Improvement of activity and stability of chloroperoxidase by chemical modification

PubMed Central

Liu, Jian-Zhong; Wang, Min

2007-01-01

Background Enzymes show relative instability in solvents or at elevated temperature and lower activity in organic solvent than in water. These limit the industrial applications of enzymes. Results In order to improve the activity and stability of chloroperoxidase, chloroperoxidase was modified by citraconic anhydride, maleic anhydride or phthalic anhydride. The catalytic activities, thermostabilities and organic solvent tolerances of native and modified enzymes were compared. In aqueous buffer, modified chloroperoxidases showed similar Km values and greater catalytic efficiencies kcat/Km for both sulfoxidation and oxidation of phenol compared to native chloroperoxidase. Of these modified chloroperoxidases, citraconic anhydride-modified chloroperoxidase showed the greatest catalytic efficiency in aqueous buffer. These modifications of chloroperoxidase increased their catalytic efficiencies for sulfoxidation by 12%~26% and catalytic efficiencies for phenol oxidation by 7%~53% in aqueous buffer. However, in organic solvent (DMF), modified chloroperoxidases had lower Km values and higher catalytic efficiencies kcat/Km than native chloroperoxidase. These modifications also improved their thermostabilities by 1~2-fold and solvent tolerances of DMF. CD studies show that these modifications did not change the secondary structure of chloroperoxidase. Fluorescence spectra proved that these modifications changed the environment of tryptophan. Conclusion Chemical modification of epsilon-amino groups of lysine residues of chloroperoxidase using citraconic anhydride, maleic anhydride or phthalic anhydride is a simple and powerful method to enhance catalytic properties of enzyme. The improvements of the activity and stability of chloroperoxidase are related to side chain reorientations of aromatics upon both modifications. PMID:17511866

Chemical Preparation Laboratory for IND Candidate Compounds

DTIC Science & Technology

1990-08-10

Confirmation by 500 MHz Spectroscopy of an Analogue of the Amaryllidaceae Alkaloids, Narciclasine and Pancratistatin." Bjarne Gabrielsen, Department...subdivided into modified nucleosides, alkaloids with synthetically modified precursors and analogues , and miscellaneous heterocycles that possess...or antitumor compounds were modified synthet 4cally to possibly yield novel analogues that possess enhanced activities or show a specific mode of

Aromatic thiol-mediated cleavage of N-O bonds enables chemical ubiquitylation of folded proteins

NASA Astrophysics Data System (ADS)

Weller, Caroline E.; Dhall, Abhinav; Ding, Feizhi; Linares, Edlaine; Whedon, Samuel D.; Senger, Nicholas A.; Tyson, Elizabeth L.; Bagert, John D.; Li, Xiaosong; Augusto, Ohara; Chatterjee, Champak

2016-09-01

Access to protein substrates homogenously modified by ubiquitin (Ub) is critical for biophysical and biochemical investigations aimed at deconvoluting the myriad biological roles for Ub. Current chemical strategies for protein ubiquitylation, however, employ temporary ligation auxiliaries that are removed under harsh denaturing conditions and have limited applicability. We report an unprecedented aromatic thiol-mediated N-O bond cleavage and its application towards native chemical ubiquitylation with the ligation auxiliary 2-aminooxyethanethiol. Our interrogation of the reaction mechanism suggests a disulfide radical anion as the active species capable of cleaving the N-O bond. The successful semisynthesis of full-length histone H2B modified by the small ubiquitin-like modifier-3 (SUMO-3) protein further demonstrates the generalizability and compatibility of our strategy with folded proteins.

Developmental exposure to triclosan alters microbiota community structure and locomotor activity in larval zebrafish

EPA Science Inventory

Growing evidence indicates that host-associated microbiota modify the toxicokinetics and/or toxicodynamics of environmental chemicals; however, current risk assessment methods do not consider interactions between microbiota and chemical toxicity. We previously reported that micro...

Improvement of human cell line activation test (h-CLAT) using short-time exposure methods for prevention of false-negative results.

PubMed

Narita, Kazuto; Ishii, Yuuki; Vo, Phuc Thi Hong; Nakagawa, Fumiko; Ogata, Shinichi; Yamashita, Kunihiko; Kojima, Hajime; Itagaki, Hiroshi

2018-01-01

Recently, animal testing has been affected by increasing ethical, social, and political concerns regarding animal welfare. Several in vitro safety tests for evaluating skin sensitization, such as the human cell line activation test (h-CLAT), have been proposed. However, similar to other tests, the h-CLAT has produced false-negative results, including in tests for acid anhydride and water-insoluble chemicals. In a previous study, we demonstrated that the cause of false-negative results from phthalic anhydride was hydrolysis by an aqueous vehicle, with IL-8 release from THP-1 cells, and that short-time exposure to liquid paraffin (LP) dispersion medium could reduce false-negative results from acid anhydrides. In the present study, we modified the h-CLAT by applying this exposure method. We found that the modified h-CLAT is a promising method for reducing false-negative results obtained from acid anhydrides and chemicals with octanol-water partition coefficients (LogK ow ) greater than 3.5. Based on the outcomes from the present study, a combination of the original and the modified h-CLAT is suggested for reducing false-negative results. Notably, the combination method provided a sensitivity of 95% (overall chemicals) or 93% (chemicals with LogK ow > 2.0), and an accuracy of 88% (overall chemicals) or 81% (chemicals with LogK ow > 2.0). We found that the combined method is a promising evaluation scheme for reducing false-negative results seen in existing in vitro skin-sensitization tests. In the future, we expect a combination of original and modified h-CLAT to be applied in a newly developed in vitro test for evaluating skin sensitization.

A modified parallel artificial membrane permeability assay for evaluating the bioconcentration of highly hydrophobic chemicals in fish.

PubMed

Kwon, Jung-Hwan; Escher, Beate I

2008-03-01

Low cost in vitro tools are needed at the screening stage of assessment of bioaccumulation potential of new and existing chemicals because the number of chemical substances that needs to be tested highly exceeds the capacity of in vivo bioconcentration tests. Thus, the parallel artificial membrane permeability assay (PAMPA) system was modified to predict passive uptake/ elimination rate in fish. To overcome the difficulties associated with low aqueous solubility and high membrane affinity of highly hydrophobic chemicals, we measured the rate of permeation from the donor poly(dimethylsiloxane)(PDMS) disk to the acceptor PDMS disk through aqueous and PDMS membrane boundary layers and term the modified PAMPA system "PDMS-PAMPA". Twenty chemicals were selected for validation of PDMS-PAMPA. The measured permeability is proportional to the passive elimination rate constant in fish and was used to predict the "minimum" in vivo elimination rate constant. The in vivo data were very close to predicted values except for a few polar chemicals and metabolically active chemicals, such as pyrene and benzo[a]pyrene. Thus, PDMS-PAMPA can be an appropriate in vitro system for nonmetabolizable chemicals. Combination with metabolic clearance rates using a battery of metabolic degradation assays would enhance the applicability for metabolizable chemicals.

Enhanced Cyanate Ester Nanocomposites through Improved Nanoparticle Surface Interactions

DTIC Science & Technology

2013-05-01

and a chemically active 3- aminopropyl surface. The cure behavior and thermal properties of the cyanate ester/modified silica nanocomposites were...area of 150 m 2 /g. Nanoparticles with a chemically active 3- aminopropyl surface were prepared by treating Aerosil 200 particles with 3...however, was visibly observed to severely undercure the nanocomposites with octyl and 3- aminopropyl surface moieties, providing a good initial

Interrogating Protein Phosphatases with Chemical Activity Probes.

PubMed

Casey, Garrett R; Stains, Cliff I

2018-06-04

Protein phosphatases, while long overlooked, have recently become appreciated as drivers of both normal- and disease-associated signaling events. As a result, the spotlight is now turning torwards this enzyme family and efforts geared towards the development of modern chemical tools for studying these enzymes are well underway. This Minireview focuses on the evolution of chemical activity probes, both optical and covalent, for the study of protein phosphatases. Small-molecule probes, global monitoring of phosphatase activity through the use of covalent modifiers, and targeted fluorescence-based activity probes are discussed. We conclude with an overview of open questions in the field and highlight the potential impact of chemical tools for studying protein phosphatases. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Allergenicity, immunogenicity and dose-relationship of three intact allergen vaccines and four allergoid vaccines for subcutaneous grass pollen immunotherapy.

PubMed

Henmar, H; Lund, G; Lund, L; Petersen, A; Würtzen, P A

2008-09-01

Different vaccines containing intact allergens or chemically modified allergoids as active ingredients are commercially available for specific immunotherapy. Allergoids are claimed to have decreased allergenicity without loss of immunogenicity and this is stated to allow administration of high allergoid doses. We compared the allergenicity and immunogenicity of four commercially available chemically modified grass pollen allergoid products with three commercially available intact grass pollen allergen vaccines. The allergenicity was investigated with immunoglobulin (Ig)E-inhibition and basophil activation assays. Human T cell proliferation and specific IgG-titres following mouse immunizations were used to address immunogenicity. Furthermore, intact allergen vaccines with different contents of active ingredients were selected to study the influence of the allergen dose. In general, a lower allergenicity for allergen vaccines was clearly linked to a reduced immunogenicity. Compared with the vaccine with the highest amount of intact allergen, the allergoids caused reduced basophil activation as well as diminished immunogenicity demonstrated by reduced T cell activation and/or reduced induction of murine grass-specific IgG antibodies. Interestingly, intact allergen vaccines with lower content of active ingredient exhibited similarly reduced allergenicity, while immunogenicity was still higher or equal to that of allergoids. The low allergenicity observed for some allergoids was inherently linked to a significantly lower immunogenic response questioning the rationale behind the chemical modification into allergoids. In addition, the linkage between allergenicity, immunogenicity and dose found for intact allergen vaccines and the immunogen as well as allergenic immune responses observed for allergoids suggest that the modified allergen vaccines do not contain high doses of immunologically active ingredients.

Chemical composition and resistance-modifying effect of the essential oil of Lantana camara Linn

PubMed Central

Sousa, Erlânio O.; Silva, Natálya F.; Rodrigues, Fabiola F. G.; Campos, Adriana R.; Lima, Sidney G.; Costa, José Galberto M.

2010-01-01

In this work, the chemical constituents, antibacterial and modulatory activities of the essential oil of Lantana camara Linn were studied. The essential oil was extracted from the leaves of L. camara by hydrodistillation method using Clevenger's apparatus and its chemical constituents were separated and identified by GC-MS, and the relative content of each constituent was determined by area normalization. Among the 25 identified components, bicyclogermacrene (19.42%), isocaryophyllene (16.70%), valecene (12.94%) and germacrene D (12.34%) were the main constituents. The oil was examined to antibacterial and modulatory activities against the multiresistant strains of Escherichia coli and Staphylococcus aureus by microdilution test. The results show an inhibitory activity to E. coli (MIC 512 μg/ml) and S. aureus (MIC 256 μg/ml). The synergism of the essential oil and aminoglycosides was verified too, with significant reduction of MICs (7 ×, 1250-5 μg/ml) against E. coli. It is suggested that the essential oil of Lantana camara Linn could be used as a source of plant-derived natural products with resistance-modifying activity. PMID:20668570

Applications of Graphene-Modified Electrodes in Microbial Fuel Cells

PubMed Central

Yu, Fei; Wang, Chengxian; Ma, Jie

2016-01-01

Graphene-modified materials have captured increasing attention for energy applications due to their superior physical and chemical properties, which can significantly enhance the electricity generation performance of microbial fuel cells (MFC). In this review, several typical synthesis methods of graphene-modified electrodes, such as graphite oxide reduction methods, self-assembly methods, and chemical vapor deposition, are summarized. According to the different functions of the graphene-modified materials in the MFC anode and cathode chambers, a series of design concepts for MFC electrodes are assembled, e.g., enhancing the biocompatibility and improving the extracellular electron transfer efficiency for anode electrodes and increasing the active sites and strengthening the reduction pathway for cathode electrodes. In spite of the challenges of MFC electrodes, graphene-modified electrodes are promising for MFC development to address the reduction in efficiency brought about by organic waste by converting it into electrical energy. PMID:28773929

Enzyme Technology of Peroxidases: Immobilization, Chemical and Genetic Modification

NASA Astrophysics Data System (ADS)

Longoria, Adriana; Tinoco, Raunel; Torres, Eduardo

An overview of enzyme technology applied to peroxidases is made. Immobilization on organic, inorganic, and hybrid supports; chemical modification of amino acids and heme group; and genetic modification by site-directed and random mutagenesis are included. Different strategies that were carried out to improve peroxidase performance in terms of stability, selectivity, and catalytic activity are analyzed. Immobilization of peroxidases on inorganic and organic materials enhances the tolerance of peroxidases toward the conditions normally found in many industrial processes, such as the presence of an organic solvent and high temperature. In addition, it is shown that immobilization helps to increase the Total Turnover Number at levels high enough to justify the use of a peroxidase-based biocatalyst in a synthesis process. Chemical modification of peroxidases produces modified enzymes with higher thermostability and wider substrate variability. Finally, through mutagenesis approaches, it is possible to produce modified peroxidases capable of oxidizing nonnatural substrates with high catalytic activity and affinity.

[Effects of Different Modifier Concentrations on Lead-Zinc Tolerance, Subcellular Distribution and Chemical Forms for Four Kinds of Woody Plants].

PubMed

Chen, Yong-hua; Zhang, Fu-yun; Wu, Xiao-fu; Liang, Xi; Yuan, Si-wen

2015-10-01

Four kinds of lead-zinc tolerant woody plants: Nerium oleander, Koelreuteria paniculata, Paulownia and Boehmeria were used as materials to estimate their enrichment and transferable capacity of lead (Pb) and zinc (Zn) and analyze the subcellular distribution and chemical speciation of Zn and Ph in different parts of plants, under different modifier concentrations (CK group: 100% lead-zinc slag plus a small amount of phosphate fertilizer, improved one: 85% of lead-zinc slag ± 10% peat ± 5% bacterial manure plus a small amount of phosphate fertilizer, improved two: 75% lead-zinc slag ± 20% peat ± 5% bacterial manure ± a small amount of phosphate). Results showed that: (1) The content of Pb, Zn in matrix after planting four kinds of plants was lower than before, no significant difference between improved one and improved two of Nerium oleander and Boehmeria was found, but improved two was better than improved one of Paulownia, while improved one was better than improved two of Koelreuteria paniculata; Four plants had relatively low aboveground enrichment coefficient of Pb and Zn, but had a high transfer coefficient, showed that the appropriate modifier concentration was able to improve the Pb and Zn enrichment and transfer ability of plants. (2) In subcellular distribution, most of Pb and Zn were distributed in plant cell wall components and soluble components while the distribution in cell organelles such as mitochondria, chloroplasts and nucleus component were less. Compared with CK group, two improved group made soluble components of the cell walls of Pb fixation and retention of zinc role in the enhancement. (3) As for the chemical forms of Pb and Zn in plants, the main chemical forms of Pb were hydrochloric acid, sodium chloride and ethanol extractable forms, while other chemical form contents were few, the main chemical forms of Zn were different based on plant type. Compared with CK group, the proportion of the active Pb chemical form in different plant parts decreased in two improved groups, while the proportion of strong activity chemical forms increased; two improved groups led strong activity Zn chemical form of root increased, while strong activity Zn chemical form of aboveground decreased.

Glucose oxidase immobilization on different modified surfaces of platinum nanowire for application in glucose detection

NASA Astrophysics Data System (ADS)

Thanh Tuyen Le, Thi; Duy Tran, Phu; Pham, Xuan Tung; Hien Tong, Duy; Chien Dang, Mau

2010-09-01

In this work, the surface of platinum (Pt) nanowires was modified by using several chemicals, including a compound of gelatin gel with SiO2, polyvinyl alcohol (PVA) with Prussian blue (PB) mediator and cysteamine self-assembled monolayers (SAM). Then, glucose oxidase (GOD) enzyme was immobilized on the modified surfaces of Pt nanowire electrodes by using techniques of electrochemical adsorption and chemical binding. The GOD immobilized Pt nanowires were used for application in glucose detection by performing a cyclic voltammetry measurement. The detection results showed that GOD was immobilized on all of the tested surfaces and the highest glucose detection sensitivity of 60 μM was obtained when the Pt nanowires were modified by PVA with PB mediator. Moreover, the sensors showed very high current response when the Pt nanowires were modified with the cysteamine SAM. The stability and catalyst activity of GOD are also reported here. For instance, the catalyst activity of GOD retained about 60% of its initial value after it was stored at 4 °C in a 100 mM PBS buffer solution with a pH of 7.2 for a period of 30 days.

Modification of chemical reactivity of enzymatic hydrolysis lignin by ultrasound treatment in dilute alkaline solutions.

PubMed

Ma, Zhuoming; Li, Shujun; Fang, Guizhen; Patil, Nikhil; Yan, Ning

2016-12-01

In this study, we have explored various ultrasound treatment conditions for structural modification of enzymatic hydrolysis lignin (EHL) for enhanced chemical reactivity. The key structural modifications were characterized by using a combination of analytical methods, including, Fourier Transform-Infrared spectroscopy (FTIR), Proton Nuclear Magnetic Resonance ( 1 H NMR), Gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS), and Folin-Ciocalteu (F-C) method. Chemical reactivity of the modified EHL samples was determined by both 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity and their reactivity towards formaldehyde. It was observed that the modified EHL had a higher phenolic hydroxyl group content, a lower molecular weight, a higher reactivity towards formaldehyde, and a greater antioxidant property. The higher reactivity demonstrated by the samples after treatment suggesting that ultrasound is a promising method for modifying enzymatic hydrolysis lignin for value-added applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Structural analysis and taste evaluation of γ-glutamyl peptides comprising sulfur-containing amino acids.

PubMed

Amino, Yusuke; Wakabayashi, Hidehiko; Akashi, Satoko; Ishiwatari, Yutaka

2018-03-01

The structures, flavor-modifying effects, and CaSR activities of γ-glutamyl peptides comprising sulfur-containing amino acids were investigated. The chemical structures, including the linkage mode of the N-terminal glutamic acid, of γ-L-glutamyl-S-(2-propenyl)-L-cysteine (γ-L-glutamyl-S-allyl-L-cysteine) and its sulfoxide isolated from garlic were established by comparing their NMR spectra with those of authentic peptides prepared using chemical methods. Mass spectrometric analysis also enabled determination of the linkage modes in the glutamyl dipeptides by their characteristic fragmentation. In sensory evaluation, these peptides exhibited flavor-modifying effects (continuity) in umami solutions less pronounced but similar to that of glutathione. Furthermore, the peptides exhibited intrinsic flavor due to the sulfur-containing structure, which may be partially responsible for their flavor-modifying effects. In CaSR assays, γ-L-glutamyl-S-methyl-L-cysteinylglycine was most active, which indicates that the presence of a medium-sized aliphatic substituent at the second amino acid residue in γ-glutamyl peptides enhances CaSR activity.

Cytotoxicity of ZnO Nanoparticles Can Be Tailored by Modifying Their Surface Structure: A Green Chemistry Approach for Safer Nanomaterials.

PubMed

Punnoose, Alex; Dodge, Kelsey; Rasmussen, John W; Chess, Jordan; Wingett, Denise; Anders, Catherine

2014-07-07

ZnO nanoparticles (NP) are extensively used in numerous nanotechnology applications; however, they also happen to be one of the most toxic nanomaterials. This raises significant environmental and health concerns and calls for the need to develop new synthetic approaches to produce safer ZnO NP, while preserving their attractive optical, electronic, and structural properties. In this work, we demonstrate that the cytotoxicity of ZnO NP can be tailored by modifying their surface-bound chemical groups, while maintaining the core ZnO structure and related properties. Two equally sized (9.26 ± 0.11 nm) ZnO NP samples were synthesized from the same zinc acetate precursor using a forced hydrolysis process, and their surface chemical structures were modified by using different reaction solvents. X-ray diffraction and optical studies showed that the lattice parameters, optical properties, and band gap (3.44 eV) of the two ZnO NP samples were similar. However, FTIR spectroscopy showed significant differences in the surface structures and surface-bound chemical groups. This led to major differences in the zeta potential, hydrodynamic size, photocatalytic rate constant, and more importantly, their cytotoxic effects on Hut-78 cancer cells. The ZnO NP sample with the higher zeta potential and catalytic activity displayed a 1.5-fold stronger cytotoxic effect on cancer cells. These results suggest that by modifying the synthesis parameters/conditions and the surface chemical structures of the nanocrystals, their surface charge density, catalytic activity, and cytotoxicity can be tailored. This provides a green chemistry approach to produce safer ZnO NP.

Determination of specific capacitance of modified candlenut shell based carbon as electrode material for supercapacitor

NASA Astrophysics Data System (ADS)

Zakir, M.; Budi, P.; Raya, I.; Karim, A.; Wulandari, R.; Sobrido, A. B. J.

2018-03-01

Surface modification of candlenut shell carbon (CSC) using three chemicals: nitric acid (HNO3), hydrogen peroxide (H2O2), and sulfuric acid (H2SO4) has been carried out. Activation of CSC was performed using H3PO4 solution with different ratio between CSC and activator. Carbon surface area was determined by methylene blue adsorption method. Surface characterization was performed using FTIR spectroscopy and Boehm titration method. Specific capacitance of electrode prepared from CSAC (candlenuts shell activated carbon) materials was quantified by Cyclic Voltammetry (CV) measurement. The surface area before and after activation are 105,127 m2/g, 112,488 m2/g, 124,190 m2/g, and 135,167 m2/g, respectively. Surface modification of CSAC showed the improvement in the chemical functionality of CSAC surface. Analyses using FTIR spectroscopy and Boehm titration showed that modifications with HNO3, H2SO4 and H2O2 on the surface of the CSAC increased the number of oxygen functional groups. As a consequence, the specific capacitance of CSAC modified with 65% HNO3 attained the highest value (127 μF/g). There is an incredible increase by a factor of 298% from electrode which was constructed with un-modified CSAC material. This increase correlates to the largest number of oxygen functional groups of CSAC modified with nitric acid (HNO3).

Allergenicity, immunogenicity and dose-relationship of three intact allergen vaccines and four allergoid vaccines for subcutaneous grass pollen immunotherapy

PubMed Central

Henmar, H; Lund, G; Lund, L; Petersen, A; Würtzen, P A

2008-01-01

Different vaccines containing intact allergens or chemically modified allergoids as active ingredients are commercially available for specific immunotherapy. Allergoids are claimed to have decreased allergenicity without loss of immunogenicity and this is stated to allow administration of high allergoid doses. We compared the allergenicity and immunogenicity of four commercially available chemically modified grass pollen allergoid products with three commercially available intact grass pollen allergen vaccines. The allergenicity was investigated with immunoglobulin (Ig)E-inhibition and basophil activation assays. Human T cell proliferation and specific IgG-titres following mouse immunizations were used to address immunogenicity. Furthermore, intact allergen vaccines with different contents of active ingredients were selected to study the influence of the allergen dose. In general, a lower allergenicity for allergen vaccines was clearly linked to a reduced immunogenicity. Compared with the vaccine with the highest amount of intact allergen, the allergoids caused reduced basophil activation as well as diminished immunogenicity demonstrated by reduced T cell activation and/or reduced induction of murine grass-specific IgG antibodies. Interestingly, intact allergen vaccines with lower content of active ingredient exhibited similarly reduced allergenicity, while immunogenicity was still higher or equal to that of allergoids. The low allergenicity observed for some allergoids was inherently linked to a significantly lower immunogenic response questioning the rationale behind the chemical modification into allergoids. In addition, the linkage between allergenicity, immunogenicity and dose found for intact allergen vaccines and the immunogen as well as allergenic immune responses observed for allergoids suggest that the modified allergen vaccines do not contain high doses of immunologically active ingredients. PMID:18647321

Separations and characterizations of fractions from Mayan, Heavy Arabian, and Hondo crude oils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kircher, C.C.

1991-01-01

This paper reports on Mayan, Heavy Arabian, and Hondo crude oil resids separated with a modified, extended ASTM D2007 procedure. The fractions obtained have been characterized with various analytical techniques. Chemical properties, hydrodesulfurization, and hydrodemetallation activities of the resids have been correlated with the chemical properties of the separated fractions. Many correlations were indicative of the overall bulk properties of the resids and the broad chemical classes obtained from the separation schemes. Other correlations reflected the unique chemical nature of each crude oil resid. Some potentially important correlations were found between hydrodesulfurization activity and sulfur concentration in polars and asphaltenes,more » and between hydrodemetallation activity and nitrogen concentration in the acid and bases fractions.« less

Activated Carbon Modified with Copper for Adsorption of Propanethiol

PubMed Central

Moreno-Piraján, Juan Carlos; Tirano, Joaquín; Salamanca, Brisa; Giraldo, Liliana

2010-01-01

Activated carbons were characterized texturally and chemically before and after treatment, using surface area determination in the BET model, Boehm titration, TPR, DRX and immersion calorimetry. The adsorption capacity and the kinetics of sulphur compound removal were determined by gas chromatography. It was established that the propanethiol retention capacity is dependent on the number of oxygenated groups generated on the activated carbon surface and that activated carbon modified with CuO at 0.25 M shows the highest retention of propanethiol. Additionally is proposed a mechanism of decomposition of propenothiol with carbon-copper system. PMID:20479992

Photocatalytic activity and antimicrobial properties of paper sheets modified with TiO2/Sodium alginate nanocomposites.

PubMed

Abdel Rehim, Mona H; El-Samahy, Magda A; Badawy, Abdelrahman A; Mohram, Maysa E

2016-09-05

Photocatalytic paper sheets were prepared by addition of different ratios of TiO2/Sodium alginate (TSA) nanocomposite. The modified paper sheets were characterized by XRD, TGA. Their morphology was studied by scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Photocatalytic activity of modified paper has been studied by analysis of chemical oxygen demand (COD) of waste-water. The results confirmed the mineralization of the waste-water and enhanced removal of chemical oxygen demand (COD) by increasing the amount of photocatalyst in the paper. Moreover, the results also confirmed that presence of sodium alginate as biopolymer increased adhesion of nanoparticles to paper fibers and reduced the harmful effect of the photocatalyst on them. The paper sheets containing 7% as well as 15% TSA showed high photocatalytic activity and anti-bacterial effect against Salmonella typhimurium higher than standard antibiotic beside other microorganisms such as Candida albicans. The maximum antimicrobial effect was found in case of specimen loaded with 15% TSA. Moreover, it was found that by adding 20% TSA to the paper matrix, the properties of the paper composite collapse. The obtained results confirm the possible utilization of the modified paper in both hygienic and food packaging applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Investigation of oxygen reduction and methanol oxidation reaction activity of PtAu nano-alloy on surface modified porous hybrid nanocarbon supports

NASA Astrophysics Data System (ADS)

Parambath Vinayan, Bhaghavathi; Nagar, Rupali; Ramaprabhu, Sundara

2016-09-01

We investigate the electrocatalytic activity of PtAu alloy nanoparticles supported on various chemically modified carbon morphologies towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). The surface-modification of graphene nanosheets (f-G), multi-walled carbon nanotubes (f-MWNTs) and (graphene nanosheets-carbon nanotubes) hybrid support (f-G-MWNTs) were carried out by soft functionalization method using a cationic polyelectrolyte poly-(diallyldimethyl ammonium chloride). The Pt and PtAu alloy nanoparticles were dispersed over chemically modified carbon supports by sodium-borohydride assisted modified polyol reduction method. The electrochemical performance of all electrocatalysts were studied by half- and full-cell proton exchange membrane fuel cell (PEMFC) measurements and PtAu/f-G-MWNTs catalyst comparatively yielded the best catalytic performance. PEMFC full cell measurements of PtAu/f-G-MWNTs cathode electrocatalyst yield a maximum power density of 319 mW cm-2 at 60 °C without any back pressure,which is 2.1 times higher than that of cathode electrocatalyst Pt on graphene support. The high ORR and MOR activity of PtAu/f-G-MWNTs electrocatalyst is due to the alloying effect and inherent beneficial properties of porous hybrid nanocarbon support.

IMPORTANCE OF ACTIVATED CARBON'S OXYGEN SURFACE FUNCTIONAL GROUPS ON ELEMENTAL MERCURY ADSORPTION

EPA Science Inventory

The effect of varying physical and chemical properties of activated carbons on adsorption of elemental mercury [Hg(0)] was studied by treating two activated carbons to modify their surface functional groups and pore structures. Heat treatment (1200 K) in nitrogen (N2), air oxidat...

Chemically Modified Polyvinyl Chloride for Removal of Thionine Dye (Lauth’s Violet)

PubMed Central

Silva, Cleuzilene V.; Royer, Betina; Rodrigues Filho, Guimes; Cerqueira, Daniel A.; Assunção, Rosana M. N.

2017-01-01

The chemical modification of hydrophobic polymer matrices is an alternative way to elchange their surface properties. The introduction of sulfonic groups in the polymer changes the surface properties such as adhesion, wettability, catalytic ability, and adsorption capacity. This work describes the production and application of chemically modified polyvinyl chloride (PVC) as adsorbent for dyes removal. Chemical modification of PVC was evaluated by infrared spectroscopy and elemental analysis, which indicated the presence of sulfonic groups on PVC. The chemically modified PVC (PVCDS) showed an ion exchange capacity of 1.03 mmol−1, and efficiently removed the thionine dye (Lauth’s violet) from aqueous solutions, reaching equilibrium in 30 min. The adsorption kinetics was better adjusted for a pseudo second order model. This result indicates that the adsorption of thionine onto PVCDS occurs by chemisorption. Among the models for the state of equilibrium, SIPS and Langmuir exhibited the best fit to the experimental results and PVCDS showed high adsorption capacities (370 mg−1). Thus, it is assumed that the system presents homogeneous characteristics to the distribution of active sites. The modification promoted the formation of surface characteristics favorable to the dye adsorption by the polymer. PMID:29137158

Neuronal apoptotic signaling pathways probed and intervened by synthetically and modularly modified (SMM) chemokines.

PubMed

Choi, Won-Tak; Kaul, Marcus; Kumar, Santosh; Wang, Jun; Kumar, I M Krishna; Dong, Chang-Zhi; An, Jing; Lipton, Stuart A; Huang, Ziwei

2007-03-09

As the main coreceptors for human immunodeficiency virus type 1 (HIV-1) entry, CXCR4 and CCR5 play important roles in HIV-associated dementia (HAD). HIV-1 glycoprotein gp120 contributes to HAD by causing neuronal damage and death, either directly by triggering apoptotic pathways or indirectly by stimulating glial cells to release neurotoxins. Here, to understand the mechanism of CXCR4 or CCR5 signaling in neuronal apoptosis associated with HAD, we have applied synthetically and modularly modified (SMM)-chemokine analogs derived from natural stromal cell-derived factor-1alpha or viral macrophage inflammatory protein-II as chemical probes of the mechanism(s) whereby these SMM-chemokines prevent or promote neuronal apoptosis. We show that inherently neurotoxic natural ligands of CXCR4, such as stromal cell-derived factor-1alpha or viral macrophage inflammatory protein-II, can be modified to protect neurons from apoptosis induced by CXCR4-preferring gp120(IIIB), and that the inhibition of CCR5 by antagonist SMM-chemokines, unlike neuroprotective CCR5 natural ligands, leads to neurotoxicity by activating a p38 mitogen-activated protein kinase (MAPK)-dependent pathway. Furthermore, we discover distinct signaling pathways activated by different chemokine ligands that are either natural agonists or synthetic antagonists, thus demonstrating a chemical biology strategy of using chemically engineered inhibitors of chemokine receptors to study the signaling mechanism of neuronal apoptosis and survival.

Characterization of a sustainable sulfur polymer concrete using activated fillers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moon, Juhyuk; Kalb, Paul D.; Milian, Laurence

Sulfur polymer concrete (SPC) is a thermoplastic composite concrete consisting of chemically modified sulfur polymer and aggregates. This study focused on the characterization of a new SPC that has been developed as a sustainable construction material. It is made from industrial by-product sulfur that is modified with activated fillers of fly ash, petroleum refinery residual oil, and sand. Unlike conventional sulfur polymer cements made using dicyclopentadiene as a chemical modifier, the use of inexpensive industrial by-products enables the new SPC to cost-effectively produce sustainable, low-carbon, thermoplastic binder that can compete with conventional hydraulic cement concretes. A series of characterization analysesmore » was conducted including thermal analysis, X-ray diffraction, and spatially-resolved Xray absorption spectroscopy to confirm the polymerization of sulfur induced from the presence of the oil. In addition, mechanical testing, internal pore structure analysis, and scanning electron microscope studies evaluate the performance of this new SPC as a sustainable construction material with a reduced environmental impact.« less

Characterization of a sustainable sulfur polymer concrete using activated fillers

DOE PAGES

Moon, Juhyuk; Kalb, Paul D.; Milian, Laurence; ...

2016-01-02

Sulfur polymer concrete (SPC) is a thermoplastic composite concrete consisting of chemically modified sulfur polymer and aggregates. This study focused on the characterization of a new SPC that has been developed as a sustainable construction material. It is made from industrial by-product sulfur that is modified with activated fillers of fly ash, petroleum refinery residual oil, and sand. Unlike conventional sulfur polymer cements made using dicyclopentadiene as a chemical modifier, the use of inexpensive industrial by-products enables the new SPC to cost-effectively produce sustainable, low-carbon, thermoplastic binder that can compete with conventional hydraulic cement concretes. A series of characterization analysesmore » was conducted including thermal analysis, X-ray diffraction, and spatially-resolved Xray absorption spectroscopy to confirm the polymerization of sulfur induced from the presence of the oil. In addition, mechanical testing, internal pore structure analysis, and scanning electron microscope studies evaluate the performance of this new SPC as a sustainable construction material with a reduced environmental impact.« less

Rhodium(II) metallopeptide catalyst design enables fine control in selective functionalization of natural SH3 domains.

PubMed

Vohidov, Farrukh; Coughlin, Jane M; Ball, Zachary T

2015-04-07

Chemically modified proteins are increasingly important for use in fundamental biophysical studies, chemical biology, therapeutic protein development, and biomaterials. However, chemical methods typically produce heterogeneous labeling and cannot approach the exquisite selectivity of enzymatic reactions. While bioengineered methods are sometimes an option, selective reactions of natural proteins remain an unsolved problem. Here we show that rhodium(II) metallopeptides combine molecular recognition with promiscuous catalytic activity to allow covalent decoration of natural SH3 domains, depending on choice of catalyst but independent of the specific residue present. A metallopeptide catalyst succeeds in modifying a single SH3-containing kinase at endogenous concentrations in prostate cancer (PC-3) cell lysate. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

129Xe nuclear magnetic resonance study of pitch-based activated carbon modified by air oxidation/pyrolysis cycles: a new approach to probe the micropore size.

PubMed

Romanenko, Konstantin V; Py, Xavier; d'Espinose de Lacaillerie, Jean-Baptiste; Lapina, Olga B; Fraissard, Jacques

2006-02-23

(129)Xe NMR has been used to study a series of homologous activated carbons obtained from a KOH-activated pitch-based carbon molecular sieve modified by air oxidation/pyrolysis cycles. A clear correlation between the pore size of microporous carbons and the (129)Xe NMR of adsorbed xenon is proposed for the first time. The virial coefficient delta(Xe)(-)(Xe) arising from binary xenon collisions varied linearly with the micropore size and appeared to be a better probe of the microporosity than the chemical shift extrapolated to zero pressure. This correlation was explained by the fact that the xenon collision frequency increases with increasing micropore size. The chemical shift has been shown to vary very little with temperature (less than 9 ppm) for xenon trapped inside narrow and wide micropores. This is indicative of a smooth xenon-surface interaction potential.

N(epsilon)-carboxymethyllysine-modified proteins are unable to bind to RAGE and activate an inflammatory response.

PubMed

Buetler, Timo M; Leclerc, Estelle; Baumeyer, Alexandra; Latado, Helia; Newell, John; Adolfsson, Oskar; Parisod, Véronique; Richoz, Janique; Maurer, Sarah; Foata, Francis; Piguet, Dominique; Junod, Sylviane; Heizmann, Claus W; Delatour, Thierry

2008-03-01

Advanced glycation endproducts (AGEs) containing carboxymethyllysine (CML) modifications are generally thought to be ligands of the receptor for AGEs, RAGEs. It has been argued that this results in the activation of pro-inflammatory pathways and diseases. However, it has not been shown conclusively that a CML-modified protein can interact directly with RAGE. Here, we have analyzed whether beta-lactoglobulin (bLG) or human serum albumin (HSA) modified chemically to contain only CML (10-40% lysine modification) can (i) interact with RAGE in vitro and (ii) interact with and activate RAGE in lung epithelial cells. Our results show that CML-modified bLG or HSA are unable to bind to RAGE in a cell-free assay system (Biacore). Furthermore, they are unable to activate pro-inflammatory signaling in the cellular system. Thus, CML probably does not form the necessary structure(s) to interact with RAGE and activate an inflammatory signaling cascade in RAGE-expressing cells.

In Silico and In Vitro Anticancer Activity of Isolated Novel Marker Compound from Chemically Modified Bioactive Fraction from Curcuma longa (NCCL).

PubMed

Naqvi, Arshi; Malasoni, Richa; Gupta, Swati; Srivastava, Akansha; Pandey, Rishi R; Dwivedi, Anil Kumar

2017-10-01

Turmeric ( Curcuma longa ) is reported to possess wide array of biological activities. Herbal Medicament (HM) is a standardized hexane-soluble fraction of C. longa and is well known for its neuroprotective effect. In this study, we attempted to synthesize a novel chemically modified bioactive fraction from HM (NCCL) along with isolation and characterization of a novel marker compound (I). NCCL was prepared from HM. The chemical structure of the marker compound isolated from NCCL was determined from 1D/2D nuclear magnetic resonance, mass spectroscopy, and Fourier transform infrared. The compound so isolated was subjected to in silico and in vitro screenings to test its inhibitory effect on estrogen receptors. Molecular docking studies revealed that the binding poses of the compound I was energetically favorable. Among NCCL and compound I taken for in vitro studies, NCCL had exhibited good anti-cancer activity over compound I against MCF-7, MDA-MB-231, DU-145, and PC-3 cells. This is the first study about the synthesis of a chemically modified bioactive fraction which used a standardized extract since the preparation of the HM. It may be concluded that NCCL fraction having residual components induce more cell death than compound I alone. Thus, NCCL may be used as a potent therapeutic drug. In the present paper, a standardized hexane soluble fraction of Curcuma longa (HM) was chemically modified to give a novel bioactive fraction (NCCL). A novel marker compound was isolated from NCCL and was characerized using various spectral techniques. The compound so isolated was investigated for in-silico screenings. NCCL and isolated compound was subjected to in-vitro anti-cancer screenings against MCF 7, MDA MB 231 (breast adenocarcinoma) and DU 145 and PC 3 cell lines (androgen independent human prostate cancer cells). The virtual screenings reveals that isolated compound has shown favourable drug like properties. NCCL fraction having residual components induces more cell death in these four cancer cell lines than isolated compound alone. Abbreviations used: HM: Herbal Medicament; NCCL: Chemically modified HM; FT-IR: Fourier transform-infrared spectroscopy; NMR: Nuclear magnetic resonance spectroscopy; MS: Mass spectroscopy; HPLC: High-performance liquid chromatography; ER: Estrogen receptor; MTT: 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; MIC: Minimum inhibitory concentration; TAM: Tamoxifen KBr: Potassium bromide; DMSO: Dimethyl sulfoxide; ACN: Acetonitrile; PDB: Protein Data Bank; PDA: Photodiode array detector.

Apparatus for rapid measurement of aerosol bulk chemical composition

DOEpatents

Lee, Yin-Nan E.; Weber, Rodney J.

2003-01-01

An apparatus and method for continuous on-line measurement of chemical composition of aerosol particles with a fast time resolution are provided. The apparatus includes a modified particle size magnifier for producing activated aerosol particles and a collection device which collects the activated aerosol particles into a liquid stream for quantitative analysis by analytical methods. The method provided for on-line measurement of chemical composition of aerosol particles includes exposing aerosol carrying sample air to hot saturated steam thereby forming activated aerosol particles; collecting the activated aerosol particles by a collection device for delivery as a jet stream onto an impaction surface; flushing off the activated aerosol particles from the impaction surface into a liquid stream for delivery of the collected liquid stream to an analytical instrument for quantitative measurement.

Catalytic activity of platinum on ruthenium electrodes with modified (electro)chemical states.

PubMed

Park, Kyung-Won; Sung, Yung-Eun

2005-07-21

Using Pt on Ru thin-film electrodes with various (electro)chemical states designed by the sputtering method, the effect of Ru states on the catalytic activity of Pt was investigated. The chemical and electrochemical properties of Pt/Ru thin-film samples were confirmed by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. In addition, Pt nanoparticles on Ru metal or oxide for an actual fuel cell system showed an effect of Ru states on the catalytic activity of Pt in methanol electrooxidation. Finally, it was concluded that such an enhancement of methanol electrooxidation on the Pt is responsible for Ru metallic and/or oxidation sites compared to pure Pt without any Ru state.

Cytotoxicity of ZnO Nanoparticles Can Be Tailored by Modifying Their Surface Structure: A Green Chemistry Approach for Safer Nanomaterials

PubMed Central

2015-01-01

ZnO nanoparticles (NP) are extensively used in numerous nanotechnology applications; however, they also happen to be one of the most toxic nanomaterials. This raises significant environmental and health concerns and calls for the need to develop new synthetic approaches to produce safer ZnO NP, while preserving their attractive optical, electronic, and structural properties. In this work, we demonstrate that the cytotoxicity of ZnO NP can be tailored by modifying their surface-bound chemical groups, while maintaining the core ZnO structure and related properties. Two equally sized (9.26 ± 0.11 nm) ZnO NP samples were synthesized from the same zinc acetate precursor using a forced hydrolysis process, and their surface chemical structures were modified by using different reaction solvents. X-ray diffraction and optical studies showed that the lattice parameters, optical properties, and band gap (3.44 eV) of the two ZnO NP samples were similar. However, FTIR spectroscopy showed significant differences in the surface structures and surface-bound chemical groups. This led to major differences in the zeta potential, hydrodynamic size, photocatalytic rate constant, and more importantly, their cytotoxic effects on Hut-78 cancer cells. The ZnO NP sample with the higher zeta potential and catalytic activity displayed a 1.5-fold stronger cytotoxic effect on cancer cells. These results suggest that by modifying the synthesis parameters/conditions and the surface chemical structures of the nanocrystals, their surface charge density, catalytic activity, and cytotoxicity can be tailored. This provides a green chemistry approach to produce safer ZnO NP. PMID:25068096

Adhesion mapping of chemically modified and poly(ethylene oxide)-grafted glass surfaces.

PubMed

Jogikalmath, G; Stuart, J K; Pungor, A; Hlady, V

1999-08-01

Two-dimensional mapping of the adhesion pull-off forces was used to study the origin of surface heterogeneity in the grafted poly(ethylene oxide) (PEO) layer. The variance of the pull-off forces measured over the μm-sized regions after each chemical step of modifying glass surfaces was taken to be a measure of the surface chemical heterogeneity. The attachment of γ-glycidoxypropyltrimethoxy silane (GPS) to glass decreased the pull-off forces relative to the clean glass and made the surface more uniform. The subsequent hydrolysis of the terminal epoxide groups resulted in a larger surface heterogeneity which was modeled by two populations of the terminal hydroxyl groups, each with its own distribution of adhesion forces and force variance. The activation of the hydroxyls with carbonyldiimmidazole (CDI) healed the surface and lowered its adhesion, however, the force variance remained rather large. Finally, the grafting of the α,ω-diamino poly(ethyleneoxide) chains to the CDI-activated glass largely eliminated adhesion except at a few discrete regions. The adhesion on the PEO grafted layer followed the Poisson distribution of the pull-off forces. With the exception of the glass surface, a correlation between the water contact angles and the mean pull-off forces measured with the Si(3)N(4) tip surfaces was found for all modified glass surfaces.

77 FR 9237 - Agency Information Collection Activities; Proposed Collection; Comment Request; Risk Management...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-16

... Activities; Proposed Collection; Comment Request; Risk Management Program Requirements and Petitions To..., non-chemical manufacturers, etc. Title: Risk Management Program Requirements and Petitions to Modify... regulated substance in a process develop and implement a risk management program and submit a risk...

Activity, Stability, and Structure of Native and Modified by Woodward Reagent K Mushroom Tyrosinase

NASA Astrophysics Data System (ADS)

Emami, S.; Piri, H.; Gheibi, N.

2018-01-01

Mushroom tyrosinase (MT) was considered a good model for studying the inhibition, activation, and mutation of tyrosinase as the key enzyme of melanogenesis. In the present study, the activity, structure, reduction, and stability of native and modified enzymes were investigated after the modification of MT carboxylic residues by the Woodward reagent K (WRK). The relative activity of the sole enzyme was reduced from 100 to 77.9, 53.8, 39.4, and 26.4% after its modification by 2.5, 5, 25, and 50 ratios of [WRK]/[MT], respectively. The Tm values were calculated from thermal denaturation curves at 61.2, 60.1, 58.3, 53.9, and 45.5oC for the sole and modified enzymes. The reduction of the Δ {G}_{{H}_2O} values for the modified enzyme in chemical denaturation indicated instability. A structural study by CD and intrinsic fluorescence technique revealed the fluctuation of the secondary and tertiary structures of MT.

Effect of alkali and oxidative treatments on the physicochemical, pasting, thermal and morphological properties of corn starch.

PubMed

Spier, Franciela; Zavareze, Elessandra da Rosa; Marques e Silva, Ricardo; Elias, Moacir Cardoso; Dias, Alvaro Renato Guerra

2013-07-01

Few studies on starch modifications using different chemical agents are available in the literature, and no reports were found on the combined effect of oxidation and alkaline treatment of corn starch. Thus this work evaluated the physicochemical, pasting, morphological, cystallinity and thermal properties of chemically modified corn starch, after either the isolated or combined action of alkaline (sodium hydroxide) and oxidative (sodium hypochlorite) treatments. The highest values for the sum of carbonyl and carboxyl and enzymatic hydrolysis occurred in starches submitted to oxidative treatment at high active chlorine concentrations. The alkali treatment in isolation modified the pasting properties, reduced the paste temperature and increased the peak viscosity, breakdown, final viscosity and setback of starches. Starch modified by the action of sodium hypochlorite and hydroxide in combination presented more severe damage on granule surfaces. The results show that corn starch modified by the combined action of oxidative and alkaline treatments should be studied more, especially at the concentration limit of sodium hydroxide where gelatinization occurs. Under these conditions the effect of oxidation can be more intense and thus allow the production of starches with different properties and an increase in their industrial applications. © 2013 Society of Chemical Industry.

40 CFR 721.6498 - Modified polyisocyanates (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6498 Modified polyisocyanates (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as modified polyisocyanates (PMN P...

40 CFR 721.6498 - Modified polyisocyanates (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6498 Modified polyisocyanates (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as modified polyisocyanates (PMN P...

40 CFR 721.6498 - Modified polyisocyanates (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6498 Modified polyisocyanates (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as modified polyisocyanates (PMN P...

A multifunctional polymeric nanofilm with robust chemical performances for special wettability.

PubMed

Wang, Yabin; Lin, Feng; Dong, Yaping; Liu, Zhong; Li, Wu; Huang, Yudong

2016-03-07

A multifunctional polymeric nanofilm of a triazinedithiolsilane compound, which can protect metallic substrates and activate the corresponding surface simultaneously, is introduced onto a copper mesh surface via facile solution-immersion approaches. The resultant interface exhibits hydrophilic features due to the existence of silanol groups (SiOH) outward and has the potential to act as a superhydrophilic and underwater superoleophobic material. As the polymeric nanofilm atop the copper mesh is modified with long-chain octadecyltrichlorosilane (OTS), the functionalized surface becomes superhydrophobic and superoleophilic. The OTS-modified polymeric nanofilm shows outstanding chemical durability and stability that are seldom concurrently satisfied for a material with special wettability, owing to its inherent architecture. These textures generate high separation efficiency, durable separation capability and excellent thermal stability. The protective ability, originating from the textures of the underlying cross-linked disulfide units (-SS-) and siloxane networks (SiOSi) on the top of the nanofilm, prolongs the chemical durability. The activating capability stemming from the residual SiOH groups improves the chemical stability as a result of the chemical bonds developed by these sites. The significant point of this investigation lies in enlightening us on the fabrication of multifunctional polymeric nanofilms on different metal surfaces using various triazinedithiolsilane compounds, and on the construction of interfaces with controllable wettable performances in demanding research or industrial applications.

Chemical Modification of Cyclodextrin and Amylose by Click Reaction and Its Application to the Synthesis of Poly-alkylamine-Modified Antibacterial Sugars.

PubMed

Yamamura, Hatsuo

2017-01-01

Cyclodextrin (CD) can be chemically modified into desired and sophisticated functional molecules. However, poly-modification often produces complicated mixtures, resulting in a low yield of the desired product. As the most promising procedure to solve such problems and to achieve poly-modification of the CD molecule, we present here the Huisgen 1,3-dipolar cycloaddition, known as a click reaction. This review will describe the results of our microwave-assisted click reaction for the poly-modification of CD and amylose molecules, and its application to the study of synthetic membrane active antibacterial derivatives.

Water Pollution

ERIC Educational Resources Information Center

Bowen, H. J. M.

1975-01-01

Deals with water pollution in the following categories: a global view, self purification, local pollution, difficulties in chemical analysis, and remedies for water pollution. Emphasizes the extent to which man's activities have modified the cycles of certain elements. (GS)

Chemical Modification of Papain and Subtilisin: An Active Site Comparison

ERIC Educational Resources Information Center

St-Vincent, Mireille; Dickman, Michael

2004-01-01

An experiment using methyle methanethiosulfonate (MMTS) and phenylmethylsulfonyl flouride (PMSF) to specifically modify the cysteine and serine residues in the active sites of papain and subtilism respectively is demonstrated. The covalent modification of these enzymes and subsequent rescue of papain shows the beginning biochemist that proteins…

Methods for immobilizing nucleic acids on a gel substrate

DOEpatents

Mirzabekov, Andrei Darievich; Proudnikov, Dimitri Y.; Timofeev, Edward N.; Kochetkova, Svetlana V.; Florentiev, Vladimir L.; Shick, Valentine V.

1999-01-01

A method for labeling oligonucleotide molecules, and for immobilizing oligonucleotide and DNA molecules is provided comprising modifying the molecules to create a chemically active group, and contacting activated fluorescent dyes to the region. A method for preparing an immobilization substrate is also provided comprising modifying a gel to contain desired functional groups which covalently interact with certain moieties of the oligonucleotide molecules. A method for immobilizing biomolecules and other molecules within a gel by copolymerization of allyl-substituted oligonucleotides, DNA and proteins with acrylamide is also provided.

Recent Progress on Cellulose-Based Electro-Active Paper, Its Hybrid Nanocomposites and Applications

PubMed Central

Khan, Asif; Abas, Zafar; Kim, Heung Soo; Kim, Jaehwan

2016-01-01

We report on the recent progress and development of research into cellulose-based electro-active paper for bending actuators, bioelectronics devices, and electromechanical transducers. The cellulose electro-active paper is characterized in terms of its biodegradability, chirality, ample chemically modifying capacity, light weight, actuation capability, and ability to form hybrid nanocomposites. The mechanical, electrical, and chemical characterizations of the cellulose-based electro-active paper and its hybrid composites such as blends or coatings with synthetic polymers, biopolymers, carbon nanotubes, chitosan, and metal oxides, are explained. In addition, the integration of cellulose electro-active paper is highlighted to form various functional devices including but not limited to bending actuators, flexible speaker, strain sensors, energy harvesting transducers, biosensors, chemical sensors and transistors for electronic applications. The frontiers in cellulose paper devices are reviewed together with the strategies and perspectives of cellulose electro-active paper and cellulose nanocomposite research and applications. PMID:27472335

Recent Progress on Cellulose-Based Electro-Active Paper, Its Hybrid Nanocomposites and Applications.

PubMed

Khan, Asif; Abas, Zafar; Kim, Heung Soo; Kim, Jaehwan

2016-07-26

We report on the recent progress and development of research into cellulose-based electro-active paper for bending actuators, bioelectronics devices, and electromechanical transducers. The cellulose electro-active paper is characterized in terms of its biodegradability, chirality, ample chemically modifying capacity, light weight, actuation capability, and ability to form hybrid nanocomposites. The mechanical, electrical, and chemical characterizations of the cellulose-based electro-active paper and its hybrid composites such as blends or coatings with synthetic polymers, biopolymers, carbon nanotubes, chitosan, and metal oxides, are explained. In addition, the integration of cellulose electro-active paper is highlighted to form various functional devices including but not limited to bending actuators, flexible speaker, strain sensors, energy harvesting transducers, biosensors, chemical sensors and transistors for electronic applications. The frontiers in cellulose paper devices are reviewed together with the strategies and perspectives of cellulose electro-active paper and cellulose nanocomposite research and applications.

Chemical vapor deposition: Stable carbons from low-rank coals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, R.K.; Kulas, R.W.; Olson, E.S.

1996-12-31

A chemical vapor deposition (CVD) technique has been used to increase the oxidative stability of activated carbons. Activated carbons prepared from Gascoyne lignite (North Dakota) by thermal or potassium hydroxide activations were subjected to BCI, in helium at 727{degrees}C with or without benzene for a limited period of time, followed by annealing in helium at 900{degrees}C for three days. Untreated and acid-washed coal samples were used to assess the magnitude of the effect of mineral matter in the coal on the boron coating. The oxidative stability of the boron-modified carbons was determined from the decomposition curves obtained from the thermogravimetricmore » analysis. Modification of the as-received, KOH-treated carbon yielded oxidatively stable carbons up to an initial temperature of 520{degrees}C, compared to about 350{degrees}C for the starting material. Similar results were obtained for the carbonized Gascoyne lignite. Sulfurous acid washing of the Gascoyne significantly enhanced the thermal stability (600{degrees}C) of the boron-modified carbon.« less

Mold Pectinase Modified with Dialdehyde Derivatives of Dextran and Cellulose.

PubMed

Kobayashi, M; Chiba, Y; Funane, K; Ohya, S; Kato, Y

1996-01-01

Chemical modification of mold pectinase with dextran- and cellulose-dialdehydes was examined to improve the enzyme characteristics. The modified pectinase with dextran-dialdehyde retained about 50% of the original activity, and more than 80% of the total amino groups were modified. HPLC gel filtration analysis showed an increase in molecular weight of the reaction product. Reaction with cellulose-dialdehyde provided an immobilized form of pectinase. The immobilized pectinase was resistant to both acidic and alkaline pHs, and also acquired heat stability at 60°C. The optimum pH of the modified enzyme shifted from pH 4.5 to 5.0-5.5, and this enzyme had higher activity at neutral pH regions than the native enzyme. A rather low recovery of immobilized enzyme (14.5%) should be improved by the combination with various methods hitherto established.

Relation between the adsorbed quantity and the immersion enthalpy in catechol aqueous solutions on activated carbons.

PubMed

Moreno-Piraján, Juan Carlos; Blanco, Diego; Giraldo, Liliana

2012-01-01

An activated carbon, Carbochem(TM)-PS230, was modified by chemical and thermal treatment in flow of H(2), in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pK(a). The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG), the immersion enthalpies obtained are between 21.5 and 45.7 J·g(-1) for catechol aqueous solutions in a range of 20 at 1500 mg·L(-1).

Relation Between the Adsorbed Quantity and the Immersion Enthalpy in Catechol Aqueous Solutions on Activated Carbons

PubMed Central

Moreno-Piraján, Juan Carlos; Blanco, Diego; Giraldo, Liliana

2012-01-01

An activated carbon, CarbochemTM—PS230, was modified by chemical and thermal treatment in flow of H2, in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pKa. The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG), the immersion enthalpies obtained are between 21.5 and 45.7 J·g−1 for catechol aqueous solutions in a range of 20 at 1500 mg·L−1. PMID:22312237

Destruction of chemical warfare agents using metal-organic frameworks

NASA Astrophysics Data System (ADS)

Mondloch, Joseph E.; Katz, Michael J.; Isley, William C., III; Ghosh, Pritha; Liao, Peilin; Bury, Wojciech; Wagner, George W.; Hall, Morgan G.; Decoste, Jared B.; Peterson, Gregory W.; Snurr, Randall Q.; Cramer, Christopher J.; Hupp, Joseph T.; Farha, Omar K.

2015-05-01

Chemical warfare agents containing phosphonate ester bonds are among the most toxic chemicals known to mankind. Recent global military events, such as the conflict and disarmament in Syria, have brought into focus the need to find effective strategies for the rapid destruction of these banned chemicals. Solutions are needed for immediate personal protection (for example, the filtration and catalytic destruction of airborne versions of agents), bulk destruction of chemical weapon stockpiles, protection (via coating) of clothing, equipment and buildings, and containment of agent spills. Solid heterogeneous materials such as modified activated carbon or metal oxides exhibit many desirable characteristics for the destruction of chemical warfare agents. However, low sorptive capacities, low effective active site loadings, deactivation of the active site, slow degradation kinetics, and/or a lack of tailorability offer significant room for improvement in these materials. Here, we report a carefully chosen metal-organic framework (MOF) material featuring high porosity and exceptional chemical stability that is extraordinarily effective for the degradation of nerve agents and their simulants. Experimental and computational evidence points to Lewis-acidic ZrIV ions as the active sites and to their superb accessibility as a defining element of their efficacy.

Destruction of chemical warfare agents using metal-organic frameworks.

PubMed

Mondloch, Joseph E; Katz, Michael J; Isley, William C; Ghosh, Pritha; Liao, Peilin; Bury, Wojciech; Wagner, George W; Hall, Morgan G; DeCoste, Jared B; Peterson, Gregory W; Snurr, Randall Q; Cramer, Christopher J; Hupp, Joseph T; Farha, Omar K

2015-05-01

Chemical warfare agents containing phosphonate ester bonds are among the most toxic chemicals known to mankind. Recent global military events, such as the conflict and disarmament in Syria, have brought into focus the need to find effective strategies for the rapid destruction of these banned chemicals. Solutions are needed for immediate personal protection (for example, the filtration and catalytic destruction of airborne versions of agents), bulk destruction of chemical weapon stockpiles, protection (via coating) of clothing, equipment and buildings, and containment of agent spills. Solid heterogeneous materials such as modified activated carbon or metal oxides exhibit many desirable characteristics for the destruction of chemical warfare agents. However, low sorptive capacities, low effective active site loadings, deactivation of the active site, slow degradation kinetics, and/or a lack of tailorability offer significant room for improvement in these materials. Here, we report a carefully chosen metal-organic framework (MOF) material featuring high porosity and exceptional chemical stability that is extraordinarily effective for the degradation of nerve agents and their simulants. Experimental and computational evidence points to Lewis-acidic Zr(IV) ions as the active sites and to their superb accessibility as a defining element of their efficacy.

REPRODUCTION AND AROMATASE ACTIVITY IN THE MARINE FISH CUNNER (TAUTOGOLABROUS ADSPERSUS) EXPOSED TO ATRAZINE AND OCTYLPHENOL IN THE LABORATORY

EPA Science Inventory

This study was conducted to test the hypothesis that reproduction in fish is altered by exposure to endocrine-disrupting chemicals (EDCs) that modify aromatase activity. Aromatase, a product of the CYP19 gene, is the enzyme that catalyzes the conversion of the androgens androst...

Sorption of lead from aqueous solution by chemically modified carbon adsorbents.

PubMed

Nadeem, Muhammad; Mahmood, A; Shahid, S A; Shah, S S; Khalid, A M; McKay, G

2006-12-01

An indigenously prepared, steam activated and chemically modified carbon from husk and pods of Moringa oleifera (M. oleifera), an agricultural waste, was comparatively examined as an adsorbent for the removal of lead from aqueous solutions. Studies were conducted as a function of contact time, initial metal concentration, dose of adsorbent, agitation speed, particle size and pH. Maximum uptake capacities were found to be, 98.89, 96.58, 91.8, 88.63, 79.43% for cetyltrimethyl ammonium bromide (CTAB), phosphoric, sulfuric, hydrochloric acid treated and untreated carbon adsorbents, respectively. Bangham, pseudo-first- and second-order, intra-particle diffusion equations were implemented to express the sorption mechanism by utilized adsorbents. Adsorption rate of lead ions was found to be considerably faster for chemically modified adsorbents than unmodified. The results of adsorption were fitted to both the Langmuir and Freundlich models. Satisfactory agreement between the metal uptake capacities by the adsorbents at different time intervals was expressed by the correlation coefficient (R(2)). The Langmuir model represented the sorption process better than the Freundlich one, with R(2) values ranging from 0.994 to 0.998.

The Electrochemical Behavior of Carbon Fiber Microelectrodes Modified with Carbon Nanotubes Using a Two-Step Electroless Plating/Chemical Vapor Deposition Process

PubMed Central

Lu, Longsheng; Liang, Linsheng; Teh, Kwok Siong; Xie, Yingxi; Wan, Zhenping; Tang, Yong

2017-01-01

Carbon fiber microelectrode (CFME) has been extensively applied in the biosensor and chemical sensor domains. In order to improve the electrochemical activity and sensitivity of the CFME, a new CFME modified with carbon nanotubes (CNTs), denoted as CNTs/CFME, was fabricated and investigated. First, carbon fiber (CF) monofilaments grafted with CNTs (simplified as CNTs/CFs) were fabricated in two key steps: (i) nickel electroless plating, followed by (ii) chemical vapor deposition (CVD). Second, a single CNTs/CF monofilament was selected and encapsulated into a CNTs/CFME with a simple packaging method. The morphologies of as-prepared CNTs/CFs were characterized by scanning electron microscopy. The electrochemical properties of CNTs/CFMEs were measured in potassium ferrocyanide solution (K4Fe(CN)6), by using a cyclic voltammetry (CV) and a chronoamperometry method. Compared with a bare CFME, a CNTs/CFME showed better CV curves with a higher distinguishable redox peak and response current; the higher the CNT content was, the better the CV curves were. Because the as-grown CNTs significantly enhanced the effective electrode area of CNTs/CFME, the contact area between the electrode and reactant was enlarged, further increasing the electrocatalytic active site density. Furthermore, the modified microelectrode displayed almost the same electrochemical behavior after 104 days, exhibiting remarkable stability and outstanding reproducibility. PMID:28358344

P7C3 neuroprotective chemicals function by activating the rate-limiting enzyme in NAD salvage.

PubMed

Wang, Gelin; Han, Ting; Nijhawan, Deepak; Theodoropoulos, Pano; Naidoo, Jacinth; Yadavalli, Sivaramakrishnan; Mirzaei, Hamid; Pieper, Andrew A; Ready, Joseph M; McKnight, Steven L

2014-09-11

The P7C3 class of aminopropyl carbazole chemicals fosters the survival of neurons in a variety of rodent models of neurodegeneration or nerve cell injury. To uncover its mechanism of action, an active derivative of P7C3 was modified to contain both a benzophenone for photocrosslinking and an alkyne for CLICK chemistry. This derivative was found to bind nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme involved in the conversion of nicotinamide into nicotinamide adenine dinucleotide (NAD). Administration of active P7C3 chemicals to cells treated with doxorubicin, which induces NAD depletion, led to a rebound in intracellular levels of NAD and concomitant protection from doxorubicin-mediated toxicity. Active P7C3 variants likewise enhanced the activity of the purified NAMPT enzyme, providing further evidence that they act by increasing NAD levels through its NAMPT-mediated salvage. Copyright © 2014 Elsevier Inc. All rights reserved.

Correlating In Vitro Splice Switching Activity With Systemic In Vivo Delivery Using Novel ZEN-modified Oligonucleotides.

PubMed

Hammond, Suzan M; McClorey, Graham; Nordin, Joel Z; Godfrey, Caroline; Stenler, Sofia; Lennox, Kim A; Smith, C I Edvard; Jacobi, Ashley M; Varela, Miguel A; Lee, Yi; Behlke, Mark A; Wood, Matthew J A; Andaloussi, Samir E L

2014-11-25

Splice switching oligonucleotides (SSOs) induce alternative splicing of pre-mRNA and typically employ chemical modifications to increase nuclease resistance and binding affinity to target pre-mRNA. Here we describe a new SSO non-base modifier (a naphthyl-azo group, "ZEN™") to direct exon exclusion in mutant dystrophin pre-mRNA to generate functional dystrophin protein. The ZEN modifier is placed near the ends of a 2'-O-methyl (2'OMe) oligonucleotide, increasing melting temperature and potency over unmodified 2'OMe oligonucleotides. In cultured H2K cells, a ZEN-modified 2'OMe phosphorothioate (PS) oligonucleotide delivered by lipid transfection greatly enhanced dystrophin exon skipping over the same 2'OMePS SSO lacking ZEN. However, when tested using free gymnotic uptake in vitro and following systemic delivery in vivo in dystrophin deficient mdx mice, the same ZEN-modified SSO failed to enhance potency. Importantly, we show for the first time that in vivo activity of anionic SSOs is modelled in vitro only when using gymnotic delivery. ZEN is thus a novel modifier that enhances activity of SSOs in vitro but will require improved delivery methods before its in vivo clinical potential can be realized.

