季铵盐型魔芋葡甘聚糖衍生物的合成、表征及生物学活性

以魔芋葡甘聚糖为载体,以硝酸铈铵作引发剂,用甲基丙烯酰氧乙基-十四烷基-二甲基溴化铵为活性单体进行接枝共聚反应制备季铵盐型魔芋葡甘聚糖衍生物。用核磁共振,红外光谱,DSC和激光粒度Zeta电位仪对接枝产物进行了表征和测定,用悬菌定量实验研究了其抗菌性能。结果表明：(1)甲基丙烯酰氧乙基-十四烷基-二甲基溴化铵通过其双键接枝到魔芋葡甘聚糖表面,接枝率随着季铵盐单体的用量增加而提高;(2)魔芋葡甘聚糖的零电位在pH 4.5,魔芋葡甘聚糖季铵盐衍生物的零电位在pH 9.9,季铵基的引入使其零电位发生了较大的位移;(3)所制备的魔芋葡甘聚糖季铵盐衍生物对大肠杆菌、金黄色葡萄球菌以及白色念珠菌在振荡作用15 min后,平均杀菌率分别为99.99％,99.99％和98.13％。     

Competition between counterions and active protein sites to bind bisquaternary ammonium groups. A combined mass spectrometry and quantum chemistry model study

A model study of the interaction between biologically active bisquaternary ammonium salts and their molecular targets in living systems is urgently needed to elucidate the molecular mechanisms involved in the interactions between these compounds. To address this need a combined experimental-computational study of the interaction of two tetramethylammonium cations (modeling two quaternary groups) with the chlorine anion and with the deprotonated 2,5-dihydroxybenzoic acid (modeling a carboxylic group and an aromatic ring of side radicals of proteins) has been performed. Fast atom bombardment mass spectrometry method and DFT/B3LYP/6-31++G^** and MP2/6-31++G^** calculations have been employed in the study. Stable noncovalent complexes with different ratios of the tetramethylammonium cations and chlorine anions or deprotonated 2,5-dihydroxybenzoic acid anions were registered in the mass spectra of tetramethylammonium chloride and 2,5-dihydroxybenzoic acid mixture. This finding shows that the organic and inorganic anions compete to bind tetramethylammonium in the studied system. The theoretically determined stabilities of the noncovalent complexes were compared with the relative stabilities evaluated from the mass spectrometric measurements. The results of the study allow us to elucidate the competing interactions that exist between quaternary groups with inorganic counterions or with active groups of molecular protein targets.     

A surface-enhanced Raman scattering study of CTAB adsorption on copper

Surface-enhanced Raman spectroscopy (SERS) has been used to study, in situ, the adsorption of cetyltrimethylammonium bromide (CTAB) on copper. The data obtained allow the determination of CTAB's adsorption rate from aqueous solution and are consistent with physisorption or weak chemisorption via the quaternary ammonium group. The use of “surface selection rules” to derive orientation information is examined.     

Radical graft polymerization initiated by azo groups introduced onto the surface of carbon whisker

The radical graft polymerization of vinyl monomers onto carbon whisker, i.e. vapor grown carbon fiber, initiated by azo groups introduced onto the surface has been investigated. The introduction of azo groups onto the surface is achieved by (1) the reaction of 4,4'-azobis(4-cyanopentanoic acid) with isocyanate groups on the surface, which are introduced by the treatment of surface carboxyl and phenolic hydroxyl groups with tolylene-2,4-diisocyanate and (2) the reaction of 2,2'-azobis(2-cyano-n-propanol) with acyl chloride groups on the surface, which are introduced by the treatment of surface phenolic hydroxyl groups with terephthaloyl dichloride. The carbon whiskers having azo groups prepared from the above two methods are abbreviated as CW-Azo 1 and 2, respectively. The azo group content of CW-Azo 1 and 2 is determined to be 0.04 and 0.07 mmol/g, respectively. It is found that the radical polymerization of methyl methacrylate and styrene is initiated by the surface azo groups to give the corresponding polymer-grafted carbon whisker. The polymer-grafted carbon whisker gives a stable colloidal dispersion in good solvents for grafted polymer.     

