Two-dimensional lattice Monte Carlo simulation of the compatibility of A/B/functionalized A ternary polymer mixtures coupled with chemical reaction

Compatibility of A/B and functionalized A ternary polymer mixtures was studied by Monte Carlo simulation in a two-dimensional lattice. Polymer A was a nonreactive polymer, whereas polymer B was a reactive polymer and immiscible with polymer A. Functionalized polymer A could react with the end group of polymer B, leading to the formation of block copolymers. Simulation results showed the phase domain sizes dropped considerably with increasing functionalized polymer A content, indicating that the compatibility between polymer A and B could be markedly improved with the introduction of functionalized polymer A. Moreover, it was shown that the resulting block copolymers tended to distribute at the phase interface between polymer A and B, and the block copolymer conformation depended on the structures of polymer B and functionalized polymer A. In case 1, i.e., both polymer B and functionalized polymer A were with single end group, it could be found that the block A and block B of resulting A–B copolymer inserted into polymer A and polymer B phase domains, respectively. In case 2, i.e., functionalized polymer A was with single end group and polymer B was with double end groups, it was found that the resulting A–B–A triblock copolymer tended to connect two neighbor separated polymer A phase domains. However, in case 3, namely functionalized polymer A was with double end groups and polymer B was with single end group, it was found that the resulting B–A–B triblock copolymer was likely to form a folding conformation. These lead to the different compatibilizing effects for different polymer structures. Comparing with case 1 and case 2, functionalized polymer A with double end groups (case 3) had less effective to compatibilize the A/B polymer blends. For the purpose of comparison, same simulations were carried out in a three-dimensional lattice. The results showed the compatibility behavior of the mixtures was similar to those in the two-dimensional lattice with the addition of functionalized polymer A. However, the conformation of the resulting block copolymers was different from that in the two-dimensional lattice.     

Isotachophoretic determination of 2-5A phosphodiesterase

Together with 2-5A synthetase and ribonuclease L, 2-5A phosphodiesterase belongs to the 2-5A system, which plays an important role in the action of interferon. Analytical capillary isotachophoresis was used for the determination of 2-5A phosphodiesterase activity. Enzyme assay was optimized using snake venom phosphodiesterase as a source of 2-5A phosphodiesterase activity. The 2-5A trimer core was used as a substrate. Enzyme activity was determined in time- and concentration-dependent reactions. In addition, 2-5A phosphodiesterase activity was determined in lysates of mononuclear blood cells.     

Peptidolipid as binding site of acetylcholinesterase: molecular recognition of paraoxon in Langmuir films

Peptidolipid C18H35O (stearoyl)-Phe-Trp-Ser-His-Glu (peptidolipid A) was synthesized and spread at the air-water interface to study the interaction with an organophosphorus compound. Paraoxon, sodium dihydrogen phosphate, or 4-nitrophenyl phosphate disodium was added to the subphase, but only paraoxon changed the surface pressure-area (pi-A) isotherm of peptidolipid A. This indicated a specific interaction between paraoxon and peptidolipid A. To clarify which amino acid residue of peptidolipid A was responsible for the interaction, peptidolipid B, namely, C18H35O-Gly-His-Ser-Glu-Glu, was synthesized and studied as a Langmuir film. The difference between the pi-A isotherms of peptidolipid B in the absence and presence of paraoxon in the subphase was minimal; consequently, the presence of amino acids phenylalanine (Phe) and tryptophan (Trp) in peptidolipid A may explain the interaction between peptidolipid A and paraoxon. The compression-decompression cycles and kinetic studies of peptidolipid A showed that the Langmuir film was stable. The in situ optical properties of the peptidolipid A Langmuir film such as UV-vis and fluorescence spectroscopies were examined to elucidate the interaction between peptidolipid A and paraoxon. UV-vis absorption of peptidolipid A was investigated in the presence and absence of paraoxon in the subphase. The emission maximum of fluorescence of Trp in peptidolipid A was observed at 351 nm on pure water, and the band intensity decreased when the concentration of paraoxon increased in the subphase. This suggested that the Trp was involved in the molecular recognition process. Epifluorescence micrographs showed domains of peptidolipid A on the pure water subphase. In the presence of paraoxon in the subphase, the Langmuir film of peptidolipid A showed a homogeneity, which was another indication of the recognition between paraoxon and peptidolipid A.     