High Levels of Sediment Contamination Have Little Influence on Estuarine Beach Fish Communities

PubMed Central

McKinley, Andrew C.; Dafforn, Katherine A.; Taylor, Matthew D.; Johnston, Emma L.

2011-01-01

While contaminants are predicted to have measurable impacts on fish assemblages, studies have rarely assessed this potential in the context of natural variability in physico-chemical conditions within and between estuaries. We investigated links between the distribution of sediment contamination (metals and PAHs), physico-chemical variables (pH, salinity, temperature, turbidity) and beach fish assemblages in estuarine environments. Fish communities were sampled using a beach seine within the inner and outer zones of six estuaries that were either heavily modified or relatively unmodified by urbanization and industrial activity. All sampling was replicated over two years with two periods sampled each year. Shannon diversity, biomass and abundance were all significantly higher in the inner zone of estuaries while fish were larger on average in the outer zone. Strong differences in community composition were also detected between the inner and outer zones. Few differences were detected between fish assemblages in heavily modified versus relatively unmodified estuaries despite high concentrations of sediment contaminants in the inner zones of modified estuaries that exceeded recognized sediment quality guidelines. Trends in species distributions, community composition, abundance, Shannon diversity, and average fish weight were strongly correlated to physico-chemical variables and showed a weaker relationship to sediment metal contamination. Sediment PAH concentrations were not significantly related to the fish assemblage. These findings suggest that variation in some physico-chemical factors (salinity, temperature, pH) or variables that co-vary with these factors (e.g., wave activity or grain size) have a much greater influence on this fish assemblage than anthropogenic stressors such as contamination. PMID:22039470

Effect of replacing the aspartic acid/glutamic acid residues of bullfrog sialic acid binding lectin with asparagine/glutamine and arginine on the inhibition of cell proliferation in murine leukemia P388 cells.

PubMed

Ogawa, Yuko; Iwama, Masanori; Ohgi, Kazuko; Tsuji, Tsutomu; Irie, Masachika; Itagaki, Tadashi; Kobayashi, Hiroko; Inokuchi, Norio

2002-06-01

The sialic acid binding lectin from bullfrog oocytes (cSBL) is known to have anti-tumor activity. In a previous report, to elucidate the relationship between the net charge and anti-tumor activity of cSBL, we examined the effect of chemical modifications of cSBL with a water-soluble carbodiimide in the presence of various nucleophiles. The results suggested that the anti-tumor activity and internalization into tumor cells increased with an increase in the net charge of cSBL. However, in the chemically modified cSBL, a modification site was observed on average in two of the carboxyl groups of cSBL. To confirm these previous results and to determine which modified carboxyl group contributes to the increase in anti-tumor activity, we prepared mutants with substitutions of Asn/Gln and Arg at three acidic amino acid residues of cSBL and studied their anti-tumor activity and internalization efficiency. The results showed the enhancing effect of charge on anti-tumor activity and internalization, and suggested that the replacement of D24 and E88 of cSBL with arginine is more effective than that of E97. The double mutant D24RE88R showed comparable anti-tumor activity to the ethylenediamine-modified cSBL reported previously. The mutant was well-characterized as a pure cSBL derivative suitable for studying the mechanism of the anti-tumor action of cSBL.

Chemical methods for encoding and decoding of posttranslational modifications

PubMed Central

Chuh, Kelly N.; Batt, Anna R.; Pratt, Matthew R.

2016-01-01

A large array of posttranslational modifications can dramatically change the properties of proteins and influence different aspects of their biological function such as enzymatic activity, binding interactions, and proteostasis. Despite the significant knowledge that has been gained about the function of posttranslational modifications using traditional biological techniques, the analysis of the site-specific effects of a particular modification, the identification of the full compliment of modified proteins in the proteome, and the detection of new types of modifications remains challenging. Over the years, chemical methods have contributed significantly in both of these areas of research. This review highlights several posttranslational modifications where chemistry-based approaches have made significant contributions to our ability to both prepare homogeneously modified proteins and identify and characterize particular modifications in complex biological settings. As the number and chemical diversity of documented posttranslational modifications continues to rise, we believe that chemical strategies will be essential to advance the field in years to come. PMID:26933738

Chemical modification, antioxidant and α-amylase inhibitory activities of corn silk polysaccharides.

PubMed

Chen, Shuhan; Chen, Haixia; Tian, Jingge; Wang, Yanwei; Xing, Lisha; Wang, Jia

2013-10-15

Water-soluble corn silk polysaccharides (CSPS) were chemically modified to obtain their sulfated, acetylated and carboxymethylated derivatives. Chemical characterization and bioactivities of CSPS and its derivatives were comparatively investigated by chemical methods, gas chromatography, gel filtration chromatography, scanning electron microscope, infrared spectroscopy and circular dichroism spectroscopy, scavenging DPPH free radical assay, scavenging hydroxyl radical assay, ferric reducing power assay, lipid peroxidation inhibition assay and α-amylase activity inhibitory assay, respectively. Among the three derivatives, carboxylmethylated polysaccharide (C-CSPS) demonstrated higher solubility, narrower molecular weight distribution, lower intrinsic viscosity, a hyperbranched conformation, significantly higher antioxidant and α-amylase inhibitory abilities compared with the native polysaccharide and other derivatives. C-CSPS might be used as a novel nutraceutical agent for human consumption. Copyright © 2013 Elsevier Ltd. All rights reserved.

Molecular modification of native coffee polysaccharide using subcritical water treatment: Structural characterization, antioxidant, and DNA protecting activities.

PubMed

Getachew, Adane Tilahun; Chun, Byung Soo

2017-06-01

Polysaccharides are an abundant resource in coffee beans and have proved to show numerous bioactivities. Despite their abundance, their activities are not always satisfactory mostly due to their structure and large molecular size. Molecular modifications of native polysaccharides can overcome this problem. In this study, we used a novel and green method to modify native coffee polysaccharides using subcritical water (SCW) treatment. The SCW treatment was used at the temperature of 180°C-220°C and pressure of 30-60bar. The molecular and structural modification of the polysaccharides was confirmed using several techniques such as FT-IR, UV spectroscopy, XRD, and TGA. The antioxidant activity of the modified polysaccharides was evaluated using several chemical and Saccharomyces cerevisiae-based high throughput assays. The modified polysaccharides showed high antioxidant activities in all tested assays. Moreover, the polysaccharides showed high DNA protection activities. Therefore, SCW could be employed as a green solvent for molecular modification of polysaccharides. Copyright © 2017 Elsevier B.V. All rights reserved.

Environmentally friendly pervious concrete for treating deicer-laden stormwater (phase one report).

DOT National Transportation Integrated Search

2015-12-30

A graphene oxide-modified pervious concrete was developed by using low-reactivity, high-calcium fly ash as sole binder and chemical : activators and other admixtures. The density, void ratio, mechanical strength, infiltration rate, Youngs modulus,...

Surface modification to improve fireside corrosion resistance of Fe-Cr ferritic steels

DOEpatents

Park, Jong-Hee; Natesan, Krishnamurti; Rink, David L.

2010-03-16

An article of manufacture and a method for providing an Fe--Cr ferritic steel article of manufacture having a surface layer modification for corrosion resistance. Fe--Cr ferritic steels can be modified to enhance their corrosion resistance to liquid coal ash and other chemical environments, which have chlorides or sulfates containing active species. The steel is modified to form an aluminide/silicide passivating layer to reduce such corrosion.

A High-Throughput Screen Reveals New Small-Molecule Activators and Inhibitors of Pantothenate Kinases

PubMed Central

2016-01-01

Pantothenate kinase (PanK) is a regulatory enzyme that controls coenzyme A (CoA) biosynthesis. The association of PanK with neurodegeneration and diabetes suggests that chemical modifiers of PanK activity may be useful therapeutics. We performed a high throughput screen of >520000 compounds from the St. Jude compound library and identified new potent PanK inhibitors and activators with chemically tractable scaffolds. The HTS identified PanK inhibitors exemplified by the detailed characterization of a tricyclic compound (7) and a preliminary SAR. Biophysical studies reveal that the PanK inhibitor acts by binding to the ATP–enzyme complex. PMID:25569308

Reverse Induced Fit-Driven MAS-Downstream Transduction: Looking for Metabotropic Agonists.

PubMed

Pernomian, Larissa; Gomes, Mayara S; de Paula da Silva, Carlos H Tomich; Rosa, Joaquin M C

2017-01-01

Protective effects of MAS activation have spurred clinical interests in developing MAS agonists. However, current bases that drive this process preclude that physiological concentrations of peptide MAS agonists induce an atypical signaling that does not reach the metabotropic efficacy of constitutive activation. Canonical activation of MAS-coupled G proteins is only achieved by supraphysiological concentrations of peptide MAS agonists or physiological concentrations of chemically modified analogues. These pleiotropic differences are because of two overlapped binding domains: one non-metabotropic site that recognizes peptide agonists and one metabotropic domain that recognizes modified analogues. It is feasible that supraphysiological concentrations of peptide MAS agonists undergo to chemical modifications required for binding to metabotropic domain. Receptor oligomerization enhances pharmacological parameters coupled to metabotropic signaling. The formation of receptor-signalosome complex makes the transduction of agonists more adaptive. Considering the recent identification of MAS-signalosome, we aimed to postulate the reverse induced fit hypothesis in which MAS-signalosome would trigger chemical modifications required for agonists bind to MAS metabotropic domain. Here we cover rational perspectives for developing novel metabotropic MAS agonists in the view of the reverse induced-fit hypothesis. Predicting a 3D model of MAS metabotropic domain may guide the screening of chemical modifications required for metabotropic efficacy. Pharmacophore-based virtual screening would select potential metabotropic MAS agonists from virtual libraries from human proteome. Rational perspectives that consider reverse induced fit hypothesis during MAS activation for developing metabotropic MAS agonists represents the best approach in providing MAS ligands with constitutive efficacy at physiological concentrations. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Impact of trehalose on the activity of sodium and potassium chloride in aqueous solutions: Why trehalose is worth its salt.

PubMed

Poplinger, Michal; Shumilin, Ilan; Harries, Daniel

2017-12-15

Trehalose is revered for its multiple unique impacts on solution properties, including the ability to modulate the salty and bitter tastes of sodium and potassium salts. However, the molecular mechanisms underlying trehalose's effect on taste perception are unknown. Here we focus on the physico-chemical effect of trehalose to alter the activity of monovalent salts in aqueous solution. Using a modified isopiestic methodology that relies on contemporary vapor pressure osmometry, we elucidate how trehalose modifies the thermodynamic chemical activity of sodium and potassium chloride, as well as the effect of the salts on the sugar's activity. We find that trehalose has a specific impact on potassium chloride that is unlike that of other sugars or polyols. Remarkably, especially at low salt concentrations, trehalose considerably elevates the activity (or chemical potential) of KCl, raising the salt activity coefficient as high as ∼1.5 its value in the absence of the sugar. Moreover, in contrast to their action on other known carbohydrates, both KCl and NaCl act as salting-out agents towards trehalose, as seen in the elevated activity coefficient compared with its value in pure water (up to ∼1.5 higher at low sugar and salt concentrations). We discuss the possible relevance of our findings to the mechanism of trehalose taste perception modification, and point to necessary future directed sensory experiments needed to resolve the possible link between our findings and the emerging biochemical or physiological mechanisms involved. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural analysis of an innate immunostimulant from broccoli, Brassica oleracea var. italica.

PubMed

Urai, Makoto; Kataoka, Keiko; Nishida, Satoshi; Sekimizu, Kazuhisa

2017-11-22

Vegetables are eaten as part of a healthy diet throughout the world, and some are also applied topically as a traditional medicine. We evaluated the innate immunostimulating activities of hot water extracts of various vegetables using the silkworm muscle contraction assay system, and found that broccoli, Brassica oleracea var. italica, contains a strong innate immunostimulant. We purified the innate immunostimulant from broccoli, and characterized the chemical structure by chemical analyses and NMR spectroscopy. The innate immunostimulant comprised galacturonic acid, galactose, glucose, arabinose, and rhamnose, and had a pectic-like polysaccharide structure. To determine the structural motif involved in the innate immunostimulating activity, we modified the structure by chemical and enzymatic treatment, and found that the activity was attenuated by pectinase digestion. These findings suggest that a pectic-like polysaccharide purified from broccoli has innate immune-stimulating activity, for which the polygalacturonic acid structure is necessary.

Antimicrobial activity of chemically modified dextran derivatives.

PubMed

Tuchilus, Cristina G; Nichifor, Marieta; Mocanu, Georgeta; Stanciu, Magdalena C

2017-04-01

Cationic amphiphilic dextran derivatives with a long alkyl group attached to the reductive end of the polysaccharide chain and quaternary ammonium groups attached as pendent groups to the main dextran backbone were synthesized and tested for their antimicrobial properties against several bacteria and fungi strains. Dependence of antimicrobial activity on both polymer chemical composition (dextran molar mass, length of end alkyl group and chemical structure of ammonium groups) and type of microbes was highlighted by disc-diffusion method (diameter of inhibition zone) and broth microdilution method (minimum inhibitory concentrations). Polymers had antimicrobial activity for all strains studied, except for Pseudomonas aeruginosa ATCC 27853. The best activity against Staphylococcus aureus (Minimun Inhibitory Concentration 60μg/mL) was provided by polymers obtained from dextran with lower molecular mass (Mn=4500), C 12 H 25 or C 18 H 37 end groups, and N,N-dimethyl-N-benzylammonium pendent groups. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biofouling-resistant ceragenin-modified materials and structures for water treatment

DOEpatents

Hibbs, Michael; Altman, Susan J.; Jones, Howland D. T.; Savage, Paul B.

2013-09-10

This invention relates to methods for chemically grafting and attaching ceragenin molecules to polymer substrates; methods for synthesizing ceragenin-containing copolymers; methods for making ceragenin-modified water treatment membranes and spacers; and methods of treating contaminated water using ceragenin-modified treatment membranes and spacers. Ceragenins are synthetically produced antimicrobial peptide mimics that display broad-spectrum bactericidal activity. Alkene-functionalized ceragenins (e.g., acrylamide-functionalized ceragenins) can be attached to polyamide reverse osmosis membranes using amine-linking, amide-linking, UV-grafting, or silane-coating methods. In addition, silane-functionalized ceragenins can be directly attached to polymer surfaces that have free hydroxyls.

Wine microbiology is driven by vineyard and winery anthropogenic factors.

PubMed

Grangeteau, Cédric; Roullier-Gall, Chloé; Rousseaux, Sandrine; Gougeon, Régis D; Schmitt-Kopplin, Philippe; Alexandre, Hervé; Guilloux-Benatier, Michèle

2017-03-01

The effects of different anthropic activities (vineyard: phytosanitary protection; winery: pressing and sulfiting) on the fungal populations of grape berries were studied. The global diversity of fungal populations (moulds and yeasts) was performed by pyrosequencing. The anthropic activities studied modified fungal diversity. Thus, a decrease in biodiversity was measured for three successive vintages for the grapes of the plot cultivated with Organic protection compared to plots treated with Conventional and Ecophyto protections. The fungal populations were then considerably modified by the pressing-clarification step. The addition of sulfur dioxide also modified population dynamics and favoured the domination of the species Saccharomyces cerevisiae during fermentation. The non-targeted chemical analysis of musts and wines by FT-ICR-MS showed that the wines could be discriminated at the end of alcoholic fermentation as a function of adding SO 2 or not, but also and above all as a function of phytosanitary protection, regardless of whether these fermentations took place in the presence of SO 2 or not. Thus, the existence of signatures in wines of chemical diversity and microbiology linked to vineyard protection has been highlighted. © 2016 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

A graphene-based electrochemical sensor for sensitive detection of paracetamol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Xinhuang; Wang, Jun; Wu, Hong

2010-05-15

An electrochemical sensor based on the electrocatalytic activity of functionalized graphene for sensitive detection of paracetamol is presented. The electrochemical behaviors of paracetamol on graphene-modified glassy carbon electrodes (GCEs) were investigated by cyclic voltammetry and square-wave voltammetry. The results showed that the graphene-modified electrode exhibited excellent electrocatalytic activity to paracetamol. A quasi-reversible redox process of paracetamol at the modified electrode was obtained, and the over-potential of paracetamol decreased significantly compared with that at the bare GCE. Such electrocatalytic behavior of graphene is attributed to its unique physical and chemical properties, e.g., subtle electronic characteristics, attractive π–π interaction, and strong adsorptivemore » capability. The sensor shows great promise for simple, sensitive, and quantitative detection of paracetamol.« less

In vitro biocompatibility of the surface ion modified NiTi alloy

NASA Astrophysics Data System (ADS)

Gudimova, Ekaterina Yu.; Meisner, Ludmila L.; Lotkov, Aleksander I.; Matveeva, Vera A.; Meisner, Stanislav N.; Matveev, Andrey L.; Shabalina, Olga I.

2016-11-01

This paper presents the results of the chemical, topographic and structural properties of the NiTi alloy surface and their changes after surface treatments by ion implantation techniques with use of ions Ta+ and Si+. The influence of physicochemical properties of the surface ion modified NiTi alloy was studied on in vitro cultured mesenchymal stem cells of the rats' bone marrow. It is shown that the ion surface modification improves histocompatibility of the NiTi alloy and leads to increase of proliferative activity of mesenchymal stem cells on its surface. It was experimentally found that a major contribution to viability improvement mesenchymal stem cells of rat marrow has the chemical composition and the microstructure of the surface area.

Applicability of vacuum impregnation to modify physico-chemical, sensory and nutritive characteristics of plant origin products--a review.

PubMed

Radziejewska-Kubzdela, Elżbieta; Biegańska-Marecik, Róża; Kidoń, Marcin

2014-09-19

Vacuum impregnation is a non-destructive method of introducing a solution with a specific composition to the porous matrices of fruit and vegetables. Mass transfer in this process is a result of mechanically induced differences in pressure. Vacuum impregnation makes it possible to fill large volumes of intercellular spaces in tissues of fruit and vegetables, thus modifying physico-chemical properties and sensory attributes of products. This method may be used, e.g., to reduce pH and water activity of the product, change its thermal properties, improve texture, color, taste and aroma. Additionally, bioactive compounds may be introduced together with impregnating solutions, thus improving health-promoting properties of the product or facilitating production of functional food.

Effects of different surface modifying agents on the cytotoxic and antimicrobial properties of ZnO nanoparticles.

PubMed

Esparza-González, S C; Sánchez-Valdés, S; Ramírez-Barrón, S N; Loera-Arias, M J; Bernal, J; Meléndez-Ortiz, H Iván; Betancourt-Galindo, R

2016-12-01

Zinc oxide (ZnO) nanoparticles (NPs) have received considerable attention in the medical field because of their antibacterial properties, primarily for killing and reducing the activity of numerous microorganisms. The purpose of this study was to determine whether surface-modified ZnO NPs exhibit different properties compared with unmodified ZnO. The antimicrobial and cytotoxic properties of modified ZnO NPs as well as their effects on inflammatory cytokine production were evaluated. ZnO NPs were prepared using a wet chemical method. Then, the surfaces of these NPs were modified using 3-aminopropyltriethoxysilane (APTES) and dimethyl sulfoxide (DMSO) as modifying agents via a chemical hydrolysis method. According to infrared spectroscopy analysis (FTIR), the structure of the ZnO remained unchanged after modification. Antibacterial assays demonstrated that APTES modification is more effective at inducing an antimicrobial effect against Gram-negative bacteria than against Gram-positive bacteria. Cytotoxicity studies showed that cell viability was dose-dependent; moreover, pristine and APTES-modified ZnO exhibited low cytotoxicity, whereas DMSO-modified ZnO exhibited toxicity even at a low NP concentration. An investigation of inflammatory cytokine production demonstrated that the extent of stimulation was related to the ZnO NP concentration but not to the surface modification, except for IFN-γ and IL-10, which were not detected even at high NP concentrations. Copyright © 2016 Elsevier B.V. All rights reserved.

Chemical modification of polyvinyl chloride and silicone elastomer in inhibiting adhesion of Aeromonas hydrophila.

PubMed

Kregiel, Dorota; Berlowska, Joanna; Mizerska, Urszula; Fortuniak, Witold; Chojnowski, Julian; Ambroziak, Wojciech

2013-07-01

Disease-causing bacteria of the genus Aeromonas are able to adhere to pipe materials, colonizing the surfaces and forming biofilms in water distribution systems. The aim of our research was to study how the modification of materials used commonly in the water industry can reduce bacterial cell attachment. Polyvinyl chloride and silicone elastomer surfaces were activated and modified with reactive organo-silanes by coupling or co-crosslinking silanes with the native material. Both the native and modified surfaces were tested using the bacterial strain Aeromonas hydrophila, which was isolated from the Polish water distribution system. The surface tension of both the native and modified surfaces was measured. To determine cell viability and bacterial adhesion two methods were used, namely plate count and luminometry. Results were expressed in colony-forming units (c.f.u.) and in relative light units (RLU) per cm(2). Almost all the chemically modified surfaces exhibited higher anti-adhesive and anti-microbial properties in comparison to the native surfaces. Among the modifying agents examined, poly[dimethylsiloxane-co-(N,N-dimethyl-N-n-octylammoniopropyl chloride) methylsiloxane)] terminated with hydroxydimethylsilyl groups (20 %) in silicone elastomer gave the most desirable results. The surface tension of this modifier, was comparable to the non-polar native surface. However, almost half of this value was due to the result of polar forces. In this case, in an adhesion analysis, only 1 RLU cm(-2) and less than 1 c.f.u. cm(-2) were noted. For the native gumosil, the results were 9,375 RLU cm(-2) and 2.5 × 10(8) c.f.u. cm(-2), respectively. The antibacterial activity of active organo-silanes was associated only with the carrier surface because no antibacterial compounds were detected in liquid culture media, in concentrations that were able to inhibit cell growth.

Preparation of activated carbon from a renewable bio-plant of Euphorbia rigida by H 2SO 4 activation and its adsorption behavior in aqueous solutions

NASA Astrophysics Data System (ADS)

Gerçel, Özgül; Özcan, Adnan; Özcan, A. Safa; Gerçel, H. Ferdi

2007-03-01

The use of activated carbon obtained from Euphorbia rigida for the removal of a basic textile dye, which is methylene blue, from aqueous solutions at various contact times, pHs and temperatures was investigated. The plant material was chemically modified with H 2SO 4. The surface area of chemically modified activated carbon was 741.2 m 2 g -1. The surface characterization of both plant- and activated carbon was undertaken using FTIR spectroscopic technique. The adsorption process attains equilibrium within 60 min. The experimental data indicated that the adsorption isotherms are well described by the Langmuir equilibrium isotherm equation and the calculated adsorption capacity of activated carbon was 114.45 mg g -1 at 40° C. The adsorption kinetics of methylene blue obeys the pseudo-second-order kinetic model and also followed by the intraparticle diffusion model up to 60 min. The thermodynamic parameters such as Δ G°, Δ H° and Δ S° were calculated to estimate the nature of adsorption. The activation energy of the system was calculated as 55.51 kJ mol -1. According to these results, prepared activated carbon could be used as a low-cost adsorbent to compare with the commercial activated carbon for the removal textile dyes from textile wastewater processes.

Chemical glycosylation of cytochrome c improves physical and chemical protein stability.

PubMed

Delgado, Yamixa; Morales-Cruz, Moraima; Hernández-Román, José; Martínez, Yashira; Griebenow, Kai

2014-08-06

Cytochrome c (Cyt c) is an apoptosis-initiating protein when released into the cytoplasm of eukaryotic cells and therefore a possible cancer drug candidate. Although proteins have been increasingly important as pharmaceutical agents, their chemical and physical instability during production, storage, and delivery remains a problem. Chemical glycosylation has been devised as a method to increase protein stability and thus enhance their long-lasting bioavailability. Three different molecular weight glycans (lactose and two dextrans with 1 kD and 10 kD) were chemically coupled to surface exposed Cyt c lysine (Lys) residues using succinimidyl chemistry via amide bonds. Five neo-glycoconjugates were synthesized, Lac4-Cyt-c, Lac9-Cyt-c, Dex5(10kD)-Cyt-c, Dex8(10kD)-Cyt-c, and Dex3(1kD)-Cyt-c. Subsequently, we investigated glycoconjugate structure, activity, and stability. Circular dichroism (CD) spectra demonstrated that Cyt c glycosylation did not cause significant changes to the secondary structure, while high glycosylation levels caused some minor tertiary structure perturbations. Functionality of the Cyt c glycoconjugates was determined by performing cell-free caspase 3 and caspase 9 induction assays and by measuring the peroxidase-like pseudo enzyme activity. The glycoconjugates showed ≥94% residual enzyme activity and 86 ± 3 to 95 ± 1% relative caspase 3 activation compared to non-modified Cyt c. Caspase 9 activation by the glycoconjugates was with 92 ± 7% to 96 ± 4% within the error the same as the caspase 3 activation. There were no major changes in Cyt c activity upon glycosylation. Incubation of Dex3(1 kD)-Cyt c with mercaptoethanol caused significant loss in the tertiary structure and a drop in caspase 3 and 9 activation to only 24 ± 8% and 26 ± 6%, respectively. This demonstrates that tertiary structure intactness of Cyt c was essential for apoptosis induction. Furthermore, glycosylation protected Cyt c from detrimental effects by some stresses (i.e., elevated temperature and humidity) and from proteolytic degradation. In addition, non-modified Cyt c was more susceptible to denaturation by a water-organic solvent interface than its glycoconjugates, important for the formulation in polymers. The results demonstrate that chemical glycosylation is a potentially valuable method to increase Cyt c stability during formulation and storage and potentially during its application after administration.

Biophysical analysis of the effect of chemical modification by 4-oxononenal on the structure, stability, and function of binding immunoglobulin protein (BiP)

PubMed Central

Shah, Dinen D.; Singh, Surinder M.; Dzieciatkowska, Monika

2017-01-01

Binding immunoglobulin protein (BiP) is a molecular chaperone important for the folding of numerous proteins, which include millions of immunoglobulins in human body. It also plays a key role in the unfolded protein response (UPR) in the endoplasmic reticulum. Free radical generation is a common phenomenon that occurs in cells under healthy as well as under stress conditions such as ageing, inflammation, alcohol consumption, and smoking. These free radicals attack the cell membranes and generate highly reactive lipid peroxidation products such as 4-oxononenal (4-ONE). BiP is a key protein that is modified by 4-ONE. In this study, we probed how such chemical modification affects the biophysical properties of BiP. Upon modification, BiP shows significant tertiary structural changes with no changes in its secondary structure. The protein loses its thermodynamic stability, particularly, that of the nucleotide binding domain (NBD) where ATP binds. In terms of function, the modified BiP completely loses its ATPase activity with decreased ATP binding affinity. However, modified BiP retains its immunoglobulin binding function and its chaperone activity of suppressing non-specific protein aggregation. These results indicate that 4-ONE modification can significantly affect the structure-function of key proteins such as BiP involved in cellular pathways, and provide a molecular basis for how chemical modifications can result in the failure of quality control mechanisms inside the cell. PMID:28886061

Cyanographone and isocyanographone — Two asymmetrically functionalized graphene pseudohalides and their potential use in chemical sensing

NASA Astrophysics Data System (ADS)

Marsoner Steinkasserer, Lukas Eugen; Pohl, Vincent; Paulus, Beate

2018-02-01

Graphene pseudohalides are natural candidates for use in molecular sensing due to their greater chemical activity as compared to both graphene halides and pristine graphene. Though their study is still in its infancy, being hindered until recently by the unavailability of both selective and efficient procedures for their synthesis, they promise to considerably widen the application potential of chemically modified graphenes. Herein, we employ van der Waals density functional theory to study the structural and electronic properties of two selected graphene pseudohalides, namely, cyanographone and isocyanographone and investigate the potential use of the latter as a chemical sensor via electron transport calculations.

Chemical modification of Saccharomycopsis fibuligera R64 α-amylase to improve its stability against thermal, chelator, and proteolytic inactivation.

PubMed

Ismaya, Wangsa Tirta; Hasan, Khomaini; Kardi, Idar; Zainuri, Amalia; Rahmawaty, Rinrin Irma; Permanahadi, Satyawisnu; El Viera, Baiq Vera; Harinanto, Gunawan; Gaffar, Shabarni; Natalia, Dessy; Subroto, Toto; Soemitro, Soetijoso

2013-05-01

α-Amylase catalyzes hydrolysis of starch to oligosaccharides, which are further degraded to simple sugars. The enzyme has been widely used in food and textile industries and recently, in generation of renewable energy. An α-amylase from yeast Saccharomycopsis fibuligera R64 (Sfamy) is active at 50 °C and capable of degrading raw starch, making it attractive for the aforementioned applications. To improve its characteristics as well as to provide information for structural study ab initio, the enzyme was chemically modified by acid anhydrides (nonpolar groups), glyoxylic acid (GA) (polar group), dimethyl adipimidate (DMA) (cross-linking), and polyethylene glycol (PEG) (hydrophilization). Introduction of nonpolar groups increased enzyme stability up to 18 times, while modification by a cross-linking agent resulted in protection of the calcium ion, which is essential for enzyme activity and integrity. The hydrophilization with PEG resulted in protection against tryptic digestion. The chemical modification of Sfamy by various modifiers has thereby resulted in improvement of its characteristics and provided systematic information beneficial for structural study of the enzyme. An in silico structural study of the enzyme improved the interpretation of the results.

Grafting of activated carbon cloths for selective adsorption

NASA Astrophysics Data System (ADS)

Gineys, M.; Benoit, R.; Cohaut, N.; Béguin, F.; Delpeux-Ouldriane, S.

2016-05-01

Chemical functionalization of an activated carbon cloth with 3-aminophthalic acid and 4-aminobenzoic acid groups by the in situ formation of the corresponding diazonium salt in aqueous acidic solution is reported. The nature and amount of selected functions on an activated carbon surface, in particular the grafted density, were determined by potentiometric titration, elemental analysis and X-ray photoelectron spectroscopy (XPS). The nanotextural properties of the modified carbon were explored by gas adsorption. Functionalized activated carbon cloth was obtained at a discrete grafting level while preserving interesting textural properties and a large porous volume. Finally, the grafting homogeneity of the carbon surface and the nature of the chemical bonding were investigated using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) technique.

Chemically modified graphite for electrochemical cells

DOEpatents

Greinke, R.A.; Lewis, I.C.

1998-05-26

This invention relates to chemically modified graphite particles: (a) that are useful in alkali metal-containing electrode of a electrochemical cell comprising: (1) the electrode, (2) a non-aqueous electrolytic solution comprising an organic aprotic solvent which solvent tends to decompose when the electrochemical cell is in use, and an electrically conductive salt of an alkali metal, and (3) a counter electrode; and (b) that are chemically modified with fluorine, chlorine, iodine or phosphorus to reduce such decomposition. This invention also relates to electrodes comprising such chemically modified graphite and a binder and to electrochemical cells containing such electrodes. 3 figs.

Chemically modified graphite for electrochemical cells

DOEpatents

Greinke, Ronald Alfred; Lewis, Irwin Charles

1998-01-01

This invention relates to chemically modified graphite particles: (a) that are useful in alkali metal-containing electrode of a electrochemical cell comprising: (i) the electrode, (ii) a non-aqueous electrolytic solution comprising an organic aprotic solvent which solvent tends to decompose when the electrochemical cell is in use, and an electrically conductive salt of an alkali metal, and (iii) a counterelectrode; and (b) that are chemically modified with fluorine, chlorine, iodine or phosphorus to reduce such decomposition. This invention also relates to electrodes comprising such chemically modified graphite and a binder and to electrochemical cells containing such electrodes.

40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section for...

40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section for...

40 CFR 721.10504 - Surface modified magnesium hydroxide (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Surface modified magnesium hydroxide... Specific Chemical Substances § 721.10504 Surface modified magnesium hydroxide (generic). (a) Chemical... as surface modified magnesium hydroxide (PMN P-06-682) is subject to reporting under this section for...

40 CFR 721.10504 - Surface modified magnesium hydroxide (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Surface modified magnesium hydroxide... Specific Chemical Substances § 721.10504 Surface modified magnesium hydroxide (generic). (a) Chemical... as surface modified magnesium hydroxide (PMN P-06-682) is subject to reporting under this section for...

40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this section...

40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this section...

40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this section...

40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this section...

40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this section...

40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section for...

40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section for...

40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section for...

40 CFR 721.5908 - Modified phenolic resin (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified phenolic resin (generic). 721... Substances § 721.5908 Modified phenolic resin (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as modified phenolic resin (PMN P...

40 CFR 721.5905 - Modified phenolic resin (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified phenolic resin (generic). 721... Substances § 721.5905 Modified phenolic resin (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a modified phenolic resin (PMN...

[Adsorption of phenol chemicals by surfactant-modified zeolites].

PubMed

Xie, Jie; Wang, Zhe; Wu, De-Yi; Li, Chun-Jie

2012-12-01

Two kinds of zeolites were prepared from fly ash and modified by surfactant subsequently. Surfactant-modified zeolites were studied for adsorption of phenol chemicals (phenol, p-chlorphenol, bisphenol A). It showed that the adsorption affinity of zeolite to phenol chemicals was significantly improved after surfactant modification. The adsorption isotherms of phenol chemicals were well fitted by the Langmuir isotherm. For the two surfactant-surfactant modified zeolites, the maximum adsorption amounts of phenol, p-chlorphenol, and bisphenol A calculated from the Langmuir equation were 37.7, 52.36, 90.9 mg x g(-1) and 10.7, 22.83, 56.8 mg x g(-1), respectively. When pH values of solutions were higher than the pK(a) values of phenol chemicals, the removal efficiencies were getting higher with the increase of pH values. The octanol/water partition coefficient (K(ow)) was also found to be an important factor affecting adsorption of phenol chemicals by the modified zeolites. Higher K(ow) value, which means the greater hydrophobicity of the chemicals, resulted in a higher removal.

40 CFR 721.2540 - Diphenylmethane diisocyanate (MDI) modified.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.2540 Diphenylmethane diisocyanate (MDI) modified. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a...

Characterization of the chemical structure and innate immune-stimulating activity of an extracellular polysaccharide from Rhizobium sp. strain M2 screened using a silkworm muscle contraction assay.

PubMed

Urai, Makoto; Aizawa, Tomoko; Imamura, Katsutoshi; Hamamoto, Hiroshi; Sekimizu, Kazuhisa

2017-11-22

We screened innate immunostimulant-producing bacteria using a silkworm muscle contraction assay, and isolated Rhizobium sp. strain M2 from soil. We purified the innate immunostimulant from strain M2, and characterized the chemical structure by nuclear magnetic resonance spectroscopy and chemical analyses. The innate immunostimulant (M2 EPS) comprised glucose, galactose, pyruvic acid, and succinic acid with a molar ratio of 6.8:1.0:0.9:0.4, and had a succinoglycan-like high molecular-weight heteropolysaccharide structure. To determine the structural motif involved in the innate immunostimulating activity, we modified the M2 EPS structure chemically, and found that the activity was increased by removal of the succinic and pyruvic acid substitutions. Strong acid hydrolysis completely inactivated the M2 EPS. Unmasking of the β-1,3/6-glucan structure of the side-chain by deacylation and depyruvylation may enhance the innate immune-stimulating activity of M2 EPS. These findings suggest that the succinoglycan-like polysaccharide purified from strain M2 has innate immune-stimulating activity, and its glycan structure is necessary for the activity.

Chemical synthesis of membrane proteins by the removable backbone modification method.

PubMed

Tang, Shan; Zuo, Chao; Huang, Dong-Liang; Cai, Xiao-Ying; Zhang, Long-Hua; Tian, Chang-Lin; Zheng, Ji-Shen; Liu, Lei

2017-12-01

Chemical synthesis can produce membrane proteins bearing specifically designed modifications (e.g., phosphorylation, isotope labeling) that are difficult to obtain through recombinant protein expression approaches. The resulting homogeneously modified synthetic membrane proteins are valuable tools for many advanced biochemical and biophysical studies. This protocol describes the chemical synthesis of membrane proteins by condensation of transmembrane peptide segments through native chemical ligation. To avoid common problems encountered due to the poor solubility of transmembrane peptides in almost any solvent, we describe an effective procedure for the chemical synthesis of membrane proteins through the removable-backbone modification (RBM) strategy. Two key steps of this protocol are: (i) installation of solubilizing Arg4-tagged RBM groups into the transmembrane peptides at any primary amino acid through Fmoc (9-fluorenylmethyloxycarbonyl) solid-phase peptide synthesis and (ii) native ligation of the full-length sequence, followed by removal of the RBM tags by TFA (trifluoroacetic acid) cocktails to afford the native protein. The installation of RBM groups is achieved by using 4-methoxy-5-nitrosalicyladehyde by reduction amination to incorporate an activated O-to-N acyl transfer auxiliary. The Arg4-tag-modified membrane-spanning peptide segments behave like water-soluble peptides to facilitate their purification, ligation and mass characterization.

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.3135 - Phosphorous modified epoxy resin (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Phosphorous modified epoxy resin... Specific Chemical Substances § 721.3135 Phosphorous modified epoxy resin (generic). (a) Chemical substance... phosphorous modified epoxy resin (PMNs P-00-992 and P-01-471) is subject to reporting under this section for...

40 CFR 721.10082 - Amine modified monomer acrylate (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Amine modified monomer acrylate... Specific Chemical Substances § 721.10082 Amine modified monomer acrylate (generic). (a) Chemical substance... amine modified monomer acrylate (PMN P-06-29) is subject to reporting under this section for the...

40 CFR 721.10082 - Amine modified monomer acrylate (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amine modified monomer acrylate... Specific Chemical Substances § 721.10082 Amine modified monomer acrylate (generic). (a) Chemical substance... amine modified monomer acrylate (PMN P-06-29) is subject to reporting under this section for the...

40 CFR 721.3710 - Polyether modified fatty acids (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polyether modified fatty acids... Specific Chemical Substances § 721.3710 Polyether modified fatty acids (generic). (a) Chemical substance... Polyether modified fatty acids (PMN P-99-0435) is subject to reporting under this section for the...

40 CFR 721.10089 - Modified salicylic acid, zirconium complex (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified salicylic acid, zirconium... Specific Chemical Substances § 721.10089 Modified salicylic acid, zirconium complex (generic). (a) Chemical... as modified salicylic acid, zirconium complex (PMN P-00-552) is subject to reporting under this...

40 CFR 721.10089 - Modified salicylic acid, zirconium complex (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified salicylic acid, zirconium... Specific Chemical Substances § 721.10089 Modified salicylic acid, zirconium complex (generic). (a) Chemical... as modified salicylic acid, zirconium complex (PMN P-00-552) is subject to reporting under this...

40 CFR 721.4380 - Modified hydrocarbon resin.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified hydrocarbon resin. 721.4380... Substances § 721.4380 Modified hydrocarbon resin. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a modified hydrocarbon resin (P-91-1418) is...

40 CFR 721.3710 - Polyether modified fatty acids (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Polyether modified fatty acids... Specific Chemical Substances § 721.3710 Polyether modified fatty acids (generic). (a) Chemical substance... Polyether modified fatty acids (PMN P-99-0435) is subject to reporting under this section for the...

Evaluation of modified titanium surfaces physical and chemical characteristics

NASA Astrophysics Data System (ADS)

Lukaszewska-Kuska, Magdalena; Leda, Bartosz; Gajdus, Przemyslaw; Hedzelek, Wieslaw

2017-11-01

Development of dental implantology is focused, among other things, on devising active surface of the implant, conditioning acceleration of the implant's integration with the bone. Increased roughness, characteristic for group of implants with developed surface, altered topography and chemically modified implant's surface determines increased implants stability. In this study four different titanium surfaces modifications: turned (TS); aluminium oxide-blasted (Al2O3); resorbable material blasted (RBM); sandblast and then etched with a mixture of acids (SAE), were evaluated in terms of surfaces topography and chemical composition prior to in vivo analysis. Topography analysis revealed two groups: one with smooth, anisotropic, undeveloped TS surface and the second group with remaining surfaces presenting rough, isotropic, developed surfaces with added during blasting procedure aluminium for Al2O3 and calcium and phosphorus for RBM. Physical and chemical modifications of titanium surface change its microstructure (typical for SAE) and increase its roughness (highest for Al2O3-blasted and RBM surfaces). The introduced modifications develop titanium surface - 10 times for SAE surfaces, 16 times for Al2O3-blasted surfaces, and 20 times for RBM surfaces.

Polyamide 6/chitosan nanofibers as support for the immobilization of Trametes versicolor laccase for the elimination of endocrine disrupting chemicals.

PubMed

Maryšková, Milena; Ardao, Inés; García-González, Carlos A; Martinová, Lenka; Rotková, Jana; Ševců, Alena

2016-07-01

In recent years, there has been an increase in efforts to improve wastewater treatment as the concentration of dangerous pollutants, such as endocrine disrupting chemicals, in wastewater increases. These compounds, which mimic the effect of hormones, have a negative impact on human health and are not easily removed from water. One way to effectively eliminate these pollutants is to use enzymatically activated materials. In this study, we report on the use of laccase from the white rot fungus Trametes versicolor immobilized onto polyamide 6/chitosan (PA6/CHIT) nanofibers modified using two different spacers (bovine serum albumin and hexamethylenediamine). We then tested the ability of the PA6/CHIT-laccase biocatalysts to eliminate a mixture containing 50μM of two endocrine disrupting chemicals: bisphenol A and 17α-ethinylestradiol. The PA6/CHIT nanofiber matrix used in this study not only proved to be a suitable carrier for immobilized and modified laccase but was also efficient in the removal of a mixture of endocrine disrupting chemicals in three treatment cycles. Copyright © 2016 Elsevier Inc. All rights reserved.

40 CFR 372.20 - Process for modifying covered chemicals and facilities.

Code of Federal Regulations, 2013 CFR

2013-07-01

... chemicals and facilities. 372.20 Section 372.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SUPERFUND, EMERGENCY PLANNING, AND COMMUNITY RIGHT-TO-KNOW PROGRAMS TOXIC CHEMICAL RELEASE REPORTING: COMMUNITY RIGHT-TO-KNOW Reporting Requirements § 372.20 Process for modifying covered chemicals...

Ethoxyresorufin-O-deethylase (EROD) activity in fish as a biomarker of chemical exposure

USGS Publications Warehouse

Whyte, J.J.; Jung, R.E.; Schmitt, C.J.; Tillitt, D.E.

2000-01-01

This review compiles and evaluates existing scientific information on the use, limitations, and procedural considerations for EROD activity (a catalytic measurement of cytochrome P4501A induction) as a biomarker in fish. A multitude of chemicals induce EROD activity in a variety of fish species, the most potent inducers being structural analogs of 2,3,7,8-tetracholordibenzo-p-dioxin. Although certain chemicals may inhibit EROD induction/activity, this interference is generally not a drawback to the use of EROD induction as a biomarker. The various methods of EROD analysis currently in use yield comparable results, particularly when data are expressed as relative rates of EROD activity. EROD induction in fish is well characterized, the most important modifying factors being fish species, reproductive status and age, all of which can be controlled through proper study design. Good candidate species for biomonitoring should have a wide range between basal and induced EROD activity (e.g., common carp, channel catfish, and mummichog). EROD activity has proven value as a biomarker in a number of field investigations of bleached kraft mill and industrial effluents, contaminated sediments, and chemical spills. Research on mechanisms of CYP1A-induced toxicity suggests that EROD activity may not only indicate chemical exposure, but also may also precede effects at various levels of biological organization. A current research need is the development of chemical exposure-response relationships for EROD activity in fish. In addition, routine reporting in the literature of EROD activity in standard positive and negative control material will enhance confidence in comparing results from different studies using this biomarker.

Investigation of a Modified 9Cr-1Mo (P91) Pipe Failure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klueh, Ronald L; Shingledecker, John P

2006-04-01

A modified 9Cr-1Mo feedwater (condensate) line at an Eastman Chemical Company plant failed in January 2005. The line was in continuous service since start-up December 2001 until failure. The Plant Superintendent estimated there were three thermal cycles since start-up, although there may have been as many as 25 thermal cycles during commissioning. Normal operating temperature was 325 F (163 C) and pressure was 1762 psig. The line was steam traced with the tracing activated only when ambient outdoor temperature dropped to 40 F (5 C). A modified 9Cr-1Mo steel (P91) pipe failure in a feedwater line in a chemical plantmore » was investigated. The failure occurred in the vicinity of an elbow produced with socket welds of the pipe to the elbow. Based on metallography and hardness measurements, it was concluded that failure occurred because of an improper post-weld heat treatment of the socket weldment.« less

Postharvest evaluation of soilless-grown table grape during storage in modified atmosphere.

PubMed

Cefola, Maria; Pace, Bernardo; Buttaro, Donato; Santamaria, Pietro; Serio, Francesco

2011-09-01

Soilless growth systems, developed mainly for vegetables and ornamental crops, have also been used recently as an alternative to soil culture for table grape in order to achieve optimal production performance. In this study, sensory, physical and chemical parameters were analysed in table grapes obtained from soil and soilless growth systems at harvest and during storage in air or modified atmosphere. At harvest, soilless-grown berries were 30% firmer than those grown in soil. Moreover, they showed 60% higher antioxidant activity and total phenol content than soil-grown fruits. Modified atmosphere storage resulted in a better quality of table grapes compared with those stored in air. Furthermore, soilless growth was more suitable than soil growth for preserving visual quality and controlling rachis browning and weight loss. Since the soilless system produces berries that are cleaner and of higher quality than those grown in soil, the implementation of soilless growth for the production of health-promoting and convenience fruits is suggested. Copyright © 2011 Society of Chemical Industry.

Evaluation of Foaming Performance of Bitumen Modified with the Addition of Surface Active Agent

NASA Astrophysics Data System (ADS)

Chomicz-Kowalska, Anna; Mrugała, Justyna; Maciejewski, Krzysztof

2017-10-01

The article presents the analysis of the performance of foamed bitumen modified using surface active agents. Although, bitumen foaming permits production of asphalt concrete and other asphalt mix types without using chemical additives in significantly reduced temperatures, the decrease in processing temperatures still impacts the adhesion performance and bitumen coating of aggregates in final mixes. Therefore, in some cases it may be feasible to incorporate adhesion promoters and surface active agents into warm and half-warm mixes with foamed bitumen to increase their service life and resilience. Because of the various nature of the available surface active agents, varying bitumen compatibility and their possible impact on the rheological properties of bitumen, the introduction of surface active agents may significantly alter the bitumen foaming performance. The tests included basic performance tests of bitumen before and after foaming. The two tested bitumen were designated as 35/50 and 50/70 penetration grade binders, which were modified with a surface active agent widely used for improving mixture workability, compactibility and adhesion in a wide range of asphalt mixes and techniques, specifically Warm Mix Asphalt. Alongside to the reference unmodified bitumen, binders with 0.2%, 0.4% and 0.6% surface active agent concentration were tested. The analysis has shown a positive influence of the modifier on the foaming performance of both of the base bitumen increasing their maximum expansion ratio and bitumen foam halflife. In the investigations, it was found that the improvement was dependent on the bitumen type and modifier content. The improved expansion ratio and foam half-life has a positive impact on the aggregate coating and adhesion, which together with the adhesion promoting action of the modifier will have a combined positive effect on the quality of produced final asphalt mixes.

Biological resistance of polyethylene composites made with chemically modified fiber or flour

Treesearch

Rebecca E. Ibach; Craig M. Clemons

2002-01-01

The role of moisture in the biological decay of wood-plastic composites was investigated. Southern pine wood fiber and ponderosa pine wood flour were chemically modified using either acetic anhydride (AA), butylene oxide (BO), or propylene oxide (PO). A 50:50 mixture of high density polyethylene and either chemically modified fiber or flour, or untreated fiber or flour...

Artificial specific binders directly recovered from chemically modified nucleic acid libraries.

PubMed

Kasahara, Yuuya; Kuwahara, Masayasu

2012-01-01

Specific binders comprised of nucleic acids, that is, RNA/DNA aptamers, are attractive functional biopolymers owing to their potential broad application in medicine, food hygiene, environmental analysis, and biological research. Despite the large number of reports on selection of natural DNA/RNA aptamers, there are not many examples of direct screening of chemically modified nucleic acid aptamers. This is because of (i) the inferior efficiency and accuracy of polymerase reactions involving transcription/reverse-transcription of modified nucleotides compared with those of natural nucleotides, (ii) technical difficulties and additional time and effort required when using modified nucleic acid libraries, and (iii) ambiguous efficacies of chemical modifications in binding properties until recently; in contrast, the effects of chemical modifications on biostability are well studied using various nucleotide analogs. Although reports on the direct screening of a modified nucleic acid library remain in the minority, chemical modifications would be essential when further functional expansion of nucleic acid aptamers, in particular for medical and biological uses, is considered. This paper focuses on enzymatic production of chemically modified nucleic acids and their application to random screenings. In addition, recent advances and possible future research are also described.

Plant Sterols: Chemical and Enzymatic Structural Modifications and Effects on Their Cholesterol-Lowering Activity.

PubMed

He, Wen-Sen; Zhu, Hanyue; Chen, Zhen-Yu

2018-03-28

Plant sterols have attracted increasing attention due to their excellent cholesterol-lowering activity. However, free plant sterols have some characteristics of low oil solubility, water insolubility, high melting point, and low bioavailability, which greatly limit their application in foods. Numerous studies have been undertaken to modify their chemical structures to improve their chemical and physical properties in meeting the needs of various applications. The present review is to summarize the literature and update the progress on structural modifications of plant sterols in the following aspects: (i) synthesis of plant sterol esters by esterification and transesterification with hydrophobic fatty acids and triacylglycerols to improve their oil solubility, (ii) synthesis of plant sterol derivatives by coupling with various hydrophilic moieties to enhance their water solubility, and (iii) mechanisms by which plant sterols reduce plasma cholesterol and the effect of structural modifications on plasma cholesterol-lowering activity of plant sterols.

Applicability of Vacuum Impregnation to Modify Physico-Chemical, Sensory and Nutritive Characteristics of Plant Origin Products—A Review

PubMed Central

Radziejewska-Kubzdela, Elżbieta; Biegańska-Marecik, Róża; Kidoń, Marcin

2014-01-01

Vacuum impregnation is a non-destructive method of introducing a solution with a specific composition to the porous matrices of fruit and vegetables. Mass transfer in this process is a result of mechanically induced differences in pressure. Vacuum impregnation makes it possible to fill large volumes of intercellular spaces in tissues of fruit and vegetables, thus modifying physico-chemical properties and sensory attributes of products. This method may be used, e.g., to reduce pH and water activity of the product, change its thermal properties, improve texture, color, taste and aroma. Additionally, bioactive compounds may be introduced together with impregnating solutions, thus improving health-promoting properties of the product or facilitating production of functional food. PMID:25244012

In vitro evolution of chemically-modified nucleic acid aptamers: Pros and cons, and comprehensive selection strategies.

PubMed

Lipi, Farhana; Chen, Suxiang; Chakravarthy, Madhuri; Rakesh, Shilpa; Veedu, Rakesh N

2016-12-01

Nucleic acid aptamers are single-stranded DNA or RNA oligonucleotide sequences that bind to a specific target molecule with high affinity and specificity through their ability to adopt 3-dimensional structure in solution. Aptamers have huge potential as targeted therapeutics, diagnostics, delivery agents and as biosensors. However, aptamers composed of natural nucleotide monomers are quickly degraded in vivo and show poor pharmacodynamic properties. To overcome this, chemically-modified nucleic acid aptamers are developed by incorporating modified nucleotides after or during the selection process by Systematic Evolution of Ligands by EXponential enrichment (SELEX). This review will discuss the development of chemically-modified aptamers and provide the pros and cons, and new insights on in vitro aptamer selection strategies by using chemically-modified nucleic acid libraries.

In vitro evolution of chemically-modified nucleic acid aptamers: Pros and cons, and comprehensive selection strategies

PubMed Central

Chen, Suxiang; Chakravarthy, Madhuri; Rakesh, Shilpa; Veedu, Rakesh N.

2016-01-01

ABSTRACT Nucleic acid aptamers are single-stranded DNA or RNA oligonucleotide sequences that bind to a specific target molecule with high affinity and specificity through their ability to adopt 3-dimensional structure in solution. Aptamers have huge potential as targeted therapeutics, diagnostics, delivery agents and as biosensors. However, aptamers composed of natural nucleotide monomers are quickly degraded in vivo and show poor pharmacodynamic properties. To overcome this, chemically-modified nucleic acid aptamers are developed by incorporating modified nucleotides after or during the selection process by Systematic Evolution of Ligands by EXponential enrichment (SELEX). This review will discuss the development of chemically-modified aptamers and provide the pros and cons, and new insights on in vitro aptamer selection strategies by using chemically-modified nucleic acid libraries. PMID:27715478

Investigations on dendrimer space reveal solid and liquid tumor growth-inhibition by original phosphorus-based dendrimers and the corresponding monomers and dendrons with ethacrynic acid motifs.

PubMed

El Brahmi, Nabil; Mignani, Serge M; Caron, Joachim; El Kazzouli, Saïd; Bousmina, Mosto M; Caminade, Anne-Marie; Cresteil, Thierry; Majoral, Jean-Pierre

2015-03-07

The well-known reactive diuretic ethacrynic acid (EA, Edecrin), with low antiproliferative activities, was chemically modified and grafted onto phosphorus dendrimers and the corresponding simple branched phosphorus dendron-like derivatives affording novel nanodevices showing moderate to strong antiproliferative activities against liquid and solid tumor cell lines, respectively.

40 CFR 721.10044 - Metal oxide, modified with alkyl and vinyl terminated polysiloxanes (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Metal oxide, modified with alkyl and... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10044 Metal oxide, modified with alkyl... to reporting. (1) The chemical substance identified generically as metal oxide, modified with alkyl...

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Modified polymer of vinyl acetate and... Significant New Uses for Specific Chemical Substances § 721.8658 Modified polymer of vinyl acetate and.... (1) The chemical substance identified generically as modified polymer of vinyl acetate and quaternary...

Synthesis and physico-chemical characterization of modified starches from banana (Musa AAB) and its biological activities in diabetic rats.

PubMed

Reddy, Chagam Koteswara; Suriya, M; Vidya, P V; Haripriya, Sundaramoorthy

2017-01-01

This study describes a simple method of preparation and physico-chemical properties of modified starches (type-3 resistant starches) from banana (Musa AAB), and the modified starches investigated as functional food with a beneficial effect on type-2 diabetes. RS3 was prepared using a method combined with debranching modification and physical modification; native and modifies starches were characterized by scanning electron microscope (SEM), powder X-ray diffraction (XRD), differential scanning calorimetry (DSC) and rapid visco analyzer (RVA). Use of the enzymatic and physical modification methodology, improved the yield of RS (26.62%) from Musa AAB. A reduced viscosity and swelling power; increased transition temperatures, water absorption capacity and solubility index with B-type crystalline pattern and loss of granular appearance were observed during the debranching modification and physical modification. The modified starches exhibited beneficial health effects in diabetic and HFD rats who consumed it. These results recommend that dietary feeding of RS3 was effective in the regulation of glucose and lipid profile in serum and suppressing the oxidative stress in rats under diabetic and HFD condition. This current study provides new bioactive starches, with potential applications in the food and non-food industries. Copyright © 2016 Elsevier B.V. All rights reserved.

Modified Separator Performing Dual Physical/Chemical Roles to Inhibit Polysulfide Shuttle Resulting in Ultrastable Li-S Batteries.

PubMed

Abbas, Syed Ali; Ding, Jiang; Wu, Sheng Hui; Fang, Jason; Boopathi, Karunakara Moorthy; Mohapatra, Anisha; Lee, Li Wei; Wang, Pen-Cheng; Chang, Chien-Cheng; Chu, Chih Wei

2017-12-26

In this paper we describe a modified (AEG/CH) coated separator for Li-S batteries in which the shuttling phenomenon of the lithium polysulfides is restrained through two types of interactions: activated expanded graphite (AEG) flakes interacted physically with the lithium polysulfides, while chitosan (CH), used to bind the AEG flakes on the separator, interacted chemically through its abundance of amino and hydroxyl functional groups. Moreover, the AEG flakes facilitated ionic and electronic transfer during the redox reaction. Live H-cell discharging experiments revealed that the modified separator was effective at curbing polysulfide shuttling; moreover, X-ray photoelectron spectroscopy analysis of the cycled separator confirmed the presence of lithium polysulfides in the AEG/CH matrix. Using this dual functional interaction approach, the lifetime of the pure sulfur-based cathode was extended to 3000 cycles at 1C-rate (1C = 1670 mA/g), decreasing the decay rate to 0.021% per cycle, a value that is among the best reported to date. A flexible battery based on this modified separator exhibited stable performance and could turn on multiple light-emitting diodes. Such modified membranes with good mechanical strength, high electronic conductivity, and anti-self-discharging shield appear to be a scalable solution for future high-energy battery systems.

Role of Disulfide Bridges in the Activity and Stability of a Cold-Active α-Amylase

PubMed Central

Siddiqui, Khawar Sohail; Poljak, Anne; Guilhaus, Michael; Feller, Georges; D'Amico, Salvino; Gerday, Charles; Cavicchioli, Ricardo

2005-01-01

The cold-adapted α-amylase from Pseudoalteromonas haloplanktis unfolds reversibly and cooperatively according to a two-state mechanism at 30°C and unfolds reversibly and sequentially with two transitions at temperatures below 12°C. To examine the role of the four disulfide bridges in activity and conformational stability of the enzyme, the eight cysteine residues were reduced with β-mercaptoethanol or chemically modified using iodoacetamide or iodoacetic acid. Matrix-assisted laser desorption-time of flight mass spectrometry analysis confirmed that all of the cysteines were modified. The iodoacetamide-modified enzyme reversibly folded/unfolded and retained approximately one-third of its activity. Removal of all disulfide bonds resulted in stabilization of the least stable region of the enzyme (including the active site), with a concomitant decrease in activity (increase in activation enthalpy). Disulfide bond removal had a greater impact on enzyme activity than on stability (particularly the active-site region). The functional role of the disulfide bridges appears to be to prevent the active site from developing ionic interactions. Overall, the study demonstrated that none of the four disulfide bonds are important in stabilizing the native structure of enzyme, and instead, they appear to promote a localized destabilization to preserve activity. PMID:16109962

Role of growth media and chemical enhancers in secondary metabolites production from Aspergillus carbonarius (NRL-369) and their pharmaceutical potentials.

PubMed

Khan, Abid Ali; Bacha, Nafess; Ahmad, Bashir; Cox, R J; Bakht, Jehan

2016-07-01

The present study investigates the effect of different growth media and chemical enhancer on silent genes in Aspergillus carbonarius (NRL-369) for secondary metabolites production and its in vitro biological activities. Results revealed that Aspergillus carbonarius (NRL-369) grown in Czapeak yeast extract broth medium produced more metabolites compared with other media. Chemical epigenetic modifiers (suberoyl-anilide hydroxamic acid (SAHA) and 5-azacytidine (5-AZA) at concentration of 15mM were effective for the expression of silent genes resulting in increased secondary metabolites production. Secondary metabolites extracted in ethyl acetate and fractionized in n-Hexane showed variable degree of growth inhibitions of the tested microorganisms. Similarly, these samples were also active against brine shrimps and Lemna.

Process for making polymers comprising derivatized carbon nanotubes and compositions thereof

NASA Technical Reports Server (NTRS)

Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

2007-01-01

The present invention incorporates new processes for blending derivatized carbon nanotubes into polymer matrices to create new polymer/composite materials. When modified with suitable chemical groups using diazonium chemistry, the nanotubes can be made chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as mechanical strength) to the properties of the composite material as a whole. To achieve this, the derivatized (modified) carbon nanotubes are physically blended with the polymeric material, and/or, if desired, allowed to react at ambient or elevated temperature. These methods can be utilized to append functionalities to the nanotubes that will further covalently bond to the host polymer matrix, or directly between two tubes themselves. Furthermore, the nanotubes can be used as a generator of polymer growth, wherein the nanotubes are derivatized with a functional group that is an active part of a polymerization process, which would also result in a composite material in which the carbon nanotubes are chemically involved.

The effect on biological and moisture resistance of epichlorohydrin chemically modified wood

Treesearch

Rebecca E. Ibach; Beom-Goo Lee

2002-01-01

Southern pine solid wood and fiber were chemically modified with epichlorohydrin to help in understanding the role of moisture in the mechanism of biological effectiveness of chemically modified wood. The solid wood had weight gains from 11% to 34%, while the fiber had weight gains from 9% to 75%. After modification, part of the specimens were water leached for 2 weeks...

A Simple Method for High Throughput Chemical Screening in Caenorhabditis Elegans

PubMed Central

Lucanic, Mark; Garrett, Theo; Gill, Matthew S.; Lithgow, Gordon J.

2018-01-01

Caenorhabditis elegans is a useful organism for testing chemical effects on physiology. Whole organism small molecule screens offer significant advantages for identifying biologically active chemical structures that can modify complex phenotypes such as lifespan. Described here is a simple protocol for producing hundreds of 96-well culture plates with fairly consistent numbers of C. elegans in each well. Next, we specified how to use these cultures to screen thousands of chemicals for effects on the lifespan of the nematode C. elegans. This protocol makes use of temperature sensitive sterile strains, agar plate conditions, and simple animal handling to facilitate the rapid and high throughput production of synchronized animal cultures for screening. PMID:29630057

siRNAmod: A database of experimentally validated chemically modified siRNAs.

PubMed

Dar, Showkat Ahmad; Thakur, Anamika; Qureshi, Abid; Kumar, Manoj

2016-01-28

Small interfering RNA (siRNA) technology has vast potential for functional genomics and development of therapeutics. However, it faces many obstacles predominantly instability of siRNAs due to nuclease digestion and subsequently biologically short half-life. Chemical modifications in siRNAs provide means to overcome these shortcomings and improve their stability and potency. Despite enormous utility bioinformatics resource of these chemically modified siRNAs (cm-siRNAs) is lacking. Therefore, we have developed siRNAmod, a specialized databank for chemically modified siRNAs. Currently, our repository contains a total of 4894 chemically modified-siRNA sequences, comprising 128 unique chemical modifications on different positions with various permutations and combinations. It incorporates important information on siRNA sequence, chemical modification, their number and respective position, structure, simplified molecular input line entry system canonical (SMILES), efficacy of modified siRNA, target gene, cell line, experimental methods, reference etc. It is developed and hosted using Linux Apache MySQL PHP (LAMP) software bundle. Standard user-friendly browse, search facility and analysis tools are also integrated. It would assist in understanding the effect of chemical modifications and further development of stable and efficacious siRNAs for research as well as therapeutics. siRNAmod is freely available at: http://crdd.osdd.net/servers/sirnamod.

Restricting detergent protease action to surface of protein fibres by chemical modification.

PubMed

Schroeder, M; Lenting, H B M; Kandelbauer, A; Silva, C J S M; Cavaco-Paulo, A; Gübitz, G M

2006-10-01

Due to their excellent properties, such as thermostability, activity over a broad range of pH and efficient stain removal, proteases from Bacillus sp. are commonly used in the textile industry including industrial processes and laundry and represent one of the most important groups of enzymes. However, due to the action of proteases, severe damage on natural protein fibres such as silk and wool result after washing with detergents containing proteases. To include the benefits of proteases in a wool fibre friendly detergent formulation, the soluble polymer polyethylene glycol (PEG) was covalently attached to a protease from Bacillus licheniformis. In contrast to activation of PEG with cyanuric chloride (50%) activation with 1,1'-carbonyldiimidazole (CDI) lead to activity recovery above 90%. With these modified enzymes, hydrolytic attack on wool fibres could be successfully prevented up to 95% compared to the native enzymes. Colour difference (DeltaE) measured in the three dimensional colour space showed good stain removal properties for the modified enzymes. Furthermore, half-life of the modified enzymes in buffers and commercial detergents solutions was nearly twice as high as those of the non-modified enzymes with values of up to 63 min. Out of the different modified proteases especially the B. licheniformis protease with the 2.0-kDa polymer attached both retained stain removal properties and did not hydrolyse/damage wool fibres.

Different Interfacial Behaviors of N- and C-Terminus Cysteine-Modified Cecropin P1 Chemically Immobilized onto Polymer Surface

DTIC Science & Technology

2013-08-06

naturally occurring antimicrobial peptides (AMPs) have been studied as an alternative with a broad range of activity and binding affinity toward...microorganisms.10−16 For example, chemically immo- bilized cecropin P1, cecropin A, cecropin B, and other antimicrobial peptides have demonstrated promise for...Autom. 2006, 11 (6), 341−351. (10) Gregory, K.; Mello, C. M. Immobilization of Escherichia coli cells by use of the antimicrobial peptide cecropin P1

The Pathfinder Microrover

NASA Technical Reports Server (NTRS)

Matijevic, J. R.; Bickler, D. B.; Braun, D. F.; Eisen, H. J.; Matthies, L. H.; Mishkin, A. H.; Stone, H. W.; van Nieuwstadt, L. M.; Wen, L. C.; Wilcox, B. H.;

ACTIVATION AND REACTIVITY OF NOVEL CALCIUM-BASED SORBENTS FOR DRY SO2 CONTROL IN BOILERS

EPA Science Inventory

Chemically modified calcium hydroxide (Ca(OH)2) sorbents developed in the U.S. Environmental Protection Agency's Air and Energy Engineering Research Laboratory (AEERL) for sulfur dioxide (SO2) control in utility boilers were tested in an electrically heated, bench-scale isotherma...

