An amperometric biosensor based on covalent immobilization of ascorbate oxidase on biocompatiable and low-toxic poly(thiophene-3-acetic acid) matrix

The biocompatiable and low-toxic poly（thiophene-3-acetic acid）（PTAA） matrix was successfully electrosynthesized in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate（BmimPF₆） in comparison with the electrosynthesis of PTAA matrix in acetonitrile（ACN）.Ascorbate oxidase（AO） was used as a model for the development and application of biosensor.Vitamin C（VC） biosensors were facilely fabricated by the covalent immobilization of AO molecules on PTAA matrices electrosynthesized in ACN containing tetrabutylammonium tetrafluoroborate and BmimPF₆, respectively.Electrochemical impedance spectroscopy,scanning electron microscopy and FTIR spectroscopy indicated that AO molecules were covalently immobilized on PTAA matrices.Parameters of the as-obtained biosensors such as working potential,pH and temperature have been optimized.The amperometric biosensor based on PTAA matrix electrosynthesized in BmimPF₆ exhibited wider linear range,lower detection limit,higher sensitivity and bioaffinity,and better operational and storage stability than that electrosynthesized in ACN under optimal conditions.The as-obtained biosensor based on PTAA matrix electrosynthesized in BmimPF₆ was employed for the detection of VC content in commercial juices,and the result was close to the data given by manufacturers.Excellent results indicate that the PTAA matrix electrosynthesized in ionic liquid is a promising platform for the covalent immobilization of biologically-active species and the development of biosensors.     

Self-doping effect in poly(o-methoxyaniline)/poly(3-thiopheneacetic acid) layer-by-layer films

Nanostructured films from two conducting polymers, poly(o-methoxyaniline) (POMA) and poly(3-thiopheneacetic acid) (PTAA), were fabricated with the layer-by-layer (LBL) technique. The electrochemical response of the LBL films differs from that of a POMA cast film, even in a potential range where PTAA is inactive. This is attributed to differences in the diffusion-controlled charge and mass transport, where distinct ionic species participate in the LBL films, as demonstrated by quartz crystal microbalance measurements. The results show that the transport properties of conducting polymers can be changed by alternation with layers of appropriate materials in LBL films.     

Poly(thiophene-3-acetic acid)-palladium nanoparticle composite modified electrodes for supersensitive determination of hydrazine

 A promising electrochemical sensor was fabricated by electrodeposition of Pd nanoparticles (PdNPs) on poly(thiophene-3-acetic acid) (PTAA)-modified glassy carbon electrode (GCE), forming a PdNPs/PTAA composites-modified GCE (PdNPs/PTAA/GCE). Scanning electron microscope (SEM) and electrochemical techniques were used for the characterization of these composites. It was found that the PdNPs/PTAA layer was very uniform. Electrochemical experiments showed that this proposed PdNPs/PTAA composites-modified electrode exhibited excellent electrocatalytic activity towards the oxidation of hydrazine. Under the optimum conditions, the proposed sensor can be applied to the quantification of hydrazine with a wide linear range from 8.0?10^-9 mol/L to 1.0?10^-5 mol/L with a low detection limit of 2.67?10^-9 mol/L. The experiment results also showed that the sensor exhibited good reproducibility and long-term stability, as well as high selectivity with no interference from other potential competing species.     

Poly(terephthalic acid anhydride) as a latent monomer in polybenzoxazole synthesis

High molecular weight poly(p-phenylenebenzobisoxazole) (PBO) was prepared from poly(terephthalic acid anhydride) (PTAA) and 1,3-diamino-4,6-dihydroxybenzene dihydrogenchloride in polyphosphoric acid (PPA). PTAA may react directly with the o-aminophenol groups to form benzoxazoles or react with PPA to generate terephthalic acid (TA) of very small particle size, which dissolves readily in PPA. PTAA provides the advantages of bypassing the requirement of small particle size TA, reducing the amount of water liberated by half, and possibly providing faster kinetics in PBO synthesis. © 1994 John Wiley & Sons, Inc.     

