蔗糖磷酸化酶全细胞催化AA-2G的条件优化

目的:使用表达蔗糖磷酸化酶(EC 2.4.1.7,Sucrose phosphorylase,SPase)的大肠杆菌重组工程菌E.coli BL21/pET-spase,作为全细胞催化剂,合成2-O-D-吡喃葡糖基-L-抗坏血酸(Ascorbic acid 2-glucoside,AA-2G)。通过反应条件的优化研究,提高AA-2G的收率。方法:分别考察菌体量、缓冲液pH、蔗糖浓度、维生素C浓度、反应时间和温度对AA-2G合成反应的影响,再组合上述最佳条件进行反应。AA-2G的产量使用高效液相色谱法进行定量。结果:最佳反应条件为:菌体量15 mg/mL,缓冲液pH 4.5,蔗糖浓度100 g/L,维生素C浓度175 g/L,反应时间20 h,温度37℃。在此条件下,AA-2G产量达到了35.7 g/L。结论:以蔗糖为底物,使用SPase合成AA-2G的研究报道较少。本研究通过优化此方法的反应条件,让AA-2G的产量得到了大幅提高。同时本研究中成功地采用了大肠杆菌工程菌作为全细胞催化剂,这比传统的使用粗酶液的方法更省时省力,有良好的应用潜力。     

正交试验法确定测定意大利蜜蜂头部乙酰胆碱酯酶反应的最佳条件

用正交试验法研究了酶浓度、底物浓度、反应体系的pH值、反应温度和反应时间5个因素对测定意大利蜜蜂Apis mellifera ligustica Spinola头部乙酰胆碱酯酶(AChE)活性的影响, 并从试验组合中选出最佳条件。蜜蜂AChE活性的测定采用Gorun(1978)改进的Ellman方法, 以碘化硫代乙酰胆碱(ATCI)为底物, 5, 5' 二硫双硝基苯甲酸(DTNB)为显色剂, 测定反应物在412 nm波长下的光密度值, 用考马斯亮蓝G-250法测定蛋白质含量, 经计算得到蜜蜂头部AChE的比活力。对正交试验结果进行极差分析和方差分析, 结果表明各因素对实验结果影响的大小顺序为：温度＞pH值＞时间＞酶浓度＞底物浓度。并得出测定蜜蜂头部AChE活性的最佳条件是：酶终浓度0.2头/mL、底物终浓度0.8 mmol/L、pH值7.5、温度40℃及反应时间5 min。     

固定化β-葡萄糖苷酶催化合成红景天甙的研究

目的:利用海藻酸钠和壳聚糖固定β-葡萄糖苷酶,催化合成红景天甙,并对固定化条件的选择、固定化酶催化合成红景天甙的条件优化进行研究.方法:采用正交实验方法寻求最佳固定化条件,以转化率为指标对合成条件进行优化.结果:固定β-葡萄糖苷酶的最佳条件为:壳聚糖浓度1.5%,吸附时间9h,交联时间12h,戊二醛浓度1.0%,吸附温度O℃,酶活力回收率达74.38%.催化合成红景天甙的最佳条件为:反应介质pH 5.8醋酸缓冲液/叔丁醇(1:9),底物浓度酩醇5g/L,D-葡萄糖与酪醇摩尔比为1:1,反应时间50h,反应温度50℃,红景天甙的转化率最高可达到71.9%.结论:固定化酶催化合成红景天甙的转化率得到较大的提高,为工业化生产提供了可靠的理论依据.     

一株脂肪酶产生菌的筛选及产酶条件优化研究

通过利用溴甲酚紫显色培养基初筛和酶活测定法复筛得到产脂肪酶的一株细菌HP2,经形态学观察和生理生化测定初步鉴定该菌株为不动杆菌属。并对该菌株的摇床培养产酶条件进行了初步研究,采用正交试验对HP2菌株发酵产脂肪酶的条件进行了优化,得到最佳发酵条件为初始pH为7.7,培养温度为35℃,接种量(V/V)为1.5%,发酵周期为48 h,酶活力达到129.7 U/mL。     