Surprising Alteration of Antibacterial Activity of 5″-Modified Neomycin against Resistant Bacteria

PubMed Central

Zhang, Jianjun; Chiang, Fang-I; Wu, Long; Czyryca, Przemyslaw Greg; Li, Ding; Chang, Cheng-Wei Tom

2009-01-01

A facile synthetic protocol for the production of neomycin B derivatives with various modifications at the 5″ position has been developed. Structural activity relationship (SAR) against aminoglycoside resistant bacteria equipped with various aminoglycoside-modifying enzymes (AME's) was investigated. Enzymatic and molecular modeling studies reveal that the superb substrate promiscuity of AME's allows the resistant bacteria to cope with diverse structural modifications despite the observation that several derivatives show enhanced antibacterial activity than the parent neomycin. Surprisingly, when testing synthetic neomycin derivatives against other human pathogens, two leads exhibit prominent activity against both Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) that are known to exert high level of resistance against clinically used aminoglycosides. These findings can be extremely useful in developing new aminoglycoside antibiotics against resistant bacteria. Our result also suggests that new biological and antimicrobial activities can be obtained by chemical modifications of old drugs. PMID:19012394

Layer-by-layer structured polysaccharides-based multilayers on cellulose acetate membrane: Towards better hemocompatibility, antibacterial and antioxidant activities

NASA Astrophysics Data System (ADS)

Peng, Lincai; Li, Hui; Meng, Yahong

2017-04-01

The development of multifunctional cellulose acetate (CA) membranes with enhanced hemocompatibility and antibacterial and antioxidant activities is extremely important for biomedical applications. In this work, significant improvements in hemocompatibility and antibacterial and antioxidant activities of cellulose acetate (CA) membranes were achieved via layer-by-layer (LBL) deposition of chitosan (CS) and water-soluble heparin-mimicking polysaccharides (i.e., sulfated Cantharellus cibarius polysaccharides, SCP) onto their surface. The surface chemical compositions, growth manner, surface morphologies, and wetting ability of CS/SCP multilayer-modified CA membranes were characterized, respectively. The systematical evaluation of hemocompatibility revealed that CS/SCP multilayer-modified CA membranes significantly improved blood compatibility including resistance to non-specific protein adsorption, suppression of platelet adhesion and activation, prolongation of coagulation times, inhibition of complement activation, as well as reduction in blood hemolysis. Meanwhile, CS/SCP multilayer-modified CA membranes exhibited strong growth inhibition against Escherichia coli and Staphylococcus aureus, as well as high scavenging abilities against superoxide and hydroxyl radicals. In summary, the CS/SCP multilayers could confer CA membranes with integrated hemocompatibility and antibacterial and antioxidant activities, which might have great potential application in the biomedical field.

40 CFR 721.10151 - Modified styrene, divinylbenzene polymer (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... polymer (generic). 721.10151 Section 721.10151 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10151 Modified styrene, divinylbenzene polymer (generic). (a) Chemical... as modified styrene, divinylbenzene polymer (PMN P-07-642) is subject to reporting under this section...

40 CFR 721.10151 - Modified styrene, divinylbenzene polymer (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... polymer (generic). 721.10151 Section 721.10151 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10151 Modified styrene, divinylbenzene polymer (generic). (a) Chemical... as modified styrene, divinylbenzene polymer (PMN P-07-642) is subject to reporting under this section...

40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this section...

40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this section...

40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this section...

40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this section...

40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this section...

40 CFR 721.10151 - Modified styrene, divinylbenzene polymer (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... polymer (generic). 721.10151 Section 721.10151 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10151 Modified styrene, divinylbenzene polymer (generic). (a) Chemical... as modified styrene, divinylbenzene polymer (PMN P-07-642) is subject to reporting under this section...

40 CFR 721.10151 - Modified styrene, divinylbenzene polymer (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... polymer (generic). 721.10151 Section 721.10151 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10151 Modified styrene, divinylbenzene polymer (generic). (a) Chemical... as modified styrene, divinylbenzene polymer (PMN P-07-642) is subject to reporting under this section...

40 CFR 721.10151 - Modified styrene, divinylbenzene polymer (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... polymer (generic). 721.10151 Section 721.10151 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10151 Modified styrene, divinylbenzene polymer (generic). (a) Chemical... as modified styrene, divinylbenzene polymer (PMN P-07-642) is subject to reporting under this section...

Modified bamboo rayon-copper nanoparticle composites as antibacterial textiles.

PubMed

Teli, M D; Sheikh, Javed

2013-10-01

In the current study the bamboo rayon fabric grafted with acrylamide was utilized as a backbone to immobilize copper nanoprticles. The grafted bamboo rayon was first treated with CuSO4 followed by chemical reduction. The modified product was characterized using FTIR, TGA and SEM. The characteristic color developed after reduction was measured spectrophotometrically. The grafted bamboo rayon with Cu nanoparticles was then evaluated for antibacterial activity against both gram positive and gram negative bacteria and the durability of their antibacterial activity after washing. The product showed antibacterial activity against both types of bacterias which was found to be durable till 50 washes. The material can be claimed as suitable candidate for medical textile applications to prevent cross-infections. Copyright © 2013 Elsevier B.V. All rights reserved.

Chemically modified graphene based supercapacitors for flexible and miniature devices

NASA Astrophysics Data System (ADS)

Ghosh, Debasis; Kim, Sang Ouk

2015-09-01

Rapid progress in the portable and flexible electronic devises has stimulated supercapacitor research towards the design and fabrication of high performance flexible devices. Recent research efforts for flexible supercapacitor electrode materials are highly focusing on graphene and chemically modified graphene owing to the unique properties, including large surface area, high electrical and thermal conductivity, excellent mechanical flexibility, and outstanding chemical stability. This invited review article highlights current status of the flexible electrode material research based on chemically modified graphene for supercapacitor application. A variety of electrode architectures prepared from chemically modified graphene are summarized in terms of their structural dimensions. Novel prototypes for the supercapacitor aiming at flexible miniature devices, i.e. microsupercapacitor with high energy and power density are highlighted. Future challenges relevant to graphene-based flexible supercapacitors are also suggested. [Figure not available: see fulltext.

Single-neuron identification of chemical constituents, physiological changes, and metabolism using mass spectrometry.

PubMed

Zhu, Hongying; Zou, Guichang; Wang, Ning; Zhuang, Meihui; Xiong, Wei; Huang, Guangming

2017-03-07

The use of single-cell assays has emerged as a cutting-edge technique during the past decade. Although single-cell mass spectrometry (MS) has recently achieved remarkable results, deep biological insights have not yet been obtained, probably because of various technical issues, including the unavoidable use of matrices, the inability to maintain cell viability, low throughput because of sample pretreatment, and the lack of recordings of cell physiological activities from the same cell. In this study, we describe a patch clamp/MS-based platform that enables the sensitive, rapid, and in situ chemical profiling of single living neurons. This approach integrates modified patch clamp technique and modified MS measurements to directly collect and detect nanoliter-scale samples from the cytoplasm of single neurons in mice brain slices. Abundant possible cytoplasmic constituents were detected in a single neuron at a relatively fast rate, and over 50 metabolites were identified in this study. The advantages of direct, rapid, and in situ sampling and analysis enabled us to measure the biological activities of the cytoplasmic constituents in a single neuron, including comparing neuron types by cytoplasmic chemical constituents; observing changes in constituent concentrations as the physiological conditions, such as age, vary; and identifying the metabolic pathways of small molecules.

Single-neuron identification of chemical constituents, physiological changes, and metabolism using mass spectrometry

PubMed Central

Zhu, Hongying; Zou, Guichang; Wang, Ning; Zhuang, Meihui; Xiong, Wei; Huang, Guangming

2017-01-01

The use of single-cell assays has emerged as a cutting-edge technique during the past decade. Although single-cell mass spectrometry (MS) has recently achieved remarkable results, deep biological insights have not yet been obtained, probably because of various technical issues, including the unavoidable use of matrices, the inability to maintain cell viability, low throughput because of sample pretreatment, and the lack of recordings of cell physiological activities from the same cell. In this study, we describe a patch clamp/MS-based platform that enables the sensitive, rapid, and in situ chemical profiling of single living neurons. This approach integrates modified patch clamp technique and modified MS measurements to directly collect and detect nanoliter-scale samples from the cytoplasm of single neurons in mice brain slices. Abundant possible cytoplasmic constituents were detected in a single neuron at a relatively fast rate, and over 50 metabolites were identified in this study. The advantages of direct, rapid, and in situ sampling and analysis enabled us to measure the biological activities of the cytoplasmic constituents in a single neuron, including comparing neuron types by cytoplasmic chemical constituents; observing changes in constituent concentrations as the physiological conditions, such as age, vary; and identifying the metabolic pathways of small molecules. PMID:28223513

Modified fly ash from municipal solid waste incineration as catalyst support for Mn-Ce composite oxides

NASA Astrophysics Data System (ADS)

Chen, Xiongbo; Liu, Ying; Yang, Ying; Ren, Tingyan; Pan, Lang; Fang, Ping; Chen, Dingsheng; Cen, Chaoping

2017-08-01

Fly ash from municipal solid waste incineration was modified by hydrothermal treatment and used as catalyst support for Mn-Ce composite oxides. The prepared catalyst showed good activity for the selective catalytic reduction (SCR) of NO by NH3. A NO conversion of 93% could be achieved at 300 °C under a GHSV of 32857 h-1. With the help of characterizations including XRD, BET, SEM, TEM, XPS and TPR, it was found that hydrothermal treatment brought a large surface area and abundant mesoporous to the modified fly ash, and Mn-Ce composite oxides were highly dispersed on the surface of the support. These physical and chemical properties were the intrinsic reasons for the good SCR activity. This work transformed fly ash into high value-added products, providing a new approach to the resource utilization and pollution control of fly ash.

Phenol metabolism and preservation of fresh in-hull walnut stored in modified atmosphere packaging.

PubMed

Wang, Jin; Li, Pan; Gong, Bi; Li, Shuying; Ma, Huiling

2017-12-01

The effects of modified atmosphere packaging (MAP) on phenol metabolism and preservation of fresh in-hull walnuts have been investigated. Fruit was packaged under MAP1 (film thickness, 30 μm), MAP2 (45 μm) and MAP3 (50 μm) and stored at -0.5 to 1.0 °C for up to 60 days. Firmness, soluble solid concentration, total phenols, total flavonoids and total antioxidant activity of the green hull were maintained at higher levels under the MAP conditions, whereas decay incidence was lower compared to the control during storage. Green hull of fruit under MAP conditions contained lower polyphenol oxidase activity than the control and the peroxidase activity was at a similar level to the control after 18 days. Phenylalanine ammonialyase activity was enhanced by MAP conditions, with two peaks on days 18 and 36. Until day 60, the peroxide value and acid value of kernel oils under MAP conditions were lower than that of the control. The MAP3 treatment was most effective for maintaining kernel quality. The protective role of MAP conditions on phenolic contents in green hull may contribute to the mitigation of decay and the maintenance of kernel quality. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Identification of Lilial as a fragrance sensitizer in a perfume by bioassay-guided chemical fractionation and structure-activity relationships.

PubMed

Arnau, E G; Andersen, K E; Bruze, M; Frosch, P J; Johansen, J D; Menné, T; Rastogi, S C; White, I R; Lepoittevin, J P

2000-12-01

Fragrance materials are among the most common causes of allergic contact dermatitis. The aim of this study was to identify in a perfume fragrance allergens not included in the fragrance mix, by use of bioassay-guided chemical fractionation and chemical analysis/structure-activity relationships (SARs). The basis for the investigation was a 45-year-old woman allergic to her own perfume. She had a negative patch test to the fragrance mix and agreed to participate in the study. Chemical fractionation of the perfume concentrate was used for repeated patch testing and/or repeated open application test on the pre-sensitized patient. The chemical composition of the fractions giving a positive patch-test response and repeated open application test reactions was obtained by gas chromatography-mass spectrometry. From the compounds identified, those that contained a "structural alert" in their chemical structure, indicating an ability to modify skin proteins and thus behave as a skin sensitizer, were tested on the patient. The patient reacted positively to the synthetic fragrance p-t-butyl-alpha-methylhydrocinnamic aldehyde (Lilial), a widely used fragrance compound not present in the fragrance mix. The combination of bioassay-guided chemical fractionation and chemical analysis/structure-activity relationships seems to be a valuable tool for the investigation of contact allergy to fragrance materials.

Investigation of the influence of coolant-lubricant modification on selected effects of pull broaching

NASA Astrophysics Data System (ADS)

Adamczuk, Krzysztof; Legutko, Stanisław; Laber, Alicja; Serwa, Wojciech

2017-10-01

The paper presents the results of testing the wear of the tool (pull broach) and a gear wheel splineway surface roughness after the friction node of pull broach/gear wheel (CuSn12Ni2) had been lubricated with metal machining oil and the same oil modified with chemically active exploitation additive. To designate the influence of modifying metal machining oil by the exploitation additive on the lubricating properties, anti-wear and antiseizure indicators have been appointed. Exploitation tests have proved purposefulness of modifying metal machining oil. Modification of the lubricant has contributed to reduction of the wear of the tools - pull broaches and to reduction of roughness of the splineway surfaces.

Iron phthalocyanine modified mesoporous titania nanoparticles for photocatalytic activity and CO2 capture applications.

PubMed

Ramacharyulu, P V R K; Muhammad, Raeesh; Praveen Kumar, J; Prasad, G K; Mohanty, Paritosh

2015-10-21

An iron(II)phthalocyanine (Fepc) modified mesoporous titania (Fepc-TiO2) nanocatalyst with a specific surface area of 215 m(2) g(-1) has been synthesized by a hydrothermal method. Fepc-TiO2 degrades one of the highly toxic chemical warfare agents, sulfur mustard (SM), photocatalytically under sunlight with an exposure time of as low as 70 min. Furthermore, the mesoporous Fepc-TiO2 also captured 2.1 mmol g(-1) of CO2 at 273 K and 1 atm.

Surface-modified nanoparticles as anti-biofilm filler for dental polymers

PubMed Central

Zaltsman, Nathan; Ionescu, Andrei C.; Weiss, Ervin I.; Brambilla, Eugenio; Beyth, Shaul

2017-01-01

The objective of the study was to synthesis silica nanoparticles modified with (i) a tertiary amine bearing two t-cinnamaldehyde substituents or (ii) dimethyl-octyl ammonium, alongside the well-studied quaternary ammonium polyethyleneimine nanoparticles. These were to be evaluated for their chemical and mechanical properties, as well for antibacterial and antibiofilm activity. Samples were incorporated in commercial dental resin material and the degree of monomer conversion, mechanical strength, and water contact angle were tested to characterize the effect of the nanoparticles on resin material. Antibacterial activity was evaluated with the direct contact test and the biofilm inhibition test against Streptococcus mutans. Addition of cinnamaldehyde-modified particles preserved the degree of conversion and compressive strength of the base material and increased surface hydrophobicity. Quaternary ammonium functional groups led to a decrease in the degree of conversion and to low compressive strength, without altering the hydrophilic nature of the base material. In the direct contact test and the anti-biofilm test, the polyethyleneimine particles exhibited the strongest antibacterial effect. The cinnamaldehyde-modified particles displayed antibiofilm activity, silica particles with quaternary ammonium were ineffective. Immobilization of t-cinnamaldehyde onto a solid surface via amine linkers provided a better alternative to the well-known quaternary ammonium bactericides. PMID:29244848

Proximate mechanism of behavioral manipulation of an orb-weaver spider host by a parasitoid wasp

PubMed Central

Gonzaga, Marcelo Oliveira; de Oliveira, Leandro Licursi; Sperber, Carlos Frankl

2017-01-01

Some ichneumonid wasps induce modifications in the web building behavior of their spider hosts to produce resistant “cocoon” webs. These structures hold and protect the wasp’s cocoon during pupa development. The mechanism responsible for host manipulation probably involves the inoculation of psychotropic chemicals by the parasitoid larva during a specific developmental period. Recent studies indicate that some spiders build cocoon webs similar to those normally built immediately before ecdysis, suggesting that this substance might be a molting hormone or a precursor chemical of this hormone. Here, we report that Cyclosa spider species exhibiting modified behavior presented higher 20-OH-ecdysone levels than parasitized spiders acting normally or unparasitized individuals. We suggest that the lack of control that spiders have when constructing modified webs can be triggered by anachronic activation of ecdysis. PMID:28158280

Correlation between dynamic wetting behavior and chemical components of thermally modified wood

NASA Astrophysics Data System (ADS)

Wang, Wang; Zhu, Yuan; Cao, Jinzhen; Sun, Wenjing

2015-01-01

In order to investigate the dynamic wetting behavior of thermally modified wood, Cathay poplar (Populus cathayana Rehd.) and Scots pine (Pinus sylvestris L.) samples were thermally modified in an oven at 160, 180, 200, 220 or 240 °C for 4 h in this study. The dynamic contact angles and droplet volumes of water droplets on modified and unmodified wood surfaces were measured by sessile drop method, and their changing rates (expression index: K value and wetting slope) calculated by wetting models were illustrated for mapping the dynamic wetting process. The surface chemical components were also measured by X-ray photoelectron spectroscopy analysis (XPS), thus the relationship between dynamic wetting behavior and chemical components of thermally modified wood were determined. The results indicated that thermal modification was capable of decreasing the dynamic wettability of wood, expressed in lowing spread and penetration speed of water droplets on wood surfaces. This change was more obvious with the increased heating temperature. The K values varied linearly with the chemical components parameter (mass loss, O/C ratio, and C1/C2 ratio), indicating a strong correlation between dynamic wetting behavior and chemical components of thermally modified wood.

40 CFR 721.10533 - Amine-modified urea-formaldehyde polymer (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... polymer (generic). 721.10533 Section 721.10533 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10533 Amine-modified urea-formaldehyde polymer (generic). (a) Chemical... as amine-modified urea-formaldehyde polymer (PMN P-12-182) is subject to reporting under this section...

40 CFR 721.10533 - Amine-modified urea-formaldehyde polymer (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... polymer (generic). 721.10533 Section 721.10533 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10533 Amine-modified urea-formaldehyde polymer (generic). (a) Chemical... as amine-modified urea-formaldehyde polymer (PMN P-12-182) is subject to reporting under this section...

Conformational changes of a chemically modified HRP: formation of a molten globule like structure at pH 5

PubMed Central

Bamdad, Kourosh; Ranjbar, Bijan; Naderi-Manesh, Hossein; Sadeghi, Mehdi

2014-01-01

Horseradish peroxidase is an all alpha-helical enzyme, which widely used in biochemistry applications mainly because of its ability to enhance the weak signals of target molecules. This monomeric heme-containing plant peroxidase is also used as a reagent for the organic synthesis, biotransformation, chemiluminescent assays, immunoassays, bioremediation, and treatment of wastewaters as well. Accordingly, enhancing stability and catalytic activity of this protein for biotechnological uses has been one of the important issues in the field of biological investigations in recent years. In this study, pH-induced structural alterations of native (HRP), and modified (MHRP) forms of Horseradish peroxidase have been investigated. Based on the results, dramatic loss of the tertiary structure and also the enzymatic activity for both forms of enzymes recorded at pH values lower than 6 and higher than 8. Ellipticiy measurements, however, indicated very slight variations in the secondary structure for MHRP at pH 5. Spectroscopic analysis also indicated that melting of the tertiary structure of MHRP at pH 5 starts at around 45 °C, which is associated to the pKa of His 42 that has a serious role in keeping of the heme prostethic group in its native position through natural hydrogen bond network in the enzyme structure. According to our data, a molten globule like structure of a chemically modified form of Horseradish peroxidase at pH 5 with initial steps of conformational transition in tertiary structure with almost no changes in the secondary structure has been detected. Despite of some conformational changes in the tertiary structure of MHRP at pH 5, this modified form still keeps its catalytic activity to some extent besides enhanced thermal stability. These findings also indicated that a molten globular state does not necessarily preclude efficient catalytic activity. PMID:26417287

Redox Active Transition Metal ions Make Melanin Susceptible to Chemical Degradation Induced by Organic Peroxide.

PubMed

Zadlo, Andrzej; Pilat, Anna; Sarna, Michal; Pawlak, Anna; Sarna, Tadeusz

2017-12-01

With aging, retinal pigment epithelium melanosomes, by fusion with the age pigment lipofuscin, form complex granules called melanolipofuscin. Lipofuscin granules may contain oxidized proteins and lipid hydroperoxides, which in melanolipofuscin could chemically modify melanin polymer, while transition metal ions present in melanin can accelerate such oxidative modifications. The aim of this research was to examine the effect of selected transition metal ions on melanin susceptibility to chemical modification induced by the water-soluble tert-butyl hydroperoxide used as an oxidizing agent. Synthetic melanin obtained by DOPA autooxidation and melanosomes isolated from bovine retinal pigment epithelium were analyzed. To monitor tert-butyl hydroperoxide-induced oxidative changes of DMa and BMs, electron paramagnetic resonance spectroscopy, UV-vis absorption spectroscopy, dynamic light scattering, atomic force microscopy and electron paramagnetic resonance oximetry were employed. These measurements revealed that both copper and iron ions accelerated chemical degradation induced by tert-butyl hydroperoxide, while zinc ions had no effect. Strong prooxidant action was detected only in the case of melanosomes and melanin degraded in the presence of iron. It can be postulated that similar chemical processes, if they occur in situ in melanolipofuscin granules of the human retinal pigment epithelium, would modify antioxidant properties of melanin and its reactivity.

Modified hydrotalcite-like compounds as active fillers of biodegradable polymers for drug release and food packaging applications.

PubMed

Costantino, Umberto; Nocchetti, Morena; Tammaro, Loredana; Vittoria, Vittoria

2012-11-01

This review treats the recent patents and related literature, mainly from the Authors laboratories, on biomedical and food packaging applications of nano-composites constituted of biodegradable polymers filled with micro or nano crystals of organically modified Layered Double Hydroxides of Hydrotalcite type. After a brief outline of the chemical and structural aspects of Hydrotalcite-like compounds (HTlc) and of their manipulation via intercalation of functional molecular anions to obtain materials for numerous, sometime unexpected applications, the review approaches the theme in three separated parts. Part 1 deals with the synthetic method used to prepare the pristine Mg-Al and Zn-Al HTlc and with the procedures of their functionalization with anti-inflammatory (diclofenac), antibacterial (chloramphenicol hemisuccinate), antifibrinolytic (tranexamic acid) drugs and with benzoates with antimicrobial activity. Procedures used to form (nano) composites of polycaprolactone, used as an example of biodegradable polymer, and functionalized HTlc are also reported. Part 2 discusses a patent and related papers on the preparation and biomedical use of a controlled delivery system of the above mentioned pharmacologically active substances. After an introduction dealing with the recent progress in the field of local drug delivery systems, the chemical and structural aspects of the patented system constituted of a biodegradable polymer and HTlc loaded with the active substances will be presented together with an extensive discussion of the drug release in physiological medium. Part 3 deals with a recent patent and related papers on chemical, structural and release property of antimicrobial species of polymeric films containing antimicrobial loaded HTlc able to act as active packaging for food products prolonging their shelf life.

Trace contaminant control simulation computer program, version 8.1

NASA Technical Reports Server (NTRS)

Perry, J. L.

1994-01-01

The Trace Contaminant Control Simulation computer program is a tool for assessing the performance of various process technologies for removing trace chemical contamination from a spacecraft cabin atmosphere. Included in the simulation are chemical and physical adsorption by activated charcoal, chemical adsorption by lithium hydroxide, absorption by humidity condensate, and low- and high-temperature catalytic oxidation. Means are provided for simulating regenerable as well as nonregenerable systems. The program provides an overall mass balance of chemical contaminants in a spacecraft cabin given specified generation rates. Removal rates are based on device flow rates specified by the user and calculated removal efficiencies based on cabin concentration and removal technology experimental data. Versions 1.0 through 8.0 are documented in NASA TM-108409. TM-108409 also contains a source file listing for version 8.0. Changes to version 8.0 are documented in this technical memorandum and a source file listing for the modified version, version 8.1, is provided. Detailed descriptions for the computer program subprograms are extracted from TM-108409 and modified as necessary to reflect version 8.1. Version 8.1 supersedes version 8.0. Information on a separate user's guide is available from the author.

Fabrication and long-wavelength characterization of neat and chemically modified graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalugin, Nikolai G.

2014-03-31

Graphene, a single- or several layer-thick carbon, attracts significant research activity because of its exceptional material properties. Graphene is a promising material for optoelectronic applications. Neat graphene demonstrates potential as a material for long wavelength photodetectors working at elevated temperatures. Chemical modification of graphene opens up many new applications of this material in electronics, in new composite materials, and in new catalysts for different chemical processes. Chemical vapor deposition-grown large-area graphene can be successfully modified with the creation of benzyne attachments. The investigation of microwave properties is an important part of graphene research. Two variants of near-field long wavelength microscopymore » were found efficient with graphene. Measurements with a probe formed by an electrically open end of a 4 GHz half-lambda parallel-strip transmission line resonator allow the implementation of an electrodynamic model of graphene microwave impedance. The results of near-field scanning superconducting quantum interference device (SQUID) RF microscopy of graphite and graphene at 200 MHz shed light on mechanisms of AC graphene response: screening currents induced in graphene by an external RF magnetic field tend to localize near structural defects.« less

Effect of Immobilized Antithrombin III on the Thromboresistance of Polycarbonate Urethane.

PubMed

Lukas, Karin; Stadtherr, Karin; Gessner, Andre; Wehner, Daniel; Schmid, Thomas; Wendel, Hans Peter; Schmid, Christof; Lehle, Karla

2017-03-24

The surface of foils and vascular grafts made from a thermoplastic polycarbonate urethanes (PCU) (Chronoflex AR) were chemically modified using gas plasma treatment, binding of hydrogels-(1) polyethylene glycol bisdiamine and carboxymethyl dextran (PEG-DEX) and (2) polyethyleneimine (PEI)-and immobilization of human antithrombin III (AT). Their biological impact was tested in vitro under static and dynamic conditions. Static test methods showed a significantly reduced adhesion of endothelial cells, platelets, and bacteria, compared to untreated PCU. Modified PCU grafts were circulated in a Chandler-Loop model for 90 min at 37 °C with human blood. Before and after circulation, parameters of the hemostatic system (coagulation, platelets, complement, and leukocyte activation) were analyzed. PEI-AT significantly inhibited the activation of both coagulation and platelets and prevented the activation of leukocytes and complement. In conclusion, both modifications significantly reduce coagulation activation, but only PEI-AT creates anti-bacterial and anti-thrombogenic functionality.

Modification of enzymes by use of high-pressure homogenization.

PubMed

Dos Santos Aguilar, Jessika Gonçalves; Cristianini, Marcelo; Sato, Helia Harumi

2018-07-01

High-pressure is an emerging and relatively new technology that can modify various molecules. High-pressure homogenization (HPH) has been used in several studies on protein modification, especially in enzymes used or found in food, from animal, plant or microbial resources. According to the literature, the enzymatic activity can be modulated under pressure causing inactivation, stabilization or activation of the enzymes, which, depending on the point of view could be very useful. Homogenization can generate changes in the structure of the enzyme modifying various chemical bonds (mainly weak bonds) causing different denaturation levels and, consequently, affecting the catalytic activity. This review aims to describe the various alterations due to HPH treatment in enzymes, to show the influence of high-pressure on proteins and to report the HPH effects on the enzymatic activity of different enzymes employed in the food industry and research. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of Trichostatin A on drug uptake transporters in primary rat hepatocyte cultures

PubMed Central

Ramboer, Eva; Rogiers, Vera; Vanhaecke, Tamara; Vinken, Mathieu

2015-01-01

The present study was set up to investigate the effects of Trichostatin A (TSA), a prototypical epigenetic modifier, on the expression and activity of hepatic drug uptake transporters in primary cultured rat hepatocytes. To this end, the expression of the sinusoidal transporters sodium-dependent taurocholate cotransporting polypeptide (Ntcp) and organic anion transporting polypeptide 4 (Oatp4) was monitored by real-time quantitative reverse transcriptase polymerase chain reaction analysis and immunoblotting. The activity of the uptake transporters was analyzed using radiolabeled substrates and chemical inhibitors. Downregulation of the expression and activity of Oatp4 and Ntcp was observed as a function of the cultivation time and could not be counteracted by TSA. In conclusion, the epigenetic modifier TSA does not seem to exert a positive effect on the expression and activity of the investigated uptake transporters in primary rat hepatocyte cultures. PMID:26648816

Activation of structural carbon fibres for potential applications in multifunctional structural supercapacitors.

PubMed

Qian, Hui; Diao, Hele; Shirshova, Natasha; Greenhalgh, Emile S; Steinke, Joachim G H; Shaffer, Milo S P; Bismarck, Alexander

2013-04-01

The feasibility of modifying conventional structural carbon fibres via activation has been studied to create fibres, which can be used simultaneously as electrode and reinforcement in structural composite supercapacitors. Both physical and chemical activation, including using steam, carbon dioxide, acid and potassium hydroxide, were conducted and the resulting fibre properties compared. It was proven that the chemical activation using potassium hydroxide is an effective method to prepare activated structural carbon fibres that possess both good electrochemical and mechanical properties. The optimal activation conditions, such as the loading of activating agent and the burn-off of carbon fibres, was identified and delivered a 100-fold increase in specific surface area and 50-fold improvement in specific electrochemical capacitance without any degradation of the fibre mechanical properties. The activation process was successfully scaled-up, showing good uniformity and reproducibility. These activated structural carbon fibres are promising candidates as reinforcement/electrodes for multifunctional structural energy storage devices. Copyright © 2012 Elsevier Inc. All rights reserved.

North Carolina Marine Education Manual, Unit Two: Seawater.

ERIC Educational Resources Information Center

Mauldin, Lundie; Frankenberg, Dirk

Although North Carolina's coastal water is chemically and physically similar to other bodies of sea water, the specific manner in which tides and waves act upon the coastline is unique. Accordingly, the 30 activities presented in this manual are intended to help junior high school students understand how physical forces modify coastal areas. While…

Making the Rate: Enzyme Dynamics

ERIC Educational Resources Information Center

Ragsdale, Frances R.

2004-01-01

An enzyme exercise to address the problem of students inability to visualize chemical reaction at the molecular level is described. This exercise is designed as a dry lab exercise but can be modified into a classroom activity then can be augmented by a wet lab procedure, thereby providing students with a practical exposure to enzyme function.

EFFECTS OF TRENBOLONE ON EXPRESSION OF ESTROGEN-RESPONSIVE PLASMA PROTEINS IN ADULT SHEEPSHEAD MINNOW, (CYPRINODON VARIEGATUS)

EPA Science Inventory

Protein profiling can be used for detection of biomarkers that can be applied diagnostically to screen chemicals for endocrine modifying activity. In previous studies using sheepshead minnows (SHM), mass spectral analysis detected four peptides (2950.5, 2972.5, 3003.4, 3025.5 m/z...

Adsorption of aromatic compounds from the biodegradation of azo dyes on activated carbon

NASA Astrophysics Data System (ADS)

Faria, P. C. C.; Órfão, J. J. M.; Figueiredo, J. L.; Pereira, M. F. R.

2008-03-01

The adsorption of three selected aromatic compounds (aniline, sulfanilic acid and benzenesulfonic acid) on activated carbons with different surface chemical properties was investigated at different solution pH. A fairly basic commercial activated carbon was modified by means of chemical treatment with HNO 3, yielding an acid activated carbon. The textural properties of this sample were not significantly changed after the oxidation treatment. Equilibrium isotherms of the selected compounds on the mentioned samples were obtained and the results were discussed in relation to their surface chemistry. The influence of electrostatic and dispersive interactions involved in the uptake of the compounds studied was evaluated. The Freundlich model was used to fit the experimental data. Higher uptakes are attained when the compounds are present in their molecular form. In general, adsorption was disfavoured by the introduction of oxygen-containing groups on the surface of the activated carbon.

Automated Inference of Chemical Discriminants of Biological Activity.

PubMed

Raschka, Sebastian; Scott, Anne M; Huertas, Mar; Li, Weiming; Kuhn, Leslie A

2018-01-01

Ligand-based virtual screening has become a standard technique for the efficient discovery of bioactive small molecules. Following assays to determine the activity of compounds selected by virtual screening, or other approaches in which dozens to thousands of molecules have been tested, machine learning techniques make it straightforward to discover the patterns of chemical groups that correlate with the desired biological activity. Defining the chemical features that generate activity can be used to guide the selection of molecules for subsequent rounds of screening and assaying, as well as help design new, more active molecules for organic synthesis.The quantitative structure-activity relationship machine learning protocols we describe here, using decision trees, random forests, and sequential feature selection, take as input the chemical structure of a single, known active small molecule (e.g., an inhibitor, agonist, or substrate) for comparison with the structure of each tested molecule. Knowledge of the atomic structure of the protein target and its interactions with the active compound are not required. These protocols can be modified and applied to any data set that consists of a series of measured structural, chemical, or other features for each tested molecule, along with the experimentally measured value of the response variable you would like to predict or optimize for your project, for instance, inhibitory activity in a biological assay or ΔG binding . To illustrate the use of different machine learning algorithms, we step through the analysis of a dataset of inhibitor candidates from virtual screening that were tested recently for their ability to inhibit GPCR-mediated signaling in a vertebrate.

2'-OMe-phosphorodithioate-modified siRNAs show increased loading into the RISC complex and enhanced anti-tumour activity.

PubMed

Wu, Sherry Y; Yang, Xianbin; Gharpure, Kshipra M; Hatakeyama, Hiroto; Egli, Martin; McGuire, Michael H; Nagaraja, Archana S; Miyake, Takahito M; Rupaimoole, Rajesha; Pecot, Chad V; Taylor, Morgan; Pradeep, Sunila; Sierant, Malgorzata; Rodriguez-Aguayo, Cristian; Choi, Hyun J; Previs, Rebecca A; Armaiz-Pena, Guillermo N; Huang, Li; Martinez, Carlos; Hassell, Tom; Ivan, Cristina; Sehgal, Vasudha; Singhania, Richa; Han, Hee-Dong; Su, Chang; Kim, Ji Hoon; Dalton, Heather J; Kovvali, Chandra; Keyomarsi, Khandan; McMillan, Nigel A J; Overwijk, Willem W; Liu, Jinsong; Lee, Ju-Seog; Baggerly, Keith A; Lopez-Berestein, Gabriel; Ram, Prahlad T; Nawrot, Barbara; Sood, Anil K

2014-03-12

Improving small interfering RNA (siRNA) efficacy in target cell populations remains a challenge to its clinical implementation. Here, we report a chemical modification, consisting of phosphorodithioate (PS2) and 2'-O-Methyl (2'-OMe) MePS2 on one nucleotide that significantly enhances potency and resistance to degradation for various siRNAs. We find enhanced potency stems from an unforeseen increase in siRNA loading to the RNA-induced silencing complex, likely due to the unique interaction mediated by 2'-OMe and PS2. We demonstrate the therapeutic utility of MePS2 siRNAs in chemoresistant ovarian cancer mouse models via targeting GRAM domain containing 1B (GRAMD1B), a protein involved in chemoresistance. GRAMD1B silencing is achieved in tumours following MePS2-modified siRNA treatment, leading to a synergistic anti-tumour effect in combination with paclitaxel. Given the previously limited success in enhancing siRNA potency with chemically modified siRNAs, our findings represent an important advance in siRNA design with the potential for application in numerous cancer types.

Base modifications affecting RNA polymerase and reverse transcriptase fidelity.

PubMed

Potapov, Vladimir; Fu, Xiaoqing; Dai, Nan; Corrêa, Ivan R; Tanner, Nathan A; Ong, Jennifer L

2018-06-20

Ribonucleic acid (RNA) is capable of hosting a variety of chemically diverse modifications, in both naturally-occurring post-transcriptional modifications and artificial chemical modifications used to expand the functionality of RNA. However, few studies have addressed how base modifications affect RNA polymerase and reverse transcriptase activity and fidelity. Here, we describe the fidelity of RNA synthesis and reverse transcription of modified ribonucleotides using an assay based on Pacific Biosciences Single Molecule Real-Time sequencing. Several modified bases, including methylated (m6A, m5C and m5U), hydroxymethylated (hm5U) and isomeric bases (pseudouridine), were examined. By comparing each modified base to the equivalent unmodified RNA base, we can determine how the modification affected cumulative RNA polymerase and reverse transcriptase fidelity. 5-hydroxymethyluridine and N6-methyladenosine both increased the combined error rate of T7 RNA polymerase and reverse transcriptases, while pseudouridine specifically increased the error rate of RNA synthesis by T7 RNA polymerase. In addition, we examined the frequency, mutational spectrum and sequence context of reverse transcription errors on DNA templates from an analysis of second strand DNA synthesis.

Immobilization of glucoamylase on ceramic membrane surfaces modified with a new method of treatment utilizing SPCP-CVD.

PubMed

Ida; Matsuyama; Yamamoto

2000-07-01

Glucoamylase, as a model enzyme, was immobilized on a ceramic membrane modified by surface corona discharge induced plasma chemical process-chemical vapor deposition (SPCP-CVD). Characterizations of the immobilized enzyme were then discussed. Three kinds of ceramic membranes with different amounts of amino groups on the surface were prepared utilizing the SPCP-CVD method. Each with 1-time, 3-times and 5-times surface modification treatments and used for supports in glucoamylase immobilization. The amount of immobilized glucoamylase increased with the increase in the number of surface modification treatments and saturated to a certain maximum value estimated by a two-dimensional random packing. The operational stability of the immobilized glucoamylase also increased with the increase in the number of the surface treatment. It was almost the same as the conventional method, while the activity of immobilized enzyme was higher. The results indicated the possibility of designing the performance of the immobilized enzyme by controlling the amount of amino groups. The above results showed that the completely new surface modification method using SPCP was effective in modifying ceramic membranes for enzyme immobilization.

Cell-mediated T lymphocyte responses against syngeneic cells modified with amino-reactive hapten (AED-NH2): H-2Dk serves as an element for cell-mediated lympholysis to amino-reactive hapten (AED-NH2)-modified self.

PubMed

Mizuochi, T; Fujiwara, H; Takai, Y; Hamaoka, T

1985-02-01

Spleen cells from C3H/He mice immunized to the newly synthesized amino-reactive hapten, 5-sulfo-1-naphthoxy acetic acid N-hydroxysuccinimide (AED-NH2), were stimulated in vitro with AED-NH2 modified syngeneic cells. After 5 days of culture, effector cells were assayed for their cytotoxic activity against AED-NH2-modified target blast cells. In contrast to other amino-reactive haptens reported so far, a strong cytotoxic activity against AED-NH2-modified syngeneic cells was found in H-2b mice as well as in H-2k mice. Furthermore, Dk-restricted anti-AED-NH2 CTL recognition was observed in H-2k mice as shown by cold target inhibition. Previous studies have demonstrated the predominant influence of K over D region self determinants, and of the chemical reactivity of the haptenic reagent in Ir gene control of CTL response to hapten-self. The present report illustrates the importance of the hapten itself in genetic regulation of these CTL responses.

Chemistry and biological activity of platinum amidine complexes.

PubMed

Michelin, Rino A; Sgarbossa, Paolo; Sbovata, Silvia Mazzega; Gandin, Valentina; Marzano, Cristina; Bertani, Roberta

2011-07-04

Platinum amidine complexes represent a new class of potential antitumor drugs that contain the imino moiety HN=C(sp(2)) bonded to the platinum center. They can be related to the iminoether derivatives, which were recently shown to be the first Pt(II) compounds with a trans configuration endowed with anticancer activity. The chemical and biological properties of platinum amidine complexes, and more generally of platinum imino derivatives, can be rationally modified through suitable synthetic procedures with the aim of improving their cytotoxicity and antitumor activity. The addition of protic nucleophiles to nitriles coordinated to platinum in various oxidation states can offer a wide variety of complexes with chemical, structural, and physical properties specifically tuned for a more efficacious biological response. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antimicrobial Peptides Produced by Selective Pressure Incorporation of Non-canonical Amino Acids.

PubMed

Nickling, Jessica H; Baumann, Tobias; Schmitt, Franz-Josef; Bartholomae, Maike; Kuipers, Oscar P; Friedrich, Thomas; Budisa, Nediljko

2018-05-04

Nature has a variety of possibilities to create new protein functions by modifying the sequence of the individual amino acid building blocks. However, all variations are based on the 20 canonical amino acids (cAAs). As a way to introduce additional physicochemical properties into polypeptides, the incorporation of non-canonical amino acids (ncAAs) is increasingly used in protein engineering. Due to their relatively short length, the modification of ribosomally synthesized and post-translationally modified peptides by ncAAs is particularly attractive. New functionalities and chemical handles can be generated by specific modifications of individual residues. The selective pressure incorporation (SPI) method utilizes auxotrophic host strains that are deprived of an essential amino acid in chemically defined growth media. Several structurally and chemically similar amino acid analogs can then be activated by the corresponding aminoacyl-tRNA synthetase and provide residue-specific cAA(s) → ncAA(s) substitutions in the target peptide or protein sequence. Although, in the context of the SPI method, ncAAs are also incorporated into the host proteome during the phase of recombinant gene expression, the majority of the cell's resources are assigned to the expression of the target gene. This enables efficient residue-specific incorporation of ncAAs often accompanied with high amounts of modified target. The presented work describes the in vivo incorporation of six proline analogs into the antimicrobial peptide nisin, a lantibiotic naturally produced by Lactococcus lactis. Antimicrobial properties of nisin can be changed and further expanded during its fermentation and expression in auxotrophic Escherichia coli strains in defined growth media. Thereby, the effects of residue-specific replacement of cAAs with ncAAs can deliver changes in antimicrobial activity and specificity. Antimicrobial activity assays and fluorescence microscopy are used to test the new nisin variants for growth inhibition of a Gram-positive Lactococcus lactis indicator strain. Mass spectroscopy is used to confirm ncAA incorporation in bioactive nisin variants.

An efficient visible-light photocatalyst prepared by modifying AgBr particles with a small amount of activated carbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Desong, E-mail: dswang06@126.com; Zhao, Mangmang; Luo, Qingzhi

2016-04-15

Highlights: • An efficient visible-light photocatalyst was prepared by modifying AgBr particles. • A small amount of activated carbon was used to modify AgBr particles. • The modified AgBr exhibited improved visible-light photocatalytic performances. - Abstract: An efficient visible-light photocatalyst was successfully prepared by modifying AgBr particles with a small amount of activated carbon (AC) via a simple chemical precipitation approach. The AC/AgBr composite was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, UV–vis diffuse reflection spectroscopy, photoluminescence spectroscopy, electrochemical impedance spectroscopy. The photocatalytic performances of the AC/AgBr composite were investigated by evaluating photodegradation of methyl orange (MO)more » and phenol under visible light irradiation, and the effects of the AC content in the composite, concentrations of AC/AgBr composite and MO, carrier scavengers on MO photodegradation rate were systematically investigated. The results indicated that the modification of AC can hardly change the crystalline and crystal size of AgBr particles, while significantly improve their specific surface areas, visible-light absorption and separation efficiency of photogenerated electron–hole pairs. Compared with pure AgBr, the AC/AgBr composite exhibited drastically enhanced visible-light photocatalytic activity and stability. The photogenerated electrons and holes, hydroxyl radicals are responsible to the photodegradation of organic pollutants, and the photogenerated holes are the main active species. On the basis of the results and the properties of AC and AgBr, the visible-light photocatalytic mechanism of the AC/AgBr composite was discussed.« less

Phosphate-Modified Nucleotides for Monitoring Enzyme Activity.

PubMed

Ermert, Susanne; Marx, Andreas; Hacker, Stephan M

2017-04-01

Nucleotides modified at the terminal phosphate position have been proven to be interesting entities to study the activity of a variety of different protein classes. In this chapter, we present various types of modifications that were attached as reporter molecules to the phosphate chain of nucleotides and briefly describe the chemical reactions that are frequently used to synthesize them. Furthermore, we discuss a variety of applications of these molecules. Kinase activity, for instance, was studied by transfer of a phosphate modified with a reporter group to the target proteins. This allows not only studying the activity of kinases, but also identifying their target proteins. Moreover, kinases can also be directly labeled with a reporter at a conserved lysine using acyl-phosphate probes. Another important application for phosphate-modified nucleotides is the study of RNA and DNA polymerases. In this context, single-molecule sequencing is made possible using detection in zero-mode waveguides, nanopores or by a Förster resonance energy transfer (FRET)-based mechanism between the polymerase and a fluorophore-labeled nucleotide. Additionally, fluorogenic nucleotides that utilize an intramolecular interaction between a fluorophore and the nucleobase or an intramolecular FRET effect have been successfully developed to study a variety of different enzymes. Finally, also some novel techniques applying electron paramagnetic resonance (EPR)-based detection of nucleotide cleavage or the detection of the cleavage of fluorophosphates are discussed. Taken together, nucleotides modified at the terminal phosphate position have been applied to study the activity of a large diversity of proteins and are valuable tools to enhance the knowledge of biological systems.

Stabilization of electrogenerated copper species on electrodes modified with quantum dots.

PubMed

Martín-Yerga, Daniel; Costa-García, Agustín

2017-02-15

Quantum dots (QDs) have special optical, surface, and electronic properties that make them useful for electrochemical applications. In this work, the electrochemical behavior of copper in ammonia medium is described using bare screen-printed carbon electrodes and the same modified with CdSe/ZnS QDs. At the bare electrodes, the electrogenerated Cu(i) and Cu(0) species are oxidized by dissolved oxygen in a fast coupled chemical reaction, while at the QDs-modified electrode, the re-oxidation of Cu(i) and Cu(0) species can be observed, which indicates that they are stabilized by the nanocrystals present on the electrode surface. A weak adsorption is proposed as the main cause for this stabilization. The electrodeposition on electrodes modified with QDs allows the generation of random nanostructures with copper nanoparticles, avoiding the preferential nucleation onto the most active electrode areas.

Application of N-doped graphene modified carbon ionic liquid electrode for direct electrochemistry of hemoglobin.

PubMed

Sun, Wei; Dong, Lifeng; Deng, Ying; Yu, Jianhua; Wang, Wencheng; Zhu, Qianqian

2014-06-01

Nitrogen-doped graphene (NG) was synthesized and used for the investigation on direct electrochemistry of hemoglobin (Hb) with a carbon ionic liquid electrode as the substrate electrode. Due to specific characteristics of NG such as excellent electrocatalytic property and large surface area, direct electron transfer of Hb was realized with enhanced electrochemical responses appearing. Electrochemical behaviors of Hb on the NG modified electrode were carefully investigated with the electrochemical parameters calculated. The Hb modified electrode exhibited excellent electrocatalytic reduction activity toward different substrates, such as trichloroacetic acid and H2O2, with wider dynamic range and lower detection limit. These findings show that NG can be used for the preparation of chemically modified electrodes with improved performance and has potential applications in electrochemical sensing. Copyright © 2014 Elsevier B.V. All rights reserved.

Improving CRISPR-Cas specificity with chemical modifications in single-guide RNAs.

PubMed

Ryan, Daniel E; Taussig, David; Steinfeld, Israel; Phadnis, Smruti M; Lunstad, Benjamin D; Singh, Madhurima; Vuong, Xuan; Okochi, Kenji D; McCaffrey, Ryan; Olesiak, Magdalena; Roy, Subhadeep; Yung, Chong Wing; Curry, Bo; Sampson, Jeffrey R; Bruhn, Laurakay; Dellinger, Douglas J

2018-01-25

CRISPR systems have emerged as transformative tools for altering genomes in living cells with unprecedented ease, inspiring keen interest in increasing their specificity for perfectly matched targets. We have developed a novel approach for improving specificity by incorporating chemical modifications in guide RNAs (gRNAs) at specific sites in their DNA recognition sequence ('guide sequence') and systematically evaluating their on-target and off-target activities in biochemical DNA cleavage assays and cell-based assays. Our results show that a chemical modification (2'-O-methyl-3'-phosphonoacetate, or 'MP') incorporated at select sites in the ribose-phosphate backbone of gRNAs can dramatically reduce off-target cleavage activities while maintaining high on-target performance, as demonstrated in clinically relevant genes. These findings reveal a unique method for enhancing specificity by chemically modifying the guide sequence in gRNAs. Our approach introduces a versatile tool for augmenting the performance of CRISPR systems for research, industrial and therapeutic applications. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

Improving CRISPR–Cas specificity with chemical modifications in single-guide RNAs

PubMed Central

Ryan, Daniel E; Taussig, David; Steinfeld, Israel; Phadnis, Smruti M; Lunstad, Benjamin D; Singh, Madhurima; Vuong, Xuan; Okochi, Kenji D; McCaffrey, Ryan; Olesiak, Magdalena; Roy, Subhadeep; Yung, Chong Wing; Curry, Bo; Sampson, Jeffrey R; Dellinger, Douglas J

2018-01-01

Abstract CRISPR systems have emerged as transformative tools for altering genomes in living cells with unprecedented ease, inspiring keen interest in increasing their specificity for perfectly matched targets. We have developed a novel approach for improving specificity by incorporating chemical modifications in guide RNAs (gRNAs) at specific sites in their DNA recognition sequence (‘guide sequence’) and systematically evaluating their on-target and off-target activities in biochemical DNA cleavage assays and cell-based assays. Our results show that a chemical modification (2′-O-methyl-3′-phosphonoacetate, or ‘MP’) incorporated at select sites in the ribose-phosphate backbone of gRNAs can dramatically reduce off-target cleavage activities while maintaining high on-target performance, as demonstrated in clinically relevant genes. These findings reveal a unique method for enhancing specificity by chemically modifying the guide sequence in gRNAs. Our approach introduces a versatile tool for augmenting the performance of CRISPR systems for research, industrial and therapeutic applications. PMID:29216382

Predicting skin sensitization potential and inter-laboratory reproducibility of a human Cell Line Activation Test (h-CLAT) in the European Cosmetics Association (COLIPA) ring trials.

PubMed

Sakaguchi, Hitoshi; Ryan, Cindy; Ovigne, Jean-Marc; Schroeder, Klaus R; Ashikaga, Takao

2010-09-01

Regulatory policies in Europe prohibited the testing of cosmetic ingredients in animals for a number of toxicological endpoints. Currently no validated non-animal test methods exist for skin sensitization. Evaluation of changes in cell surface marker expression in dendritic cell (DC)-surrogate cell lines represents one non-animal approach. The human Cell Line Activation Test (h-CLAT) examines the level of CD86 and CD54 expression on the surface of THP-1 cells, a human monocytic leukemia cell line, following 24h of chemical exposure. To examine protocol transferability, between-lab reproducibility, and predictive capacity, the h-CLAT has been evaluated by five independent laboratories in several ring trials (RTs) coordinated by the European Cosmetics Association (COLIPA). The results of the first and second RTs demonstrated that the protocol was transferable and basically had good between-lab reproducibility and predictivity, but there were some false negative data. To improve performance, protocol and prediction model were modified. Using the modified prediction model in the first and second RT, accuracy was improved. However, about 15% of the outcomes were not correctly identified, which exposes some of the limitations of the assay. For the chemicals evaluated, the limitation may due to chemical being a weak allergen or having low solubility (ex. alpha-hexylcinnamaldehyde). The third RT evaluated the modified prediction model and satisfactory results were obtained. From the RT data, the feasibility of utilizing cell lines as surrogate DC in development of in vitro skin sensitization methods shows promise. The data also support initiating formal pre-validation of the h-CLAT in order to fully understand the capabilities and limitations of the assay. Copyright 2010 Elsevier Ltd. All rights reserved.

Chemical and Biological Tools for the Preparation of Modified Histone Proteins

PubMed Central

Howard, Cecil J.; Yu, Ruixuan R.; Gardner, Miranda L.; Shimko, John C.; Ottesen, Jennifer J.

2016-01-01

Eukaryotic chromatin is a complex and dynamic system in which the DNA double helix is organized and protected by interactions with histone proteins. This system is regulated through, a large network of dynamic post-translational modifications (PTMs) exists to ensure proper gene transcription, DNA repair, and other processes involving DNA. Homogenous protein samples with precisely characterized modification sites are necessary to better understand the functions of modified histone proteins. Here, we discuss sets of chemical and biological tools that have been developed for the preparation of modified histones, with a focus on the appropriate choice of tool for a given target. We start with genetic approaches for the creation of modified histones, including the incorporation of genetic mimics of histone modifications, chemical installation of modification analogs, and the use of the expanded genetic code to incorporate modified amino acids. Additionally, we will cover the chemical ligation techniques that have been invaluable in the generation of complex modified histones that are indistinguishable from the natural counterparts. Finally, we will end with a prospectus on future directions of synthetic chromatin in living systems. PMID:25863817

Modified Surface Having Low Adhesion Properties to Mitigate Insect Residue Adhesion

NASA Technical Reports Server (NTRS)

Wohl, Christopher J., Jr. (Inventor); Smith, Joseph G., Jr. (Inventor); Siochi, Emilie J. (Inventor); Penner, Ronald K. (Inventor)

2016-01-01

A process to modify a surface to provide reduced adhesion surface properties to mitigate insect residue adhesion. The surface may include the surface of an article including an aircraft, an automobile, a marine vessel, all-terrain vehicle, wind turbine, helmet, etc. The process includes topographically and chemically modifying the surface by applying a coating comprising a particulate matter, or by applying a coating and also topographically modifying the surface by various methods, including but not limited to, lithographic patterning, laser ablation and chemical etching, physical vapor phase deposition, chemical vapor phase deposition, crystal growth, electrochemical deposition, spin casting, and film casting.

Metal Oxide Nanoparticles: The Importance of Size, Shape, Chemical Composition, and Valence State in Determining Toxicity

NASA Astrophysics Data System (ADS)

Dunnick, Katherine

Nanoparticles, which are defined as a structure with at least one dimension between 1 and 100 nm, have the potential to be used in a variety of consumer products due to their improved functionality compared to similar particles of larger size. Their small size is associated with increased strength, improved catalytic properties, and increased reactivity; however, their size is also associated with increased toxicity in vitro and in vivo. Numerous toxicological studies have been conducted to determine the properties of nanomaterials that increase their toxicity in order to manufacture new nanomaterials with decreased toxicity. Data indicates that size, shape, chemical composition, and valence state of nanomaterials can dramatically alter their toxicity profile. Therefore, the purpose of this dissertation was to determine how altering the shape, size, and chemical composition of various metal oxide nanoparticles would affect their toxicity. Metal oxides are used in variety of consumer products, from spray-sun screens, to food coloring agents; thus, understanding the toxicity of metal oxides and determining which aspects affect their toxicity may provide safe alternatives nanomaterials for continued use in manufacturing. Tungstate nanoparticles toxicity was assessed in an in vitro model using RAW 264.7 cells. The size, shape, and chemical composition of these nanomaterials were altered and the effect on reactive oxygen species and general cytotoxicity was determined using a variety of techniques. Results demonstrate that shape was important in reactive oxygen species production as wires were able to induce significant reactive oxygen species compared to spheres. Shape, size, and chemical composition did not have much effect on the overall toxicity of these nanoparticles in RAW 264.7 cells over a 72 hour time course, implicating that the base material of the nanoparticles was not toxic in these cells. To further assess how chemical composition can affect toxicity, cerium oxide nanoparticles were chemically modified using a process known as doping, to alter their valence state. The size and shape of the cerium oxide nanoparticles remained constant. Overall, results indicated that cerium oxide was not toxic in both RLE-6TN and NR8383 pulmonary rat cells, however, chemically modifying the valence state of the nanomaterial did affect the antioxidant potential. To determine if this trend was measureable in vivo, rats were exposed to various cerium oxide nanoparticles via intratracheal instillation and damage, changes in pulmonary cell differentials, and phagocytic cell activity were assessed. Results implicate that chemically modifying the nanoparticles had an effect on the overall damage induced by the material but did not dramatically affect inflammatory potential or phagocytic cell activity. Overall the data from these studies imply that size, shape, chemical composition, and valence state of nanomaterials can be manipulated to alter their toxicity.

Non-aqueous homogenous biocatalytic conversion of polysaccharides in ionic liquids using chemically modified glucosidase.

PubMed

Brogan, Alex P S; Bui-Le, Liem; Hallett, Jason P

2018-06-25

The increasing requirement to produce platform chemicals and fuels from renewable sources means advances in biocatalysis are rapidly becoming a necessity. Biomass is widely used in nature as a source of energy and as chemical building blocks. However, recalcitrance towards traditional chemical processes and solvents provides a significant barrier to widespread utility. Here, by optimizing enzyme solubility in ionic liquids, we have discovered solvent-induced substrate promiscuity of glucosidase, demonstrating an unprecedented example of homogeneous enzyme bioprocessing of cellulose. Specifically, chemical modification of glucosidase for solubilization in ionic liquids can increase thermal stability to up to 137 °C, allowing for enzymatic activity 30 times greater than is possible in aqueous media. These results establish that through a synergistic combination of chemical biology (enzyme modification) and reaction engineering (solvent choice), the biocatalytic capability of enzymes can be intensified: a key step towards the full-scale deployment of industrial biocatalysis.

Chemical Modification in the Design of Immobilized Enzyme Biocatalysts: Drawbacks and Opportunities.

PubMed

Rueda, Nazzoly; Dos Santos, Jose C S; Ortiz, Claudia; Torres, Rodrigo; Barbosa, Oveimar; Rodrigues, Rafael C; Berenguer-Murcia, Ángel; Fernandez-Lafuente, Roberto

2016-06-01

Chemical modification of enzymes and immobilization used to be considered as separate ways to improve enzyme properties. This review shows how the coupled use of both tools may greatly improve the final biocatalyst performance. Chemical modification of a previously immobilized enzyme is far simpler and easier to control than the modification of the free enzyme. Moreover, if protein modification is performed to improve its immobilization (enriching the enzyme in reactive groups), the final features of the immobilized enzyme may be greatly improved. Chemical modification may be directed to improve enzyme stability, but also to improve selectivity, specificity, activity, and even cell penetrability. Coupling of immobilization and chemical modification with site-directed mutagenesis is a powerful instrument to obtain fully controlled modification. Some new ideas such as photoreceptive enzyme modifiers that change their physical properties under UV exposition are discussed. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemical modification of citrus pectin: Structural, physical and rheologial implications.

PubMed

Fracasso, Aline Francielle; Perussello, Camila Augusto; Carpiné, Danielle; Petkowicz, Carmen Lúcia de Oliveira; Haminiuk, Charles Windson Isidoro

2018-04-01

The present study aimed to investigate the physical, structural and rheological modifications caused by the chemical modification process of citrus pectin. Therefore, three commercial citrus pectins with different degree of esterification were chemically modified by sequential alkali and acidic hydrolytic process to produce modified citrus pectins (MCP) with special properties. The molar mass (M w ), degree of esterification (DE), monosaccharide composition, 13 C NMR spectra, homogeneity, morphology (SEM) and rheological behavior of both native and modified citrus pectins (MCP) were investigated. The chemical modification reduced the acid uronic content (up to 28.3%) and molar mass (up to 29.98%), however, showed little influence on the degree of esterification of native pectins. Modified citrus pectins presented higher amounts of neutral monosaccharides, mainly galactose, arabinose and rhamnose, typical of the Ramnogalacturonana-I (RG-I) region. Rheological tests indicated that the native and modified citrus pectins presented pseudoplastic behavior, however, the MCP samples were less viscous, compared to the native ones. Modified samples presented better dissolution in water and less strong gels, with good stability during oscillatory shearing at 25°C. This study aims to better understand the implications that chemical modifications may impose on the structure of citrus pectins. Copyright © 2017 Elsevier B.V. All rights reserved.

Extending enzyme molecular recognition with an expanded amino acid alphabet

PubMed Central

Windle, Claire L.; Simmons, Katie J.; Ault, James R.; Trinh, Chi H.; Nelson, Adam

2017-01-01

Natural enzymes are constructed from the 20 proteogenic amino acids, which may then require posttranslational modification or the recruitment of coenzymes or metal ions to achieve catalytic function. Here, we demonstrate that expansion of the alphabet of amino acids can also enable the properties of enzymes to be extended. A chemical mutagenesis strategy allowed a wide range of noncanonical amino acids to be systematically incorporated throughout an active site to alter enzymic substrate specificity. Specifically, 13 different noncanonical side chains were incorporated at 12 different positions within the active site of N-acetylneuraminic acid lyase (NAL), and the resulting chemically modified enzymes were screened for activity with a range of aldehyde substrates. A modified enzyme containing a 2,3-dihydroxypropyl cysteine at position 190 was identified that had significantly increased activity for the aldol reaction of erythrose with pyruvate compared with the wild-type enzyme. Kinetic investigation of a saturation library of the canonical amino acids at the same position showed that this increased activity was not achievable with any of the 20 proteogenic amino acids. Structural and modeling studies revealed that the unique shape and functionality of the noncanonical side chain enabled the active site to be remodeled to enable more efficient stabilization of the transition state of the reaction. The ability to exploit an expanded amino acid alphabet can thus heighten the ambitions of protein engineers wishing to develop enzymes with new catalytic properties. PMID:28196894

Influence of Chemical Precleaning on the Plasma Treatment Efficiency of Aluminum by RF Plasma Pencil

NASA Astrophysics Data System (ADS)

Vadym, Prysiazhnyi; Pavel, Slavicek; Eliska, Mikmekova; Milos, Klima

2016-04-01

This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces. The results of our study showed that the state of the topmost surface layer (i.e. the surface morphology and chemical groups) of plasma modified aluminum significantly depends on the chemical precleaning. Commonly used chemicals (isopropanol, trichlorethane, solution of NaOH in deionized water) were used as precleaning agents. The plasma treatments were done using a radio frequency driven atmospheric pressure plasma pencil developed at Masaryk University, which operates in Ar, Ar/O2 gas mixtures. The effectiveness of the plasma treatment was estimated by the wettability measurements, showing high wettability improvement already after 0.3 s treatment. The effects of surface cleaning (hydrocarbon removal), surface oxidation and activation (generation of OH groups) were estimated using infrared spectroscopy. The changes in the surface morphology were measured using scanning electron microscopy. Optical emission spectroscopy measurements in the near-to-surface region with temperature calculations showed that plasma itself depends on the sample precleaning procedure.

Synthesis of inulin derivatives with quaternary phosphonium salts and their antifungal activity.

PubMed

Chen, Yuan; Tan, Wenqiang; Li, Qing; Dong, Fang; Gu, Guodong; Guo, Zhanyong

2018-07-01

Inulin is a kind of renewable and biodegradable carbohydrate with good water solubility and numerous physiological functions. For further utilization of inulin, chemical modification can be applied to improve its bioactivities. In this paper, five novel inulin derivatives were synthesized via chemical modification with quaternary phosphonium salt. Their antifungal activity against three kinds of plant pathogens including Colletotrichum lagenarium, Phomopsis asparagi, and Fusarium oxysporum was assessed with radial growth assay in vitro. Results revealed that all the inulin derivatives exhibited improved antifungal activity compared with inulin. Particularly, inulin modified with triphenylphosphine (TPhPAIL) exhibited the best antifungal activity with inhibitory indices of 80.0%, 78.8%, and 87.4% against Colletotrichum lagenarium, Phomopsis asparagi, and Fusarium oxysporum at 1.0mg/mL respectively. The results clearly showed that chemical modification of inulin with quaternary phosphonium salt could efficiently improve derivatives' antifungal activity. Further analysis of results indicated that the antifungal activity was influenced by alkyl chain length or electron-withdrawing ability of the grafted quaternary phosphonium salts. Longer alkyl chain lengths or the stronger electron-withdrawing groups would lead to enhanced antifungal efficacy. Copyright © 2018 Elsevier B.V. All rights reserved.

Photocatalytic performance of Ag doped SnO2 nanoparticles modified with curcumin

NASA Astrophysics Data System (ADS)

Vignesh, K.; Hariharan, R.; Rajarajan, M.; Suganthi, A.

2013-07-01

Visible light active Ag doped SnO2 nanoparticles modified with curcumin (Cur-Ag-SnO2) have been prepared by a combined precipitation and chemical impregnation route. The optical properties, phase structures and morphologies of the as-prepared nanoparticles were characterized using UV-visible diffuse reflectance spectra (UV-vis-DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The surface area was measured by Brunauer. Emmett. Teller (B.E.T) analysis. Compared to bare SnO2, the surface modified photocatalysts (Ag-SnO2 and Cur-Ag-SnO2) showed a red shift in the visible region. The photocatalytic activity was monitored via the degradation of rose bengal (RB) dye and the results revealed that Cur-Ag-SnO2 shows better photocatalytic activity than that of Ag-SnO2 and SnO2. The superior photocatalytic activity of Cur-Ag-SnO2 could be attributed to the effective electron-hole separation by surface modification. The effect of photocatalyst concentration, initial dye concentration and electron scavenger on the photocatalytic activity was examined in detail. Furthermore, the antifungal activity of the photocatalysts and the reusability of Cur-Ag-SnO2 were tested.

Proteomic analysis of adducted butyrylcholinesterase for biomonitoring organophosphorus exposures

PubMed Central

Marsillach, Judit; Hsieh, Edward J.; Richter, Rebecca J.; MacCoss, Michael J.; Furlong, Clement E.

