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  • 1
    Language: English
    In: Journal of the American Chemical Society, 02 October 2013, Vol.135(39), pp.14679-90
    Description: Bacteria that cause most of the hospital-acquired infections make use of class C β-lactamase (CBL) among other enzymes to resist a wide spectrum of modern antibiotics and pose a major public health concern. Other than the general features, details of the defensive mechanism by CBL, leading to the hydrolysis of drug molecules, remain a matter of debate, in particular the identification of the general base and role of the active site residues and substrate. In an attempt to unravel the detailed molecular mechanism, we carried out extensive hybrid quantum mechanical/molecular mechanical Car-Parrinello molecular dynamics simulation of the reaction with the aid of the metadynamics technique. On this basis, we report here the mechanism of the formation of the acyl-enzyme complex from the Henry-Michaelis complex formed by β-lactam antibiotics and CBL. We considered two β-lactam antibiotics, namely, cephalothin and aztreonam, belonging to two different subfamilies. A general mechanism for the formation of a β-lactam antibiotic-CBL acyl-enzyme complex is elicited, and the individual roles of the active site residues and substrate are probed. The general base in the acylation step has been identified as Lys67, while Tyr150 aids the protonation of the β-lactam nitrogen through either the substrate carboxylate group or a water molecule.
    Keywords: Anti-Bacterial Agents -- Metabolism ; Aztreonam -- Metabolism ; Cephalothin -- Metabolism ; Citrobacter Freundii -- Enzymology ; Beta-Lactamases -- Metabolism
    ISSN: 00027863
    E-ISSN: 1520-5126
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  • 2
    In: Nature, 2017, Vol.550(7677), p.457
    Description: Construction: use waste for building
    Keywords: Sciences (General) ; Physics;
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 3
    Language: English
    In: Bioresource Technology, 2011, Vol.102(13), pp.6850-6856
    Description: ► This is a new work in the tropical cities, like Varanasi in India. ► The work is based on the combined process of Biofiltration and Ozone treatment of secondary effluent from the wastewater treatment plant. ► Removal efficiency of toxic heavy metals was 55–70%, organic and inorganic contents was 60–85% and microbes ranges between 98–99%. The present work was aimed at studying the efficiency of the combined process of biofiltration with ozonation to improve the quality of secondary effluent. The secondary effluent from the Dinapur Sewage Treatment Plant Varanasi, India was used in this work. The process of biofiltration with the plant species of and , at a flow rate of 262 ml min and plant density of 30 mg L for 48 h, in combination with the process of ozonation with ozone dose of 10 mg L and contact time of 5 min was applied. Results revealed that combined process was statistically most suitable for the highest degradation of physico-chemical and microbial parameters with improving BDOC value. The biofiltration process is able to remove highest percentage of toxic heavy metals from the secondary effluent without production of toxicity. This technique is highly recommendable for tropical wastewater where sewage is mixed with industrial effluents.
    Keywords: Biofiltration ; Ozonation ; Wastewater Treatment ; Macrophytes ; Heavy Metal Toxicity ; Agriculture ; Engineering ; Chemistry
    ISSN: 0960-8524
    E-ISSN: 1873-2976
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  • 4
    In: Journal of Applied Polymer Science, 15 November 2013, Vol.130(4), pp.2912-2922
    Description: The poor mechanical strength and instability of polysaccharide's gel takes away opportunities for versatile application. The grafting of polyacrylamide (PAM) onto polysaccharide was found to be an efficient tool for transforming its properties and obtaining stable and robust composite microspheres (CMs). In this study, free‐radical polymerization reaction was used for the grafting of PAM onto the polysaccharide backbone, and their hydrogel CMs were obtained through an ionotropic gelation method. Porous and buoyant CMs were obtained through the incorporation of sodium bicarbonate into the reaction mixture. Characterizations were done through Fourier transform infrared spectroscopy, thermal and scanning electron microscopy analysis. The mechanical strength and squeezing capacity were evaluated extensively through a modified syringe method developed in‐house. The squeezing capacity of grafted CMs diminished with the formation of a complex interpenetrating network. The Young's modulus, swelling kinetics, mechanical strength, and squeezing capacity of the grafted microspheres were compared extensively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2912–2922, 2013
    Keywords: Biopolymers And Renewable Polymers ; Mechanical Properties ; Synthesis And Processing
    ISSN: 0021-8995
    E-ISSN: 1097-4628
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  • 5
    Language: English
    In: Journal of Applied Physics, 01 March 2011, Vol.109(5)
    Description: This paper presents an analytical model for the internal capacitances of short-channel ion-implanted GaAs MESFETs under dark and illuminated conditions. The device structure considered in this study is a normally-on self-aligned GaAs MESFET with indium tin oxide (ITO) as the Schottky metal for the gate electrode of the device. The gate area of the device is illuminated by an optical radiation of 0.87 μ m from an external source which is coupled into the device through the semitransparent ITO metal at Schottky-gate to modulate the electrical and microwave characteristics of the device. The nonanalytic Gaussian doping profile commonly considered for the channel doping of an ion-implanted GaAs MESFET has been replaced by an analytic Gaussianlike function for the simplicity of the present model. The two-dimensional (2D) potential distribution obtained by solving the 2D Poisson’s equation by including the effect of photo-generated carriers due to the incident optical radiation has been utilized to model the depletion region width below the gate of the short-channel GaAs MESFETs. The depletion width model has then been used to model the internal gate-source and gate-drain capacitances of the device operating under both the linear and saturation regions. The effect of illumination on the Schottky junction at the gate of the MESFET has been modeled by considering an induced photo-voltage developed across the junction that is superimposed on the applied gate bias voltage. The proposed model has been verified by comparing the theoretically predicted results with simulated data obtained by using the commercially available ATLAS TM 2D device simulator.
