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Sample records for limon chemical modification

  1. Seasonal variations of antimicrobial activity and chemical composition of essential oils extracted from three Citrus limon L. Burm. cultivars.

    Science.gov (United States)

    Settanni, L; Randazzo, W; Palazzolo, E; Moschetti, M; Aleo, A; Guarrasi, V; Mammina, C; San Biagio, P L; Marra, F P; Moschetti, G; Germanà, M A

    2014-01-01

    In order to investigate the seasonal variations of antimicrobial properties and chemical composition of essential oils (EOs), three different cultivars of Citrus limon L. Burm. spp. (Femminello Santa Teresa, Monachello and Femminello Continella) were collected at 6-week intervals, from December 2012 to April 2013, for a total of four harvests. The EOs were extracted from lemon peel by hydro-distillation. The antimicrobial activity, tested by paper disc diffusion method, was evaluated against common food-related pathogenic bacteria (Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica and Enterobacter spp.). EOs were more effective against Gram-positive than Gram-negative bacteria at each collection time, but a strong strain dependence was evidenced. Monachello EOs showed the highest inhibition power. The chemical characterisation of the EOs performed by gas chromatography/mass spectrometry identified from 36 to 42 molecules. The chemical difference registered among samples and seasons may explain the different antimicrobial efficacies recorded.

  2. Chemical guide parameters for Spanish lemon (Citrus limon (L.) Burm.) juices.

    Science.gov (United States)

    Lorente, José; Vegara, Salud; Martí, Nuria; Ibarz, Albert; Coll, Luís; Hernández, Julio; Valero, Manuel; Saura, Domingo

    2014-11-01

    To contribute for setting reference guideline for commercial juice extracted from the Spanish lemon varieties, chemical composition of 92 direct and 92 reconstituted samples were investigated. In direct lemon juice, titratable acidity was 52.4 g/L, being the citric acid the main component. Glucose, fructose and sucrose concentrations were 7.9, 7.3 and 4.5 g/L, respectively. Predominant mineral was potassium (1264.2mg/L), followed by phosphorous (306 mg/L), calcium (112 mg/L) and magnesium (92.6 mg/L). Hesperidin ranged from 257 to 484.8 mg/L, while water soluble pectins varied between 164.8 and 550 mg/L. Similar values were obtained in reconstituted lemon juice. There are different parameters that did not reach or exceeded the limits proposed by the European Association of the Industry of Juices and Nectars. These levels should be taken into account to modify the present reference guideline and that Spanish lemon juices are not discarded for to have lower or bigger values.

  3. Chemical Protein Modification through Cysteine.

    Science.gov (United States)

    Gunnoo, Smita B; Madder, Annemieke

    2016-04-01

    The modification of proteins with non-protein entities is important for a wealth of applications, and methods for chemically modifying proteins attract considerable attention. Generally, modification is desired at a single site to maintain homogeneity and to minimise loss of function. Though protein modification can be achieved by targeting some natural amino acid side chains, this often leads to ill-defined and randomly modified proteins. Amongst the natural amino acids, cysteine combines advantageous properties contributing to its suitability for site-selective modification, including a unique nucleophilicity, and a low natural abundance--both allowing chemo- and regioselectivity. Native cysteine residues can be targeted, or Cys can be introduced at a desired site in a protein by means of reliable genetic engineering techniques. This review on chemical protein modification through cysteine should appeal to those interested in modifying proteins for a range of applications.

  4. Chemical Modification of Food Proteins

    Institute of Scientific and Technical Information of China (English)

    Allaoua Achouri; Wang Zhang; Xu Shiying

    1999-01-01

    Acylation has been shown to be an effective tool for improving surface functional properties of plant proteins.Soy bean protein has been extensively modified through chemical and enzymatic treatments. Their effectiveness lies in their high nutritional value and low cost, which promote their use as ingredients for the formulation of food products.This paper reports a complete review of chemical modification of various proteins from plant and animal sources. The nutritive and toxicological aspects through in vitro and in vivo tests are also described.

  5. Evaluation of the chemical composition and antioxidant activity of Citrus limon essential oil and its application in margarine preservation

    Directory of Open Access Journals (Sweden)

    Louiza HIMED

    2016-08-01

    Full Text Available Essential oils are aromatic oil liquids obtained from various plant parts. The growing interest in the substitution of synthetic antioxidant agents by natural ones has fostered research on vegetable sources and the screening of plant materials in order to identify new compounds. The study aims to evaluate the use of essential oil extract by cold pression of Citrus limon (Lisbon variety as a substitute of Tocoblend (mixture of α, β, γ and δ-tocopherol used as antioxidant in margarine preservation. The major constituents of the essential oil extract Identified were Limonene (66.75% followed by β-Pinene (13.92% and γ-Terpinene (3.10%. In both DPPH scavenging and bleachability of β-carotene in linoleic acid system assays, the essential oil extract exhibited the highest activity compared to the Tocoblend. Tests conducted at pilot scale showed that the margarine elaborated with essential oil extract was more resistant to oxidation than the margarine reference with Tocoblend. In addition, the physicochemical properties were not modified.

  6. Chemical Profile and Antioxidant Properties of Extracts and Essential Oils from Citrus × limon (L.) Burm. cv. Femminello Comune.

    Science.gov (United States)

    Loizzo, Monica Rosa; Tundis, Rosa; Bonesi, Marco; Sanzo, Giuseppe Di; Verardi, Alessandra; Lopresto, Catia Giovanna; Pugliese, Alessandro; Menichini, Francesco; Balducchi, Roberto; Calabrò, Vincenza

    2016-05-01

    Citrus × limon cv. Femminello Comune (Rutaceae) from Rocca Imperiale (Italy), one of the six Protected Geographical Indication (PGI) Italian lemon crops, has been recently received renewed interest. In this work, fresh and dried peels and leaves were extracted by hydrodistillation, supercritical fluid extraction (SFE), and Soxhlet apparatus. Chemical profile was assessed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). Except for leaves extracts obtained by Soxhlet apparatus, the monoterpene hydrocarbons fraction dominated. Limonene, γ-terpinene, and β-pinene were the main identified compounds. The antioxidant activity was investigated using different in vitro assays namely 2,2-diphenyl-1-picrylhydrazyl (DPPH), ABTS, ferric reducing ability power (FRAP), and β-carotene bleaching test. In DPPH test, the essential oil obtained by hydrodistillation of fresh peel exhibited the highest activity (IC50 of 1.17 mg/ml). Leaves extracted by SFE showed a good activity in both DPPH and β-carotene bleaching test with IC50 values of 2.20 and 6.66 mg/ml, respectively. Monoterpene hydrocarbons fraction exhibited a positive Pearson's correlation coefficient with all antioxidant assays. Leaves, often considered waste material, should be considered from a different point because they represent a matrix of indisputable interest. © 2016 Verlag Helvetica Chimica Acta AG, Zürich.