2014-01-01

Organophosphorus (OP) compounds include a broad group of toxic chemicals such as insecticides, chemical warfare agents and antiwear agents. The liver cytochromes P450 bioactivate many OPs to potent inhibitors of serine hydrolases. Cholinesterases were the first OP targets discovered and are the most studied. They are used to monitor human exposures to OP compounds. However, the assay that is currently used has limitations. The mechanism of action of OP compounds is the inhibition of serine hydrolases by covalently modifying their active-site serine. After structural rearrangement, the complex OP inhibitor-enzyme is irreversible and will remain in circulation until the modified enzyme is degraded. Mass spectrometry is a sensitive technology for analyzing protein modifications, such as OP-adducted enzymes. These analyses also provide some information about the nature of the OP adduct. Our aim is to develop high-throughput protocols for monitoring OP exposures using mass spectrometry. PMID:23123252

Copolyimide Surface Modifying Agents for Particle Adhesion Mitigation

NASA Technical Reports Server (NTRS)

Wohl, Christopher J.; Connell, John W.

2011-01-01

Marine biofouling, insect adhesion on aircraft surfaces, microbial contamination of sterile environments, and particle contamination all present unique challenges for which researchers have adopted an array of mitigation strategies. Particulate contamination is of interest to NASA regarding exploration of the Moon, Mars, asteroids, etc.1 Lunar dust compromised seals, clogged filters, abraded visors and space suit surfaces, and was a significant health concern during the Apollo missions.2 Consequently, NASA has instituted a multi-faceted approach to address dust including use of sacrificial surfaces, active mitigation requiring the use of an external energy source, and passive mitigation utilizing materials with an intrinsic resistance to surface contamination. One passive mitigation strategy is modification of a material s surface energy either chemically or topographically. The focus of this paper is the synthesis and evaluation of novel copolyimide materials with surface modifying agents (SMA, oxetanes) enabling controlled variation of surface chemical composition.

Impact of the interaction with the positive charge in adsorption of benzene and other organic compounds from aqueous solutions on carbons

NASA Astrophysics Data System (ADS)

Terzyk, Artur P.; Ćwiertnia, Magdalena S.; Wiśniewski, Marek; Gauden, Piotr A.; Rychlicki, Gerhard; Szymański, Grzegorz S.

2007-02-01

We present the results of benzene adsorption at the acidic pH level determined on the series of chemically modified activated carbons and at three temperatures. The influence of carbon surface chemical composition on benzene adsorption is discussed. It is shown that the decrease in the pH level from 7 up to 1.5 increases benzene adsorption and the only exception is carbon modified with gaseous ammonia. Basing on the results of current work and those published previously (for phenol, paracetamol, acetanilide and aniline) and using the results of quantum chemistry calculations (DFT, Gaussian 98) we show, that the value of the energy of interaction with unit positive charge is crucial during the analysis of the influence of pH level on adsorption. Obtained results allow to predict the changes in adsorption of aromatics on carbons with the decrease in the pH level.

Photogeneration of singlet oxygen by the phenothiazine derivatives covalently bound to the surface-modified glassy carbon

NASA Astrophysics Data System (ADS)

Blacha-Grzechnik, Agata; Piwowar, Katarzyna; Krukiewicz, Katarzyna; Koscielniak, Piotr; Szuber, Jacek; Zak, Jerzy K.

2016-05-01

The selected group of four amine-derivatives of phenothiazine was covalently grafted to the glassy carbon surface in the four-step procedure consisting of the electrochemical reduction of the diazonium salt followed by the electrochemical and chemical post-modification steps. The proposed strategy involves the bonding of linker molecule to which the photosensitizer is attached. The synthesized organic layers were characterized by means of cyclic voltammetry, XPS and Raman Spectroscopy. It was shown that the phenothiazines immobilized via proposed strategy retain their photochemical properties and are able to generate 1O2 when activated by the laser radiation. The effectiveness of in situ singlet oxygen generation by those new solid photoactive materials was determined by means of UVVis spectroscopy. The reported, covalently modified solid surfaces may find their application as the singlet oxygen photogenerators in the fine chemicals' synthesis or in the wastewater treatment.

Antifungal activity of Ag:hydroxyapatite thin films synthesized by pulsed laser deposition on Ti and Ti modified by TiO2 nanotubes substrates

NASA Astrophysics Data System (ADS)

Eraković, S.; Janković, A.; Ristoscu, C.; Duta, L.; Serban, N.; Visan, A.; Mihailescu, I. N.; Stan, G. E.; Socol, M.; Iordache, O.; Dumitrescu, I.; Luculescu, C. R.; Janaćković, Dj.; Miškovic-Stanković, V.

2014-02-01

Hydroxyapatite (HA) is a widely used biomaterial for implant thin films, largely recognized for its excellent capability to chemically bond to hard tissue inducing the osteogenesis without immune response from human tissues. Nowadays, intense research efforts are focused on development of antimicrobial HA doped thin films. In particular, HA doped with Ag (Ag:HA) is expected to inhibit the attachment of microbes and contamination of metallic implant surface. We herewith report on nano-sized HA and Ag:HA thin films synthesized by pulsed laser deposition on pure Ti and Ti modified with 100 nm diameter TiO2 nanotubes (fabricated by anodization of Ti plates) substrates. The HA-based thin films were characterized by SEM, AFM, EDS, FTIR, and XRD. The cytotoxic activity was tested with HEp2 cells against controls. The antifungal efficiency of the deposited layers was tested against the Candida albicans and Aspergillus niger strains. The Ti substrates modified with TiO2 nanotubes covered with Ag:HA thin films showed the highest antifungal activity.

Studies on chemical modification of cold agglutinin from the snail Achatina fulica.

PubMed Central

Sarkar, M; Mitra, D; Sen, A K

1987-01-01

The cold agglutinin isolated from the albumin gland of the snail Achatina fulica was modified with various chemical reagents in order to detect the amino acids and/or carbohydrate residues present in its carbohydrate-binding sites. Treatment with reagents considered specific for modification of lysine, arginine and tryptophan residues of the cold agglutinin did not affect the carbohydrate-binding activity of the agglutinin. Modification of tyrosine residues showed some change. However, modification with carbodiimide followed by alpha-aminobutyric acid methyl ester causes almost complete loss of its binding activity, indicating the involvement of aspartic acid and glutamic acid in its carbohydrate-binding activity. The carbohydrate residues of the cold agglutinin were removed by beta-elimination reaction, indicating that the sugars are O-glycosidically linked to protein part of the molecule. Removal of galactose residues from the cold agglutinin by the action of beta-galactosidase indicated that the galactose molecules are beta-linked. These carbohydrate-modified glycoproteins showed a marked change in agglutination property, i.e. they agglutinated rabbit erythrocytes at both 10 degrees C and 25 degrees C, indicating that the galactose residues of the glycoprotein play an important role in the cold-agglutination property of the glycoprotein. The c.d. data showed the presence of an almost identical type of random-coil conformation in the native cold agglutinin at 10 degrees C and in the carbohydrate-modified glycoprotein at 10 degrees C and 25 degrees C. This particular random-coil conformation is essential for carbohydrate-binding property of the agglutinin. Images Fig. 1. PMID:3118867

Correction to: Top Down Tandem Mass Spectrometric Analysis of a Chemically Modified Rough-Type Lipopolysaccharide Vaccine Candidate

NASA Astrophysics Data System (ADS)

Oyler, Benjamin L.; Khan, Mohd M.; Smith, Donald F.; Harberts, Erin M.; Kilgour, David P. A.; Ernst, Robert K.; Cross, Alan S.; Goodlett, David R.

2018-04-01

In the preceding article "Top Down Tandem Mass Spectrometric Analysis of a Chemically Modified Rough-Type Lipopolysaccharide Vaccine Candidate" by Oyler et al., an error in the J5 E. coli LPS chemical structure (Figs. 2 and 4) was introduced and propagated into the final revision.

Bio- and chemical syntheses of mangiferin and congeners.

PubMed

Ehianeta, Teddy Stephen; Laval, Stéphane; Yu, Biao

2016-09-10

Mangiferin (2C-β-d-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone) is a xanthone C-glycoside occurring in many plant species. Composed of a glucose unit C1→2 linked to a 1,3,6,7-tetrahydroxyxanthone aglycone, mangiferin exhibits a wide range of biological activities, which recently renewed its interest as a potential pharmacophore. Mangiferin is mainly isolated after extraction procedures from natural sources alongside with its isoforms isomangiferin, homomangiferin, and neomangiferin. However, enzymatic and chemical approaches have been developed to access these phytochemicals, which address the challenging construction of the C-glycosidic linkage. In addition, both approaches have been exploited to modify the aglycone and the sugar moiety in order to afford analogues with specific and improved pharmacological activities. Herein, we provide a comprehensive review on the biosynthesis and chemical synthesis of mangiferin and its congeners. © 2016 BioFactors, 42(5):445-458, 2016. © 2016 International Union of Biochemistry and Molecular Biology.

The effect of surface charge on the thermal stability and ice recrystallization inhibition activity of antifreeze protein III (AFP III).

PubMed

Deller, R C; Carter, B M; Zampetakis, I; Scarpa, F; Perriman, A W

2018-01-01

The aim of this study was to examine the effect of chemical cationization on the structure and function of antifreeze protein III (AFP III) over an extreme temperature range (-40°C to +90°C) using far-UV synchrotron radiation circular dichroism (SRCD) and ice recrystallization inhibition (IRI) assays. Chemical cationization was able to produce a modified AFP III with a net cationic charge at physiological pH that had enhanced resistance to denaturation at elevated temperatures, with no immediate negative impact on protein structure at subzero temperatures. Furthermore, cationized AFP III retained an IRI activity similar to that of native AFP III. Consequently, chemical cationization may provide a pathway to the development of more robust antifreeze proteins as supplementary cryoprotectants in the cryopreservation of clinically relevant cells. Copyright © 2017. Published by Elsevier Inc.

Targeting physiological activities to modify the ecology and functionality of rumen and gastrointestinal ecosystems, prototypical anaerobic digester

USDA-ARS?s Scientific Manuscript database

The rumen microbial ecosystem is highly regarded for its ability to digest and transform low quality plant material into chemical forms of use by the host. However, less than 35% of the dietary energy consumed by the ruminant is conserved by the host. Methane production within the rumen contribute...

Comparison of Estrogen-Responsive Plasma Protein Biomarkers and Reproductive Endpoints in Sheepshead Minnows Exposed to 17B-Trenbolone

EPA Science Inventory

Protein profiling can be used for detection of biomarkers that can be applied diagnostically to screen chemicals for endocrine modifying activity. In previous studies, mass spectral analysis revealed four peptides (2950.5, 2972.5, 3003.4, 3025.5 m/z) in the plasma of estrogen ag...

Zeppelin NT - Measurement Platform for the Exploration of Atmospheric Chemistry and Dynamics in the Planetary Boundary Layer

NASA Astrophysics Data System (ADS)

Hofzumahaus, Andreas; Holland, Frank; Oebel, Andreas; Rohrer, Franz; Mentel, Thomas; Kiendler-Scharr, Astrid; Wahner, Andreas; Brauchle, Artur; Steinlein, Klaus; Gritzbach, Robert

2014-05-01

The planetary boundary layer (PBL) is the chemically most active and complex part of the atmosphere where freshly emitted reactive trace gases, tropospheric radicals, atmospheric oxidation products and aerosols exhibit a large variability and spatial gradients. In order to investigate the chemical degradation of trace gases and the formation of secondary pollutants in the PBL, a commercial Zeppelin NT was modified to be used as an airborne measurement platform for chemical and physical observations with high spatial resolution. The Zeppelin NT was developed by Zeppelin Luftschifftechnik (ZLT) and is operated by Deutsche Zeppelin Reederei (DZR) in Friedrichshafen, Germany. The modification was performed in cooperation between Forschungszentrum Jülich and ZLT. The airship has a length of 75 m, can lift about 1 ton of scientific payload and can be manoeuvered with high precision by propeller engines. The modified Zeppelin can carry measurement instruments mounted on a platform on top of the Zeppelin, or inside the gondola beneath the airship. Three different instrument packages were developed to investigate a. gas-phase oxidation processes involving free radicals (OH, HO2) b. formation of secondary organic aerosols (SOA) c. new particle formation (nucleation) The presentation will describe the modified airship and provide an overview of its technical performance. Examples of its application during the recent PEGASOS flight campaigns in Europe will be given.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Hao; Yang, Fan; Pan, Ding

Mechanical stimuli can modify the energy landscape of chemical reactions and enable reaction pathways, offering a synthetic strategy that complements conventional chemistry. These mechanochemical mechanisms have been studied extensively in one-dimensional polymers under tensile stress using ring-opening and reorganization, polymer unzipping and disulfide reduction as model reactions. In these systems, the pulling force stretches chemical bonds, initiating the reaction. Additionally, it has been shown that forces orthogonal to the chemical bonds can alter the rate of bond dissociation. Furthermore, these bond activation mechanisms have not been possible under isotropic, compressive stress (that is, hydrostatic pressure). Here we show that mechanochemistrymore » through isotropic compression is possible by molecularly engineering structures that can translate macroscopic isotropic stress into molecular-level anisotropic strain.« less

Application of combinatorial biocatalysis for a unique ring expansion of dihydroxymethylzearalenone.

PubMed

Rich, Joseph O; Budde, Cheryl L; McConeghey, Luke D; Cotterill, Ian C; Mozhaev, Vadim V; Singh, Sheo B; Goetz, Michael A; Zhao, Annie; Michels, Peter C; Khmelnitsky, Yuri L

2009-06-01

Combinatorial biocatalysis was applied to generate a diverse set of dihydroxymethylzearalenone analogs with modified ring structure. In one representative chemoenzymatic reaction sequence, dihydroxymethylzearalenone was first subjected to a unique enzyme-catalyzed oxidative ring opening reaction that creates two new carboxylic groups on the molecule. These groups served as reaction sites for further derivatization involving biocatalytic ring closure reactions with structurally diverse bifunctional reagents, including different diols and diamines. As a result, a library of cyclic bislactones and bislactams was created, with modified ring structures covering chemical space and structure activity relationships unattainable by conventional synthetic means.

N-Chloramide Modified Nomex(Registered) as a Regenerable Self-Decontaminating Material for Protection Against Chemical Warfare Agents (Postprint)

DTIC Science & Technology

2009-02-26

weaponizable bacteria, mustard, and VX, as well as possessing antimicrobial properties against nuisance organisms that cause conditions such as athlete’s foot...were assayed for content of active oxidizing agent, and tested for efficacy against 2-chloroethyl ethyl sulfide and Demeton-S, simulants for mustard and...attached to Nomex intended for use as self-decontaminating regenerable military textiles. The materials were assayed for content of active oxidizing

Cys-X scanning for expansion of active-site residues and modulation of catalytic functions in a glutathione transferase.

PubMed

Norrgård, Malena A; Hellman, Ulf; Mannervik, Bengt

2011-05-13

We propose Cys-X scanning as a semisynthetic approach to engineer the functional properties of recombinant proteins. As in the case of Ala scanning, key residues in the primary structure are identified, and one of them is replaced by Cys via site-directed mutagenesis. The thiol of the residue introduced is subsequently modified by alternative chemical reagents to yield diverse Cys-X mutants of the protein. This chemical approach is orthogonal to Ala or Cys scanning and allows the expansion of the repertoire of amino acid side chains far beyond those present in natural proteins. In its present application, we have introduced Cys-X residues in human glutathione transferase (GST) M2-2, replacing Met-212 in the substrate-binding site. To achieve selectivity of the modifications, the Cys residues in the wild-type enzyme were replaced by Ala. A suite of simple substitutions resulted in a set of homologous Met derivatives ranging from normethionine to S-heptyl-cysteine. The chemical modifications were validated by HPLC and mass spectrometry. The derivatized mutant enzymes were assayed with alternative GST substrates representing diverse chemical reactions: aromatic substitution, epoxide opening, transnitrosylation, and addition to an ortho-quinone. The Cys substitutions had different effects on the alternative substrates and differentially enhanced or suppressed catalytic activities depending on both the Cys-X substitution and the substrate assayed. As a consequence, the enzyme specificity profile could be changed among the alternative substrates. The procedure lends itself to large-scale production of Cys-X modified protein variants.

Date palm pollen allergoid: characterization of its chemical-physical and immunological properties.

PubMed

Mistrello, G; Harfi, H; Roncarolo, D; Kwaasi, A; Zanoni, D; Falagiani, P; Panzani, R

2008-01-01

Date palm (DP) pollen can cause allergic symptoms in people living in different countries. Specific immunotherapy with allergenic extracts by subcutaneous route is effective to cure allergic people. However, the risk of side effects has led to explore safer therapeutic modalities. The aim of our work was to evaluate IgE cross-reactivity between DP and autochthonous palm (European fan palm, EFP) pollen extracts, to chemically modify DP extract with potassium cyanate in order to obtain an allergoid, and to characterize it. By radioallergosorbent test inhibition, immunoblotting (IB) and skin prick test, in vitro and in vivo allergenic activities of native and modified DP extracts were compared. By SDS-PAGE and IB, we compared the protein profile and IgE-binding capacity of both native and modified DP, as well as of EFP extracts. By IB inhibition, IgE cross-reactivity of native DP and EFP extracts was evaluated. By ELISA, the capacity of modified DP-induced IgG to react with native DP extract was determined. Radioallergosorbent test inhibition, IB and skin prick test results demonstrated that modified DP was significantly less allergenic than native DP extract. The SDS-PAGE profile showed that potassium cyanate treatment of DP extract did not alter the molecular weight of its components. In addition, no difference was observed between native DP and EFP extracts. Subsequent IB inhibition data evidenced the existence of a strong IgE cross-reactivity between native DP and EFP extracts. ELISA results indicated that the administration of modified DP in mice was able to induce specific IgG also recognizing native DP extract. Modified DP extract (allergoid) seems to be a good candidate for immunotherapy of patients affected by specific allergy. 2007 S. Karger AG, Basel

Conjugated-polyelectrolyte-grafted cotton fibers act as "micro flypaper" for the removal and destruction of bacteria.

PubMed

Ista, Linnea K; Dascier, Dimitri; Ji, Eunkyung; Parthasarathy, Anand; Corbitt, Thomas S; Schanze, Kirk S; Whitten, David G

2011-08-01

We demonstrate herein a method for chemically modifying cotton fibers and cotton-containing fabric with a light-activated, cationic phenylene-ethynylene (PPE-DABCO) conjugated polyelectrolyte biocide. When challenged with Pseudomonas aeruginosa and Bacillus atropheaus vegetative cells from liquid suspension, light-activated PPE-DABCO effects 1.2 and 8 log, respectively, losses in viability of the exposed bacteria. These results suggest that conjugated polyelectrolytes retain their activity when grafted to fabrics, showing promise for use in settings where antimicrobial textiles are needed.

Improved anti-inflammatory activity of three new terpenoids derived, by systematic chemical modifications, from the abundant triterpenes of the flowery plant Calendula officinalis.

PubMed

Neukirch, Hannes; D'Ambrosio, Michele; Sosa, Silvio; Altinier, Gianmario; Della Loggia, Roberto; Guerriero, Antonio

2005-05-01

Rings A, D and E of faradiol (1), and ring E of both arnidiol (10) and calenduladiol (4) have been subjected to various selective chemical manipulations to modify polarity, water affinity, H-bonding, sterics, and number of aromatic groups of these anti-inflammatory natural compounds. A total of 15 new and four known pentacyclic triterpenoids have been obtained in this way. Some 13 terpenoids were evaluated for their topical anti-inflammatory activities with respect to inhibition of croton oil induced ear oedema in mouse. Three derivatives of 1, the C(16) benzyl ether 15, the C(30) aldehyde 24, and the C(30) primary alcohol 25 showed significantly improved anti-inflammatory potencies, which is relevant for (future) structure-activity-relationship (SAR) studies.

A modified oxic-settling-anaerobic activated sludge process using gravity thickening for excess sludge reduction

NASA Astrophysics Data System (ADS)

Wang, Jun; Li, Shi-Yu; Jiang, Feng; Wu, Ke; Liu, Guang-Li; Lu, Hui; Chen, Guang-Hao

2015-09-01

Oxic-settling-anaerobic process (OSA) was known as a cost-effective way to reduce the excess sludge production with simple upgrade of conventional activated sludge process (CAS). A low oxidation-reduction potential (ORP) level was the key factor to sludge decay and lysis in the sludge holding tank of the OSA process. However, the ORP control with nitrogen purge or chemical dosing in the OSA process would induce extra expense and complicate the operation. Hence, in this study, a sludge holding tank using gravity thickening was applied to OSA process to reduce the excess sludge production without any ORP control. Results showed that the modified OSA process not only reduced the excess sludge production effectively but also improved the sludge settleability without affected the treatment capacity. The reduction of the excess sludge production in the modified OSA process resulted from interactions among lots of factors. The key element of the process was the gravity thickening sludge holding tank.

Process for derivatizing carbon nanotubes with diazonium species and compositions thereof

NASA Technical Reports Server (NTRS)

Bahr, Jeffrey L. (Inventor); Tour, James M. (Inventor); Yang, Jiping (Inventor)

2011-01-01

Methods for the chemical modification of carbon nanotubes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications, and sensor devices. The methods of derivatization include electrochemical induced reactions, thermally induced reactions, and photochemically induced reactions. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes.

Abundance of Cysteine Endopeptidase Dionain in Digestive Fluid of Venus Flytrap (Dionaea muscipula Ellis) Is Regulated by Different Stimuli from Prey through Jasmonates

PubMed Central

Libiaková, Michaela; Floková, Kristýna; Novák, Ondřej; Slováková, L'udmila; Pavlovič, Andrej

2014-01-01

The trap of the carnivorous plant Venus flytrap (Dionaea muscipula) catches prey by very rapid closure of its modified leaves. After the rapid closure secures the prey, repeated mechanical stimulation of trigger hairs by struggling prey and the generation of action potentials (APs) result in secretion of digestive fluid. Once the prey's movement stops, the secretion is maintained by chemical stimuli released from digested prey. We investigated the effect of mechanical and chemical stimulation (NH4Cl, KH2PO4, further N(Cl) and P(K) stimulation) on enzyme activities in digestive fluid. Activities of β-D-glucosidases and N-acetyl-β-D-glucosaminidases were not detected. Acid phosphatase activity was higher in N(Cl) stimulated traps while proteolytic activity was higher in both chemically induced traps in comparison to mechanical stimulation. This is in accordance with higher abundance of recently described enzyme cysteine endopeptidase dionain in digestive fluid of chemically induced traps. Mechanical stimulation induced high levels of cis-12-oxophytodienoic acid (cis-OPDA) but jasmonic acid (JA) and its isoleucine conjugate (JA-Ile) accumulated to higher level after chemical stimulation. The concentration of indole-3-acetic acid (IAA), salicylic acid (SA) and abscisic acid (ABA) did not change significantly. The external application of JA bypassed the mechanical and chemical stimulation and induced a high abundance of dionain and proteolytic activity in digestive fluid. These results document the role of jasmonates in regulation of proteolytic activity in response to different stimuli from captured prey. The double trigger mechanism in protein digestion is proposed. PMID:25153528

Identification of cancer chemopreventive isothiocyanates as direct inhibitors of the arylamine N-acetyltransferase-dependent acetylation and bioactivation of aromatic amine carcinogens.

PubMed

Duval, Romain; Xu, Ximing; Bui, Linh-Chi; Mathieu, Cécile; Petit, Emile; Cariou, Kevin; Dodd, Robert H; Dupret, Jean-Marie; Rodrigues-Lima, Fernando

2016-02-23

Aromatic amines (AAs) are chemicals of industrial, pharmacological and environmental relevance. Certain AAs, such as 4-aminobiphenyl (4-ABP), are human carcinogens that require enzymatic metabolic activation to reactive chemicals to form genotoxic DNA adducts. Arylamine N-acetyltransferases (NAT) are xenobiotic metabolizing enzymes (XME) that play a major role in this carcinogenic bioactivation process. Isothiocyanates (ITCs), including benzyl-ITC (BITC) and phenethyl-ITC (PEITC), are phytochemicals known to have chemopreventive activity against several aromatic carcinogens. In particular, ITCs have been shown to modify the bioactivation and subsequent mutagenicity of carcinogenic AA chemicals such as 4-ABP. However, the molecular and biochemical mechanisms by which these phytochemicals may modulate AA carcinogens bioactivation and AA-DNA damage remains poorly understood. This manuscript provides evidence indicating that ITCs can decrease the metabolic activation of carcinogenic AAs via the irreversible inhibition of NAT enzymes and subsequent alteration of the acetylation of AAs. We demonstrate that BITC and PEITC react with NAT1 and inhibit readily its acetyltransferase activity (k(i) = 200 M(-1).s(-1) and 66 M(-1).s(-1) for BITC and PEITC, respectively). Chemical labeling, docking approaches and substrate protection assays indicated that inhibition of the acetylation of AAs by NAT1 was due to the chemical modification of the enzyme active site cysteine. Moreover, analyses of AAs acetylation and DNA adducts in cells showed that BITC was able to modulate the endogenous acetylation and bioactivation of 4-ABP. In conclusion, we show that direct inhibition of NAT enzymes may be an important mechanism by which ITCs exert their chemopreventive activity towards AA chemicals.

Surface modification of calcium sulfate whisker prepared from flue gas desulfurization gypsum

NASA Astrophysics Data System (ADS)

Liu, Chengjun; Zhao, Qing; Wang, Yeguang; Shi, Peiyang; Jiang, Maofa

2016-01-01

In order to obtain hydrophobic whisker for preparing polymeric composite product, the calcium sulfate whisker (CSW) prepared from flue gas desulfurization (FGD) gypsum by hydrothermal synthesis was modified by various surfactants, and the effects of some modification conditions on the hydrophobic property of CSW were investigated in this study. Sodium stearate was considered to be a suitable surfactant and its reasonable dosage was 2% of ethanol solvent. Both physical and chemical absorptions were found in the surface modification process, and the later one was suggested to preferentially occur on the CSW surface. Moreover, modifying temperature, modifying duration, and agitation speed were experimentally found to have a remarkable influence on the modification behavior. Active ratio reached 0.845 when the modification process was conducted under reasonable conditions obtained in the current work. Finally, polypropylene sheet products were prepared from modified CSW showing an excellence mechanical property.

A noninterventional study documenting use and success of implants with a new chemically modified titanium surface in daily dental practice.

PubMed

Luongo, Giuseppe; Oteri, Giacomo

2010-01-01

A new chemically modified titanium surface, SLActive, has recently been developed. The results obtained in controlled clinical trials indicate that this implant can be safely used and that it offers predictable results. The goal of this noninterventional study was to verify that the success rates of implants used in daily dental practice are comparable to those reported in controlled clinical trials. This study was a prospective, noninterventional study using implants with a chemically modified surface according to the daily dental practice procedures applied by private practitioners. The choice of the implantation procedure and the loading protocol were the responsibility of the investigator and were chosen according to the patient's needs. Thirty clinical centers actively participated in this study, and 226 patients were treated, of which, 8 patients were lost to follow-up. Because of the noninterventional design of the study, the patients were not selected according to strictly defined inclusion/exclusion criteria. Thus, the study included individuals with risk factors such as smoking (24%), untreated gingivitis or periodontitis (9%), and bruxism (6%). The implants were equally distributed between mandible (46%) and maxilla (54%). A bone augmentation procedure was done in 31% of the cases. Early loading (functional loading between 48 hours and 3 months after implant insertion) was applied most frequently (48%), followed by the conventional loading protocol (3 to 6 months after implant placement, 34%). Immediate restoration and immediate loading were rare (7% and 2%, respectively). Of 276 implants inserted and documented, 5 implants failures were reported, all of which were associated with a sinus floor augmentation procedure. The survival rate was 98.2% at the 1-year follow-up visit. The results showed that implants with a chemically modified surface can be successfully restored with success rates similar to those reported in formal clinical trials under more controlled conditions.

Semi-synthesis of murine prion protein by native chemical ligation and chemical activation for preparation of polypeptide-α-thioester.

PubMed

Shi, Lei; Chen, Huai; Zhang, Si-Yu; Chu, Ting-Ting; Zhao, Yu-Fen; Chen, Yong-Xiang; Li, Yan-Mei

2017-06-01

Prions are suspected as pathogen of the fatal transmissible spongiform encephalopathies. Strategies to access homogenous prion protein (PrP) are required to fully comprehend the molecular mechanism of prion diseases. However, the polypeptide fragments from PrP show a high tendency to form aggregates, which is a gigantic obstacle of protein synthesis and purification. In this study, murine prion sequence 90 to 230 that is the core three-dimensional structure domain was constructed from three segments murine PrP (mPrP)(90-177), mPrP(178-212), and mPrP(213-230) by combining protein expression, chemical synthesis and chemical ligation. The protein sequence 90 to 177 was obtained from expression and finally converted into the polypeptide hydrazide by chemical activation of a cysteine in the tail. The other two polypeptide fragments of the C-terminal were obtained by chemical synthesis, which utilized the strategies of isopeptide and pseudoproline building blocks to complete the synthesis of such difficult sequences. The three segments were finally assembled by sequentially using native chemical ligation. This strategy will allow more straightforward access to homogeneously modified PrP variants. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Reduced in vitro T-cell responses induced by glutaraldehyde-modified allergen extracts are caused mainly by retarded internalization of dendritic cells

PubMed Central

Heydenreich, Bärbel; Bellinghausen, Iris; Lorenz, Steffen; Henmar, Helene; Strand, Dennis; Würtzen, Peter A; Saloga, Joachim

2012-01-01

Although allergen-specific immunotherapy is a clinically effective therapy for IgE-mediated allergic diseases, the risk of IgE-mediated adverse effects still exists. For this reason, chemically modified allergoids have been introduced, which may destroy IgE-binding sites while T-cell activation should be retained. The aim of the study was to analyse the differences between intact allergens and differently modified/aggregated allergoids concerning their internalization as well as T-cell and basophil activation. For this purpose human monocyte-derived immature dendritic cells (DC) were incubated with Phleum pratense or Betula verrucosa pollen extract or with the corresponding allergoids, modified with formaldehyde or glutaraldehyde. After an additional maturation process, the antigen-loaded mature DC were co-cultured with autologous CD4+ T cells. Allergenicity was tested by leukotriene release from basophils. In addition, the uptake of intact allergens and allergoids by immature DC was analysed. The proliferation of, as well as the interleukin-4 (IL-4), IL-10, IL-13 and interferon-γ production by, CD4+ T cells which had been stimulated with glutaraldehyde allergoid-treated DC was reduced compared with CD4+ T cells stimulated with intact allergen-treated or formaldehyde allergoid-treated DC. In line with this, glutaraldehyde-modified allergoids were more aggregated and were internalized more slowly. Furthermore, only the allergoids modified with glutaraldehyde induced a decreased leukotriene release by activated basophils. These findings suggest that IgE-reactive epitopes were destroyed more efficiently by modification with glutaraldehyde than with formaldehyde under the conditions chosen for these investigations. Glutaraldehyde-modified allergoids also displayed lower T-cell stimulatory capacity, which is mainly the result of greater modification/aggregation and diminished uptake by DC. PMID:22348538

Reduced in vitro T-cell responses induced by glutaraldehyde-modified allergen extracts are caused mainly by retarded internalization of dendritic cells.

PubMed

Heydenreich, Bärbel; Bellinghausen, Iris; Lorenz, Steffen; Henmar, Helene; Strand, Dennis; Würtzen, Peter A; Saloga, Joachim

2012-06-01

Although allergen-specific immunotherapy is a clinically effective therapy for IgE-mediated allergic diseases, the risk of IgE-mediated adverse effects still exists. For this reason, chemically modified allergoids have been introduced, which may destroy IgE-binding sites while T-cell activation should be retained. The aim of the study was to analyse the differences between intact allergens and differently modified/aggregated allergoids concerning their internalization as well as T-cell and basophil activation. For this purpose human monocyte-derived immature dendritic cells (DC) were incubated with Phleum pratense or Betula verrucosa pollen extract or with the corresponding allergoids, modified with formaldehyde or glutaraldehyde. After an additional maturation process, the antigen-loaded mature DC were co-cultured with autologous CD4(+) T cells. Allergenicity was tested by leukotriene release from basophils. In addition, the uptake of intact allergens and allergoids by immature DC was analysed. The proliferation of, as well as the interleukin-4 (IL-4), IL-10, IL-13 and interferon-γ production by, CD4(+) T cells which had been stimulated with glutaraldehyde allergoid-treated DC was reduced compared with CD4(+) T cells stimulated with intact allergen-treated or formaldehyde allergoid-treated DC. In line with this, glutaraldehyde-modified allergoids were more aggregated and were internalized more slowly. Furthermore, only the allergoids modified with glutaraldehyde induced a decreased leukotriene release by activated basophils. These findings suggest that IgE-reactive epitopes were destroyed more efficiently by modification with glutaraldehyde than with formaldehyde under the conditions chosen for these investigations. Glutaraldehyde-modified allergoids also displayed lower T-cell stimulatory capacity, which is mainly the result of greater modification/aggregation and diminished uptake by DC. © 2012 The Authors. Immunology © 2012 Blackwell Publishing Ltd.

Creatine kinase: Essential arginine residues at the nucleotide binding site identified by chemical modification and high-resolution tandem mass spectrometry

PubMed Central

Wood, Troy D.; Guan, Ziqiang; Borders, Charles L.; Chen, Lorenzo H.; Kenyon, George L.; McLafferty, Fred W.

1998-01-01

Phenylglyoxal is an arginine-specific reagent that inactivates creatine kinase (CK). Previous results suggest that modification of the dimeric enzyme at a single arginine residue per subunit causes complete inactivation accompanied by the loss of nucleotide binding; the actual site of modification was not identified. Here, high-resolution tandem mass spectrometry (MS/MS) was used to identify three phenylglyoxal-modified Arg residues in monomeric rabbit muscle CK. Electrospray ionizaton Fourier-transform MS of the phenylglyoxal-modified CK that had lost ≈80% activity identified three species: unmodified, once-modified (+116 Da), and twice-modified (+232 Da) enzyme in a ratio of approximately 1:4:1. MS/MS restricts the derivatized sites to P122-P212 and P283-V332, whereas MS of Lys-C digestions revealed two modified peptides, A266-K297 and G116-K137. The only Arg in A266-K297 is Arg-291 (invariant), whereas MS/MS of modified G116-K137 shows that two of the three sites Arg-129, Arg-131, or Arg-134 (all invariant) can contain the modification. The recently reported x-ray crystal structure for the octameric chicken mitochondrial CK indicates that its nucleotide triphosphate-binding site indeed contains the equivalent of R291, R129, and R131 reported here to be at the active site of rabbit muscle CK. PMID:9520370

Interlaboratory validation of the modified murine local lymph node assay based on adenosine triphosphate measurement.

PubMed

Omori, Takashi; Idehara, Kenji; Kojima, Hajime; Sozu, Takashi; Arima, Kazunori; Goto, Hirohiko; Hanada, Tomohiko; Ikarashi, Yoshiaki; Inoda, Taketo; Kanazawa, Yukiko; Kosaka, Tadashi; Maki, Eiji; Morimoto, Takashi; Shinoda, Shinsuke; Shinoda, Naoki; Takeyoshi, Masahiro; Tanaka, Masashi; Uratani, Mamoru; Usami, Masahito; Yamanaka, Atsushi; Yoneda, Tomofumi; Yoshimura, Isao; Yuasa, Atsuko

2008-01-01

The murine local lymph node assay (LLNA) is a well-established alternative to the guinea pig maximization test (GPMT) or Buehler test (BT) for the assessment of the skin sensitizing ability of drugs and chemicals. Daicel Chemical Industries Ltd. has developed a modified LLNA based on the adenosine triphosphate (ATP) content (LLNA-DA). We conducted 2 interlaboratory validation studies to evaluate the reliability and relevance of LLNA-DA. The experiment involved 17 laboratories, wherein 14 chemicals were examined under blinded conditions. In the first study, 3 chemicals were examined in 10 laboratories and the remaining 9 were examined in 3 laboratories. In the second study, 1 chemical was examined in 7 laboratories and the remaining 4 chemicals were examined in 4 laboratories. The data were expressed as the ATP content for each chemical-treated group, and the stimulation index (SI) for each chemical-treated group was determined as the increase in the ATP content relative to the concurrent vehicle control group. An SI of 3 was set as the cut-off value for exhibiting skin sensitization activity. The results of the first study obtained in the experiments conducted for the 3 chemicals that were examined in all the 10 laboratories and for 5 of the remaining 9 chemicals were sufficiently consistent with small variations in their SI values. The sensitivity, specificity, and accuracy of LLNA-DA against those of GPMT/BT were 7/8 (87.5%), 3/3 (100%), and 10/11 (90.9%), respectively. In the second study, all the 5 chemicals studied demonstrated acceptably small interlaboratory variations. In the first study, a large variation was observed for 2 chemicals; in the second study, this variation was small. It was attributed to the application of dimethylsulfoxide as the solvent for the metallic salts. In conclusion, these 2 studies provide good evidence for the reliability of the LLNA-DA.

Chemical modification of semiconductor surfaces

NASA Technical Reports Server (NTRS)

Finklea, H. O.

1981-01-01

Results of research on the chemical modification of TiO2 powders in the gas phase and the examination of the modified powders by infrared absorption spectroscopy are comprehensively summarized. The range of information obtainable by IR spectroscopy of chemically modified semiconductors, and a definition of the optimum reaction conditions for synthesizing a monolayer of methylsilanes using vapor phase reaction conditions were considered.

Modified Aequorin Shows Increased Bioluminescence Activity

DTIC Science & Technology

1993-08-18

Prendergast, and William W. Ward. Chemical Structure of the Hexapeptide Chromophore of the Aequorea Green - Fluorescent Protein . Biochemistry 32: 1 212...C. Prasher, Virginia K Eckenrode, William W. Ward, Frank G. Prendergast, and Milton J. Cormier. Primary structure of the Aequorea victoria green ...LW. Schultz, J.R. Deschamps, and KB. Ward. Preparation and Initial Characterization of Crystals of the Photoprotein Aequorin from Aequorea victoria

'Pro et contra' ionic liquid drugs - Challenges and opportunities for pharmaceutical translation.

PubMed

Balk, Anja; Holzgrabe, Ulrike; Meinel, Lorenz

2015-08-01

Ionic liquids (ILs) are organic salts with a melting point below 100°C. Active pharmaceutical ingredients (APIs) are transformed into ILs by combining them with typically large yet charged counterions. ILs hold promise to build a large design space for relevant pharmaceutical parameters, particularly for poorly water soluble drugs. It is for this wide design space that ILs may be the entry into the fascinating vision of modifying physico-chemical properties without the need to structurally modify the active pharmaceutical ingredient itself. This extremely intriguing pharmaceutical option is critically discussed including its potential and limitations. The review is starting off with an introduction to the metathesis and characterization of ILs, and leads over to examples for pharmaceutical application, including enhancement of dissolution rate and kinetic solubility and hygroscopicity adaptation, respectively. Tuning biopharmaceutics and toxicology by proper IL design is another focus. The review connects the interrelated chemical, physical, pharmaceutical, and toxicological outcome of API-ILs, serving as guidance for the formulation scientist who aims at expanding ones armamentarium for poorly water soluble APIs while avoiding structural modification, thereof. Copyright © 2015 Elsevier B.V. All rights reserved.

Effective Anti-miRNA Oligonucleotides Show High Releasing Rate of MicroRNA from RNA-Induced Silencing Complex.

PubMed

Ariyoshi, Jumpei; Matsuyama, Yohei; Kobori, Akio; Murakami, Akira; Sugiyama, Hiroshi; Yamayoshi, Asako

2017-10-01

MicroRNAs (miRNAs) regulate gene expression by forming RNA-induced silencing complexes (RISCs) and have been considered as promising therapeutic targets. MiRNA is an essential component of RISC for the modulation of gene expression. Therefore, the release of miRNA from RISC is considered as an effective method for the inhibition of miRNA functions. In our previous study, we reported that anti-miRNA oligonucleotides (AMOs), which are composed of the 2'-O-methyl (2'-OMe) RNA, could induce the release of miRNA from RISC. However, the mechanisms underlying the miRNA-releasing effects of chemically modified AMOs, which are conventionally used as anti-cancer drugs, are still unclear. In this study, we investigated the relationship between the miRNA releasing rate from RISC and the inhibitory effect on RISC activity (IC 50 ) using conventional chemically modified AMOs. We demonstrated that the miRNA-releasing effects of AMOs are directly proportional to the IC 50 values, and AMOs, which have an ability to promote the release of miRNA from RISC, can effectively inhibit RISC activity in living cells.

Tailor-made resealable micro(bio)reactors providing easy integration of in situ sensors

NASA Astrophysics Data System (ADS)

Viefhues, Martina; Sun, Shiwen; Valikhani, Donya; Nidetzky, Bernd; Vrouwe, Elwin X.; Mayr, Torsten; Bolivar, Juan M.

2017-06-01

Flow microreactors utilizing immobilized enzymes are of great interest in biocatalysis development. Most of the common devices are permanently closed, single-use systems, which allow limited physical and chemical surface modifications and evaluation methods. In this paper we will present resealable flowcells that overcome these limitations and moreover allow a quick and easy integration of sensor systems, because of the use of modular building blocks. The devices were utilized to study the enzyme activity of glucose oxidase immobilized on chemically modified glass surfaces under flow conditions, employing integrated optical oxygen sensors for on-line monitoring.

Antimicrobial 3D Porous Scaffolds Prepared by Additive Manufacturing and Breath Figures.

PubMed

Vargas-Alfredo, Nelson; Dorronsoro, Ane; Cortajarena, Aitziber L; Rodríguez-Hernández, Juan

2017-10-25

We describe herein a novel strategy for the fabrication of efficient 3D printed antibacterial scaffolds. For this purpose, both the surface topography as well as the chemical composition of 3D scaffolds fabricated by additive manufacturing were modified. The scaffolds were fabricated by fused deposition modeling (FDM) using high-impact polystyrene (HIPS) filaments. The surface of the objects was then topographically modified providing materials with porous surfaces by means of the Breath Figures approach. The strategy involves the immersion of the scaffold in a polymer solution during a precise period of time. This approach permitted the modification of the pore size varying the immersion time as well as the solution concentration. Moreover, by using polymer blend solutions of polystyrene and polystyrene-b-poly(acrylic acid) (PS 23 -b-PAA 18 ) and a quaternized polystyrene-b-poly(dimethylaminoethyl methacrylate) (PS 42 -b-PDMAEMAQ 17 ), the scaffolds were simultaneously chemically modified. The surfaces were characterized by scanning electron microscopy and infrared spectroscopy. Finally, the biological response toward bacteria was explored. Porous surfaces prepared using quaternized PDMAEMA as well as those prepared using PAA confer antimicrobial activity to the films, i.e., were able to kill on contact Staphylococcus aureus employed as model bacteria.

2’f-OMe-phosphorodithioate modified siRNAs show increased loading into the RISC complex and enhanced anti-tumour activity

PubMed Central

Wu, Sherry Y.; Yang, Xianbin; Gharpure, Kshipra M.; Hatakeyama, Hiroto; Egli, Martin; McGuire, Michael H.; Nagaraja, Archana S.; Miyake, Takahito M.; Rupaimoole, Rajesha; Pecot, Chad V.; Taylor, Morgan; Pradeep, Sunila; Sierant, Malgorzata; Rodriguez-Aguayo, Cristian; Choi, Hyun J.; Previs, Rebecca A.; Armaiz-Pena, Guillermo N.; Huang, Li; Martinez, Carlos; Hassell, Tom; Ivan, Cristina; Sehgal, Vasudha; Singhania, Richa; Han, Hee-Dong; Su, Chang; Kim, Ji Hoon; Dalton, Heather J.; Kowali, Chandra; Keyomarsi, Khandan; McMillan, Nigel A.J.; Overwijk, Willem W.; Liu, Jinsong; Lee, Ju-Seog; Baggerly, Keith A.; Lopez-Berestein, Gabriel; Ram, Prahlad T.; Nawrot, Barbara; Sood, Anil K.

2014-01-01

Improving small interfering RNA (siRNA) efficacy in target cell populations remains a challenge to its clinical implementation. Here, we report a chemical modification, consisting of phosphorodithioate (PS2) and 2’-O-Methyl (2’-OMe) MePS2 on one nucleotide that significantly enhances potency and resistance to degradation for various siRNAs. We find enhanced potency stems from an unforeseen increase in siRNA loading to the RNA-induced silencing complex, likely due to the unique interaction mediated by 2’-OMe and PS2. We demonstrate the therapeutic utility of MePS2 siRNAs in chemoresistant ovarian cancer mouse models via targeting GRAM Domain Containing 1B (GRAMD1B), a protein involved in chemoresistance. GRAMD1B silencing is achieved in tumors following MePS2-modified siRNA treatment, leading to a synergistic anti-tumor effect in combination with paclitaxel. Given the previously limited success in enhancing siRNA potency with chemically modified siRNAs, our findings represent an important advance in siRNA design with the potential for application in numerous cancer types. PMID:24619206

High Photocatalytic Performance of Two Types of Graphene Modified TiO2 Composite Photocatalysts

NASA Astrophysics Data System (ADS)

Zhang, Jun; Li, Sen; Tang, Bo; Wang, Zhengwei; Ji, Guojian; Huang, Weiqiu; Wang, Jinping

2017-07-01

High quality and naturally continuous structure of three-dimensional graphene network (3DGN) endow it a promising candidate to modify TiO2. Although the resulting composite photocatalysts display outstanding performances, the lacking of active sites of the 3DGN not only goes against a close contact between the graphene basal plane and TiO2 nanoparticles (weaken electron transport ability) but also limits the efficient adsorption of pollutant molecules. Similar with surface functional groups of the reduced graphene oxide (RGO) nanosheets, surface defects of the 3DGN can act as the adsorption sites. However, the defect density of the 3DGN is difficult to control (a strict cool rate of substrate and a strict flow of precursor gas are necessary) because of its growth approach (chemical vapor deposition method). In this study, to give full play to the functions of graphene, the RGO nanosheets and 3DGN co-modified TiO2 composite photocatalysts are prepared. After optimizing the mass fraction of the RGO nanosheets in the composite photocatalyst, the resulting chemical adsorption ability and yields of strong oxidizing free radicals increase significantly, indicating the synergy of the RGO nanosheets and 3DGN.

Rho-associated kinase (ROCK) inhibition reverses low cell activity on hydrophobic surfaces.

PubMed

Tian, Yu Shun; Kim, Hyun Jung; Kim, Hyun-Man

2009-08-28

Hydrophobic polymers do not offer an adequate scaffold surface for cells to attach, migrate, proliferate, and differentiate. Thus, hydrophobic scaffolds for tissue engineering have traditionally been physicochemically modified to enhance cellular activity. However, modifying the surface by chemical or physical treatment requires supplementary engineering procedures. In the present study, regulation of a cell signal transduction pathway reversed the low cellular activity on a hydrophobic surface without surface modification. Inhibition of Rho-associated kinase (ROCK) by Y-27632 markedly enhanced adhesion, migration, and proliferation of osteoblastic cells cultured on a hydrophobic polystyrene surface. ROCK inhibition regulated cell-cycle-related molecules on the hydrophobic surface. This inhibition also decreased expression of the inhibitors of cyclin-dependent kinases such as p21(cip1) and p27(kip1) and increased expression of cyclin A and D. These results indicate that defective cellular activity on the hydrophobic surface can be reversed by the control of a cell signal transduction pathway without physicochemical surface modification.

Enhancement of the Norfloxacin Antibiotic Activity by Gaseous Contact with the Essential Oil of Croton zehntneri

PubMed Central

Coutinho, HDM; Matias, EFF; Santos, KKA; Tintino, SR; Souza, CES; Guedes, GMM; Santos, FAD; Costa, JGM; Falcão-Silva, VS; Siqueira-Júnior, JP

2010-01-01

This is the first on the modulation of norfloxacin antibiotic activity by the volatile compounds of an essential oil. We report the chemical composition and antibiotic modifying activity of the essential oil extracted from the leaves of Croton zehntneri Pax et Hoffm (variety estragole), using the minimal inhibitory dose method and gaseous contact. The leaves of Croton zehntneri Pax et Hoffm (Euphorbiaceae) were subjected to hydrodistillation, and the essential oil extracted was examined with respect to the chemical composition, by gas chromatography-mass spectrometry (GC/MS), and to inhibitory activity of efflux pump by gaseous contact. The main component of the essential oil of C. zehntneri was estragole (76,8%). The gaseous components of the oil enhanced the inhibition zone of norfloxacin in 39,5%. This result shows that this oil influences the antibiotic activity of norfloxacin, possibly affecting the bacterial NorA efflux system, and may be used as an adjuvant in the antibiotic therapy of multidrug resistant pathogens. PMID:21264094

A mechanism-mediated model for carcinogenicity: Model content and prediction of the outcome of rodent carcinogenicity bioassays currently being conducted on 25 organic chemicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purdy, R.

A hierarchical model consisting of quantitative structure-activity relationships based mainly on chemical reactivity was developed to predict the carcinogenicity of organic chemicals to rodents. The model is comprised of quantitative structure-activity relationships, QSARs based on hypothesized mechanisms of action, metabolism, and partitioning. Predictors included octanol/water partition coefficient, molecular size, atomic partial charge, bond angle strain, atomic acceptor delocalizibility, atomic radical superdelocalizibility, the lowest unoccupied molecular orbital (LUMO) energy of hypothesized intermediate nitrenium ion of primary aromatic amines, difference in charge of ionized and unionized carbon-chlorine bonds, substituent size and pattern on polynuclear aromatic hydrocarbons, the distance between lone electron pairsmore » over a rigid structure, and the presence of functionalities such as nitroso and hydrazine. The model correctly classified 96% of the carcinogens in the training set of 306 chemicals, and 90% of the carcinogens in the test set of 301 chemicals. The test set by chance contained 84% of the positive thiocontaining chemicals. A QSAR for these chemicals was developed. This posttest set modified model correctly predicted 94% of the carcinogens in the test set. This model was used to predict the carcinogenicity of the 25 organic chemicals the U.S. National Toxicology Program was testing at the writing of this article. 12 refs., 3 tabs.« less

Sterically controlled mechanochemistry under hydrostatic pressure

DOE PAGES

Yan, Hao; Yang, Fan; Pan, Ding; ...

2018-02-21

Mechanical stimuli can modify the energy landscape of chemical reactions and enable reaction pathways, offering a synthetic strategy that complements conventional chemistry. These mechanochemical mechanisms have been studied extensively in one-dimensional polymers under tensile stress using ring-opening and reorganization, polymer unzipping and disulfide reduction as model reactions. In these systems, the pulling force stretches chemical bonds, initiating the reaction. Additionally, it has been shown that forces orthogonal to the chemical bonds can alter the rate of bond dissociation. Furthermore, these bond activation mechanisms have not been possible under isotropic, compressive stress (that is, hydrostatic pressure). Here we show that mechanochemistrymore » through isotropic compression is possible by molecularly engineering structures that can translate macroscopic isotropic stress into molecular-level anisotropic strain.« less

A sustainable slashing industry using biodegradable sizes from modified soy protein to replace petro-based poly(vinyl alcohol).

PubMed

Zhao, Yi; Zhao, Yuzhu; Xu, Helan; Yang, Yiqi

2015-02-17

Biodegradable sizing agents from triethanolamine (TEA) modified soy protein could substitute poly(vinyl alcohol)(PVA) sizes for high-speed weaving of polyester and polyester/cotton yarns to substantially decrease environmental pollution and impel sustainability of textile industry. Nonbiodegradable PVA sizes are widely used and mainly contribute to high chemical oxygen demand (COD) in textile effluents. It has not been possible to effectively degrade, reuse or replace PVA sizes so far. Soy protein with good biodegradability showed potential as warp sizes in our previous studies. However, soy protein sizes lacked film flexibility and adhesion for required high-speed weaving. Additives with multiple hydroxyl groups, nonlinear molecule, and electric charge could physically modify secondary structure of soy protein and lead to about 23.6% and 43.3% improvement in size adhesion and ability of hair coverage comparing to unmodified soy protein. Industrial weaving results showed TEA-soy protein had relative weaving efficiency 3% and 10% higher than PVA and chemically modified starch sizes on polyester/cotton fabrics, and had relative weaving efficiency similar to PVA on polyester fabrics, although with 3- 6% lower add-on. In addition, TEA-soy sizes had a BOD5/COD ratio of 0.44, much higher than 0.03 for PVA, indicating that TEA-soy sizes were easily biodegradable in activated sludge.

Methods for attaching polymerizable ceragenins to water treatment membranes using amine and amide linkages

DOEpatents

Hibbs, Michael; Altman, Susan J.; Jones, Howland D.T.; Savage, Paul B.

2013-10-15

This invention relates to methods for chemically grafting and attaching ceragenin molecules to polymer substrates; methods for synthesizing ceragenin-containing copolymers; methods for making ceragenin-modified water treatment membranes and spacers; and methods of treating contaminated water using ceragenin-modified treatment membranes and spacers. Ceragenins are synthetically produced antimicrobial peptide mimics that display broad-spectrum bactericidal activity. Alkene-functionalized ceragenins (e.g., acrylamide-functionalized ceragenins) can be attached to polyamide reverse osmosis membranes using amine-linking, amide-linking, UV-grafting, or silane-coating methods. In addition, silane-functionalized ceragenins can be directly attached to polymer surfaces that have free hydroxyls.

Methods for attaching polymerizable ceragenins to water treatment membranes using silane linkages

DOEpatents

Hibbs, Michael; Altman, Susan J.; Jones, Howland D. T.; Savage, Paul B.

2013-09-10

This invention relates to methods for chemically grafting and attaching ceragenin molecules to polymer substrates; methods for synthesizing ceragenin-containing copolymers; methods for making ceragenin-modified water treatment membranes and spacers; and methods of treating contaminated water using ceragenin-modified treatment membranes and spacers. Ceragenins are synthetically produced antimicrobial peptide mimics that display broad-spectrum bactericidal activity. Alkene-functionalized ceragenins (e.g., acrylamide-functionalized ceragenins) can be attached to polyamide reverse osmosis membranes using amine-linking, amide-linking, UV-grafting, or silane-coating methods. In addition, silane-functionalized ceragenins can be directly attached to polymer surfaces that have free hydroxyls.

Different Interfacial Behaviors of Peptides Chemically Immobilized on Surfaces with Different Linker Lengths and via Different Termini

DTIC Science & Technology

2014-02-20

spectroscopy was applied to investigate such structures of peptides immobilized on self-assembled monolayers (SAMs). Here cysteine-modified antimicrobial ...modified antimicrobial peptide cecropin P1 (CP1) was chemically immobilized onto SAM with a maleimide terminal group. Two important characteristics...applied to investigate such structures of peptides immobilized on self-assembled monolayers (SAMs). Here cysteine-modified antimicrobial peptide cecropin

Cyclodextrins: A Weapon in the Fight Against Antimicrobial Resistance

NASA Astrophysics Data System (ADS)

Wong, Chew Ee; Dolzhenko, Anton V.; Lee, Sui Mae; Young, David James

Antimicrobial resistance poses one of the most serious global challenges of our age. Cyclodextrins (CDs) are widely utilized excipients in formulations because of their solubilizing properties, low toxicity, and low inflammatory response. This review summarizes recent investigations of antimicrobial agents involving CDs and CD-based antimicrobial materials. CDs have been employed for antimicrobial applications either through formation of inclusion complexes or by chemical modification of their hydroxyl groups to tailor pharmaceutically active compounds. Applications of these CD inclusion complexes include drug delivery, antimicrobial coatings on materials (e.g., biomedical devices and implants) and antimicrobial dressings that help to prevent wound infections. There are relatively limited studies of chemically modified CDs with antimicrobial activity. The mechanism of action of antimicrobial CD inclusion complexes and derivatives needs further elucidation, but activity of CDs and their derivatives is often associated with their interaction with bacterial cell membranes.

Isolation of bacterial metabolites as natural inducers for larval settlement in the marine polychaete Hydroides elegans (Haswell).

PubMed

Harder, Tilmann; Lau, Stanley Chun Kwan; Dahms, Hans-Uwe; Qian, Pei-Yuan

2002-10-01

The bacterial component of marine biofilms plays an important role in the induction of larval settlement in the polychaete Hydroides elegans. In this study, we provide experimental evidence that bacterial metabolites comprise the chemical signal for larval settlement. Bacteria were isolated from biofilms, purified and cultured according to standard procedures. Bacterial metabolites were isolated from spent culture broth by chloroform extraction as well as by closed-loop stripping and adsorption of volatile components on surface-modified silica gel. A pronounced biological activity was exclusively observed when concentrated metabolites were adsorbed on activated charcoal. Larvae did not respond to waterbome metabolites when prevented from contacting the bacterial film surface. These results indicate that an association of the chemical signal with a sorbent-like substratum may be an essential cofactor for the expression of biological activity. The functional role of bacterial exopolymers as an adsorptive matrix for larval settlement signals is discussed.

Study of the surface activation of ETFE by low energy (keV) Si and N bombardment

NASA Astrophysics Data System (ADS)

Parada, M. A.; de Almeida, A.; Muntele, C.; Muntele, I.; Delalez, N.; Ila, D.

2005-12-01

The ethylenetetrafluoroethylene (ETFE) is a polymer formed by alternating ethylene and tetrafluoroethylene segments. It can be applied in the field of medical physics as intra venous catheters and as radiation dosimeters. The increasing application of polymeric materials in technological and scientific fields has motivated the use of surface treatments to modify the physical and chemical properties of polymer surfaces. When a material is exposed to ionizing radiation, it suffers damage leading to surface activation depending on the type, energy and intensity of the applied radiation. In order to determine the radiation damage and the surface activation mechanism ETFE films were bombarded with keV Si and N at various fluences. The bombarded film was also analyzed with optical absorption photospectrometry (OAP), Raman and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy showing quantitatively the chemical nature at the damage caused by the Si and N bombardment.

Treating respiratory viral diseases with chemically modified, second generation intranasal siRNAs.

PubMed

Barik, Sailen

2009-01-01

Chemically synthesized short interfering RNA (siRNA) of pre-determined sequence has ushered a new era in the application of RNA interference (RNAi) against viral genes. We have paid particular attention to respiratory viruses that wreak heavy morbidity and mortality worldwide. The clinically significant ones include respiratory syncytial virus (RSV), parainfluenza virus (PIV) and influenza virus. As the infection by these viruses is clinically restricted to the respiratory tissues, mainly the lungs, the logical route for the application of the siRNA was also the same, i.e., via the nasal route. Following the initial success of intranasal siRNA against RSV, second-generation siRNAs were made against the viral polymerase large subunit (L) that were chemically modified and screened for improved stability, activity and pharmacokinetics. 2'-O-methyl (2'-O-Me) and 2'-deoxy-2'-fluoro (2'-F) substitutions in the ribose ring were incorporated in different positions of the sense and antisense strands and the resultant siRNAs were tested with various transfection reagents intranasally against RSV. Based on these results, we propose the following consensus for designing intranasal antiviral siRNAs: (i) modified 19-27 nt long double-stranded siRNAs are functional in the lung, (ii) excessive 2'-OMe and 2'-F modifications in either or both strands of these siRNAs reduce efficacy, and (iii) limited modifications in the sense strand are beneficial, although their precise efficacy may be position-dependent.

Mesoporous Silica Nanoparticle Delivery of Chemically Modified siRNA Against TWIST1 Leads to Reduced Tumor Burden

PubMed Central

Finlay, James; Roberts, Cai M.; Dong, Juyao; Zink, Jeffrey I.; Tamanoi, Fuyuhiko; Glackin, Carlotta A.

2015-01-01

Growth and progression of solid tumors depends on the integration of multiple pro-growth and survival signals, including the induction of angiogenesis. TWIST1 is a transcription factor whose reactivation in tumors leads to epithelial to mesenchymal transition (EMT), including increased cancer cell stemness, survival, and invasiveness. Additionally, TWIST1 drives angiogenesis via activation of IL-8 and CCL2, independent of VEGF signaling. In this work, results suggest that chemically modified siRNA against TWIST1 reverses EMT both in vitro and in vivo. siRNA delivery with a polyethyleneimine-coated mesoporous silica nanoparticle (MSN) led to reduction of TWIST1 target genes and migratory potential in vitro. In mice bearing xenograft tumors, weekly intravenous injections of the siRNA-nanoparticle complexes resulted in decreased tumor burden together with a loss of CCL2 suggesting a possible anti-angiogenic response. Therapeutic use of TWIST1 siRNA delivered via MSNs has the potential to inhibit tumor growth and progression in many solid tumor types. Chemically modified siRNA against TWIST1 was complexed to cation-coated mesoporous silica nanoparticles and tested in vitro and in vivo. In cell culture experiments, siRNA reduced expression of TWIST1 and its target genes, and reduced cell migration. In mice, injections of the siRNA-nanoparticle complex led to reduced tumor weight. Data suggest that diminished tumor burden was the result of reduced CCL2 expression and angiogenesis following TWIST1 knockdown. PMID:26115637

An empirical study on the preparation of the modified coke and its catalytic oxidation properties

NASA Astrophysics Data System (ADS)

Liu, Hao; Jiang, Wenqiang

2017-05-01

T As a methyl acrylic ester fungicide, pyraclostrobin has the advantages of high activity, wide sterilization spectrum and high safety level comparing with the traditional fungicide. Due to less toxicity and side effects on human and environment, the use of pyraclostrobin and its mixture in agriculture is increasing. The heavy use of pyraclostrobin will inevitably cause pollution to the biological and abiotic environment. Therefore, it is of great significance to do the research on the degradation of pyraclostrobin. In this study, coke, as matrix, was modified by chemical modification. The modified coke was used as the catalyst and the pyraclostrobin was used as the degradation object. The degradation experiment of pyraclostrobin was carried out by using catalytic oxidation. The catalytic oxidation performance of modified coke was studied. The result showed that in the catalytic oxidation system of using modified coke as catalyst and H2O2 as oxidant, the best reaction condition is as following: The modified coke which is modified by using 70% concentration nitric acid is used as catalyst; The dosage of the catalyst is10g; The dosage of H2O2 is 0.6ml; The reaction time is 6 hours.

Can vaccinia virus be replaced by MVA virus for testing virucidal activity of chemical disinfectants?

PubMed

Rabenau, Holger F; Rapp, Ingrid; Steinmann, Jochen

2010-06-23

Vaccinia virus strain Lister Elstree (VACV) is a test virus in the DVV/RKI guidelines as representative of the stable enveloped viruses. Since the potential risk of laboratory-acquired infections with VACV persists and since the adverse effects of vaccination with VACV are described, the replacement of VACV by the modified vaccinia Ankara strain (MVA) was studied by testing the activity of different chemical biocides in three German laboratories. The inactivating properties of different chemical biocides (peracetic acid, aldehydes and alcohols) were tested in a quantitative suspension test according to the DVV/RKI guideline. All tests were performed with a protein load of 10% fetal calf serum with both viruses in parallel using different concentrations and contact times. Residual virus was determined by endpoint dilution method. The chemical biocides exhibited similar virucidal activity against VACV and MVA. In three cases intra-laboratory differences were determined between VACV and MVA - 40% (v/v) ethanol and 30% (v/v) isopropanol are more active against MVA, whereas MVA seems more stable than VACV when testing with 0.05% glutardialdehyde. Test accuracy across the three participating laboratories was high. Remarkably inter-laboratory differences in the reduction factor were only observed in two cases. Our data provide valuable information for the replacement of VACV by MVA for testing chemical biocides and disinfectants. Because MVA does not replicate in humans this would eliminate the potential risk of inadvertent inoculation with vaccinia virus and disease in non-vaccinated laboratory workers.

A novel computational method to simulate non-enzymatic self-replication. [Abstract only

NASA Technical Reports Server (NTRS)

Navarro-Gonzalez, Rafael; Reggia, James A.; Wu, Jayoung; Chou, Hui-Hsien

1994-01-01

Non-enzymatic, template-directed synthesis of oligonucleotides has been extensively studied in the laboratory as a model to understand the kind of chemical processes that might have contributed to the origin of life on Earth. Several oligonucleotides have been shown to catalyze the synthesis of their complements from activated mononucleotides; however, a restricted number of them have been found to self-replicate. Recently we developed an efficient modified cellular automata method that supports the study of self-replicating oligonucleotides. With this method the oligonucleotide molecules are represented as active cells imbedded in a two-dimensional array of inactive cells symbolizing the environment. Random movements and probability-governed chemical reactions occurring in a cellular space can effectively simulate the experimental behavior observed in self-directed replication of oligonucleotides.

Use Zircon-Ilmenite Concentrate in Steelmaking

NASA Astrophysics Data System (ADS)

Fedoseev, S. N.; Volkova, T. N.

