Monte Carlo simulations of systems of rodlike molecules with semiflexible terminal groups

The results of Monte Carlo simulations of systems of rodlike molecules with semiflexible terminal groups are compared with those of systems with terminal groups at a fixed angle τ with respect to the rigid core and with those of a system containing the rigid cores alone in the same total volume. The nematic/isotropic transition temperature decreases with increasing flexibility or with increasing τ. For semiflexible groups, the transition is coupled with a conformational change favouring more extended conformations in the nematic phase. The results of the simulations are discussed in connection with those obtained for similar models in the recent literature and with the predictions of the Maier‐Saupe and Flory‐Ronca‐Irvine theories.     

表面等离子体子共振传感器用于研究不同材质包裹的磁性纳米粒子性质

利用自行设计组装的以白色发光二极管为光源的表面等离子体子共振传感器实验装置, 检测了不同材质包裹的磁性纳米粒子连接靶向DNA与生物素化DNA探针的结合程度. 结果表明, 与聚苯乙烯磁性微球连接的靶向DNA相比, Fe3O4@SiO2核壳式纳米微球连接的靶向DNA与生物素化的DNA探针结合速率较快, 且其相对标准偏差较小.     

乳腺癌术前灰阶超声与彩色多普勒超声联合应用对预后的预测价值

目的探究乳腺癌术前灰阶超声与彩色多普勒超声联合应用对预后的预测价值。方法选取温州医科大学附属第一医院2013年5月—2015年5月期间收治的乳腺癌患者83例,治疗前均行灰阶超声与彩色多普勒超声检查,分析患者超声检查结果、临床征象与术后随访2年期间患者预后的关系,从而分析术前灰阶超声与彩色多普勒超声联合应用对乳腺癌患者预后的预测价值。结果乳腺癌肿块边界清晰、边界不清晰、边界恶性晕的患者2年无瘤生存率依次降低,边界恶性晕与边界不清晰患者死亡率均显著高于边界清晰患者(P0.05);肿瘤≥2 cm患者2年无瘤生存率显著低于2 cm患者;淋巴结转移患者2年无瘤生存率显著低于无转移患者(P0.05);血流分级Ⅱ级患者2年无瘤生存率明显低于0级(P0.05),Ⅲ级患者2年无瘤生存率显著低于0级和Ⅰ级(P0.05)。结论乳腺癌患者术前联合应用灰阶超声与彩色多普勒超声检查可确定肿瘤边界、大小及淋巴转移等征象,其与患者无瘤生存率、死亡率等预后指标密切相关,可作为预测乳腺癌患者预后的重要方法。     

金蒲抑瘤片在鼻咽癌的临床应用研究

为探讨鼻咽癌患者放疗期间合并应用金蒲抑瘤片治疗对细胞免疫功能及血中微量元素硒、锌、铜的影响，经病理证实鼻咽癌患者58例，随机分为放疗服药组30例和单纯放疗组28例。两组放疗前后抽静脉血测定T细胞亚群（CD3＋，CD4＋，CD8＋，CD4＋／CD8＋），血中微量元素硒，锌，铜并与30例健康者（正常对照组）进行比较。结果表明，鼻咽癌患者血中微量元素硒，锌，铜及CD3＋，CD4＋，CD4＋／CD8＋显著低于健康人，放疗期间合并应用金蒲抑瘤片治疗后血中微量元素硒，锌，铜及CD3＋，CD4＋，CD4＋／CD8＋较服药前显著升高。提示鼻咽癌患者细胞免疫功能低下，血中微量元素硒，锌，铜显著低于健康人。金蒲抑瘤片能提高鼻咽癌患者因中微量元素硒，锌，铜含量，使低下的细胞免疫功能迅速恢复。     

Zur reaktionvon cyclotri- und cyclotri- und cyclotetrasilazanen mit silylfluoriden

Fluorosilyl substituted cyclosilazanes are formed by treating lithium salts of hexamethylcyclotri- and octa-methylcyclotetrasilazanes with silicon tetrafluoride and organo-substituted silicon fluorides. Disubstituted compounds are obtained by the reaction of dilithium hexamethylcyclotrisilazane with silicon fluorides or by the reaction of lithium hexamethylcyclotrisilazane with silicon fluorides at higher temperature. Cyclosilazanes with bulky ligands react with butyllithium with elimination of butane as a first step and then react further with a silicon fluoride compound, with LiF-elimination, to give a mixed substituted cyclosilazane. Ring coupling through a silicon bridge is achieved by the reaction of a fluorosilyl-substituted cyclotrisilazane with lithium hexamethylcyclotrisilazane. The mass,¹H and¹⁹F NMR spectra of the compounds are reported.     