嗜麦芽黄单胞菌游离细胞催化合成α-熊果苷

研究了利用嗜麦芽黄单胞菌BT-112(Xanthomonas maltophilia BT-112)游离细胞生物催化合成α-熊果苷,系统探讨了温度、对苯二酚浓度、对苯二酚与蔗糖摩尔比、反应时间、转速、细胞浓度、磷酸缓冲溶液pH值和浓度对反应转化率的影响。最佳反应条件为:反应温度为25℃,菌体对对苯二酚的最大耐受度为30mmol/L,蔗糖和对苯二酚的摩尔比为20∶1,反应时间为45h,摇床转速为160r/min,细胞浓度为85g/L,磷酸缓冲溶液浓度为25mmol/L、pH值为8.0。在此条件下α-熊果苷转化率高达86.7%(以对苯二酚计算)。     

Fe^2＋-H2O2体系降解壳聚糖

Fe2 -H2O2体系能够有效地降解壳聚糖,反应介质的pH值、反应时间、反应温度、Fe2 浓度及H2O2浓度等实验因素对壳聚糖的降解效果都有程度不同的影响,其中以反应介质的pH值和H2O2浓度对降解反应的影响为最大.在pH值为3～5时Fe2 -H2O2体系降解壳聚糖的活性最高.适当增大H2O2的用量可以增大壳聚糖的降解程度,但当其用量增大至一定程度后,壳聚糖降解产物分子量的下降趋势明显变缓.合理的Fe2 -H2O2体系降解壳聚糖的实验条件为:介质pH值3～5;温度,室温;时间60～90 min;壳聚糖:H2O2:Fe2 =240:12～24:1～2(摩尔比).     

α-淀粉酶水解魔芋飞粉最佳条件优化的研究

本研究采用单因素和正交试验的方法对α-淀粉酶水解魔芋飞粉的酶用量、pH值、温度、[Ca2 ]和底物浓度等条件进行优化,结果表明当α-淀粉酶用量为4u/g淀粉、pH为6.0、温度为60℃、[Ca2 ]为0.01mol/L和底物浓度为8%时,水解度达20%,为最佳反应条件,研究为进一步利用α-淀粉酶水解魔芋飞粉生产燃料乙醇奠定了基础.     

聚乙二醇诱导鸡红细胞融合条件的优化

目的:探讨聚乙二醇诱导鸡红细胞融合最适条件.方法:以鸡红细胞为材料,聚乙二醇为诱导剂,从细胞密度、融合温度、聚乙二醇浓度及反应时间进行单因素实验,并设计3因素3水平的正交实验计算细胞融合率.结果:鸡红细胞融合的最佳条件是:细胞密度为2×106个/ml,聚乙二醇浓度为35%,反应温度为35℃,反应时间40min.结论:在该条件下,细胞融合率最高达33.06%.     

菖蒲过氧化物酶测定条件的研究

过氧化物酶是植物在低温等逆境条件下酶促防御系统的关键酶之一,其活性可以作为植物抗寒性的一个指标。以菖蒲为材料比较了反应体系、H2O2浓度、pH值及反应时间对过氧化物酶活性测定的影响。结果表明:过氧化物活性测定的较佳反应体系是3 mL;最佳H2O2浓度为0.1%;最佳磷酸缓冲液pH值为6.0;最佳反应时间为4min。该研究结果为人工湿地污水处理系统冬季植物的筛选与评价研究提供参考,对植物生理实验教学和相关科学研究有一定的参考价值。     

脂肪酶催化猪油与辛酸酸解制备功能性脂反应条件的优化

目的:探索有机溶剂体系中酶法酸解猪油与辛酸制备减热量型功能性脂的最佳反应条件。方法:采用响应曲面法中的3水平5因子2星点部分因子试验设计,评价酸解反应中的5个关键因素,即酶量、反应时间、反应温度、底物比率和水分添加量及其交互作用对辛酸插入率的影响,确定最佳反应条件。结果:建立了辛酸插入率对5个变量的一个2次多项式数学模型,该模型极显著(P<0.0001),拟合优度良好。通过主效应分析,得出每个因子对模型的贡献程度从大到小依次为反应温度(负效应)>底物比率>反应时间>酶量(在实验范围内,水分不影响辛酸插入率)。借助模型方程产生的等高线图及统计软件,分析得出最大辛酸插入率下各个因子的最适水平分别为酶量16%,反应时间36h,反应温度50℃,底物比率3.8,水分添加量5%。在此条件下辛酸插入率达到了50.5mol%,与模型预测值50.7mol%非常吻合。结论:应用响应曲面法对有机溶剂体系中酶法酸解猪油与辛酸制备减热量性脂的反应条件进行优化是合理可靠,科学迅速的,且有效的。     

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.