2016-08-01

Market requirements cause a constant search for new materials and technologies, for their immediate use in increasing requirements for material and energy efficiency, as well as to the quality of steel. In practice, steel production in the tended recently of more stringent requirements for the chemical composition of the steel and its contamination by nonmetallic inclusions, gas and non-ferrous metals. The main ways of increasing of strength and performance characteristics fabricated metal products related to the profound and effective influence on the crystallizing metal structure by furnace processing of the melt with refining and modifying additives. It can be argued that the furnace processing of steel and iron chemically active metals (alkali-earth metals, rare-earth metals, and others.) is an integral part of modern production of high quality products and competitive technologies. Important condition for development of methods secondary metallurgy of steel is the use of relatively inexpensive materials in a variety of complex alloys and blends, allowing targeted control of physical and chemical state of the molten metal and, therefore, receive steel with improved performance. In this connection the development of modifying natural materials metallurgy technologies presented complex ores containing titanium and zirconium, is a very urgent task.

Bioimaging of Nucleolin Aptamer-Containing 5-(N-benzylcarboxyamide)-2′-deoxyuridine More Capable of Specific Binding to Targets in Cancer Cells

PubMed Central

Lee, Kyue Yim; Kang, Hyungu; Ryu, Sung Ho; Lee, Dong Soo; Lee, Jung Hwan; Kim, Soonhag

2010-01-01

Chemically modified nucleotides have been developed and applied into SELEX procedure to find a novel type of aptamers to fit with targets of interest. In this study, we directly performed chemical modification of 5-(N-benzylcarboxyamide)-2′-deoxyuridine (called 5-BzdU) in the AS1411 aptamer, which binds to the nucleolin protein expressed in cancer cells. Forty-seven compounds of AS1411-containing Cy3-labeled 5-BzdU (called Cy3-(5-BzdU)-modified-AS1411) were synthesized by randomly substituting thymidines one to twelve in AS1411 with Cy3-labeled 5-BzdU. Both statistically quantified fluorescence measurements and confocal imaging analysis demonstrated at least three potential compounds of interest: number 12, 29 and 41 that significantly increased the targeting affinity to cancer cells but no significant activity from normal healthy cells. These results suggest that the position and number of substituents in AS1411 are critical parameters to improve the aptamer function. In this study, we demonstrated that chemical modification of the existing aptamers enhanced the binding and targeting affinity to targets of interest without additional SELEX procedures. PMID:20204158

Chemical treatment of the intra-canal dentin surface: a new approach to modify dentin hydrophobicity

PubMed Central

GAITAN-FONSECA, Cesar; COLLART-DUTILLEUL, Pierre-Yves; SEMETEY, Vincent; ROMIEU, Olivier; CRUZ, Roel; FLORES, Hector; CUISINIER, Frédéric; PÉREZ, Elías; POZOS-GUILLEN, Amaury

2013-01-01

Objective: This study evaluated the hydrophobicity of dentin surfaces that were modified through chemical silanization with octadecyltrichlorosilane (OTS). Material and Methods: An in vitro experimental study was performed using 40 human permanent incisors that were divided into the following two groups: non-silanized and silanized. The specimens were pretreated and chemically modified with OTS. After the chemical modification, the dentin hydrophobicity was examined using a water contact angle measurement (WCA). The effectiveness of the modification of hydrophobicity was verified by the fluid permeability test (FPT). Results and Conclusions: Statistically significant differences were found in the values of WCA and FPT between the two groups. After silanization, the hydrophobic intraradicular dentin surface exhibited in vitro properties that limit fluid penetration into the sealed root canal. This chemical treatment is a new approach for improving the sealing of the root canal system. PMID:23559114

A novel carbon electrode material for highly improved EDLC performance.

PubMed

Fang, Baizeng; Binder, Leo

2006-04-20

Porous materials, developed by grafting functional groups through chemical surface modification with a surfactant, represent an innovative concept in energy storage. This work reports, in detail, the first practical realization of a novel carbon electrode based on grafting of vinyltrimethoxysilane (vtmos) functional group for energy storage in electric double layer capacitor (EDLC). Surface modification with surfactant vtmos enhances the hydrophobisation of activated carbon and the affinity toward propylene carbonate (PC) solvent, which improves the wettability of activated carbon in the electrolyte solution based on PC solvent, resulting in not only a lower resistance to the transport of electrolyte ions within micropores of activated carbon but also more usable surface area for the formation of electric double layer, and accordingly, higher specific capacitance, energy density, and power capability available from the capacitor based on modified carbon. Especially, the effects from surface modification become superior at higher discharge rate, at which much better EDLC performance (i.e., much higher energy density and power capability) has been achieved by the modified carbon, suggesting that the modified carbon is a novel and very promising electrode material of EDLC for large current applications where both high energy density and power capability are required.

Strategies for emission reduction of air pollutants produced from a chemical plant.

PubMed

Lee, Byeong-Kyu; Cho, Sung-Woong

2003-01-01

Various air pollution control (APC) techniques were employed in order to reduce emissions of air pollutants produced from chemical plants, which have many different chemical production facilities. For an emission reduction of acid gases, this study employed a method to improve solubility of pollutants by decreasing the operating temperature of the scrubbers, increasing the surface area for effective contact of gas and liquid, and modifying processes in the acid scrubbers. To reduce emission of both amines and acid gases, pollutant gas components were first separated, then condensation and/or acid scrubbing, depending on the chemical and physical properties of pollutant components, were used. To reduce emission of solvents, condensation and activated carbon adsorption were employed. To reduce emission of a mixture gases containing acid gases and solvents, the mixed gases were passed into the first condenser, the acid scrubber, the second condenser, and the activated carbon adsorption tower in sequence. As a strategy to reduce emission of pollutants at the source, this study also employed the simple pollution prevention concept of modification of the previously operating APC control device. Finally, air emissions of pollutants produced from the chemical plants were much more reduced by applying proper APC methods, depending upon the types (physical or chemical properties) and the specific emission situations of pollutants.

Chemical modification of L-asparaginase from Cladosporium sp. for improved activity and thermal stability.

PubMed

Mohan Kumar, N S; Kishore, Vijay; Manonmani, H K

2014-01-01

L-Asparaginase (ASNase), an antileukemia enzyme, is facing problems with antigenicity in the blood. Modification of L-asparaginase from Cladosporium sp. was tried to obtain improved stability and improved functionality. In our experiment, modification of the enzyme was tried with bovine serum albumin, ovalbumin by crosslinking using glutaraldehyde, N-bromosuccinimide, and mono-methoxy polyethylene glycol. Modified enzymes were studied for activity, temperature stability, rate constants (kd), and protection to proteolytic digestion. Modification with ovalbumin resulted in improved enzyme activity that was 10-fold higher compared to native enzyme, while modification with bovine serum albumin through glutaraldehyde cross-linking resulted in high stability of L-asparaginase that was 8.5- and 7.62-fold more compared to native enzyme at 28°C and 37°C by the end of 24 hr. These effects were dependent on the quantity of conjugate formed. Modification also markedly prolonged L-asparaginase half-life and serum stability. N-Bromosuccinimide-modified ASNase presented greater stability with prolonged in vitro half-life of 144 hr to proteolytic digestion relative to unmodified enzyme (93 h). The present work could be seen as producing a modified L-asparaginase with improved activity and stability and can be a potential source for developing therapeutic agents for cancer treatment.

Screening complex hazardous wastes for mutagenic activity using a modified version of the TLC/Salmonella assay.

PubMed

Houk, V S; Claxton, L D

1986-03-01

10 complex hazardous wastes were tested for mutagenic activity using a modified version of the TLC/Salmonella assay developed by Bjørseth et al. (1982). This fractionation/bioassay scheme couples thin-layer chromatography (TLC) with the Salmonella/mammalian-microsome (Ames) assay for the detection of mutagenic constituents in complex mixtures. Crude (unadulterated) hazardous wastes and selected hazardous waste extracts were fractionated on commercially available cellulose TLC plates. Mutagenicity testing was performed in situ by applying a single overlay of minimal growth agar, tester strain TA98 or TA100, and the optional metabolic activation system directly onto the developed chromatogram. A mutagenic effect was indicated either by the appearance of localized clusters of revertant colonies or by an increase in total revertant growth vis-à-vis control plates. 7 of 10 hazardous wastes (including tars, emulsions, sludges, and spent acids and caustics) demonstrated mutagenic activity when tested by this method. To assess the sensitivity of the modified TLC/Salmonella assay, 14 Salmonella mutagens from a wide range of chemical classes and polarities were tested. Selected compounds included heterocyclics, aromatic amines, alkylating agents, antitumor agents, a nitrosamine and a nitroaromatic. 11 of the 14 mutagens were positive in this test system. The 3 compounds refractory to analysis included a polycyclic aromatic hydrocarbon and two volatiles.

Chemical analysis and biological testing of materials from the EDS coal liquefaction process: a status report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Later, D.W.; Pelroy, R.A.; Wilson, B.W.

1984-05-01

Representative process materials were obtained from the EDS pilot plant for chemical and biological analyses. These materials were characterized for biological activity and chemical composition using a microbial mutagenicity assay and chromatographic and mass spectrometric analytical techniques. The two highest boiling distillation cuts, as well as process solvent (PS) obtained from the bottoms recycle mode operation, were tested for initiation of mouse skin tumorigenicity. All three materials were active; the crude 800/sup 0 +/F cut was substantially more potent than the crude bottoms recycle PS or 750 to 800/sup 0/F distillate cut. Results from chemical analyses showed the EDS materials,more » in general, to be more highly alkylated and have higher hydroaromatic content than analogous SRC II process materials (no in-line process hydrogenation) used for comparison. In the microbial mutagenicity assays the N-PAC fractions showed greater activity than did the aliphatic hydrocarbon, hydroxy-PAH, or PAH fractions, although mutagenicity was detected in certain PAH fractions by a modified version of the standard microbial mutagenicity assay. Mutagenic activities for the EDS materials were lower, overall, than those for the corresponding materials from the SRC II process. The EDS materials produced under different operational modes had distinguishable differences in both their chemical constituency and biological activity. The primary differences between the EDS materials studied here and their SRC II counterparts used for comparison are most likely attributable to the incorporation of catalytic hydrogenation in the EDS process. 27 references, 28 figures, 27 tables.« less

Chemically modified tetracycline-3 (CMT-3): a novel inhibitor of the serine proteinase, elastase.

PubMed

Gu, Ying; Lee, Hsi-Ming; Simon, Sanford R; Golub, Lorne M

2011-12-01

Two classes of enzymes play an important role in connective tissue breakdown during various inflammatory diseases: serine proteinases and matrix metalloproteinases (MMPs). Tetracyclines (TCs) exhibit important anti-inflammatory and MMP-inhibitory properties that are unrelated to their antibacterial activities. Of the various TCs and their chemically modified NON-antibiotic analogs (CMTs) tested in vitro and in vivo, CMT-3 (6-demethyl-6-deoxy 4 de-dimethylamino tetracycline) has repeatedly been shown to be the most potent inhibitor of MMP activity and cytokine production. In addition to its anti-MMP function, we have shown that among all CMTs, CMT-3 is the only CMT that can also directly inhibit both the amidolytic activity of human leukocyte elastase (HLE, a serine proteinase) and the extracellular matrix degradation mediated by HLE. In addition, CMT-3 has been found to reduce leukocyte elastase activity in vivo in gingival extracts of rats with experimental periodontal disease. Thus, CMT-3 can inhibit pathologic connective tissue breakdown by (at least) two mechanisms: direct inhibition of neutral proteinases (elastase and MMPs); and protecting their endogenous inhibitors, α(1)-PI and TIMPs, from being digested and inactivated by MMPs and HLE, respectively. The pleiotropic properties of CMT-3 including (but not limited to) inhibition of serine proteinases, MMPs, and cytokines provide impressive therapeutic potential to reduce excessive connective tissue breakdown during various pathologic processes including inflammatory diseases, cancer metastasis and metabolic bone diseases. Copyright © 2011 Elsevier Ltd. All rights reserved.

Alkylation of histidine residues of Bothrops jararacussu venom proteins and isolated phospholipases A2: a biotechnological tool to improve the production of antibodies.

PubMed

Guimarães, C L S; Andrião-Escarso, S H; Moreira-Dill, L S; Carvalho, B M A; Marchi-Salvador, D P; Santos-Filho, N A; Fernandes, C A H; Fontes, M R M; Giglio, J R; Barraviera, B; Zuliani, J P; Fernandes, C F C; Calderón, L A; Stábeli, R G; Albericio, F; da Silva, S L; Soares, A M

2014-01-01

Crude venom of Bothrops jararacussu and isolated phospholipases A2 (PLA2) of this toxin (BthTX-I and BthTX-II) were chemically modified (alkylation) by p-bromophenacyl bromide (BPB) in order to study antibody production capacity in function of the structure-function relationship of these substances (crude venom and PLA2 native and alkylated). BthTX-II showed enzymatic activity, while BthTX-I did not. Alkylation reduced BthTX-II activity by 50% while this process abolished the catalytic and myotoxic activities of BthTX-I, while reducing its edema-inducing activity by about 50%. Antibody production against the native and alkylated forms of BthTX-I and -II and the cross-reactivity of antibodies to native and alkylated toxins did not show any apparent differences and these observations were reinforced by surface plasmon resonance (SPR) data. Histopathological analysis of mouse gastrocnemius muscle sections after injection of PBS, BthTX-I, BthTX-II, or both myotoxins previously incubated with neutralizing antibody showed inhibition of the toxin-induced myotoxicity. These results reveal that the chemical modification of the phospholipases A2 (PLA2) diminished their toxicity but did not alter their antigenicity. This observation indicates that the modified PLA2 may provide a biotechnological tool to attenuate the toxicity of the crude venom, by improving the production of antibodies and decreasing the local toxic effects of this poisonous substance in animals used to produce antivenom.

Engineering surfaces for bioconjugation: developing strategies and quantifying the extent of the reactions.

PubMed

Gauvreau, Virginie; Chevallier, Pascale; Vallières, Karine; Petitclerc, Eric; Gaudreault, René C; Laroche, Gaétan

2004-01-01

This study presents two-step and multistep reactions for modifying the surface of plasma-functionalized poly(tetrafluoroethylene) (PTFE) surfaces for subsequent conjugation of biologically relevant molecules. First, PTFE films were treated by a radiofrequency glow discharge (RFGD) ammonia plasma to introduce amino groups on the fluoropolymer surface. This plasma treatment is well optimized and allows the incorporation of a relative surface concentration of approximately 2-3.5% of amino groups, as assessed by chemical derivatization followed by X-ray photoelectron spectroscopy (XPS). In a second step, these amino groups were further reacted with various chemical reagents to provide the surface with chemical functionalities such as maleimides, carboxylic acids, acetals, aldehydes, and thiols, that could be used later on to conjugate a wide variety of biologically relevant molecules such as proteins, DNA, drugs, etc. In the present study, glutaric and cis-aconitic anhydrides were evaluated for their capability to provide carboxylic functions to the PTFE plasma-treated surface. Bromoacetaldehyde diethylacetal was reacted with the aminated PTFE surface, providing a diethylacetal function, which is a latent form of aldehyde functionality. Reactions with cross-linkers such as sulfo-succinimidyl derivatives (sulfo-SMCC, sulfo-SMPB) were evaluated to provide a highly reactive maleimide function suitable for further chemical reactions with thiolated molecules. Traut reagent (2-iminothiolane) was also conjugated to introduce a thiol group onto the fluoropolymer surface. PTFE-modified surfaces were analyzed by XPS with a particular attention to quantify the extent of the reactions that occurred on the polymer. Finally, surface immobilization of fibronectin performed using either glutaric anhydride or sulfo-SMPB activators demonstrated the importance of selecting the appropriate conjugation strategy to retain the protein biological activity.

Surface modification and electrochemical properties of activated carbons for supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Yang, Dan; Qiu, Wenmei; Xu, Jingcai; Han, Yanbing; Jin, Hongxiao; Jin, Dingfeng; Peng, Xiaoling; Hong, Bo; Li, Ji; Ge, Hongliang; Wang, Xinqing

2015-12-01

Modifications with different acids (HNO3, H2SO4, HCl and HF, respectively) were introduced to treat the activated carbons (ACs) surface. The microstructures and surface chemical properties were discussed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), ASAP, Raman spectra and Fourier transform infrared (FTIR) spectra. The ACs electrode-based supercapacitors were assembled with 6 mol ṡ L-1 KOH electrolyte. The electrochemical properties were studied by galvanostatic charge-discharge and cyclic voltammetry. The results indicated that although the BET surface area of modified ACs decreased, the functional groups were introduced and the ash contents were reduced on the surface of ACs, receiving larger specific capacitance to initial AC. The specific capacitance of ACs modified with HCl, H2SO4, HF and HNO3 increased by 31.4%, 23%, 21% and 11.6%, respectively.

Chemical Carcinogen-Induced Changes in tRNA Metabolism in Human Cells.

DTIC Science & Technology

1981-11-01

the resolution and quantitation of modified ucleosides in the urine of cancer patients would not be particularly useful for the cell culture studies...Comparison of nucleic acid catabolism by normal human fibroblasts and fibroblasts transformed with methylazoxymethyl alcohol ( MAMA ),an activated...catabolite in long-term, pulse-chase experiments. However, the kinetics of catabolism differed, in that only the MAMA -transformed cells had generated

Water and chemical budgets in an urbanized river system under various hydrological conditions

NASA Astrophysics Data System (ADS)

Brion, Natacha; Carbonnel, Vincent; Elskens, Marc; Claeys, Philippe; Verbanck, Michel A.

2017-04-01

Since historical times, riversides are preferential settlement places for human life and activities, ultimately leading to the development of Cities. Available water resources are not only essential to ensure human's vital functions, they are also used for the production of food, goods, and energy, as transport routes and as evacuation ways for domestic and industrial waste products. All these activities profoundly modify natural water circulation as well as water quality, with increased hydrological risks (floods, droughts,…) and chemical hazards (untreated sewage releases, industrial pollution,…) as consequence. An extreme example of strongly modified river system is the river Zenne crossing the city of Brussels. In and around the city, the river together with its connected navigation canal, determine a small vertical urbanized area (800 km2) combining extreme land-use landscapes. While the southern upstream part of this area lies in a region of intensive agricultural activities, the central part is occupied by a dense cityscape including a forested area, and the downstream part is mainly under industrial influence. In this context, we established a box-model representation of water and selected polluting chemicals (N and P, biological oxygen demand, and a selection of metals, pesticides and PAHs) budgets for the studied area under variable hydrological conditions. We first have identified the general distribution of water and pollutant tracers in the various background sources of the system: waters in streams located in the very upstream parts of the catchment, and untreated and treated sewage. Secondly we have assessed the distribution of water flows, and pollutant tracer concentrations at the boundaries of the studied water systems for different stable hydrological conditions and during flood events. Finally we will discuss water budgets and pollution tracer budgets for a yearly average hydrological situation and for dry and wet weather conditions in order to understand hydrological effects on the transport/transfer/retention of water and pollutants in highly human-impacted modified streams. Results from this study were obtained in the framework of the OSIRIS research project (INNOVIRIS Anticipate 2015-2019).

Assembly of Oriented Virus Arrays by Chemo-Selective Ligation Methods and Nanolithography Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Camarero, J A; Cheung, C L; Lin, T

2002-12-02

The present work describes our ongoing efforts towards the creation of nano-scaled ordered arrays of protein/virus covalently attached to site-specific chemical linkers patterned by different nanolithograpy techniques. We will present a new and efficient solid-phase approach for the synthesis of chemically modified long alkyl-thiols. These compounds can be used to introduce chemoselective reacting groups onto gold and silicon-based surfaces. Furthermore, these modified thiols have been used to create nanometric patterns by using different nanolithography techniques. We will show that these patterns can react chemoselectively with proteins and/or virus which have been chemically or recombinantly modified to contain complementary chemical groupsmore » at specific positions thus resulting in the oriented attachment of the protein or virus to the surface.« less

Sensitive And Selective Chemical Sensor With Nanostructured Surfaces.

DOEpatents

Pipino, Andrew C. R.

2003-02-04

A chemical sensor is provided which includes an optical resonator including a nanostructured surface comprising a plurality of nanoparticles bound to one or more surfaces of the resonator. The nanoparticles provide optical absorption and the sensor further comprises a detector for detecting the optical absorption of the nanoparticles or their environment. In particular, a selective chemical interaction is provided which modifies the optical absorption of the nanoparticles or their environment, and an analyte is detected based on the modified optical absorption. A light pulse is generated which enters the resonator to interrogate the modified optical absorption and the exiting light pulse is detected by the detector.

Molecular modification of highly degenerate semiconductor as an active electrode to enhance the performance of supercapacitors

NASA Astrophysics Data System (ADS)

Mundinamani, S. P.; Rabinal, M. K.

2014-12-01

Highly conducting antimony doped tin oxide (SnO2:Sb) films are electrografted with suitable organic molecules to study their electrolytic behavior. A series of organic molecules, such as heptanethiol, dodecanethiol and octadecanethiol are bonded to electrode surfaces. Electrolytic capacitors were formed on both unmodified and chemically modified electrodes using KCl and H2SO4 as electrolytes. This molecular modification significantly enhances the current levels in cyclic voltammograms, and there is a clear shift in oxidation/reduction peaks of these capacitors with scan rate. The results obey Randles-Sevcik relation, which indicates that there is enhancement of ionic diffusion at the electrode-electrolyte interface. There is a large enhancement in the values of specific capacitance (almost by 104 times) after the chemical modification. These measurements show that Faradaic reactions are responsible for charge storage/discharge process in these capacitors. Hence, the molecularly modified electrodes can be a good choice to increase the specific capacitance.

Evaluating Kinase ATP Uptake and Tyrosine Phosphorylation using Multiplexed Quantification of Chemically Labeled and Post-Translationally Modified Peptides

PubMed Central

Fang, Bin; Hoffman, Melissa A.; Mirza, Abu-Sayeef; Mishall, Katie M.; Li, Jiannong; Peterman, Scott M.; Smalley, Keiran S. M.; Shain, Kenneth H.; Weinberger, Paul M.; Wu, Jie; Rix, Uwe; Haura, Eric B.; Koomen, John M.

2015-01-01

Cancer biologists and other healthcare researchers face an increasing challenge in addressing the molecular complexity of disease. Biomarker measurement tools and techniques now contribute to both basic science and translational research. In particular, liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MRM) for multiplexed measurements of protein biomarkers has emerged as a versatile tool for systems biology. Assays can be developed for specific peptides that report on protein expression, mutation, or post-translational modification; discovery proteomics data rapidly translated into multiplexed quantitative approaches. Complementary advances in affinity purification enrich classes of enzymes or peptides representing post-translationally modified or chemically labeled substrates. Here, we illustrate the process for the relative quantification of hundreds of peptides in a single LC-MRM experiment. Desthiobiotinylated peptides produced by activity-based protein profiling (ABPP) using ATP probes and tyrosine-phosphorylated peptides are used as examples. These targeted quantification panels can be applied to further understand the biology of human disease. PMID:25782629

Interface enhancement of glass fiber reinforced vinyl ester composites with flame-synthesized carbon nanotubes and its enhancing mechanism.

PubMed

Liao, Lingmin; Wang, Xiao; Fang, Pengfei; Liew, Kim Meow; Pan, Chunxu

2011-02-01

Interface enhancement with carbon nanotubes (CNTs) provides a promising approach for improving shock strength and toughness of glass fiber reinforced plastic (GFRP) composites. The effects of incorporating flame-synthesized CNTs (F-CNTs) into GFRP were studied, including on hand lay-up preparation, microstructural characterization, mechanical properties, fracture morphologies, and theoretical calculation. The experimental results showed that: (1) the impact strength of the GFRP modified by F-CNTs increased by more than 15% over that of the GFRP modified by CNTs from chemical vapor deposition; and (2) with the F-CNT enhancement, no interfacial debonding was observed at the interface between the fiber and resin matrix on the GFRP fracture surface, which indicated strong adhesive strength between them. The theoretical calculation revealed that the intrinsic characteristics of the F-CNTs, including lower crystallinity with a large number of defects and chemical functional groups on the surface, promoted their surface activity and dispersibility at the interface, which improved the interfacial bond strength of GFRP.

Chemically modified amino porphyrin/TiO2 for the degradation of Acid Black 1 under day light illumination

NASA Astrophysics Data System (ADS)

Krishnakumar, Balu; Balakrishna, Avula; Arranja, Cláudia T.; Dias, Carlos M. F.; Sobral, Abilio J. F. N.

2017-04-01

In this paper, for the first time, chemically modified 5,10,15,20-meso-tetra-(para-amino)-phenyl-porphyrin/TiO2 (TPAPP/TiO2) was prepared and used for the degradation of an azo dye Acid Black 1 (AB 1) under direct sunlight. Initially, TiO2 was prepared by sol-gel method. Before making a TPAPP/TiO2 composite, the surface modification of TiO2 was carried out with glycidoxypropyltrimethoxy silane (GPTMS) which acts as a coupling agent. This is an epoxy terminated silane and could easily bond to the amino group of TPAPP through epoxy cleavage. The formation of TPAPP/TiO2 was confirmed by different characterization techniques such as FT-IR, XRD, SEM and DRS. The photocatalytic activity of TiO2 was highly influenced by TPAPP. A mechanism was proposed for AB 1 degradation by TPAPP/TiO2 under sun light.

Chemically modified amino porphyrin/TiO2 for the degradation of Acid Black 1 under day light illumination.

PubMed

Krishnakumar, Balu; Balakrishna, Avula; Arranja, Cláudia T; Dias, Carlos M F; Sobral, Abilio J F N

2017-04-05

In this paper, for the first time, chemically modified 5,10,15,20-meso-tetra-(para-amino)-phenyl-porphyrin/TiO 2 (TPAPP/TiO 2 ) was prepared and used for the degradation of an azo dye Acid Black 1 (AB 1) under direct sunlight. Initially, TiO 2 was prepared by sol-gel method. Before making a TPAPP/TiO 2 composite, the surface modification of TiO 2 was carried out with glycidoxypropyltrimethoxy silane (GPTMS) which acts as a coupling agent. This is an epoxy terminated silane and could easily bond to the amino group of TPAPP through epoxy cleavage. The formation of TPAPP/TiO 2 was confirmed by different characterization techniques such as FT-IR, XRD, SEM and DRS. The photocatalytic activity of TiO 2 was highly influenced by TPAPP. A mechanism was proposed for AB 1 degradation by TPAPP/TiO 2 under sun light. Copyright © 2017 Elsevier B.V. All rights reserved.

Chemical improvement of chitosan-modified beads for the immobilization of Enterococcus faecium DBFIQ E36 L-arabinose isomerase through multipoint covalent attachment approach.

PubMed

Manzo, Ricardo M; de Sousa, Marylane; Fenoglio, Cecilia L; Gonçalves, Luciana Rocha Barro; Mammarella, Enrique J

2015-10-01

D-tagatose is produced from D-galactose by the enzyme L-arabinose isomerase (L-AI) in a commercially viable bioprocess. An active and stable biocatalyst was obtained by modifying chitosan gel structure through reaction with TNBS, D-fructose or DMF, among others. This led to a significant improvement in L-AI immobilization via multipoint covalent attachment approach. Synthetized derivatives were compared with commercial supports such as Eupergit(®) C250L and glyoxal-agarose. The best chitosan derivative for L-AI immobilization was achieved by reacting 4 % (w/v) D-fructose with 3 % (w/v) chitosan at 50 °C for 4 h. When compared to the free enzyme, the glutaraldehyde-activated chitosan biocatalyst showed an apparent activity of 88.4 U g (gel) (-1) with a 211-fold stabilization factor while the glyoxal-agarose biocatalyst gave an apparent activity of 161.8 U g (gel) (-1) with an 85-fold stabilization factor. Hence, chitosan derivatives were comparable to commercial resins, thus becoming a viable low-cost strategy to obtain high active L-AI insolubilized derivatives.

Photo-switchable microbial fuel-cells.

PubMed

Schlesinger, Orr; Dandela, Rambabu; Bhagat, Ashok; Adepu, Raju; Meijler, Michael M; Xia, Lin; Alfonta, Lital

2018-05-01

Regulation of Bio-systems in a clean, simple, and efficient way is important for the design of smart bio-interfaces and bioelectronic devices. Light as a non-invasive mean to control the activity of a protein enables spatial and temporal control far superior to other chemical and physical methods. The ability to regulate the activity of a catalytic enzyme in a biofuel-cell reduces the waste of resources and energy and turns the fuel-cell into a smart and more efficient device for power generation. Here we present a microbial-fuel-cell based on a surface displayed, photo-switchable alcohol dehydrogenase. The enzyme was modified near the active site using non-canonical amino acids and a small photo-reactive molecule, which enables reversible control of enzymatic activity. Depending on the modification site, the enzyme exhibits reversible behavior upon irradiation with UV and visible light, in both biochemical, and electrochemical assays. The change observed in power output of a microbial fuel cell utilizing the modified enzyme was almost five-fold, between inactive and active states. © 2018 Wiley Periodicals, Inc.

Chemical and Conformational Diversity of Modified Nucleosides Affects tRNA Structure and Function.

PubMed

Väre, Ville Y P; Eruysal, Emily R; Narendran, Amithi; Sarachan, Kathryn L; Agris, Paul F

2017-03-16

RNAs are central to all gene expression through the control of protein synthesis. Four major nucleosides, adenosine, guanosine, cytidine and uridine, compose RNAs and provide sequence variation, but are limited in contributions to structural variation as well as distinct chemical properties. The ability of RNAs to play multiple roles in cellular metabolism is made possible by extensive variation in length, conformational dynamics, and the over 100 post-transcriptional modifications. There are several reviews of the biochemical pathways leading to RNA modification, but the physicochemical nature of modified nucleosides and how they facilitate RNA function is of keen interest, particularly with regard to the contributions of modified nucleosides. Transfer RNAs (tRNAs) are the most extensively modified RNAs. The diversity of modifications provide versatility to the chemical and structural environments. The added chemistry, conformation and dynamics of modified nucleosides occurring at the termini of stems in tRNA's cloverleaf secondary structure affect the global three-dimensional conformation, produce unique recognition determinants for macromolecules to recognize tRNAs, and affect the accurate and efficient decoding ability of tRNAs. This review will discuss the impact of specific chemical moieties on the structure, stability, electrochemical properties, and function of tRNAs.

Genetically Encoded Chemical Probes In Cells Reveal the Binding Path of Urocortin-I to CRF Class B GPCR

PubMed Central

Coin, Irene; Katritch, Vsevolod; Sun, Tingting; Xiang, Zheng; Siu, Fai Yiu; Beyermann, Michael; Stevens, Raymond C.; Wang, Lei

2014-01-01

SUMMARY Molecular determinants regulating the activation of class B G-protein coupled receptors (GPCRs) by native peptide agonists are largely unknown. We have investigated here the interaction between the corticotropin releasing factor receptor type 1 (CRF1R) and its native 40-mer peptide ligand Urocortin-I directly in mammalian cells. By incorporating unnatural amino acid photo-chemical and new click-chemical probes into the receptor, 44 inter-molecular spatial constraints have been derived for the ligand-receptor interaction. The data were analyzed in the context of the recently resolved crystal structure of CRF1R transmembrane domain and existing extracellular domain structures, yielding a complete conformational model for the peptide-receptor complex. Structural features of the receptor-ligand complex yield molecular insights on the mechanism of receptor activation. The experimental strategy provides unique information on full-length post-translationally modified GPCRs in the native membrane of the live cell, complementing in vitro biophysical reductionist approaches. PMID:24290358

40 CFR 721.10029 - Isocyanate compound, modified with methoxysilane (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... to those contained in the corresponding section 5(e) consent order. (ii) Hazard communication program...) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as isocyanate compound, modified with methoxysilane (PMN P-01-918) is subject to reporting under...

40 CFR 721.10150 - Carbon black, (4-methylphenyl)-modified, substituted (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10150 Carbon black, (4-methylphenyl)-modified... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Carbon black, (4-methylphenyl...

40 CFR 721.10149 - Carbon black, (3-methylphenyl)-modified, substituted (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10149 Carbon black, (3-methylphenyl)-modified... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Carbon black, (3-methylphenyl...

Chemical-modification studies of a unique sialic acid-binding lectin from the snail Achatina fulica. Involvement of tryptophan and histidine residues in biological activity.

PubMed Central

Basu, S; Mandal, C; Allen, A K

1988-01-01

A unique sialic acid-binding lectin, achatininH (ATNH) was purified in single step from the haemolymph of the snail Achatina fulica by affinity chromatography on sheep submaxillary-gland mucin coupled to Sepharose 4B. The homogeneity was checked by alkaline gel electrophoresis, immunodiffusion and immunoelectrophoresis. Amino acid analysis showed that the lectin has a fairly high content of acidic amino acid residues (22% of the total). About 1.3% of the residues are half-cystine. The glycoprotein contains 21% carbohydrate. The unusually high content of xylose (6%) and fucose (2.7%) in this snail lectin is quite interesting. The protein was subjected to various chemical modifications in order to detect the amino acid residues and carbohydrate residues present in its binding sites. Modification of tyrosine and arginine residues did not affect the binding activity of ATNH; however, modification of tryptophan and histidine residues led to a complete loss of its biological activity. A marked decrease in the fluorescence emission was found as the tryptophan residues of ATNH were modified. The c.d. data showed the presence of an identical type of conformation in the native and modified agglutinin. The modification of lysine and carboxy residues partially diminished the biological activity. The activity was completely lost after a beta-elimination reaction, indicating that the sugars are O-glycosidically linked to the glycoprotein's protein moiety. This result confirms that the carbohydrate moiety also plays an important role in the agglutination property of this lectin. Images Fig. 3. PMID:3140796

Synthetic CRISPR RNA-Cas9-guided genome editing in human cells.

PubMed

Rahdar, Meghdad; McMahon, Moira A; Prakash, Thazha P; Swayze, Eric E; Bennett, C Frank; Cleveland, Don W

2015-12-22

Genome editing with the clustered, regularly interspaced, short palindromic repeats (CRISPR)-Cas9 nuclease system is a powerful technology for manipulating genomes, including introduction of gene disruptions or corrections. Here we develop a chemically modified, 29-nucleotide synthetic CRISPR RNA (scrRNA), which in combination with unmodified transactivating crRNA (tracrRNA) is shown to functionally replace the natural guide RNA in the CRISPR-Cas9 nuclease system and to mediate efficient genome editing in human cells. Incorporation of rational chemical modifications known to protect against nuclease digestion and stabilize RNA-RNA interactions in the tracrRNA hybridization region of CRISPR RNA (crRNA) yields a scrRNA with enhanced activity compared with the unmodified crRNA and comparable gene disruption activity to the previously published single guide RNA. Taken together, these findings provide a platform for therapeutic applications, especially for nervous system disease, using successive application of cell-permeable, synthetic CRISPR RNAs to activate and then silence Cas9 nuclease activity.

Chemical Composition and Antioxidant Activity of Essential Oils from Cinnamodendron dinisii Schwacke and Siparuna guianensis Aublet

PubMed Central

Andrade, Milene Aparecida; Cardoso, Maria das Graças; de Andrade, Juliana; Silva, Lucilene Fernandes; Teixeira, Maria Luisa; Resende, Juliana Maria Valério; Figueiredo, Ana Cristina da Silva; Barroso, José Gonçalves

2013-01-01

The objectives of this study were to chemically characterize and evaluate the antioxidant activity of essential oils Cinnamodendron dinisii Schwacke (pepper) and Siparuna guianensis Aublet (negramina). The essential oil was isolated by hydrodistillation using a Clevenger modified apparatus, and the identification and quantification of constituents, through GC/MS and GC-FID analysis. The antioxidant activity was evaluated using β-carotene/linoleic acid system and the DPPH radical sequestering method. In chromatographic analysis, the majority constituents found in the essential oil of C. dinisii were bicyclic monoterpenes, α-pinene (35.41%), β-pinene (17.81%), sabinene (12.01%) and sesquiterpene bicyclogermacrene (7.59%). In the essential oil of the fresh leaves of Siparuna guianensis Aublet, acyclic monoterpene, β-myrcene (13.14%), and sesquiterpenes, germacrene-D (8.68%) and bicyclogermacrene (16.71%) were identified. The antioxidant activity was low by the β-carotene/linoleic acid test and was not evidenced by the DPPH test, for both oils evaluated. PMID:26784471

A Rapid Method for Measuring Strontium-90 Activity in Crops in China

NASA Astrophysics Data System (ADS)

Pan, Lingjing Pan; Yu, Guobing; Wen, Deyun; Chen, Zhi; Sheng, Liusi; Liu, Chung-King; Xu, X. George

2017-09-01

A rapid method for measuring Sr-90 activity in crop ashes is presented. Liquid scintillation counting, combined with ion exchange columns 4`, 4"(5")-di-t-butylcyclohexane-18-crown-6, is used to determine the activity of Sr-90 in crops. The yields of chemical procedure are quantified using gravimetric analysis. The conventional method that uses ion-exchange resin with HDEHP could not completely remove all the bismuth when comparatively large lead and bismuth exist in the samples. This is overcome by the rapid method. The chemical yield of this method is about 60% and the MDA for Sr-90 is found to be 2:32 Bq/kg. The whole procedure together with using spectrum analysis to determine the activity only takes about one day, which is really a large improvement compared with the conventional method. A modified conventional method is also described here to verify the value of the rapid one. These two methods can meet di_erent needs of daily monitoring and emergency situation.

Dynamic high-pressure microfluidization assisting octenyl succinic anhydride modification of rice starch.

PubMed

Li, Yu-Ting; Wang, Ri-Si; Liang, Rui-Hong; Chen, Jun; He, Xiao-Hong; Chen, Rui-Yun; Liu, Wei; Liu, Cheng-Mei

2018-08-01

Octenyl succinic anhydride (OSA) modified starch is widely used in food industries. In this study, rice starch (RS) was pretreated by dynamic high-pressure microfluidization (DHPM) and subsequently modified by OSA. The influence of DHPM on OSA modification of rice starch was investigated. Results showed that DHPM pretreatment enhanced the degree of substitution by changing the morphology and crystallinity of rice starch. Compared with the rice starch modified by OSA without DHPM pretreatment (OSA-RS), the DHPM-pretreated OSA starch (DHPM-OSA-RS) presented higher peak viscosity and lower pasting temperature. DHPM-OSA-RS also exhibited better emulsifying activity and emulsion stability. This study suggested that DHPM will provide an opportunity to change the physicochemical properties of starch, with the resulting starch being more suitable for chemical modification. Copyright © 2018 Elsevier Ltd. All rights reserved.

Pupicidal and repellent activities of Pogostemon cablin essential oil chemical compounds against medically important human vector mosquitoes

PubMed Central

Gokulakrishnan, J; Kuppusamy, Elumalai; Shanmugam, Dhanasekaran; Appavu, Anandan; Kaliyamoorthi, Krishnappa

2013-01-01

Objective To determine the repellent and pupicidal activities of Pogostemon cablin (P. cablin) chemical compositions were assayed for their toxicity against selected important vector mosquitoes, viz., Aedes aegypti (Ae. aegypti), Anopheles stephensi (An. stephensi) and Culex quinquefasciatus (Cx. quinquefasciatus) (Diptera: Culicidae). Methods The plants dry aerial parts were subjected to hydrodistillation using a modified Clevenger-type apparatus. The composition of the essential oil was analyzed by Gas Chromatography (GC) and GC mass spectrophotometry. Evaluation was carried out in a net cage (45 cm×30 cm×45 cm) containing 100 blood starved female mosquitoes and were assayed in the laboratory condition by using the protocol of WHO 2010. The repellent activity of P. cablin chemical compositions at concentration of 2mg/cm2were applied on skin of fore arm in man and exposed against adult female mosquitoes. The pupicidal activity was determined against selected important vector mosquitoes to concentration of 100 mg/L and mortality of each pupa was recorded after 24 h of exposure to the compounds. Results Chemical constituents of 15 compounds were identified in the oil of P.cablin compounds representing to 98.96%. The major components in essential oil were â-patchoulene, á-guaiene, ã-patchoulene, á-bulnesene and patchouli alcohol. The repellent activity of patchouli alcohol compound was found to be most effective for repellent activity and 2 mg/cm2 concentration provided 100% protection up to 280 min against Ae. aegypti, An. stephensi and Cx. quinquefasciatus, respectively. Similarly, pupae exposed to 100 mg/L concentrations of P. cablin chemical compositions. Among five compounds tested patchouli alcoholwas found to be most effective for pupicidal activity provided 28.44, 26.28 and 25.36 against Ae.aegypti, An.stephensi and Cx. quinquefasciatus, respectively. The percent adult emergence was inversely proportional to the concentration of compounds and directly proportional to the pupal mortality. Conclusion These results suggest that the P. cablin chemical compositions have the potential to be used as an ideal eco-friendly approach for the control of mosquitoes. This is the first report on the mosquito repellent and pupicidal activities of the reported P. cablin chemical compositions.

Effect of the pH in the adsorption and in the immersion enthalpy of monohydroxylated phenols from aqueous solutions on activated carbons.

PubMed

Blanco-Martínez, D A; Giraldo, L; Moreno-Piraján, J C

2009-09-30

An activated carbon Carbochem--PS230 was modified by chemical and thermal treatment in flow of H(2) in order to evaluate the influence of the activated carbon chemical surface in the adsorption of the monohydroxylated phenols. The solid-solution interaction was determined by analyzing the adsorption isotherms at 298 K at pH 7, 9 and 11 during 48 h. The adsorption capacity of activated carbons increases when the pH solution decreases. The amount adsorbed increases in the reduced carbon at the maximum adsorption pH and decreases in the oxidized carbon. In the sample of granulated activated carbon, CAG, the monohydroxylated phenols adsorption capacity diminishes in the following order catechol >hydroquinone >resorcinol, at the three pH values. The experimental data are evaluated with Freundlich's and Langmuir's models. The immersion enthalpies are determined and increase with the retained amount, ranging between 21.5 and 45.7 J g(-1). In addition, the immersion enthalpies show more interaction with the reduced activated carbon that has lower total acidity contents.

Structure-based design of novel chemical modification of the 3'-overhang for optimization of short interfering RNA performance.

PubMed

Xu, Lexing; Wang, Xin; He, Hongwei; Zhou, Jinming; Li, Xiaoyu; Ma, Hongtao; Li, Zelin; Zeng, Yi; Shao, Rongguang; Cen, Shan; Wang, Yucheng

2015-02-10

Short interfering RNAs (siRNAs) are broadly used to manipulate gene expression in mammalian cells. Although chemical modification is useful for increasing the potency of siRNAs in vivo, rational optimization of siRNA performance through chemical modification is still a challenge. In this work, we designed and synthesized a set of siRNAs containing modified two-nucleotide 3'-overhangs with the aim of strengthening the interaction between the 3'-end of the siRNA strand and the PAZ domain of Ago2. Their efficiency of binding to the PAZ domain was calculated using a computer modeling program, followed by measurement of RNA-Ago2 interaction in a surface plasmon resonance biochemical assay. The results suggest that increasing the level of binding of the 3'-end of the guiding strand with the PAZ domain, and/or reducing the level of binding of the sense strand through modifying the two-nucleotide 3'-overhangs, affects preferential strand selection and improves siRNA activity, while we cannot exclude the possibility that the modifications at the 3'-end of the sense strand may also affect the recognition of the 5'-end of the guiding strand by the MID domain. Taken together, our work presents a strategy for optimizing siRNA performance through asymmetric chemical modification of 3'-overhangs and also helps to develop the computer modeling method for rational siRNA design.

Peroxide-modified titanium dioxide: a chemical analog of putative Martian soil oxidants

NASA Technical Reports Server (NTRS)

Quinn, R. C.; Zent, A. P.

1999-01-01

Hydrogen peroxide chemisorbed on titanium dioxide (peroxide-modified titanium dioxide) is investigated as a chemical analog to the putative soil oxidants responsible for the chemical reactivity seen in the Viking biology experiments. When peroxide-modified titanium dioxide (anatase) was exposed to a solution similar to the Viking labeled release (LR) experiment organic medium, CO2 gas was released into the sample cell headspace. Storage of these samples at 10 degrees C for 48 hr prior to exposure to organics resulted in a positive response while storage for 7 days did not. In the Viking LR experiment, storage of the Martian surface samples for 2 sols (approximately 49 hr) resulted in a positive response while storage for 141 sols essentially eliminated the initial rapid release of CO2. Heating the peroxide-modified titanium dioxide to 50 degrees C prior to exposure to organics resulted in a negative response. This is similar to, but not identical to, the Viking samples where heating to approximately 46 degrees C diminished the response by 54-80% and heating to 51.5 apparently eliminated the response. When exposed to water vapor, the peroxide-modified titanium dioxide samples release O2 in a manner similar to the release seen in the Viking gas exchange experiment (GEx). Reactivity is retained upon heating at 50 degrees C for three hours, distinguishing this active agent from the one responsible for the release of CO2 from aqueous organics. The release of CO2 by the peroxide-modified titanium dioxide is attributed to the decomposition of organics by outer-sphere peroxide complexes associated with surface hydroxyl groups, while the release of O2 upon humidification is attributed to more stable inner-sphere peroxide complexes associated with Ti4+ cations. Heating the peroxide-modified titanium dioxide to 145 degrees C inhibited the release of O2, while in the Viking experiments heating to this temperature diminished but did not eliminated the response. Although the thermal stability of the titanium-peroxide complexes in this work is lower than the stability seen in the Viking experiments, it is expected that similar types of complexes will form in titanium containing minerals other than anatase and the stability of these complexes will vary with surface hydroxylation and mineralogy.

40 CFR 721.10149 - Carbon black, (3-methylphenyl)-modified, substituted (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Carbon black, (3-methylphenyl)-modified, substituted (generic). 721.10149 Section 721.10149 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substance...

40 CFR 721.10149 - Carbon black, (3-methylphenyl)-modified, substituted (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Carbon black, (3-methylphenyl)-modified, substituted (generic). 721.10149 Section 721.10149 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substance...

40 CFR 721.10150 - Carbon black, (4-methylphenyl)-modified, substituted (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Carbon black, (4-methylphenyl)-modified, substituted (generic). 721.10150 Section 721.10150 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substance...

40 CFR 721.10150 - Carbon black, (4-methylphenyl)-modified, substituted (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Carbon black, (4-methylphenyl)-modified, substituted (generic). 721.10150 Section 721.10150 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substance...

40 CFR 721.9514 - Ethyl silicate, reaction products with modified alkoxysilane salt (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Ethyl silicate, reaction products with... Significant New Uses for Specific Chemical Substances § 721.9514 Ethyl silicate, reaction products with.... (1) The chemical substance identified generically as Ethyl silicate, reaction products with modified...

40 CFR 721.9514 - Ethyl silicate, reaction products with modified alkoxysilane salt (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Ethyl silicate, reaction products with... Significant New Uses for Specific Chemical Substances § 721.9514 Ethyl silicate, reaction products with.... (1) The chemical substance identified generically as Ethyl silicate, reaction products with modified...

21 CFR 178.3790 - Polymer modifiers in semirigid and rigid vinyl chloride plastics.

Code of Federal Regulations, 2012 CFR

2012-04-01

... chemical reactions, other than addition reactions, occur when they are mixed. (2) Polymers identified in...; provided that no chemical reactions, other than addition reactions, occur when they are combined. Such..., other than addition reactions, occur among the vinyl chloride polymers and the modifying polymers...

21 CFR 178.3790 - Polymer modifiers in semirigid and rigid vinyl chloride plastics.

Code of Federal Regulations, 2013 CFR

2013-04-01

... chemical reactions, other than addition reactions, occur when they are mixed. (2) Polymers identified in...; provided that no chemical reactions, other than addition reactions, occur when they are combined. Such..., other than addition reactions, occur among the vinyl chloride polymers and the modifying polymers...

Chemical Control over T-Cell Activation in Vivo Using Deprotection of trans-Cyclooctene-Modified Epitopes.

PubMed

van der Gracht, Anouk M F; de Geus, Mark A R; Camps, Marcel G M; Ruckwardt, Tracy J; Sarris, Alexi J C; Bremmers, Jessica; Maurits, Elmer; Pawlak, Joanna B; Posthoorn, Michelle M; Bonger, Kimberly M; Filippov, Dmitri V; Overkleeft, Herman S; Robillard, Marc S; Ossendorp, Ferry; van Kasteren, Sander I

2018-06-15

Activation of a cytotoxic T-cell is a complex multistep process, and tools to study the molecular events and their dynamics that result in T-cell activation in situ and in vivo are scarce. Here, we report the design and use of conditional epitopes for time-controlled T-cell activation in vivo. We show that trans-cyclooctene-protected SIINFEKL (with the lysine amine masked) is unable to elicit the T-cell response characteristic for the free SIINFEKL epitope. Epitope uncaging by means of an inverse-electron demand Diels-Alder (IEDDA) event restored T-cell activation and provided temporal control of T-cell proliferation in vivo.

Evaluating Zeolite-Modified Sensors: towards a faster set of chemical sensors

NASA Astrophysics Data System (ADS)

Berna, A. Z.; Vergara, A.; Trincavelli, M.; Huerta, R.; Afonja, A.; Parkin, I. P.; Binions, R.; Trowell, S.

2011-09-01

The responses of zeolite-modified sensors, prepared by screen printing layers of chromium titanium oxide (CTO), were compared to unmodified tin oxide sensors using amplitude and transient responses. For transient responses we used a family of features, derived from the exponential moving average (EMA), to characterize chemo-resistive responses. All sensors were tested simultaneously against 20 individual volatile compounds from four chemical groups. The responses of the two types of sensors showed some independence. The zeolite-modified CTO sensors discriminated compounds better using either amplitude response or EMA features and CTO-modified sensors also responded three times faster.

Enzyme immobilization techniques on poly(glycidyl methacrylate-co-ethylene dimethacrylate) carrier with penicillin amidase as model.

PubMed

Drobník, J; Saudek, V; Svec, F; Kálal, J; Vojtísek, V; Bárta, M

1979-08-01

Two types of bead-form macroporous carriers based on glycidyl methacrylate with ethylene dimethacrylate copolymers were used for the immobilization of penicillin amidase either directly or after chemical modification. Direct binding through oxirane groups, which is equally efficient at pH 4.2 and 7, is relatively slow and brings about an activity loss at low enzyme concentrations. The most efficient immobilization was achieved on glutaraldehyde-activated amino carrier, irrespective of whether the amino groups were formed by ammonia or 1,6-diaminohexane treatment of the original oxirane carrier. Hydrazine treatment gave lower immobilization yields. The same is true of the azide method independent of the length of the spacer. Most enzyme activity was preserved by coupling the carbodiimide-activated enzyme to the carrier with alkyl or arylamino groups at the end of a longer substituent. Immobilization on diazo-modified carrier gave average results. Rapid immobilization by a lysine-modified phosgene-treated carrier resulted in an activity loss. It is suggested that multipoint and very tight attachment of the enzyme molecule to the matrix decreased the activity. The immobilized activity is quite stable in solution and very stable upon lyophilization with sucrose.

Chemical modification of poly(ethylene terephthalate) and immobilization of the selected enzymes on the modified film

NASA Astrophysics Data System (ADS)

Irena, Gancarz; Jolanta, Bryjak; Karolina, Zynek

2009-07-01

Poly(ethylene terephthalate) (PET) film was modified by reaction with hydrazine (HD), ethylenediamine (EDA), 1,2-diaminopropane (1,2-DAP) and 1,3-diaminopropane (1,3-DAP). The maximal amount of amine functionalities introduced in the chosen conditions on the surface was found as 0.07, 3.35, 0.76 and 1.99 nmol cm -2 for HD, EDA, 1,2-DAP and 1,3-DAP respectively. During the modification process etching of the sample and an increase of stiffness takes place. FTIR-ATR spectra prove that the surface chemistry after modification in amine solution is very complex. The lack of clear correlation between the surface tension and surface concentration of amine functionalities seems to confirm that. For immobilization purpose invertase, laccase and tyrosinase were used. The amount of covalently attached proteins at first increases with the increase of surface concentration of amine groups but after reaching a certain level of amine groups, decrease of the immobilization level was observed. All enzymes tested showed highest activity for a moderate level of aminolysis and this activity had the highest values for EDA-modified PET.

Improved antifouling properties and selective biofunctionalization of stainless steel by employing heterobifunctional silane-polyethylene glycol overlayers and avidin-biotin technology

PubMed Central

Hynninen, Ville; Vuori, Leena; Hannula, Markku; Tapio, Kosti; Lahtonen, Kimmo; Isoniemi, Tommi; Lehtonen, Elina; Hirsimäki, Mika; Toppari, J. Jussi; Valden, Mika; Hytönen, Vesa P.

2016-01-01

A straightforward solution-based method to modify the biofunctionality of stainless steel (SS) using heterobifunctional silane-polyethylene glycol (silane-PEG) overlayers is reported. Reduced nonspecific biofouling of both proteins and bacteria onto SS and further selective biofunctionalization of the modified surface were achieved. According to photoelectron spectroscopy analyses, the silane-PEGs formed less than 10 Å thick overlayers with close to 90% surface coverage and reproducible chemical compositions. Consequently, the surfaces also became more hydrophilic, and the observed non-specific biofouling of proteins was reduced by approximately 70%. In addition, the attachment of E. coli was reduced by more than 65%. Moreover, the potential of the overlayer to be further modified was demonstrated by successfully coupling biotinylated alkaline phosphatase (bAP) to a silane-PEG-biotin overlayer via avidin-biotin bridges. The activity of the immobilized enzyme was shown to be well preserved without compromising the achieved antifouling properties. Overall, the simple solution-based approach enables the tailoring of SS to enhance its activity for biomedical and biotechnological applications. PMID:27381834

Improved antifouling properties and selective biofunctionalization of stainless steel by employing heterobifunctional silane-polyethylene glycol overlayers and avidin-biotin technology

NASA Astrophysics Data System (ADS)

Hynninen, Ville; Vuori, Leena; Hannula, Markku; Tapio, Kosti; Lahtonen, Kimmo; Isoniemi, Tommi; Lehtonen, Elina; Hirsimäki, Mika; Toppari, J. Jussi; Valden, Mika; Hytönen, Vesa P.

2016-07-01

A straightforward solution-based method to modify the biofunctionality of stainless steel (SS) using heterobifunctional silane-polyethylene glycol (silane-PEG) overlayers is reported. Reduced nonspecific biofouling of both proteins and bacteria onto SS and further selective biofunctionalization of the modified surface were achieved. According to photoelectron spectroscopy analyses, the silane-PEGs formed less than 10 Å thick overlayers with close to 90% surface coverage and reproducible chemical compositions. Consequently, the surfaces also became more hydrophilic, and the observed non-specific biofouling of proteins was reduced by approximately 70%. In addition, the attachment of E. coli was reduced by more than 65%. Moreover, the potential of the overlayer to be further modified was demonstrated by successfully coupling biotinylated alkaline phosphatase (bAP) to a silane-PEG-biotin overlayer via avidin-biotin bridges. The activity of the immobilized enzyme was shown to be well preserved without compromising the achieved antifouling properties. Overall, the simple solution-based approach enables the tailoring of SS to enhance its activity for biomedical and biotechnological applications.

Treatment of swine wastewater using chemically modified zeolite and bioflocculant from activated sludge.

PubMed

Guo, Junyuan; Yang, Chunping; Zeng, Guangming

2013-09-01

Sterilization, alkaline-thermal and acid-thermal treatments were applied to activated sludge and the pre-treated sludge was used as raw material for Rhodococcus R3 to produce polymeric substances. After 60 h of fermentation, bioflocculant of 2.7 and 4.2 g L(-1) were produced in sterilized and alkaline-thermal treated sludge as compared to that of 0.9 g L(-1) in acid-thermal treated sludge. Response surface methodology (RSM) was employed to optimize the treatment process of swine wastewater using the composite of bioflocculant and zeolite modified by calcining with MgO. The optimal flocculating conditions were bioflocculant of 24 mg L(-1), modified zeolite of 12 g L(-1), CaCl2 of 16 mg L(-1), pH of 8.3 and contact time of 55 min, and the corresponding removal rates of COD, ammonium and turbidity were 87.9%, 86.9%, and 94.8%. The use of the composite by RSM provides a feasible way to improve the pollutant removal efficiencies and recycle high-level of ammonium from wastewater. Copyright © 2013 Elsevier Ltd. All rights reserved.

Removal of sulfur compounds from petroleum refinery wastewater through adsorption on modified activated carbon.

PubMed

Ben Hariz, Ichrak; Al Ayni, Foued; Monser, Lotfi

2014-01-01

The adsorption of sulfur compounds from petroleum refinery wastewater on a chemically modified activated carbon (MAC) was investigated. The modification technique (nitric acid, hydrogen peroxide and thermal modification) enhanced the removal capacity of carbon and therefore decreases cost-effective removal of sulfide from refinery wastewater. Adsorption equilibrium and kinetics data were determined for sulfur removal from real refinery wastewater. The data were evaluated according to several adsorption isotherm and kinetics models. The Freundlich isotherm fitted well with the equilibrium data of sulfur on different adsorbents, whereas the kinetics data were best fitted by the pseudo-second-order model. Insights of sulfide removal mechanisms indicated that the sorption was controlled through the intraparticle diffusion mechanism with a significant contribution of film diffusion. The MAC adsorbent was found to have an effective removal capacity of approximately 2.5 times that of non-modified carbon. Using different MAC, sulfides were eliminated with a removal capacity of 52 mg g(-1). Therefore, MAC can be utilized as an effective and less expensive adsorbent for the reduction of sulfur in refinery wastewater.

Profiling the immunotoxicity of chemicals based on in vitro evaluation by a combination of the Multi-ImmunoTox assay and the IL-8 Luc assay.

PubMed

Kimura, Yutaka; Fujimura, Chizu; Ito, Yumiko; Takahashi, Toshiya; Terui, Hitoshi; Aiba, Setsuya

2018-06-01

We established a luciferase reporter assay system, the Multi-ImmunoTox Assay (MITA), which can evaluate the effects of chemicals on the promoter activities of four cytokines: IL-2, IFN-γ, IL-1β, and IL-8. We previously reported that MITA correctly reflected the change in mRNA of human whole-blood cells treated with dexamethasone, cyclosporine, FK506, or several other immunosuppressive drugs. In this study, we combined MITA with the IL-8 Luc assay to detect skin sensitization chemicals (OECD 442E) (modified MITA: mMITA) and established a data set of 60 chemicals examined by mMITA. Using the mMITA results, chemicals can be classified based on the lowest observed effect level (LOEL) of chemicals in suppressing or augmenting the promoter activities of the four cytokines. Moreover, we demonstrated that K-means clustering and hierarchical clustering of the 60 chemicals based on the LOEL for their effects on IL-2 and IL-8 promoter activities and the judgment by the IL-8 Luc assay resulted in the same 6-cluster solution: cluster 1 with preferential suppression of IL-8, cluster 2 with suppression of IL-2 and a positive IL-8 Luc assay result, cluster 3 with suppression of both IL-2 and IL-8, cluster 4 with no effects on IL-2 or IL-8 and a negative IL-8 Luc assay result, cluster 5 with suppression of both IL-2 and IL-8 and a negative IL-8 Luc assay result, and cluster 6 with preferential suppression of IL-8. These data suggest that mMITA is a promising novel high-throughput approach for detecting unrecognized immunological effects of chemicals and for profiling their immunotoxic effects.

Development of a novel electric field-assisted modified hydrodynamic cavitation system for disintegration of waste activated sludge.

PubMed

Jung, Kyung-Won; Hwang, Min-Jin; Yun, Yeo-Myeong; Cha, Min-Jung; Ahn, Kyu-Hong

2014-09-01

In this current study, we present a modified hydrodynamic cavitation device that combines an electric field to substitute for the chemical addition. A modified HC system is basically an orifice plate and crisscross pipe assembly, in which the crisscross pipe imparts some turbulence, which creates collision events. This study shows that for maximizing disintegration, combining HC system, which called electric field-assisted modified orifice plate hydrodynamic cavitation (EFM-HC) in this study, with an electric field is important. Various HC systems were compared in terms of disintegration of WAS, and, among them, the EFM-HC system exhibited the best performance with the highest disintegration efficiency of 47.0±2.0% as well as the destruction of WAS morphological characteristics. The experimental results clearly show that a conventional HC system was successfully modified. In addition, electric field has a great potential for efficient disintegration of WAS for as a additional option in a combination treatment. This study suggests continued research in this field may lead to an appropriate design for commercial use. Copyright © 2014 Elsevier B.V. All rights reserved.

Highly exposed {001} facets of titanium dioxide modified with reduced graphene oxide for dopamine sensing.

PubMed

How, Gregory Thien Soon; Pandikumar, Alagarsamy; Ming, Huang Nay; Ngee, Lim Hong

2014-05-23

Titanium dioxide (TiO2) with highly exposed {001} facets was synthesized through a facile solvo-thermal method and its surface was decorated by using reduced graphene oxide (rGO) sheets. The morphology and chemical composition of the prepared rGO/TiO2 {001} nanocomposite were examined by using suitable characterization techniques. The rGO/TiO2 {001} nanocomposite was used to modify glassy carbon electrode (GCE), which showed higher electrocatalytic activity towards the oxidation of dopamine (DA) and ascorbic acid (AA), when compared to unmodified GCE. The differential pulse voltammetric studies revealed good sensitivity and selectivity nature of the rGO/TiO2 {001} nanocomposite modified GCE for the detection of DA in the presence of AA. The modified GCE exhibited a low electrochemical detection limit of 6 μM over the linear range of 2-60 μM. Overall, this work provides a simple platform for the development of GCE modified with rGO/TiO2 {001} nanocomposite with highly exposed {001} facets for potential electrochemical sensing applications.

Highly exposed {001} facets of titanium dioxide modified with reduced graphene oxide for dopamine sensing

NASA Astrophysics Data System (ADS)

How, Gregory Thien Soon; Pandikumar, Alagarsamy; Ming, Huang Nay; Ngee, Lim Hong

2014-05-01

Titanium dioxide (TiO2) with highly exposed {001} facets was synthesized through a facile solvo-thermal method and its surface was decorated by using reduced graphene oxide (rGO) sheets. The morphology and chemical composition of the prepared rGO/TiO2 {001} nanocomposite were examined by using suitable characterization techniques. The rGO/TiO2 {001} nanocomposite was used to modify glassy carbon electrode (GCE), which showed higher electrocatalytic activity towards the oxidation of dopamine (DA) and ascorbic acid (AA), when compared to unmodified GCE. The differential pulse voltammetric studies revealed good sensitivity and selectivity nature of the rGO/TiO2 {001} nanocomposite modified GCE for the detection of DA in the presence of AA. The modified GCE exhibited a low electrochemical detection limit of 6 μM over the linear range of 2-60 μM. Overall, this work provides a simple platform for the development of GCE modified with rGO/TiO2 {001} nanocomposite with highly exposed {001} facets for potential electrochemical sensing applications.

Highly exposed {001} facets of titanium dioxide modified with reduced graphene oxide for dopamine sensing

PubMed Central

How, Gregory Thien Soon; Pandikumar, Alagarsamy; Ming, Huang Nay; Ngee, Lim Hong

2014-01-01

Titanium dioxide (TiO2) with highly exposed {001} facets was synthesized through a facile solvo-thermal method and its surface was decorated by using reduced graphene oxide (rGO) sheets. The morphology and chemical composition of the prepared rGO/TiO2 {001} nanocomposite were examined by using suitable characterization techniques. The rGO/TiO2 {001} nanocomposite was used to modify glassy carbon electrode (GCE), which showed higher electrocatalytic activity towards the oxidation of dopamine (DA) and ascorbic acid (AA), when compared to unmodified GCE. The differential pulse voltammetric studies revealed good sensitivity and selectivity nature of the rGO/TiO2 {001} nanocomposite modified GCE for the detection of DA in the presence of AA. The modified GCE exhibited a low electrochemical detection limit of 6 μM over the linear range of 2–60 μM. Overall, this work provides a simple platform for the development of GCE modified with rGO/TiO2 {001} nanocomposite with highly exposed {001} facets for potential electrochemical sensing applications. PMID:24853929

Piezoelectric sensor for sensitive determination of metal ions based on the phosphate-modified dendrimer

NASA Astrophysics Data System (ADS)

Wang, S. H.; Shen, C. Y.; Lin, Y. M.; Du, J. C.

2016-08-01

Heavy metal ions arising from human activities are retained strongly in water; therefore public water supplies must be monitored regularly to ensure the timely detection of potential problems. A phosphate-modified dendrimer film was investigated on a quartz crystal microbalance (QCM) for sensing metal ions in water at room temperature in this study. The chemical structures and sensing properties were characterized by Fourier transform infrared spectroscopy and QCM measurement, respectively. This phosphate-modified dendrimer sensor can directly detect metal ions in aqueous solutions. This novel sensor was evaluated for its capacity to sense various metal ions. The sensor exhibited a higher sensitivity level and shorter response time to copper(II) ions than other sensors. The linear detection range of the prepared QCM based on the phosphate-modified dendrimer was 0.0001 ∼ 1 μM Cu(II) ions (R2 = 0.98). The detection properties, including sensitivity, response time, selectivity, reusability, maximum adsorption capacity, and adsorption equilibrium constants, were also investigated.

Antibiotic Algae by Chemical Surface Engineering.