  7. Chemical biology approaches for studying posttranslational modifications.

    Science.gov (United States)

    Yang, Aerin; Cho, Kyukwang; Park, Hee-Sung

    2017-09-13

    Posttranslational modification (PTM) is a key mechanism for regulating diverse protein functions, and thus critically affects many essential biological processes. Critical for systematic study of the effects of PTMs is the ability to obtain recombinant proteins with defined and homogenous modifications. To this end, various synthetic and chemical biology approaches, including genetic code expansion and protein chemical modification methods, have been developed. These methods have proven effective for generating site-specific authentic modifications or structural mimics, and have demonstrated their value for in vitro and in vivo functional studies of diverse PTMs. This review will discuss recent advances in chemical biology strategies and their application to various PTM studies.

  8. Chemical Modifications of Starch: Microwave Effect

    OpenAIRE

    Kamila Lewicka; Przemysław Siemion; Piotr Kurcok

    2015-01-01

    This paper presents basic methods of starch chemical modification, the effect of microwave radiation on the modification process, and the physicochemical properties of starch. It has been shown that the modifications contribute to improvement of the material performance and likewise to significant improvement of its mechanical properties. As a result, more and more extensive use of starch is possible in various industries. In addition, methods of oxidized starch and starch esters preparation ...

  9. Chemical Modifications of Starch: Microwave Effect

    Directory of Open Access Journals (Sweden)

    Kamila Lewicka

    2015-01-01

    Full Text Available This paper presents basic methods of starch chemical modification, the effect of microwave radiation on the modification process, and the physicochemical properties of starch. It has been shown that the modifications contribute to improvement of the material performance and likewise to significant improvement of its mechanical properties. As a result, more and more extensive use of starch is possible in various industries. In addition, methods of oxidized starch and starch esters preparation are discussed. Properties of microwave radiation and its impact on starch (with particular regard to modifications described in literature are characterized.

  10. Compositional, physical and chemical modification of polylactide

    Directory of Open Access Journals (Sweden)

    M. Żenkiewicz

    2010-11-01

    Full Text Available Purpose: The purpose of this article was to review some of the modification methods applied to improve mechanical, barrier and/or surface properties of polylactide (PLA.Design/methodology/approach: The presented modification methods were classified into three groups due to the dominant role of compositional, physical or chemical factor effecting the most PLA properties.Findings: It was found that incorporation of small amounts of montmorillonite up to 5% leads to formation of a nanocomposite with enhanced tensile strength and improved barrier properties. Corona treatment of pure PLA and PLA contained MMT nanofiller causes a significant decrease in the water contact angle and does not essentially affect the diiodomethane contact angle. This treatment leads to an increase in surface free energy that is much more significant for pure PLA than for PLA containing MMT nanofiller. It was also found that with increasing number up to 1000 of laser pulses of energies 5 mJ/cm2 an increase in surface free energy was observed, while the next laser pulses caused decrease of this energy. The determination and comparison of the influence of 3 wt.% of trimethylopropane trimethacylate (TMPTA and 3 wt.% of trially isocyanurate (TAIC crosslinking agents on the thermomechanical properties of electron beam irradiated PLA was reported.Research limitations/implications: A number of various modification methods are widely reported in literature. In this article a review of only such modification methods is presented, which are in line with the newest trends in polymer industry and science.Practical implications: There are a number of PLA properties, which need to be improved to satisfy specific application conditions. For that reasons researches are leading to find suitable modification methods to improve selected properties of PLA.Originality/value: This article presents some of modification methods, which are in line with the newest trends in polymer industry and

  11. Chemical composition of the essential oils of variegated pink-fleshed lemon (Citrus x limon L. Burm. f.) and their anti-inflammatory and antimicrobial activities.

    Science.gov (United States)

    Hamdan, Dalia; Ashour, Mohamed L; Mulyaningsih, Sri; El-Shazly, Assem; Wink, Michael

    2013-01-01

    The volatile secondary metabolites of essential oils from fruit peel and leaves of variegated pink-fleshed lemon (Citrus x limon) were investigated using GLC and GLC-MS (gas-liquid chromatography-mass spectroscopy). Altogether 141 compounds were identified and quantified, accounting for 99.59% and 96.33% of the total hydrodistilled peel and leaf oil, respectively. Limonene occurred in higher amounts in fruit peel (52.73%) than in leaf oil (29.13%). Neral (12.72%), neryl acetate (8.53%), p-menth-1-en-7-al (4.63%), beta-pinene (6.35%), and nerol (4.42%) were the most abundant constituents in leaf oil, whereas gamma-terpinene (9.88%), beta-pinene (7.67%), geranial (4.44%), and neral (3.64%) dominated in the fruit peel oil. The antioxidant, anti-inflammatory, antitrypanosomal, and antimicrobial activities of the fruit peel essential oil were evaluated. The oil had a low antioxidant activity with an IC50 value of (26.66 +/- 2.07) mg/ml as compared to the efficient antioxidant ascorbic acid [IC50 (16.32 +/- 0.16) microg/ml]. The oil moderately inhibited soybean 5-lipoxygenase (5-LOX) with an IC50 value of (32.05 +/- 3.91) microg/ml and had moderate antitrypanosomal activity [IC50 (60.90 +/- 0.91) microg/ml]. In addition, moderate antimicrobial activities were detected against Gram-positive bacteria (Bacillus subtilis, Staphylococcus capitis, Micrococcus luteus), one Gram-negative bacterium (Pseudomonas fluorescens), and yeasts (Saccharomyces cerevisiae, Candida parapsilosis).

  12. Gold Nanowires and Their Chemical Modifications

    Science.gov (United States)

    Häkkinen, Hannu; Barnett, Robert N.; Landman, Uzi

    2000-03-01

    Atomic structure, electronic structure, and ballistic transport in thin gold nanowires at their final stages before break-up, recently imaged by high-resolution electron microscopy,(H. Ohnishi et al., Nature 395), 780 (1998) are investigated with density functional simulations.(H. Häkkinen et al., J. Phys. Chem. B 103), 8814 (1999) We discuss stretching mechanisms leading to elongated chain-like structures showing dimerization akin to a Peierls transition and retaining conductance close to unity for stretching lengths that exceed considerably a typical interatomic bond length. We also demonstrate a chemical modification of the wire via adsorption of a methyl thiol molecule and discuss its effects on the structure and conductance.

  13. Chemical and structural effects of base modifications in messenger RNA

    Science.gov (United States)

    Harcourt, Emily M.; Kietrys, Anna M.; Kool, Eric T.

    2017-01-01

    A growing number of nucleobase modifications in messenger RNA have been revealed through advances in detection and RNA sequencing. Although some of the biochemical pathways that involve modified bases have been identified, research into the world of RNA modification -- the epitranscriptome -- is still in an early phase. A variety of chemical tools are being used to characterize base modifications, and the structural effects of known base modifications on RNA pairing, thermodynamics and folding are being determined in relation to their putative biological roles.

