一种偶氮聚电解质在不同pH值条件下的静电逐层自组装研究

研究了一种光响应偶氮聚电解质(PEAPE)在不同pH值条件下的自组装,重点讨论了pH值对静电逐层自组装以及对光响应性能的影响.研究表明,在所研究的pH范围内,pH值越低,越有利于生成吸光度高的自组装膜,对应的自组装膜厚度也越大.红外光谱分析表明,偶氮聚电解质在不同pH溶液中存在不同的电离情况.pH值越低,用于自组装的溶液中的聚合物链上的电荷数越少,链构象越卷曲.解释了不同pH值条件下自组装膜吸光度和厚度差别的原因.     

卟啉自组装膜与分子信息存储

基于卟啉化合物良好的光电性能,结合自组装膜技术,对其信息存储进行了研究.卟啉分子单体的结构、自组装膜表面卟啉的空间定位以及自组装膜基底材料的选择等对卟啉的信息存储产生着重要影响.目前,卟啉自组装膜的信息存储研究已由单点存储向超高密度多点存储发展.     

3-巯基丙酸自组装单分子膜的研究进展

自组装单层或单分子膜(Self-assembled monolayers)的研究十分活跃,尤其是硫-金体系的单层研究更是得到科学家们的青睐。3-巯基丙酸由于可以在金基底形成稳定有序的二维自组装单分子膜,从而显示出独特的结构和表面性质。该文着重从膜的制备、膜内分子的结构、单层膜的性质以及应用等方面综述金基底上3-巯基丙酸自组装单分子膜的研究进展,并对其前景进行了展望。     

建立在硫醇分子电化学替换组装基础上的纳米粒子区域化组装

利用金基底电位变化时硫醇自组装膜的吸脱附性质, 通过改变基底电位和组装溶液, 用电化学方法在金基底上实现了传统自组装技术难以实现的硫醇分子的替换组装; 通过金基底的分区化设计, 用控制电位的组装技术在基底的不同微区内制备了不同末端官能团的硫醇及其衍生物自组装膜; 并在此基础上实现了纳米粒子的区域化组装.     

钙调素修饰金电极的交流阻抗行为研究

利用交流阻抗方法, 以氧化还原对为探针，对自组装到金电极表面的钙调素 (CaM)膜的成膜过程、不同pH值的影响以及与钙离子的结合情况进行了较系统的研究.实验结果表明, 钙调素可以自组装到金电极表面并且其自组装过程较为明显地分为快、慢两个步骤；还发现钙调素膜的性能结构随体系不同的pH值发生有规律的变化，在其等电点，膜的结构最致密；而且钙调素膜与钙离子的结合也分为较明显的三个阶段.     

偶氮苯衍生物自组装膜的表征及组装动力学

报导了4-正辛基-4′-（3－巯基丙氧基）偶氮苯（简称C8AzoC3）自组装膜（Self-AssembledMonolnyersSAMs）的表征及其自组装成膜动力学，接触角滴定、原子力显微镜（AFM）及电化学的实验结果表明，C8AzoC3分子在金表面自组装形成致密有序的流水性单分子膜，并且在电极上没有明显的电化学响应．通过控制组装时间，考察了偶氮苯自组装形成单分子膜的动力学过程，从接触角和电化学数据得到组装过程的速率常数kad为（1.2±0.2）×103mol-1·dm3·s－1；依据不同组装时间形成的自组装膜的特征循环伏安行为，提出了C8AzoC3分子在金表面自组装过程的动态模型．     

金纳米粒子在氨基表面上的组装-pH值的影响

用原子力显微镜（AFM）和表面增强喇曼光谱（SERS）研究了pH值对金纳米粒子在Au／巯基苯胺自组装膜表面上组装效果的影响．AFM结果表明，金纳米粒子在表面上的覆盖度随pH值表现出规律性的变化，巯基苯胺自组装膜的SERS强度随pH值的变化也有类似的趋势．在磁性环境下，氨基未质子化，金粒子难以组装上，而在酸性条件下，氨基质子化带正电，金粒子与基底容易结合．我们认为金纳米粒子和氨基之间的作用属于静电力，pH值同时影响膜表面氨基的质子化程度和金纳米粒子表面的带电量．     