A coupled reagent of o-phthalaldehyde and sulfanilic acid for protein detection based on the measurements of light scattering signals with a common spectrofluorometer

A rapid and sensitive method for the determination of proteins is proposed with a coupled reagent of o-phthalaldehyde and sulfanilic acid by measuring the light scattering (LS) signals with a common spectrofluorometer. Mechanism investigations showed that o-phthalaldehyde couples at first with sulfanilic acid with fast speed and forms a new synthesized Schiff base dye, which then interacts with protein rapidly on acidic condition, resulting in greatly enhanced LS signals with the maximum peak located at 344 nm. Based on the linear relationship between enhanced LS intensities and concentrations of proteins, a novel assay of HSA and BSA is established in the linear range of 0.1-25.0 microg ml(-1) with the limits of detection (3sigma) being 13 ng ml(-1) depending on the concentration of the reagent. Results for sample detections of our method were consistent with the documented spectrophotometric method with CBB G250 assay.     

Structural studies of the Maillard reaction products of a protein using ion trap mass spectrometry

The early stage products of the Maillard reaction of egg white lysozyme with D-glucose were studied. Incubation with D-glucose at 50 degrees C for 20 days caused reaction on the Lys and Arg residues of lysozyme as follows: all of the six Lys residues and 10 of the 11 Arg residues in lysozyme reacted with D-glucose; Arg 61 did not react with D-glucose. The Lys residues reacted with D-glucose with 1 mol of dehydration per mole of residue, and the Arg residues reacted with 2 mol of dehydration per mole of residue. The major constituent of the Amadori product with the epsilon-amino group of the Lys residue and the D-glucose was found to be the beta-pyranose form. The structure of the early stage product of the Maillard reaction of a protein with a sugar is the same as that of an amino acid with a sugar.     

Comparison of electrothermal atomization diode laser Zeeman- and wavelength-modulated atomic absorption and coherent forward scattering spectrometry

Atomic absorption and coherent forward scattering spectrometry by using a near-infrared diode laser with and without Zeeman and wavelength modulation were carried out with graphite furnace electrothermal atomization. Analytical curves and limits of detection were compared. The magnetic field was modulated with 50 Hz, and the wavelength of the diode laser with 10 kHz. Coherent forward scattering was measured with crossed and slightly uncrossed polarizers. The results show that the detection limits of atomic absorption spectrometry are roughly the same as those of coherent forward scattering spectrometry with crossed polarizers. According to the theory with bright flicker noise limited laser sources the detection limits and linear ranges obtained with coherent forward scattering spectrometry with slightly uncrossed polarizers are significantly better than those obtained with crossed polarizers and with atomic absorption spectrometry. This is due to the fact that employing approaches of polarization spectroscopy reduce laser intensity fluctuations to their signal carried fractions.     

N-去甲万古霉素的亲和吸附

通过交联聚丙烯酸甲酯与乙醇胺反应,形成聚(N-羟乙基丙烯酰胺)树脂,在酸催化作用下与环氧氯丙烷反应,形成含有α-羟基氯乙基的树脂.含α-羟基氯乙基的树脂与D-丙氨酸、L-丙氨酸或甘氨酸反应,分别得到含有这3种氨基酸的吸附剂.这3种吸附剂吸附N-去甲万古霉素的结果表明,含D-丙氨酸的吸附剂的吸附量最大,含甘氨酸的吸附剂的吸附量次之,而含L-丙氨酸的吸附剂不吸附N-去万古霉素.说明前两种吸附剂对N-去甲万古霉素存在亲和吸附作用.含D-丙氨酸吸附剂的最佳吸附pH值为5.8,当吸附液中的盐(NaCl)浓度增加时,吸附量降低.用0.4mol/LNa₂CO₃/CH₃CN(摩尔比7∶3,pH=9.5)作为洗脱剂可完全脱附被吸附的N-去甲万古霉素.     

Evidences of macromolecular chains confinement of ethylene–propylene copolymer in organophilic montmorillonite nanocomposites

A random ethylene–propylene copolymer (EPM) functionalized with grafted diethylsuccinate groups was melt blended with increasing amount (to 20 wt%) of organophilic montmorillonite (OMMT) to prepare nanocomposites with different morphologies as evidenced by XRD and TEM analysis. All the nanocomposites were treated with boiling toluene that did not extract a significant amount of EPM. The increase of not-extracted EPM with the increasing quantity of OMMT suggested strong interactions of the polymer chains with the inorganic substrate. The DSC measurements of nanocomposites and the corresponding insoluble residues revealed a higher T_g values with larger amount of inorganic particles. The dielectric relaxation analysis confirmed the evidence of strong interactions among montmorillonite and the polar diethylsuccinate groups for the macromolecules trapped due to the presence of the inorganic layers. The results were discussed with reference to their relevance as an evidence of nanoconfinement at polymer clay interface and correlated with the clay basal distance variation due to the intercalation process.     