  14. Chemical Modification Methods of Nanoparticles of Silicon Carbide Surface

    Directory of Open Access Journals (Sweden)

    Anton S. Yegorov

    2015-09-01

    Full Text Available silicon carbide exhibits exceptional properties: high durability, high thermal conductivity, good heat resistance, low thermal expansion factor and chemical inactivity. Reinforcement with silicon carbide nanoparticles increases polymer’s tensile strength and thermal stability.Chemical methods of modification of the silicon carbide surface by means of variety of reagents from ordinary molecules to macromolecular polymers are reviewed in the review.The structure of silicon carbide surface layer and the nature of modificator bonding with the surface of SiC particles are reviewed. General examples of surface modification methodologies and composite materials with the addition of modified SiC are given.

  15. Effects of citrus limon essential oil (Citrus limon L. on cytomorphometric changes of Candida albicans

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    Rina Prabajati

    2017-03-01

    Full Text Available Background: The most common fungal infection found in oral cavity is oral candidiasis, largely caused by Candida species, particularly Candida albicans (C. albicans. Candida infection can get worse since it is difficult to be treated and resistant with antifungal drugs. Therefore, new drugs and compounds as well as alternative therapies involving natural sources that have antifungal activities have continually been developed. Limonene, β-pinene, and ɣ-terpinene contained in Citrus limon essential oil have been known to have quite good antifungal activities against C. albicans. Purpose: This research aimed to examine and analyze the effects of Citrus limon essential oil on cytomorphometric changes of C. albicans. Method: The research used post test only control group design. Based on the results of the pre-elementary research on antifungal activities of Citrus limon essential oil against C. albicans, Citrus limon essential oil used in this research was on concentrations of 1.56%, 1.37%, 1.17%, 0.98%, and 0.78%. Citrus limon essential oil by C. albicans inoculum and incubated for 24 hours and 48 hours. After the incubation, those C. albicans cells were fixed, dried, and then observed using a scanning electron microscopy. Result: The most effective concentrations of Citrus limon essential oil triggering cytomorphometric changes of Candida albicans were at 1.37% and 1.56% with the incubation period of 48 hours. Conclusion: C. albicans can undergo necrosis process through cytomorphometric changes after the administration of Citrus limon essential oil at concentrations of 1.56% and 1.37% with the incubation period of 48 hours.

  16. Chemical modification of soybean oil for lubricant

    Energy Technology Data Exchange (ETDEWEB)

    Duan Shijie; Mao Zongqiang [Tsinghua Univ., INET, BJ (China)

    2008-07-01

    This paper presents a series of structural modifications of soybean oils for lubricant. The reaction was monitored and products were confirmed by NMR and FTIR. The structural modification is carried out in four stages, (1) synthesis of soybean oil isooctyl ester from soybean oil; (2) synthesis of epoxy-soybean oil isooctyl ester from soybean oil isooctyl ester; (3) synthesis of hydroxylated products from epoxy soybean oil isooctyl ester with fatty acid; (4) esterification of the hydroxylated product with anhydride. Rheological behaviour of the products was measured. Pour points of the products (3) were observed as low as -24 C (lauric acid) and -15 C (isooctanoic acid) respectively. When the hydroxyl groups in the products were esterified with and acid anhydride, the pour points were became higher, which were -21 C (lauric acid) and -6 C (isooctanoic acid) without pour point depressant, and -27 C (lauric acid) and -24 C (isooctanoic acid) with 1% of pour point depressant respectively. The products have suitable viscosity and viscosity index, and the viscosity indices are all above 100. (orig.)

  17. Chemical modifications of liquid natural rubber

    Science.gov (United States)

    Azhar, Nur Hanis Adila; Rasid, Hamizah Md; Yusoff, Siti Fairus M.

    2016-11-01

    Liquid natural rubber (LNR) was synthesized via photosentisized degradation of natural rubber (NR). LNR was modified into epoxidized liquid natural rubber (LENR) and hydroxylated liquid natural rubber (LNR-OH) using Na2WO4/CH3COOH/H2O2 catalytic system. Chemical structures of LNR and modified LNRs were characterized using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and 1H Nuclear Magnetic Resonance (NMR) spectroscopies. Integration of 1H NMR was used to calculate the epoxy content (%) of LENR. 1H NMR detected the formation of LNR-OH after prolonged heating and increased of catalyst in oxidation reaction.

  18. Chemical modification of antifungal polyene macrolide antibiotics

    Science.gov (United States)

    Solovieva, S. E.; Olsufyeva, E. N.; Preobrazhenskaya, M. N.

    2011-02-01

    The review summarizes advances in the methods for the synthesis of polyene antibiotics (amphotericin B, partricin A, etc.) and investigations of the structure-activity relationship made in the last 15 years. State-of-the-art approaches based on the combination of the chemical synthesis and genetic engineering are considered. Emphasis is given to the design of semisynthetic antifungal agents against chemotherapy-resistant pathogens having the highest therapeutic indices. Recent results of research on the mechanisms of action of polyenes are outlined.

  19. Chemical modification of antifungal polyene macrolide antibiotics

    Energy Technology Data Exchange (ETDEWEB)

    Solovieva, S E; Olsufyeva, E N; Preobrazhenskaya, M N [G.F.Gause Institute of New Antibiotics, Russian Academy of Medical Sciences (Russian Federation)

    2011-02-28

    The review summarizes advances in the methods for the synthesis of polyene antibiotics (amphotericin B, partricin A, etc.) and investigations of the structure-activity relationship made in the last 15 years. State-of-the-art approaches based on the combination of the chemical synthesis and genetic engineering are considered. Emphasis is given to the design of semisynthetic antifungal agents against chemotherapy-resistant pathogens having the highest therapeutic indices. Recent results of research on the mechanisms of action of polyenes are outlined.

  20. Behavioral effects of Citrus limon in rats.

    Science.gov (United States)

    Khan, Rafeeq Alam; Riaz, Azra

    2015-04-01

    Anxiety and depression are increasing worldwide, however these disorders may be managed by making healthier changes is dietary pattern, since there are evidences that diet rich in antioxidants and vitamins help reduce anxiety and depression. Hence present study was designed to evaluate the behavioral effects of Citrus limon in rats at three different doses i.e. 0.2, 0.4 and 0.6 ml/kg considered as low, moderate and high doses. Anxiolytic and antidepressant activities were specifically assessed twice during 15 days using open field test, elevated plus maze and forced swimming test. In open field test C. limon, revealed increase in distance travelled, number of central entries and number of rearing's at moderate dose, while in the elevated plus maze, number of open arm entries were found to be increased. Whereas in forced swimming test, there was decrease in duration of immobility and increase in duration of climbing. Thus results of present study suggest that C. limon at moderate dose have anxiolytic effect.

  1. Structures of antimutagenic constituents in the peels of Citrus limon.

    Science.gov (United States)

    Matsumoto, Takahiro; Takahashi, Kazuki; Kanayama, Sumire; Nakano, Yuka; Imai, Hiromi; Kibi, Masumi; Imahori, Daisuke; Hasei, Tomohiro; Watanabe, Tetsushi

    2017-07-11

    The methanolic extracts from the peels of Citrus limon were found to show antimutagenic effects against 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole, and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in the Ames test. From the methanolic extracts, four new coumarins (wakayamalimonol A-D) and a new furanocoumarin (wakayamalimonol E) were isolated together with fifteen known compounds. The absolute stereostructures of the new compounds were determined by chemical synthesis and the modified Mosher's method. Among the isolated constituents, coumarins, furanocoumarins, and limonoids showed antimutagenic effects in the Ames test. One of the major constituent, limonin, showed significant antimutagenic effects against mitomycinC and PhIP in the micronucleus test in vivo.