季铵盐型纳米气相二氧化硅衍生物的合成、表征及生物学活性

以纳米气相SiO₂为载体,以γ- 氯丙基三甲氧基硅烷作偶联剂,用N,N-二甲基十四烷基叔胺进行了季铵化反应制备季铵盐型纳米气相二氧化硅衍生物。用红外光谱,DSC和激光粒度Zeta电位仪对纳米气相二氧化硅季铵盐衍生物进行了表征和测定,用悬菌定量实验(Suspension quantitative test)研究了其抗菌性能。结果表明：(1) γ- 氯丙基三甲氧基硅烷通过与纳米气相二氧化硅表面羟基的反应键合到二氧化硅表面,随着γ-氯丙基三甲氧基硅烷的用量增加,纳米气相二氧化硅表面羟基被取代程度也增加;(2)纳米气相二氧化硅的零电位在pH 4.8,纳米气相二氧化硅季铵盐衍生物的零电位在pH 10.5,季铵盐的引入使其零电位发生了较大的位移;(3)所制备的纳米气相二氧化硅季铵盐衍生物对大肠杆菌、金黄色葡萄球菌以及白色念珠菌在振荡作用15 min后,平均抑菌率分别为99.99%,99.99%和94.12%。     

Study of combined electroreflectance and double layer effects at lead electrodes

Reflectance changes at lead electrodes have been measured as a function of surface charge at 45° and 70° angles of incidence using solutions of sodium fluoride and quaternary ammonium salts. These solutions were chosen so as to provide quite different composition for the inner layer at the metal/solution interface, and hence different optical contributions there from. Linear reflectance-surface charge relation has been observed for NaF solutions only at a number of wavelengths. The optical effects from the inner layer has been recognized but could not be separated out from the main er effect by comparative measurements at two angles of incidence. This has been rationalized on the basis of similar variation of the er effect and the optical effect from the double-layer as a function of angle of incidence of light.     

Radical grafting from carbon fiber surface: graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface

This paper describes the radical graft polymerizations of vinyl monomers from carbon fiber surface initiated by azo groups introduced onto the fiber surface. The carbon fiber used in this experiment was the polyacrylonitrile type. The introduction of azo groups onto the carbon fiber surface was achieved by the reaction of 4,4'-azobis (4-cyanopentanoic acid) with isocyanate groups which were previously attached onto the surface by the treatment of the fiber with tolylene 2,4-diisocyanate. The amount of surface azo groups introduced onto nitric acid-treated carbon fiber was determined to be 0.60 x 10^-5 mol 9^-1 by nitrogen analysis. The radical graft polymerization of methyl methacrylate (MMA) was tried. Though the thermal polymerization of MMA proceeded slightly in the absence or in the presence of untreated carbon fiber, the rate of the polymerization was considerably low. In contrast, the graft polymerization of MMA was initiated in the presence of the carbon fiber having surface azo groups, and part of resultant poly(MMA) grafted onto the surface. The percentage of grafting increased with an increase in polymerization time and reached 42.8% after 24 h. The graft polymerizations of other monomers, such as styrene, vinyl acetate, and acrylic acid, were also initiated by the surface azo groups attached onto the carbon fiber, and the corresponding polymer effectively grafted onto the surface.     

Surfactant-assisted organic reactions in water. Effect of ultrasound on condensation reactions between active methylene compounds and arylaldehydes

A series of quaternary ammonium salts has been tested as phase transfer agents to promote condensation reactions in an aqueous solution of sodium hydroxide in the absence of any organic solvent. Methyltrioctylammonium chloride (Aliquat 336) emerges as the most efficient catalyst. Sonication of the reaction media has a poor but positive kinetic effect.     

Superhydrophobic cotton fabric coating based on a complex layer of silica nanoparticles and perfluorooctylated quaternary ammonium silane coupling agent

A superhydrophobic complex coating for cotton fabrics based on silica nanoparticles and perfluorooctylated quaternary ammonium silane coupling agent (PFSC) was reported in this article. The complex thin film was prepared through a sol-gel process using cotton fabrics as a substrate. Silica nanoparticles in the coating made the textile surface much rougher, and perfluorooctylated quaternary ammonium silane coupling agent on the top layer of the surface lowered the surface free energy. Textiles coated with this coating showed excellent water repellent property, and water contact angle (CA) increased from 133° on cotton fabrics treated with pure PFSC without silica sol pretreatment up to 145°. The oil repellency was also improved and the contact angle of CH₂I₂ droplet on the fabric surface reached to 131°. In contrast, the contact angle of CH₂I₂ on the fabric surface treated with pure PFSC was only 125°.     