PubMed

Kerschgens, Isabel P; Gademann, Karl

2018-03-02

Chemical cell-surface engineering is a tool for modifying and altering cellular functions. Herein, we report the introduction of an antibiotic phenotype to the green alga Chlamydomonas reinhardtii by chemically modifying its cell surface. Flow cytometry and confocal microscopy studies demonstrated that a hybrid of the antibiotic vancomycin and a 4-hydroxyproline oligomer binds reversibly to the cell wall without affecting the viability or motility of the cells. The modified cells were used to inhibit bacterial growth of Gram-positive Bacillus subtilis cultures. Delivery of the antibiotic from the microalgae to the bacterial cells was verified by microscopy. Our studies provide compelling evidence that 1) chemical surface engineering constitutes a useful tool for the introduction of new, previously unknown functionality, and 2) living microalgae can serve as new platforms for drug delivery. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Minimal 2'-O-methyl phosphorothioate linkage modification pattern of synthetic guide RNAs for increased stability and efficient CRISPR-Cas9 gene editing avoiding cellular toxicity

PubMed Central

Basila, Megan; Kelley, Melissa L.

2017-01-01

Since its initial application in mammalian cells, CRISPR-Cas9 has rapidly become a preferred method for genome engineering experiments. The Cas9 nuclease is targeted to genomic DNA using guide RNAs (gRNA), either as the native dual RNA system consisting of a DNA-targeting CRISPR RNA (crRNA) and a trans-activating crRNA (tracrRNA), or as a chimeric single guide RNA (sgRNA). Entirely DNA-free CRISPR-Cas9 systems using either Cas9 protein or Cas9 mRNA and chemically synthesized gRNAs allow for transient expression of CRISPR-Cas9 components, thereby reducing the potential for off-targeting, which is a significant advantage in therapeutic applications. In addition, the use of synthetic gRNA allows for the incorporation of chemical modifications for enhanced properties including improved stability. Previous studies have demonstrated the utility of chemically modified gRNAs, but have focused on one pattern with multiple modifications in co-electroporation with Cas9 mRNA or multiple modifications and patterns with Cas9 plasmid lipid co-transfections. Here we present gene editing results using a series of chemically modified synthetic sgRNA molecules and chemically modified crRNA:tracrRNA molecules in both electroporation and lipid transfection assessing indel formation and/or phenotypic gene knockout. We show that while modifications are required for co-electroporation with Cas9 mRNA, some modification patterns of the gRNA are toxic to cells compared to the unmodified gRNA and most modification patterns do not significantly improve gene editing efficiency. We also present modification patterns of the gRNA that can modestly improve Cas9 gene editing efficiency when co-transfected with Cas9 mRNA or Cas9 protein (> 1.5-fold difference). These results indicate that for certain applications, including those relevant to primary cells, the incorporation of some, but not all chemical modification patterns on synthetic crRNA:tracrRNA or sgRNA can be beneficial to CRISPR-Cas9 gene editing. PMID:29176845

Minimal 2'-O-methyl phosphorothioate linkage modification pattern of synthetic guide RNAs for increased stability and efficient CRISPR-Cas9 gene editing avoiding cellular toxicity.

PubMed

Basila, Megan; Kelley, Melissa L; Smith, Anja van Brabant

2017-01-01

Since its initial application in mammalian cells, CRISPR-Cas9 has rapidly become a preferred method for genome engineering experiments. The Cas9 nuclease is targeted to genomic DNA using guide RNAs (gRNA), either as the native dual RNA system consisting of a DNA-targeting CRISPR RNA (crRNA) and a trans-activating crRNA (tracrRNA), or as a chimeric single guide RNA (sgRNA). Entirely DNA-free CRISPR-Cas9 systems using either Cas9 protein or Cas9 mRNA and chemically synthesized gRNAs allow for transient expression of CRISPR-Cas9 components, thereby reducing the potential for off-targeting, which is a significant advantage in therapeutic applications. In addition, the use of synthetic gRNA allows for the incorporation of chemical modifications for enhanced properties including improved stability. Previous studies have demonstrated the utility of chemically modified gRNAs, but have focused on one pattern with multiple modifications in co-electroporation with Cas9 mRNA or multiple modifications and patterns with Cas9 plasmid lipid co-transfections. Here we present gene editing results using a series of chemically modified synthetic sgRNA molecules and chemically modified crRNA:tracrRNA molecules in both electroporation and lipid transfection assessing indel formation and/or phenotypic gene knockout. We show that while modifications are required for co-electroporation with Cas9 mRNA, some modification patterns of the gRNA are toxic to cells compared to the unmodified gRNA and most modification patterns do not significantly improve gene editing efficiency. We also present modification patterns of the gRNA that can modestly improve Cas9 gene editing efficiency when co-transfected with Cas9 mRNA or Cas9 protein (> 1.5-fold difference). These results indicate that for certain applications, including those relevant to primary cells, the incorporation of some, but not all chemical modification patterns on synthetic crRNA:tracrRNA or sgRNA can be beneficial to CRISPR-Cas9 gene editing.

A Synthetic DNA-Binding Domain Guides Distinct Chromatin-Modifying Small Molecules to Activate an Identical Gene Network.

PubMed

Han, Le; Pandian, Ganesh N; Chandran, Anandhakumar; Sato, Shinsuke; Taniguchi, Junichi; Kashiwazaki, Gengo; Sawatani, Yoshito; Hashiya, Kaori; Bando, Toshikazu; Xu, Yufang; Qian, Xuhong; Sugiyama, Hiroshi

2015-07-20

Synthetic dual-function ligands targeting specific DNA sequences and histone-modifying enzymes were applied to achieve regulatory control over multi-gene networks in living cells. Unlike the broad array of targeting small molecules for histone deacetylases (HDACs), few modulators are known for histone acetyltransferases (HATs), which play a central role in transcriptional control. As a novel chemical approach to induce selective HAT-regulated genes, we conjugated a DNA-binding domain (DBD) "I" to N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-benzamide (CTB), an artificial HAT activator. In vitro enzyme activity assays and microarray studies were used to demonstrate that distinct functional small molecules could be transformed to have identical bioactivity when conjugated with a targeting DBD. This proof-of-concept synthetic strategy validates the switchable functions of HDACs and HATs in gene regulation and provides a molecular basis for developing versatile bioactive ligands. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrogenation of biofuels with formic acid over a palladium-based ternary catalyst with two types of active sites.

PubMed

Wang, Liang; Zhang, Bingsen; Meng, Xiangju; Su, Dang Sheng; Xiao, Feng-Shou

2014-06-01

A composite catalyst including palladium nanoparticles on titania (TiO2) and on nitrogen-modified porous carbon (Pd/TiO2@N-C) is synthesized from palladium salts, tetrabutyl titanate, and chitosan. N2 sorption isotherms show that the catalyst has a high BET surface area (229 m(2)  g(-1)) and large porosity. XPS and TEM characterization of the catalyst shows that palladium species with different chemical states are well dispersed across the TiO2 and nitrogen-modified porous carbon, respectively. The Pd/TiO2@N-C catalyst is very active and shows excellent stability towards hydrogenation of vanillin to 2-methoxy-4-methylphenol using formic acid as hydrogen source. This activity can be attributed to a synergistic effect between the Pd/TiO2 (a catalyst for dehydrogenation of formic acid) and Pd/N-C (a catalyst for hydrogenation of vanillin) sites. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

n-Hexane hydro-isomerization over promoted Pd/HZSM-5 catalysts

NASA Astrophysics Data System (ADS)

Thoa Dao, Thi Kim; Loc Luu, Cam

2015-09-01

A series of Pd/HZSM-5 catalysts modified by various metallic species, including Co, Ni, Fe, Re, and Cu, was prepared by sequential impregnation. Contents of Pd and second metals in modified catalysts were 0.8 and 1.0 wt%, respectively. Physico-chemical characteristics of catalysts were investigated by nitrogen physi-sorption (BET), x-ray diffraction (XRD), transmission electron microscopy (TEM), ammonia temperature programmed desorption (NH3-TPD), temperature programmed reduction (TPR) and hydrogen pulse chemisorption (HPC). Coke formation was studied by the method of thermogravimetric analysis (TGA). The activities of catalysts in n-hexane isomerization were studied in a micro-flow reactor under atmospheric pressure at 250 °C, and molar ratio of H2: n-hexane of 5.92. It was found that Co, Ni, Fe, and Re additives exhibited geometric and electronic effects toward Pd/HZSM-5 catalyst, leading to an enhancement of its activity and stability. On the contrary, Cu additive caused Pd/HZSM-5 to become poorer in activity and stability.

Covalent Chemical 5'-Functionalization of RNA with Diazo Reagents.

PubMed

Gampe, Christian M; Hollis-Symynkywicz, Micah; Zécri, Frédéric

2016-08-22

Functionalization of RNA at the 5'-terminus is important for analytical and therapeutic purposes. Currently, these RNAs are synthesized de novo starting with a chemically functionalized 5'-nucleotide, which is incorporated into RNA using chemical synthesis or biochemical techniques. Methods for direct chemical modification of native RNA would provide an attractive alternative but are currently underexplored. Herein, we report that diazo compounds can be used to selectively alkylate the 5'-phosphate of ribo(oligo)nucleotides to give RNA labelled through a native phosphate ester bond. We applied this method to functionalize oligonucleotides with biotin and an orthosteric inhibitor of the eukaryotic initiation factor 4E (eIF4E), an enzyme involved in mRNA recognition. The modified RNA binds to eIF4E, demonstrating the utility of this labelling technique to modulate biological activity of RNA. This method complements existing techniques and may be used to chemically introduce a broad range of functional handles at the 5'-end of RNA. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

(±)-Japonones A and B, two pairs of new enantiomers with anti-KSHV activities from Hypericum japonicum

NASA Astrophysics Data System (ADS)

Hu, Linzhen; Zhu, Hucheng; Li, Lei; Huang, Jinfeng; Sun, Weiguang; Liu, Junjun; Li, Hua; Luo, Zengwei; Wang, Jianping; Xue, Yongbo; Zhang, Yu; Zhang, Yonghui

2016-06-01

Two pairs of new enantiomers with unusual 5,5-spiroketal cores, termed (±)-japonones A and B [(±)-1 and (±)-2], were obtained from Hypericum japonicum Thunb. The absolute configurations of (±)-1 and (±)-2 were characterized by extensive analyses of spectroscopic data and calculated electronic circular dichroism (ECD) spectra, the application of modified Mosher’s methods, and the assistance of quantum chemical predictions (QCP) of 13C NMR chemical shifts. Among these metabolites, (+)-1 exhibited some inhibitory activity on Kaposi’s sarcoma associated herpesvirus (KSHV). Virtual screening of (±)-1 and (±)-2 were conducted using the Surflex-Dock module in the Sybyl software, and (+)-1 exhibited ability to bind with ERK to form key interactions with residues Lys52, Pro56, Ile101, Asp165, Gly167 and Val99.

Magnetorheological finishing of chemical-vapor deposited zinc sulfide via chemically and mechanically modified fluids.

PubMed

Salzman, Sivan; Romanofsky, Henry J; Giannechini, Lucca J; Jacobs, Stephen D; Lambropoulos, John C

2016-02-20

We describe the anisotropy in the material removal rate (MRR) of the polycrystalline, chemical-vapor deposited zinc sulfide (ZnS). We define the polycrystalline anisotropy via microhardness and chemical erosion tests for four crystallographic orientations of ZnS: (100), (110), (111), and (311). Anisotropy in the MRR was studied under magnetorheological finishing (MRF) conditions. Three chemically and mechanically modified magnetorheological (MR) fluids at pH values of 4, 5, and 6 were used to test the MRR variations among the four single-crystal planes. When polishing the single-crystal planes and the polycrystalline with pH 5 and pH 6 MR fluids, variations were found in the MRR among the four single-crystal planes and surface artifacts were observed on the polycrystalline material. When polishing the single-crystal planes and the polycrystalline with the modified MR fluid at pH 4, however, minimal variation was observed in the MRR among the four orientations and a reduction in surface artifacts was achieved on the polycrystalline material.

Expanding the chemical toolbox for the synthesis of large and uniquely modified proteins

NASA Astrophysics Data System (ADS)

Bondalapati, Somasekhar; Jbara, Muhammad; Brik, Ashraf

2016-05-01

Methods to prepare proteins that include a specific modification at a desired position are essential for understanding their cellular functions and physical properties in living systems. Chemical protein synthesis, which relies on the chemoselective ligation of unprotected peptides, enables the preparation of modified proteins that are not easily fabricated by other methods. In contrast to recombinant approaches, chemical synthesis can be used to prepare protein analogues such as D-proteins, which are useful in protein structure determination and the discovery of novel therapeutics. Post-translationally modifying proteins is another example where chemical protein synthesis proved itself as a powerful approach for preparing samples with high homogeneity and in workable quantities. In this Review, we discuss the basic principles of the field, focusing on novel chemoselective peptide ligation approaches such as native chemical ligation and the recent advances based on this method with a proven record of success in the synthesis of highly important protein targets.

Microencapsulation, Chemical Characterization, and Antimicrobial Activity of Mexican (Lippia graveolens H.B.K.) and European (Origanum vulgare L.) Oregano Essential Oils

PubMed Central

Regalado-González, Carlos; Vázquez-Landaverde, Pedro; Guerrero-Legarreta, Isabel; García-Almendárez, Blanca E.

2014-01-01

The effect of solvent polarity (methanol and pentane) on the chemical composition of hydrodistilled essential oils (EO's) of Lippia graveolens H.B.K. (MXO) and Origanum vulgare L. (EUO) was studied by GC-MS. Composition of modified starch microencapsulated EO's was conducted by headspace-solid-phase microextraction (HS-SPME). The antimicrobial activity of free and microencapsulated EO's was evaluated. They were tested against Salmonella sp., Brochothrix thermosphacta, Pseudomonas fragi, Lactobacillus plantarum, and Micrococcus luteus. Thymol and carvacrol were among the main components of EO's and their free and microencapsulated inhibitory activity was tested against M. luteus, showing an additive combined effect. Chemical composition of EO's varied according to the solvent used for GC analysis and to volatile fraction as evaluated by HS-SPME. Thymol (both solvents) was the main component in essential oil of MXO, while carvacrol was the main component of the volatile fraction. EUO showed α-pinene (methanol) and γ-terpinene (pentane) as major constituents, the latter being the main component of the volatile fraction. EO's showed good stability after 3 months storage at 4°C, where antimicrobial activity of microencapsulated EO's remained the same, while free EO's decreased 41% (MXO) and 67% (EUO) from initial activity. Microencapsulation retains most antimicrobial activity and improves stability of EO's from oregano. PMID:25177730

Microencapsulation, chemical characterization, and antimicrobial activity of Mexican (Lippia graveolens H.B.K.) and European (Origanum vulgare L.) oregano essential oils.

PubMed

Hernández-Hernández, Elvia; Regalado-González, Carlos; Vázquez-Landaverde, Pedro; Guerrero-Legarreta, Isabel; García-Almendárez, Blanca E

2014-01-01

The effect of solvent polarity (methanol and pentane) on the chemical composition of hydrodistilled essential oils (EO's) of Lippia graveolens H.B.K. (MXO) and Origanum vulgare L. (EUO) was studied by GC-MS. Composition of modified starch microencapsulated EO's was conducted by headspace-solid-phase microextraction (HS-SPME). The antimicrobial activity of free and microencapsulated EO's was evaluated. They were tested against Salmonella sp., Brochothrix thermosphacta, Pseudomonas fragi, Lactobacillus plantarum, and Micrococcus luteus. Thymol and carvacrol were among the main components of EO's and their free and microencapsulated inhibitory activity was tested against M. luteus, showing an additive combined effect. Chemical composition of EO's varied according to the solvent used for GC analysis and to volatile fraction as evaluated by HS-SPME. Thymol (both solvents) was the main component in essential oil of MXO, while carvacrol was the main component of the volatile fraction. EUO showed α-pinene (methanol) and γ-terpinene (pentane) as major constituents, the latter being the main component of the volatile fraction. EO's showed good stability after 3 months storage at 4°C, where antimicrobial activity of microencapsulated EO's remained the same, while free EO's decreased 41% (MXO) and 67% (EUO) from initial activity. Microencapsulation retains most antimicrobial activity and improves stability of EO's from oregano.

Modified NASA-Lewis chemical equilibrium code for MHD applications

NASA Technical Reports Server (NTRS)

Sacks, R. A.; Geyer, H. K.; Grammel, S. J.; Doss, E. D.

1979-01-01

A substantially modified version of the NASA-Lewis Chemical Equilibrium Code was recently developed. The modifications were designed to extend the power and convenience of the Code as a tool for performing combustor analysis for MHD systems studies. The effect of the programming details is described from a user point of view.

40 CFR 721.630 - Salt of a modified tallow alkylenediamine (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Salt of a modified tallow alkylenediamine (generic). 721.630 Section 721.630 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.630 Sal...

Enhancing saccharification of wheat straw by mixing enzymes from genetically-modified Trichoderma reesei and Aspergillus niger.

PubMed

Jiang, Yanping; Duarte, Alexandra Vivas; van den Brink, Joost; Wiebenga, Ad; Zou, Gen; Wang, Chengshu; de Vries, Ronald P; Zhou, Zhihua; Benoit, Isabelle

2016-01-01

To increase the efficiency of enzymatic hydrolysis for plant biomass conversion into renewable biofuel and chemicals. By overexpressing the point mutation A824 V transcriptional activator Xyr1 in Trichoderma reesei, carboxymethyl cellulase, cellobiosidase and β-D-glucosidase activities of the best mutant were increased from 1.8 IU/ml, 0.1 IU/ml and 0.05 IU/ml to 4.8 IU/ml, 0.4 IU/ml and 0.3 IU/ml, respectively. The sugar yield of wheat straw saccharification by combining enzymes from this mutant and the Aspergillus niger genetically modified strain ΔcreA/xlnR c/araR c was improved up to 7.5 mg/ml, a 229 % increase compared to the combination of wild type strains. Mixing enzymes from T. reesei and A. niger combined with the genetic modification of transcription factors is a promising strategy to increase saccharification efficiency.

Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium.

PubMed

Pullamsetty, Ashok; Sundara, Ramaprabhu

2016-10-01

Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts. Copyright © 2016 Elsevier Inc. All rights reserved.

Sulfation effect on levan polysaccharide chains structure with molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Coskunkan, Binnaz; Turgut, Deniz; Rende, Deniz; Malta, Seyda; Baysal, Nihat; Ozisik, Rahmi; Toksoy-Oner, Ebru

Diversity in conformations and structural heterogeneity make polysaccharides the most challenging biopolymer type for experimental and theoretical characterization studies. Levan is a biopolymer chain that consists of fructose rings with β(2-6) linkages. It is a glycan that has great potential as a functional biopolymer in foods, feeds, cosmetics, pharmaceutical and chemical industries. Sulfated polysaccharides are group of macromolecules with sulfated groups in their hydroxyl parts with a range of important biological properties. Sulfate groups and their positions have a major effect on anticoagulant activity. It is reported that sulfate modified levan has anticoagulant activity such as heparin. In the current study, the effect of sulfation on the structure and dynamics of unmodified and sulfate modified levan are investigated via fully atomistic Molecular Dynamics simulations in aqueous media and varying salt concentrations at 310 K. This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1538730.

Synthesis of block copolymers consists on vinylidene chloride and α- Methylstyrene by cationic polymerization using an acid exchanged motmorillonite clay as heterogeneous catalyst (Algerian MMT)

NASA Astrophysics Data System (ADS)

Ayat, Moulkheir; Belbachir, Mohamed; Rahmouni, Abdelkader

2017-07-01

The aim of this study was to develop the efficient and versatile method for the synthesis of block copolymers consists by cationic polymerization vinylidene chloride (VDC) and alpha-methylstyrene (alpha-MS) in the presence of a natural Algerian montmorillonite clay modified by 0.05-0.35 M H2SO4 (Algerian MMT-H+). It was found that H2SO4 concentration allows controlling the chemical composition, the porous structure of the acid-activated clays and their catalytic performance. The maximal yield of polymer is observed in the presence of Algerian MMT modified by 0.25 M H2SO4. Effects of VDC/MS molar ration, catalyst concentration, reaction time, reaction temperature and polarity medium on yield and molecular weight of polymer were revealed in the presence of the most active sample.

[In vitro studies on antioxidant and antimicrobial activities of polysaccharide from Lycoris aurea].

PubMed

Ru, Qiao-Mei; Pei, Zhen-Ming; Zheng, Hai-Lei

2008-10-01

To study the preliminary antioxidant and antimicrobial activities of polysaccharide extracted from Lycoris aurea. The scavenging activities of the polysaccharide in vitro on superoxide radical (O2-*), hydroxyl radical (*OH), alkyl radical (R*) and hydrogen peroxide (H2O2) were investigated by modified chemical systems. Meanwhile, the antimicrobial activities were tested using paper-discagar diffusion method. In general, the antioxidant activities of the polysaccharide were lower compared with Vc. However, the scavenging effects to *OH and H2O2 were parallel to Vc. Meanwhile, polysaccharide from Lycoris aurea had strong antimicrobial activities against Micrococcus luteus, Bacillus pumilus and Staphylococcus aureus. The polysaccharide extracted from L. aurea can scavenge *OH and H2O2 effectively and inhibit Gram-positive bacterias.

The determination of lead in sugar and sweets without digestion by electrothermal atomic absorption spectrometry (ETAAS) with a rhodium chemical modifier.

PubMed

Dias, V M C; Cardoso, A S B

2006-05-01

Reference methods for determining lead in food are usually time-consuming. This paper reports a straightforward procedure using electrothermal atomic absorption spectrometry (ETAAS), to determine lead (Pb) in fat-free sweets. Several chemical modifiers were examined and results showed that it is not necessary to digest the samples, when a rhodium (Rh) modifier was used. The samples were dissolved in nitric acid and the determination of Pb was performed by ETAAS, using Rh chemical modifier at a pyrolysis temperature of 900 degrees C and an atomization temperature of 1,500 degrees C. No ashing step was employed and aqueous standards were used, in the range 2-10 microg l(-1). The limit of quantification was 0.095 mg kg(-1), and the accuracy of the method was verified by analysing certified reference materials.

Total chemical synthesis of modified histones

NASA Astrophysics Data System (ADS)

Qi, Yun-Kun; Ai, Hua-Song; Li, Yi-Ming; Yan, Baihui

2018-02-01

In the post-genome era, epigenetics has received increasing attentions in recent years. The post-translational modifications (PTMs) of four core histones play central roles in epigenetic regulation of eukaryotic genome by either directly altering the biophysical properties of nucleosomes or by recruiting other effector proteins. In order to study the biological functions and structural mechanisms of these histone PTMs, an obligatory step is to prepare a sufficient amount of homogeneously modified histones. This task cannot be fully accomplished either by recombinant technology or enzymatic modification. In this context, synthetic chemists have developed novel protein synthetic tools and state-of-the-art chemical ligation strategies for the preparation of homologous modified histones. In this review, we summarize the recent advances in the preparation of modified histones, focusing on the total chemical synthesis strategies. The importance and potential of synthetic chemistry for the study of histone code will be also discussed.

Gold-supported cerium-doped NiO x catalysts for water oxidation

DOE PAGES

Ng, Jia Wei Desmond; García-Melchor, Max; Bajdich, Michal; ...

2016-04-29

Here, the development of high-performance catalysts for the oxygen-evolution reaction (OER) is paramount for cost-effective conversion of renewable electricity to fuels and chemicals. Here we report the significant enhancement of the OER activity of electrodeposited NiO x films resulting from the combined effects of using cerium as a dopant and gold as a metal support. This NiCeO x–Au catalyst delivers high OER activity in alkaline media, and is among the most active OER electrocatalysts yet reported. On the basis of experimental observations and theoretical modelling, we ascribe the activity to a combination of electronic, geometric and support effects, where highlymore » active under-coordinated sites at the oxide support interface are modified by the local chemical binding environment and by doping the host Ni oxide with Ce. The NiCeO x–Au catalyst is further demonstrated in a device context by pairing it with a nickel–molybdenum hydrogen evolution catalyst in a water electrolyser, which delivers 50 mA consistently at 1.5 V over 24 h of continuous operation.« less

Activated biochar: Preparation, characterization and electroanalytical application in an alternative strategy of nickel determination.

PubMed

Kalinke, Cristiane; Oliveira, Paulo Roberto; Oliveira, Geovane Arruda; Mangrich, Antonio Sálvio; Marcolino-Junior, Luiz H; Bergamini, Márcio F

2017-08-29

This work reports for the first time the use of chemically activated biochar as electrode modifier for nickel determination. The biochar activation was performed by refluxing with HNO 3 , which promoted a higher nickel preconcentration compared to unmodified and modified biochar precursor electrodes. Morphological and structural characterization revealed the increase of surface acid groups, surface area and porosity of biochar after activation. Nickel determination was investigated adopting an alternative voltammetric methodology based on monitoring the Ni(II)/Ni(III) redox couple. In the proposed method, it was not necessary to use a complexing agent and the biochar itself was responsible for the analyte preconcentration. A linear response for Ni(II) concentration range from 1.0 to 30 μmol L -1 and a limit of detection of 0.25 μmol L -1 were obtained. The method was successfully applied for Ni(II) determination in spiked samples of bioethanol fuel and discharge water, with recoveries values between 103 and 109%. Copyright © 2017 Elsevier B.V. All rights reserved.

Nanocomposite of polystyrene foil grafted with metallaboranes for antimicrobial activity

NASA Astrophysics Data System (ADS)

Benkocká, Monika; Kolářová, Kateřina; Matoušek, Jindřich; Semerádtová, Alena; Šícha, Václav; Kolská, Zdeňka

2018-05-01

The surface of polystyrene foil (PS) was chemically modified. Firstly, the surface was pre-treated with Piranha solution. The activated surface was grafted by selected amino-compounds (cysteamine, ethylenediamine or chitosan) and/or subsequently grafted with five members of inorganic metallaboranes. Selected surface properties were studied by using various methods in order to indicate significant changes before and after individual modification steps of polymer foil. Elemental composition of surface was conducted by using X-ray photoelectron spectroscopy, chemistry and polarity by infrared spectroscopy and by electrokinetic analysis, wettability by goniometry, surface morphology by atomic force microscopy. Antimicrobial tests were performed on individual samples in order to confirm antimicrobial impact. Our results show slight antibacterial activity of PS modified with SK5 for Escherichia coli in comparison with the rest of the tested borane. On the other hand molecules of all tested metallaboranes could easier pierce through bacterial cell of Staphylococcus epidermidis due to absence of outer membrane (phospholipid bilayer). Some borane grafted on PS surface embodies the strong activity for Staphylococcus epidermidis and also for Desmodesmus quadricauda growth inhibition.

Improved sensitivity by post-column chemical environment modification of CE-ESI-MS using a flow-through microvial interface.

PubMed

Risley, Jessica May; Chen, David Da Yong

2017-06-01

Post-column chemical environment modification can affect detection sensitivity and signal appearance when capillary electrophoresis is coupled through electrospray ionization to mass spectrometry (CE-ESI-MS). In this study, changes in the signal intensity and peak shape of N-Acetylneuraminic acid (Neu5Ac) were examined when the modifier solution used in a flow-through microvial interface for CE-ESI-MS was prepared using an acidic or basic background electrolyte (BGE) composition. The use of a basic modifier resulted in improved detection compared to the results obtained when an acidic modifier was used in negative ion mode. Increased sensitivity and more symmetrical peak shape were obtained. Using an acidic modifier, the LOD of Neu5Ac was 47.7 nM, whereas for a basic modifier, the LOD of Neu5Ac was 5.20 nM. The calculated asymmetry factor at 100 nM of Neu5Ac ranged from 0.71 to 1.5 when an acidic modifier was used, while the factor ranged from 1.0 to 1.1 when a basic modifier was used. Properly chosen post-column chemical modification can have a significant effect on the performance of the CE-MS system. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of nanohydroxyapaptite (nano-HA) coated epigallocatechin-3-gallate (EGCG) cross-linked collagen membranes.

PubMed

Chu, Chenyu; Deng, Jia; Man, Yi; Qu, Yili

2017-09-01

Collagen is the main component of extracellular matrix (ECM) with desirable biological activities and low antigenicity. Collagen materials have been widely utilized in guided bone regeneration (GBR) surgery due to its abilities to maintain space for hard tissue growth. However, pure collagen lacks optimal mechanical properties. In our previous study, epigallocatechin-3-gallate (EGCG) cross-linked collagen membranes, with better biological activities and enhanced mechanical properties, may promote osteoblast proliferation, but their effect on osteoblast differentiation is not very significant. Nanohydroxyapatite (nano-HA) is the main component of mineral bone, which possesses exceptional bioactivity properties including good biocompatibility, high osteoconductivity and osteoinductivity, non-immunogenicity and non-inflammatory behavior. Herein, by analyzing the physical and chemical properties as well as the effects on promoting bone regeneration, we have attempted to present a novel EGCG-modified collagen membrane with nano-HA coating, and have found evidence that the novel collagen membrane may promote bone regeneration with a better surface morphology, without destroying collagen backbone. To evaluate the surface morphologies, chemical and mechanical properties of pure collagen membranes, epigallocatechin-3-gallate (EGCG) cross-linked collagen membranes, nano-HA coated collagen membranes, nano-HA coated EGCG-collagen membranes, (ii) to evaluate the bone regeneration promoted by theses membranes. In the present study, collagen membranes were divided into 4 groups: (1) untreated collagen membranes (2) EGCG cross-linked collagen membranes (3) nano-HA modified collagen membranes (4) nano-HA modified EGCG-collagen membranes. Scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to evaluate surface morphologies and chemical properties, respectively. Mechanical properties were determined by differential scanning calorimeter (DSC) and elastic modulus (EM) measurements. Then in 12 rats, 4 types of membranes were randomly applied to cover the rat calvarial defects. The animals were sacrificed at 8weeks. Histologic analyses were performed using Hematoxylin-eosin (H&E) staining and Masson's Trichrome stains. For statistical analysis, analysis of variance (ANOVA) followed by Tukey's multiple comparison tests was applied. HA nanoparticles were fairly well distributed nanoparticles among the collagen fibers on the nano-HA-modified EGCG-collagen membranes, with smoother surface. Moreover, collagen membranes with modifications all maintained their collagen backbone and the mechanical properties were enhanced by EGCG and nano-HA treatments. In addition, EGCG cross-linked collagen membranes with nano-HA coatings promoted bone regeneration. Nano-HA modified EGCG-collagen membranes can be utilized as a barrier membrane to enhance the bone regeneration in GBR surgeries. Copyright © 2017 Elsevier B.V. All rights reserved.

Direct-push geochemical profiling for assessment of inorganic chemical heterogeneity in aquifers

USGS Publications Warehouse

Schulmeister, M.K.; Healey, J.M.; Butler, J.J.; McCall, G.W.

2004-01-01

Discrete-depth sampling of inorganic groundwater chemistry is essential for a variety of site characterization activities. Although the mobility and rapid sampling capabilities of direct-push techniques have led to their widespread use for evaluating the distribution of organic contaminants, complementary methods for the characterization of spatial variations in geochemical conditions have not been developed. In this study, a direct-push-based approach for high-resolution inorganic chemical profiling was developed at a site where sharp chemical contrasts and iron-reducing conditions had previously been observed. Existing multilevel samplers (MLSs) that span a fining-upward alluvial sequence were used for comparison with the direct-push profiling. Chemical profiles obtained with a conventional direct-push exposed-screen sampler differed from those obtained with an adjacent MLS because of sampler reactivity and mixing with water from previous sampling levels. The sampler was modified by replacing steel sampling components with stainless-steel and heat-treated parts, and adding an adapter that prevents mixing. Profiles obtained with the modified approach were in excellent agreement with those obtained from an adjacent MLS for all constituents and parameters monitored (Cl, NO3, Fe, Mn, DO, ORP, specific conductance and pH). Interpretations of site redox conditions based on field-measured parameters were supported by laboratory analysis of dissolved Fe. The discrete-depth capability of this approach allows inorganic chemical variations to be described at a level of detail that has rarely been possible. When combined with the mobility afforded by direct-push rigs and on-site methods of chemical analysis, the new approach is well suited for a variety of interactive site-characterization endeavors. ?? 2003 Elsevier B.V. All rights reserved.

The role of Dynamic Energy Budget theory in predictive modeling of stressor impacts on ecological systems. Comment on: ;Physics of metabolic organization; by Marko Jusup et al.

NASA Astrophysics Data System (ADS)

Galic, Nika; Forbes, Valery E.

2017-03-01

Human activities have been modifying ecosystems for centuries, from pressures on wild populations we harvest to modifying habitats through urbanization and agricultural activities. Changes in global climate patterns are adding another layer of, often unpredictable, perturbations to ecosystems on which we rely for life support [1,2]. To ensure the sustainability of ecosystem services, especially at this point in time when the human population is estimated to grow by another 2 billion by 2050 [3], we need to predict possible consequences of our actions and suggest relevant solutions [4,5]. We face several challenges when estimating adverse impacts of our actions on ecosystems. We describe these in the context of ecological risk assessment of chemicals. Firstly, when attempting to assess risk from exposure to chemicals, we base our decisions on a very limited number of species that are easily cultured and kept in the lab. We assume that preventing risk to these species will also protect all of the untested species present in natural ecosystems [6]. Secondly, although we know that chemicals interact with other stressors in the field, the number of stressors that we can test is limited due to logistical and ethical reasons. Similarly, empirical approaches are limited in both spatial and temporal scale due to logistical, financial and ethical reasons [7,8]. To bypass these challenges, we can develop ecological models that integrate relevant life history and other information and make testable predictions across relevant spatial and temporal scales [8-10].

Engineering the internal surfaces of three-dimensional nanoporous catalysts by surfactant-modified dealloying.

PubMed

Wang, Zhili; Liu, Pan; Han, Jiuhui; Cheng, Chun; Ning, Shoucong; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

2017-10-20

Tuning surface structures by bottom-up synthesis has been demonstrated as an effective strategy to improve the catalytic performances of nanoparticle catalysts. Nevertheless, the surface modification of three-dimensional nanoporous metals, fabricated by a top-down dealloying approach, has not been achieved despite great efforts devoted to improving the catalytic performance of three-dimensional nanoporous catalysts. Here we report a surfactant-modified dealloying method to tailor the surface structure of nanoporous gold for amplified electrocatalysis toward methanol oxidation and oxygen reduction reactions. With the assistance of surfactants, {111} or {100} faceted internal surfaces of nanoporous gold can be realized in a controllable manner by optimizing dealloying conditions. The surface modified nanoporous gold exhibits significantly enhanced electrocatalytic activities in comparison with conventional nanoporous gold. This study paves the way to develop high-performance three-dimensional nanoporous catalysts with a tunable surface structure by top-down dealloying for efficient chemical and electrochemical reactions.

Research of Adhesion Bonds Between Gas-Thermal Coating and Pre-Modified Base

NASA Astrophysics Data System (ADS)

Kovalevskaya, Z.; Zaitsev, K.; Klimenov, V.

2016-08-01

Nature of adhesive bonds between gas-thermal nickel alloy coating and carbon steel base was examined using laser profilometry, optical metallography, transmission and scanning electron microscopy. The steel surface was plastically pre-deformed by an ultrasonic tool. Proved that ultrasound pre-treatment modifies the steel surface. Increase of dislocation density and formation of sub micro-structure are base elements of surface modification. While using high-speed gas-flame, plasma and detonation modes of coatings, surface activation occurs and durable adhesion is formed. Ultrasonic pre-treatment of base material is effective when sprayed particles and base material interact through physical-chemical bond formation. Before applying high-speed gas flame and plasma sprayed coatings, authors recommend ultrasonic pretreatment, which creates periodic wavy topography with a stroke of 250 microns on the steel surface. Before applying detonation sprayed coatings, authors recommend ultrasound pretreatment that create modified surface with a uniform micro-topography.

Suppression of experimental autoimmune diseases and prolongation of allograft survival by treatment of animals with low doses of heparins.

PubMed

Lider, O; Baharav, E; Mekori, Y A; Miller, T; Naparstek, Y; Vlodavsky, I; Cohen, I R

1989-03-01

The ability of activated T lymphocytes to penetrate the extracellular matrix and migrate to target tissues was found to be related to expression of a heparanase enzyme (Naparstek, Y., I. R. Cohen, Z. Fuks, and I. Vlodavsky. 1984. Nature (Lond.). 310:241-243; Savion, N., Z. Fuks, and I. Vlodavsky. 1984. J. Cell. Physiol. 118:169-176; Fridman, R., O. Lider, Y. Naparstek, Z. Fuks, I. Vlodavsky, and I. R. Cohen. 1987. J. Cell. Physiol. 130:85-92; Lider, O., J. Mekori, I. Vlodavsky, E. Baharav, Y. Naparstek, and I. R. Cohen, manuscript submitted for publication). We found previously that heparin molecules inhibited expression of T lymphocyte heparanase activity in vitro and in vivo, and administration of a low dose of heparin in mice inhibited lymphocyte traffic and delayed-type hypersensitivity reactions (Lider, O., J. Mekori, I. Vlodavsky, E. Baharav, Y. Naparstek, and I. R. Cohen, manuscript submitted for publication). We now report that treatment with commercial or chemically modified heparins at relatively low doses once daily (5 micrograms for mice and 20 micrograms for rats) led to inhibition of allograft rejection and the experimental autoimmune diseases adjuvant arthritis and experimental autoimmune encephalomyelitis. Higher doses of the heparins were less effective. The ability of chemically modified heparins to inhibit these immune reactions was associated with their ability to inhibit expression of T lymphocyte heparanase. There was no relationship to anticoagulant activity. Thus heparins devoid of anticoagulant activity can be effective in regulating immune reactions when used at appropriate doses.

Chemical Composition and Antibacterial Activity of Essential Oils of Tagetes minuta (Asteraceae) against Selected Plant Pathogenic Bacteria

PubMed Central

Wagacha, John M.; Dossaji, Saifuddin F.

2016-01-01

The objective of this study was to determine the chemical composition and antibacterial activity of essential oils (EOs) of Tagetes minuta against three phytopathogenic bacteria Pseudomonas savastanoi pv. phaseolicola, Xanthomonas axonopodis pv. phaseoli, and Xanthomonas axonopodis pv. manihotis. The essential oils were extracted using steam distillation method in a modified Clevenger-type apparatus while antibacterial activity of the EOs was evaluated by disc diffusion method. Gas chromatography coupled to mass spectrometry (GC/MS) was used for analysis of the chemical profile of the EOs. Twenty compounds corresponding to 96% of the total essential oils were identified with 70% and 30% of the identified components being monoterpenes and sesquiterpenes, respectively. The essential oils of T. minuta revealed promising antibacterial activities against the test pathogens with Pseudomonas savastanoi pv. phaseolicola being the most susceptible with mean inhibition zone diameters of 41.83 and 44.83 mm after 24 and 48 hours, respectively. The minimum inhibitory concentrations and minimum bactericidal concentrations of the EOs on the test bacteria were in the ranges of 24–48 mg/mL and 95–190 mg/mL, respectively. These findings provide a scientific basis for the use of T. minuta essential oils as a botanical pesticide for management of phytopathogenic bacteria. PMID:27721831

Extranuclear-initiated estrogenic actions of endocrine disrupting chemicals: Is there toxicology beyond paracelsus?

PubMed

Nadal, Angel; Fuentes, Esther; Ripoll, Cristina; Villar-Pazos, Sabrina; Castellano-Muñoz, Manuel; Soriano, Sergi; Martinez-Pinna, Juan; Quesada, Ivan; Alonso-Magdalena, Paloma

2018-02-01

Endocrine Disrupting Chemicals (EDCs), including bisphenol-A (BPA) do not act as traditional toxic chemicals inducing massive cell damage or death in an unspecific manner. EDCs can work upon binding to hormone receptors, acting as agonists, antagonists or modulators. Bisphenol-A displays estrogenic activity and, for many years it has been classified as a weak estrogen, based on the classic transcriptional action of estrogen receptors serving as transcription factors. However, during the last two decades our knowledge about estrogen signaling has advanced considerably. It is now accepted that estrogen receptors ERα and ERβ activate signaling pathways outside the nucleus which may or may not involve transcription. In addition, a new membrane estrogen receptor, GPER, has been proposed. Pharmacological and molecular evidence, along with results obtained in genetically modified mice, demonstrated that BPA, and its substitute BPS, are potent estrogens acting at nanomolar concentrations via extranuclear ERα, ERβ, and GPER. The different signaling pathways activated by BPA and BPS explain the well-known estrogenic effects of low doses of EDCs as well as non-monotonic dose-response relationships. These signaling pathways may help to explain the actions of EDCs with estrogenic activity in the etiology of different pathologies, including type-2 diabetes and obesity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Investigation of Ag-TiO2 nanostructures photocatalytic properties prepared by modified dip coating method

NASA Astrophysics Data System (ADS)

AlArfaj, Esam

2016-05-01

In this article, titanium dioxide and silver nanostructures were deposited on glass substrates using modified sol-gel methods and dip-coating technique. The films were characterised chemically and physically using different techniques (TLC, UV-Vis and XRD) and tested for environmental applications regarding degradation of aromatic hydrocarbons. The photocatalytic activity of the TiO2 nanostructures is tested with different small concentrations of phenol in water and reaction mechanisms discussed. Considerable enhancement is observed in the photodegradation activity of Ag-modified (3 wt.%) TiO2 compared to unmodified TiO2 nanostructures for phenol concentrations within the pseudo-first-order Langmuir-Hinshelwood (LH) model for reaction kinetics. The pseudo-first-order global degradation rate constant increased from <0.005 min-1 for TiO2 to 0.013 min-1 for 3 mol% Ag-modified TiO2. The enhancement is attributed to the incorporation of Ag which promotes the generation of reactive oxygen species and increases the carrier recombination life-time. In addition, Ag has been observed to extend the absorption to the visible region by its surface plasmon resonances and to suppress the anatase-rutile phase transformation. Moreover, TiO2 grain size prepared was found to be 10 nm which maximises the active surface area. For phenol initial concentrations as low as 0.0002 M, saturation trend in the degradation process occurred at 0.00014 M and the reaction rate can be fitted with half-order LH kinetics.

Performance enhancement in organic photovoltaic solar cells using iridium (Ir) ultra-thin surface modifier (USM)

NASA Astrophysics Data System (ADS)

Pandey, Rina; Lim, Ju Won; Kim, Jung Hyuk; Angadi, Basavaraj; Choi, Ji Won; Choi, Won Kook

2018-06-01

In this study, Iridium (Ir) metallic layer as an ultra-thin surface modifier (USM) was deposited on ITO coated glass substrate using radio frequency magnetron sputtering for improving the photo-conversion efficiency of organic photovoltaic cells. Ultra-thin Ir acts as a surface modifier replacing the conventional hole transport layer (HTL) PEDOT:PSS in organic photovoltaic (OPV) cells with two different active layers P3HT:PC60BM and PTB7:PC70BM. The Ir USM (1.0 nm) coated on ITO glass substrate showed transmittance of 84.1% and work function of >5.0 eV, which is higher than that of ITO (4.5-4.7 eV). The OPV cells with Ir USM (1.0 nm) exhibits increased power conversion efficiency of 3.70% (for P3HT:PC60BM active layer) and 7.28% (for PTB7:PC70BM active layer) under 100 mW/cm2 illumination (AM 1.5G) which are higher than those of 3.26% and 6.95% for the same OPV cells but with PEDOT:PSS as HTL instead of Ir USM. The results reveal that the chemically stable Ir USM layer could be used as an alternative material for PEDOT:PSS in organic photovoltaic cells.

Electrochemical detection of uric acid via uricase-immobilized graphene oxide.

PubMed

Omar, Muhamad Nadzmi; Salleh, Abu Bakar; Lim, Hong Ngee; Ahmad Tajudin, Asilah

2016-09-15

Measurement of the uric acid level in the body can be improved by biosensing with respect to the accuracy, sensitivity and time consumption. This study has reported the immobilization of uricase onto graphene oxide (GO) and its function for electrochemical detection of uric acid. Through chemical modification of GO using 1-ethyl-3-(dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS) as cross-linking reagents, the enzyme activity of the immobilized uricase was much comparable to the free enzyme with 88% of the activity retained. The modified GO-uricase (GOU) was then subjected to electrocatalytic detection of uric acid (UA) via cyclic voltammetry (CV). For that reason, a glassy carbon electrode (GCE) was modified by adhering the GO along with the immobilized uricase to facilitate the redox reaction between the enzyme and the substrate. The modified GOU/GCE outperformed a bare electrode through the electrocatalytic activity with an amplified electrical signal for the detection of UA. The electrocatalytic response showed a linear dependence on the UA concentration ranging from 0.02 to 0.49 mM with a detection limit of 3.45 μM at 3σ/m. The resulting biosensor also exhibited a high selectivity towards UA in the presence of other interference as well as good reproducibility. Copyright © 2016 Elsevier Inc. All rights reserved.

Biotic and abiotic characterization of bioanodes formed on oxidized carbon electrodes as a basis to predict their performance.

PubMed

Cercado, Bibiana; Cházaro-Ruiz, Luis Felipe; Ruiz, Vianey; López-Prieto, Israel de Jesús; Buitrón, Germán; Razo-Flores, Elías

2013-12-15

Bioelectrochemical systems (BESs) are based on the catalytic activity of biofilm on electrodes, or the so-called bioelectrodes, to produce electricity and other valuable products. In order to increase bioanode performance, diverse electrode materials and modification methods have been implemented; however, the factors directly affecting performance are yet unclear. In this work carbon cloth electrodes were modified by thermal, chemical, and electrochemical oxidation to enhance oxygenated surface groups, to modify the electrode texture, and consequently the electron transfer rate and biofilm adhesion. The oxidized electrodes were physically, chemically, and electrochemically characterized, then bioanodes were formed at +0.1 V vs. Ag/AgCl using domestic wastewater amended with acetate. The bioanode performance was evaluated according to the current and charge generated. The efficacy of the treatments were in the order Thermal>Electrochemical>Untreated>Chemical oxidation. The maximum current observed with untreated electrode was 0.152±0.026 mA (380±92 mA m(-2)), and it was increased by 78% and 28% with thermal and electrochemical oxidized electrodes, respectively. Moreover, the volatile solids correlated significantly with the maximum current obtained, and the electrode texture was revealed as a critical factor for increasing the bioanode performance. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of Montmorillonite Nanogel Composite Fillers on the Protection Performance of Epoxy Coatings on Steel Pipelines.

PubMed

Atta, Ayman M; El-Saeed, Ashraf M; Al-Lohedan, Hamad A; Wahby, Mohamed

2017-06-02

Montmorillonite (MMT) clay mineral is widely used as filler for several organic coatings. Its activity is increased by exfoliation via chemical modification to produce nanomaterials. In the present work, the modification of MMT to form nanogel composites is proposed to increase the dispersion of MMT into epoxy matrices used to fill cracks and holes produced by the curing exotherms of epoxy resins. The dispersion of MMT in epoxy improved both the mechanical and anti-corrosion performance of epoxy coatings in aggressive marine environments. In this respect, the MMT surfaces were chemically modified with different types of 2-acrylamido-2-methyl propane sulfonic acid (AMPS) nanogels using a surfactant-free dispersion polymerization technique. The effect of the chemical structure, nanogel content and the interaction with MMT surfaces on the surface morphology, surface charges and dispersion in the epoxy matrix were investigated for use as nano-filler for epoxy coatings. The modified MMT nanogel epoxy composites showed excellent resistance to mechanical damage and salt spray resistance up to 1000 h. The interaction of MMT nanogel composites with the epoxy matrix and good response of AMPS nanogel to sea water improve their ability to act as self-healing materials for epoxy coatings for steel.

The role of chemical transport in the brown-rot decay resistance of modified wood

Treesearch

Samuel Zelinka; R. Ringman; A. Pilgard; E. E. Thybring; Joseph Jakes; K. Richter

2016-01-01

Chemical modification of wood increases decay resistance but the exact mechanisms remain poorly understood. Recently, Ringman and coauthors examined established theories addressing why modified wood has increased decay resistance and concluded that the most probable cause of inhibition and/or delay of initiation of brown-rot decay is lowering the equilibrium moisture...

Selective adsorption of bovine hemoglobin on functional TiO2 nano-adsorbents: surface physic-chemical properties determined adsorption activity

NASA Astrophysics Data System (ADS)

Guo, Shiguang; Zhang, Jianghua; Shao, Mingxue; Zhang, Xia; Liu, Yufeng; Xu, Junli; Meng, Hao; Han, Yide

2015-04-01

Surface functionalized nanoparticles are efficient adsorbents which have shown good potential for protein separation. In this work, we chose two different types of organic molecules, oleic acid (OA) and 3-glycidoxypropyltrimethoxy silane (GPTMS), to functionalize the surface of TiO2 nanoparticles, and we studied the effects of this modification on their surface physicochemical properties in correlation with their selective adsorption of proteins. The results showed that the surface zeta potential and the surface water wettability of the modified TiO2 were significantly changed in comparison with the original TiO2 nanoparticles. The adsorption activities of bovine hemoglobin (BHb) and bovine serum albumin (BSA) on these functionalized TiO2 samples were investigated under different conditions, including pH values, contact time, ion strength, and initial protein concentration. In comparison with the non-specific adsorption of original TiO2, however, both the OA-TiO2 and GPTMS-TiO2 exhibited increased BHb adsorption and decreased BSA adsorption at the same time. Using a binary protein mixture as the adsorption object, a higher separation factor (SF) was obtained for OA-TiO2 under optimum conditions. The different adsorption activities of BHb and BSA on the modified TiO2 were correlated with different interactions at the protein/solid interface, and the chemical force as well as the electrostatic force played an important role in the selective adsorption process.

Photoelectrocatalytic reduction of CO2 into chemicals using Pt-modified reduced graphene oxide combined with Pt-modified TiO2 nanotubes.

PubMed

Cheng, Jun; Zhang, Meng; Wu, Gai; Wang, Xin; Zhou, Junhu; Cen, Kefa

2014-06-17

The photoelectrocatalytic (PEC) reduction of CO2 into high-value chemicals is beneficial in alleviating global warming and advancing a low-carbon economy. In this work, Pt-modified reduced graphene oxide (Pt-RGO) and Pt-modified TiO2 nanotubes (Pt-TNT) were combined as cathode and photoanode catalysts, respectively, to form a PEC reactor for converting CO2 into valuable chemicals. XRD, XPS, TEM, AFM, and SEM were employed to characterize the microstructures of the Pt-RGO and Pt-TNT catalysts. Reduction products, such as C2H5OH and CH3COOH, were obtained from CO2 under band gap illumination and biased voltage. A combined liquid product generation rate (CH3OH, C2H5OH, HCOOH, and CH3COOH) of approximately 600 nmol/(h·cm(2)) was observed. Carbon atom conversion rate reached 1,130 nmol/(h·cm(2)), which were much higher than those achieved using Pt-modified carbon nanotubes and platinum carbon as cathode catalysts.

Self-propulsion of a catalytically active particle near a planar wall: from reflection to sliding and hovering.

PubMed

Uspal, W E; Popescu, M N; Dietrich, S; Tasinkevych, M

2015-01-21

Micron-sized particles moving through a solution in response to self-generated chemical gradients serve as model systems for studying active matter. Their far-reaching potential applications will require the particles to sense and respond to their local environment in a robust manner. The self-generated hydrodynamic and chemical fields, which induce particle motion, probe and are modified by that very environment, including confining boundaries. Focusing on a catalytically active Janus particle as a paradigmatic example, we predict that near a hard planar wall such a particle exhibits several scenarios of motion: reflection from the wall, motion at a steady-state orientation and height above the wall, or motionless, steady "hovering." Concerning the steady states, the height and the orientation are determined both by the proportion of catalyst coverage and the interactions of the solutes with the different "faces" of the particle. Accordingly, we propose that a desired behavior can be selected by tuning these parameters via a judicious design of the particle surface chemistry.

An Overview of Recent Development in Composite Catalysts from Porous Materials for Various Reactions and Processes

PubMed Central

Xie, Zaiku; Liu, Zhicheng; Wang, Yangdong; Yang, Qihua; Xu, Longya; Ding, Weiping

2010-01-01

Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT), etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts. PMID:20559508

Biological Nanoplatforms for Self-Assembled Electronics

DTIC Science & Technology

2015-03-24

as M13 , a virus that infects Escherichia coli. Approximately one billion different amino acid sequences are displayed on different viruses in the...sequence when contained within a phage M13 coat protein sequence, not chemically linked to the surface of phage MS2 VLPs. Thus, binding properties may...gallium arsenide in a bacteriophage M13 phage display library, MS2 VLPs modified with the metal binding peptides do not display the same activity

Calcium Channels: Structure and Function (Annals of the New York Academy of Sciences. Volume 560)

DTIC Science & Technology

1989-06-26

many protease inhibitors were used , we believe that proteolysis was a problem. We therefore modified our purification protocol and have obtained a...recover activity by selective combination of fractions were unsuccessful. Chemical Cross-Linking of [ 25 Jo-CgTX Cross-linking of w-CgTX derivatives using ... using the planar bilayer recording technique and by comparing ligand-dependent gating, ionic selectivity , and pharmacology of purified ryanodine

Metal and Oxide Additives as Agents for Munitions Self-Remediation

DTIC Science & Technology

2010-07-01

properties of TiO2 can be modified by adding various dopants which serve to expand the range of light energy adsorbed into the visible part of the...spectrum. Photocatalyst development is an extremely active area of research with respect to both substrate and dopant . The selection of an anatase...based photocatalyst is largely due to its established dominance and chemical stability (Diebold 2003). Tungsten trioxide (WO3) is one of many dopants

Chemical composition, antioxidant and antibacterial activities of essential oils from leaves and flowers of Eugenia klotzschiana Berg (Myrtaceae).

PubMed

Carneiro, Nárgella S; Alves, Cassia C F; Alves, José M; Egea, Mariana B; Martins, Carlos H G; Silva, Thayná S; Bretanha, Lizandra C; Balleste, Maira P; Micke, Gustavo A; Silveira, Eduardo V; Miranda, Mayker L D

2017-01-01

Many essential oils (EOs) of different plant species possess interesting antimicrobial effects on buccal bacteria and antioxidant properties. Eugenia klotzschiana Berg (pêra-do-cerrado, in Portuguese) is a species of Myrtaceae with restricted distribution in the Cerrado. The essential oils were extracted through the hydrodistillation technique using a modified Clevenger apparatus (2 hours) and chemically characterized by GC-MS. The major compounds were α-copaene (10.6 %) found in oil from leaves in natura, β-bisabolene (17.4 %) in the essential oil from dry leaves and α-(E)-bergamotene (29.9 %) in oil from flowers. The antioxidant activity of essential oils showed similarities in both methods under analysis (DPPH and ABTS˙+) and the results suggested moderate to high antioxidant activity. The antibacterial activity was evaluated by determining minimum inhibitory concentrations (MICs), using the microdilution method. MIC values below 400 µg/mL were obtained against Streptococcus salivarius (200 µg/mL), S. mutans (50 µg/mL), S. mitis (200 µg/mL) and Prevotella nigrescens (50 µg/mL). This is the first report of the chemical composition and antibacterial and antioxidant activities of the essential oils of E. klotzschiana. These results suggest that E. klotzschiana, a Brazilian plant, provide initial evidence of a new and alternative source of substances with medicinal interest.

Scale-Invariant Forms of Conservation Equations in Reactive Fields and a Modified Hydro-Thermo-Diffusive Theory of Laminar Flames

NASA Technical Reports Server (NTRS)

Sohrab, Siavash H.; Piltch, Nancy (Technical Monitor)

2000-01-01

A scale-invariant model of statistical mechanics is applied to present invariant forms of mass, energy, linear, and angular momentum conservation equations in reactive fields. The resulting conservation equations at molecular-dynamic scale are solved by the method of large activation energy asymptotics to describe the hydro-thermo-diffusive structure of laminar premixed flames. The predicted temperature and velocity profiles are in agreement with the observations. Also, with realistic physico-chemical properties and chemical-kinetic parameters for a single-step overall combustion of stoichiometric methane-air premixed flame, the laminar flame propagation velocity of 42.1 cm/s is calculated in agreement with the experimental value.

Improving the catalytic activity of amorphous molybdenum sulfide for hydrogen evolution reaction using polydihydroxyphenylalanine modified MWCNTs

NASA Astrophysics Data System (ADS)

Li, Maoguo; Yu, Muping; Li, Xiang

2018-05-01

Molybdenum sulfides are promising electrocatalysts for hydrogen evolution reaction (HER) in acid medium due to their unique properties. In order to improve their HER activity, different strategies have been developed. In this study, amorphous molybdenum sulfide was prepared by a simple wet chemical method and its HER activity was further improved by using polydihydroxyphenylalanine (PDOPA) modified MWCNTs as supports. It was found that the PDOPA can effectively improve the hydrophilic properties of multiwalled carbon nanotubes (MWCNTs) and amorphous MoSx can uniformly grow on the surface of PDOPA@MWCNTs. Compared with MoSx and MoSx/MWCNTs, MoSx/PDOPA@MWCNTs show obviously enhanced HER activities due to the superior electrical conductivity and more exposed active sites. In addition, the effect of the ratio of MoSx and PDOPA@MWCNTs and the loading amount of catalysts on the electrodes are also investigated in detail. At the optimum conditions, MoSx/PDOPA@MWCNTs display an overpotential of 198 mV at 10 mA/cm2, a Tafel slope of 53 mV/dec and a good long-term stability in 0.5 M H2SO4, which make them promising candidates for HER application.

Is Allelopathic Activity of Ipomoea murucoides Induced by Xylophage Damage?

PubMed

Flores-Palacios, Alejandro; Corona-López, Angélica María; Rios, María Yolanda; Aguilar-Guadarrama, Berenice; Toledo-Hernández, Víctor Hugo; Rodríguez-López, Verónica; Valencia-Díaz, Susana

2015-01-01

Herbivory activates the synthesis of allelochemicals that can mediate plant-plant interactions. There is an inverse relationship between the activity of xylophages and the abundance of epiphytes on Ipomoea murucoides. Xylophagy may modify the branch chemical constitution, which also affects the liberation of allelochemicals with defense and allelopathic properties. We evaluated the bark chemical content and the effect of extracts from branches subjected to treatments of exclusion, mechanical damage and the presence/absence of epiphytes, on the seed germination of the epiphyte Tillandsia recurvata. Principal component analysis showed that branches without any treatment separate from branches subjected to treatments; damaged and excluded branches had similar chemical content but we found no evidence to relate intentional damage with allelopathy; however 1-hexadecanol, a defense volatile compound correlated positively with principal component (PC) 1. The chemical constitution of branches subject to exclusion plus damage or plus epiphytes was similar among them. PC2 indicated that palmitic acid (allelopathic compound) and squalene, a triterpene that attracts herbivore enemies, correlated positively with the inhibition of seed germination of T. recurvata. Inhibition of seed germination of T. recurvata was mainly correlated with the increment of palmitic acid and this compound reached higher concentrations in excluded branches treatments. Then, it is likely that the allelopathic response of I. murucoides would increase to the damage (shade, load) that may be caused by a high load of epiphytes than to damage caused by the xylophages.

Process for preparing chemically modified micas for removal of cesium salts from aqueous solution

DOEpatents

Yates, Stephen Frederic; DeFilippi, Irene; Gaita, Romulus; Clearfield, Abraham; Bortun, Lyudmila; Bortun, Anatoly

2000-09-05

A chemically modified mica composite formed by heating a trioctahedral mica in an aqueous solution of sodium chloride having a concentration of at least 1 mole/liter at a temperature greater than 180 degrees Centigrade for at least 20 hours, thereby replacing exchangeable ions in the mica with sodium. Formation is accomplished at temperatures and pressures which are easily accessed by industrial equipment. The reagent employed is inexpensive and non-hazardous, and generates a precipitate which is readily separated from the modified mica.

Manganese-modified asphalts : chemistry of the curing reaction, its effect on properties, and evidence for manganese inactivation following cure

DOT National Transportation Integrated Search

1986-06-01

The chemical reactions and reaction kinetics of asphalt modified with a patented modifier supplied by Chemkrete Technologies, Inc. were investigated. The modifier, a manganese-carboxylic acid complex, has been shown to cause a rap; d react; on with a...

40 CFR 721.10603 - Epoxy modified alkyd resin, partially neutralized (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Epoxy modified alkyd resin, partially... Specific Chemical Substances § 721.10603 Epoxy modified alkyd resin, partially neutralized (generic). (a... generically as epoxy modified alkyd resin, partially neutralized (PMN P-11-280) is subject to reporting under...

40 CFR 721.10603 - Epoxy modified alkyd resin, partially neutralized (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Epoxy modified alkyd resin, partially... Specific Chemical Substances § 721.10603 Epoxy modified alkyd resin, partially neutralized (generic). (a... generically as epoxy modified alkyd resin, partially neutralized (PMN P-11-280) is subject to reporting under...

Fabrication of Annealed Gold Nanostructures on Pre-Treated Glow-Discharge Cleaned Glasses and Their Used for Localized Surface Plasmon Resonance (LSPR) and Surface Enhanced Raman Spectroscopy (SERS) Detection of Adsorbed (Bio)molecules.

PubMed

Ionescu, Rodica Elena; Aybeke, Ece Neslihan; Bourillot, Eric; Lacroute, Yvon; Lesniewska, Eric; Adam, Pierre-Michel; Bijeon, Jean-Louis

2017-01-26

Metallic nanoparticles are considered as active supports in the development of specific chemical or biological biosensors. Well-organized nanoparticles can be prepared either through expensive (e.g., electron beam lithography) or inexpensive (e.g., thermal synthesis) approaches where different shapes of nanoparticles are easily obtained over large solid surfaces. Herein, the authors propose a low-cost thermal synthesis of active plasmonic nanostructures on thin gold layers modified glass supports after 1 h holding on a hot plate (~350 °C). The resulted annealed nanoparticles proved a good reproducibility of localized surface plasmon resonance (LSPR) and surface enhanced Raman spectroscopy (SERS) optical responses and where used for the detection of low concentrations of two model (bio)chemical molecules, namely the human cytochrome b5 (Cyt-b5) and trans -1,2-bis(4-pyridyl)ethylene (BPE).

Phosphatase-Resistant Analogues of Lysophosphatidic Acid

PubMed Central

Prestwich, Glenn D.; Gajewiak, Joanna; Zhang, Honglu; Xu, Xiaoyu; Yang, Guanghui; Serban, Monica

2008-01-01

Isoform-selective agonists and antagonists of the lysophosphatidic acid (LPA) G protein coupled receptors (GPCRs) have important potential applications in cell biology and therapy. LPA GPCRs regulate cancer cell proliferation, invasion, angiogenesis, and also biochemical resistance to chemotherapy- and radiotherapy-induced apoptosis. LPA and its analogues also are feedback inhibitors of the enzyme lysophospholipase D (lysoPLD, a.k.a., autotaxin, ATX), a central regulator of invasion and metastasis. For cancer therapy, the optimal therapeutic profile would be a metabolically stabilized, pan-LPA receptor antagonist that also inhibited lysoPLD. For protection of gastrointestinal mucosa and lymphocytes, LPA agonists would be desirable to minimize or reverse radiation or chemical-induced injury. Analogues of lysophosphatidic acid (LPA) that are chemically modified to be less susceptible to phospholipases and phosphatases show activity as long-lived receptor-specific agonists and antagonists for LPA receptors, as well as inhibitors for the lysoPLD activity of ATX. PMID:18454946

A New Green Ionic Liquid-Based Corrosion Inhibitor for Steel in Acidic Environments.

PubMed

Atta, Ayman M; El-Mahdy, Gamal A; Al-Lohedan, Hamad A; Ezzat, Abdel Rahman O

2015-06-17

This work examines the use of new hydrophobic ionic liquid derivatives, namely octadecylammonium tosylate (ODA-TS) and oleylammonium tosylate (OA-TS) for corrosion protection of steel in 1 M hydrochloric acid solution. Their chemical structures were determined from NMR analyses. The surface activity characteristics of the prepared ODA-TS and OA-TS were evaluated from conductance, surface tension and contact angle measurements. The data indicate the presence of a double bond in the chemical structure of OA-TS modified its surface activity parameters. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) measurements, scanning electron microscope (SEM), Energy dispersive X-rays (EDX) analysis and contact angle measurements were utilized to investigate the corrosion protection performance of ODA-TS and OA-TS on steel in acidic solution. The OA-TS and ODA-TS compounds showed good protection performance in acidic chloride solution due to formation of an inhibitive film on the steel surface.

Process for derivatizing carbon nanotubes with diazonium species

NASA Technical Reports Server (NTRS)

Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

2007-01-01

The invention incorporates new processes for the chemical modification of carbon nanotubes. Such processes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications and sensor devices. The methods of derivatization include electrochemical induced reactions thermally induced reactions (via in-situ generation of diazonium compounds or pre-formed diazonium compounds), and photochemically induced reactions. The derivatization causes significant changes in the spectroscopic properties of the nanotubes. The estimated degree of functionality is ca. 1 out of every 20 to 30 carbons in a nanotube bearing a functionality moiety. Such electrochemical reduction processes can be adapted to apply site-selective chemical functionalization of nanotubes. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes ##STR00001##.

Emergence of a replicating species from an in vitro RNA evolution reaction

NASA Technical Reports Server (NTRS)

Breaker, R. R.; Joyce, G. F.