  2. Chemical Modification Methods of Nanoparticles of Silicon Carbide Surface

    OpenAIRE

    Anton S. Yegorov; Vitaly S. Ivanov; Alexey V. Antipov; Alyona I. Wozniak; Kseniia V. Tcarkova.

    2015-01-01

    silicon carbide exhibits exceptional properties: high durability, high thermal conductivity, good heat resistance, low thermal expansion factor and chemical inactivity. Reinforcement with silicon carbide nanoparticles increases polymer’s tensile strength and thermal stability.Chemical methods of modification of the silicon carbide surface by means of variety of reagents from ordinary molecules to macromolecular polymers are reviewed in the review.The structure of silicon carbide surface layer...

  3. Selective chemical modification of DNA with alkoxy- and benzyloxyamines

    NARCIS (Netherlands)

    Gjonaj, Lorina; Roelfes, Gerard

    2015-01-01

    A new method for the selective chemical modification of DNA at cytosine nucleobases using alkoxy- and benzyloxyamines is presented. It is shown that in particular benzyloxyamines are effective DNA modifying agents, giving rise to almost exclusive formation of the mono addition products. By using a

  4. Chemical modification/grafting of mesoporous alumina with polydimethylsiloxane (PDMS)

    NARCIS (Netherlands)

    Pinheiro de Melo, A.F.; Nijmeijer, A.; Sripathi, V.G.P.; Winnubst, A.J.A.

    2015-01-01

    A method for polydimethylsiloxane grafting of alumina powders is described which involves chemical modification of the surface of mesoporous (5 nm) γ-alumina flakes with a linker (3-aminopropyltriethoxysilane: APTES), either by a solution phase (SPD) or a vapour phase (VPD) reaction, followed by PDM

  5. Chemical modification/grafting of mesoporous alumina with polydimethylsiloxane (PDMS)

    NARCIS (Netherlands)

    Pinheiro de Melo, A.F.; Nijmeijer, Arian; Sripathi, V.G.P.; Winnubst, Aloysius J.A.

    2015-01-01

    A method for polydimethylsiloxane grafting of alumina powders is described which involves chemical modification of the surface of mesoporous (5 nm) γ-alumina flakes with a linker (3-aminopropyltriethoxysilane: APTES), either by a solution phase (SPD) or a vapour phase (VPD) reaction, followed by

  6. Recent Advances in Chemical Modification of Peptide Nucleic Acids

    Directory of Open Access Journals (Sweden)

    Eriks Rozners

    2012-01-01

    Full Text Available Peptide nucleic acid (PNA has become an extremely powerful tool in chemistry and biology. Although PNA recognizes single-stranded nucleic acids with exceptionally high affinity and sequence selectivity, there is considerable ongoing effort to further improve properties of PNA for both fundamental science and practical applications. The present paper discusses selected recent studies that improve on cellular uptake and binding of PNA to double-stranded DNA and RNA. The focus is on chemical modifications of PNA's backbone and heterocyclic nucleobases. The paper selects representative recent studies and does not attempt to provide comprehensive coverage of the broad and vibrant field of PNA modification.

  7. Chemical posttranslational modification of phage-displayed peptides.

    Science.gov (United States)

    Ng, Simon; Tjhung, Katrina F; Paschal, Beth M; Noren, Christopher J; Derda, Ratmir

    2015-01-01

    Phage-displayed peptide library has fueled the discovery of novel ligands for diverse targets. A new type of phage libraries that displays not only linear and disulfide-constrained cyclic peptides but moieties that cannot be encoded genetically or incorporated easily by bacterial genetic machinery has emerged recently. Chemical posttranslational modification of phage library is one of the simplest approaches to encode nonnatural moieties. It confers the library with new functionality and makes it possible to select and evolve molecules with properties not found in the peptides, for instance, glycopeptides recognized by carbohydrate-binding protein and peptides with photoswitching capability. To this end, we describe the newly emerging techniques to chemically modify the phage library and quantify the efficiency of the reaction with a biotin-capture assay. Finally, we provide the methods to construct N-terminal Ser peptide library that allows site-selective modification of phage.

  8. Surface chemical modification of fullerene by mechanochemical treatment

    Science.gov (United States)

    Todorović Marković, B.; Jokanović, V.; Jovanović, S.; Kleut, D.; Dramićanin, M.; Marković, Z.

    2009-06-01

    In this study different encapsulating agents have been used for chemical modification of fullerenes. Fullerenes have reacted with tetrahydrofuran, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and ethylene vinyl acetate-ethylene vinyl versatate at room temperature under mechanical milling. The obtained powder has been dispersed in water by ultrasonication. The fullerene based colloids have been characterized by UV-vis, FTIR, Raman spectroscopy and atomic force microscopy. FTIR and Raman analysis have shown the presence of C 60 after surface functionalization.

  9. A Viral Platform for Chemical Modification and Multivalent Display

    Directory of Open Access Journals (Sweden)

    Peabody David S

    2003-07-01

    Full Text Available Abstract The ability to chemically modify the surfaces of viruses and virus-like particles makes it possible to confer properties that make them potentially useful in biotechnology, nanotechnology and molecular electronics applications. RNA phages (e.g. MS2 have characteristics that make them suitable scaffolds to which a variety of substances could be chemically attached in definite geometric patterns. To provide for specific chemical modification of MS2's outer surface, cysteine residues were substituted for several amino acids present on the surface of the wild-type virus particle. Some substitutions resulted in coat protein folding or stability defects, but one allowed the production of an otherwise normal virus-like particle with an accessible sulfhydryl on its surface.

  10. Surface chemical modification for exceptional wear life of MEMS materials

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    R. Arvind Singh

    2011-12-01

    Full Text Available Micro-Electro-Mechanical-Systems (MEMS are built at micro/nano-scales. At these scales, the interfacial forces are extremely strong. These forces adversely affect the smooth operation and cause wear resulting in the drastic reduction in wear life (useful operating lifetime of actuator-based devices. In this paper, we present a surface chemical modification method that reduces friction and significantly extends the wear life of the two most popular MEMS structural materials namely, silicon and SU-8 polymer. The method includes surface chemical treatment using ethanolamine-sodium phosphate buffer, followed by coating of perfluoropolyether (PFPE nanolubricant on (i silicon coated with SU-8 thin films (500 nm and (ii MEMS process treated SU-8 thick films (50 μm. After the surface chemical modification, it was observed that the steady-state coefficient of friction of the materials reduced by 4 to 5 times and simultaneously their wear durability increased by more than three orders of magnitude (> 1000 times. The significant reduction in the friction coefficients is due to the lubrication effect of PFPE nanolubricant, while the exceptional increase in their wear life is attributed to the bonding between the -OH functional group of ethanolamine treated SU-8 thin/thick films and the -OH functional group of PFPE. The surface chemical modification method acts as a common route to enhance the performance of both silicon and SU-8 polymer. It is time-effective (process time ≤ 11 min, cost-effective and can be readily integrated into MEMS fabrication/assembly processes. It can also work for any kind of structural material from which the miniaturized devices are/can be made.

