Self-assembly in mixed dialkyl chain cationic-nonionic surfactant mixtures: dihexadecyldimethyl ammonium bromide-monododecyl hexaethylene glycol (monododecyl dodecaethylene glycol) mixtures

The self-assembly of dialkyl chain cationic surfactant dihexadecyldimethyl ammonium bromide, DHDAB, and nonionic surfactants monododecyl hexaethylene glycol, C(12)E(6), and monododecyl dodecaethylene glycol, C(12)E(12), mixtures has been studied using predominantly small-angle neutron scattering, SANS. The scattering data have been used to produce a detailed phase diagram for the two surfactant mixtures and to quantify the microstructure in the different regions of the phase diagram. For cationic-surfactant-rich compositions, the microstructure is in the form of bilamellar, blv, or multilamellar, mlv, vesicles at low surfactant concentrations and is in an L(beta) lamellar phase at higher surfactant concentrations. For nonionic-rich compositions, the microstructure is predominantly in the form of relatively small globular mixed surfactant micelles, L(1). At intermediate compositions, there is an extensive mixed (blv/mlv) L(beta)/L(1) region. Although broadly similar, in detail there are significant differences in the phase behavior of DHDAB/C(12)E(6) and DHDAB/C(12)E(12) as a result of the increasing curvature associated with C(12)E(12) aggregates compared to that of C 12E 6 aggregates. For the DHDAB/C(12)E(12) mixture, the mixed (blv/mlv) L(beta)/L(1) phase region is more extensive. Furthermore, C(12)E(12) has a greater impact upon the rigidity of the bilayer in the blv, mlv, and L(beta) regions than is the case for C(12)E(6). The general features of the phase behavior are also reminiscent of that observed in phospholipid/surfactant mixtures and other related systems.     

Design of separation length and electric field strength for high-speed DNA electrophoresis

Gel-based DNA separation on microchip will play an important role in future genomic analysis due to its potential for high-efficiency and high-speed. Optimal design of microchip and separation condition is essential to take full advantage of high-speed separation on microchip. Separation length L and electric field strength E, which are crucial for design of microchip system, are focused on in this paper. Simultaneous optimization of L and E was carried out to achieve the most rapid separation. It was shown that the condition of L and E and the shortest separation time is closely related to the shape of resolution Rs surface in a three-dimensional space with axes E, L, and Rs. This surface was investigated, taking sample injection, detector, diffusion, and Joule heating into account. Thermal gradient broadening due to Joule heating helps to produce camber or ridge shape of Rs surface, which is essential for the shortest separation length and separation time. Sample plug length and detection volume should be more carefully controlled in microchip. The property of diffusion coefficient was shown to play a key role in determining Rs surface.     

In Silico Comparison of Low- and High-Risk Human Papillomavirus Proteins

Human papillomavirus (HPV) is an important pathogen which is classified into two, high- and low-risk groups. The proteins of high-risk and low-risk HPV types have different functions. Therefore, there is a need to develop a computational method for predicting these two groups. In the present study, the physiochemical properties of all early (E1, E2, E4, E5, E6, and E7) and late (L1 and L2) proteins in high- and low-risk HPV types have been studied. The concept of receiver operating characteristic analysis and support vector machines methods has been used for comparison of high- and low-risk HPV types. The results demonstrate that amino acid composition, physiochemical, and secondary structure of E2 protein are significantly different between these two groups. The results demonstrate that in silico properties can create useful information to predict high-risk and low-risk HPV types.     

Electrochemical Parametrization in Sandwich Complexes of the First Row Transition Metals

Applying the ligand electrochemical parameter approach to sandwich complexes and standardizing to the Fe(III)/Fe(II) couple, we obtained E(L)(L) values for over 200 pi-ligands. Linear correlations exist between formal potential (E degrees ) and the summation operatorE(L)(L) for each metal couple. In this fashion, we report correlation data for many first row transition metal couples. The correlations between the E(L)(L) of the substituted pi-ligand and the Hammett substituent constants (sigma(p)) are also explored.     