尼泊金乙酯分子印迹固相萃取小柱的研制及应用

研制了一种对尼泊金乙酯具有特异性识别性能的分子印迹固相萃取小柱。用本体聚合法制备尼泊金乙酯分子印迹聚合物,通过静态平衡吸附实验及固相萃取实验表征其固相萃取性能,并结合UV法对滴眼液中的尼泊金乙酯进行测定。结果显示,尼泊金乙酯模板聚合物的吸附能力强于空白聚合物;印迹固相萃取柱对尼泊金乙酯标准溶液(0.04mmol/L)一...     

An important role for peroxiredoxin II in survival of A549 lung cancer cells resistant to gefitinib

Redox adaptation is an important concept that explains the mechanisms by which cancer cells survive under persistent endogenous oxidative stress and become resistant to certain anticancer agents. To investigate this concept, we determined the expression levels of peroxiredoxins (Prxs), antioxidant enzymes in drug-resistant non-small cell lung carcinoma cells. Prx II was remarkably increased only in A549/GR (gefitinib-resistant) cells compared with A549 cells, consistent with methylation/demethylation. Prx II was highly methylated in the A549 cells but was demethylated in the A549/GR cells. The elevated expression of Prx II resulted in the downregulation of reactive oxygen species (ROS) and cell death and upregulation of cell cycle progression in the A549/GR cells. When Prx II mRNA in the A549/GR cells was knocked down, the levels of ROS and apoptosis were significantly recovered to the levels of the controls. In addition, signaling molecules involved in apoptosis were increased in the A549/GR-shPrx II cells. There was no difference in the expression of MAPK/ERK between the A549/GR cells and A549/GR-shPrx II cells, but the phosphorylation of JNK was increased in the A549/GR cells and was markedly decreased in the A549/GR-shPrx II cells. Colony number and tumor growth were significantly decreased in the A549/GR-shPrx II cells compared with the A549/GR cells. Our findings suggest that Prx II has an important role in cancer cell survival via the modulation of signaling molecules involved in apoptosis and the phosphorylation of JNK by the downregulation of ROS levels in A549/GR cells.     

小孔沸石微结构的CO_2吸附表征

以3种已知结构的小孔沸石3A、4A和5A为研究对象,以N2和CO2为吸附质,通过吸附数据测定,研究了小孔沸石微孔结构的吸附表征方法.结果表明,N2吸附无法检测4A沸石的孔,而CO2吸附可以检测.对于4A和5A沸石,在35s内CO2吸附就可以达到平衡.HK(Horvath-Kawazoe)柱状模型不能表征4A和5A沸石的孔结构,但是HK球形模型可以,基于最大吸附量、D-A(Dubinin-Astakhov)方程和Langmuir-Freundlich模型计算了4A和5A沸石的微孔孔容,其中根据最大吸附容量和D-A方程计算的微孔孔容与文献值最接近.     

Long-distance radical cation migration in duplex DNA: the effect of contiguous A.A and T.T mismatches on efficiency and mechanism

A series of DNA oligomers was prepared. Each oligomer contained an anthraquinone group (AQ, sensitizer) covalently linked at a 5'-end and two GG steps that surrounded a variable region. The variable region was composed of A.T base pairs or A.A or T.T mismatches. Irradiation of the AQ injected a radical cation (hole) into the DNA that migrated through the duplex, being trapped by reaction with H2O of O2 at the GG steps. The effect of substituting A.A or T.T mismatches for Watson-Crick base pairs was examined. For A.A mispairs, charge transfer through the mismatch region was as efficient as through normal DNA. For the T.T mismatches, radical cation transport was strongly distance-dependent. These findings suggest that A.A mismatches form a zipper-like motif, and charge transport proceeds by a hopping mechanism. In contrast, charge transport through the T.T mismatches (where there are no purines) may proceed by quantum mechanical tunneling.     

Determination of Bisphenol A Using an Electrochemical Sensor Based on a Molecularly Imprinted Polymer-Modified Multiwalled Carbon Nanotube Paste Electrode

A novel electrochemical sensor for bisphenol A was developed through the combination of a molecular imprinting technique with a multiwalled carbon nanotube paste electrode. A molecularly imprinted polymer and nonimprinted polymer were synthesized in the presence and absence of bisphenol A, and then used to prepare the electrode. The bisphenol A imprinted polymer was applied as a selective recognition element in the electrochemical sensor. Differential pulse voltammetry was used to characterize the electrochemical behavior of bisphenol A at the modified electrodes. The results showed that the imprinted sensor had highest response for bisphenol A. Parameters including the carbon paste composition, pH, and adsorption time for the imprinted sensor were optimized. Under the optimized conditions, the differential pulse voltammetry peak current was linear with the concentration of bisphenol A from 0.08 to 100.0 µM, with a detection limit of 0.022 µM. The imprinted sensor for bisphenol A exhibited good selectivity, stability, and reproducibility. This sensor was successfully used for the determination of bisphenol A in real water samples.     