1994-01-01

The technique of self-sustained sequence replication allows isothermal amplification of DNA and RNA molecules in vitro. This method relies on the activities of a reverse transcriptase and a DNA-dependent RNA polymerase to amplify specific nucleic acid sequences. We have modified this protocol to allow selective amplification of RNAs that catalyze a particular chemical reaction. During an in vitro RNA evolution experiment employing this modified system, a unique class of "selfish" RNAs emerged and replicated to the exclusion of the intended RNAs. Members of this class of selfish molecules, termed RNA Z, amplify efficiently despite their inability to catalyze the target chemical reaction. Their amplification requires the action of both reverse transcriptase and RNA polymerase and involves the synthesis of both DNA and RNA replication intermediates. The proposed amplification mechanism for RNA Z involves the formation of a DNA hairpin that functions as a template for transcription by RNA polymerase. This arrangement links the two strands of the DNA, resulting in the production of RNA transcripts that contain an embedded RNA polymerase promoter sequence.

Functionalization of multi-walled carbon nanotubes with iron phthalocyanine via a liquid chemical reaction for oxygen reduction in alkaline media

NASA Astrophysics Data System (ADS)

Yan, Xiaomei; Xu, Xiao; Liu, Qin; Guo, Jia; Kang, Longtian; Yao, Jiannian

2018-06-01

Iron single-atom catalyst in form of iron-nitrogen-carbon structure possesses the excellent catalytic activity in various chemical reactions. However, exploring a sustainable and stable single-atom metal catalyst still faces a great challenge due to low yield and complicated synthesis. Here, we report a functional multi-wall carbon nanotubes modified with iron phthalocyanine molecules via a liquid chemical reaction and realize the performance of similar single-atom catalysis for oxygen reduction reaction. A serial of characterizations strongly imply the structure change of iron phthalocyanine molecule and its close recombination with multi-wall carbon nanotubes, which are in favor of ORR catalysis. Compared to commercial platinum-carbon catalyst, composites exhibit superior activity for oxygen reduction reaction with higher half-wave potential (0.86 V), lower Tafel slope (38 mV dec-1), higher limiting current density and excellent electrochemical stability. The corresponding Zinc-air battery also presents higher maximum power density and discharge stability. Therefore, these findings provide a facile route to synthesize a highly efficient non-precious metal carbon-based catalyst.

Marine Rare Actinobacteria: Isolation, Characterization, and Strategies for Harnessing Bioactive Compounds

PubMed Central

Dhakal, Dipesh; Pokhrel, Anaya Raj; Shrestha, Biplav; Sohng, Jae Kyung

2017-01-01

Actinobacteria are prolific producers of thousands of biologically active natural compounds with diverse activities. More than half of these bioactive compounds have been isolated from members belonging to actinobacteria. Recently, rare actinobacteria existing at different environmental settings such as high altitudes, volcanic areas, and marine environment have attracted attention. It has been speculated that physiological or biochemical pressures under such harsh environmental conditions can lead to the production of diversified natural compounds. Hence, marine environment has been focused for the discovery of novel natural products with biological potency. Many novel and promising bioactive compounds with versatile medicinal, industrial, or agricultural uses have been isolated and characterized. The natural compounds cannot be directly used as drug or other purposes, so they are structurally modified and diversified to ameliorate their biological or chemical properties. Versatile synthetic biological tools, metabolic engineering techniques, and chemical synthesis platform can be used to assist such structural modification. This review summarizes the latest studies on marine rare actinobacteria and their natural products with focus on recent approaches for structural and functional diversification of such microbial chemicals for attaining better applications. PMID:28663748

[A computer method for the evaluation of Paramecium motor activity using video records of their movement].

PubMed

Bingi, V N; Zarutskiĭ, A A; Kapranov, S V; Kovalev, Iu M; Miliaev, V A; Tereshchenko, N A

2004-01-01

A method for the evaluation of Paramecium caudatum motility was proposed as a tool for the investigation of magnetobiological as well as other physical and chemical effects. The microscopically observed movement of paramecia is recorded and processed using a special software program. The protozoan motility is determined as a function of their mean velocity in a definite time. The main advantages of the method are that it is easily modified for determining various characteristics of the motor activity of paramecia and that the video data obtained can be reused.

Chemical characteristics and volatile profile of genetically modified peanut cultivars.

PubMed

Ng, Ee Chin; Dunford, Nurhan T; Chenault, Kelly

2008-10-01

Genetic engineering has been used to modify peanut cultivars for improving agronomic performance and pest resistance. Food products developed through genetic engineering have to be assessed for their safety before approval for human consumption. Preservation of desirable chemical, flavor and aroma attributes of the peanut cultivars during the genetic modifications is critical for acceptance of genetically modified peanuts (GMP) by the food industry. Hence, the main objective of this study is to examine chemical characteristics and volatile profile of GMP. The genetically modified peanut cultivars, 188, 540 and 654 were obtained from the USDA-ARS in Stillwater, Oklahoma. The peanut variety Okrun was examined as a control. The volatile analysis was performed using a gas chromatograph/mass spectrometer (GC/MS) equipped with an olfactory detector. The peanut samples were also analyzed for their moisture, ash, protein, sugar and oil compositions. Experimental results showed that the variations in nutritional composition of peanut lines examined in this study were within the values reported for existing cultivars. There were minor differences in volatile profile among the samples. The implication of this study is significant, since it shows that peanut cultivars with greater pest and fungal resistance were successfully developed without major changes in their chemical characteristics.

Magnetorheological finishing of chemical-vapor deposited zinc sulfide via chemically and mechanically modified fluids

DOE PAGES

Salzman, Sivan; Romanofsky, Henry J.; Giannechini, Lucca J.; ...

2016-02-19

In this study, we describe the anisotropy in the material removal rate (MRR) of the polycrystalline, chemical-vapor deposited zinc sulfide (ZnS).We define the polycrystalline anisotropy via microhardness and chemical erosion tests for four crystallographic orientations of ZnS: (100), (110), (111), and (311). Anisotropy in the MRR was studied under magnetorheological finishing (MRF) conditions. Three chemically and mechanically modified magnetorheological (MR) fluids at pH values of 4, 5, and 6 were used to test the MRR variations among the four single-crystal planes. When polishing the single-crystal planes and the polycrystalline with pH 5 and pH 6MR fluids, variations were found inmore » the MRR among the four single-crystal planes and surface artifacts were observed on the polycrystalline material. When polishing the single-crystal planes and the polycrystalline with the modified MR fluid at pH 4, however, minimal variation was observed in the MRR among the four orientations and a reduction in surface artifacts was achieved on the polycrystalline material.« less

Chemical Modification of Waste Cotton Linters for Oil Spill Cleanup Application

NASA Astrophysics Data System (ADS)

Chattopadhyay, Debapriya; Umrigar, Keval

2017-12-01

The possibility of use of waste cotton linters as oil sorbents by chemical modification such as acetylation and cyanoethylation was studied. The acetylation process was carried out in presence of acetic anhydride using either H2SO4 or HClO4 as catalyst. The acetylation treatment time was 30, 60 and 120 min and treatment temperature was room temperature, 50 and 70 °C. For cyanoethylation, the waste cotton linters were pre-treated with 2, 5 and 10% NaOH. The treatment temperature for cyanoethylation was room temperature, 50 and 70 °C and treatment time was 30, 60 and 120 min. Both the chemical modification processes were optimized on the basis of oil absorption capacity of the chemically modified cotton fibre with the help of MATLAB software. The modified samples were tested for its oleophilicity in terms of oil absorption capacity, oil retention capacity, oil recovery capacity, reusability of sample and water uptake and buoyancy as oil sorbent. Chemically modified fibres were characterized by Fourier transform infra red spectrophotometer, scanning electron microscope and degree of substitutions.

Highly efficient temperature-induced visible light photocatalytic hydrogen production

NASA Astrophysics Data System (ADS)

Han, Bing

Photocatalysis is the acceleration of photoreaction in presence of a photocatalyst. Semiconductor photocatalysis has obtained much attention as a potential solution to the worldwide energy storage due to its promising ability to directly convert solar energy into chemical fuels. This dissertation research mainly employ three approaches to enhance photocatalytic activities, which includes (I) Modifying semiconductor nanomaterials for visible and near-IR light absorption; (II) Synthesis of light-diffuse-reflection-surface of SiO2 substrate to utilize scattered light; and (III) design of a hybrid system that combines light and heat to enhance visible light photocatalytic activity. Those approaches were applied to two systems: (1) hydrogen production from water; (2) carbon dioxide reforming of methane. The activity of noble metals such as platinum were investigated as co-catalysts and cheap earth abundant catalysts as alternatives to reduce cost were also developed. Stability, selectivity, mechanism were investigated. Great enhancement of visible light activity over a series of semiconductors/heterostructures were observed. Such extraordinary performance of artificial photosynthetic hydrogen production system would provide a novel approach for the utilization of solar energy for chemical fuel production.

Surface Modified Particles By Multi-Step Michael-Type Addition And Process For The Preparation Thereof

DOEpatents

Cook, Ronald Lee; Elliott, Brian John; Luebben, Silvia DeVito; Myers, Andrew William; Smith, Bryan Matthew

2005-05-03

A new class of surface modified particles and a multi-step Michael-type addition surface modification process for the preparation of the same is provided. The multi-step Michael-type addition surface modification process involves two or more reactions to compatibilize particles with various host systems and/or to provide the particles with particular chemical reactivities. The initial step comprises the attachment of a small organic compound to the surface of the inorganic particle. The subsequent steps attach additional compounds to the previously attached organic compounds through reactive organic linking groups. Specifically, these reactive groups are activated carbon—carbon pi bonds and carbon and non-carbon nucleophiles that react via Michael or Michael-type additions.

Refractory inclusions with unusual chemical compositions from the Vigarano carbonaceous chondrite

NASA Technical Reports Server (NTRS)

Sylvester, Paul J.; Grossman, Lawrence; Macpherson, Glenn J.

1992-01-01

Neutron activation was used to test ten inclusions, nine Vigarano and one from Leoville, for major and trace elements. Six Vigarano refractory inclusions have refractory element fractionations that are rare or absent in Allende inclusions. Vig 1623-11 has Th/La and Ir/Mo ratios that are lower than those of any Allende Group I or modified Group I inclusions, and Os/La, Ir/La, and Zr/Hf ratios that are among the lowest in those inclusions. The low Os/La, Ir/La, and Ir/Mo ratios seem to require nonrepresentative sampling of condensate phase in the nebula to a degree that is usual for Allende Group I and modified group I inclusions. The nature and origins of the different inclusions are discussed.

Modulation of the norfloxacin resistance in Staphylococcus aureus by Cordia verbenaceae DC.

PubMed

Matias, Edinardo F F; Santos, Karla K A; Falcão-Silva, Vivyanne S; Siqueira-Junior, Jose P; Costa, Jose G M; Coutinho, Henrique D M

2013-01-01

Several chemical compounds isolated from natural sources have antibacterial activity and some enhance the antibacterial activity of antibiotics reversing the natural resistance of bacteria to certain antibiotics. In this study, the hexane and methanol extract of Cordia verbenaceae were assessed for antibacterial activity alone and combinated with norfloxacin against the Staphylococcus aureus strain SA1199B. The minimum inhibitory concentration (MIC) of extracts was assayed using microdilution assay and the modulatory activity was evaluated using plate diffusion assay. The MIC observed varied between 256 to >1024 μg/ml. However, the antibiotic activity of norfloxacin was enhanced in the presence of subinhibitory concentrations of hexane extract of C. verbenaceae (HECV). INTERPRETATIONS & CONCLUSIONS: Our results indicate that Cordia verbenaceae DC. can be a source of plant derived products with antibiotic modifying activity.

Enhancement of p-nitrophenol adsorption capacity through N2-thermal-based treatment of activated carbons

NASA Astrophysics Data System (ADS)

Álvarez-Torrellas, S.; Martin-Martinez, M.; Gomes, H. T.; Ovejero, G.; García, J.

2017-08-01

In this work several activated carbons showing different textural and chemical properties were obtained by chemical and physical activation methods, using a lignocellulosic material (peach stones) as precursor. The activated carbon resulting from the chemical activation, namely as CAC, revealed the best textural properties (SBET = 1521 m2 g-1, pore volume = 0.90 cm3 g-1) and an acidic character. It was found that the activated carbon obtained at 300 °C (under air atmosphere, PAC_air), and those synthesized at 750 °C in presence of N2 flow with bubbling of water/12 M H3PO4 solution (PAC_N2(H2O)/PAC_N2(H3PO4)), respectively, revealed worse textural properties, compared to CAC. Two functionalization treatments, by using sulphuric acid at boiling temperature (PACS) and nitric acid-urea-N2 heating at 800 °C (PAC-NUT), were applied to PAC_air, in order to enhance the adsorption ability of the carbon material. Several techniques were carried out to characterize the physical and chemical properties of the obtained carbon materials. The modification treatments had influence on the carbon surface properties, since the nitric acid-urea-N2 heating treatment led to a carbon material with highly-improved properties (SBET = 679 m2 g-1, pHIEP = 5.3). Accordingly, the original and modified-carbon materials were tested as adsorbents to remove 4-nitrophenol (4-NP), assessing batch and fixed-bed column adsorption tests. PAC-NUT carbon offered the best adsorption behavior (qe = 234 mg g-1), showing a high ability for the removal of 4-NP from water.

Utilization and Conversion of Sewage Sludge as Metal Sorbent

NASA Astrophysics Data System (ADS)

Gong, Xu Dong; Li, Loretta Y.

2013-04-01

Most biosolids are disposed on land. With improvements in wastewater treatment processes and upgrading of treatment plants across Canada, biosolids generation will increase dramatically. These biosolids will need to be dealt with because they contain various contaminants, including heavy metals and several classes of emerging contaminants. A number of researchers have recently focused on preparation of sewage sludge-based adsorbents by carbonation, physical activation and chemical activation for decontamination of air and wastewater. These previous studies have indicated that sludge-based activated carbon can have good adsorption performance for organic substances in dye wastewater. The overall results suggest that activated carbon from sewage sludge can produce a useful adsorbent, while also reducing the amount of sewage sludge to be disposed. However, sludge-derived activated carbon has not been extensively studied, especially for adsorption of heavy metal ions in wastewater and for its capacity to remove emerging contaminants, such as poly-fluorinated compounds (PFCs). Previous research has indicated that commercial activated carbons adsorb organic compounds more efficiently than heavy metal ions. 45 Activated carbon can be modified to enhance its adsorption capacity for special heavy metal ions,46 e.g. by addition of inorganic and organic reagents. The modifications which are successful for commercial activated carbon should also be effective for sludge-derived activated carbon, but this needs to be confirmed. Our research focuses on (a) investigation of techniques for converting sewage sludge (SS) to activated carbon (AC) as sorbents; (b) exploration of possible modification of the activated carbon (MAC) to improve its sorption capacity; (c) examination of the chemical stability of the activated carbon and the leachability of contaminants from activated carbon,; (d) comparison of adsorptivity with that of other sorbents. Based on XRD and FT-IR, we successfully converted SS to AC and further modified it to improve absorption. SSMAC has large specific surface areas based on the BET technique. Batch adsorption results indicate that metal adsorption for SSMAC > SSAC, with adsorption occurring within the first 5 minutes of contact. Comparison of the adsorptivity of various sorbents such as commercial activated carbon (CAC), mineral sorbents such as perlite, clinoptilolite and illite indicates that SSMAC × CAC × clinoptilolite > kaolite.

Catalytic decomposition of hydrogen peroxide and 4-chlorophenol in the presence of modified activated carbons.

PubMed

Huang, Hsu-Hui; Lu, Ming-Chun; Chen, Jong-Nan; Lee, Cheng-Te

2003-06-01

The objective of this research was to examine the heterogeneous catalytic decomposition of H(2)O(2) and 4-chlorophenol (4-CP) in the presence of activated carbons modified with chemical pretreatments. The decomposition of H(2)O(2) was suppressed significantly by the change of surface properties including the decreased pH(pzc) modified with oxidizing agent and the reduced active sites occupied by the adsorption of 4-CP. The apparent reaction rate of H(2)O(2) decomposition was dominated by the intrinsic reaction rates on the surface of activated carbon rather than the mass transfer rate of H(2)O(2) to the solid surface. By the detection of chloride ion in suspension, the reduction of 4-CP was not only attributed to the advanced adsorption but also the degradation of 4-CP. The catalytic activity toward 4-CP for the activated carbon followed the inverse sequence of the activity toward H(2)O(2), suggesting that acidic surface functional group could retard the H(2)O(2) loss and reduce the effect of surface scavenging resulting in the increase of the 4-CP degradation efficiency. Few effective radicals were expected to react with 4-CP for the strong effect of surface scavenging, which could explain why the degradation rate of 4-CP observed in this study was so slow and the dechlorination efficiency was independent of the 4-CP concentration in aqueous phase. Results show that the combination of H(2)O(2) and granular activated carbon (GAC) did increase the total removal of 4-CP than that by single GAC adsorption.

Preparation and characterization of copper telluride thin films by modified chemical bath deposition (M-CBD) method

NASA Astrophysics Data System (ADS)

Pathan, H. M.; Lokhande, C. D.; Amalnerkar, D. P.; Seth, T.

2003-09-01

Copper telluride thin films were deposited using modified chemical method using copper(II) sulphate; pentahydrate [CuSO 4·5H 2O] and sodium tellurite [Na 2TeO 3] as cationic and anionic sources, respectively. Modified chemical method is based on the immersion of the substrate into separately placed cationic and anionic precursors. The preparative conditions such as concentration, pH, immersion time, immersion cycles, etc. were optimized to get good quality copper telluride thin films at room temperature. The films have been characterized for structural, compositional, optical and electrical transport properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Rutherford back scattering (RBS), optical absorption/transmission, electrical resistivity and thermoemf measurement techniques.

Phosphoethanolamine cellulose: A naturally produced chemically modified cellulose.

PubMed

Thongsomboon, Wiriya; Serra, Diego O; Possling, Alexandra; Hadjineophytou, Chris; Hengge, Regine; Cegelski, Lynette

2018-01-19

Cellulose is a major contributor to the chemical and mechanical properties of plants and assumes structural roles in bacterial communities termed biofilms. We find that Escherichia coli produces chemically modified cellulose that is required for extracellular matrix assembly and biofilm architecture. Solid-state nuclear magnetic resonance spectroscopy of the intact and insoluble material elucidates the zwitterionic phosphoethanolamine modification that had evaded detection by conventional methods. Installation of the phosphoethanolamine group requires BcsG, a proposed phosphoethanolamine transferase, with biofilm-promoting cyclic diguanylate monophosphate input through a BcsE-BcsF-BcsG transmembrane signaling pathway. The bcsEFG operon is present in many bacteria, including Salmonella species, that also produce the modified cellulose. The discovery of phosphoethanolamine cellulose and the genetic and molecular basis for its production offers opportunities to modulate its production in bacteria and inspires efforts to biosynthetically engineer alternatively modified cellulosic materials. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Surface Chemical Conversion of Organosilane Self-Assembled Monolayers with Active Oxygen Species Generated by Vacuum Ultraviolet Irradiation of Atmospheric Oxygen Molecules

NASA Astrophysics Data System (ADS)

Kim, Young-Jong; Lee, Kyung-Hwang; Sano, Hikaru; Han, Jiwon; Ichii, Takashi; Murase, Kuniaki; Sugimura, Hiroyuki

2008-01-01

The chemical conversion of the top surface of n-octadecyltrimethoxy silane self-assembled monolayers (ODS-SAMs) on oxide-covered Si substrates using active oxygen species generated from atmospheric oxygen molecules irradiated with vacuum ultraviolet (VUV) light at 172 nm in wavelength has been studied on the basis of water contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy. An ODS-SAM whose water contact angle was 104° on average was prepared using chemical vapor deposition with substrate and vapor temperatures of 150 °C. The VUV treatment of an ODS-SAM sample was carried out by placing the sample in air and then irradiating the sample surface with a Xe-excimer lamp. The distance between the lamp and the sample was regulated so that the VUV light emitted from the lamp was almost entirely absorbed by atmospheric oxygen molecules to generate active oxygen species, such as ozone and atomic oxygen before reaching the sample surface. Hence, the surface chemical conversion of the ODS-SAM was primarily promoted through chemical reactions with the active oxygen species. Photochemical changes in the ODS-SAM were found to be the generation of polar functional groups, such as -COOH, -CHO, and -OH, on the surface and the subsequent etching of the monolayer. Irradiation parameters, such as irradiation time, were optimized to achieve a better functionalization of the SAM top surface while minimizing the etching depth of the ODS-SAM. The ability to graft another SAM onto the modified ODS-SAM bearing polar functional groups was demonstrated by the formation of alkylsilane bilayers.

The bioavailability of chemicals in soil for earthworms

USGS Publications Warehouse

Lanno, R.; Wells, J.; Conder, Jason M.; Bradham, K.; Basta, N.

2004-01-01

The bioavailability of chemicals to earthworms can be modified dramatically by soil physical/chemical characteristics, yet expressing exposure as total chemical concentrations does not address this problem. In order to understand the effects of modifying factors on bioavailability, one must measure and express chemical bioavailability to earthworms in a consistent, logical manner. This can be accomplished by direct biological measures of bioavailability (e.g., bioaccumulation, critical body residues), indirect biological measures of bioavailability (e.g., biomarkers, reproduction), or indirect chemical measures of bioavailability (e.g., chemical or solid-phase extracts of soil). If indirect chemical measures of bioavailability are to be used, they must be correlated with some biological response. Bioavailability can be incorporated into ecological risk assessment during risk analysis, primarily in the estimation of exposure. However, in order to be used in the site-specific ecological risk assessment of chemicals, effects concentrations must be developed from laboratory toxicity tests based on exposure estimates utilizing techniques that measure the bioavailable fraction of chemicals in soil, not total chemical concentrations. ?? 2003 Elsevier Inc. All rights reserved.

Preparation and characterization of soy protein films with a durable water resistance-adjustable and antimicrobial surface.

PubMed

Li, Shuzhao; Donner, Elizabeth; Xiao, Huining; Thompson, Michael; Zhang, Yachuan; Rempel, Curtis; Liu, Qiang

2016-12-01

A water resistant surface was first obtained by immobilizing hydrophobic copolymers, poly (styrene-co-glycidyl methacrylate) (PSG), with functional groups on soy protein isolate (SPI) films. XPS and AFM results showed that PSG copolymers were immobilized on the film by chemical bonding, and formed a rough surface with some bumps because of the segregation of two different phases on PSG copolymers. Water resistance of the modified films could be adjusted dramatically by further immobilizing different amounts of guanidine-based antimicrobial polymers, poly (hexamethylene guanidine hydrochloride) (PHMG) on the resulting hydrophobic surface. The introduction of hydrophilic PHMG on the resulting surface generated many micropores, which potentially increased the water uptake of the modified films. Furthermore, the modified SPI films showed higher thermostability compared to native SPI film and broad-spectrum antimicrobial activity by contact killing, attributed to the presence of PHMG on the surface. The modified SPI film with a multi-functional surface showed potential for applications in the packaging and medical fields. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Targeted Delivery of Hyaluronan-Immobilized Magnetic Ceramic Nanocrystals.

PubMed

Wu, Hsi-Chin; Wang, Tzu-Wei; Hsieh, Shun-Yu; Sun, Jui-Sheng; Kang, Pei-Leun

2016-01-01

Effective cancer therapy relies on delivering the therapeutic agent precisely to the target site to improve the treatment outcome and to minimize side effects. Although surgery, chemotherapy, and radiotherapy are the standard methods commonly used in clinics, hyperthermia has been developed as a new and promising strategy for cancer therapy. In this study, magnetic bioceramic hydroxyapatite (mHAP) nanocrystals have been developed as heat mediator for intracellular hyperthermia. Hyaluronic acid (HA) modified mHAP nanocrystals are synthesized by a wet chemical precipitation process to achieve active targeting. The results demonstrate that the HA targeting moiety conjugated by a poly(ethylene glycol) (PEG) spacer arm is successfully immobilized on the surface of mHAP. The HA-modified mHAP possesses relatively good biocompatibility, an adequate biodegradation rate and superparamagnetic properties. The HA-modified mHAP could be localized and internalized into HA receptor-overexpressed malignant cells (e.g., MDA-MB-231 cell) and used as the heat generating agent for intracellular hyperthermia. The results from this study indicate that biocompatible HA-modified mHAP shows promise as a novel heat mediator and a specific targeting nanoagent for intracellular hyperthermia cancer therapy.

Investigation of gas surface interactions at self-assembled silicon surfaces acting as gas sensors

NASA Astrophysics Data System (ADS)

Narducci, Dario; Bernardinello, Patrizia; Oldani, Matteo

2003-05-01

This paper reports the results of an investigation aimed at using self-assembled monolayers to modify the supramolecular interactions between Si surfaces and gaseous molecules. The specific goal is that of employing molecularly imprinted silicon surfaces to develop a new class of chemical sensors capable to detect species with enhanced selectivity. Single-crystal p-type (0 0 1) silicon has been modified by grafting organic molecules onto its surface by using wet chemistry synthetic methods. Silicon has been activated toward nucleophilic attack by brominating its surface using a modified version of the purple etch, and aromatic fragments have been bonded through the formation of direct Si-C bonds onto it using Grignard reagents or lithium aryl species. Formation of self-assembled monolayers (SAMs) was verified by using vibrational spectroscopy. Porous metal-SAM-Si diodes have been successfully tested as resistive chemical sensors toward NO x, SO x, CO, NH 3 and methane. Current-voltage characteristics measured at different gas compositions showed that the mechanism of surface electron density modulation involves a modification of the junction barrier height upon gas adsorption. Quantum-mechanical simulations of the interaction mechanism were carried out using different computational methods to support such an interaction mechanism. The results obtained appear to open up new relevant applications of the SAM techniques in the area of gas sensing.

Development of functional biointerfaces by surface modification of polydimethylsiloxane with bioactive chlorogenic acid.

PubMed

Wu, Ming; He, Jia; Ren, Xiao; Cai, Wen-Sheng; Fang, Yong-Chun; Feng, Xi-Zeng

2014-04-01

The effect of physicochemical surface properties and chemical structure on the attachment and viability of bacteria and mammalian cells has been extensively studied for the development of biologically relevant applications. In this study, we report a new approach that uses chlorogenic acid (CA) to modify the surface wettability, anti-bacterial activity and cell adhesion properties of polydimethylsiloxane (PDMS). The chemical structure of the surface was obtained by X-ray photoelectron spectroscopy (XPS), the roughness was measured by atomic force microscopy (AFM), and the water contact angle was evaluated for PDMS substrates both before and after CA modification. Molecular modelling showed that the modification was predominately driven by van der Waals and electrostatic interactions. The exposed quinic-acid moiety improved the hydrophilicity of CA-modified PDMS substrates. The adhesion and viability of E. coli and HeLa cells were investigated using fluorescence and phase contrast microscopy. Few viable bacterial cells were found on CA-coated PDMS surfaces compared with unmodified PDMS surfaces. Moreover, HeLa cells exhibited enhanced adhesion and increased spreading on the modified PDMS surface. Thus, CA-coated PDMS surfaces reduced the ratio of viable bacterial cells and increased the adhesion of HeLa cells. These results contribute to the purposeful design of anti-bacterial surfaces for medical device use. Copyright © 2013 Elsevier B.V. All rights reserved.

Activated Carbon Preparation and Modification for Adsorption

NASA Astrophysics Data System (ADS)

Cao, Yuhe

Butanol is considered a promising, infrastructure-compatible biofuel. Butanol has a higher energy content than ethanol and can be used in conventional gas engines without modifications. Unfortunately, the fermentation pathway for butanol production is restricted by its toxicity to the microbial strains used in the process. Butanol is toxic to the microbes, and this can slow fermentation rates and reduce butanol yields. Gas stripping technology can efficiently remove butanol from the fermentation broth as it is produced, thereby decreasing its inhibitory effects. Traditional butanol separation heavily depends on the energy intensive distillation method. One of the main issues in acetone-butanol-ethanol fermentation is that butanol concentrations in the fermentation broth are low, ranging from 1 to 1.2 percent in weight, because of its toxicity to the microorganisms. Therefore distillation of butanol is even worse than distillation of corn ethanol. Even new separation methods, such as solid- extraction methods involve adding substances, such as polymer resin and zeolite or activated carbon, to biobutanol fermentatioon broth did not achieve energy efficient separation of butanol due to low adsorption selectivity and fouling in broth. Gas-stripping - condensation is another new butanol recovery method, however, the butanol in gas-stripping stream is too low to be condensed without using expensive and energy intensive liquid nitrogen. Adsorption can then be used to recover butanol from the vapor phase. Activated carbon (AC) samples and zeolite were investigated for their butanol vapor adsorption capacities. Commercial activated carbon was modified via hydrothermal H2O2 treatment, and the specific surface area and oxygen-containing functional groups of activated carbon were tested before and after treatment. Hydrothermal H2O 2 modification increased the surface oxygen content, Brunauer-Emmett-Teller surface area, micropore volume, and total pore volume of active carbon. The adsorption capacities of these active carbon samples were almost three times that of zeolite. However, the un-modified active carbon had the highest adsorption capacity for butanol vapor (259.6 mg g-1), compared to 222.4 mg g-1 after 10% H2O2 hydrothermal treatment. Both modified and un-modified active carbon can be easily regenerated for repeatable adsorption by heating to 150 °C. Therefore, surface oxygen groups significantly reduced the adsorption capacity of active carbons for butanol vapor. In addition, original active carbon and AC samples modified by nitric acid hydrothermal modification were assessed for their ability to adsorb butanol vapor. The specific surface area and oxygen-containing functional groups of AC were tested before and after modification. The adsorption capacity of unmodified AC samples were the highest. Hydrothermal oxidation of AC with HNO3 increased the surface oxygen content, Brunauer-Emmett-Teller (BET) surface area, micropore, mesopore and total pore volume of AC. Although the pore structure and specific surface area were greatly improved after hydrothermal oxidization with 4 M HNO3, the increased oxygen on the surface of AC decreased the dynamic adsorption capacity. In order to get high adsorption capacity adsorbents, we used corn stalk as precursor to fabricate porous carbon. ACs were prepared through chemical activation of biochar from whole corn stalk (WCS) and corn stalk pith (CSP) at varying temperatures using potassium hydroxide as the activating agent. ACs were characterized via pore structural analysis and scanning electron microscopy (SEM). These adsorbents were then assessed for their adsorption capacity for butanol vapor. It was found that WCS activated at 900 °C for 1 h (WCS-900) had optimal butanol adsorption characteristics. The BET surface area and total pore volume of the WCS-900 were 2330 m2 g-1 and 1.29 cm3 g-1, respectively. The dynamic adsorption capacity of butanol vapor was 410.0 mg g-1, a 185.1 % increase compared to charcoal-based commercial AC (143.8 mg g -1). Based on the adsorption experiments of butanol vapor, we found the chemical properties of the AC surface play an important role in adsorbing molecules. The adsorption of creatinine on active carbons was also studied, which is a toxic compound generated by human. High levels of creatinine in the blood stream is normally caused by malfunction or failure of the kidneys. Activated carbons is taken by the patients orally to reduce creatinine level. In order to figure out whether chemical modification could increase the adsorption capacity of creatinine, AC samples modified by nitric acid hydrothermal modification were assessed for their ability to adsorb creatinine. The pore structure and surface properties of the AC samples were characterized by N 2 adsorption, temperature programmed desorption (TPD), Fourier Transform Infrared spectroscopy (FTIR), and X-ray photoelectron spectrometer (XPS). It indicated that 4M HNO3 hydrothermal modification with 180 °C was an efficient method in improvement of the creatinine adsorption. The improved adsorption capacity can be attributed mainly to an increase in the acidic oxygen-containing functional groups. The adsorption of creatinine over AC may involve an interaction with the acidic oxygen-containing groups on AC. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherm and isotherm constants. Equilibrium data fitted very well to the Freundlich model in the entire saturation range (3.58-59.08 mg L-1 ). The maximum adsorption capacities of AC modified with 180 °C is 62.5 mg g-1 according to the Langmuir model. Pseudo first-order and second-order kinetic models were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted well to the second-order kinetic model, which indicates that the chemical adsorption was the rate-limiting step, instead of mass transfer. (Abstract shortened by ProQuest.).

Development of a Theoretical Model to Assess the Hepatocarcinogenic Potential of Chemicals Using Structure-Activity Relationships and the Rat Hepatocyte Assay

DTIC Science & Technology

1985-11-01

Kappus ,19a5; Tyson and Green, in press). When ethane evolution was quantitated, the experimental conditions were modified to maximize sensitivity, as...commonly used and convenient technique for tVat purpose ( Kappus , 1985). Since MDA, the lipid breakdown product that the TBA reaction primarily...cytcchrome P-450(c) reductase. Mol. Pharmacol. 20, 669-673 (1981). Kappus , H. (1985). Lipid peroxidatioa: mechanisms, analysis, enzymology and

Novel chitosan derivative for the removal of cadmium in the presence of cyanide from electroplating wastewater.

PubMed

Sankararamakrishnan, Nalini; Sharma, Ajit Kumar; Sanghi, Rashmi

2007-09-05

Chitosan was chemically modified by introducing xanthate group onto its backbone using carbondisulfide under alkaline conditions. The chemically modified chitosan flakes (CMC) was used as an adsorbent for the removal of cadmium ions from electroplating waste effluent under laboratory conditions. CMC was found to be far more efficient than the conventionally used adsorbent activated carbon. The maximum uptake of cadmium by CMC in batch studies was found to be 357.14 mg/g at an optimum pH of 8.0 whereas for plain chitosan flakes it was 85.47 mg/g. Since electroplating wastewater contains cyanide in appreciable concentrations, interference of cyanide ions in cadmium adsorption was found to be very significant. This problem could be easily overcome by using higher doses of CMC, however, activated carbon was not found to be effective even at higher doses. Due to the high formation constant of cadmium with xanthate and adsorption was carried out at pH 8, cations like Pb(II), Cu(II), Ni(II) and Zn(II) did not interfere in the adsorption. Dynamics of the sorption process were studied and the values of rate constant of adsorption were calculated. Desorption of the bound cadmium from CMC was accomplished with 0.01 N H(2)SO(4). The data from regeneration efficiencies for 10 cycles evidenced the reusability of CMC in the treatment of cadmium-laden wastewater.

Tailored functionalization of iron oxide nanoparticles for MRI, drug delivery, magnetic separation and immobilization of biosubstances.

PubMed

Hola, Katerina; Markova, Zdenka; Zoppellaro, Giorgio; Tucek, Jiri; Zboril, Radek

2015-11-01

In this critical review, we outline various covalent and non-covalent approaches for the functionalization of iron oxide nanoparticles (IONPs). Tuning the surface chemistry and design of magnetic nanoparticles are described in relation to their applicability in advanced medical technologies and biotechnologies including magnetic resonance imaging (MRI) contrast agents, targeted drug delivery, magnetic separations and immobilizations of proteins, enzymes, antibodies, targeting agents and other biosubstances. We review synthetic strategies for the controlled preparation of IONPs modified with frequently used functional groups including amine, carboxyl and hydroxyl groups as well as the preparation of IONPs functionalized with other species, e.g., epoxy, thiol, alkane, azide, and alkyne groups. Three main coupling strategies for linking IONPs with active agents are presented: (i) chemical modification of amine groups on the surface of IONPs, (ii) chemical modification of bioactive substances (e.g. with fluorescent dyes), and (iii) the activation of carboxyl groups mainly for enzyme immobilization. Applications for drug delivery using click chemistry linking or biodegradable bonds are compared to non-covalent methods based on polymer modified condensed magnetic nanoclusters. Among many challenges, we highlight the specific surface engineering allowing both therapeutic and diagnostic applications (theranostics) of IONPs and magnetic/metallic hybrid nanostructures possessing a huge potential in biocatalysis, green chemistry, magnetic bioseparations and bioimaging. Copyright © 2015 Elsevier Inc. All rights reserved.

Rocket effluent: Its ice nucleation activity and related properties

NASA Technical Reports Server (NTRS)

Parungo, F. P.; Allee, P. A.

1978-01-01

To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei and modify local weather in suitable meteorological conditions.

Role of graphene on the surface chemical reactions of BiPO4-rGO with low OH-related defects.

PubMed

Gao, Erping; Wang, Wenzhong

2013-11-21

Graphene has been widely introduced into photocatalysis to enhance photocatalytic performance due to its unique physical and chemical properties. However, the effect of graphene on the surface chemical reactions of photocatalysis has not been clearly researched, which is important for photocatalysis because photocatalytic reactions ultimately occur on the catalyst surface. Herein, a two-step solution-phase reaction has been designed to synthesize quasi-core-shell structured BiPO4-rGO cuboids and the role of graphene on the surface chemical reactions was investigated in detail. It was found that the introduced graphene modified the process and the mechanism of the surface chemical reactions. The change mainly originates from the interaction between graphene and the adsorbed O2 molecule. Due to the electron transfer from graphene to adsorbed O2, graphene could tune the interfacial charge transport and efficiently activate molecular oxygen to form O2˙(-) anions as the major oxidation species instead of ˙OH. In addition, the two-step synthesis approach could efficiently suppress the formation of OH-related defects in the lattice. As a result, the BiPO4-rGO composite exhibited superior photocatalytic activity to BiPO4 and P25, about 4.3 times that of BiPO4 and 6.9 times that of P25.

Highly Modified Cellulose Nanocrystals and Formation of Epoxy-CNC Nanocomposites.

PubMed

Abraham, Eldho; Kam, Doron; Nevo, Yuval; Slattegard, Rikard; Rivkin, Amit; Lapidot, Shaul; Shoseyov, Oded

2016-10-05

This work presents an environmentally friendly, iodine-catalysed chemical modification method to generate highly hydrophobic, optically active cellulose nanocrystals (CNC). The high degree of ester substitution (DS=2.18), hydrophobicity, crystalline behaviour and optical activity of the generated acetylated CNC (Ac-CNC) were quantified by TEM, FTIR, solid 13C NMR, contact angle, XRD and POM analyses. Ac-CNC possessing substantial enhancement in thermal stability (16.8%) and forms thin films with interlayer distance of 50-150 nm, presenting cavities suitable for entrapping nano and micro particles. Generated Ac-CNC proved as an effective reinforcing agent in hydrophobic polymer matrices for fabricating high performance nanocomposites. When integrated at a very low weight percentage (0.5%) in an epoxy matrix, Ac-CNC provided for a 73% increase in tensile strength and a 98% increase in modulus, demonstrating its remarkable reinforcing potential and effective stress transfer behaviour. The method of modification and the unique properties of the modified CNC (hydrophobicity, crystallinity, reinforcing ability and optical activity) render them a novel bionanomaterial for a range of multipurpose applications.

Inter-laboratory validation of the modified murine local lymph node assay based on 5-bromo-2'-deoxyuridine incorporation.

PubMed

Kojima, Hajime; Takeyoshi, Masahiro; Sozu, Takashi; Awogi, Takumi; Arima, Kazunori; Idehara, Kenji; Ikarashi, Yoshiaki; Kanazawa, Yukiko; Maki, Eiji; Omori, Takashi; Yuasa, Atsuko; Yoshimura, Isao

2011-01-01

The murine local lymph node assay (LLNA) is a well-established alternative to the guinea pig maximization test (GPMT) or Buehler test (BT) for the assessment of the skin sensitizing ability of a drug, cosmetic material, pesticide or industrial chemical. Instead of radioisotope using in this method, Takeyoshi M. et al. (2001) has developed a modified LLNA based on the 5-bromo-2'-deoxyuridine (BrdU) incorporation (LLNA:BrdU-ELISA). The LLNA:BrdU-ELISA is practically identical to the LLNA methodology excluding the use of BrdU, for which a single intraperitoneal injection of BrdU is made on day 4, and colorimetric detection of cell turnover. We conducted the validation study to evaluate the reliability and relevance of LLNA:BrdU-ELISA. The experiment involved 7 laboratories, wherein 10 chemicals were examined under blinded conditions. In this study, 3 chemicals were examined in all laboratories and the remaining 7 were examined in 3 laboratories. The data were expressed as the BrdU incorporation using an ELISA method for each group, and the stimulation index (SI) for each chemical-treated group was determined as the increase in the BrdU incorporation relative to the concurrent vehicle control group. An SI of 2 was set as the cut-off value for exhibiting skin sensitization activity. The results obtained in the experiments conducted for all 10 chemicals were sufficiently consistent with small variations in their SI values. The sensitivity, specificity, and accuracy of LLNA:BrdU-ELISA against those of GPMT/BT were 7/7 (100%), 3/3 (100%), and 10/10 (100%), respectively. Copyright © 2010 John Wiley & Sons, Ltd.

Effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds using a modified QSAR model.

PubMed

Lim, Seung Joo; Fox, Peter

2014-02-01

The effects of halogenated aromatics/aliphatics and nitrogen(N)-heterocyclic aromatics on estimating the persistence of future pharmaceutical compounds were investigated using a modified half life equation. The potential future pharmaceutical compounds investigated were approximately 2000 pharmaceutical drugs currently undergoing the United States Food and Drug Administration (US FDA) testing. EPI Suite (BIOWIN) model estimates the fates of compounds based on the biodegradability under aerobic conditions. While BIOWIN considered the biodegradability of a compound only, the half life equation used in this study was modified by biodegradability, sorption and cometabolic oxidation. It was possible that the potential future pharmaceutical compounds were more accurately estimated using the modified half life equation. The modified half life equation considered sorption and cometabolic oxidation of halogenated aromatic/aliphatics and nitrogen(N)-heterocyclic aromatics in the sub-surface, while EPI Suite (BIOWIN) did not. Halogenated aliphatics in chemicals were more persistent than halogenated aromatics in the sub-surface. In addition, in the sub-surface environment, the fates of organic chemicals were much more affected by halogenation in chemicals than by nitrogen(N)-heterocyclic aromatics. © 2013.

Influence of grain activation conditions on functional characteristics of brown rice flour.

PubMed

Singh, Arashdeep; Sharma, Savita; Singh, Baljit

2017-09-01

Grain activation is a natural processing technique that can be used to produce modified flours without chemical modification. Functional characteristics of brown rice flour as influenced by grain activation time and temperatures were investigated. Germination temperatures at 25 ℃, 30 ℃ and 35 ℃ and time for 12, 24, 36 and 48 h significantly influenced the functional properties of flour with modification of starch, protein and high enzymatic activity. Significant decrease in the bulk density, water absorption and swelling power of brown rice flour was observed in comparison to non-germinated flour. Gel consistency and oil absorption capacity of brown rice flour increased as the grain activation time and temperature were increased. Native flour had lowest emulsion and foaming properties, while increase in grain activation time and temperature enhanced the emulsifying and foaming properties of flour. Paste clarity of native flour was 54% which was reduced to 25.17%; however, increase in germination time and temperature increased the % synersis values of germinated flour. Native flour had least gelation concentration of 12% which increased to 25% after 48 h of germination at 35 ℃. Overall, germination can be used as a natural way to modify the functional properties of brown rice flours for their utilization in variety food products.

A bleached-kraft mill effluent fraction causing induction of a fish mixed-function oxygenase enzyme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burnison, B.K.; Hodson, P.V.; Nuttley, D.J.

1996-09-01

Pulp mill effluents contain a myriad of chemicals that have the potential to cause deleterious effects on aquatic biota in receiving waters. Some of these chemicals evoke an acute lethal response of exposed biota while others evoke sublethal responses. One such sublethal response is the induction of mixed-function oxygenases (MFO) in fish, specifically the CYP1A1 enzyme ethoxy-resorufin-o-deethylase (EROD). Compounds causing MFO induction include congeners of polychlorinated biphenyls (PCBs), dioxins, furans, and polycyclic aromatic hydrocarbons (PAHs). The authors followed the partitioning of the inducing chemicals in pulp mill effluent fractions by Toxicity Identification Evaluation (TIE), or bioassay-driven chemical analysis. This proceduremore » was eventually modified to a more direct technique involving centrifugation, filtration, cleanup procedures, and C{sub 18} solid-phase adsorption. The extracts from the fractionation of two pulp mill effluents after secondary treatment were tested for EROD-inducing activity in a 4-d rainbow trout bioassay. The methanol extracts of particulates/colloids showed significant inducing capacity in Mill A effluent but not in Mill B effluent. The C{sub 18} methanol extracts induced activity from both effluents, with extracts from Mill A causing the greatest response. The particulate/colloidal extract (Mill A) was used as the source material for chemicals which caused EROD induction. The fraction was purified by solid-phase extraction techniques and reverse-phase high-performance liquid chromatography. The majority of the EROD activity was found in the moderately nonpolar region of the chromatogram (K{sub ow} = 4.6 to 5.1).« less

Balancing the Hydrogen Evolution Reaction, Surface Energetics, and Stability of Metallic MoS2 Nanosheets via Covalent Functionalization.

PubMed

Benson, Eric E; Zhang, Hanyu; Schuman, Samuel A; Nanayakkara, Sanjini U; Bronstein, Noah D; Ferrere, Suzanne; Blackburn, Jeffrey L; Miller, Elisa M

2018-01-10

We modify the fundamental electronic properties of metallic (1T phase) nanosheets of molybdenum disulfide (MoS 2 ) through covalent chemical functionalization, and thereby directly influence the kinetics of the hydrogen evolution reaction (HER), surface energetics, and stability. Chemically exfoliated, metallic MoS 2 nanosheets are functionalized with organic phenyl rings containing electron donating or withdrawing groups. We find that MoS 2 functionalized with the most electron donating functional group (p-(CH 3 CH 2 ) 2 NPh-MoS 2 ) is the most efficient catalyst for HER in this series, with initial activity that is slightly worse compared to the pristine metallic phase of MoS 2 . The p-(CH 3 CH 2 ) 2 NPh-MoS 2 is more stable than unfunctionalized metallic MoS 2 and outperforms unfunctionalized metallic MoS 2 for continuous H 2 evolution within 10 min under the same conditions. With regards to the entire studied series, the overpotential and Tafel slope for catalytic HER are both directly correlated with the electron donating strength of the functional group. The results are consistent with a mechanism involving ground-state electron donation or withdrawal to/from the MoS 2 nanosheets, which modifies the electron transfer kinetics and catalytic activity of the MoS 2 nanosheet. The functional groups preserve the metallic nature of the MoS 2 nanosheets, inhibiting conversion to the thermodynamically stable semiconducting state (2H) when mildly annealed in a nitrogen atmosphere. We propose that the electron density and, therefore, reactivity of the MoS 2 nanosheets are controlled by the attached functional groups. Functionalizing nanosheets of MoS 2 and other transition metal dichalcogenides provides a synthetic chemical route for controlling the electronic properties and stability within the traditionally thermally unstable metallic state.

Integration of antimicrobial pectin-based edible coating and active modified atmosphere packaging to preserve the quality and microbial safety of fresh-cut persimmon (Diospyros kaki Thunb. cv. Rojo Brillante).

PubMed

Sanchís, Elena; Ghidelli, Christian; Sheth, Chirag C; Mateos, Milagros; Palou, Lluís; Pérez-Gago, María B

2017-01-01

The greatest hurdle to the commercial marketing of fresh-cut fruits is related to their higher susceptibility to enzymatic browning, tissue softening, and microbial growth. The aim of this study was to test the efficacy of a pectin-based edible coating and low oxygen modified atmosphere packaging (MAP) to control enzymatic browning and reduce microbial growth of fresh-cut 'Rojo Brillante' persimmon. The survival of Escherichia coli, Salmonella enteritidis and Listeria monocytogenes artificially inoculated on fresh-cut fruit was also assessed. The pectin coating was amended with 500 IU mL -1 nisin (NI) as antimicrobial agent and 10 g kg -1 citric acid and 10 g kg -1 calcium chloride as anti-browning and firming agents, respectively. Persimmon slices were dipped in the coating or in water (control) and packed under 5 kPa O 2 (MAP) or in ambient atmosphere for up to 9 days at 5 °C. Microbial growth, package gas composition, colour, firmness, polyphenol oxidase activity, visual quality and overall sensory flavour of persimmon slices were measured during storage. Coating application combined with active MAP significantly reduced the CO 2 emission and O 2 consumption in the package. The coating was effective in reducing browning and also inhibited the growth of mesophilic aerobic bacteria. Coating also reduced the populations of E. coli, S. enteritidis and L. monocytogenes. The combination of the pectin-based edible coating and active MAP proved to be the most effective treatment to maintain the sensory and microbiological quality of persimmon slices for more than 9 days of storage. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

A Chemically Modified Curcumin (CMC 2.24) Inhibits Nuclear Factor κB Activation and Inflammatory Bone Loss in Murine Models of LPS-Induced Experimental Periodontitis and Diabetes-Associated Natural Periodontitis.

PubMed

Elburki, Muna S; Rossa, Carlos; Guimarães-Stabili, Morgana R; Lee, Hsi-Ming; Curylofo-Zotti, Fabiana A; Johnson, Francis; Golub, Lorne M

2017-08-01

The purpose of this study was to assess the effect of a novel chemically modified curcumin (CMC 2.24) on NF-κB and MAPK signaling and inflammatory cytokine production in two experimental models of periodontal disease in rats. Experimental model I: Periodontitis was induced by repeated injections of LPS into the gingiva (3×/week, 3 weeks); control rats received vehicle injections. CMC 2.24, or the vehicle, was administered by daily oral gavage for 4 weeks. Experimental model II: Diabetes was induced in adult male rats by streptozotocin injection; periodontal breakdown then results as a complication of uncontrolled hyperglycemia. Non-diabetic rats served as controls. CMC 2.24, or the vehicle, was administered by oral gavage daily for 3 weeks to the diabetics. Hemimaxillae and gingival tissues were harvested, and bone loss was assessed radiographically. Gingival tissues were pooled according to the experimental conditions and processed for the analysis of matrix metalloproteinases (MMPs) and bone-resorptive cytokines. Activation of p38 MAPK and NF-κB signaling pathways was assessed by western blot. Both LPS and diabetes induced an inflammatory process in the gingival tissues associated with excessive alveolar bone resorption and increased activation of p65 (NF-κB) and p38 MAPK. In both models, the administration of CMC 2.24 produced a marked reduction of inflammatory cytokines and MMPs in the gingival tissues, decreased bone loss, and decreased activation of p65 (NF-κB) and p38 MAPK. Inhibition of these cell signaling pathways by this novel tri-ketonic curcuminoid (natural curcumin is di-ketonic) may play a role in its therapeutic efficacy in locally and systemically associated periodontitis.

Highly selective hydrogenation of arenes using nanostructured ruthenium catalysts modified with a carbon–nitrogen matrix

PubMed Central

Cui, Xinjiang; Surkus, Annette-Enrica; Junge, Kathrin; Topf, Christoph; Radnik, Jörg; Kreyenschulte, Carsten; Beller, Matthias

2016-01-01

Selective hydrogenations of (hetero)arenes represent essential processes in the chemical industry, especially for the production of polymer intermediates and a multitude of fine chemicals. Herein, we describe a new type of well-dispersed Ru nanoparticles supported on a nitrogen-doped carbon material obtained from ruthenium chloride and dicyanamide in a facile and scalable method. These novel catalysts are stable and display both excellent activity and selectivity in the hydrogenation of aromatic ethers, phenols as well as other functionalized substrates to the corresponding alicyclic reaction products. Furthermore, reduction of the aromatic core is preferred over hydrogenolysis of the C–O bond in the case of ether substrates. The selective hydrogenation of biomass-derived arenes, such as lignin building blocks, plays a pivotal role in the exploitation of novel sustainable feedstocks for chemical production and represents a notoriously difficult transformation up to now. PMID:27113087

Lanthipeptides: chemical synthesis versus in vivo biosynthesis as tools for pharmaceutical production.

PubMed

Ongey, Elvis Legala; Neubauer, Peter

2016-06-07

Lanthipeptides (also called lantibiotics for those with antibacterial activities) are ribosomally synthesized post-translationally modified peptides having thioether cross-linked amino acids, lanthionines, as a structural element. Lanthipeptides have conceivable potentials to be used as therapeutics, however, the lack of stable, high-yield, well-characterized processes for their sustainable production limit their availability for clinical studies and further pharmaceutical commercialization. Though many reviews have discussed the various techniques that are currently employed to produce lanthipeptides, a direct comparison between these methods to assess industrial applicability has not yet been described. In this review we provide a synoptic comparison of research efforts on total synthesis and in vivo biosynthesis aimed at fostering lanthipeptides production. We further examine current applications and propose measures to enhance product yields. Owing to their elaborate chemical structures, chemical synthesis of these biomolecules is economically less feasible for large-scale applications, and hence biological production seems to be the only realistic alternative.

Spatial control of chemical processes on nanostructures through nano-localized water heating.

PubMed

Jack, Calum; Karimullah, Affar S; Tullius, Ryan; Khorashad, Larousse Khosravi; Rodier, Marion; Fitzpatrick, Brian; Barron, Laurence D; Gadegaard, Nikolaj; Lapthorn, Adrian J; Rotello, Vincent M; Cooke, Graeme; Govorov, Alexander O; Kadodwala, Malcolm

2016-03-10

Optimal performance of nanophotonic devices, including sensors and solar cells, requires maximizing the interaction between light and matter. This efficiency is optimized when active moieties are localized in areas where electromagnetic (EM) fields are confined. Confinement of matter in these 'hotspots' has previously been accomplished through inefficient 'top-down' methods. Here we report a rapid 'bottom-up' approach to functionalize selective regions of plasmonic nanostructures that uses nano-localized heating of the surrounding water induced by pulsed laser irradiation. This localized heating is exploited in a chemical protection/deprotection strategy to allow selective regions of a nanostructure to be chemically modified. As an exemplar, we use the strategy to enhance the biosensing capabilities of a chiral plasmonic substrate. This novel spatially selective functionalization strategy provides new opportunities for efficient high-throughput control of chemistry on the nanoscale over macroscopic areas for device fabrication.

Novel Swelling-Resistant Sodium Alginate Membrane Branching Modified by Glycogen for Highly Aqueous Ethanol Solution Pervaporation.

PubMed

Ji, Chen-Hao; Xue, Shuang-Mei; Xu, Zhen-Liang

2016-10-12

A novel carbohydrate chain cross-linking method of sodium alginate (SA) is proposed in which glycogen with the branched-chain structure is utilized to cross-link with SA matrix by the bridging of glutaraldehyde (GA). The active layer of SA composite ceramic membrane modified by glycogen and GA for pervaporation (PV) demonstrates great advantages. The branched structure increases the chain density of the active layer, which compresses the free volume between the carbohydrate chains of SA. Large amounts of hydroxyl groups are consumed during the reaction with GA, which reduces the hydrogen bond formation between water molecules and the polysaccharide matrix. The two factors benefit the active layer with great improvement in swelling resistance, promoting the potential of the active layer for the dehydration of an ethanol-water solution containing high water content. Meanwhile, the modified active layer is loaded on the rigid α-Al 2 O 3 ceramic membrane by dip-coating method with the enhancement of anti-deformation and controllable thickness of the active layer. Characterization techniques such as SEM, AFM, XRD, FTIR, XPS, and water contact angle are utilized to observe the composite structure and surface morphology of the composite membrane, to probe the free volume variation, and to determine the chemical composition and hydrophilicity difference of the active layer caused by the different glycogen additive amounts. The membrane containing 3% glycogen in the selective layer demonstrates the flux at 1250 g m -2 h -1 coupled with the separation factor of 187 in the 25 wt % water content feed solution at the operating temperature of 75 °C, reflecting superior pervaporation processing capacity compared with the general organic PV membranes in the same condition.

Sulfur-Modified Zero-Valent Iron for Remediation Applications at DOE Sites - 13600

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fogwell, Thomas W.; Santina, Pete

2013-07-01

Many DOE remediation sites have chemicals of concern that are compounds in higher oxidation states, which make them both more mobile and more toxic. The chemical reduction of these compounds both prevents the migration of these chemicals and in some cases reduces the toxicity. It has also been shown that zero-valent iron is a very effective substance to use in reducing oxygenated compounds in various treatment processes. These have included the treatment of halogenated hydrocarbons in the form volatile organic compounds used as solvents and pesticides. Zero-valent iron has also been used to reduce various oxidized metals such as chromium,more » arsenic, and mercury in order to immobilize them, decrease their toxicity, and prevent further transport. In addition, it has been used to immobilize or break down other non-metallic species such as selenium compounds and nitrates. Of particular interest at several DOE remediation sites is the fact that zero-valent iron is very effective in immobilizing several radioactive metals which are mobile in their oxidized states. These include both technetium and uranium. The main difficulty in using zero-valent iron has been its tendency to become inactive after relatively short periods of time. While it is advantageous to have the zero-valent iron particles as porous as possible in order to provide maximum surface area for reactions to take place, these pores can become clogged when the iron is oxidized. This is due to the fact that ferric oxide has a greater volume for a given mass than metallic iron. When the surfaces of the iron particles oxidize to ferric oxide, the pores become narrower and will eventually shut. In order to minimize the degradation of the chemical activity of the iron due to this process, a modification of zero-valent iron has been developed which prevents or slows this process, which decreases its effectiveness. It is called sulfur-modified iron, and it has been produced in high purity for applications in municipal water treatment applications. Sulfur-modified iron has been found to not only be an extremely economical treatment technology for municipal water supplies, where very large quantities of water must be treated economically, but it has also been demonstrated to immobilize technetium. It has the added benefit of eliminating several other harmful chemicals in water supplies. These include arsenic and selenium. In one large-scale evaluation study an integrated system implemented chemical reduction of nitrate with sulfur-modified iron followed by filtration for arsenic removal. The sulfur-modified iron that was used was an iron-based granular medium that has been commercially developed for the removal of nitrate, co-contaminants including uranium, vanadium and chromium, and other compounds from water. The independent study concluded that 'It is foreseen that the greatest benefit of this technology (sulfur-modified iron) is that it does not produce a costly brine stream as do the currently accepted nitrate removal technologies of ion exchange and reverse osmosis. This investigation confirmed that nitrate reduction via sulfur-modified iron is independent of the hydraulic loading rate. Future sulfur-modified iron treatment systems can be designed without restriction of the reactor vessel dimensions. Future vessels can be adapted to existing site constraints without being limited to height-to-width ratios that would exist if nitrate reduction were to depend on hydraulic loading rate'. Sulfur-modified iron was studied by the Pacific Northwest National Laboratory (PNNL) for its effectiveness in the reduction and permanent sequestration of technetium. The testing was done using Hanford Site groundwater together with sediment. The report stated, 'Under reducing conditions, TcO{sub 4} is readily reduced to TcIV, which forms highly insoluble oxides such at TcO{sub 2}.nH{sub 2}O. However, (re)oxidation of TcIV oxides can lead to remobilization. Under sulfidogenic conditions, most TcIV will be reduced and immobilized as Tc{sub 2}S{sub 7}, which is less readily re-mobilized, even under oxic conditions. This process should be favored by stimulation of sulfidogenic conditions'. The sulfur-modified iron provides the sulfur, together with the iron, to maintain this stable sequestration of technetium. As a result of these and other studies demonstrating the cost-effectiveness of sulfur-modified iron in treating technetium and other hazardous compounds in Hanford Site groundwater and its cost-effectiveness in reducing nitrate, the Richland Operations Office of the Department of Energy issued a change order to the Central Plateau Contractor providing for the testing of sulfur-modified iron in a mobile pilot unit at the Hanford Site. Further testing is anticipated to produce refinements in operating conditions and further optimization of the existing process. (authors)« less

Novel characteristics of sophorolipids, yeast glycolipid biosurfactants, as biodegradable low-foaming surfactants.

PubMed

Hirata, Yoshihiko; Ryu, Mizuyuki; Oda, Yuka; Igarashi, Keisuke; Nagatsuka, Asami; Furuta, Taro; Sugiura, Masaki

2009-08-01

Sophorolipids (SLs) are a family of glycolipid type biosurfactants, which are largely produced by the non-pathogenic yeast, Candida bombicola. In order to investigate the possibility of SLs for industrial use, here we examined the interfacial activities, cytotoxicity and biodegradability of SLs, and compared these properties with those of two lipopeptide type biosurfactants (surfactin and arthrofactin), sodium laurate (soap, SP) and four kinds of chemically synthesized surfactants including two block-copolymer nonionic surfactants (BPs), polyoxyethylene lauryl ether (AE) and sodium dodecyl sulfate (SDS). It was indicated that SLs had extremely low-foaming properties and high detergency comparable with commercially available low-foaming BPs. These interfacial activities of SLs were maintained under 100 ppm water hardness. Cytotoxicity of SLs on human keratinocytes was the same as surfactin, which has already been commercialized as cosmetic material, but higher than BPs. Moreover, biodegradability of SLs using the OECD Guidelines for Testing of Chemicals (301C, Modified MITI Test) displayed that SLs can be classified as "readily" biodegradable chemicals, which are defined as chemicals that are degraded 60% within 28 days under specified test methods. We observed 61% degradation of SLs on the eighth day of cultivation. Our results indicate that SLs are low-foaming surfactants with high detergency, which also exhibit both low cytotoxicity and readily biodegradable properties.

Chemical patterning on preformed porous silicon photonic crystals: towards multiplex detection of protease activity at precise positions†Electronic supplementary information (ESI) available: SEM images, XPS result and more optical reflectivity data. See DOI: 10.1039/c4tb00281dClick here for additional data file.

PubMed

Zhu, Ying; Soeriyadi, Alexander H; Parker, Stephen G; Reece, Peter J; Gooding, J Justin

2014-06-21

Porous silicon (PSi) rugate filters modified with alkyne-terminated monolayers were chemically patterned using a combination of photolithography of photoresist and click chemistry. Two chemical functionalities were obtained by conjugating, via click reactions, ethylene glycol moieties containing two different terminal groups to discrete areas towards the exterior of a PSi rugate filter. The patterning of biological species to the functionalized surface was demonstrated through the conjugation of fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA). Fluorescence microscopy showed selective positioning of FITC-BSA at discretely functionalized areas. Meanwhile, the optical information from precisely defined positions on the patterned surface was monitored by optical reflectivity measurements. The optical measurements revealed successful step-wise chemical functionalization followed by immobilization of gelatin. Multiplex detection of protease activity from different array elements on the patterned surface was demonstrated by monitoring the blue shifts in the reflectivity spectra resulted from the digestion of gelatin by subtilisin. Precise information from both individual elements and average population was acquired. This technique is important for the development of PSi into a microarray platform for highly parallel biosensing applications, especially for cell-based assays.

Identification and characterization of intracellular proteins that bind oligonucleotides with phosphorothioate linkages

PubMed Central

Liang, Xue-hai; Sun, Hong; Shen, Wen; Crooke, Stanley T.

2015-01-01

Although the RNase H-dependent mechanism of inhibition of gene expression by chemically modified antisense oligonucleotides (ASOs) has been well characterized, little is known about the interactions between ASOs and intracellular proteins that may alter cellular localization and/or potency of ASOs. Here, we report the identification of 56 intracellular ASO-binding proteins using multi-step affinity selection approaches. Many of the tested proteins had no significant effect on ASO activity; however, some proteins, including La/SSB, NPM1, ANXA2, VARS and PC4, appeared to enhance ASO activities, likely through mechanisms related to subcellular distribution. VARS and ANXA2 co-localized with ASOs in endocytic organelles, and reduction in the level of VARS altered lysosome/ASO localization patterns, implying that these proteins may facilitate ASO release from the endocytic pathway. Depletion of La and NPM1 reduced nuclear ASO levels, suggesting potential roles in ASO nuclear accumulation. On the other hand, Ku70 and Ku80 proteins inhibited ASO activity, most likely by competition with RNase H1 for ASO/RNA duplex binding. Our results demonstrate that phosphorothioate-modified ASOs bind a set of cellular proteins that affect ASO activity via different mechanisms. PMID:25712094

Ecological guild and enzyme activities of rhizosphere soil microbial communities associated with Bt-maize cultivation under field conditions in North West Province of South Africa.

