MnO2纳米粒子固载纤维素酶用于高效水解农业废弃物制备生物乙醇

纤维素酶是一种有效的纤维质类物质水解催化剂,工业应用时可通过固定化纤维素酶来降低其成本。本文将烟曲霉原变种JCF产生的纤维素酶固定在MnO2纳米颗粒上。 MnO2可提高纤维素酶的活性,并充当一个更好的载体。采用扫描电镜表征了所制MnO2纳米粒子及其负载纤维素酶的表面性质,以傅里叶变换红外光谱分析了固定在MnO2纳米粒子上纤维素酶的官能团性质。纤维素酶在MnO2纳米粒子上最大的固定化效率为75%。考察了固定化纤维素酶的活性、操作pH值、温度、热稳定性和重复使用性等性质。结果表明,所制固定化酶的稳定性比游离酶更高。固定于MnO2纳米粒子上的纤维素酶可用于纤维质类物质的水解反应,且能在较宽的温度和pH值范围内使用。表征结果证实了该催化剂具有非常高的催化纤维素类物质水解的活性。     

Statistical and evolutionary optimisation of operating conditions for enhanced production of fungal <Emphasis Type="SmallCaps">l</Emphasis>-asparaginase

A three-level central composite design of the Response Surface Methodology and the Artificial Neural Network-linked Genetic Algorithm were applied to find the optimum operating conditions for enhanced production of l-asparaginase by the submerged fermentation of Aspergillus terreus MTCC 1782. The various effects of the operating conditions, including temperature, pH, inoculum concentration, agitation rate, and fermentation time on the experimental production of l-asparaginase, were fitted to a second-order polynomial model and non-linear models using Response Surface Methodology and the Artificial Neural Network, respectively. The Artificial Neural Network model fitted well, achieving a higher coefficient of determination (R ² = 0.999) than the second-order polynomial model (R ² = 0.962). The l-asparaginase activity (38.57 IU s mL⁻¹) predicted under the optimum conditions of 32.08°C, pH of 5.85, inoculum concentration of 1 vol. %, agitation rate of 123.5 min⁻¹, and fermentation time of 55.1 h was obtained using the Artificial Neural Networklinked Genetic Algorithm in very close agreement with the activity of 37.84 IU mL⁻¹ achieved in confirmation experiments.     

Surface enhanced Raman scattering studies of acetophenone on colloidal silver particles

Intense Raman scattering by acetophenone molecules adsorbed on colloidal silver particles is reported. Greater enhancement is observed for the ring breathing and ring stretching vibrations. The orientation determination analysis shows that the adsorption of acetophenone molecule is neither through its co-ordinating site nor through itsπ-orbital system and there is no strong chemical interaction. However significant intensity enhancement for several vibrations suggests that the contribution is from classical electromagnetic field on the rough surface.     

Fluorescence properties and photophysics of the sulfoindocyanine Cy3 linked covalently to DNA

The sulfoindocyanine Cy3 is one of the most commonly used fluorescent dyes in the investigation of the structure and dynamics of nucleic acids by means of fluorescence methods. In this work, we report the fluorescence and photophysical properties of Cy3 attached covalently to single-stranded and duplex DNA. Steady-state and time-resolved fluorescence techniques were used to determine fluorescence quantum yields, emission lifetimes, and fluorescence anisotropy decays. The existence of a transient photoisomer was investigated by means of transient absorption techniques. The fluorescence quantum yield of Cy3 is highest when attached to the 5' terminus of single-stranded DNA (Cy3-5' ssDNA), and decreases by a factor of 2.4 when the complementary strand is annealed to form duplex DNA (Cy3-5' dsDNA). Substantial differences were also observed between the 5'-modified strands and strands modified through an internal amino-modified deoxy uridine. The fluorescence decay of Cy3 became multiexponential upon conjugation to DNA. The longest lifetime was observed for Cy3-5' ssDNA, where about 50% of the decay is dominated by a 2.0-ns lifetime. This value is more than 10 times larger than the fluorescence lifetime of the free dye in solution. These observations are interpreted in terms of a model where the molecule undergoes a trans-cis isomerization reaction from the first excited state. We observed that the activation energy for photoisomerization depends strongly on the microenvironment in which the dye is located. The unusually high activation energy measured for Cy3-5' ssDNA is an indication of dye-ssDNA interactions. In fact, the time-resolved fluorescence anisotropy decay of this sample is dominated by a 2.5-ns rotational correlation time, which evidences the lack of rotational freedom of the dye around the linker that separates it from the terminal 5' phosphate. The remarkable variations in the photophysical properties of Cy3-DNA constructs demonstrate that caution should be used when Cy3 is used in studies employing DNA conjugates.     