Outer‐Membrane Protease (OmpT) Based E. coli Sensing with Anionic Polythiophene and Unlabeled Peptide Substrate

E. coli and Salmonella are two of the most common bacterial pathogens involved in foodborne and waterborne related deaths. Hence, it is critical to develop rapid and sensitive detection strategies for near‐outbreak applications. Reported is a simple and specific assay to detect as low as 1 CFU mL^?1 of E. coli in water within 6 hours by targeting the bacteria's surface protease activity. The assay relies on polythiophene acetic acid (PTAA) as an optical reporter and a short unlabeled peptide (LL37_FRRV) previously optimized as a substrate for OmpT, an outer‐membrane protease on E. coli. LL37_FRRV interacts with PTAA to enhance its fluorescence while also inducing the formation of a helical PTAA‐LL37_FRRV construct, as confirmed by circular dichroism. However, in the presence of E. coli LL37_FRRV is cleaved and can no longer affect the conformations and optical properties of PTAA. This ability to distinguish between an intact and cleaved peptide was investigated in detail using LL37_FRRV sequence variants.     

Outer-Membrane Protease (OmpT) Based E. coli Sensing with Anionic Polythiophene and Unlabeled Peptide Substrate

E. coli and Salmonella are two of the most common bacterial pathogens involved in foodborne and waterborne related deaths. Hence, it is critical to develop rapid and sensitive detection strategies for near-outbreak applications. Reported is a simple and specific assay to detect as low as 1 CFU mL⁻¹ of E. coli in water within 6 hours by targeting the bacteria's surface protease activity. The assay relies on polythiophene acetic acid (PTAA) as an optical reporter and a short unlabeled peptide (LL37_FRRV) previously optimized as a substrate for OmpT, an outer-membrane protease on E. coli. LL37_FRRV interacts with PTAA to enhance its fluorescence while also inducing the formation of a helical PTAA-LL37_FRRV construct, as confirmed by circular dichroism. However, in the presence of E. coli LL37_FRRV is cleaved and can no longer affect the conformations and optical properties of PTAA. This ability to distinguish between an intact and cleaved peptide was investigated in detail using LL37_FRRV sequence variants.     

Self-assembly of multilayer films containing gold nanoparticles via hydrogen bonding

Polymer/Au nanoparticle multilayer ultrathin films are fabricated via hydrogen-bonding interaction by a layer-by-layer technique. The Au nanoparticles surface-modified with pyridine groups of poly(4-vinylpyridine) (PVP) are prepared in dimethyl formamide (DMF). Transmission electron microscopy (TEM) image shows that uniform nanoparticles are dispersed in the PVP chains. Poly(3-thiophene acetic acid) (PTAA) and poly(acrylic acid) (PAA) are utilized to form hydrogen bonds with PVP, respectively. Considering the pH-sensitive dissociation behavior of PTAA and PAA, we investigate the release behavior of the Au-containing multilayers at different pH values in this work. UV-vis spectroscopy and atomic force microscopy (AFM) are employed to monitor the buildup and the release of the multilayers. The results indicate that in the films assembled with gold nanoparticles, the polymers are difficult to be removed from the substrate. The interaction between the gold particles and the neighboring PVP chains is responsible for the phenomenon. Gold particles act as physical cross-link points in the multilayers. Due to the additional interaction caused by the gold nanoparticles in the films except the hydrogen-bonding interaction between PTAA (or PAA) and PVP, the stability of the Au-containing multilayer film is ensured even though the changes in pH values may result in the break of the hydrogen bonds.     