PubMed

van Wyk, Deidré A B; Adeleke, Rasheed; Rhode, Owen H J; Bezuidenhout, Carlos C; Mienie, Charlotte

2017-09-01

Insecticidal proteins expressed by genetically modified Bt maize may alter the enzymatic and microbial communities associated with rhizosphere soil. This study investigated the structure and enzymatic activity of rhizosphere soil microbial communities associated with field grown Bt and non-Bt maize. Rhizosphere soil samples were collected from Bt and non-Bt fields under dryland and irrigated conditions. Samples were subjected to chemical tests, enzyme analyses, and next generation sequencing. Results showed that nitrate and phosphorus concentrations were significantly higher in non-Bt maize dryland soils, while organic carbon was significantly higher in non-Bt maize irrigated field soil. Acid phosphatase and β-glucosidase activities were significantly reduced in soils under Bt maize cultivation. The species diversity differed between fields and Bt and non-Bt maize soils. Results revealed that Actinobacteria, Proteobacteria, and Acidobacteria were the dominant phyla present in these soils. Redundancy analyses indicated that some chemical properties and enzyme activities could explain differences in bacterial community structures. Variances existed in microbial community structures between Bt and non-Bt maize fields. There were also differences between the chemical and biochemical properties of rhizosphere soils under Bt and non-Bt maize cultivation. These differences could be related to agricultural practices and cultivar type. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aryl-modified graphene quantum dots with enhanced photoluminescence and improved pH tolerance

NASA Astrophysics Data System (ADS)

Luo, Peihui; Ji, Zhe; Li, Chun; Shi, Gaoquan

2013-07-01

Chemical modification is an important technique to modulate the chemical and optical properties of graphene quantum dots (GQDs). In this paper, we report a versatile diazonium chemistry method to graft aryl groups including phenyl, 4-carboxyphenyl, 4-sulfophenyl and 5-sulfonaphthyl to GQDs via Gomberg-Bachmann reaction. The aryl-modified GQDs are nanocrystals with lateral dimensions in the range of 2-4 nm and an average thickness lower than 1 nm. Upon chemical modification with aryl groups, the photoluminescence (PL) bands of GQDs were tuned in the range of 418 and 447 nm, and their fluorescence quantum yields (QYs) were increased for up to about 6 times. Furthermore, the aryl-modified GQDs exhibited stable PL (both intensity and peak position) in a wide pH window of 1-11. The mechanism of improving the PL properties of GQDs by aryl-modification was also discussed.Chemical modification is an important technique to modulate the chemical and optical properties of graphene quantum dots (GQDs). In this paper, we report a versatile diazonium chemistry method to graft aryl groups including phenyl, 4-carboxyphenyl, 4-sulfophenyl and 5-sulfonaphthyl to GQDs via Gomberg-Bachmann reaction. The aryl-modified GQDs are nanocrystals with lateral dimensions in the range of 2-4 nm and an average thickness lower than 1 nm. Upon chemical modification with aryl groups, the photoluminescence (PL) bands of GQDs were tuned in the range of 418 and 447 nm, and their fluorescence quantum yields (QYs) were increased for up to about 6 times. Furthermore, the aryl-modified GQDs exhibited stable PL (both intensity and peak position) in a wide pH window of 1-11. The mechanism of improving the PL properties of GQDs by aryl-modification was also discussed. Electronic supplementary information (ESI) available: Fluorescence quantum yield measurements, estimation of grafting ratio, TEM images, FTIR spectra, PL spectra and zeta potentials. See DOI: 10.1039/c3nr02156d

Integrated Bioinformatics, Environmental Epidemiologic and Genomic Approaches to Identify Environmental and Molecular Links between Endometriosis and Breast Cancer

PubMed Central

Roy, Deodutta; Morgan, Marisa; Yoo, Changwon; Deoraj, Alok; Roy, Sandhya; Yadav, Vijay Kumar; Garoub, Mohannad; Assaggaf, Hamza; Doke, Mayur

2015-01-01

We present a combined environmental epidemiologic, genomic, and bioinformatics approach to identify: exposure of environmental chemicals with estrogenic activity; epidemiologic association between endocrine disrupting chemical (EDC) and health effects, such as, breast cancer or endometriosis; and gene-EDC interactions and disease associations. Human exposure measurement and modeling confirmed estrogenic activity of three selected class of environmental chemicals, polychlorinated biphenyls (PCBs), bisphenols (BPs), and phthalates. Meta-analysis showed that PCBs exposure, not Bisphenol A (BPA) and phthalates, increased the summary odds ratio for breast cancer and endometriosis. Bioinformatics analysis of gene-EDC interactions and disease associations identified several hundred genes that were altered by exposure to PCBs, phthalate or BPA. EDCs-modified genes in breast neoplasms and endometriosis are part of steroid hormone signaling and inflammation pathways. All three EDCs–PCB 153, phthalates, and BPA influenced five common genes—CYP19A1, EGFR, ESR2, FOS, and IGF1—in breast cancer as well as in endometriosis. These genes are environmentally and estrogen responsive, altered in human breast and uterine tumors and endometriosis lesions, and part of Mitogen Activated Protein Kinase (MAPK) signaling pathways in cancer. Our findings suggest that breast cancer and endometriosis share some common environmental and molecular risk factors. PMID:26512648

Flexible strategy for immobilizing redox-active compounds using in situ generation of diazonium salts. Investigations of the blocking and catalytic properties of the layers.

PubMed

Noël, Jean-Marc; Sjöberg, Béatrice; Marsac, Rémi; Zigah, Dodzi; Bergamini, Jean-François; Wang, Aifang; Rigaut, Stéphane; Hapiot, Philippe; Lagrost, Corinne

2009-11-03

A versatile two-step method is developed to covalently immobilize redox-active molecules onto carbon surfaces. First, a robust anchoring platform is grafted onto surfaces by electrochemical reduction of aryl diazonium salts in situ generated. Depending on the nature of the layer termini, -COOH or -NH(2), a further chemical coupling involving ferrocenemethylamine or ferrocene carboxylic acid derivatives leads to the covalent binding of ferrocene centers. The chemical strategy using acyl chloride activation is efficient and flexible, since it can be applied either to surface-reactive end groups or to reactive species in solution. Cyclic voltammetry analyses point to the covalent binding of ferrocene units restricted to the upper layers of the underlying aryl films, while AFM measurements show a lost of compactness of the layers after the chemical attachment of ferrocene centers. The preparation conditions of the anchoring layers were found to determine the interfacial properties of the resulted ferrocenyl-modified electrodes. The ferrocene units promoted effective redox mediation providing that the free redox probes are adequately chosen (i.e., vs size/formal potential) and the underlying layers exhibit strong blocking properties. For anchoring films with weaker blocking effect, the coexistence of two distinct phenomena, redox mediation and ET at pinholes could be evidenced.

Characterization and antibacterial activity of silver exchanged regenerated NaY zeolite from surfactant-modified NaY zeolite.

PubMed

Salim, Mashitah Mad; Malek, Nik Ahmad Nizam Nik

2016-02-01

The antibacterial activity of regenerated NaY zeolite (thermal treatment from cetyltrimethyl ammonium bromide (CTAB)-modified NaY zeolite and pretreatment with Na ions) loaded with silver ions were examined using the broth dilution minimum inhibitory concentration (MIC) method against Escherichia coli (E. coli ATCC 11229) and Staphylococcus aureus (S. aureus ATCC 6538). X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and chemical elemental analyses were used to characterize the regenerated NaY and AgY zeolites. The XRD patterns indicated that the calcination and addition of silver ions on regenerated NaY zeolite did not affect the structure of the regenerated NaY zeolite as the characteristic peaks of the NaY zeolite were retained, and no new peaks were observed. The regenerated AgY zeolite showed good antibacterial activity against both bacteria strains in distilled water, and the antibacterial activity of the samples increased with increasing Ag loaded on the regenerated AgY zeolite; the regenerated AgY zeolite was more effective against E. coli than S. aureus. However, the antibacterial activity of the regenerated AgY was not effective in saline solution for both bacteria. The study showed that CTAB-modified NaY zeolite materials could be regenerated to NaY zeolite using thermal treatment (550°C, 5h) and this material has excellent performance as an antibacterial agent after silver ions loading. Copyright © 2015 Elsevier B.V. All rights reserved.

Treatment of low level radioactive liquid waste containing appreciable concentration of TBP degraded products.

PubMed

Valsala, T P; Sonavane, M S; Kore, S G; Sonar, N L; De, Vaishali; Raghavendra, Y; Chattopadyaya, S; Dani, U; Kulkarni, Y; Changrani, R D

2011-11-30

The acidic and alkaline low level radioactive liquid waste (LLW) generated during the concentration of high level radioactive liquid waste (HLW) prior to vitrification and ion exchange treatment of intermediate level radioactive liquid waste (ILW), respectively are decontaminated by chemical co-precipitation before discharge to the environment. LLW stream generated from the ion exchange treatment of ILW contained high concentrations of carbonates, tributyl phosphate (TBP) degraded products and problematic radio nuclides like (106)Ru and (99)Tc. Presence of TBP degraded products was interfering with the co-precipitation process. In view of this a modified chemical treatment scheme was formulated for the treatment of this waste stream. By mixing the acidic LLW and alkaline LLW, the carbonates in the alkaline LLW were destroyed and the TBP degraded products got separated as a layer at the top of the vessel. By making use of the modified co-precipitation process the effluent stream (1-2 μCi/L) became dischargeable to the environment after appropriate dilution. Based on the lab scale studies about 250 m(3) of LLW was treated in the plant. The higher activity of the TBP degraded products separated was due to short lived (90)Y isotope. The cement waste product prepared using the TBP degraded product was having good chemical durability and compressive strength. Copyright © 2011 Elsevier B.V. All rights reserved.

Single, simultaneous and consecutive biosorption of Cr(VI) and Orange II onto chemically modified masau stones.

PubMed

Albadarin, Ahmad B; Solomon, Samuel; Kurniawan, Tonni Agustiono; Mangwandi, Chirangano; Walker, Gavin

2017-12-15

Novel and low cost chemically modified masau stone (CMMS) was investigated for its biosorption of an anionic azo dye, Orange II (OII), and toxic hexavalent chromium (Cr(VI)) from aqueous systems: individually, simultaneously and consecutively. XPS and FTIR analyses indicated the introduction of quaternary-Nitrogen to the CMMS surface after activation with epichlorohydrin (etherifying agent) and diethylenetriamine (crosslinking agent). The effects of pH, contact time and initial concentration (C o ), and loading order on mechanisms of biosorption/reduction of OII and Cr(VI) onto CMMS were examined in detail. Several analytical techniques were employed to characterise the physio-chemical properties of the CMMS and determine the biosorption mechanisms. The pseudo second order and redox models were able to adequately predict the kinetics of biosorption. The Langmuir maximum OII biosorption capacity (q max ) was calculated as 136.8 mg/g for the dye onto the Cr(VI)-loaded CMMS consecutive system at C o  = 100 mg/dm 3 . The q max for the Cr(VI) system was found to be 87.32 mg/g at the same C o max. This reveals that the biosorption of OII and Cr(VI) mainly takes place via two different mechanisms i.e. hydrogen bonding and electrostatic attraction for the dye, and biosorption-coupled reduction for Cr(VI). Copyright © 2017 Elsevier Ltd. All rights reserved.

Co3O4 nanocrystals with exposed low-surface-energy planes anchored on chemically integrated graphitic carbon nitride-modified nitrogen-doped graphene: A high-performance anode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhang, Wenyao; Fu, Yongsheng; Wang, Xin

2018-05-01

A facile strategy to synthesize a composite composed of cubic Co3O4 nanocrystals anchored on chemically integrated g-C3N4-modified N-graphene (CN-NG) as an advanced anode material for high-performance lithium-ion batteries is reported. It is found that the morphology of the Co3O4 nanocrystals contains blunt-edge nanocubes with well-demarcated boundaries and numerous exposed low-index (1 1 1) crystallographic facets. These planes can be directly involved in the electrochemical reactions, providing rapid Li-ion transport channels for charging and discharging and thus enhancing the round-trip diffusion efficiency. On the other hand, the CN-NG support displays unusual textural features, such as superior structural stability, accessible active sites, and good electrical conductivity. The experimental results reveal that the chemical and electronic coupling of graphitic carbon nitride and nitrogen-doped graphene synergistically facilitate the anchoring of Co3O4 nanocrystals and prevents their migration. The resulting Co3O4/CN-NG composite exhibits a high specific reversible capacity of up to 1096 mAh g-1 with excellent cycling stability and rate capability. We believe that such a hybrid carbon support could open a new path for applications in electrocatalysis, sensors, supercapacitors, etc., in the near future.

Sequence-specific 1H-NMR assignments for the aromatic region of several biologically active, monomeric insulins including native human insulin.

PubMed

Roy, M; Lee, R W; Kaarsholm, N C; Thøgersen, H; Brange, J; Dunn, M F

1990-06-12

The aromatic region of the 1H-FT-NMR spectrum of the biologically fully-potent, monomeric human insulin mutant, B9 Ser----Asp, B27 Thr----Glu has been investigated in D2O. At 1 to 5 mM concentrations, this mutant insulin is monomeric above pH 7.5. Coupling and amino acid classification of all aromatic signals is established via a combination of homonuclear one- and two-dimensional methods, including COSY, multiple quantum filters, selective spin decoupling and pH titrations. By comparisons with other insulin mutants and with chemically modified native insulins, all resonances in the aromatic region are given sequence-specific assignments without any reliance on the various crystal structures reported for insulin. These comparisons also give the sequence-specific assignments of most of the aromatic resonances of the mutant insulins B16 Tyr----Glu, B27 Thr----Glu and B25 Phe----Asp and the chemically modified species des-(B23-B30) insulin and monoiodo-Tyr A14 insulin. Chemical dispersion of the assigned resonances, ring current perturbations and comparisons at high pH have made possible the assignment of the aromatic resonances of human insulin, and these studies indicate that the major structural features of the human insulin monomer (including those critical to biological function) are also present in the monomeric mutant.

Improved actuation strain of PDMS-based DEA materials chemically modified with softening agents

NASA Astrophysics Data System (ADS)

Biedermann, Miriam; Blümke, Martin; Wegener, Michael; Krüger, Hartmut

2015-04-01

Dielectric elastomer actuators (DEAs) are smart materials that gained much in interest particularly in recent years. One active field of research is the improvement of their properties by modification of their structural framework. The object of this work is to improve the actuation properties of polydimethylsiloxane (PDMS)-based DEAs by covalent incorporation of mono-vinyl-terminated low-molecular PDMS chains into the PDMS network. These low-molecular units act as a kind of softener within the PDMS network. The loose chain ends interfere with the network formation and lower the network's density. PDMS films with up to 50wt% of low-molecular PDMS additives were manufactured and the chemical, mechanical, electrical, and electromechanical properties of these novel materials were investigated.

Calculating the mean time to capture for tethered ligands and its effect on the chemical equilibrium of bound ligand pairs.

PubMed

Shen, Lu; Decker, Caitlin G; Maynard, Heather D; Levine, Alex J

2016-09-01

We present here the calculation of the mean time to capture of a tethered ligand to the receptor. This calculation is then used to determine the shift in the partitioning between (1) free, (2) singly bound, and (3) doubly bound ligands in chemical equilibrium as a function of the length of the tether. These calculations are used in the research article Fibroblast Growth Factor 2 Dimer with Superagonist in vitro Activity Improves Granulation Tissue Formation During Wound Healing (Decker et al., in press [1]) to explain quantitatively how changes in polymeric linker length in the ligand dimers modifies the efficacy of these molecules relative to that of free ligands.

CRRES combined radiation and release effects satellite program

NASA Technical Reports Server (NTRS)

Giles, B. L. (Compiler); Mccook, M. A. (Compiler); Mccook, M. W. (Compiler); Miller, G. P. (Compiler)

1995-01-01

The various regions of the magnetosphere-ionosphere system are coupled by flows of charged particle beams and electromagnetic waves. This coupling gives rise to processes that affect both technical and non-technical aspects of life on Earth. The CRRES Program sponsored experiments which were designed to produce controlled and known input to the space environment and the effects were measured with arrays of diagnostic instruments. Large amounts of material were used to modify and perturb the environment in a controlled manner, and response to this was studied. The CRRES and PEGSAT satellites were dual-mission spacecraft with a NASA mission to perform active chemical-release experiments, grouped into categories of tracer, modification, and simulation experiments. Two sounding rocket chemical release campaigns completed the study.

Hydrocarbon-stapled lipopeptides exhibit selective antimicrobial activity.

PubMed

Jenner, Zachary B; Crittenden, Christopher M; Gonzalez, Martín; Brodbelt, Jennifer S; Bruns, Kerry A

2017-05-01

Antimicrobial peptides (AMPs) occur widely in nature and have been studied for their therapeutic potential. AMPs are of interest due to the large number of possible chemical structural combinations using natural and unnatural amino acids, with varying effects on their biological activities. Using physicochemical properties from known naturally occurring amphipathic cationic AMPs, several hydrocarbon-stapled lipopeptides (HSLPs) were designed, synthesized, and tested for antimicrobial properties. Peptides were chemically modified by N-terminal acylation, C-terminal amidation, and some were hydrocarbon stapled by intramolecular olefin metathesis. The effects of peptide length, amphipathic character, and stapling on antimicrobial activity were tested against Escherichia coli, three species of Gram-positive bacteria (Staphylococcus aureus, Bacillus megaterium, and Enterococcus faecalis), and two strains of Candida albicans. Peptides were shown to disrupt liposomes of different phospholipid composition, as measured by leakage of a fluorescent compound from vesicles. Peptides with (S)-2-(4'-pentenyl)-alanine substituted for l-alanine in a reference peptide showed a marked increase in antimicrobial activity, hemolysis, and membrane disruption. Stapled peptides exhibited slightly higher antimicrobial potency; those with greatest hydrophobic character showed the greatest hemolysis and liposome leakage, but lower antimicrobial activity. The results support a model of HSLPs as membrane-disruptive AMPs with potent antimicrobial activity and relatively low hemolytic potential at biologically active peptide concentrations. © 2017 Wiley Periodicals, Inc.

Release of LHRH-activity from human fetal membranes upon exposure to PGE/sub 2/, oxytocin and isoproterenol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poisner, A.M.; Poisner, R.; Becca, C.R.

1986-03-01

The authors have previously reported that superfused chorion laeve (fetal membranes) release LHRH-like immunoreactivity upon exposure to angiotensin II. They have now studied the effects of other agonists on the release of LHRH-activity and something of its chemical nature. Fetal membranes were obtained from placentas delivered by cesarean section, the amnion stripped from the chorion, and the chorion superfused in an Amicon thin-channel device with the maternal surface facing up. The whole device was submerged in a 37 C water bath and perfused with a modified Locke's solution at 0.4 - 1.0 ml/min. LHRH-activity was measured by radioimmunoassay using threemore » different antisera against LHRH. The release of LHRH-activity was stimulated by 6-10 min exposure to PGE/sub 2/, oxytocin, and isoproterenol. Extracts of chorion were studied using gel filtration on Sephacryl S-200 and ultrafiltration with Amicon PM-10 filters. The bulk of the LHRH-activity appeared as a higher molecular weight form (about 70,000 daltons). Since oxytocin has been reported to release PGE/sub 2/ from chorion, it may release LHRH-activity by virtue of liberating endogenous PGE/sub 2/. The chemical nature of the LHRH-activity is presently under investigation.« less

In vitro antioxidant activity of rice protein affected by alkaline degree and gastrointestinal protease digestion.

PubMed

Liu, Ye; Wang, Zhengxuan; Li, Hui; Liang, Mingcai; Yang, Lin

2016-12-01

To elucidate whether and how alkali treatment, which is a common process for rice protein (RP) extraction, affects antioxidant activity of RP, the different degree of alkali (from 0.1% to 0.4% of NaOH) was used to extract RP (RP-1, RP-2, RP-3, RP-4). The antioxidant capacities of scavenging free radicals [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid] diammonium salt, ABTS; 1,1-diphenyl-2-picrylhydrazyl, DPPH), chelating metals (iron, copper) and reducing power investigated in the hydrolysates of RPs (RP-1, RP-2, RP-3, RP-4) during in vitro pepsin-pancreatin digestion were effectively affected by alkali treatment. The present study demonstrated that the weakest antioxidant responses to ABTS radical-scavenging activity, DPPH radical-scavenging activity, iron chelating activity, copper chelating activity and reducing power were produced by RP-4 extracted by the highest alkali proportion (0.4% NaOH). The present study indicates that antioxidant capacity of RP could be more readily depressed by strict alkali degree and affected by gastrointestinal proteases. Results suggest that alkali extraction is a vital process to regulate the antioxidant activity of RP through modifying the compositions of amino acids, which are dependent on alkali magnitude. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Common structural changes accompany the functional inactivation of HPr by seryl phosphorylation or by serine to aspartate substitution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wittekind, M.; Klevit, R.E.; Reizer, J.

1989-12-26

Although many proteins are known to be regulated via reversible phosphorylation, little is known about the mechanism by which the covalent modification of seryl, threonyl, or tyrosyl residues alters the activities of the target systems. To address this question, modified versions of bacillus subtilus HPr, a protein component of the bacterial phosphotransferase system, have been studied by {sup 1}H NMR spectroscopy. Phosphorylation at Ser{sub 46} or a Ser to Asp substitution at this position inactivates HPr. Two-dimensional spectra of these two modified proteins display nearly identical proton chemical shifts that differ significantly from those observed in the spectra of themore » unphosphorylated, wild-type protein and of functionally active HPr mutants. These results demonstrate that the functional inactivation of HPr brought about by the serine to aspartate mutation is accompanied by the same structural changes that occur when HPr is phosphorylated at Ser{sub 46}.« less

Chemically modified maize cobs waste with enhanced adsorption properties upon methyl orange and arsenic.

PubMed

Elizalde-González, María P; Mattusch, J; Wennrich, R

2008-07-01

The surface chemistry of maize naturasorbent was altered in this work by the modifying agents: phosphoric acid and different amines (triethanolamine, diethylenetriamine and 1,4-diaminobutane). Removal of methyl orange (25 mg l(-1)) was <50% by maize corn cobs modified by phosphorylation and higher by the quaternized samples: 68% with the 1,4-diaminobutane and 73% with the diethylenetriamine modificators. Adsorption of arsenite by the samples modified with phosphoric acid/ammonia was 11 microg g(-1), which corresponds to 98% removal from a 550 microg As l(-1) solution for an adsorbent dose of 50 mg ml(-1). The samples modified by phosphoric acid/urea removed 0.4 microg g(-1) arsenate from a 300 mug As l(-1) solution. Adsorption of methyl orange, arsenite and arsenate was superior by the chemically modified maize cobs judged against the initial naturasorbent. For comparison, removal by the commercial anion exchanger was 100% for methyl orange, 45% (5 microg g(-1)) for arsenite and 99% (5 microg g(-1)) for arsenate.

Surface characterization and free thyroid hormones response of chemically modified poly(ethylene terephthalate) blood collection tubes

NASA Astrophysics Data System (ADS)

Jalali Dil, Ebrahim; Kim, Samuel C.; Saffar, Amir; Ajji, Abdellah; Zare, Richard N.; Sattayapiwat, Annie; Esguerra, Vanessa; Bowen, Raffick A. R.

2018-06-01

The surface chemistry and surface energy of chemically modified polyethylene terephthalate (PET) blood collection tubes (BCTs) were studied and the results showed a significant increase in hydrophilicity and polarity of modified PET surface. The surface modification created nanometer-sized, needle-like asperities through molecular segregation at the surface. The surface dynamics of the modified PET was examined by tracking its surface properties over a 280-day period. The results showed surface rearrangement toward a surface with lower surface energy and fewer nanometer-sized asperities. Thromboelastography (TEG) was used to evaluate and compare the thrombogenicity of the inner walls of various types of BCTs. The TEG tracings and data from various types of BCTs demonstrated differences in the reactionand coagulation times but not in clot strength. The performance of the modified tubes in free triiodothyronine (FT3) and free thyroxine (FT4) hormone tests was examined, and it was found that the interference of modified PET tubes was negligible compared to that of commercially available PET BCTs.

Nano-TiO2 decorated carbon coating on the separator to physically and chemically suppress the shuttle effect for lithium-sulfur battery

NASA Astrophysics Data System (ADS)

Shao, Hongyuan; Wang, Weikun; Zhang, Hao; Wang, Anbang; Chen, Xiaonong; Huang, Yaqin

2018-02-01

Despite recent progress in designing modified separators for lithium-sulfur (Li-S) batteries, detail in optimizing the synergistic effect between chemical and physical immobilization for lithium polysulfides (LiPS) in modified separator hasn't been investigated totally. Here, a nano-TiO2 decorated carbon layer (T-DCL) has been successfully applied to modify separator for the Li-S battery. The results indicate that appropriate weight percentage of nano-TiO2 uniformly distributed in conductive carbon layer is effective to chemically and physically immobilize for LiPS, and promote the electron transfer during discharge/charge process. The performance of the modified Li-S battery with T-DCL separator are significantly enhanced, with a specific capacity of 883 mAh g-1 retained after 180 cycles at 0.1 C and 762 mAh g-1 retained after 200 cycles at 0.5C, which are much higher than that of separators only coated with TiO2 layer or conductive carbon layer. Besides, the separator coated with T-DCL also shows low electrochemical impedance and good lithium anode protection. These results indicate that separator with T-DCL is promising to balance the physical and chemical LiPS trapping effect, and optimize the electrochemical performance for Li-S battery.

Site-selective chemical modification of chymotrypsin using peptidyl derivatives bearing optically active diphenyl 1-amino-2-phenylethylphosphonate: Stereochemical effect of the diphenyl phosphonate moiety.

PubMed

Ono, Shin; Nakai, Takahiko; Kuroda, Hirofumi; Miyatake, Ryuta; Horino, Yoshikazu; Abe, Hitoshi; Umezaki, Masahito; Oyama, Hiroshi

2016-11-04

Diphenyl (α-aminoalkyl)phosphonates act as mechanism-based inhibitors against serine proteases by forming a covalent bond with the hydroxy group of the active center Ser residue. Because the covalent bond was found to be broken and replaced by 2-pyridinaldoxime methiodide (2PAM), we employed a peptidyl derivative bearing diphenyl 1-amino-2-phenylethylphosphonate moiety (Phe(p) (OPh)2 ) to target the active site of chymotrypsin and to selectively anchor to Lys175 in the vicinity of the active site. Previously, it was reported that the configuration of the α-carbon of phosphorus in diphenyl (α-aminoalkyl)phosphonates affects the inactivation reaction of serine proteases, i.e., the (R)-enantiomeric diphenyl phosphonate is comparable to l-amino acids and it effectively reacts with serine proteases, whereas the (S)-enantiomeric form does not. In this study, we evaluated the stereochemical effect of the phosphonate moiety on the selective chemical modification. Epimeric dipeptidyl derivatives, Ala-(R or S)-Phe(p) (OPh)2 , were prepared by separation with RP-HPLC. A tripeptidyl (R)-epimer (Ala-Ala-(R)-Phe(p) (OPh)2 ) exhibited a more potent inactivation ability against chymotrypsin than the (S)-epimer. The enzyme inactivated by the (R)-epimer was more effectively reactivated with 2PAM than the enzyme inactivated by the (S)-epimer. Finally, N-succinimidyl (NHS) active ester derivatives, NHS-Suc-Ala-Ala- (R or S)-Phe(p) (OPh)2 , were prepared, and we evaluated their action when modifying Lys175 in chymotrypsin. We demonstrated that the epimeric NHS derivative that possessed the diphenyl phosphonate moiety with the (R)-configuration effectively modified Lys175 in chymotrypsin, whereas that with the (S)-configuration did not. These results demonstrate the utility of peptidyl derivatives that bear an optically active diphenyl phosphonate moiety as affinity labeling probes in protein bioconjugation. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 521-530, 2016. © 2015 Wiley Periodicals, Inc.

Thermal isomerization of azobenzenes: on the performance of Eyring transition state theory.

PubMed

Rietze, Clemens; Titov, Evgenii; Lindner, Steven; Saalfrank, Peter

2017-08-09

The thermal [Formula: see text] (back-)isomerization of azobenzenes is a prototypical reaction occurring in molecular switches. It has been studied for decades, yet its kinetics is not fully understood. In this paper, quantum chemical calculations are performed to model the kinetics of an experimental benchmark system, where a modified azobenzene (AzoBiPyB) is embedded in a metal-organic framework (MOF). The molecule can be switched thermally from cis to trans, under solvent-free conditions. We critically test the validity of Eyring transition state theory for this reaction. As previously found for other azobenzenes (albeit in solution), good agreement between theory and experiment emerges for activation energies and activation free energies, already at a comparatively simple level of theory, B3LYP/6-31G * including dispersion corrections. However, theoretical Arrhenius prefactors and activation entropies are in qualitiative disagreement with experiment. Several factors are discussed that may have an influence on activation entropies, among them dynamical and geometric constraints (imposed by the MOF). For a simpler model-[Formula: see text] isomerization in azobenzene-a systematic test of quantum chemical methods from both density functional theory and wavefunction theory is carried out in the context of Eyring theory. Also, the effect of anharmonicities on activation entropies is discussed for this model system. Our work highlights capabilities and shortcomings of Eyring transition state theory and quantum chemical methods, when applied for the [Formula: see text] (back-)isomerization of azobenzenes under solvent-free conditions.

Thermal isomerization of azobenzenes: on the performance of Eyring transition state theory

NASA Astrophysics Data System (ADS)

Rietze, Clemens; Titov, Evgenii; Lindner, Steven; Saalfrank, Peter

2017-08-01

The thermal Z\\to E (back-)isomerization of azobenzenes is a prototypical reaction occurring in molecular switches. It has been studied for decades, yet its kinetics is not fully understood. In this paper, quantum chemical calculations are performed to model the kinetics of an experimental benchmark system, where a modified azobenzene (AzoBiPyB) is embedded in a metal-organic framework (MOF). The molecule can be switched thermally from cis to trans, under solvent-free conditions. We critically test the validity of Eyring transition state theory for this reaction. As previously found for other azobenzenes (albeit in solution), good agreement between theory and experiment emerges for activation energies and activation free energies, already at a comparatively simple level of theory, B3LYP/6-31G* including dispersion corrections. However, theoretical Arrhenius prefactors and activation entropies are in qualitiative disagreement with experiment. Several factors are discussed that may have an influence on activation entropies, among them dynamical and geometric constraints (imposed by the MOF). For a simpler model—Z\\to E isomerization in azobenzene—a systematic test of quantum chemical methods from both density functional theory and wavefunction theory is carried out in the context of Eyring theory. Also, the effect of anharmonicities on activation entropies is discussed for this model system. Our work highlights capabilities and shortcomings of Eyring transition state theory and quantum chemical methods, when applied for the Z\\to E (back-)isomerization of azobenzenes under solvent-free conditions.

Modulation of the norfloxacin resistance in Staphylococcus aureus by Cordia verbenaceae DC

PubMed Central

Matias, Edinardo F.F.; Santos, Karla K. A.; Falcão-Silva, Vivyanne S.; Siqueira-Júnior, José P.; Costa, José G. M.; Coutinho, Henrique D.M.

2013-01-01

Background & objectives: Several chemical compounds isolated from natural sources have antibacterial activity and some enhance the antibacterial activity of antibiotics reversing the natural resistance of bacteria to certain antibiotics. In this study, the hexane and methanol extract of Cordia verbenaceae were assessed for antibacterial activity alone and combinated with norfloxacin against the Staphylococcus aureus strain SA1199B. Methods: The minimum inhibitory concentration (MIC) of extracts was assayed using microdilution assay and the modulatory activity was evaluated using plate diffusion assay. Results: The MIC observed varied between 256 to >1024 μg/ml. However, the antibiotic activity of norfloxacin was enhanced in the presence of subinhibitory concentrations of hexane extract of C. verbenaceae (HECV). Interpretations & conclusions: Our results indicate that Cordia verbenaceae DC. can be a source of plant derived products with antibiotic modifying activity. PMID:23481069

Catalytic conversion of biomass pyrolysis-derived compounds with chemical liquid deposition (CLD) modified ZSM-5.

PubMed

Zhang, Huiyan; Luo, Mengmeng; Xiao, Rui; Shao, Shanshan; Jin, Baosheng; Xiao, Guomin; Zhao, Ming; Liang, Junyu

2014-03-01

Chemical liquid deposition (CLD) with KH550, TEOS and methyl silicone oil as the modifiers was used to modify ZSM-5 and deposit its external acid sites. The characteristics of modified catalysts were tested by catalytic conversion of biomass pyrolysis-derived compounds. The effects of different modifying conditions (deposited amount, temperature, and time) on the product yields and selectivities were investigated. The results show KH550 modified ZSM-5 (deposited amount of 4%, temperature of 20°C and time of 6h) produced the maximum yields of aromatics (24.5%) and olefins (16.5%), which are much higher than that obtained with original ZSM-5 catalyst (18.8% aromatics and 9.8% olefins). The coke yield decreased from 44.1% with original ZSM-5 to 26.7% with KH550 modified ZSM-5. The selectivities of low-molecule-weight hydrocarbons (ethylene and benzene) decreased, while that of higher molecule-weight hydrocarbons (propylene, butylene, toluene, and naphthalene) increased comparing with original ZSM-5. Copyright © 2013 Elsevier Ltd. All rights reserved.

A Diversity-Oriented Library of Fluorophore-Modified Receptors Constructed from a Chemical Library of Synthetic Fluorophores.

PubMed

Nakano, Shun; Tamura, Tomoki; Das, Raj Kumar; Nakata, Eiji; Chang, Young-Tae; Morii, Takashi

2017-11-16

The practical application of biosensors can be determined by evaluating the sensing ability of fluorophore-modified derivatives of a receptor with appropriate recognition characteristics for target molecules. One of the key determinants for successfully obtaining a useful biosensor is wide variation in the fluorophores attached to a given receptor. Thus, using a larger fluorophore-modified receptor library provides a higher probability of obtaining a practically useful biosensor. However, no effective method has yet been developed for constructing such a diverse library of fluorophore-modified receptors. Herein, we report a method for constructing fluorophore-modified receptors by using a chemical library of synthetic fluorophores with a thiol-reactive group. This library was converted into a library of fluorophore-modified adenosine-binding ribonucleopeptide (RNP) receptors by introducing the fluorophores to the Rev peptide of the RNP complex by alkylation of the thiol group. This method enabled the construction of 263 fluorophore-modified ATP-binding RNP receptors and allowed the selection of suitable receptor-based fluorescent sensors that target ATP. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile fabrication of CNT-based chemical sensor operating at room temperature

NASA Astrophysics Data System (ADS)

Sheng, Jiadong; Zeng, Xian; Zhu, Qi; Yang, Zhaohui; Zhang, Xiaohua

2017-12-01

This paper describes a simple, low cost and effective route to fabricate CNT-based chemical sensors, which operate at room temperature. Firstly, the incorporation of silk fibroin in vertically aligned CNT arrays (CNTA) obtained through a thermal chemical vapor deposition (CVD) method makes the direct removal of CNT arrays from substrates without any rigorous acid or sonication treatment feasible. Through a simple one-step in situ polymerization of anilines, the functionalization of CNT arrays with polyaniline (PANI) significantly improves the sensing performance of CNT-based chemical sensors in detecting ammonia (NH3) and hydrogen chloride (HCl) vapors. Chemically modified CNT arrays also show responses to organic vapors like menthol, ethyl acetate and acetone. Although the detection limits of chemically modified CNT-based chemical sensors are of the same orders of magnitudes reported in previous studies, these CNT-based chemical sensors show advantages of simplicity, low cost and energy efficiency in preparation and fabrication of devices. Additionally, a linear relationship between the relative sensitivity and concentration of analyte makes precise estimations on the concentrations of trace chemical vapors possible.

Is Allelopathic Activity of Ipomoea murucoides Induced by Xylophage Damage?

PubMed Central

Flores-Palacios, Alejandro; Corona-López, Angélica María; Rios, María Yolanda; Aguilar-Guadarrama, Berenice; Toledo-Hernández, Víctor Hugo; Rodríguez-López, Verónica; Valencia-Díaz, Susana

2015-01-01

Herbivory activates the synthesis of allelochemicals that can mediate plant-plant interactions. There is an inverse relationship between the activity of xylophages and the abundance of epiphytes on Ipomoea murucoides. Xylophagy may modify the branch chemical constitution, which also affects the liberation of allelochemicals with defense and allelopathic properties. We evaluated the bark chemical content and the effect of extracts from branches subjected to treatments of exclusion, mechanical damage and the presence/absence of epiphytes, on the seed germination of the epiphyte Tillandsia recurvata. Principal component analysis showed that branches without any treatment separate from branches subjected to treatments; damaged and excluded branches had similar chemical content but we found no evidence to relate intentional damage with allelopathy; however 1-hexadecanol, a defense volatile compound correlated positively with principal component (PC) 1. The chemical constitution of branches subject to exclusion plus damage or plus epiphytes was similar among them. PC2 indicated that palmitic acid (allelopathic compound) and squalene, a triterpene that attracts herbivore enemies, correlated positively with the inhibition of seed germination of T. recurvata. Inhibition of seed germination of T. recurvata was mainly correlated with the increment of palmitic acid and this compound reached higher concentrations in excluded branches treatments. Then, it is likely that the allelopathic response of I. murucoides would increase to the damage (shade, load) that may be caused by a high load of epiphytes than to damage caused by the xylophages. PMID:26625350

THE USE OF CHEMICALS AS PLANT REGULATORS. AGRICULTURAL CHEMICALS TECHNOLOGY, NUMBER 8.

ERIC Educational Resources Information Center

Ohio State Univ., Columbus. Center for Vocational and Technical Education.

ONE OF A SERIES DESIGNED TO ASSIST TEACHERS IN PREPARING POST-SECONDARY STUDENTS FOR AGRICULTURAL CHEMICAL OCCUPATIONS, THIS MODULE IS SPECIFICALLY CONCERNED WITH CHEMICALS AS PLANT REGULATORS. IT WAS DEVELOPED BY A NATIONAL TASK FORCE ON THE BASIS OF DATA FROM STATE STUDIES. SECTIONS INCLUDE -- (1) CHEMICALS AS MODIFIERS OF PLANT GROWTH, (2)…

A biomimetic approach to the chemical inactivation of chrysotile fibres by lichen metabolites.

PubMed

Turci, Francesco; Favero-Longo, Sergio E; Tomatis, Maura; Martra, Gianmario; Castelli, Daniele; Piervittori, Rosanna; Fubini, Bice

2007-01-01

Some lichens were recently reported to modify the surface state of asbestos. Here we report some new insight on the physico-chemical modifications induced by natural chelators (lichen metabolites) on two asbestos samples collected in two different locations. A biomimetic approach was followed by reproducing in the laboratory the weathering effect of lichen metabolites. Norstictic, pulvinic and oxalic acid (0.005, 0.5 and 50 mM) were put in contact with chrysotile fibres, either in pure form (A) or intergrown with balangeroite, an iron-rich asbestiform phase (B). Mg and Si removal, measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), reveals an incongruent dissolution for pure chrysotile (A), with Mg removal always exceeding that of Si, while chrysotile-balangeroite (B) follows a congruent dissolution pattern in all cases except in the presence of 50 mM oxalic acid. A much larger removal of Mg than Si in the solutions of 0.5 and 50 mM oxalic acid with chrysotile (A) suggests a structural collapse, which in the case of chrysotile-balangeroite (B) only occurs with 50 mM oxalic acid; in these cases both samples are converted into amorphous silica (as detected by X-ray diffraction (XRD)). Subsequent to incubation, some new phases (Fe(2)O(3), CaMg(CO(3))(2), Ca(C(2)O(4)) x H(2)O and Mg(C(2)O(4))2 x H(2)O), similar to those observed in the field, were detected by XRD and micro-Raman spectroscopy. The leaching effect of lichen metabolites also modifies the Fenton activity, a process widely correlated with asbestos pathogenicity: pure chrysotile (A) activity is reduced by 50 mM oxalic acid, while all lichen metabolites reduce the activity of chrysotile-balangeroite (B). The selective removal of poorly coordinated, highly reactive iron ions, evidenced by NO adsorption, accounts for the loss in Fenton activity. Such fibres were chemically close to the ones observed in the field. Chrysotile-rich rocks, colonised by lichens, could be exposed to a natural bioattenuation and considered as a transient environmental hazard.

A comparison of simple global kinetic models for coal devolatilization with the CPD model

DOE PAGES

Richards, Andrew P.; Fletcher, Thomas H.

2016-08-01

Simulations of coal combustors and gasifiers generally cannot incorporate the complexities of advanced pyrolysis models, and hence there is interest in evaluating simpler models over ranges of temperature and heating rate that are applicable to the furnace of interest. In this paper, six different simple model forms are compared to predictions made by the Chemical Percolation Devolatilization (CPD) model. The model forms included three modified one-step models, a simple two-step model, and two new modified two-step models. These simple model forms were compared over a wide range of heating rates (5 × 10 3 to 10 6 K/s) at finalmore » temperatures up to 1600 K. Comparisons were made of total volatiles yield as a function of temperature, as well as the ultimate volatiles yield. Advantages and disadvantages for each simple model form are discussed. In conclusion, a modified two-step model with distributed activation energies seems to give the best agreement with CPD model predictions (with the fewest tunable parameters).« less

Progress in the preparation and application of modified biochar for improved contaminant removal from water and wastewater.

PubMed

Ahmed, Mohammad Boshir; Zhou, John L; Ngo, Huu H; Guo, Wenshan; Chen, Mengfang

2016-08-01

Modified biochar (BC) is reviewed in its preparation, functionality, applications and regeneration. The nature of precursor materials, preparatory conditions and modification methods are key factors influencing BC properties. Steam activation is unsuitable for improving BC surface functionality compared with chemical modifications. Alkali-treated BC possesses the highest surface functionality. Both alkali modified BC and nanomaterial impregnated BC composites are highly favorable for enhancing the adsorption of different contaminants from wastewater. Acidic treatment provides more oxygenated functional groups on BC surfaces. The Langmuir isotherm model provides the best fit for sorption equilibria of heavy metals and anionic contaminants, while the Freundlich isotherm model is the best fit for emerging contaminants. The pseudo 2(nd) order is the most appropriate model of sorption kinetics for all contaminants. Future research should focus on industry-scale applications and hybrid systems for contaminant removal due to scarcity of data. Copyright © 2016 Elsevier Ltd. All rights reserved.

Lipid degradation and sensory characteristics of ripened sausages packed in modified atmosphere at different carbon dioxide concentrations.

PubMed

Summo, Carmine; Pasqualone, Antonella; Paradiso, Vito Michele; Centomani, Isabella; Centoducati, Gerardo; Caponio, Francesco

2016-01-15

Conflicting results about the effect of modified atmosphere packaging (MAP) rich in CO2 on the quality of different kinds of meat products are present in the literature. In this study, the degree of lipid degradation and the sensory characteristics of ripened sausages packed in modified atmosphere at three different carbon dioxide (CO2) concentrations were evaluated during 5 months of storage. The degree of hydrolytic degradation of the lipid fraction was found to decrease with increasing CO2 concentration. Similarly, oxidative phenomena occurred at a lower rate when the CO2 concentration increased. The variations in CO2 concentration influenced the perception of rancid flavor in the examined sausages. An increase in CO2 concentration in MAP slowed down the evolution of lipid oxidation owing to the minor extent of hydrolytic degradation, whose products have pro-oxidant activity. This effect was more evident in the first 2 months of storage. © 2015 Society of Chemical Industry.

Novel potato micro-tuber-inducing compound, (3R,6S)-6-hydroxylasiodiplodin, from a strain of Lasiodiplodia theobromae.

PubMed

Li, Peng; Takahashi, Kosaku; Matsuura, Hideyuki; Yoshihara, Teruhiko

2005-08-01

A novel potato micro-tuber-inducing compound was isolated from the culture broth of Lasiodiplodia theobromae Shimokita 2. The structure of the isolated compound was determined as (3R,6S)-6-hydroxylasiodiplodin by means of spectroscopic analyses, the modified Mosher method, and chemical conversion. The compound showed potato micro-tuber-inducing activity at a concentration of 10(-4) M, using the culture of single-node segments of potato stems in vitro.

Preparation, characterization, and catalytic activity of zirconocene bridged on surface of silica gel

NASA Astrophysics Data System (ADS)

El Majdoub, Lotfia; Shi, Yasai; Yuan, Yuan; Zhou, Annan; Abutartour, Abubaker; Xu, Qinghong

2015-10-01

Zirconocene catalyst supported on silica gel was prepared for olefin polymerization by surface modification of calcined silica with SiCl4, and the reaction between the modified silica and cyclopentadienyl sodium and ZrCl4. The catalyst was characterized by using Fourier-transform infrared (FT-IR) spectrometer, thermogravimetric (TG), and differential scanning calorimetric (DSC) analytic spectrometer. It was found that the metallocene structure could be formed and connected on silica surface by chemical bond. Initial catalytic tests showed that the supported metallocene was catalytically active (methylaluminoxane as a cocatalyst), producing polymer with higher molecular weight than the metallocene just immobilized on the surface of silica gel.

Microbiological Transformations of Radionuclides in the Subsurface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, Matthew J.; Beliaev, Alex S.; Fredrickson, Jim K.

2010-01-04

Microorganisms are ubiquitous in subsurface environments although their populations sizes and metabolic activities can vary considerably depending on energy and nutrient inputs. As a result of their metabolic activities and the chemical properties of their cell surfaces and the exopolymers they produce, microorganisms can directly or indirectly facilitate the biotransformation of radionuclides, thus altering their solubility and overall fate and transport in the environment. Although biosorption to cell surfaces and exopolymers can be an important factor modifying the solubility of some radionuclides under specific conditions, oxidation state is often considered the single most important factor controlling their speciation and, therefore,more » environmental behavior.« less

Quantum chemical characterization of zwitterionic structures: Supramolecular complexes for modifying the wettability of oil-water-limestone system.

PubMed

Lopez-Chavez, Ernesto; Garcia-Quiroz, Alberto; Gonzalez-Garcia, Gerardo; Orozco-Duran, Gabriela E; Zamudio-Rivera, Luis S; Martinez-Magadan, José M; Buenrostro-Gonzalez, Eduardo; Hernandez-Altamirano, Raul

2014-06-01

In this work, we present a quantum chemical study pertaining to some supramolecular complexes acting as wettability modifiers of oil-water-limestone system. The complexes studied are derived from zwitterionic liquids of the types N'-alkyl-bis, N-alquenil, N-cycloalkyl, N-amyl-bis-beta amino acid or salts acting as sparkling agents. We studied two molecules of zwitterionic liquids (ZL10 and ZL13), HOMO and LUMO levels, and the energy gap between them, were calculated, as well as the electron affinity (EA) and ionization potential (IP), chemical potential, chemical hardness, chemical electrophilicity index and selectivity descriptors such Fukui indices. In this work, electrochemical comparison was realized with cocamidopropyl betaine (CPB), which is a structure zwitterionic liquid type, nowadays widely applied in enhanced recovery processes. Copyright © 2014 Elsevier Inc. All rights reserved.

ChemBrowser: a flexible framework for mining chemical documents.

PubMed

Wu, Xian; Zhang, Li; Chen, Ying; Rhodes, James; Griffin, Thomas D; Boyer, Stephen K; Alba, Alfredo; Cai, Keke

2010-01-01

The ability to extract chemical and biological entities and relations from text documents automatically has great value to biochemical research and development activities. The growing maturity of text mining and artificial intelligence technologies shows promise in enabling such automatic chemical entity extraction capabilities (called "Chemical Annotation" in this paper). Many techniques have been reported in the literature, ranging from dictionary and rule-based techniques to machine learning approaches. In practice, we found that no single technique works well in all cases. A combinatorial approach that allows one to quickly compose different annotation techniques together for a given situation is most effective. In this paper, we describe the key challenges we face in real-world chemical annotation scenarios. We then present a solution called ChemBrowser which has a flexible framework for chemical annotation. ChemBrowser includes a suite of customizable processing units that might be utilized in a chemical annotator, a high-level language that describes the composition of various processing units that would form a chemical annotator, and an execution engine that translates the composition language to an actual annotator that can generate annotation results for a given set of documents. We demonstrate the impact of this approach by tailoring an annotator for extracting chemical names from patent documents and show how this annotator can be easily modified with simple configuration alone.

Chemically and compositionally modified solid solution disordered multiphase nickel hydroxide positive electrode for alkaline rechargeable electrochemical cells

DOEpatents

Ovshinsky, Stanford R.; Corrigan, Dennis; Venkatesan, Srini; Young, Rosa; Fierro, Christian; Fetcenko, Michael A.

1994-01-01

A high capacity, long cycle life positive electrode for use in an alkaline rechargeable electrochemical cell comprising: a solid solution nickel hydroxide material having a multiphase structure that comprises at least one polycrystalline .gamma.-phase including a polycrystalline .gamma.-phase unit cell comprising spacedly disposed plates with at least one chemical modifier incorporated around the plates, the plates having a range of stable intersheet distances corresponding to a 2.sup.+ oxidation state and a 3.5.sup.+, or greater, oxidation state; and at least one compositional modifier incorporated into the solid solution nickel hydroxide material to promote the multiphase structure.

Inactivation of human DGAT2 by oxidative stress on cysteine residues

PubMed Central

Choi, Kwangman; Kwon, Eun Bin; Kang, Mingu; Kim, Dong-eun; Jeong, Hyejeong; Kim, Janghwan; Kim, Jong Heon; Kim, Mun Ock; Han, Sang-Bae

2017-01-01

Diacylglycerol acyltransferases (DGATs) have a crucial role in the biosynthesis of triacylglycerol (TG), the major storage form of metabolic energy in eukaryotic organisms. Even though DGAT2, one of two distinct DGATs, has a vital role in TG biosynthesis, little is known about the regulation of DGAT2 activity. In this study, we examined the role of cysteine and its oxidation in the enzymatic activity of human DGAT2 in vitro. Human DGAT2 activity was considerably inhibited not only by thiol-modifying reagents (NEM and IA) but also by ROS-related chemicals (H2O2 and β-lapachone), while human DGAT1 and GPAT1 were little affected. Particularly, ROS-related chemicals concomitantly induced intermolecular disulfide crosslinking of human DGAT2. Both the oxidative inactivation and disulfide crosslinking were almost completely reversed by the treatment with DTT, a disulfide-reducing agent. These results clearly demonstrated the significant role of ROS-induced intermolecular crosslinking in the inactivation of human DGAT2 and also suggested DGAT2 as a redox-sensitive regulator in TG biosynthesis. PMID:28700690

Decaleside: a new class of natural insecticide targeting tarsal gustatory sites

NASA Astrophysics Data System (ADS)

Rajashekar, Yallappa; Rao, Lingamallu J. M.; Shivanandappa, Thimmappa

2012-10-01

Natural sources for novel insecticide molecules hold promise in view of their eco-friendly nature, selectivity, and mammalian safety. Recent progress in understanding the biology of insect olfaction and taste offers new strategies for developing selective pest control agents. We have isolated two natural insecticidal molecules from edible roots of Decalepis hamiltonii named Decalesides I and II, which are novel trisaccharides, highly toxic to household insect pests and stored-product insects. We have experimentally shown that insecticidal activity requires contact with tarsi on the legs but is not toxic orally. The insecticidal activity of molecules is lost by hydrolysis, and various sugars modify toxic response, showing that the insecticidal activity is via gustatory sites on the tarsi. Selective toxicity to insects by virtue of their gustatory site of action and the mammalian safety of the new insecticides is inherent in their chemical structure with 1-4 or 1-1 α linkage that is easily hydrolyzed by digestive enzymes of mammals. Decalesides represent a new chemical class of natural insecticides with a unique mode of action targeting tarsal chemosensory/gustatory system of insects.

Research on the chemical mechanism in the polyacrylate latex modified cement system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Min; Wang, Rumin, E-mail: wangmin19@mail.nwpu.edu.cn; Zheng, Shuirong

2015-10-15

In this paper, the chemical mechanism in the polyacrylate latex modified cement system was investigated by Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS), gel permeation chromatography (GPC) and compact pH meter. All results have shown that the chemical reactions in the polyacrylate modified system can be divided into three stages. The hydration reactions of cement can produce large amounts of Ca(OH){sub 2} (calcium hydroxide) and lead the whole system to be alkali-rich and exothermic at the first stage. Subsequently, this environment can do great contributions to the hydrolysis of ester groups in the polyacrylate chains, resulting in themore » formation of carboxyl groups at the second stage. At the third stage, the final crosslinked network structure of the product was obtained by the reaction between the carboxyl groups in the polyacrylate latex chains and Ca(OH){sub 2}.« less

Electrodeposition of platinum and silver into chemically modified microporous silicon electrodes

PubMed Central

2012-01-01

Electrodeposition of platinum and silver into hydrophobic and hydrophilic microporous silicon layers was investigated using chemically modified microporous silicon electrodes. Hydrophobic microporous silicon enhanced the electrodeposition of platinum in the porous layer. Meanwhile, hydrophilic one showed that platinum was hardly deposited within the porous layer, and a film of platinum on the top of the porous layer was observed. On the other hand, the electrodeposition of silver showed similar deposition behavior between these two chemically modified electrodes. It was also found that the electrodeposition of silver started at the pore opening and grew toward the pore bottom, while a uniform deposition from the pore bottom was observed in platinum electrodeposition. These electrodeposition behaviors are explained on the basis of the both effects, the difference in overpotential for metal deposition on silicon and on the deposited metal, and displacement deposition rate of metal. PMID:22720690

Supersensitive fingerprinting of explosives by chemically modified nanosensors arrays.

PubMed

Lichtenstein, Amir; Havivi, Ehud; Shacham, Ronen; Hahamy, Ehud; Leibovich, Ronit; Pevzner, Alexander; Krivitsky, Vadim; Davivi, Guy; Presman, Igor; Elnathan, Roey; Engel, Yoni; Flaxer, Eli; Patolsky, Fernando

2014-06-24

The capability to detect traces of explosives sensitively, selectively and rapidly could be of great benefit for applications relating to civilian national security and military needs. Here, we show that, when chemically modified in a multiplexed mode, nanoelectrical devices arrays enable the supersensitive discriminative detection of explosive species. The fingerprinting of explosives is achieved by pattern recognizing the inherent kinetics, and thermodynamics, of interaction between the chemically modified nanosensors array and the molecular analytes under test. This platform allows for the rapid detection of explosives, from air collected samples, down to the parts-per-quadrillion concentration range, and represents the first nanotechnology-inspired demonstration on the selective supersensitive detection of explosives, including the nitro- and peroxide-derivatives, on a single electronic platform. Furthermore, the ultrahigh sensitivity displayed by our platform may allow the remote detection of various explosives, a task unachieved by existing detection technologies.

Supersensitive fingerprinting of explosives by chemically modified nanosensors arrays

NASA Astrophysics Data System (ADS)

Lichtenstein, Amir; Havivi, Ehud; Shacham, Ronen; Hahamy, Ehud; Leibovich, Ronit; Pevzner, Alexander; Krivitsky, Vadim; Davivi, Guy; Presman, Igor; Elnathan, Roey; Engel, Yoni; Flaxer, Eli; Patolsky, Fernando

2014-06-01

The capability to detect traces of explosives sensitively, selectively and rapidly could be of great benefit for applications relating to civilian national security and military needs. Here, we show that, when chemically modified in a multiplexed mode, nanoelectrical devices arrays enable the supersensitive discriminative detection of explosive species. The fingerprinting of explosives is achieved by pattern recognizing the inherent kinetics, and thermodynamics, of interaction between the chemically modified nanosensors array and the molecular analytes under test. This platform allows for the rapid detection of explosives, from air collected samples, down to the parts-per-quadrillion concentration range, and represents the first nanotechnology-inspired demonstration on the selective supersensitive detection of explosives, including the nitro- and peroxide-derivatives, on a single electronic platform. Furthermore, the ultrahigh sensitivity displayed by our platform may allow the remote detection of various explosives, a task unachieved by existing detection technologies.

Chemical characterization and antifungal activity of Origanum vulgare, Thymus vulgaris essential oils and carvacrol against Malassezia furfur.

PubMed

Vinciguerra, Vittorio; Rojas, Florencia; Tedesco, Viviana; Giusiano, Gustavo; Angiolella, Letizia

2018-05-04

The composition of the essential oils (EOs) of O. vulgare L. EO and T. vulgaris EO, were analyzed by GC and GC-MS. Antifungal activities of the EOs and its main component, carvacrol, were evaluated against 27 clinical isolates of Malassezia furfur. Minimum inhibitory concentrations (MICs) were measured according to the broth microdilution protocols by Clinical and Laboratory Standards Institute (CLSI) modified for Malassezia spp. EOs and carvacrol showed low MIC values ranged 450-900 μg/ml against M. furfur. No differences in EOs antifungal activity were observed in sensitive to resistant fluconazole isolates. The antifungal activity obtained showed O. vulgare EO, T. vulgaris EO and carvacrol, their compound, as potential antimicrobial agents against M. furfur, yeast associated with human mycoses.

18β-Glycyrrhetinic Acid Derivatives Possessing a Trihydroxylated A Ring Are Potent Gram-Positive Antibacterial Agents.

PubMed

Huang, Li-Rong; Hao, Xiao-Jiang; Li, Qi-Ji; Wang, Dao-Ping; Zhang, Jian-Xin; Luo, Heng; Yang, Xiao-Sheng

2016-04-22

The oleanane-type triterpene 18β-glycyrrhetinic acid (1) was modified chemically through the introduction of a trihydroxylated A ring and an ester moiety at C-20 to enhance its antibacterial activity. Compounds 22, 23, 25, 28, 29, 31, and 32 showed more potent inhibitory activity against Streptomyces scabies than the positive control, streptomycin. Additionally, the inhibitory activity of the most potent compound, 29, against Bacillus subtilis, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus was greater than that of the positive controls. The antibacterial mode of action of the active derivatives involved the regulation of the expression of genes associated with peptidoglycans, the respiratory metabolism, and the inherent virulence factors found in bacteria, as determined through a quantitative real-time reverse transcriptase PCR assay.

40 CFR 721.10149 - Carbon black, (3-methylphenyl)-modified, substituted (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Carbon black, (3-methylphenyl... Significant New Uses for Specific Chemical Substances § 721.10149 Carbon black, (3-methylphenyl)-modified... substance identified generically as carbon black, (3-methylphenyl)-modified, substituted (PMN P-07-522) is...

40 CFR 721.10150 - Carbon black, (4-methylphenyl)-modified, substituted (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Carbon black, (4-methylphenyl... Significant New Uses for Specific Chemical Substances § 721.10150 Carbon black, (4-methylphenyl)-modified... substance identified generically as carbon black, (4-methylphenyl)-modified, substituted (PMN P-07-523) is...

Optimization of process variables by response surface methodology for malachite green dye removal using lime peel activated carbon

NASA Astrophysics Data System (ADS)

Ahmad, Mohd Azmier; Afandi, Nur Syahidah; Bello, Olugbenga Solomon

2017-05-01

This study investigates the adsorptive removal of malachite green (MG) dye from aqueous solutions using chemically modified lime-peel-based activated carbon (LPAC). The adsorbent prepared was characterized using FTIR, SEM, Proximate analysis and BET techniques, respectively. Central composite design (CCD) in response surface methodology (RSM) was used to optimize the adsorption process. The effects of three variables: activation temperature, activation time and chemical impregnation ratio (IR) using KOH and their effects on percentage of dye removal and LPAC yield were investigated. Based on CCD design, quadratic models and two factor interactions (2FI) were developed correlating the adsorption variables to the two responses. Analysis of variance (ANOVA) was used to judge the adequacy of the model. The optimum conditions of MG dye removal using LPAC are: activation temperature (796 °C), activation time (1.0 h) and impregnation ratio (2.6), respectively. The percentage of MG dye removal obtained was 94.68 % resulting in 17.88 % LPAC yield. The percentage of error between predicted and experimental results for the removal of MG dye is 0.4 %. Model prediction was in good agreement with experimental results and LPAC was found to be effective in removing MG dye from aqueous solution.

Enzymatically Modified Starch Favorably Modulated Intestinal Transit Time and Hindgut Fermentation in Growing Pigs

PubMed Central

Newman, M. A.; Zebeli, Q.; Velde, K.; Grüll, D.; Molnar, T.; Kandler, W.; Metzler-Zebeli, B. U.

2016-01-01

Aside from being used as stabilizing agents in many processed foods, chemically modified starches may act as functional dietary ingredients. Therefore, development of chemically modified starches that are less digestible in the upper intestinal segments and promote fermentation in the hindgut receives considerable attention. This study aimed to investigate the impact of an enzymatically modified starch (EMS) on nutrient flow, passage rate, and bacterial activity at ileal and post-ileal level. Eight ileal-cannulated growing pigs were fed 2 diets containing 72% purified starch (EMS or waxy cornstarch as control) in a cross-over design for 10 d, followed by a 4-d collection of feces and 2-d collection of ileal digesta. On d 17, solid and liquid phase markers were added to the diet to determine ileal digesta flow for 8 h after feeding. Reduced small intestinal digestion after the consumption of the EMS diet was indicated by a 10%-increase in ileal flow and fecal excretion of dry matter and energy compared to the control diet (P<0.05). Moreover, EMS feeding reduced ileal transit time of both liquid and solid fractions compared to the control diet (P<0.05). The greater substrate flow to the large intestine with the EMS diet increased the concentrations of total and individual short-chain fatty acids (SCFA) in feces (P<0.05). Total bacterial 16S rRNA gene abundance was not affected by diet, whereas the relative abundance of the Lactobacillus group decreased (P<0.01) by 50% and of Enterobacteriaceae tended (P<0.1) to increase by 20% in ileal digesta with the EMS diet compared to the control diet. In conclusion, EMS appears to resemble a slowly digestible starch by reducing intestinal transit and increasing SCFA in the distal large intestine. PMID:27936165

In vitro extracellular recording and stimulation performance of nanoporous gold-modified multi-electrode arrays.

PubMed

Kim, Yong Hee; Kim, Gook Hwa; Kim, Ah Young; Han, Young Hwan; Chung, Myung-Ae; Jung, Sang-Don

2015-12-01

Nanoporous gold (Au) structures can reduce the impedance and enhance the charge injection capability of multi-electrode arrays (MEAs) used for interfacing neuronal networks. Even though there are various nanoporous Au preparation techniques, fabrication of MEA based on low-cost electro-codeposition of Ag:Au has not been performed. In this work, we have modified a Au MEA via the electro-codeposition of Ag:Au alloy, followed by the chemical etching of Ag, and report on the in vitro extracellular recording and stimulation performance of the nanoporous Au-modified MEA. Ag:Au alloy was electro-codeposited on a bilayer lift-off resist sputter-deposition passivated Au MEA followed by chemical etching of Ag to form a porous Au structure. The porous Au structure was analyzed by scanning electron microscopy and tunneling electron microscopy and found to have an interconnected nanoporous Au structure. The impedance value of the nanoporous Au-modified MEA is 15.4 ± 0.55 kΩ at 1 kHz, accompanied by the base noise V rms of 2.4 ± 0.3 μV. The charge injection limit of the nanoporous Au-modified electrode estimated from voltage transient measurement is approximately 1 mC cm(-2), which is comparable to roughened platinum and carbon nanotube electrodes. The charge injection capability of the nanoporous Au-modified MEA was confirmed by observing stimulus-induced spikes at above 0.2 V. The nanoporous Au-modified MEA showed mechanical durability upon ultrasonic treatment for up to an hour. Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus-response relationship of cultured neuronal networks.

In vitro extracellular recording and stimulation performance of nanoporous gold-modified multi-electrode arrays

NASA Astrophysics Data System (ADS)

Kim, Yong Hee; Kim, Gook Hwa; Kim, Ah Young; Han, Young Hwan; Chung, Myung-Ae; Jung, Sang-Don

2015-12-01

Objective. Nanoporous gold (Au) structures can reduce the impedance and enhance the charge injection capability of multi-electrode arrays (MEAs) used for interfacing neuronal networks. Even though there are various nanoporous Au preparation techniques, fabrication of MEA based on low-cost electro-codeposition of Ag:Au has not been performed. In this work, we have modified a Au MEA via the electro-codeposition of Ag:Au alloy, followed by the chemical etching of Ag, and report on the in vitro extracellular recording and stimulation performance of the nanoporous Au-modified MEA. Approach. Ag:Au alloy was electro-codeposited on a bilayer lift-off resist sputter-deposition passivated Au MEA followed by chemical etching of Ag to form a porous Au structure. Main results. The porous Au structure was analyzed by scanning electron microscopy and tunneling electron microscopy and found to have an interconnected nanoporous Au structure. The impedance value of the nanoporous Au-modified MEA is 15.4 ± 0.55 kΩ at 1 kHz, accompanied by the base noise V rms of 2.4 ± 0.3 μV. The charge injection limit of the nanoporous Au-modified electrode estimated from voltage transient measurement is approximately 1 mC cm-2, which is comparable to roughened platinum and carbon nanotube electrodes. The charge injection capability of the nanoporous Au-modified MEA was confirmed by observing stimulus-induced spikes at above 0.2 V. The nanoporous Au-modified MEA showed mechanical durability upon ultrasonic treatment for up to an hour. Significance. Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus-response relationship of cultured neuronal networks.

Development of combinations of chemically modified vegetable oils as pork backfat substitutes in sausages formulation.

PubMed

Ospina-E, Juan Camilo; Cruz-S, Adriana; Pérez-Alvarez, José Angel; Fernández-López, Juana

2010-03-01

Today's consumers look for foods which provide nutrition and pleasure, while safeguarding their health, the result of which is that they increasingly avoid foods containing cholesterol and saturated and trans fatty acids. Chemically modified vegetable oils can help tailor meat products to meet this growing need and at the same time fulfil the technological needs of the meat processing industry. In this study, 16 backfat samples were characterised for their solid fat content (SFC) and melting point and these characteristics were used to design a mixture of chemically modified vegetable oils for use as a pork fat substitute for elaborating sausages. The mixtures were prepared with different vegetable oils bearing in mind with stearic acid content due to its close correlation with the SFC. The backfat was characterised as a function of its SFC and some modified vegetable oil mixtures were proposed, which led to a 10-20% diminution in saturated fatty acids and with a melting point similar to those observed in the backfat. The fatty acid profile pointed to a polyunsaturated/saturated fatty acids ratio higher than 0.4, and an n-6/n-3 fatty acid ratio of less than 4 in both modified vegetable oil mixtures proposed. Copyright 2009 Elsevier Ltd. All rights reserved.