电势诱导的N-异丁酰基-L-半胱氨酸分子在金(111)表面的相转变（英文）

自组装单层膜修饰的功能性基底在生物传感,色谱分析,生物相容性材料等方面均具有潜在应用。本文利用原位电化学扫描隧道显微镜(EC-STM)研究了电势诱导的N-异丁酰基-L-半胱氨酸(L-NIBC)分子在Au(111)表面自组装结构的相转变。我们把Au(111)基底分别浸润在纯的NIBC水溶液和pH=7(磷酸盐缓冲溶液调节)的NIBC溶液中,分别制备了NIBC的α相和β相两种不同的自组装结构。EC-STM观测显示,当改变金的电极电势时,α相和β相的NIBC自组装单层膜出现了多种不同的结构变化。当电压从0.7 V(相对于饱和甘汞电极而言)降低到0.2 V时,α相由有序结构变为无序结构。而对于β相的样品,当E0.3 V时,为无序结构;当电极电势增大到0.4 VE0.5 V时,出现γ相;继续增大到0.5 VE0.7 V时,变为β相。另外,EC-STM图像也证实存在β相转变为α相的可能。综合密度泛函理论计算的结果,我们提出,β相转变为α相的原因可以解释为电极电势的变化引起了Au-COO~-键的断裂,从而引发分子吸附构型变化而导致相变。     

新型偶氮苯硫醇衍生物自组装膜的制备与结构表征

自组装单分子膜(ＳＡＭｓ)是近年来引起广泛注意的一种稳定的、二维有序的、致密的有机超薄膜体系,由于其优越的性能,在润滑、吸附、防腐、电化学及微电子等领域中显示出广阔的应用前景[1～4].自组装单分子膜是使用含有各种活性官能团(如-ＣＯＯＨ,-ＳＨ,-Ｓ-Ｓ-,-ＯＨ,-ＣＮ等)的分子,以化学键的形式与相应的基底(如Ａｕ,Ａｇ,Ｃｕ,Ｐｔ,Ｓｉ,Ｍｉｃａ等)相互作用从而自发地形成自组装膜.根据不同的研究或应用目的合理设计组装分子的结构及基底表面,从而得到具有所需功能的自组装单分子膜是近年来界面科学和材料科学等领域研究的热点之一.…     

苝四羧酸自组装单分子膜的制备及其光电转换性质研究

通过共价键连接的方式在亲水性基底上制备了刚性功能分子3,4,9,10- NFDA1 四羧酸的自组装单分子膜,利用接解角、紫外-可见光谱、电化学循环伏安等方法对所制备的NFDA1 四羧酸自组装膜进行了表征,并初步研究了该自组装膜在ITO电极表面光电转换性质.     

Development of Anti-Interference Enzyme Layer for α -Amylase Measurements in Glucose Containing Samples

Abstract

A glucose oxidase-glucoamylase-bienzyme electrode has been developed and tested for determination of α-amylase activity. To eliminate interfering endogeneous glucose a glucose oxidase-catalase anti-interference layer was coupled with the bienzyme electrode. Linearity was obtained for the kinetic signal up to 1.0 I.U. α-amylase. Glucose was effectively eliminated up to 2 mM final concentration thus not influencing α-amylase determinations. A general concept for anti-interference enzyme layers is suggested.     

