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Abnormal miRNA expressions are closely related to the occurrence and development of cancers. It is of great significance to monitor miRNA expression levels for early diagnosis and therapy of the diseases. This study presents two i...
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Abnormal miRNA expressions are closely related to the occurrence and development of cancers. It is of great significance to monitor miRNA expression levels for early diagnosis and therapy of the diseases. This study presents two independent colorimetric strategies for simultaneously monitoring multiple miRNAs based on cross-linking or non-cross-linking aggregations of gold nanoparticles (AuNPs). By introducing a Y shaped DNA structure and two types of DNA modified AuNPs, a triple-input DNA AND logic gate is facilely developed with the cross-linking aggregation of AuNPs as the signal output. To improve the sensitivity and shorten reaction time, the logic gate is modified by further employing a three DNA strands formed duplex and hybridization chain reaction. Non-cross-linking aggregation of AuNPs is used to evaluate the concentration of initial miRNA inputs. This strategy does not require DNA modification of AuNPs and ultrahigh sensitivity is achieved with the amplification of hybridization chain reaction. The present work may provide powerful tools for multiple miRNAs diagnostics and inspire further development of DNA based logic gates.
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1-Cyanocyclohexaneacetic acid (1-CHAA) is an important intermediate in the preparation of gabapentin. Regioselective biotransformation of 1-cyanocyclohexaneacetonitile (1-CHAN) into 1-CHAA, mediated by the immobilization of recomb...
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1-Cyanocyclohexaneacetic acid (1-CHAA) is an important intermediate in the preparation of gabapentin. Regioselective biotransformation of 1-cyanocyclohexaneacetonitile (1-CHAN) into 1-CHAA, mediated by the immobilization of recombinant microbial nitrilase, is a novel and promising strategy for its production. In this study, a recombinant E. colt expressing Acidovorax facilis nitrilase was flocculated with polyethylenemine, followed by cross-linking with glutaraldehyde to obtain cross-linked cell aggregates (CLCAs). Under the optimum preparation conditions, the activity recovery of CLCAs reached 68%. Characterization of the CLCAs showed that the optimum pH was not affected by cross-linking, but cross-linking resulted in slightly different optimum temperature. The half-life of CLCAs at 45 degrees C was 266.5 h, which is 11.6-times higher than that of the free cells. Preparative-scale biotransformation of 1-CHAN to 1-CHAA at high substrate loading (up to 1.0 M) was performed using CLCAs as the biocatalyst in a 2L stirred reactor, resulting in an conversion of 91%, with a productivity of 244.5 g L-1 d(-1). The CLCAs also exhibited a high operational stability and even after 30 cycles of reaction, it retained > 80% of the initial conversion.
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Nanoparticles (NPs) may be exploited to make practical materials that are capable of the selective detection of (bio)molecules. Sensing with NPs often depends on the ability to selectively form aggregates. For instance, Mirkin et ...
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Nanoparticles (NPs) may be exploited to make practical materials that are capable of the selective detection of (bio)molecules. Sensing with NPs often depends on the ability to selectively form aggregates. For instance, Mirkin et al. introduced a bio-barcode amplification method for ultrasensitive protein detection.'' Another important study involves the detection of copper ions by hybrid AuNP assemblies in click chemistry. The structures of AuNP-based assemblies can also be controlled electrochemically or by light. However, despite these successes, controlling the properties and structure of NP-based assemblies with organic cross-linkers (CLs) still remains a challenge. We have previously shown that the molecular geometry of CLs and the number of possible NP binding sites are related to the formation of hybrid AuNP assemblies and their associated optical properties.
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Structurally well-defined organic compounds have the ability to direct the formation of large assemblies in solution and in the solid state. Control over nanoparticle (NP) assemblies has been reported with a variety of cross-linke...
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Structurally well-defined organic compounds have the ability to direct the formation of large assemblies in solution and in the solid state. Control over nanoparticle (NP) assemblies has been reported with a variety of cross-linkers (CLs), including polymers, charged molecules, dendrimers, and biomolecules (e.g., DNA, antigen-antibody, and avidin-biotin) to name but a few. In particular, the formation of NP assemblies has been studied as a function of the size or charge characteristics of the CL. Nevertheless, designing and predicting the properties and structure of hybrid NP-based assemblies based on a given molecular structure is still a difficult task. Systematic variation of the CL (2D vs. 3D geometry, number of potential NP binding sites, size, symmetry, etc.) is needed to gain fundamental insight into the factors that control the physicochemical properties of the resulting hybrid assemblies.
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Short-chain fructooligosaccharides (scFOSs) can be produced from the levan hydrolysis using levanase. Levanase from Bacillus lehensis G1 (rlevblg1) is an enzyme that specifically converts levan to scFOSs. However, the use free lev...