Synthesis of linear unsubstituted poly(4,4′-triphenylamine) via Suzuki-Miyaura coupling of an asymmetric AB monomer

Polytriarylamines (PTAAs) are amorphous polymers that can be reversibly oxidized to generate stable radical cations. Despite exhibiting a low charge carrier mobility, PTAAs are widely used as hole-transporting layers in perovskite solar cells due to their excellent stability under ambient conditions. The highest occupied molecular orbital (HOMO) energy levels of PTAA are generally in the range of −5.1 to −5.2 eV, and therefore slightly too high for an optimal alignment with perovskites. Most linear PTAAs carry two or three methyl substituents per repeating unit. While these prevent crosslinking of chains and thus provide reaction control, the electron-donating substituents raise the energy level of the HOMO. Unsubstituted PTAA on the other hand is usually obtained crosslinked via oxidative polymerization, while nickel-catalyzed Grignard polycondensation leads to inclusion of impurities. We report the synthesis of linear unsubstituted PTAA using Suzuki-Miyaura coupling of a novel asymmetric monomer, 4-((4-bromophenyl)(phenyl)amino)phenyl)boronic acid M1 . Based on matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) and ¹H NMR analysis, we can conclude that the hydrogen-terminated linear polymer is obtained. The determined HOMO energy level of −5.47 eV is a favorable match for many perovskite systems.     

Layer-by-layer self-assembled chitosan/poly(thiophene-3-acetic acid) and organophosphorus hydrolase multilayers

The aim of this study is to immobilize an enzyme, namely, organophosphorus hydrolase (OPH), and to detect the presence of paraoxon, which is an organophosphorus compound, using the layer-by-layer (LbL) deposition technique. To lift the OPH from the solid substrate, a pair of polyelectrolytes (positively charged chitosan (CS) and negatively charged poly(thiophene-3-acetic acid) (PTAA)) were combined. These species were made charged by altering the pH of the solutions. LbL involved alternate adsorption of the oppositely charged polyions from dilute aqueous solutions onto a hydrophilic quartz slide. This polyion cushion was held together by the electrostatic attraction between CS and PTAA. The growing process was monitored by fluorescence spectroscopy. OPH was then adsorbed onto the five-bilayer CS/PTAA system. This five-bilayer macromolecular structure compared to the solid substrate rendered stability to the enzyme by giving functional integrity in addition to the ability to react with paraoxon solutions. The ultimate goal is to use such a system to detect the presence of organophosphorus compounds with speed and sensitivity using the absorption and fluorescence detection methodologies.     

煤酸异构化制对苯二甲酸

进行了煤氧化产物煤酸（水溶酸WSA）钾在催化剂碳酸镉的存在下，异构化制对苯二甲酸(TPA)的研究。主要考察了催化剂用量、二氧化碳初压、反应温度和反应时间对TPA产率的影响。结果表明，在催化剂存在下煤酸可以转化成TPA。单独煤酸钾异构化时，较佳反应条件：温度430 ℃～450 ℃，压力4.0 MPa，催化剂CdCO3用量4%，反应时间2 h。煤酸钾与苯甲酸（BA）钾混合异构化时，较佳反应条件与单独煤酸钾时基本相同。单独煤酸钾在较佳条件下异构化时，粗TPA产率达34%左右，相当于根据其中有效成分苯多羧酸（BPCA）计算的理论产率的75%左右，选择性较好。煤酸钾加苯甲酸钾在较佳条件下异构化时,粗TPA产率可达68%，扣除假定BA自身岐化生成TPA理论产量之后，则煤酸的TPA产率高达70%，比煤酸单独异构化TPA产率(34%)高1倍。粗TPA经精制可得纯度99%以上的精TPA。     

三氟化硼乙醚/乙酸混合电解质中芴的电化学聚合

在三氟化硼V(乙醚):V(乙酸)=4:5的混合电解质体系中直接氧化芴,获得芴聚合物膜,其电导率为0.5 S cm-1,高于在纯三氟化硼乙醚中制得的聚芴的电导率0.25 S cm-1.在三氟化硼乙醚:乙酸=4:5的混合电解质体系中获得的聚芴膜具有良好的电化学性质和化学稳定性.FTIR,1H-NMR和量化计算表明反应发生在...     

Molecular Assembly by Sequential Ionic Adsorption of Nanocrystalline TiO2 and a Conjugated Polymer

Abstract

Cationic nanocrystalline TiO₂ particles have been synthesized for which the size and composition of the nanoparticles were analyzed by a transmission emission microscopy and energy dispersive x‐ray spectrometer (EDXS). Multilayered films have been fabricated by sequential adsorption of TiO₂ nanoparticles and poly(3‐thiophene acetic acid) (PTAA). Each layer of the nanoparticles and PTAA in the thin film has also been characterized by x‐ray photoelectron spectroscopy, atomic force microscopy, and UV‐visible spectroscopy. These types of multilayered nanocomposite films may find applications in the fabrication of efficient light harvesting photovoltaic cells.     

