变性剂作用下文昌鱼碱性磷酸酶构象与催化活力变化

研究了文昌鱼碱性磷酸酶(AKP)的变性作用,结果表明:低浓度盐酸胍(0.5 mol/l,1.0 mol/l)对该酶具有明显激活作用;酶的荧光构象变化指标随脲浓度增大呈现两个陡变区(1.0～2.0 mol/l,4.0～8.0 mol/l),蜂位因变性剂存在而明显红移,表明肽链己发生较明显的伸展,该酶的失活与变性过程均为一级反应,低浓度脲(2.0 mol/l)作用表现为构象变化略快于失活,而高浓度盐酸胍(2.0 mol/l,4.0 mol/l)及高浓度脲(4.0 mol/l,6.0 mol/l,8.0 mol/l)作用均表现为失活略快于构象变化。     

效应物对牛肠激酶活性的影响

肠激酶(EK,EC 3. 4. 21. 9)是一种在基因工程产品中广泛应用的工具酶.以小分子荧光物质甘氨酰-天冬氨酰-天冬氨酰-天冬氨酰-天冬氨酰-赖氨酰-β-萘胺(Gly-Asp-Asp-Asp-Asp-Lys-β-naphthylamide, GD4K-β-naphthylamide) 为底物,采用荧光跟踪法研究了不同氨基酸、几种常用有机溶剂、EDTA、DTT等对牛肠激酶(BEK)活力的影响.结果表明:L-赖氨酸(L-Lys)、丙酮、EDTA、DTT对该酶的活性有较强的抑制作用,IC50分别约为25,50,50 和120 mmol/L.进一步研究了L-Lys与丙酮对BEK活力的抑制机理以及抑制类型,结果表明:L-Lys对该酶的抑制机理为可逆抑制,其抑制类型为竞争型抑制类型,其抑制常数KI为12.02 mmol/L.丙酮对BEK的抑制类型表现为不可逆抑制.     

发酵产物对灰绿曲霉β-葡萄糖苷酶活力的影响

从自行筛选出的灰绿曲霉XC-9菌株的发酵液得到活力较高的纤维素酶,分离纯化出其中的β-葡萄糖苷酶(BG).探讨发酵产物对酶活力的影响,乙醇、乙酸、乳酸对酶活力有不同程度抑制,抑制强度依次为乳酸乙酸乙醇,其半抑制浓度(IC50)分别为0.09,0.34和4.4mol/L.它们对BG的抑制作用均表现为非竞争性可逆抑制,抑制常数分别为0.7%(0.083mol/L)、2%(0.315mol/L)、26%(4.25mol/L),实验结果表明它们不是结合在酶活性中心的底物结合部位上,而是结合在其以外的必需基团上抑制酶活力.随着乙醇浓度上升,BG最适反应温度逐渐降低,乙醇达到20%(体积分数,下同)时,BG最适温度由60℃降到50℃.在低体积分数乙醇溶液(小于16%)中的BG活力高过无乙醇溶液中的BG活力.荧光光谱分析表明,高浓度乙醇可使BG分子构象松散,导致变构失效.该研究为纤维素酶发酵进程控制提供了理论依据.     

添加剂促进变性还原溶菌酶复性的作用

研究了多种添加剂促进变性还原溶菌酶复性的作用，考察了添加剂浓度及变性剂盐酸胍浓度对复性收率的影响．结果表明，精氨酸、乙酰胺、丙酮、硫脲及甘油均能有效促进变性溶菌酶复性，并且存在最佳的添加剂浓度使变性溶菌酶的复性收率最大．在促进复性中，乙酰胺等结构类似物与盐酸胍具有相同作用，因此，在降低复性液中盐酸胍浓度的同时，适当提高乙酰胺浓度即可获得较高的复性收率．当盐酸胍浓度为0．2mol／L时，复性收率达到90％时的乙酰胺浓度为2mol／L，但降低盐酸胍浓度至0．06mol／L时，达到相同变性收率的乙酰胺浓度需要4mol／L．甘油与盐酸胍存在着协同作用，在一定浓度的盐酸胍存在下，添加适量的甘油能获得较高的复性收率．     

温度、酸碱度和变性剂对黄花石蒜凝集素活性和构象的影响

采用荧光光谱研究了不同温度、pH和变性剂对黄花石蒜凝集素（Lycoris aurea agglutinin,简称LAA）凝血活性和分子构象的变化关系,结果表明：LAA具有较强的温度和酸碱度的耐受性,经过3种变性剂的处理都能使LAA分子构象发生不同程度的变化并导致活性的丧失,浓度为6 mol/L的盐酸胍和脲,20 mmol/L的SDS可以使LAA完全丧失凝血活性,荧光光谱的变化表明了这种变性过程具有阶段性.     