Facile Metalation of Silicon and Germanium Analogues of Thiocarboxylic Acids with a Manganese(II) Hydride Precursor

Synthesis and characterization of the first manganese(II)-containing heavier thiocarboxylate analogues, [L(Dip) Si(?S)OMnL(Dep) ] (4; L(Dip) =CH[C(Me)N(2,6-iPr(2) C(6) H(3) )](2) , L(Dep) =CH[C(Me)N(2,6-Et(2) C(6) H(3) )](2) ) and [L(Dip) Ge(?S)OMnL(Dep) ] (5) are described. They are accessible through reaction of the silicon and germanium analogues of the respective thiocarboxylic acids [L(Dip) E(?S)OH] (E=Si, Ge) with the β-diketiminato (nacnac) manganese(II) hydride precursor [(L(Dep) Mn)(2) (μ-H)(2) ] (3) in high yield. The first Mn nacnac hydride 3 has been prepared by the reaction of manganese bromide [(L(Dep) Mn)(2) (μ-Br)(2) ] (2) with KBEt(3) H. Compounds 4 and 5 represent the first transition-metal heavier thiocarboxylates with the Si?S and Ge?S functionalities. All new compounds are paramagnetic and were characterized by elemental analysis, IR spectroscopy, MS (EI), and single-crystal X-ray diffraction analyses. Due to the N→E (E=Si, Ge) and E=S→Mn donor-acceptor interaction as well as the carboxylate-like π-electron delocalization within the E(S)O moieties, the E?S double bonds in these compounds are resonance stabilized.     

13C-labeled platinum(IV)-carbohydrate complexes: structure determination based on (1)H-(1)H, (13)C-(1)H, and (13)C-(13)C spin-spin coupling constants

The reaction of D-mannose and D-allose with [PtMe(3)(Me(2)CO)(3)]BF(4) 1 in acetone affords complexes [PtMe(3)L]BF(4) 5 and 6 (5, L = alpha-D-mannofuranose; 6, L = beta-D-allofuranose). The coordination mode and conformation of the carbohydrate ligands in 5 and 6 in acetone-d(6) have been determined from an analysis of J(HH), J(CH), and J(CC) in complexes formed using site-specific (13)C-labeled D-mannose and D-allose. These coupling data are compared to those measured in (13)C-labeled complex [PtMe(3)L]BF(4) 2 (L = 1, 2-O-isopropylidene-alpha-D-glucofuranose) and 1, 2-O-isopropylidene-alpha-D-glucofuranose 3, whose solid-state structures are known, and in (13)C-labeled 1,2;5, 6-di-O-isopropylidene-alpha-D-glucofuranose 4. The preferred furanose ring conformations in 2 and 5 are very similar ((3)E/E(4) and E(4)/(o)E/E(1), respectively; eastern hemisphere of the pseudorotational itinerary), with platinum coordination involving O3, O5, and O6 of the saccharide. In contrast, the furanose ring of 6 prefers an (4)E/E(o)/(1)E geometry (western hemisphere of the pseudorotational itinerary) resulting from altered complexation involving O1, O5, and O6. Couplings within the exocyclic fragments of 2, 5, and 6 also support the existence of two different platinum coordination modes. In addition to establishing the structures and conformations of 2, 5, and 6 in solution, one-, two-, and three-bond J(CH) and J(CC) observed in these complexes provide new insights into the effect of structure and conformation on the magnitudes of these couplings in saccharides. Weak platinum(IV) complexation with the carbohydrate conformationally restricts the furanose and exocyclic fragment without introducing undesirable structural strain, thereby allowing more reliable correlations between structure and coupling magnitude.     