  11. Memory boosting effect of Citrus limon, Pomegranate and their combinations

    National Research Council Canada - National Science Library

    Riaz, Azra; Khan, Rafeeq Alam; Algahtani, Hussein A

    2014-01-01

    Memory is greatly influenced by factors like food, stress and quality of sleep, hence present study was designed to evaluate the effect of Citrus limon and Pomegranate juices on memory of mice using...

  12. Marine derived polysaccharides for biomedical applications: chemical modification approaches.

    Science.gov (United States)

    d'Ayala, Giovanna Gomez; Malinconico, Mario; Laurienzo, Paola

    2008-09-03

    Polysaccharide-based biomaterials are an emerging class in several biomedical fields such as tissue regeneration, particularly for cartilage, drug delivery devices and gelentrapment systems for the immobilization of cells. Important properties of the polysaccharides include controllable biological activity, biodegradability, and their ability to form hydrogels. Most of the polysaccharides used derive from natural sources; particularly, alginate and chitin, two polysaccharides which have an extensive history of use in medicine, pharmacy and basic sciences, and can be easily extracted from marine plants (algae kelp) and crab shells, respectively. The recent rediscovery of poly-saccharidebased materials is also attributable to new synthetic routes for their chemical modification, with the aim of promoting new biological activities and/or to modify the final properties of the biomaterials for specific purposes. These synthetic strategies also involve the combination of polysaccharides with other polymers. A review of the more recent research in the field of chemical modification of alginate, chitin and its derivative chitosan is presented. Moreover, we report as case studies the results of our recent work concerning various different approaches and applications of polysaccharide-based biomaterials, such as the realization of novel composites based on calcium sulphate blended with alginate and with a chemically modified chitosan, the synthesis of novel alginate-poly(ethylene glycol) copolymers and the development of a family of materials based on alginate and acrylic polymers of potential interest as drug delivery systems.

  13. Marine Derived Polysaccharides for Biomedical Applications: Chemical Modification Approaches

    Directory of Open Access Journals (Sweden)

    Paola Laurienzo

    2008-09-01

    Full Text Available Polysaccharide-based biomaterials are an emerging class in several biomedical fields such as tissue regeneration, particularly for cartilage, drug delivery devices and gelentrapment systems for the immobilization of cells. Important properties of the polysaccharides include controllable biological activity, biodegradability, and their ability to form hydrogels. Most of the polysaccharides used derive from natural sources; particularly, alginate and chitin, two polysaccharides which have an extensive history of use in medicine, pharmacy and basic sciences, and can be easily extracted from marine plants (algae kelp and crab shells, respectively. The recent rediscovery of poly-saccharidebased materials is also attributable to new synthetic routes for their chemical modification, with the aim of promoting new biological activities and/or to modify the final properties of the biomaterials for specific purposes. These synthetic strategies also involve the combination of polysaccharides with other polymers. A review of the more recent research in the field of chemical modification of alginate, chitin and its derivative chitosan is presented. Moreover, we report as case studies the results of our recent work concerning various different approaches and applications of polysaccharide-based biomaterials, such as the realization of novel composites based on calcium sulphate blended with alginate and with a chemically modified chitosan, the synthesis of novel alginate-poly(ethylene glycol copolymers and the development of a family of materials based on alginate and acrylic polymers of potential interest as drug delivery systems.

  14. Artificial Metalloenzymes through Chemical Modification of Engineered Host Proteins

    KAUST Repository

    Zernickel, Anna

    2014-10-01

    With a few exceptions, all organisms are restricted to the 20 canonical amino acids for ribosomal protein biosynthesis. Addition of new amino acids to the genetic code can introduce novel functionalities to proteins, broadening the diversity of biochemical as well as chemical reactions and providing new tools to study protein structure, reactivity, dynamics and protein-protein-interactions. The site directed in vivo incorporation developed by P. G. SCHULTZ and coworkers, using an archeal orthogonal tRNA/aaRS (aminoacyl-tRNA synthase) pair, allows site-specifically insertion of a synthetic unnatural amino acid (UAA) by reprogramming the amber TAG stop codon. A variety of over 80 different UAAs can be introduced by this technique. However by now a very limited number can form kinetically stable bonds to late transition metals. This thesis aims to develop new catalytically active unnatural amino acids or strategies for a posttranslational modification of site-specific amino acids in order to achieve highly enantioselective metallorganic enzyme hybrids (MOEH). As a requirement a stable protein host has to be established, surviving the conditions for incorporation, posttranslational modification and the final catalytic reactions. mTFP* a fluorescent protein was genetically modified by excluding any exposed Cys, His and Met forming a variant mTFP*, which fulfills the required specifications. Posttranslational chemical modification of mTFP* allow the introduction of single site metal chelating moieties. For modification on exposed cysteines different maleiimid containing ligand structures were synthesized. In order to perform copper catalyzed click reactions, suitable unnatural amino acids (para-azido-(L)-phenylalanine, para-ethynyl-(L)-phenylalanine) were synthesized and a non-cytotoxic protocol was established. The triazole ring formed during this reaction may contribute as a moderate σ-donor/π-acceptor ligand to the metal binding site. Since the cell limits the

  15. Chemical modification of proteins by lipids in diabetes.

    Science.gov (United States)

    Baynes, John W

    2003-09-01

    Advanced glycation and lipoxidation end-products (AGE/ALE) increase in tissue proteins with age and at an accelerated rate in diabetes. This Review focuses on the nature and source of AGEs/ALEs and the factors affecting their formation in tissue and plasma proteins. Lipids are identified as an important source of chemical modification of proteins in diabetes, and the role of diabetes, dyslipidemia and renal disease in formation of AGEs/ALEs is reviewed. The article concludes with a discussion of ELISA assays for AGEs/ALEs and the merits of measuring AGEs/ALEs in the clinical laboratory.

  16. Surface Modification of Nitinol by Chemical and Electrochemical Etching

    Science.gov (United States)

    Yang, Zhendi; Wei, Xiaojin; Cao, Peng; Gao, Wei

    2013-07-01

    In this paper, Nitinol, an equiatomic binary alloy of nickel and titanium, was surface modified for its potential biomedical applications by chemical and electrochemical etching. The main objective of the surface modification is to reduce the nickel content on the surface of Nitinol and simultaneously to a rough surface microstructure. As a result, better biocompatibility and better cell attachment would be achieved. The effect of the etching parameters was investigated, using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometry (EDX) and X-ray photoelectron spectrometry (XPS). The corrosion property of modified Nitinol surfaces was investigated by electrochemical work station. After etching, the Ni content in the surface layer has been reduced and the oxidation of Ti has been enhanced.