三元无皂乳液共聚合动力学及其模型的研究

以苯乙烯（ Ｓｔ） 和甲基丙烯酸甲酯（ Ｍ Ｍ Ａ） 为主单体,以丙烯酸（ Ａ Ａ） 为功能单体进行了无皂乳液批量共聚合．考察了功能单体浓度、引发剂过硫酸铵（ Ａ Ｐ Ｓ） 浓度及聚合温度对其动力学行为的影响．建立了转化率 时间关系曲线的模型函数——— Ｇａｍ ｍａ 积分函数,用它拟合了转化率 时间关系曲线,获得了聚合过程的重要特征参数,如平均成核速率（ Ｎ Ｖ） ,聚合最大速率（ Ｍ Ｖ） 和平稳期平均聚合速率（ Ａ Ｖ） 及成核结束和聚合进入完成期对应的转化率．同时对聚合速率与以上各聚合参数的关系数据进行了非线性拟合,得到了它们之间的关系式．研究发现拟合误差很小,成核结束时转化率在１５ ％ 以内,成核及聚合速率均随以上参数增大而增大,引发剂过硫酸铵在聚合过程中起决定作用．     

Regulation of coenzyme a transferase and acetoacetate decarboxylase activities in clostridium acetobutylicum

The activity of two enzymes involved in acetone production in Clostridium acetobutylicum, acetoacetate decarboxylase and coenzyme A transferase, was studied under acidogenic or solventogenic conditions. Acetoacetate decarboxylase activity was low under acidogenic conditions and after pyruvate addition. Under the same conditions, coenzyme A transferase activity was high. A mutant which lacked acetoacetate decarboxylase activity but was positive for coenzyme A transferase activity was isolated.     

Sugar-sensitive thin films composed of concanavalin A and sugar-bearing polymers.

Layered thin films composed of concanavalin A (Con A) and sugar-bearing polymers were prepared by a layer-by-layer deposition of Con A and the polymer on a solid surface. The sugar-induced disintegration was studied. Con A-polymer layered films could be successfully prepared using a maltose-bearing polymer (PV-MA), while melibiose- and glucose-bearing polymers (PV-MEA and PV-G) did not afford a layered film, due to a weak affinity of PV-MEA and PV-G to Con A. The Con A/PV-MA layered film was stable in pH 7 and 8 solutions, while in a pH 6 medium the film was slightly unstable. The Con A/PV-MA film was disintegrated upon the addition of sugars in solution owing to a preferential binding of the sugars to the binding site of Con A in the film. The disintegration rate was dependent on the type of sugar and its concentration. The Con A/PV-MA film was disintegrated rapidly upon the addition of methyl alpha-D-mannopyranoside, while the rate was slower upon the addition of the same concentration of D-mannose, D-glucose and methyl alpha-D-glucopyranoside. The present system may be useful for constructing sensitive devices that can release a drug or other functional molecules in response to sugars.     

Ligand-based combinatorial design of selective purinergic receptor (A2A) antagonists using self-organizing maps

A virtual screening procedure based on a topological pharmacophore similarity metric and self-organizing maps (SOM) was developed and applied to optimizing combinatorial products functioning as P(1) purinergic receptor antagonists. The target was the human A(2A) receptor. A SOM was developed using a set of biologically tested molecules to establish a preliminary structure-activity relationship. A combinatorial library design was performed by projecting virtually assembled new molecules onto the SOM. A small focused library of 17 selected combinatorial products was synthesized and tested. On average, the designed structures yielded a 3-fold smaller binding constant ( approximately 33 vs approximately 100 nM) and 3.5-fold higher selectivity (50 vs 14) than the initial library. The most selective compound obtained revealed a 121-fold relative selectivity for A(2A) with K(i) (A(2A)) = 2.4 nM, and K(i) (A(1)) = 292 nM. This result demonstrates that it was possible to design a small, activity-enriched focused library with an improved property profile using the SOM virtual screening approach. The strategy might be particularly useful in projects in which structure-based design cannot be applied because of a lack of receptor structure information, for example, in the many projects aiming at finding new GPCR modulators.     