鬼臼毒素衍生物的量子化学研究

对若干个鬼臼毒素衍生物进行了量子化学计算,根据其电子结构及有关分析结果,结合它们对体外L1210白血病细胞生长的抑制活性(IC50),讨论了它们的活性部位及构效关系,发现具有较高活性的化合物分子中有三个重要部位：C4位为有效的修饰位点;B环及E环是重要的活性部位,其中B环是接受电子的主要活性部位,其正电性越高,活性越强;E环及其4'位酚羟基氧的负电性越高,活性越强。     

胶束电动毛细管色谱法测定硫酸多粘菌素E药物中的多粘菌素E1和E2

采用胶束电动毛细管色谱法(MECC)对硫酸多粘菌素E药物中的主要成分多粘菌素E1和E2进行了分离,并测定了多粘菌素E1、E2的含量。分别考察了电泳电压、表面活性剂种类、Brij-35(月桂醇聚氧乙烯醚)浓度、乙腈含量、磷酸盐缓冲液的pH值、氯化钠浓度等实验参数对实验结果的影响,从而确定了最佳的分离条件: 电泳电压为10 kV,运行缓冲液为含有30 mmol/L Brij-35、5%(体积分数)乙腈、0.167 mol/L氯化钠的磷酸二氢钠缓冲液(0.01 mol/L,pH 4.1)。在优化的实验条件下,E1和E2得到了较好的分离,分离度达到1.94。以多粘菌素E1为例,柱效和峰面积的日间及日内测定的相对标准偏差(RSD)均小于5%。E1和E2在硫酸多粘菌素E药物中的含量分别为67%和32%。该方法简便、快速、准确、重现性好。     

功能化聚(2,5-二甲氧基苯胺)膜的电化学和电催化性质研究

聚(2，5-二甲氧基苯胺)含有对称的环取代基，其电化学活性可与PAni相比拟．该聚合物具有三种氧化态，即完全还原态(L)、半氧化态(E)和完全氧化态(P)，在伏安曲线上分别于0．19和0．51V处出现L／E和E／P转变峰．掺杂态聚合物和本征态聚合物的氧化还原分别经历L=EH=P和LH=EH=P路径，其中E／P转变峰电位随pH升高而发生负移．铂化的聚合物电极对异丙醇的氧化具有明显的催化作用，且随着扫描时间延长，氧化电流逐渐提高；聚合物与铂微粒相互作用，改变铂微粒的几何结构和电子性质，使催化体系具有良好的催化活性和抗中毒能力．在pH=4．7的缓冲溶液中，该修饰电极对异丙醇氧化仍具有催化活性．聚合物在空气中存放太久(3年)会发生降解，从而影响其电化学性质．     

The direct electrocatalysis of Escherichia coli through electroactivated excretion in microbial fuel cell

Previous reports showed that Escherichia coli (E. coli) undergone an electrochemical activation process can catalyze glucose oxidation in microbial fuel cell (MFC) in the absence of extraneous mediators [T. Zhang, C.Z. Cui, S.L. Chen, X.P. Ai, H.X. Yang, P. Shen, Z.R. Peng, Chem. Commun. (2006) 2257; T. Zhang, Y.L. Zeng, S.L. Chen, X.P. Ai, H.X. Yang, Electrochem. Commun. 9 (2007) 349]. This paper investigates the electron transfer mechanism associated with the direct bioelectrocatalysis of electroactivated E. coli in MFC. It is shown that covering the electrode surface with a filter membrane with pore smaller than the size of E. coli cells hardly changes the fuel cell discharge behaviors and the voltammetric responses in the culture of electroactivated E. coli, indicating that the electron transfer between the electrode and E. coli cells is carried out by soluble compounds in the culture. The GC–MS results indicate that these compounds are excreted by E. coli in MFC, i.e., they are exploitable metabolites.     