Influence of substituents on selectivity and efficiency of chiral separations of anions containing single nido-7,8-dicarbaundecaborane cluster with alpha-cyclodextrin

In background electrolyte (BGE) with the optimal methanol concentration of 30% (v/v), the ion with -NCS group bonded to a cluster boron atom exhibits the strongest interaction with alpha-cyclodextrin and the highest separation selectivity. Interaction of ions with alkyl or thioalkyl group weakens with the increasing substituent size. The ion with phenyl group exhibits the weakest interaction. Bonding of a group to boron atom weakens the ion interaction with alpha-cyclodextrin. Second substituent further weakens the interaction with alpha-cyclodextrin. Separation efficiency is lower at the presence of alpha-cyclodextrin than at its absence. This separation efficiency loss, amounts up to 90%.     

四环素-铜(Ⅱ)配合物与DNA相互作用的吸收光谱研究

用紫外光谱方法研究了四环素(TC) Cu(II)配合物与DNA的相互作用.吸收光谱研究表明,DNA能与四环素(TC)及Cu(II)形成的配合物发生反应,配合物与DNA的作用方式随着配合物类型及DNA浓度的不同而不尽相同:当四环素与铜形成1∶1型配合物时,较低浓度的DNA能与配合物以嵌插方式相互作用,而较高浓度的DNA与该配合物除了发生嵌插作用外,还存在另外的作用方式;当四环素与铜形成1∶2型配合物时,DNA与该配合物则主要以嵌插方式相互作用,并且这两种配合物与DNA的嵌插作用均是通过四环素配体插入的.     

卤代苯与水分子间作用的从头算

污染是科学家关注的热点问题,化学污染物是造成水污染的重要因素［１］．在水环境中,卤代苯是一类优先污染物（ｐｒｉｏｒｉｔｙｐｏｌｕｔａｎｔｓ）［２］．这类污染物毒性大,在环境中的半衰期长,美国环保局（ＥＰＡ）已经把它们列入优先污染物之列．Ｖｅｒｓｃｈｎ...     

Synthesis and copolymerization of new phosphorus‐containing acrylates

Two phosphorus‐containing acrylate monomers were synthesized from the reaction of ethyl α‐chloromethyl acrylate and t‐butyl α‐bromomethyl acrylate with triethyl phosphite. The selective hydrolysis of the ethyl ester monomer with trimethylsilyl bromide (TMSBr) gave a phosphonic acid monomer. The attempted bulk polymerizations of the monomers at 57–60 °C with 2,2′‐azobisisobutyronitrile (AIBN) were unsuccessful; however, the monomers were copolymerized with methyl methacrylate (MMA) in bulk at 60 °C with AIBN. The resulting copolymers produced chars on burning, showing potential as flame‐retardant materials. Additionally, α‐(chloromethyl)acryloyl chloride (CMAC) was reacted with diethyl (hydroxymethyl)phosphonate to obtain a new monomer with identical ester and ether moieties. This monomer was hydrolyzed with TMSBr, homopolymerized, and copolymerized with MMA. The thermal stabilities of the copolymers increased with increasing amounts of the phosphonate monomer in the copolymers. A new route to highly reactive phosphorus‐containing acrylate monomers was developed. A new derivative of CMAC with mixed ester and ether groups was synthesized by substitution, first with diethyl (hydroxymethyl)phosphonate and then with sodium acetate. This monomer showed the highest reactivity and gave a crosslinked polymer. The incorporation of an ester group increased the rate of polymerization. The relative reactivities of the synthesized monomers in photopolymerizations were determined and compared with those of the other phosphorous‐containing acrylate monomers. Changing the monomer structure allowed control of the polymerization reactivity so that new phosphorus‐containing polymers with desirable properties could be obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2207–2217, 2003     

Reaction features of 2,3,4-trichloro-1-butene with phosphoric and nitrogen nucleophiles

Reaction of 2,3,4-trichloro-1-butene with phosphoric and nitrogen nucleophiles was carried out. In the reaction with allyldiphenylphosphine 1,4-bis-(allyldiphenylphosphoniochlorido)-1,3-butadiene was obtained, with tributylphosphine, allyldimethylamine and trimethylamine respective 1,4-bis-onium salts with 2-chloro-2-butenylene group. Reaction with trimethylamine proceeded with formation of monoammonium salt with 3,4-dichloro-2-butenyl group. It is noteworthy that 1,4-splitting of 1,4-bis-(trimethylammoniochlorido)-2-butene at the action of sodium methoxide occurs with involvement of the less labile hydrogen atom.     

