Microreactor system with immobilized enzyme on polydimethylsiloxane (PDMS) polymers

Microsystems, specifically microreactors, open the gate to new, improved analytical techniques while offering many advantages for a large number of applications in chemical engineering, pharmacy, medicine, and biotechnology. This study explored the feasibility of fabrication of microreactors using polydimethylsiloxane (PDMS) as a support for enzyme immobilization. Urease enzyme was used for catalyzing the conversion of urea to ammonia. PDMS (polydimethylsiloxane) is a silicone-based elastomeric polymer. Traditional micromanufacturing technology was employed for reactor mold fabrication. The mold was fabricated based on photolithography techniques, and SU-8 photoresist was used to construct reactor structure templates. The resulting silicon-wafer based reactor molds were then used repeatedly to generate PDMS microreactors. One advantage of using an immobilized enzyme system is that the bio-catalyst is retained within the reactor system and enables high concentrations to be maintained. Two enzyme immobilization methods were explored for use with PDMS microreactor systems. One used CMC (1-cyclohexyl-3-(2-morpholineoeethyl) carbodiimide metho-p-tolunensulfonate) as a crosslinker for covalently binding the enzyme to the PDMS microreactor surface. The other employed directly incorporating the enzyme into the uncured polymer. The latter method provided a higher urease activity and was used for most microreactor studies. To allow an examination of reactor path length, two different reactor templates were applied for evaluation: straight- and wave-channel microreactors. The reactors were tested with different enzyme loadings, feed flowrates, channel lengths, and different operation environments. The wave-channel reactors exhibited considerably high urea conversions at relatively higher flowrates compared with the straight-channel reactors. Urea conversion was about 90% in wave-channel reactor with 0.001 ml/min flowrate and 0.01 g/g PDMS urease loading, whereas for straight-channel reactor, it is only about 10% urea conversion. A mathematical model was developed for the microreactors tested. The predicted results were consistent with the experiment results for the straight-charnel reactors with short-channels. For the wave-channel reactors, the model showed large deviation from experimented results. The longer the channel length, the greater the deviation. Several assumptions were considered to account for the deviations: channel structure, ammonium ion inhibition, and reactive surface estimation

Towards deeper understanding of the search interfaces of the deep Web

Many databases have become Web-accessible through form-based search interfaces (i.e., HTML forms) that allow users to specify complex and precise queries to access the underlying databases. In general, such a Web search interface can be considered as containing an interface schema with multiple attributes and rich semantic/meta information; however, the schema is not formally defined in HTML. Many Web applications, such as Web database integration and deep Web crawling, require the construction of the schemas. In this paper, we first propose a schema model for representing complex search interfaces, and then present a layout-expression based approach to automatically extract the logic attributes from search interfaces. We also rephrase the identification of different types of semantic information as a classification problem, and design several Bayesian classifiers to help derive semantic information from extracted attributes. A system, WISE-iExtractor, has been implemented to automatically construct the schema from any Web search interfaces. Our experimental results on real search interfaces indicate that this system is highly effective

Grape SnRK2.7 Positively Regulates Drought Tolerance in Transgenic <i>Arabidopsis</i>

In this study, we obtained and cloned VvSnRK2.7 by screening transcriptomic data to investigate the function of the grape sucrose non-fermenting kinase 2 (SnRK2) gene under stress conditions. A yeast two-hybrid (Y2H) assay was used to further screen for interaction proteins of VvSnRK2.7. Ultimately, VvSnRK2.7 was heterologously expressed in Arabidopsis thaliana, and the relative conductivity, MDA content, antioxidant enzyme activity, and sugar content of the transgenic plants were determined under drought treatment. In addition, the expression levels of VvSnRK2.7 in Arabidopsis were analyzed. The results showed that the VvSnRK2.7-EGFP fusion protein was mainly located in the cell membrane and nucleus of tobacco leaves. In addition, the VvSnRK2.7 protein had an interactive relationship with the VvbZIP protein during the Y2H assay. The expression levels of VvSnRK2.7 and the antioxidant enzyme activities and sugar contents of the transgenic lines were higher than those of the wild type under drought treatment. Moreover, the relative conductivity and MDA content were lower than those of the wild type. The results indicate that VvSnRK2.7 may activate the enzyme activity of the antioxidant enzyme system, maintain normal cellular physiological metabolism, stabilize the berry sugar metabolism pathway under drought stress, and promote sugar accumulation to improve plant resistance

Molecular evolution of Phytocyanin gene and analysis of expression at different coloring periods in apple (Malus domestica)