Cloning and Characterization of Cold-Adapted α-Amylase from Antarctic <Emphasis Type="Italic">Arthrobacter agilis</Emphasis>

In this study, the gene encoding an α-amylase from a psychrophilic Arthrobacter agilis PAMC 27388 strain was cloned into a pET-28a(+) vector and heterologously expressed in Escherichia coli BL21(DE3). The recombinant α-amylase with a molecular mass of about 80 kDa was purified by using Ni²⁺-NTA affinity chromatography. This recombinant α-amylase exhibited optimal activity at pH 3.0 and 30 °C and was highly stable at varying temperatures (30–60 °C) and within the pH range of 4.0–8.0. Furthermore, α-amylase activity was enhanced in the presence of FeCl₃ (1 mM) and β-mercaptoethanol (5 mM), while CoCl₂ (1 mM), ammonium persulfate (5 mM), SDS (10 %), Triton X-100 (10 %), and urea (1 %) inhibited the enzymatic activity. Importantly, the presence of Ca²⁺ ions and phenylmethylsulfonyl fluoride (PMSF) did not affect enzymatic activity. Thin layer chromatography (TLC) analysis showed that recombinant A. agilis α-amylase hydrolyzed starch, maltotetraose, and maltotriose, producing maltose as the major end product. These results make recombinant A. agilis α-amylase an attractive potential candidate for industrial applications in the textile, paper, detergent, and pharmaceutical industries.     

壳聚糖与丙烯腈接枝共聚物的制备及固定化α-淀粉酶研究

本文以过硫酸钾/亚硫酸氢钠为引发体系,制备了丙烯腈接枝壳聚糖的共聚物,并以 其为载体固定化α-淀粉酶,探讨了固定化酶的最佳制备条件和固定化酶的性质,并与游离 酶、壳聚糖作为载体的固定化α-淀粉酶进行了比较,结果表明,丙烯腈接枝壳聚糖共聚物 是固定化α-淀粉酶的优良载体。     

Evaluation of Octyl-β-D-Glucopyranoside (OGP) for Cytotoxic,Hemolytic<Emphasis Type="Italic">,</Emphasis> Thrombolytic,and Antibacterial Activity

The current study indicates that octyl-β-D-glucopyranoside (OGP) as a detergent which has the ability to make the lipid layer stiff. OGP was subjected for toxicity studies and in vitro cytotoxicty assays on cancerous HeLa and non-cancerous myoblasts H9c2 cell lines. Test against aquatic organisms were carried out in Artemia salina and LC₅₀ values were calculated. Hemolytic activity tested for blood bio-compalibity showed hemolysis rate of 10–16%, followed by thrombolytic activity to burst the clots in blood. Also, the samples showed good lysis when compared to the standard streptokinase. Furthermore, α-amylase activity has been carried out to check the inhibition of α-amylase by the OGP. Finally, antibacterial activity has been tested against four different pathogens and their MIC values have been calculated.     

In vitro inhibitory effects of cyandin-3-rutinoside on pancreatic α-amylase and its combined effect with acarbose

The inhibitory activity on pancreatic α-amylase by cyanidin-3-rutinoside was examined in vitro. The IC?? value of cyanidin-3-rutinoside against pancreatic α-amylase was 24.4 ± 0.1 μM. The kinetic analysis revealed that pancreatic α-amylase was inhibited by cyanidin-3-rutinoside in a non-competitive manner. The additive inhibition of a combination of cyanidin-3-rutinoside with acarbose against pancreatic α-amylase was also found. These results provide the first evidence for the effect of cyanidin-3-rutinoside in a retarded absorption of carbohydrates by inhibition of pancreatic α-amylase which may be useful as a potential inhibitor for prevention and treatment of diabetes mellitus.     

Immobilization of Amylases on Silica Support to Study Breakdown Products of Potato Starch by HPLC

Abstract

Immobilization of α- and β-amylases on epoxypropylsilanized PartiSphere-5 was achieved. Hydrolysis of 2% potato starch solution yielded limit dextrin on α-amylase bound column while a mixture of limit dextrin, maltose and glucose was obtained from β-amylase bound column. The β-amylase bound column converted limit dextrin from α-amylase column into glucose.     

