Fatigue-crack closure measurements on 2024-t3 sheet specimens

A computer-controlled procedure has been developed for automatic measurement of the crack opening stress S-op during fatigue tests. A crack opening displacement gauge (GOD meter) is used to obtain digital data on the load versus COD curves. Three methods for deriving S-op from the data sets are compared: (1) a slope method, (2) a tangent lines intersecting method, and (3) a tangent point method. The effect of the position of the COD meter with respect to the crack tip on S-op is studied in tests of 2024-T3 specimens. Results of crack growth and S-op are presented for CA loading with an overload, and with an overload followed by an underload.

Application of methyl parathion hydrolase (MPH) as a labeling enzyme

Methyl parathion hydrolase (MPH) is an enzyme that catalyzes the degradation of methyl parathion, generating a yellow product with specific absorption at 405 nm. The application of MPH as a new labeling enzyme was illustrated in this study. The key advantages of using MPH as a labeling enzyme are as follows: (1) unlike alkaline phosphatase (AP), horseradish peroxidase (HRP), and glucose oxidase (GOD), MPH is rarely found in animal cells, and it therefore produces less background noise; (2) its active form in solution is the monomer, with a molecular weight of 37 kDa; (3) its turnover number is 114.70 +/- 13.19 s(-1), which is sufficiently high to yield a significant signal for sensitive detection; and (4) its 3D structure is known and its C-terminal that is exposed to the surface can be easily subjected to the construction of genetic engineering monocloning antibody-enzyme fusion for enzyme-linked immunosorbent assay (ELISA). To demonstrate its utility, MPH was ligated to an single-chain variable fragment (scFv), known as A1E, against a white spot syndrome virus (WSSV) with the insertion of a [-(Gly-Ser)(5)-] linker peptide. The resulting fusion protein MPH-A1E possessed both the binding specificity of the scFv segment and the catalytic activity of the MPH segment. When MPH-A1E was used as an ELISA reagent, 25 ng purified WSSV was detected; this was similar to the detection sensitivity obtained using A1E scFv and the HRP/Anti-E Tag Conjugate protocol. The fusion protein also recognized the WSSV in 1 mu L hemolymph from an infected shrimp and differentiated it from a healthy shrimp.

酶生物燃料电池载体选择及其应用基础研究

酶生物燃料电池（EBFC）是利用酶作为催化剂将化学能转化为电能的装置。由于氧化还原蛋白质和酶通常具有复杂的空间结构，活性中心深埋在它们的肽链中，很难与基底电极进行直接电子传递，从而影响了电池的性能。但使用适当的载体对电极表面进行修饰，可以实现直接的、快速的电子传递。因此，开发稳定性好、成本低、能够有效促进氧化还原蛋白质或酶与基底电极进行直接电子传递的载体成为EBFC发展中的重要课题之一。 本论文主要集中于EBFC中蛋白质或酶载体的选择方面的研究。探讨不同性质的载体，包括半导体电物质、生物相容性物质和导电物质对氧化还原蛋白质或酶的直接电子传递的影响。同时以SiO2纳米粒子为例，探讨了载体促进氧化还原蛋白质直接电子传递的作用机理。通过对不同载体的考察，最终选择了一种合适的材料组装成葡萄糖/O2 EBFC，并考察了EBFC的性能。主要结果如下： 1．将SiO2纳米粒子固定在GC电极上，成功实现了细胞色素c（Cyt c）的准可逆的直接电化学反应，并在这基础上提出双功能机理模型，说明了半导体对氧化还原蛋白质和电极之间的直接电子迁移的影响。 2．发现Cyt c能够在SBA-15膜修饰的电极上实现准可逆的直接电化学反应，并能够对H2O2产生较好的电催化还原效果。 3．以生物相容性物质壳聚糖为载体，分别研究了Cyt c、微过氧化物酶（MP-11）和葡萄糖氧化酶（GOD）的准可逆的直接电化学反应。并发现固载在壳聚糖上的Cyt c和MP-11对H2O2和O2还原有很好的电催化活性，而固载在壳聚糖上的GOD对葡萄糖氧化有很好的电催化活性。 4．以碳纳米管（CNT）为载体，实现了GOD的准可逆的直接电化学反应。并在氧化还原媒介体的作用下实现了其对葡萄糖的电催化氧化。 5．将筛选出的最佳载体组装成葡萄糖/O2 EBFC，分别以葡萄糖氧化酶和漆酶作为阳极和阴极的催化剂，制得有隔膜和无隔膜的EBFC。