Second-order dispersion interactions in π-conjugated polymers

We calculate the ground state and excited state second-order dispersion interactions between parallel π-conjugated polymers. The unperturbed eigenstates and energies are calculated from the Pariser-Parr-Pople model using CI-singles theory. Based on large-scale calculations using the molecular structure of trans-polyacetylene as a model system and by exploiting dimensional analysis, we find that: (1) For inter-chain separations, R, greater than a few lattice spacings, the ground-state dispersion interaction, ΔE(GS), satisfies, ΔE(GS)～L(2)/R(6) for L ? R and ΔE(GS)～L/R(5) for R ? L, where L is the chain length. The former is the London fluctuating dipole-dipole interaction while the latter is a fluctuating line dipole-line dipole interaction. (2) The excited state screening interaction exhibits a crossover from fluctuating monopole-line dipole interactions to either fluctuating dipole-dipole or fluctuating line dipole-line dipole interactions when R exceeds a threshold R(c), where R(c) is related to the root-mean-square separation of the electron-hole excitation. Specifically, the excited state screening interaction, ΔE(n), satisfies, ΔE(n) ～ L∕R(6) for R(c) < L ? R and ΔE(n) ～ L(0)∕R(5) for R(c) < R ? L. For R < R(c) < L, ΔE(n) ～ R(-ν), where ν ? 3. We also investigate the relative screening of the primary excited states in conjugated polymers, namely the n = 1, 2, and 3 excitons. We find that a larger value of n corresponds to a larger value of ΔE(n). For example, for poly(para-phenylene), ΔE(n = 1) ? 0.1 eV, ΔE(n = 2) ? 0.6 eV, and ΔE(n = 3) ? 1.2 eV (where n = 1 is the 1(1)B(1) state, n = 2 is the m(1)A state, and n = 3 is the n(1)B(1) state). Finally, we find that the strong dependence of ΔE(n) on inter-chain separation implies a strong dependency of ΔE(n) on density fluctuations. In particular, a 10% density fluctuation implies a fluctuation of 13 meV, 66 meV, and 120 meV for the 1(1)B(1), m(1)A state, and n(1)B(1) states of poly(para-phenylene), respectively. Our results for the ground-state dispersion are applicable to all types of conjugated polymers. However, our excited state results are only applicable to conjugated polymers, such as the phenyl-based class of light emitting polymers, in which the primary excitations are particle-hole (or ionic) states.     

Study of allelopathic effects of Eucalyptus erythrocorys L. crude extracts against germination and seedling growth of weeds and wheat

Allelopathic materials inside a tree can produce positive or negative change in the survival, growth, reproduction and behaviour of other organisms if they escape into the environment. To assess these effects, this work was carried out to evaluate the allelopathic impact of Eucalyptus erythrocorys L. on seed germination and seedling growth of two weeds: Sinapis arvensis L. and Phalaris canariensis L.; on one cultivated crop: Triticum durum L. Aqueous; and on ethanolic leaf extracts of E. erythrocorys L. The study was effected using four concentrations (10, 20, 25 and 30 μL/mL) while distilled water was used as a control. The results showed that the E. erythrocorys L. crude extracts had an inhibitory effect on seed germination and seedling growth of both studied weeds and wheat. The inhibition rate was increased by the increase in extract concentration. Only ethanolic extracts of E. erythrocorys L. induced a significant inhibition of seed germination of durum wheat. The effect of E. erythrocorys L. crude extracts was more severe on weeds than on durum wheat. These results indicate that the seedling growth, especially radicle elongation, was the more sensitive indicator to evaluate the effects of extracts than was the seed germination.     

Determination of estrogenic steroids in surface water and wastewater by liquid chromatography-electrospray tandem mass spectrometry

An analytical method is presented which permits trace level determination of 17alpha-ethynylestradiol (EE2), 17beta-estradiol (E2), and estrone (E1). Using this method, the estrogenic steroids were analyzed in drinking water, surface water, and wastewater (sewage influents and effluents) at concentrations down to 0.1 ng/L. Sample volumes between 100 and 500 mL are concentrated using automated solid-phase extraction. Analysis is performed by liquid chromatography with detection by tandem mass spectrometry. Applying simple clean-up procedures and internal standard calibration, recovery losses resulting from matrix-dependent ion suppression during electrospray ionization could be compensated for all of the investigated compounds. Recoveries around 100% were obtained for all analytes after correction using the internal standards. Limits of quantification (LOQ) were between 0.1 and 0.4 ng/L for purified sewage, surface, ground, and drinking water and between 1 and 2 ng/L in the case of raw sewage. Water treatment by wastewater treatment plants (WWTPs) or by a surface water treatment plant affected the removal of all estrogenic steroids. Thus, E1, E2, and EE2 were removed in the municipal WWTPs to the extent of 93%, 93%, and 80%, respectively. In the effluents of the WWTP in Ruhleben (Berlin, Germany), E1, E2, and EE2 were detected at the low ng/L level. E2 and EE2 were, however, not present in the Berlin surface water above the LOQ (0.2 ng/L). E1 was the only compound that could be detected in surface water samples. After additional surface water treatment it was still detectable but only at trace-level concentrations with a mean value of 0.16 ng/L.     