一种苊并杂环有机小分子嵌入DNA的几何学模式研究

利用圆二色谱(CD)、紫外-可见吸收光谱以及荧光光谱等方法对苊并杂环化合物8-氧-8H-苊并[1,2-b]吡咯-9-腈(A1) 与小牛胸腺DNA(CT DNA) 的相互作用进行了研究. 结果表明, 随着n(A1)/n(CT DNA)的变化存在两种不同的几何学结合构型. 当n(A1)/n(CT DNA)值低于0.20时, A1分子与DNA的结合方式是不均一的, 化合物分子以多种角度嵌入到DNA碱基对之间. 表现为A1-DNA复合物的诱导圆二色光谱图上较小的正峰和紫外吸收光谱图缺省等吸收点. DNA的特征圆二色谱图表明, 在n(A1)/n(CT DNA)≤0.20范围内, CT DNA的构象从标准的B型转化为A-like型; 当n(A1)/n(CT DNA)>0.20时, 诱导圆二色光谱由正峰转变为强度大、波形复杂的负峰, 表明A1分子开始堆积到DNA螺旋的表面, 同时DNA的二级结构发生了进一步变化.     

Rapid diagnosis of M. tuberculosis using a piezoelectric immunosensor.

A piezoelectric immunosensor was developed for detecting Mycobacteria Tuberculosis (M. TB). Protein A was modified onto a silver-coated piezoelectric quartz-crystal sensor. Antibodies could be bond onto the crystal surface in an ordered orientation through protein A. An impendence analyzer was employed to record the admittance-frequency curve. The experimental results showed a successful and less-rigid bonding of protein A and antibodies. Compared with other traditional detection methods of TB, the method suggested in this paper was sensitive, selective and effective. The nonspecific response was limited by using control antibody-rabbit anti-honey bee venom (anti-HBV). A glycine-HCI buffer solution (pH = 2.4) was used to release antibodies from a crystal coated with protein A, and 0.5 mg/mL anti-TB was used to remove TB from a crystal that was bonded by an antibody. Good reusability was exhibited. Spike samples of sputum and saliva from normal people with and without adding M. tuberculosis were diagnosed using the proposed method. Good results were obtained.     

Limits of detection and selectivity coefficients of a PVC-based anion-selective electrode

A PVC-based anion-selective electrode was constructed with use of Capriquat as ion-exchanger. Experimental data were in good agreement with E = E(0) - (RT/F)ln(C + radicalC (2) + A (x))/2. The parameter A(x) governs the limit of detection. It was experimentally shown that A(x) was related to the selectivity coefficient K(xy) by K(xy) = A(y)/A(x).     

Remarkable supramolecular catalysis of glycoside hydrolysis by a cyclodextrin cyanohydrin

(6AR,6DR)-6A,6D-di-C-cyano-beta-cyclodextrin (3) was synthesized and shown to catalyze hydrolysis of nitrophenyl glycosides with the reaction following Michaelis-Menten kinetics. At pH 7.4 and 25 degrees C, hydrolysis of 4-nitrophenyl-beta-glucopyranoside (2) was catalyzed with KM = 15 mM, kcat = 8.2 x 10-6 s-1, and kcat/kuncat = 1217. Catalysis was observed with concentration of 3 as low as 10 muM. Hydrolysis of the corresponding alpha-glucoside, alpha-galactoside, alpha-mannoside, and 2-nitrophenyl-beta-galactoside was also catalyzed by 3, with kcat/kuncat ranging from 283 to 2147. A series of analogues of 3 was prepared and investigated for catalysis of the hydrolysis of 2: (6AR,6DR)-6A,6D-di-C-propyl-beta-cyclodextrin (9) was not catalytic, while 6A,6D-di-C-cyano-6A,6D-dideoxy-beta-cyclodextrin (12) had a low catalytic activity (kcat/kuncat = 4). A kcat/kuncat = 48 was found for 6A,6D-dialdehydo-beta-cyclodextrin dihydrate (11). It was proposed that 3 acts by general acid catalysis on the bound substrate.     