直接型生物燃料电池酶催化剂的研究

生物燃料电池作为一种真正意义上的理想绿色环保电源，由于可作为小功率长寿命的体内植入电源，已成为人们研究的热点课题之一。目前对生物燃料电池的研究主要集中在间接型生物燃料电池，已取得一定进展。但是间接型生物燃料电池具有电子传递链长、效率低等弱点，而直接型生物燃料电池有望克服以上缺点，成为更具研究潜力的新一代生物燃料电池。本文从探索简单、有效的酶固定方法入手，制备炭载辣根过氧化物酶（HRP）、漆酶（Lac）、酪氨酸酶（Tyr）作直接型生物燃料电池的阴极催化剂和炭载葡萄糖氧化酶（GoD）作阳极催化剂。用多种谱学方法表征了炭载酶催化剂的结构特征和用电化学方法研究了炭载酶的直接电化学及电催化性能。得到的主要结果和结论如下：1．以比活性高、稳定、结构清楚、有纯的商品化试剂且价廉的HRP为模型分子来探索用平衡吸附法将HRP固定到活性炭表面，用Nofion膜加固并修饰到玻碳（GC）电极上，以期制备得到炭载HRP修饰的Gc电极（HRP-C／GC）。实验结果表明，炭载HRP能进行准可逆的直接电化学反应，式电位（0）在50-700mv／s的范围内几乎不随扫速变化，平均值为C0．362±0．001）v，表观速率常数（ks）为（3．4±0．69）s-1HRP-C/GC电极对HZoZ还原有很好和稳定的电催化活性，表明固定在活性炭上的HRP能保持其生物活性，而且能稳定数月时间。因此，固定在活性炭上的HRP有可能用作直接型生物燃料电池的阴极催化剂。由上述结果可见，用平衡吸附法把HRP固载到活性炭上，并用Nofion膜加固的酶电极的制备方法具有简单且有效的特点，有可能作为直接型生物燃料电池酶催化剂的制备方法。2．用平衡吸附法将Lac和Tyr分别固定到活性炭上，发现炭载Lac和Tyr都能进行准可逆的直接电化学反应，其0，在10-150mv／s的范围内几乎不随扫速而变化，分别为-0．166和-0．139v。另外，还发现炭载Lac和Tyr对02的还原有明显的电催化作用，表明炭载Lac和Tyr仍能保持它们的生物活性，因而能作直接型生物燃料电池的阴极催化剂。3．用平衡吸附法将葡萄糖氧化酶（GOD）固定到活性炭表面，发现炭载GOD能进行准可逆的直接电化学反应，其0，在10-200mv／s的范围内几乎不随扫速而变化，平均值为C0．467±0．002）v；ks值为（1．18±0．59）5-1；且其直接电化学反应是2e＋ZH＋的过程。另外，还发现炭载GOD对p-D（＋）葡萄糖的氧化有明显的电催化作用，表明炭载GOD没有发生变性，仍保持其生物活性，所以能用作直接型生物燃料电池的阳极催化剂。

Growth and fabrication of high performance 980nm strained InGaAs quantum well lasers using novel hybrid material system of InGaAsP and AlGaAs