12-钼磷酸的BrÖnsted酸位和Lewis酸位

研究了加热、抽空等预处理对固态12-钼磷酸(PMA)酸位的影响。发现了PMA上除存在B-酸位外,还可生成L-酸位。研究了PMA上L-酸位的成因,水在两类酸位形成过程中的作用,L-酸位与B-酸位的相对强度,以及PMA上酸强度的分布。据此,对Miscno等认为PMA中只存在质子酸和酸强度分布均匀的观点提出了不同的看法。     

酸对脱乙酰甲壳质稀溶液粘度的影响

脱乙酰甲壳质是甲壳质衍生物中最重要,用途最为广泛的一种,属阳离子性聚电解质,可以溶于多种稀酸溶液中,本文从脱乙酰甲壳质在甲酸、乙酸和丁酸溶液中的粘度变化,研究其稀溶液性质。分別考察了脱乙酰甲壳质在8×10~(71)～3×10~(72)/1,酸浓度在5×10~(-1)～1×10~(-1)mol范围内溶液ηsp/c-c的关系。实验结果表明,作为脱乙酰甲壳质溶剂的酸,在溶液稀释时对溶液ηsp/c的影响,在不同的阶段可以是完全不同的。当溶液中可离解的酸还未能完全满足游离氨基成盐要求时,酸溶液的增加将导致溶液的ηsp/c的增加,而一旦游离氨都已成盐,过量酸的增加都会导致溶液粘度的下降。而在一般情况下,酸的酸性越强,酸的浓度越大,都会使溶液得到较低的粘度值。     

PHOTOSENSITIZED INACTTVATION OF INFECTIOUS DNA BY UROCANIC ACID, INDOLEACRYLIC ACID AND RHODIUM COMPLEXES

Naked, infectious single-stranded (ss) and double-stranded (ds) DNA from phages SI3 and G4 were irradiated with 308 nm UV radiation in the absence and presence of several photobiologically active compounds: E - and Z -urocanic acid ( E - and Z -UA), their methyl esters ( E - and Z -MU), E - and Z-indoleacrylic acid ( E - and Z -IA), cis -dichlorobis(1,10-phenanthroline)rhodium(III) chloride (cDCBPR) and tris(1,10-phenanthroline)rhodium (III) perchlorate (TPR). E -urocanic acid protects against cyclobutane pyrimidine dimer formation in ssDNA but concomitantly photosensitizes the formation of other lesions that inactivate ssDNA. Z -urocanic acid also protects ssDNA against such dimerization but without the associated sensitized damage. The methyl ester isomers behave similarly. There is no such differential activity observed for the IA isomers, both of which sensitize the inactivation of ssDNA. Photostationary state mixtures of both UA and IA efficiently sensitize the inactivation of dsDNA, and cDCBPR strongly protects ssDNA from UV damage, while TPR is a significant sensitizer. Both of these metal complexes sensitize the inactivation of dsDNA slightly. For all compounds, cyclobutane pyrimidine dimers were the predominant lethal lesions produced by sensitization of the dsDNA, but they were not the major lethal lesions created by sensitization of the ssDNA. In the case of dsDNA, both UA and IA created pyrimidine dimers with a high degree of potential for mutagenesis, as determined by an assay that monitors the frequency of mutations following the spontaneous deamination of cytosine in photodimers.     