Combined phenyl silane and immunoaffinity column cleanup with liquid chromatography for determination of ochratoxin A in roasted coffee: collaborative study

A collaborative study was conducted to evaluate a liquid chromatography (LC) method for ochratoxin A using sequential phenyl silane and immunoaffinity column cleanup. The method was tested at 3 different levels of ochratoxin A in roasted coffee, which spanned the range of possible future European regulatory limits. The test portion was extracted with methanol and sodium bicarbonate by shaking for 30 min. The extract was filtered, centrifuged, and then cleaned up on a phenyl silane column before being eluted from the washed column with methanol-water. The eluate was diluted with phosphate-buffered saline (PBS) and applied to an ochratoxin A immunoaffinity column, which was washed with water. The ochratoxin A was eluted with methanol, the solvent was evaporated, and the residue was redissolved in injection solvent. After injection of this solution onto a reversed-phase LC apparatus, ochratoxin A was measured by fluorescence detection. Eight laboratory samples of low-level naturally contaminated roasted coffee and 2 laboratory samples of blank coffee (< 0.2 ng/g ochratoxin A at the signal-to-noise ratio of 3:1), along with ampules of ochratoxin A calibrant and spiking solutions, were sent to 15 laboratories in 13 different European countries. Test portions of the laboratory samples were spiked at levels of 4 ng/g ochratoxin A, and recoveries ranged from 65 to 97%. Based on results for spiked blank material (blind duplicates) and naturally contaminated material (blind duplicates at 3 levels), the relative standard deviation for repeatability (RSDr) ranged from 2 to 22% and the relative standard deviation for reproducibility (RSDR) ranged from 14 to 26%. The method showed acceptable within- and between-laboratory precision, as evidenced by HORRAT values, at the low level of determination for ochratoxin A in roasted coffee.     

SO2的简并四波混频光谱

简并四波混频（DegenerateFour－WaveMixingDFWM）是一项非线性光谱技术·近年来，它被成功地用于气相痕量原子、分子和自由基的探测［1，2］，而受到人们的关注．DFWM具有亚多普勒的光谱分辨、良好的时间和空间分群等特点，可以实现远距离探测，能有效地排除背景光干扰．此外，由于DFWM技术是直接用于探测体系的吸收，可以应用于无荧光或荧光量子产率低的体系和激发态具有电离和预解离等竞争通道的体系，而这两种体系用传统的激光诱导荧光（LIF）和共振多光子电离（REMPI）方法很难探测．Dreier和Rakestraw曾用DFWM技术探测火…     

AFM and fluorescence spectrascopy investigation for disaggregation of existing Aβ fibrils by baicalein

The wavelength for the peak of fluorescence emission of thioflavin T（ThT） was changed from 445 nm to 481 nm when ThT was added in Aβ solution which indicating theβ-sheet structure of Aβ fibril.The significant decrease in the intensity of fluorescence at 481 nm was observed when the baicalein was added in mixed solution of Aβ and ThT,suggesting that the depolymerization of Aβ fibrils happened and there were Aβfibrils left to react with ThT to keep the initial fluorescence intensity.And the existing Aβfibrils are disaggregated by baicalein in a time- and dose-dependent manner.AFM images of the morphologies of the Aβ_1-42 fibrils obviously changed smaller and more dispersive when baicalein added indicating also the depolymerization of Aβ.The results demonstrate a basis for development of a potential herb drug candidate for the treatment of Alzheimer’s disease（AD）.     

Development of cation exchanger-based nano-CdS hybrid catalyst for visible-light photodegradation of rhodamine B from water

A new polymeric nanocomposite photocatalyst A15-CdS with large spherical beads (0.70-0.80 mm in diameter) was fabricated for efficient Rhodamine B (RhB) photodegradation with facile separation during cyclic runs,and photocorrosion,a congenital drawback of CdS,was successfully inhibited for A15-CdS.The nanocomposite catalyst was obtained by impregnating CdS nanoparticles within porous polymeric cation exchanger A15 through a facile inner-surface deposition.CdS nanoparticles (<20 nm) immobilized in A15 were deliberately distributed within an outside ring-like region of 40-50 m in depth,which is dominant for photoreaction because visible light is not expected to permeate through the inner region of nontransparent A15.As expected,efficient RhB photodegradation by A15-CdS was achieved under visible light irradiation,and large-size A15-CdS beads are expected to result in their facile separation from solution for repeated use.More significantly,negligible photocorrosion for the hybrid catalyst A15-CdS was demonstrated by the constant photodegradation efficiency and negligible CdS loss during five-cycle runs.The results indicated that nano-CdS immobilization within A15 would greatly improve the applicability of CdS nanoparticles in practical environmental remediation.