A new colorimetric assay for amylase based on starch-supported Cu/Au nanocluster peroxidase-like activity

In this paper, we present a new colorimetric technique as a novel assay for the easy and direct detection of α-amylase activity. This detection system utilizes the interaction of α-amylase with starch that is supporting copper/gold (Cu/Au) nanoclusters. The Cu/Au nanoclusters are synthesized using starch as a stabilizing agent at room temperature. These nanoclusters show robust peroxidase-like activity and are able to catalyze the oxidation of TMB (3,3,5,5-tetramethylbenzidine) in the presence of hydrogen peroxide (H₂O₂), leading to the generation of a blue-colored solution. The α-amylase detection mechanism is based on the digestion of the starch by α-amylase, which results in nanocluster aggregation, leading to increased nanoparticle size and thus decreased peroxidase-like activity of the Cu/Au NCs. Experiments showed that the gradual addition of α-amylase causes the peroxidase activity to decrease step by step in a linear fashion. Using this method, colorimetric sensing of α-amylase was achieved with a detection limit (LOD) of 0.04 U/mL and a linear range of 0.1–10 U/mL. This method is significantly selective for α-amylase and could be affordably and conveniently applied to the detection of α-amylase in blood serum.

Graphical Abstract

     

HPLC study of starch hydrolysis products obtained with α-amylase from bacillus amyloliquefaciens and bacillus licheniformis

Two bacterial α-amylases from new industrial strains were studied: α-amylase fromBacillus amyloliquefaciens CCM 3502 (Czechoslovak) and thermostable α-amylase fromBacillus licheniformis 44MB82 (Bulgarian). The thermostable enzyme hydrolyzed starch mainly to dextrins, and after 1 h, 30% of the products were oligosaccharides. TheB. amyloliquefaciens enzyme produced more maltooligosaccharides than the first enzyme (B. licheniformis). Within 1 h, up to 80% of the substrate were hydrolyzed, giving different spectrum of oligosaccharides in comparison with the thermostable one.     

A new potentiometric sensor for the determination of α-amylase activity

A platinum redox sensor for the direct potentiometric determination of α-amylase concentration has been described. The sensor measured the amount of triiodide released from a starch-triiodide complex, which was correlated with the α-amylase activity after biocatalytic starch degradation. The composition and stability of the potassium triiodide solution was optimized. The starch-triiodide complex was characterized potentiometrically at variable starch and triiodide concentrations. The response mechanism of the platinum redox sensor towards α-amylase was proposed and the appropriate theoretical model was elaborated. The results obtained using the redox sensor exhibited satisfactory accuracy and precision and good agreement with a standard spectrophotometric method and high-sensitive fully automated descret analyser method. The sensor was tested on pure α-amylase (EC 3.2.1.1, Fluka, Switzerland), industrial granulated α-amylase Duramyl 120 T and an industrial cogranulate of protease and α-amylase Everlase/Duramyl 8.0 T/60 T. The detection limit was found to be 1.944 mU for α-amylase in the range of 0-0.54 U (0-15 μg), 0.030 mKNU for Duramyl 120 T in the range of 0-9.6 mKNU (0-80 μg) and 0.032 mKNU for Everlase/Duramyl 8.0 T/60 T in the range of 0-9.24 mKNU (0-140 μg).     

Water Structure in the Contact Layer on the Surface of Crystalline Silver Iodine

The basal face of a silver iodide crystal in unsaturated water vapor is covered by a continuous molecular layer which serves as an underlying film. The structure of the film demonstrates long-range molecular order and looks like a honeycomb. Thus, macroscopic manifestations of the substrate wetting are due to the structure of the underlying film rather than the substrate crystal surface as such. A quarter of hydrogen bonds of the film molecules participate in bonding with the ions of the second crystallographic layer of the substrate. Three other quarters ensure the integrity of the film. The interactions with the ions of the first crystallographic layer are antibonding in nature. No free molecules serving as hydrogen bond donors are left on the film surface to keep vapor molecules. The shape of the free energy function associated with the adsorption of vapor molecules indicates its markedly layered nature.