Photochemical transformations of quaternary ammonium tetrachlorocuprates on an aerosil surface

EPR measurements show that the products of photolysis of quaternary ammonium tetrachlorocuprates with 405-nm light in a solvent frozen at 77 K and on an aerosil surface are identical. As compared to matrix isolation at low temperature, immobilization on an aerosil surface makes it possible to extend the temperature range of existence of copper(II) organic products of photolysis by at least 50 K.     

Positioning of cationic silver nanoparticle by using AFM lithography and electrostatic interaction

One-dimensional metal lines of silver nanoparticles with a nano-sized width were generated onto silicon surface by using a nano-level lithography technique, field induced oxidation (FIO) by AFM, on self-assembled monolayer-modified Si wafers. This FIO technique provided SiO₂ lines a width of less than 100 nm. Short-time immersion of partially anodized silicon surface which is covered by a cationic silanol surfactant ((CH₃O)₃SiCH₂CH₂CH₂N(CH₃)₃⁺Cl⁻)-monolayer into quaternary ammonium (HSCH₂CH₂N(CH₃)₃⁺Br⁻)-covered silver nanoparticles readily and reproducibly gave nano-metal lines of silver onto silicon wafers. Hydrophilicity of the whole wafer surface was indispensable for homogeneously wetting the anodized SiO₂ area with a nanodimensional width.     

Flocculation Properties of Some Cationic Polysaccharides

Flocculation of a clay suspension model using some cationic polysaccharides has been studied by turbidity measurements. The investigated polyelectrolytes contain quaternary ammonium salt groups, N-ethyl-N, N-dimethyl-2-hydroxypropylene ammonium chloride, attached to a dextran backbone. The flocculation efficiency was studied as a function of the polycation charge density and some flocculation parameters (polycation dose, settling time, concentration of both clay suspension and parent solution of polymer). All investigated cationic polysaccharides showed high flocculating efficiency at optimum flocculant doses, which correlated well with the charge density of the polycations: the higher charge density, the lower the amount of dextran derivative was required for reaching the maximum clarity degree (of about 100%). This finding is consistent with the neutralization mechanism for a flocculation process. The residual turbidity values also varied with the settling time and the concentrations of clay suspension and parent solution of polymer. Possible reasons for these dependences are discussed.     

A Novel Water-soluble Ratiometric Fluorescent Probe Based on FRET for Sensing Lysosomal pH

A new ratiometric fluorescent probe based on Förster resonance energy transfer (FRET) for sensing lysosomal pH has been developed. The probe (RMPM) was composed of imidazo[1,5-α]pyridine quaternary ammonium salt fluorophore as the FRET donor and the rhodamine moiety as the FRET acceptor. It’s the first time to report that imidazo[1,5-α]pyridine quaternary ammonium salt acts as the FRET donor. The ratio of fluorescence intensity of the probe at two wavelengths (I₄₂₄/I₅₈₁) changed significantly and responded linearly toward minor pH changes in the range of 5.4–6.6. It should be noted that it’s rare to report that a ratiometric pH probe could detect so weak acidic pH with pKa = 6.31. In addition, probe RMPM exhibited excellent water-solubility, fast-response, all-right selectivity and brilliant reversibility. Moreover, RMPM has been successfully applied to sensing lysosomal pH in HeLa cells and has low cytotoxicity.     

Corrosion inhibition of iron in acidic solutions by alkyl quaternary ammonium halides: Correlation between inhibition efficiency and molecular structure

The corrosion inhibition of iron in 0.5 M H₂SO₄ solutions by alkyl quaternary ammonium halides (AQAH) inhibitors has been studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements. The correlation between inhibition efficiency and molecular structure of the AQAH compounds is investigated. The results show that besides the concentration, the structure of alkyl groups and the type of halide ions of these AQAH inhibitors greatly influence the inhibition efficiency. Data obtained from EIS measurements are analyzed to model the corrosion inhibition process through appropriate equivalent circuit models.     

Surface modification of calcium carbonate: radical graft polymerization of vinyl monomers onto calcium carbonate surface initiated by azo groups introduced onto the surface

—The preparation of calcium carbonate modified by 12-hydroxystearate groups and the grafting of polymers onto the surface by the polymerization of vinyl monomers initiated by azo groups introduced onto the surface were investigated. The preparation of calcium carbonate modified by 12-hydroxystearate was achieved by the reaction of calcium chloride with sodium carbonate containing a small amount of sodium 12-hydroxystearate. The introduction of azo groups onto calcium carbonate was successfully achieved by the direct condensation of the carboxyl group of 4,4'-azobis(4-cyanopentanoic acid) with 12-hydroxystearate groups on the modified calcium carbonate using N,N'-dicyclohexylcarbodiimide as a condensing agent. It was found that the radical polymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole (NVC), was initiated by azo groups introduced onto the surface, and the corresponding polymers were grafted onto the surface based on the propagation of polymer from the surface: the percentage of grafting of polyMMA, polystyrene, and polyNVC reached 5.7, 9.5 and 3.5%, respectively, at 70°C. The percentage of grafting was found to decrease with decreasing monomer concentration. The wettability of calcium carbonate surface was found to turn from hydrophilic to hydrophobic by the grafting of polymers.     