Development of environmental friendly castor oil‐based waterborne polyurethane dispersions with polyaniline

This study describes the fabrication and characterization of castor oil‐based waterborne polyurethane/polyaniline (COWPU/PAni) conducting polymer blend films. The COWPU synthesized from isophorone diisocyanate was reacted with castor oil to form prepolymers, which were chain extended by reacting it with N‐methyldiethanolamine. Quaternization and self‐emulsification including deionized water followed in COWPU dispersions. Also, COWPU/PAni hybrid dispersions were synthesized with 2, 4, and 6 wt% of PAni–dodecyl benzene sulfonic acid to make different conductive composites. The outcome of COWPU/PAni was characterized by Fourier transform infrared spectrometer, differential scanning calorimeter, thermogravimetric analysis, dynamic mechanical and thermal analyzer, and scanning electron microscopy analysis. According to Fourier transform infrared spectrometer analysis, hydrogen bonding appears between –NH of PAni and C?O of COWPU. Meanwhile, incorporating PAni can improve the thermal stability of COWPU. The resulting COWPU/PAni conducting blend films can be used as antistatic and anticorrosive coating materials. Copyright © 2016 John Wiley & Sons, Ltd.     

Mechanistic investigation of oxidation of aromatic anils by isonicotinium dichromate in acidic medium. A kinetic study

Abstract Under identical experimental conditions the kinetics of oxidation of aromatic anils to benzaldehyde and nitrosobenzene, by isonicotinium dichromate, has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. Ionic strength has no significant effect on the conversion. The added Mn(II) decreases the rate of the reaction. The added acrylonitrile has no effect on the reaction rate indicating the absence of free radical mechanism. Highly negative ΔS ^# values indicate a structured transition state. The deviation of Hammett plot is noted and a concave downward curve is obtained for the anils with substituents in the aniline moiety. The observed break in the log k _obs versus σ is attributed to the change in the transition state whereas the linear plot is observed for the substituents in the benzaldehyde moiety. A suitable mechanism has been proposed. Graphical Abstract Mechanistic investigation of oxidation of aromatic anils by isonicotinium dichromate in acidic medium. A kinetic study.      

Synthesis,crystal structure and molecular docking studies of novel 2-(4-(4-substitutedphenylsulfonyl)piperazin-1-yl)quinolone-3-carbaldehyde derivatives

The present work reports the synthesis of novel 2-(4-(4-substitutedphenylsulfonyl) piperazin-1-yl) quinolone-3-carbaldehyde derivatives, namely, 2-(4-tosylpiperazin-1-yl)quinoline-3-carbaldehyde (4a), 2-(4-(4-nitrophenylsulfonyl)piperazin-1-yl)quinoline-3-carbaldehyde (4b) and 2-(4-(4-tert-butylphenylsulfonyl) piperazin-1-yl)quinoline-3-carbaldehyde (4c). These compounds have been characterized by FT-IR, ¹H-NMR, ¹³C-NMR and LCMS. Further, the structures of compounds 4b and 4c have been elucidated by single crystal X-ray diffraction studies. The asymmetric unit of 4b contains two molecules (A and B) and that of 4c contains one. The piperazine ring in both the molecules 4b and 4c has chair conformation and the aldehyde group is twisted with respect to the quinoline group, respectively, by 13.3 (3)°, 18.2 (3)° and 11.2 (3)° in Molecule A & B of 4b and 4c due to the bulky piperazinyl group present in the ortho position. The crystal structures of both features interactions of the type C-H…O, C-H…π_aryl and π_aryl… π_aryl, leading to a three-dimensional (3D) supramolecular architecture in 4b and a one-dimensional (1D) architecture in 4c. The various intermolecular interactions exhibited in 4b and 4c are well supported by Hirshfeld surface and fingerprint plots analysis. Further, the three compounds were evaluated for their in-silico antimicrobial activity. In-silico molecular docking studies were carried out in order to know the binding modes of the synthesized compounds with DNA Gyrase A and N-myristoyltranferase as target proteins for antibacterial and antifungal docking studies, respectively.     