    Keywords: Articles
    ISSN: 0021-8979
    E-ISSN: 1089-7550
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  • 6
    Language: English
    In: Nature, 03 November 2016, Vol.539(7627), pp.38-39
    Description: Bacteria are expert at adapting to changing lifestyles. Dealing with damaged or misfolded proteins is a key challenge during adaptation to stressful conditions such as high temperature. In such situations, chaperone proteins restore unfolded proteins to their functional, folded states and protease enzymes...
    Keywords: Garbage ; Phosphates
    ISSN: 00280836
    E-ISSN: 1476-4687
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  • 7
    Language: English
    In: Nature, Nov 3, 2016, Vol.539(7627), p.38(2)
    Keywords: Phosphates -- Health Aspects ; Microbial Colonies -- Health Aspects
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 8
    Language: English
    In: Bioresource technology, 2011, Vol.102(3), pp.2481-2486
    Description: The present work was aimed at studying the efficiency of ozone in oxidation processes, coliform inactivation and Disinfection Byproducts (DBPs) formation, associated with the potential of ozone to increase the Biodegradable Dissolved Organic Carbon (BDOC) in secondary effluent with applied ozone doses of 5.0, 10.0 and 15.0mg/L for contact times of 2, 5 and 10min. The wastewater used in this work was collected from the Bhagwanpur Sewage Treatment Plant, Varanasi, India. Results of this experiment showed that 10mg O₃/L O₃ for 5min exposure was found most suitable dose for highest degradation of COD, TOC, UV₂₅₄, color, turbidity and total nitrogen parameters. The inactivation range of microbial biomass range was found in between 95% and 98%. Experiment revealed the fact that aldehydes and carboxylic acid formation were significantly related with the ozone dose and exposure time and ozone might enhance the treatment efficiency of secondary effluent treatment. ; Includes references ; p. 2481-2486.
    Keywords: Sewage Treatment -- Environmental Aspects ; Ozonization -- Environmental Aspects ; Air Pollution -- Environmental Aspects;
    ISSN: 0960-8524
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  • 9
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 2012, Vol.109(31), pp.12497-12502
    Description: Toxin-antitoxin (TA) systems are found on both bacterial plasmids and chromosomes, but in most cases their functional role is unclear. Gene knockouts often yield limited insights into functions of individual TA systems because of their redundancy. The well-characterized F-plasmid–based CcdAB TA system is important for F-plasmid maintenance. We have isolated several point mutants of the toxin CcdB that fail to bind to its cellular target, DNA gyrase, but retain binding to the antitoxin, CcdA. Expression of such mutants is shown to result in release of the WT toxin from a functional preexisting TA complex as well as derepression of the TA operon. One such inactive, active-site mutant of CcdB was used to demonstrate the contribution of CcdB to antibiotic persistence. Transient activation of WT CcdB either by coexpression of the mutant or by antibiotic/heat stress was shown to enhance the generation of drug-tolerant persisters in a process dependent on Lon protease and RecA. An F-plasmid containing a ccd locus can, therefore, function as a transmissible persistence factor. ; p. 12497-12502.
    Keywords: Antibiotics ; Antitoxins ; Proteinases ; Operon ; Active Sites ; Dna Topoisomerase (Atp-Hydrolysing) ; Plasmids ; Loci ; Heat Stress ; Mutants
    ISSN: 0027-8424
    E-ISSN: 10916490
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  • 10
    Language: English
    In: The Journal of Academic Librarianship, 2011, Vol.37(6), pp.543-545
    Description: Digitization is becoming more common in library and information centers throughout India. India's former president Dr. APJ Abdul Kalam, has even entered into the discussion by remarking that a "digital library is where past meets the present and creates a future." With this current growth and interest in digital libraries and institutional repositories, it is useful to look at what is carefully being offered and what is in development. Universities and other organizations are spending large amounts of money on setting up digital libraries and institutional repositories. Therefore it is important to find out how these are being used--and what kind of access they provide. Here, Tripathi and Jeevan provide an overview of digital libraries and institutional repositories in India and to evaluate their features using criteria established in other studies already conducted in India and internationally. They also assess how each of the digital facilities rate on an international scale.
    Keywords: Library & Information Science
    ISSN: 0099-1333
    E-ISSN: 1879-1999
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