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Short-chain fructooligosaccharides (scFOSs) can be produced from the levan hydrolysis using levanase. Levanase from Bacillus lehensis G1 (rlevblg1) is an enzyme that specifically converts levan to scFOSs. However, the use free levanase presents a lack of stability and reusability, thus hindering the synthesis of scFOSs for continuous actions. Here, CLEAs for rlevblg1 were prepared and characterized. Cross-linked levanase aggregates using glutaraldehyde (CLLAs-ga) and bovine albumin serum (CLLAs-ga-bsa) showed the best activity recovery of 92.8% and 121.2%, respectively. The optimum temperature of CLLAs-ga and CLLAs-ga-bsa was increased to 35 degrees C and 40 respectively, from its free rlevblg1 (30 degrees C). At high temperature (50 degrees C), the half-life of CLLAs-ga-bsa was higher than that of free rlevblg1 and CLLAs-ga. Both CLLAs exhibited higher stability at pH 9 and pH 10. Hyperactivation of CLLAs-ga-bsa was achieved with an effectiveness factor of more than 1 and with improved catalytic efficiency. After 3 h reaction, CLLAs-ga-bsa produced the highest total scFOSs yield of 35.4% and total sugar of 60.4% per gram levan. Finally, the reusability of CLLAs for 8 cycles with more than 50% activity retained makes them as a potential synthetic catalyst to be explored for scFOSs synthesis. (C) 2020 Elsevier B.V. All rights reserved.
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Short-chain fructooligosaccharides (scFOSs) can be produced from the levan hydrolysis using levanase. Levanase from Bacillus lehensis G1 (rlevblg1) is an enzyme that specifically converts levan to scFOSs. However, the use of free ...
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Short-chain fructooligosaccharides (scFOSs) can be produced from the levan hydrolysis using levanase. Levanase from Bacillus lehensis G1 (rlevblg1) is an enzyme that specifically converts levan to scFOSs. However, the use of free levanase presents a lack of stability and reusability, thus hindering the synthesis of scFOSs for continuous reactions. Here, CLEAs for rlevblg1 were prepared and characterized. Cross-linked levanase aggregates using glutaraldehyde (CLLAs-ga) and bovine albumin serum (CLLAs-ga-bsa) showed the best activity recovery of 92.8% and 121.2%, respectively. The optimum temperature of CLLAs-ga and CLLAs-ga-bsa was increased to 35 degrees C and 40 degrees C, respectively, from its free rlevblg1 (30 degrees C). At high temperature (50 degrees C), the half-life of CLLAs-ga-bsa was higher than that of free rlevblg1 and CLLAs-ga. Both CLLAs exhibited higher stability at pH 9 and pH 10. Hyperactivation of CLLAs-ga-bsa was achieved with an effectiveness factor of more than 1 and with improved catalytic efficiency. After 3 h reaction, CLLAs-ga-bsa produced the highest total scFOSs yield of 35.4% and total sugar of 60.4% per gram levan. Finally, the reusability of CLLAs for 8 cycles with more than 50% activity retained makes them as a potential synthetic catalyst to be explored for scFOSs synthesis. (c) 2020 Elsevier B.V. All rights reserved.
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Genipin is a nontoxic natural cross-linker that was successfully used to prepare cross-linked enzyme aggregates (CLEAs) of Trametes versicolor laccase. The recovered activity of CLEAs was influenced by the co-solvent type, genipin...
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Genipin is a nontoxic natural cross-linker that was successfully used to prepare cross-linked enzyme aggregates (CLEAs) of Trametes versicolor laccase. The recovered activity of CLEAs was influenced by the co-solvent type, genipin concentration, cross-linking time, preparation pH, and bovine serumalbumin (BSA; amino group feeder) concentration. The characteristics of CLEAs prepared using genipin under optimal conditions (genipin-BSA-CLEAs) were compared with those of typical CLEAs prepared using glutaraldehyde or dextran polyaldehyde. Genipin-BSA-CLEAs were nano-sized (average diameter, approximately 700 nm), had a ball-like shape, showed a narrow size distribution, and exhibited the highest substrate affinity among the prepared CLEAs. The thermal stability of genipin-BSA-CLEAs was 6.8-fold higher than that of free laccase, and their pH stability was also much higher than that of free laccase in the tested range. Additionally, genipin-BSA-CLEAs retained 85% of their initial activity after 10 cycles of reuse. Particularly, genipin-BSA-CLEAs showed higher thermal and pH stability than CLEAs that were cross-linked using glutaraldehyde. Therefore, genipin represents an alternative to toxic compounds such as glutaraldehyde during cross-linking to prepare CLEAs. (C) 2020 Elsevier B.V. All rights reserved.
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Hypothesis: Uniform cross-linked cellulase aggregate (XCA) can be prepared by using a millifluidic reactor which consists of two inlets and a Y-junction, because mixing pattern and spatial distribution of reactants can be controll...
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Hypothesis: Uniform cross-linked cellulase aggregate (XCA) can be prepared by using a millifluidic reactor which consists of two inlets and a Y-junction, because mixing pattern and spatial distribution of reactants can be controlled precisely. Experiments: Aqueous cellulase solution is mixed with acetonitrile (as a precipitant) and 20 mM of glutaraldehyde (as a cross-linker) at the Y-junction. XCA is collected from the outlet of the reactor. Findings: Uniform XCA, with an average size between 200 nm and 400 nm, can be formed inside the reactor. Unlike free cellulase, XCA is insoluble such that it can be filtered out from the solution. It can be used alone or absorb on silica gel (XCA-Si) as a catalyst for hydrolyzing carboxymethyl cellulose (CMC). Interestingly, XCA-Si shows highest activity at pH 4.8 and 50 °C, which is similar to the optimal condition of free cellulase. Moreover, XCA-Si is more stable than free cellulase at high temperature (>60 °C). It precipitates naturally and can be recycled at least 5 times after the hydrolysis of CMC.
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