Facile synthesis of 3-alkoxy-4-cyanothiophenes as new building blocks for donor-acceptor conjugated systems

3-Alkoxy-4-cyanothiophenes are efficiently synthesized in two steps from the readily available 4-cyano-3-oxotetrahydrothiophene. Regioisomers of bithiophene derivatives are easily synthesized by playing on the strong electronic dissymmetry of the thiophene ring induced by the alkoxy and cyano groups.     

Biofilm inhibition and antimicrobial action of lipopeptide biosurfactant produced by heavy metal tolerant strain Bacillus cereus NK1

Biosurfactants are worthful microbial amphiphilic molecules with efficient surface-active and biological properties applicable to several industries and processes. Among them lipopeptides represent a class of microbial surfactants with increasing scientific, therapeutic and biotechnological interests. A heavy metal tolerant Bacillus strain has been isolated and the biofilm inhibition and antimicrobial activity of biosurfactant produced by the strain have been studied. Biosurfactant production was confirmed by the conventional screening methods including hemolytic activity, drop collapsing test, oil displacement test, emulsification and lipase production assays. The biosurfactant produced by this strain was a lipopeptide and exhibited strong surface activity. The biosurfactant has been characterized using FTIR, TLC and HPLC. The minimum active dose of this biosurfactant when compared with the other chemical surfactants was found as 0.150±0.06 μg. The critical micelle concentration was found to be 45 mg/l. The biosurfactant was found to be stable and active over a wide range of pH, temperature and NaCl concentration. It was also able to emulsify a wide range of hydrocarbons and oils thereby extending its application for the bioremediation of oil contaminated sites. The biosurfactant exhibited significant reduction in biofilm formation by pathogens and showed potent antimicrobial activity against various gram positive, gram negative bacteria and fungi. Agar diffusion assay for heavy metal resistance showed that the isolate was resistant to ferrous, lead and zinc. Considering the biofilm inhibition and antimicrobial property of biosurfactant, it can be utilized as a potential therapeutic molecule for numerous microbial infections. The heavy metal resistance of the strain can also be harnessed as an invaluable biological tool for in situ bioremediation.     

Biosynthesis, purification and characterization of silver nanoparticles using Escherichia coli

The application of nanoscale materials and structures, usually ranging from 1 to 100 nanometers (nm), is an emerging area of nanoscience and nanotechnology. Nanomaterials may provide solutions to technological and environmental challenges in the areas of solar energy conversion, catalysis, medicine, and water-treatment. The development of techniques for the controlled synthesis of nanoparticles of well-defined size, shape and composition, to be used in the biomedical field and areas such as optics and electronics, has become a big challenge. Development of reliable and eco-friendly processes for synthesis of metallic nanoparticles is an important step in the field of application of nanotechnology. One of the options to achieve this objective is to use ‘natural factories’ such as biological systems. This study reports the optimal conditions for maximum synthesis of silver nanoparticles (AgNPs) through reduction of Ag⁺ ions by the culture supernatant of Escherichia coli. The synthesized silver nanoparticles were purified by using sucrose density gradient centrifugation. The purified sample was further characterized by UV–vis spectra, fluorescence spectroscopy and TEM. The purified solution yielded the maximum absorbance peak at 420 nm and the TEM characterization showed a uniform distribution of nanoparticles, with an average size of 50 nm. X-ray diffraction (XRD) spectrum of the silver nanoparticles exhibited 2θ values corresponding to the silver nanocrystal. The size-distribution of nanoparticles was determined using a particle-size analyzer and the average particle size was found to be 50 nm. This study also demonstrates that particle size could be controlled by varying the parameters such as temperature, pH and concentration of AgNO₃.