Sequence of the amino-terminal region of rat liver ribosomal proteins S4, S6, S8, L6, L7a, L18, L27, L30, L37, L37a, and L39.

The sequence of the amino-terminal region of eleven rat liver ribosomal proteins--S4, S6, S8, L6, L7a, L18, L27, L30, L37a, and L39--was determined. The analysis confirmed the homogeneity of the proteins and suggests that they are unique, since no extensive common sequences were found. The N-terminal regions of the rat liver proteins were compared with amino acid sequences in Saccharomyces cerevisiae and in Escherichia coli ribosomal proteins. It seems likely that the proteins L37 from rat liver and Y55 from yeast ribosomes are homologous. It is possible that rat liver L7a or L37a or both are related to S cerevisiae Y44, although the similar sequences are at the amino-terminus of the rat liver proteins and in an internal region of Y44. A number of similarities in the sequences of rat liver and E coli ribosomal proteins have been found; however, it is not yet possible to say whether they connote a common ancestry.     

Electrophoretic separations of twelve phenothiazines and N-demethyl derivatives by using capillary zone electrophoresis and micellar electrokinetic chromatography with non ionic surfactant

We focused our work on the separation of phenothiazines that are important drugs used for the treatment of psychic diseases. For a better understanding of the metabolism of these solutes, we wanted to separate not only a mixture of 12 phenothiazines but also a mixture containing phenothiazines and their N-demethyl metabolites by capillary electrophoresis. Separations in capillary zone electrophoresis were performed using 3 x 10(-2) mol/L H3PO4 (pH 2.5) but the obtained resolutions were not entirely satisfactory especially with regard to phenothiazine -N-demethyl derivative pairs. To improve the obtained results, we have performed separations by using micellar electrokinetic chromatography. In this approach, we used a running electrolyte containing 3 x 10(-2) mol/L H3PO4 electrolyte (pH 2.5) and octaethylene glycol monododecyl ether (C12E8) as neutral surfactant. By introducing 2 x 10(-3) mol/L C12E8 in the electrolyte, 11 out of 12 phenothiazines have been baseline separated. With respect to the separation of a mixture containing 3 phenothiazines and their 3 demethyl derivatives, we obtained an excellent separation by using a running electrolyte prepared with 7.5 x 10(-4) mol/L C12E8 and 3 x 10(-2) mol/L H3PO4.     

Synthesis and structure of [Zn(OMe)(L)] x [Zn(OH)(L)] x 2(BPh4), L = cis,cis-1,3,5-tris[(E,E)-3-(2-furyl)acrylideneamino]cyclohexane: structural models of carbonic anhydrase and liver alcohol dehydrogenase

Direct reaction of [Zn(OH)(L)]+, L = cis,cis-1,3,5-tris[(E,E)-3-(2-furyl)acrylideneamino]cyclohexane, with methanol gives a mixture of the starting material and [Zn(OMe)(L)]+; structural analysis of the complexes shows that they are models of reactive intermediates in the catalytic cycles of the zinc enzymes carbonic anhydrase and liver alcohol dehydrogenase.     

Antiradical efficiency of 20 selected medicinal plants

The antioxidant system of a plant comprises a group of chemicals that are highly diverse in their sources, effects and uses. These antioxidants are capable of contracting and damaging free radicals. This investigation deals with a screening and comparison of the antioxidant activities of 20 selected medicinal plants and their parts, individually and in combination with vitamins A, C or E, using the DPPH radical scavenging method. Phyllanthus emblica L., Santalum album L., Syzygium cumini L. and Trigonella foenum-graecum L. presented highly significant antiradical efficiency (AE) singly and in combination with either vitamin A, C or E. Further, Curcuma longa L., Momordica charantia L., S. cumini, T. foenum-graecum, Moringa oleifera Lam and S. album have also shown fairly significant AE in a vitamin combination dose of 0.001 mM concentration.     