  17. CHEMICAL MODIFICATION OF THE SURFACE OF CALCIUM ALGINATE GEL BEADS

    Institute of Scientific and Technical Information of China (English)

    Cong-ming Xiao; Li-chun Zhou

    2004-01-01

    The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerization two steps were explored. First, 5 grams CAGB with 2.5 mm initial diameter was initiated with 0.0493 mol/L K2S2O8 at 51 ℃ for 30 min in 15 mL 1% PVA/H2O. Then 4.34 mol/L VAc was added dropwise and the reaction was allowed to proce at 48 ℃ for 3 h. The grafting efficiency could come up to 30%. It was found the stability of modified CAGB in the air and in electrolyte solutions was greatly improved.

  18. Chemical Modification of Poly(epichlorohydrin) Using Montmorillonite Clay

    Institute of Scientific and Technical Information of China (English)

    BEKKAR Fatima; BELBACHIR Mohamed

    2009-01-01

    Cationic ring opening polymerization of epichlorohydrin (1) and acetic anhydride in the presence of Maghnite-H (Mag-H') as a catalyst afforded, ω-diacetylated poly(epichlorohydrin) (P1) in a moderate yield and molecular weight without formation of side products and degradation. P1 was chemically modified with morpholine (2),piperidine (3) and pyrrolidine (4) into the corresponding new functional poly(epichlorohydrin)s (P2-P4) in a moderate reaction conversion. The conversion of P1 into P2-P4 was confirmed by using FTIR and NMR spec-troscopy and the yield was calculated from the elemental analysis data according to the mole fraction concept. The obtained functional polymers were further characterized by thermal analysis which showed a substantial increase of the glass transition temperature (Tg). Thus, the chemical modification of a,ω-acetylated PECH using Mag-H+ of-fers a simple method for obtaining functional polymers. Mag-H+ is a montmorillonite sheet silicate clay exchanged with proton.

  19. Chemical modification of hybrid nanostructures (POSS for application as lubricant

    Directory of Open Access Journals (Sweden)

    Caroline Luvison

    2014-08-01

    Full Text Available Polyhedral oligomeric silsesquioxanes (POSS are hybrid structures type RSiO15n, with n organic groups R. These molecules can be easily functionalized by simply changing the chemical constitution of the organic groups. In this work, chemical modification of POSS-NH2 was performed by amidation reaction with butyric acid at elevated temperature, 160°C. The formation of the amide group is evinced by the appearance of NH angular deformation band at 1540 cm-1 in the FTIR spectra. Approximately 40% of the amino groups reacted, according to titration results. The formation of the amide groups resulted in a shift of the glass transition temperature (Tg from -36.9°C to -25.6°C for the modified-POSS sample. Both POSS-NH2 and modified-POSS samples exhibited similar thermal degradation pattern. Analysis of the pairs distribution function (PDF has determined that the hybrid nanoparticles are separated by a periodic distance of approximately 1.32 nm. POSS-NH2 and modified-POSS exhibit newtonian behavior, which will range from 10-1 s-1 and 1000 s-1. The viscosity decreased with increasing temperature, a typical behavior of liquid lubricants.

  20. Progressive chemical modification of clastic sediments with burial

    Science.gov (United States)

    Curtis, C. D.

    1987-03-01

    The porosity of clastic sediments at deposition varies very approximately between about 45% (sands) and 85% (muds). With burial, consolidation takes place as pore water is progressively eliminated. It would be misleading, however, to attribute alterations in sediment bulk properties to physical processes alone. Very significant mineralogical changes occur and these start soon after burial, especially in mudrocks. Striking heterogeneities such as thin, laterally continuous cemented horizons or discrete concretions are commonly introduced. These shallow burial processes are predominently the result of microbial activity. Thermodynamically unstable mixtures of organic matter and various oxidants [dissolved oxygen, sulphate, nitrate, particulate Fe(III) and Mn(IV)] provide both substrate and energy source for a variety of different microbial ecosystems. Mineralogical consequences include both leaching and the precipitation of carbonate, sulphide, phosphate and silica cements. The type and extent of mineral modification depends strongly on depositional environment variables such as rate of sedimentation and water composition. At greater depths, large scale modification of detrital clay minerals (particularly the smectite-I/S-illite transformation) takes place. Recent work of various kinds, however, has demonstrated that these changes may not be solid state transformations: clay mineral dissolution, transport and precipitation occur much more widely than was formerly supposed. In sandstones, authigenic precipitation of clay minerals from pore solution is much more obviouis. Systematic patterns of precipitation, alteration and replacement have been documented in many sedimentary basins. Porosity and permeability are reduced by cementation and, sometimes, enhanced by mineral dissolution. Whereas the general nature of these chemical reactions is fairly well understood, it is not yet possible to predict with certainty the scale or distribution of mineralogical consequences

  1. Surface modification on PMMA : PVDF polyblend: hardening under chemical environment

    Indian Academy of Sciences (India)

    R Bajpai; V Mishra; Pragyesh Agrawal; S C Datt

    2002-02-01

    The influence of chemical environment on polymers include the surface alteration as well as other deep modifications in surface layers. The surface hardening, as an effect of organic liquids on poly(methyl methacrylate): poly(vinylidene fluoride) (PMMA: PVDF), which is one of the few known miscible blends, has been detected using microhardness testing. Organic liquids like acetone, toluene, xylene and benzene were introduced on the surface of blend specimens for different durations. Vickers microhardness (v) was measured for treated and untreated specimens. The study reveals both hardening and plasticization of specimens at different exposure times. The degree of surface hardening is maximum under acetone treatment. All the specimens exhibit surface hardening at an exposure time of 1 h with all the four liquids. This feature is prominent with longer exposures for specimens with increasing content of PVDF. However, the degree of hardening decreases with the time of exposure in the respective environments. In general, acetone and toluene impart surface hardening, whereas, xylene and benzene soften the specimen. PMMA: PVDF (83 : 17) blend exhibits surface hardening under all the four treatments when compared with the respective untreated specimens.

  2. The Use of Chemical Modification of Polymer Waste for Obtaining Polymer Flocculants

    Institute of Scientific and Technical Information of China (English)

    W.W.Sulkowski; K.Nowak; A.Sulkowska; A.Wolin; ska; S.Malanka; W.M.Baldur; D.Pentak

    2007-01-01

    1 Results Chemical modification of polymer plastic wastes to useful products can be one of the way of effective waste plastics management (chemical recycling). Chemical modification of polymers and polymer plastic wastes can yield products with suitable physical and chemical properties. In consequence they can be used as polyelectrolytes[1]. The variety of pollutants, universality of various water and sewage treatment technologies, introduction of new water quality improved technologies have caused a gr...