Steric effects in the aerobic oxidation of pi-allylnickel(II) complexes with N-heterocyclic carbenes

Pi-allylchloro(NHC)nickel(II) complexes were synthesized and their reactions with O2 were studied. Ligand steric effects were found to determine the difference between rapid oxidation of the allyl group to produce bis-mu-hydroxonickel complexes and no observable reaction. The ability of the metal-NHC bond to rotate correlates with the ability of the complex to react with O2. In the limiting cases, conformationally restricted complexes are stable to O2 and complexes with rapid Ni-NHC bond rotation react rapidly with O2. Complexes with intermediate conformational flexibility were found to exhibit lesser reactivity with O2. On the basis of the observed inertness of complexes with saddle-shaped ligands to O2, we propose the adoption of a nonplanar geometry upon reaction with O2 to be required. The issue of conformational flexibility versus rigidity is expected to directly impact the catalytic behavior of metal-NHC complexes.     

A hierarchically zeolite Y for the N-heterocyclic compounds synthesis

High activity and selectivity of the hierarchical H-Ymmm zeolite in the synthesis of practically important pyridines (by interaction of C₂–C₄ alcohols with formaldehyde and ammonia, cyclocondensation of acetaldehyde and propanal with ammonia), dialkyl quinolines (by reaction of aniline with aldehydes) and alkyl dihydroquinolines (by reaction of aniline with ketones- acetone, acetophenone) were revealed in the research.The advantages of the micro-meso-macroporous H-Ymmm zeolite over the microporous H-Y zeolite in the synthesis of pyridines and quinolines were demonstrated. In the products formed by the reaction of ethanol with formaldehyde and ammonia, picolines (up to 63%) and lutidine are predominant in H-Ymmm, Pb-H-Ymmm and Fe-H-Ymmm zeolites. The interaction of n-propanol (n-butanol) with formaldehyde and ammonia in the presence of H-Ymmm zeolite with high selectivity produced 3,5-lutidine (up to 90%) or 3,5-diethylpyridine (85%). H-Ymmm zeolite makes it possible to prepare 2-methyl-5-ethylpyridine with 87% selectivity (reaction of acetaldehyde with ammonia) and 2-ethyl-3,5-dimethylpyridine with 58% selectivity (reaction of propanal with ammonia).The synthesis of dialkylquinolines and dialkyltetrahydroquinolines with a total selectivity of 65–73% by the interaction of aniline with C₃–C₅ aldehydes has been carried out. The dihydroquinoline derivatives with the selectivity of up to 70% have been synthesized by the reaction of aniline with ketones (acetone, acetophenone).     

Electrochemical Characterization of the Interaction of Multiwalled Carbon Nanotubes with Doxorubicin

It has been suggested that multiwalled carbon nanotubes (MWCNTs) interacting with pharmaceutics may be introduced into the body as nanocarriers. To deliver the anticancer drugs, covalent or noncovalent functionalization of MWCNTs is required. In this study, the influence of oxidation on MWCNTs in the interaction with chemotherapeutic drug, doxorubicin, was characterized. The binding of doxorubicin with MWCNTs decreased rapidly with the increasing oxidation period with sulfuric acid. However, with nitric acid, the interaction increased initially and slowly decreased with time. The best results were obtained for sulfuric and nitric acid following 1 and 3?h of oxidation, respectively. The results show that sulfuric acid provided more favorable interaction for MWCNTs with doxorubicin than nitric acid.     

Determination of paraquat in marijuana by reversed-phase paired-ion high performance liquid chromatography.

A sensitive and selective method is described for the quantitative determination of paraquat in marijuana. Paraquat is extracted from finely ground plant material with hydrochloric acid with sonification, and the resulting acidic solution is extracted with chloroform:isopropanol (9:1) and evaporated to dryness. The residue is reconstituted with aqueous phosphate buffer pH 7.0; the solution is passed through a C-18 SEP-PAK TM and is analyzed with high performance liquid chromatography, using a reversed-phase column and an "ion pairing" reagent in the mobile phase. The recovery of paraquat in laboratory-spiked material varied from 90-97%. Results obtained with confiscated, field-sprayed marijuana by the procedure described were in excellent agreement with those obtained with a well-established ultraviolet procedure. The calculated limit of detection with this method is 2 ng of paraquat.     

Modification of supercapacitor electrodes with polymer metallocomplexes: Methods and results

A procedure for electrochemical modification of carbon materials with high specific surface was developed. The materials were modified with polymeric nickel complexes with Schiff bases. The prototype of a hybrid double-layer Faraday supercapacitor with a positive carbon electrode modified with a polymeric complex was studied. Modification of this type doubled the energy stored by the hybrid capacitor compared with the similar double-layer capacitor.