THE PHOTOCHEMISTRY OF p-AMINOBENZOIC ACID

We have studied the photoreactions occurring when p-aminobenzoic acid (PABA), a component of some sunscreens, is irradiated in aqueous solution. These studies were carried out in the presence and absence of oxygen, using light of lambda = 254 nm as well as light of wavelengths greater than 290 nm. In deoxygenated solution between pH 7.5 and 11.0, we found two photoproducts that were identified as 4-(4'-aminophenyl)aminobenzoic acid (I) and 4-(2'-amino-5'-carboxyphenyl)aminobenzoic acid (V); we used 1H and 13C NMR, electron impact mass spectrometry and synthesis by an independent route to identify each of these compounds. Rapid discoloration of the photolyzed sample was observed when PABA was irradiated in aerated solution. Although a number of products were detected under these conditions, the three most abundant stable compounds have been isolated and identified as 4-amino-3-hydroxybenzoic acid, 4-aminophenol and 4-(4'-hydroxyphenyl)aminobenzoic acid (IV). The latter compound was shown to result from rapid photo-induced oxidation of I in the presence of oxygen. Even in the presence of trace amounts of oxygen, the yield of I was significantly reduced in favor of IV. Studies of the thermal oxidation of I, coupled with evidence gathered from studies of the photochemistry of incompletely deoxygenated PABA solutions, indicate that 4-(2,5-cyclohexadien-4-one)iminobenzoic acid (III) is an intermediate on the pathway between I and IV. Qualitatively, we found that the photochemical reactions resulting from irradiation of PABA solutions with lambda = 254 nm light and light with lambda greater than 290 nm were the same. The quantum yields for formation of I and V are highly pH dependent, both being less than 10(-4) at pH 7 and rising steadily to values greater than 10(-3) at pH 11. The detailed pH dependence suggests that the deprotonated PABA radical cation may be an important intermediate entering into the reactions forming I and IV.     

壳聚糖不饱和羧酸盐聚集行为的研究

以半干法制备了一系列壳聚糖不饱和羧酸盐--壳聚糖水杨酸盐(a1)、壳聚糖苯甲酸盐(a2)、壳聚糖肉桂酸盐(a3)壳聚糖丙烯酸盐(a4)和壳聚糖衣康酸盐(a5).用红外光谱和紫外光谱表征了该产品的结构,以凯氏定氮法测定了羧酸的结合量.结果表明壳聚糖和不饱和羧酸盐是通过壳聚糖上的氨基和羧酸中的羧基发生了成盐反应,羧酸的结合...     

SYNTHESIS OF 1, 6-DIEPI-DIHYDROARTEANNUIC ACID

R(+)-Citronellal was converted into a key intermediate, (unsaturated ketone 5)in three steps, which led to 6 having the frame of arteannuic acid through intramolecular ene reaction.Further modification of 6afforded 1, 6-epimer of dihydroarteannuic acid.The configuration of 7 was determined by X-ray diffraction analysis.     

甲苯磺酸异构体的气相色谱分析

为克服在甲苯磺酸异构体定量分析结果中重复性和准确性差的问题，从多种色谱固定液中选出合适固定液，以正十十一烷作为内标物，优化了色谱条件，对气相色谱法研究甲苯磺酸乙酯异构体中的诸多影响因素进行了比较，确定了汽化室温度对于邻、间、对甲苯磺酸乙酯异构体准确测定的影响作用。     

苯丙炔酸低聚物的合成及性能

极性-共轭双取代乙炔-苯丙炔酸在Pd(PPh3)2Cl2催化下直接通过易位催化机理聚合为低聚物.单体苯丙炔酸由两步制得,先通过液溴和肉桂酸的加成反应得到二溴代苯丙酸,然后消去两分子溴化氢得到单体.通过红外光谱(IR)、核磁共振(NMR)对单体及低聚物的结构进行了表征.凝胶渗透色谱(GPC)结果显示,聚合反应以甲苯作溶剂,75℃下效果最好,产率中等.这种共轭低聚物可以溶于四氢呋喃(THF)等极性溶剂,TGA结果表明低聚物热稳定性高.紫外可见吸收光谱(UV-Vis)显示,由于聚合后共轭主链大大增长,苯丙炔酸低聚物骨架上电子的跃迁使得低聚物的四氢呋喃溶液在波长高于310 nm光谱的区域中有吸收.荧光光谱(FS)显示,低聚物的四氢呋喃溶液在342 nm激发光下发蓝光,420 nm处有特征荧光发射峰.