In this paper, we report on the design, growth and fabrication of 980nm strained InGaAs quantum well lasers employing novel material system of Al-free active region and AlGaAs cladding layers. The use of AlGaAs cladding instead of InGaP provides potential advantages in laser structure design, improvement of surface morphology and laser performance. We demonstrate an optimized broad-waveguide structure for obtaining high power 980nm quantum well lasers with low vertical beam divergence. The laser structure was grown by low-pressure metalorganic chemical vapor deposition, which exhibit a high internal quantum efficiency of similar to 90% and a low internal loss of 1.5-2.5 cm(-1). The broad-area and ridge-waveguide laser devices are both fabricated. For 100 mu m wide stripe lasers with cavity length of 800 mu m, a low threshold current of 170mA, a high slope efficiency of 1.0W/A and high output power of more than 3.5W are achieved. The temperature dependences of the threshold current and the emitting spectra demonstrate a very high characteristic temperature coefficient (T-o) of 200-250K and a wavelength shift coefficient of 0.34nm/degrees C. For 4 mu m-width ridge waveguide structure laser devices, a maximum output power of 340mW with GOD-free thermal roll-over characteristics is obtained.

黑曲霉葡萄糖氧化酶基因的克隆及其在酵母中的高效表达

将黑曲霉葡萄糖氧化酶 (GOD)基因重组进大肠杆菌 酵母穿梭质粒pPIC9,转化甲基营养酵母Pichiapasto risGS115 ,构建出GOD的高产酵母工程菌株。在酵母α Factor及AOX1基因启动子和终止信号的调控下 ,黑曲霉GOD在甲基酵母中大量表达并分泌至胞外 ,经甲醇诱导 3～ 4d ,发酵液中的GOD活力可达 30～ 40u mL。SDS PAGE证实GOD在培养物上清中的含量显著高于其它杂蛋白 ,约占胞外蛋白总量的 6 0 %～ 70 % ,经QSepharoseTM FastFlow离子交换柱一步纯化即达电泳纯。重组酵母GOD比活达 42 6 6 3u mg蛋白 ,是商品黑曲霉GOD的 1 6倍。动力学性质分析表明 ,重组酵母GOD的Km 和kcat分别为 38 2 5mmol L和 34 92 6 6s- 1 ,与商品黑曲霉GOD相比 ,具有更高的催化效率。重组酵母GOD的高活力特性可有效提高葡萄糖传感器的线性检测范围。

Highly ordered mesoporous carbons as electrode material for the construction of electrochemical dehydrogenase- and oxidase-based biosensors

In this work, the excel lent catalytic activity of highly ordered mesoporous carbons (OMCs) to the electrooxidation of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2) was described for the construction of electrochemical alcohol dehydrogenase (ADH) and glucose oxidase (GOD)-based biosensors.

Carbon nanotube/gold nanoparticles/polyethylenimine-functionalized ionic liquid thin film composites for glucose biosensing

A novel glucose biosensor based on immobilization of glucose oxidase (GOD) in thin films of polyethylenimine-functionalized ionic liquid (PFIL), containing a mixture of carbon nanotubes (CNT) and gold nanoparticles (AuNPs) and deposited on glassy carbon electrodes, was developed. Direct electrochemistry of glucose oxidase in the film was observed, with linear glucose response up to 12 mM. The PFIL-stabilized gold nanoparticles had a diameter of 2.4 +/- 0.8 nm and exhibited favorable stability (stored even over one month with invisible change in UV-vis spectroscopic measurements).

Direct electron transfer and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified with Nafion and mesoporous carbon FDU-15

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified with mesoporous carbon FDU-15 (MC-FDU-15) and Nafion by simple technique. The sorption behavior of GOD immobilized on MC-FDU-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that MC-FDU-15 could facilitate the electron exchange between the active center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on the modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and MC-FDU-15 matrices display direct, reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 4.095 s(-1) in 0.1 M phosphate buffer solution (PBS) (pH 7.12).

Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified by Nafion and ordered mesoporous silica-SBA-15

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified by ordered mesoporous silica-SBA-15 and Nafion. The sorption behavior of GOD immobilized on SBA-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that SBA-15 can facilitate the electron exchange between the electroactive center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and SBA-15 matrices displays direct, nearly reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 3.89 s(-1) in 0.1 M phosphate buffer solution (PBS) (pH 7.12).

Direct electrochemistry of glucose oxidase and biosensing for glucose based on carbon nanotubes@SnO2-Au composite

Multiwalled carbon nanotubes@SnO2-Au (MWCNTs@SnO2-Au) composite was synthesized by a chemical route. The structure and composition of the MWCNTs@SnO2-Au composite were confirmed by means of transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Due to the good electrocatalytic property of MWCNTs@SnO2-Au composite, a glucose biosensor was constructed by absorbing glucose oxidase (GOD) on the hybrid material. A direct electron transfer process is observed at the MWCNTs@SnO2-Au/GOD-modified glassy carbon electrode. The glucose biosensor has a linear range from 4.0 to 24.0 mM, which is suitable for glucose determination by real samples. It should be worthwhile noting that, from 4.0 to 12.0 mM, the cathodic peak currents of the biosensor decrease linearly with increasing the glucose concentrations in human blood. Meanwhile, the resulting biosensor can also prevent the effects of interfering species.

Direct Electrochemistry of Glucose Oxidase and Biosensing for Glucose Based on Graphene

We first reported that polyvinylpyrrolidone-protected graphene was dispersed well in water and had good electrochemical reduction toward O-2 and H2O2. With glucose oxidase (GOD) as an enzyme model, we constructed a novel polyvinylpyrrolidone-proteeted graphene/polyethylenimine-ftmctionalized ionic liquid/GOD electrochemical biosensor, which achieved the direct electron transfer of GOD, maintained its bioactivity and showed potential application for the fabrication of novel glucose biosensors with linear glucose response up to 14 mM.

Nanocomposite based on depositing platinum nanostructure onto carbon nanotubes through a one-pot, facile synthesis method for amperometric sensing

Platinum nanoparticles (Pt NPs) were deposited onto multi-walled carbon nanotubes (MWNTs) through direct chemical reduction without any other stabilizing agents. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry were employed to characterize the morphology of the as-prepared nanocomposite (noted as Pt NPs-MWNTs) and further identify the Pt NPs on the surface of MWNTs. The nanocomposite demonstrated the ability to electrocatalyze the oxidation of hydrogen peroxide and substantially raises the response current. A sensitivity of 591.33 mu A mM(-1) cm(-2) was obtained at Pt NPs-MWNTs modified electrode. Thus, we immobilized glucose oxidase (GOD) as a model enzyme on the nanocomposite-based electrode with a thin layer of Nafion to fabricate a glucose biosensor, which showed sensitive and fast response to glucose. The influence of the GOD loading was investigated and the biosensor with an enzyme loading concentration of 10 mg/mL shows optimal performance for glucose detection, that is, a detection limit of 3 mu M and a response time of 3 s, respectively.

Electrochemistry of glucose oxidase immobilized on the carbon nanotube wrapped by polyelectrolyte

A more stably dispersing of multi-wall carbon nanotube composite (noted as PDDA-MWNT), which was obtained by wrapping the MWNT with poly (diallydimethylammonium) chloride (PDDA), was used for the immobilization of glucose oxidase (GOD) and its bioelectrochemical studies. The morphologies and structures of the PDDA-MWNT composite were characterized by environment-canning electron microscopy (ESEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry were used to feature the GOD adsorbed onto the electrode modified by PDDA-MWNT composite. The immobilized GOD at the PDDA-MWNT films exhibited a pair of well-defined nearly reversible redox peaks and a fast heterogeneous electron transfer rate with the rate constant (k(s)) of 2.76 s(-1). In addition, GOD immobilized in this way retained its bioelectrocatalytic activity for the oxidation of glucose. The method of immobilizing GOD without any additional cross-linking agents presented here is easy and facile, which provides a model for other redox enzymes and proteins.