变性剂和巯基修饰对黄精凝集素II构象和活性的影响

采用圆二色谱、荧光光谱,研究了黄精凝集素II(PolygonatumcyrtonemaHua.LectinII,PCLII)在4mol/L和6mol/L盐酸胍中,以及巯基修饰后,其活性和分子构象的变化关系.研究结果表明:PCLII是一种稳定的蛋白质,巯基修饰剂虽不影响其活性,但可使其分子构象发生变化,去除修饰剂后其结构部分能够恢复.在4mol/L盐酸胍中,PCLII活性及构象可发生很大变化,去除盐酸胍后其活性恢复;在6mol/L盐酸胍中,呈现典型的无规卷曲构象,活性完全丧失,去除盐酸胍后活性仍不能恢复,表明活性中心已遭到不可逆的破坏.     

重组人干扰素α2b和胸腺肽αl融合蛋白的分离纯化

考察了大肠杆菌E.coli表达的重组人干扰素α2b和胸腺肽αl融合蛋白包涵体的变性、复性及融合蛋白的分离纯化过程。实验结果表明：包涵体经7mol/L盐酸胍,10mmol/L DTT变性;1mol/L尿素,2mmol/L还原型谷胱甘肽,0.2mmol/L氧化型谷胱甘肽脉冲加样稀释复性;金属螯合层析收集0.3mol/L咪唑洗脱峰,冷干后经重组肠激酶30℃酶切24h、Sephadex G50 柱纯化,可得到纯度达90%的重组人干扰素α2b和胸腺肽αl融合蛋白,且最终目的融合蛋白产量达68mg/g干菌体。     

罗非鱼脯氨酸内肽酶的分离及抑制剂对其的作用机制

采用硫酸铵盐析及柱层析技术,从罗非鱼肌肉中分离纯化得到分子质量约为85 ku的脯氨酸内肽酶(prolyl endopeptidase,PEP)。通过肽质量指纹质谱分析,获得13个肽片段,含128个氨基酸残基,结果显示,与伯氏朴丽鱼(Haplochromis burtoni)的PEP完全一致。该酶特异分解荧光底物Suc-Gly-ProMCA和Suc-Gly-Pro-Leu-Gly-Pro-MCA,PEP特异性抑制剂SUAM-14746和丝氨酸蛋白酶抑制剂PMSF可以抑制该酶的活性。PEP催化Suc-Gly-Pro-MCA水解反应的活化能(Ea)为47.42 k J/mol。SUAM-14746对PEP表现为竞争性抑制作用,抑制常数(KI)为1.91μmol/L。金属离子Zn~(2+)和Cu~(2+)对PEP的抑制类型均为混合型抑制,其中对游离酶的抑制常数(KI)分别为1.80 mmol/L和0.07 mmol/L,对酶-底物络合物的抑制常数(KIS)分别为2.33 mmol/L和1.17 mmol/L。     

曲酸作为化妆品添加剂的增白作用机理研究

以曲酸为效应物,研究对酪氨酸酶的单酚酶和二酚酶活力的影响.结果表明,曲酸对酪氨酸酶的单酚酶和二酚酶活性均有抑制作用,其效应为可逆抑制效应.测定导致单酚酶活力和二酚酶活力下降50%的抑制剂浓度(IC50)分别为31.0和20.0μmol/L.曲酸对酪氨酸酶的单酚酶的迟滞时间有明显的延长效应,60μmol/L曲酸使得单酚酶的迟滞时间从52s延长到390s.曲酸对二酚酶的抑制作用表现为混合型抑制类型,抑制常数KI和KIS分别为13.0和100.0μmol/L.曲酸和酶的结合导致天然酶的内源荧光的量子产率下降,但荧光发射峰没有位移.通过曲酸对酪氨酸酶的抑制作用研究阐明曲酸作为化妆品添加剂的增白作用机理.     

4-(4-羟基苯基)乙基儿茶酚作为尿素酶抑制剂的机理

4-(4-羟基苯基)乙基儿茶酚是一种新型幽门螺旋杆菌尿素酶抑制剂,运用酶动力学研究方法,对它的抑制机理、抑制类型进行探讨.实验结果表明,4-(4-羟基苯基)乙基儿茶酚是尿素酶的竞争性抑制剂,抑制常数Ki为1.48 μmol/L,为其在抗胃炎、胃溃疡方面的应用以及进一步的结构优化奠定了理论基础.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-