Adsorption of Poly(ethylene oxide)-Poly(lactide) Copolymers. Effects of Composition and Degradation

The effect of chemical degradation of two diblock copolymers of poly(ethylene oxide) (E) and poly(lactide) (L), E(39)L(5) and E(39)L(20), on their adsorption at silica and methylated silica was investigated with in situ ellipsometry. Steric stablization of polystyrene dispersions was investigated in relation to degradation. Hydrolysis of the poly(lactide) block of the copolymers was followed at different temperatures and pH by using HPLC to measure the occurrence of lactic acid in solution. The block copolymers were quite stable in pH-unadjusted solution at low temperature, whereas degradation was facilitated by increasing temperature or lowering of the pH. Lower degradation rates of E(39)L(20) where observed at low temperature in comparison with those of E(39)L(5), whereas the degradation rates of the copolymers were quantitatively similar at high temperature. The adsorption of the copolymers at methylated silica substrates decreased with increasing degree of degradation due to the reduction in the ability of hydrophobic block to anchor the copolymer layer at the surface. At silica the adsorption initially increased with increasing degradation, particularly for E(39)L(20) due to deposition of aggregates onto the surface. After extensive degradation the adsorption of the copolymers at both silica and methylated silica resembled that of the corresponding poly(ethylene oxide) homopolymer. Overall, it was found that the eventual reduction in adsorption occurred at a lower degree of degradation for E(39)L(5) than for E(39)L(20). Mean-field calculations showed a reduced anchoring for the block copolymers with decreasing poly(lactide) block length at hydrophobic surfaces. In accordance with this finding, it was observed that polystyrene dispersions were stabilized by E(39)L(20) or E(39)L(5) in a way that depended on both the lactide block length and the degree of degradation. Upon degradation of the hydrophobic block, stabilization of the polystyrene dispersions was maintained initially, but eventually degradation resulted in destabilization. The average residual copolymer concentration required for stabilization of the polystyrene dispersions was much higher than the corresponding concentration of intact copolymer required for stabilization. Copyright 2001 Academic Press.     

Analysis of 17β-Estadiol from Sewage in Coastal Marine Environment by Surface Plasmon Resonance Technique

In this study, surface plasmon resonance(SPR) for monitoring 17β-eatradiol( E2 ) was developed. The small molecule E2 was immobilized on a CM5 sensor chip for an indirect competitive immunoassay to detect F2. The SPR response based on the antigen-antibody reaction was measured by injecting the sample solution into the flow system.The limitation of detection was 0.445 μg/L. The developed SPE-SPR system was applied to analyze the seawater samples. Recovery of E2 was 91.6%-93.1%. Relative standard deviations(RSD) for the E2 assay were between 10.9%-15.1% ( n = 3). The range of determination of E2 samples from the sewage in the coastal marine environment was between ND(lower than detection limit) and ca. 11.78 ng/L.     

固相萃取-衍生化气相色谱/质谱法测定制药厂污水中的环境雌激素

采用固相萃取-衍生化气相色谱/质谱法(GC/MS)测定某制药厂污水中的雌酮(E1)、雌二醇(E2)、雌三醇(E3)和乙炔基雌二醇(EE2)4种雌激素化合物。样品经固相萃取柱萃取富集及双(三甲基硅烷基)三氟乙酰胺(1%三甲基氯硅烷)（BSTFA(1%TMCS)）衍生化后进行GC/MS分析。该法对4种目标物的检出限为1.8～4.7 ng/L,相对标准偏差为2.3%～9.1%(n=8)。目标化合物的加标回收率为（94.0±2.9）%～（101±3.8）%,说明该方法能较好地应用于污水中雌激素化合物的定量检测。通过对某制药厂污水中的雌激素进行定量分析,发现污水中乙炔基雌二醇和雌酮质量浓度分别达396.6 和39.9 ng/L;经过传统的厌氧兼氧好氧生物处理后,污水中的环境雌激素的去除率仅为35%～40%,说明传统的污水处理工艺对去除污水中雌激素效果并不明显,需要改进。