微量热法研究硒对砷在大肠杆菌生长中的联合作用

以大肠杆菌为模型生物,结合生物学的细菌培养方法,用微量热法研究了硒代吗啉与亚砷酸钠对大肠杆菌的联合作用,初步探讨了它们之间的作用机理.结果表明,硒代吗啉和亚砷酸钠之间既有拮抗作用,也有协同作用,这依赖于两者的相对浓度.硒与砷的作用机理可能与细菌生长代谢过程中酶的合成有关.     

Lewis acidity/basicity of pi-electron systems: theoretical study of a molecular interaction between a pi system and a Lewis acid/base

Molecular interactions between pi systems having different pi-electron character (benzene, hexafluorobenzene, and borazine), and a Lewis acid/base (borane and ammonia) were theoretically studied. An attractive interaction between benzene, the electron-rich pi system, and borane was observed. On the other hand, repulsive interactions between benzene and ammonia was observed when the lone pair of nitrogen points toward the benzene ring. In contrast, an attractive interaction between hexafluorobenzene, an electron-deficient pi system, and ammonia was observed. Unexpectedly, a weak attractive interaction between hexafluorobenzene and borane was also observed. Borazine shows an interaction both to borane and ammonia. The attraction between the nitrogen atom of borazine and borane was larger than that between the boron atom of borazine and ammonia.     

机械振动理论方法与直链烷烃性质研究

将直链烷烃分子看成是一个多自由度振动系统,用机械振动理论中的传递矩阵法计算了C2～C32直链烷烃的固有频率,分析了固有频率随化合物结构单元的变化规律.发现各阶固有频率中的基频与直链烷烃的结构型性质呈现出优良的相关性,用各阶固有频率之和表示的总频与直链烷烃的加和型性质也呈现出优艮的相关性,将两者组合后还能够反映直链烷烃的凝聚型性质的变化规律.在此基础上建立了直链烷烃的物化性能与基频和总频之间的定量相关模型.用该模型对直链烷烃的电离能、沸点、临界温度、临界压力、密度、粘度、标准生成焓、离子标准生成焓、常压热容、折光指数等10种不同类型性质的实验数据进行回归分析,相关系数均大于0.999.     

气相色谱检测甘蔗中乐果和特丁磷的残留量

甘蔗经加速溶剂萃取仪萃取,应用气相色谱仪定量法检测乐果和特丁磷,建立了定量检测甘蔗中乐果和特丁磷的快速、准确、高灵敏度的方法。经方法学验证,该方法对乐果最低检出限(LOD)为0.01 mg/kg,特丁磷LOD为0.05 mg/kg。乐果和特丁磷在1.0～100.0μg/mL的线性范围内,相关系数r>0.999 9。乐果回收率为91.5%～99.6%,相对标准偏差(RSD)为1.9%～3.2%,特丁磷回收率为81.0%～93.2%,RSD为2.0%～3.5%。结果表明,该检测方法灵敏度高、操作简单、定量准确、测定浓度范围广,是甘蔗样品中乐果和特丁磷含量检测的理想方法。     

肌醇与牛血清白蛋白相互作用的荧光光谱研究

应用荧光光谱研究了肌醇与牛血清白蛋白(BSA)分子间的相互作用;求出了猝灭常数,讨论了肌醇对BSA构象的影响,并依据能量转移理论确定了肌醇与蛋白的最近距离.结果表明,肌醇与BSA两者间的相互作用为单一的动态猝灭过程.     

Optimization of operating conditions in a high-shear mixer using dem model: determination of optimal fill level

For the purpose of evaluating optimal fill level of starting materials in a high-shear mixer, discrete element method (DEM) simulation was conducted to visualize kinetic status between particles. The simulation results obtained by changing fill levels were used to determine solid fraction of particles, particle velocity, particle velocity vector, and kinetic energy and discuss the flow pattern. Optimal fill level was obtained from the information on these matters. It was pointed out that understanding the kinetic energy between particles in an agitating vessel was effective in determining the optimal fill level. Granulation experiment was conducted to validate the optimal fill level obtained by the simulation, confirming the good agreement between these two results. It was pointed out that determination of kinetic energy between particles through the simulation was effective in obtaining an index of the kinetic status of particles. Further, it was confirmed that the simulation could provide more information than conventional granulation experiments could provide and also helpful in optimizing the operating conditions.     

