枝改性后抗菌作用的实验观察

目的观察经接枝改性后FFA-3和FFS-1纤维织物的抗菌作用.方法采用容器振荡法,溶液为生理盐水,纤维含量为2.5%,受试菌接种量为105～106CFU/ml,作用12h.结果 2种纤维中的大肠埃希菌存活菌数均为0;葡萄球菌存活菌数分别是1.02×104和4.16×103CFU/ml.而对照纤维中2种受试菌存活菌数分别为1.6×105CFU/ml和2.99×104CFU/ml.结论 FFA-3和FFS-1纤维织物有一定的抗菌作用.     

綪纶纤维接枝改性后抗菌作用的实验观察

目的　观察经接枝改性后 FFA- 3和 FFS- 1纤维织物的抗菌作用。方法　采用容器振荡法 ,溶液为生理盐水 ,纤维含量为 2 .5 % ,受试菌接种量为 10 5～ 10 6 CFU/ml,作用 12 h。结果　 2种纤维中的大肠埃希菌存活菌数均为 0 ;葡萄球菌存活菌数分别是 1.0 2× 10 4和 4.16× 10 3CFU/m l。而对照纤维中 2种受试菌存活菌数分别为 1.6× 10 5 CFU/ml和 2 .99× 10 4CFU/m l。结论　 FFA- 3和 FFS- 1纤维织物有一定的抗菌作用     

制备液相色谱分离纯化埃博霉素B

基于制备液相色谱法开发与优化埃博霉素B的分离纯化工艺，制备得高纯度埃博霉素B样品。实验首先对埃博霉素B粗品进行了液相色谱（HPLC）分析，定位目标峰和杂质情况。其次，对两款正相色谱填料进行筛选和模拟制备，考查不同填料对埃博霉素B相关杂质的去除效果和回收率。结果表明，上样量为0.2%时，埃博霉素B在NPLC-2分析柱（250 mm×4.6 mm, 10μm）上保留得较好，可与杂质有效分离。最后，将优化好的纯化方法在制备水平上进行放大，以正庚烷和乙酸丁酯为洗脱剂，使用NPLC-2制备柱（260 mm×50 mm, 10μm）对埃博霉素B粗品进行分离纯化，样品的色谱纯度可达99.63%，回收率为90%，各项有关杂质均符合限量规定。该方法对埃博霉素B的相关杂质去除效果好，纯化效率和回收率均很高，为埃博霉素B分离纯化生产工艺的开发提供了新方法。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.