Abstract Background PC (phytocyanin) is a class of copper-containing electron transfer proteins closely related to plant photosynthesis, abiotic stress responses growth and development in plants, and regulation of the expression of some flavonoids and phenylpropanoids, etc., however, compared with other plants, the PC gene family has not been systematically characterized in apple. Results A total of 59 MdPC gene members unevenly distributed across 12 chromosomes were identified at the genome-wide level. The proteins of the MdPC family were classified into four subfamilies based on differences in copper binding sites and glycosylation sites: Apple Early nodulin-like proteins (MdENODLs), Apple Uclacyanin-like proteins (MdUCLs), Apple Stellacyanin-like proteins (MdSCLs), and Apple Plantacyanin-like proteins (MdPLCLs). Some MdPC members with similar gene structures and conserved motifs belong to the same group or subfamily. The internal collinearity analysis revealed 14 collinearity gene pairs among members of the apple MdPC gene. Interspecific collinearity analysis showed that apple had 31 and 35 homologous gene pairs with strawberry and grape, respectively. Selection pressure analysis indicated that the MdPC gene was under purifying selection. Prediction of protein interactions showed that MdPC family members interacted strongly with the Nad3 protein. GO annotation results indicated that the MdPC gene also regulated the biosynthesis of phenylpropanoids. Chip data analysis showed that (MdSCL3, MdSCL7 and MdENODL27) were highly expressed in mature fruits and peels. Many cis-regulatory elements related to light response, phytohormones, abiotic stresses and flavonoid biosynthetic genes regulation were identified 2000 bp upstream of the promoter of the MdPC gene, and qRT-PCR results showed that gene members in Group IV (MdSCL1/3, MdENODL27) were up-regulated at all five stages of apple coloring, but the highest expression was observed at the DAF13 (day after fruit bag removal) stage. The gene members in Group II (MdUCL9, MdPLCL3) showed down-regulated or lower expression in the first four stages of apple coloring but up-regulated and highest expression in the DAF 21 stage. Conclusion Herein, one objective of these findings is to provide valuable information for understanding the structure, molecular evolution, and expression pattern of the MdPC gene, another major objective in this study was designed to lay the groundwork for further research on the molecular mechanism of PC gene regulation of apple fruit coloration

and Retrieval – retrieval model, search process.

In this paper, we describe MySearchView – a system for assembling search engines into metasearch engines. With this system, any user can create a metasearch engine by simply letting the system know the URLs of the search engines the user wants to be included and the metasearch engine will be built fully automatically. In this paper, the main steps of building metasearch engines will be sketched. We will also outline our plan to demonstrate all the features of MySearchView

Single-Crystal Graphene-Directed van der Waals Epitaxial Resistive Switching

Graphene has been broadcasted as a promising choice of electrode and substrate for flexible electronics. To be truly useful in this regime, graphene has to prove its capability in ordering the growth of overlayers at an atomic scale, commonly known as epitaxy. Meanwhile, graphene as a diffusion barrier against atoms and ions has been shown in some metal–graphene–dielectric configurations for integrated circuits. Guided by these two points, this work explores a new direction of using graphene as a bifunctional material in an electrochemical metallization memory, where graphene is shown to (i) order the growth of a low-ionicity semiconductor ZnS single-crystalline film and (ii) regulate the ion migration in the resistive switching device made of Cu/ZnS/graphene/Cu structures. The ZnS film is confirmed to be van der Waals epitaxially grown on single-crystal graphene with X-ray structural analysis and Raman spectroscopy. Charge transport studies with controlled kinetic parameters reveal superior ion regulating characteristic of graphene in this ZnS-based resistive switching device. The demonstration of the first graphene-directed epitaxial wide band gap semiconductor resistive switching suggests a possible and promising route toward flexible memristors

Revealing the Crystalline Integrity of Wafer-Scale Graphene on SiO₂/Si: An Azimuthal RHEED Approach

The symmetry of graphene is usually determined by a low-energy electron diffraction (LEED) method when the graphene is on the conductive substrates, but LEED cannot handle graphene transferred to SiO₂/Si substrates due to the charging effect. While transmission electron microscopy can generate electron diffraction on post-transferred graphene, this method is too localized. Herein, we employed an azimuthal reflection high-energy electron diffraction (RHEED) method to construct the reciprocal space mapping and determine the symmetry of wafer-size graphene both pre- and post-transfer. In this work, single-crystalline Cu(111) films were prepared on sapphire(0001) and spinel(111) substrates with sputtering. Then the graphene was epitaxially grown on single-crystalline Cu(111) films with a low pressure chemical vapor deposition. The reciprocal space mapping using azimuthal RHEED confirmed that the graphene grown on Cu(111) films was single-crystalline, no matter the form of the monolayer or multilayer structure. While the Cu(111) film grown on sapphire(0001) may occasionally consist of 60° in-plane rotational twinning, the reciprocal space mapping revealed that the in-plane orientation of graphene grown atop was not affected. The proposed method for checking the crystalline integrity of the post-transferred graphene sheets is an important step in the realization of the graphene as a platform to fabricate electronic and optoelectronic devices