On the exchange of cyanide with acetonitrile. A test of theoretical calculations

- The theoretically predicted formation of an adduct between cyanide and anhydrous acetonitrile was tested experimentally; no evidence for such a complex was found. The previously reported radioactivity loss in the reactions of cyanide - ¹⁴C in acetonitrile solutions was possibly due to protonation and loss of hydrogen cyanide, since no exchange between cyanide and acetonitrile was evidenced within the sensitivity limits of ¹³C labelling. Potassium cyanide and carbonate in the presence of 18-crown-6 ether catalyze the H/D exchange between acetonitrile and trideuteroacetonitrile.     

苯-氯苯二元系的折射分析

研究了液体二元系的折射分析法。发现苯-氯苯的折射率和组成间有良好的线性关系。得出了线性方程。利用方程测得的结果和实际值十分吻合。     

糖尿病患者血清中5种元素分析

用原子吸收分光光度法对８４例糖尿病患者及５０例健康人的血清中微量元素锌,铜,铁及宏量元素钙,镁的含量进行了测定分析。结果表明：糖尿病组血清中锌,铁明显低于对照组,血清中铜高于对照组,经ｔ检验差别有显著意义Ｐ〈０．０５或Ｐ〈０．０１）。     

光谱-分子模拟法分析杨梅素与人血清白蛋白的分子作用机制

在模拟生理条件下,用多种光谱法结合分子对接法测定了杨梅素(MY)与人血清白蛋白(HSA)的相互作用.研究结果表明,MY能够明显猝灭HSA的荧光,MY与HSA的相互作用为复合式静态结合过程,结合强度较强.热力学和分子对接结果表明,MY与HSA是自发结合的,维持MY与HSA的相互作用力主要是氢键和范德华力.能量转移结果表明...     

A pulse radiolysis study on electron affinity of piperonal

Many processes in organisms are involved in elec-tron transfer reaction, and radioactive effect, preven-tion and sensitization of radioactive injury are in-volved in it too. There exists a quantitative relation-ship between one-electron reduction potentia…     

绝热法研究己内酰胺阴离子聚合尼龙动力学

采用己内酰胺钠盐、N-75缩二脲作为反应催化体系, 确定反应温度在145-160 ℃之间, 通过计算得到动力学参数: 反应级数为准一级、活化能在73.2-77.1 kJ·mol-1之间、指前因子在2.9×1011-3.6×1011 mol1-n·s-1范围内. 本实验条件下测定并计算的反应热为134.5-137.3 J·g-1, 与文献值(138.6 J·g-1)吻合. 并在前人基础上修正并建构了己内酰胺阴离子绝热反应动力学模型, 对反应过程的模拟结果与实验数据基本吻合, 从而证明了本模型的正确合理.     

The Effect of pH Difference Between Two Phases on the Partition of Lysozyme in Aqueous Two-Phase System

Aqueoustwo-phasesystems(ATPS)areformedwhentwoaqueoussolutionsofhydrophilicpolymersorapolymerandasaltaremixedathighconcentration.Forthechargedproteins,AlbertssonhasdevelopedtheclassicalmodelfortheelectrochemicalpartitioninginATPSfInK,=lnK, (Z,F/RT)Arp(l)HereK,denotesthepartitioncoefficientofproteins,InK,includesalltheotherfactorsaffectingproteinpartitioning,and(Z,F/RT)A(PistheelectrostatictermasaproductofproteinsurfacechargeZPandAam,theelectrostaticpotentialdifferencebetweenthetwopha…     

Elucidation of solid-state complexation in ground mixtures of cholic acid and guest compounds

The solid-state complexation between cholic acid (CA) and either methyl p-hydroxybenzoate (MPB) or ibuprofen (IBP) was investigated. Powder X-ray diffractometry, IR spectroscopy and thermal analysis suggested the complex formation between CA and MPB as well as between CA and IBP by co-grinding method. The stoichiometry of CA-MPB was 1 : 1 while that of CA-IBP was 2 : 1, reflecting the effect of guest size on complex formation. The guest compounds were assumed to be included in the channel of complexes formed by hydrogen bonds among CA molecules.     