  3. Antioxidant activity of Citrus limon essential oil in mouse hippocampus.

    Science.gov (United States)

    Campêlo, Lidianne Mayra Lopes; Gonçalves, Fabrício Custódio Moura; Feitosa, Chistiane Mendes; de Freitas, Rivelilson Mendes

    2011-07-01

    Citrus limon (L.) Burms (Rutaceae) has been shown in previous studies to have various biological functions (anti-inflammatory, antiallergic, antiviral, antimutagenic, and anticarcinogenic). However, traditional uses in folk medicine suggest that C. limon may have an effect on the central nervous system (CNS). This study investigated the effects of C. limon essential oil (EO) on lipid peroxidation level, nitrite content, glutathione reduced (GSH) concentration, and antioxidant enzymes [superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx)] activities in mice hippocampus. Swiss mice were treated with the suspension of 0.5% Tween 80, in distilled water used as vehicle (i.p., control group) and with EO in three different doses (0.05, 0.1, or 0.15 g/kg, i.p., EO 50, EO 100, and EO 150 groups, respectively). After the treatments, all groups were observed for 24 h. The enzyme activities as well as the lipid peroxidation, nitrite, and GSH concentrations in mice hippocampus were measured using spectrophotometric methods and the results were compared with values obtained from control group. EO of C. limon treatment significantly reduced the lipid peroxidation level and nitrite content but increased the GSH levels and the SOD, catalase, and GPx activities in mice hippocampus. Our findings strongly support the hypothesis that oxidative stress in hippocampus can occur during neurodegenerative diseases, proving that hippocampal damage induced by the oxidative process plays a crucial role in brain disorders, and also imply that a strong protective effect could be achieved using EO of C. limon as an antioxidant.

  4. Chemical synthesis and modification of target phases of chalcogenide nanomaterials

    Science.gov (United States)

    Sines, Ian T.

    Inorganic nanoparticles have been at the forefront of materials research in recent years due to their utility in modern technological processes. Chalcogenide nanomaterials are of particular interest because of their wide range of desirable properties for semiconductors, magnetic devices, and energy industries. Primary factors that dictate the properties of the material are the elemental composition, crystal structure, stoichiometry, crystallite size, and particle morphology. One of the most common approaches to synthesize these materials is through solution mediated routes. This approach offers unique advantages in controlling the morphology and particle size that other methods lack. This dissertation describes our recent work on exploiting solution chemical routes to control the crystal structure and composition of chalcogenide nanomaterials. We will start by discussing solution chemistry routes to synthesize non-equilibrium phases of chaclogenide nanomaterials. By using low-temperature bottom-up techniques it is possible to trap kinetically stable phases that cannot be accessed using traditional high-temperature techniques. We used solution chemistry to synthesize and characterize, for the first time, wurtzite-type MnSe. Wurtzite-type MnSe is the end-member of the highly investigated ZnxMn1-xSe solid solution, a classic magnetic semiconductor system. We will then discuss PbO-type FeS, another non-equilibrium phase that is isostructural with the superconducting phase of FeSe. We synthesized phase-pure PbO-type FeS using a low-temperature solvothermal route. We will then discuss the post-synthetic modification of chalcogenides nanomaterials. By exploiting the solubility of Se and S in tri-n-octylphosphine we can selectively extract the chalcogen from preformed chalcogenide nanomaterials. This gives chemists a technique for purification and phase-targeting of particular chalcogenide phases. This method can be modified to facilitate anion exchange. When Te is

  5. Chitosan derivatives obtained by chemical modifications for biomedical and environmental applications.

    Science.gov (United States)

    Alves, N M; Mano, J F

    2008-12-01

    Chitosan is a natural based polymer, obtained by alkaline deacetylation of chitin, which presents excellent biological properties such as biodegradability and immunological, antibacterial and wound-healing activity. Recently, there has been a growing interest in the chemical modification of chitosan in order to improve its solubility and widen its applications. The main chemical modifications of chitosan that have been proposed in the literature are reviewed in this paper. Moreover, these chemical modifications lead to a wide range of derivatives with a broad range of applications. Recent and relevant examples of the distinct applications, with particular emphasis on tissue engineering, drug delivery and environmental applications, are presented.

  6. Surface chemical and physical modification in stent technology for the treatment of coronary artery disease.

    Science.gov (United States)

    Nazneen, Feroze; Herzog, Grégoire; Arrigan, Damien W M; Caplice, Noel; Benvenuto, Pasquale; Galvin, Paul; Thompson, Michael

    2012-10-01

    Coronary artery disease (CAD) kills millions of people every year. It results from a narrowing of the arteries (stenosis) supplying blood to the heart. This review discusses the merits and limitations of balloon angioplasty and stent implantation, the most common treatment options for CAD, and the pathophysiology associated with these treatments. The focus of the review is heavily placed on research efforts geared toward the modification of stent surfaces for the improvement of stent-vascular compatibility and the reduction in the occurrence of related pathophysiologies. Such modifications may be chemical or physical, both of which are surveyed here. Chemical modifications may be passive or active, while physical modification of stent surfaces can also provide suitable substrates to manipulate the responses of vascular cells (endothelial, smooth muscle, and fibroblast). The influence of micro- and nanostructured surfaces on the in vitro cell response is discussed. Finally, future perspectives on the combination of chemical and physical modifications of stent surfaces are also presented.

  7. Chemical Posttranslational Modification with Designed Rhodium(II) Catalysts.

    Science.gov (United States)

    Martin, S C; Minus, M B; Ball, Z T

    2016-01-01

    Natural enzymes use molecular recognition to perform exquisitely selective transformations on nucleic acids, proteins, and natural products. Rhodium(II) catalysts mimic this selectivity, using molecular recognition to allow selective modification of proteins with a variety of functionalized diazo reagents. The rhodium catalysts and the diazo reactivity have been successfully applied to a variety of protein folds, the chemistry succeeds in complex environments such as cell lysate, and a simple protein blot method accurately assesses modification efficiency. The studies with rhodium catalysts provide a new tool to study and probe protein-binding events, as well as a new synthetic approach to protein conjugates for medical, biochemical, or materials applications.

  8. Chemical Modification of Papain and Subtilisin: An Active Site Comparison

    Science.gov (United States)

    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…

  9. Chitosan derivatives obtained by chemical modifications for biomedical and environmental applications

    OpenAIRE

    ALVES,N.M.; Mano, J. F.

    2008-01-01

    Chitosan is a natural based polymer, obtained by alkaline deacetylation of chitin, which presents excellent biological properties such as biodegradability and immunological, antibacterial and wound-healing activity. Recently, there has been a growing interest in the chemical modification of chitosan in order to improve its solubility and widen its applications. The main chemical modifications of chitosan that have been proposed in the literature are reviewed in this paper. Moreove...

  10. Chemical modification of the inner and outer surfaces of Tobacco Mosaic Virus (TMV).

    Science.gov (United States)

    Bruckman, Michael A; Steinmetz, Nicole F

    2014-01-01

    Viral nanoparticles derived from tobacco mosaic virus (TMV) find applications in various fields. We report the purification and chemical modification of TMV which is a hollow rod-shaped plant viral nanoparticle with modifiable interior and exterior surfaces. We describe methods to isolate TMV from its tobacco plant host for spatially controlled interior and exterior chemical modification and to characterize the resulting TMV hybrid materials.