Density, ultrasonic velocity, surface tension, excess volume and viscosity of quaternary fluid solutions

Density, ultrasonic velocity, surface tension, excess volume and viscosity of quaternary non-electrolyte solution n-pentane+tolune+n-heptane+cyclohexane has been experimentally determined at 25 °C over a wide range of composition. Assuming a quaternary fluid solution to be made of six binaries, a statistical approach of Prigogine–Flory–Patterson (PFP) theory has been extended to develop the expressions for dynamic viscosity, surface tension excess volume and ultrasonic velocity of quaternary fluid system. A reasonable agreement has been achieved between theory and experiment. An attempt has also bee made to explain the nature of molecular interactions involved in the light of excess thermodynamic functions whose sign and magnitude depend upon the chain length and size of the component fluids and also studied the role of order breakers (toluene and cyclohexane) on these properties.     

Combined effect of ultrasound and nanoclay on adsorption of phenol

Sorption of phenol onto organophilic bentonite (nanoclay) by ultrasonic irradiation was investigated. Tetrabutyl ammonium chloride (TBAC), N-acetyl-N,N,N trimethyl ammonium bromide (CTAB) and hexadecyl trimethyl ammonium chloride (HDTMA) were used as intercalating agents. Nanoclay was synthesized using sonication technique. TBAC modified nanoclay shows amorphous exfoliated nature, while CTAB and HDTMA modified nanoclay shows intercalating crystalline nature, which was revealed by XRD gram. Further FTIR reveals the presence of NH(2) and (CH(2))(n) groups onto clay platelet. Due to sonication, adsorption equilibrium was achieved within short period of time (10 min). It was found that intraparticle diffusion resistance has overcome due to sonication. The experimental data obtained obeys both Freundlich isotherm model and Langmuir adsorption isotherm model. HDTMA modified nanoclay shows higher parameter values.     

Polypropylene modified with 2-hydroxyethyl acrylate-g-2-methacryloyloxyethyl phosphorycholine and its hemocompatibility

Polypropylene (PP) was modified with 2-hydroxyethyl acrylate (HEA) by solution radical grafting to introduce active hydroxyl groups on polypropylene backbone (PP-g-HEA). Then the biomimic monomer, 2-methacryloyloxyethyl phosphorycholine (MPC), was grafted onto the surface of PP-g-HEA film (PP-g-HEA-g-MPC) by redox graft polymerizations with ceric(IV) ammonium nitrate as an initiator. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) showed that the HEA and MPC were introduced onto PP molecular chains and the copolymer, PP-g-HEA-g-MPC were formed. The water contact angle measurements demonstrated that the final modified PP film exhibited a better hydrophilic surface compared to the neat PP film. The platelets adhesion on the neat PP, PP-g-HEA and PP-g-HEA-g-MPC film was examined by scanning electron microscopy (SEM). It was found that a large number of platelets were adhered and activated on the surface of neat PP and PP-g-HEA films, while the number of platelets on PP-g-HEA-g-MPC surface was decreased remarkably. The result revealed that the introduction of poly(MPC) onto the PP surface improved the hemocompatibility of PP substantially.     

不同链长尾式卟啉-三乙胺和吡啶季铵盐的1H NMR研究

为了改善卟啉显色剂对金属离子选择性较差的缺点,新合成了不同链长尾式卟啉-三乙胺季铵盐和吡啶季铵盐六种化合物,对新化合物进行元素分析,确定其组成.用NMR和IR研究其化合物的结构,并讨论六种化合物核磁共振谱关系特征及其规律.     

新型尾式卟啉-三乙胺和吡啶季铵盐的红外光谱研究

本文对新合成的三个尾式卟啉季铵盐的红外光谱吸收带进行了归属和总结。讨论了红外吸收频率随取代基不同而发生变化的原因,以及不同链长时的诱导效应对＝Ｃ－Ｏ－Ｃ键的影响。