Substoichiometric precipitation of fluoride with lanthanum

The substoichiometric precipitation of fluoride with lanthanum was studied by using¹⁸F and¹⁴⁰La tracers and it was found that fluoride could be precipitated substoichiometrically with lanthanum and the reaction ratio between fluoride and lanthanum was 3∶1. The pH range at which fluoride can be separated substoichiometrically with lanthanum is between 2 and 8. Barium and indium interfere in the precipitation of fluoride, sodium, copper and manganese, however, not. Fluorosilicate can also be precipitated substoichiometrically by using lanthanum as a precipitant and the reaction ratio between fluorosilicate and lanthanum was 1∶2. This separation was applied for the determination of oxygen in silicon crystals. The concentration of oxygen measured in some silicon crystals was between 5 and 27 ppm and in good agreement with those by non-destructive method and infrared spectrophotometry.     

长链支化聚丙烯的非线性流变行为

通过大幅振荡剪切试验方法, 研究了长链支化聚丙烯的非线性流变学行为, 揭示了长链支化结构与非线性黏弹响应的关系. 利用傅里叶变换流变学方法得到试样的三次倍频相对振幅I_3/1与应变的标度关系, 用于界定线性聚丙烯和长链支化聚丙烯非线性流变行为的差异, 并定义了非线性系数来量度长链支化程度. 在高应变下, I_3/1与应变的变化关系可以进一步描述长链支化在非线性流场下的特性, 并得到了长链支化程度与其非线性响应之间的变化关系. 通过应力波的Lissajous曲线分解, 发现了环内和环间黏弹性的差异, 长链支化结构在大应变流场下的非线性黏弹性响应弱于线性结构, 支化程度越高非线性响应越弱.     

Effects of hydrogen bonds and the solubility of onium hexafluorosilicates

The relationship between the water solubility of hexafluorosilicates with different types of onium cations and the characteristics of interionic H-bonds in their structures was analyzed. The antibate correlation between the solubility and the number of short interionic H-bonds was revealed for salts with aromatic heterocyclic and arylammonium cations.     

Properties of branched confined polymers

A model of star-branched polymer chains confined in a slit formed by two parallel surfaces was studied. The chains were embedded to a simple cubic lattice and consisted of f=3 branches of equal length. The macromolecules had the excluded volume and the confining surfaces were impenetrable for polymer segments. No attractive interactions between polymer segments and then between polymer segments and the surfaces were assumed and therefore the system was a thermal. Monte Carlo simulations were carried out employing the sampling algorithm based on chain's local changes of conformation. Lateral diffusion of star-branched chains was studied. Dynamic properties of star-branched chains between the walls with impenetrable rod-like obstacles were also studied and compared to the previous case. The density profiles of polymer segments on the slit were determined. The analysis of contacts between the polymer chain and the surfaces was also carried out.     

Understanding cellulose dissolution: effect of the cation and anion structure of ionic liquids on the solubility of cellulose

The effect of ionic liquids (ILs) on the solubility of cellulose was investigated by changing their anions and cations. The structural variation included 11 kinds of cations in combination with 4 kinds of anions. The interaction between the IL and cellobiose, the repeating unit of cellulose, was clarified through nuclear magnetic resonance (NMR) spectroscopy. The reason for different dissolving capabilities of various ILs was revealed. The hydrogen bonding interaction between the IL and hydroxyl was the major force for cellulose dissolution. Both the anion and cation in the IL formed hydrogen bonds with cellulose. Anions associated with hydrogen atoms of hydroxyls, and cations favored the formation of hydrogen bonds with oxygen atoms of hydroxyls by utilizing activated protons in imidazolium ring. Weakening of either the hydrogen bonding interaction between the anion and cellulose, or that between the cation and cellulose, or both, decreases the capability of ILs to dissolve cellulose.     

三聚氰胺对DNA潜在损伤作用的研究

在生理酸度条件下(pH 7.4),采用溴化乙锭(EB)为荧光探针的荧光光谱法、I-离子荧光猝灭效应、DNA熔点和粘度效应等手段,研究了三聚氰胺与DNA的相互作用。随着DNA的加入,三聚氰胺的荧光强度明显减小而且三聚氰胺能够猝灭DNA-EB复合物的荧光,说明三聚氰胺能够竞争置换EB而与DNA作用;三聚氰胺的加入使得DNA的粘度增大,DNA-EB的熔点降低;DNA的加入减小了I-对三聚氰胺荧光的猝灭程度。三聚氰胺以嵌插方式作用于DNA的亲核位点,意味着三聚氰胺进入生物体后有可能通过形成DNA加合物的形式造成DNA损伤,从而最终导致基因突变。