  11. Reactive schedule modification in multipurpose batch chemical plants

    Energy Technology Data Exchange (ETDEWEB)

    Kanakamedala, K.B.; Reklaitis, G.V.; Venkatasubramanian, V. (Purdue Univ., West Lafayette, IN (United States). School of Chemical Engineering)

    1994-01-01

    A new scheme is described for reactive schedule modification in the face of unexpected deviations in processing times and unit availabilities of a multipurpose batch plant (MBP). Schedule modification is done using at least impact heuristic beam search which proceeds in two levels: creation of a decision tree which makes use of possible reroutings of the product that is causing a conflict, and heuristic pruning of the search space to contain the combinatorial complexity. The heuristic chooses a path among all possible reroutings for a product such that the impact of each decision on the rest of the schedule is kept as small as possible. This approach has been implemented and tested on a number of simulated deviations in a MBP case study with three products. The proposed least impact heuristic was found to perform better than the earliest finishing unit heuristic in all the cases considered.

  12. Incorporating chemical modification constraints into a dynamic programming algorithm for prediction of RNA secondary structure

    Science.gov (United States)

    Mathews, David H.; Disney, Matthew D.; Childs, Jessica L.; Schroeder, Susan J.; Zuker, Michael; Turner, Douglas H.

    2004-01-01

    A dynamic programming algorithm for prediction of RNA secondary structure has been revised to accommodate folding constraints determined by chemical modification and to include free energy increments for coaxial stacking of helices when they are either adjacent or separated by a single mismatch. Furthermore, free energy parameters are revised to account for recent experimental results for terminal mismatches and hairpin, bulge, internal, and multibranch loops. To demonstrate the applicability of this method, in vivo modification was performed on 5S rRNA in both Escherichia coli and Candida albicans with 1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide metho-p-toluene sulfonate, dimethyl sulfate, and kethoxal. The percentage of known base pairs in the predicted structure increased from 26.3% to 86.8% for the E. coli sequence by using modification constraints. For C. albicans, the accuracy remained 87.5% both with and without modification data. On average, for these sequences and a set of 14 sequences with known secondary structure and chemical modification data taken from the literature, accuracy improves from 67% to 76%. This enhancement primarily reflects improvement for three sequences that are predicted with <40% accuracy on the basis of energetics alone. For these sequences, inclusion of chemical modification constraints improves the average accuracy from 28% to 78%. For the 11 sequences with <6% pseudoknotted base pairs, structures predicted with constraints from chemical modification contain on average 84% of known canonical base pairs. PMID:15123812

  13. Effects of aluminium surface morphology and chemical modification on wettability

    DEFF Research Database (Denmark)

    Rahimi, Maral; Fojan, Peter; Gurevich, Leonid;

    2014-01-01

    Aluminium alloys are some of the predominant metals in industrial applications such as production of heat exchangers, heat pumps. They have high heat conductivity coupled with a low specific weight. In cold working conditions, there is a risk of frost formation on the surface of aluminium...... in the presence of water vapour, which can lead to the deterioration of equipment performance. This work addresses the methods of surface modification of aluminium and their effect of the underlying surface morphology and wettability, which are the important parameters for frost formation. Three groups of real...

  14. 77 FR 36170 - TSCA Inventory Update Reporting Modifications; Chemical Data Reporting; 2012 Submission Period...

    Science.gov (United States)

    2012-06-18

    ... rule. SUMMARY: EPA is amending the Toxic Substances Control Act (TSCA) Chemical Data Reporting (CDR... From the Federal Register Online via the Government Publishing Office EVIRONMENTAL PROTECTION AGENCY 40 CFR Part 711 RIN 2070-AJ43 TSCA Inventory Update Reporting Modifications; Chemical Data...

  15. Chemical reporter for visualizing metabolic cross-talk between carbohydrate metabolism and protein modification.

    Science.gov (United States)

    Zaro, Balyn W; Chuh, Kelly N; Pratt, Matthew R

    2014-09-19

    Metabolic chemical reporters have been largely used to study posttranslational modifications. Generally, it was assumed that these reporters entered one biosynthetic pathway, resulting in labeling of one type of modification. However, because they are metabolized by cells before their addition onto proteins, metabolic chemical reporters potentially provide a unique opportunity to read-out on both modifications of interest and cellular metabolism. We report here the development of a metabolic chemical reporter 1-deoxy-N-pentynyl glucosamine (1-deoxy-GlcNAlk). This small-molecule cannot be incorporated into glycans; however, treatment of mammalian cells results in labeling of a variety proteins and enables their visualization and identification. Competition of this labeling with sodium acetate and an acetyltransferase inhibitor suggests that 1-deoxy-GlcNAlk can enter the protein acetylation pathway. These results demonstrate that metabolic chemical reporters have the potential to isolate and potentially discover cross-talk between metabolic pathways in living cells.

  16. Polymeric Amines by chemical modifications of alternating aliphatic polyketones

    NARCIS (Netherlands)

    Zhang, Youchun; Broekhuis, A. A.; Stuart, Marc C. A.; Picchioni, F.

    2008-01-01

    Alternating, aliphatic polyketones were chemically modified by using di-amines to obtain polymeric products having pendant amino groups. The used reaction, Paal-Knorr, involves the formation of pyrrole rings along the polyketone backbone. The corresponding kinetics and final conversions are clearly

  17. Chemical modifications and applications of alternating aliphatic polyketones

    NARCIS (Netherlands)

    Zhang, Youchun

    2008-01-01

    Alternating aliphatic polyketones, produced by co- and terpolymerization of carbon monoxide and olefins (mixtures of ethylene and propylene) using palladium-based homogeneous catalysis represent a very promising class of polymers for a wide range of applications. Besides many interesting chemical

  18. Synthesis, chemical modification, and surface assembly of carbon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Amma, A.; St. Angelo, S.K.; Mallouk, T.E. [Department of Chemistry, The Pennsylvania State University, University Park, PA 16802 (United States); Razavi, B.; Mayer, T.S. [Electrical Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2003-05-01

    Carbon nanotubules and nanowires were synthesized by pyrolysis of polymer precursors in the pores of alumina membranes. The nanowires were released by dissolving the membranes, and were then made hydrophobic or hydrophilic by chemical surface derivatization. These nanowires could be placed into lithographically defined wells on surfaces by means of electrostatic interactions with monolayers at the bottoms of the wells. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  19. Petroleum system of the Cano Limon field, Llanos Basin, Colombia

    Energy Technology Data Exchange (ETDEWEB)

    Molina, J. [Occidental de Colombia, Inc., Bogota (Colombia)

    1996-08-01

    The Chipaque-Lower Carbonera({circ}) Petroleum System of the northernmost Llanos Basin of Colombia, covers 11,100 km{sup 2} and includes two major oil fields: Caho Limon in Colombia, and Guafita in Venezuela, jointly with three more relatively small fields in Colombia: Redondo, Cano Rondon, and Jiba. Ultimate recoverable reserves are in the order of 1.4 BBO. The sedimentary section penetrated in the Northern Llanos has been informally subdivided into four Cretaceous formations: K3, K2B, K2A, and Lower K1 deposited during the Albian-Senonian, and into four Tertiary formations: Lower Carbonera, Upper Carbonera, Leon, and Guayabo deposited during the Late Eocene to Pliocene time. The main reservoir is the Lower Carbonera Formation, which contains 81% of the total reserves. The Cretaceous K2A and Lower K1 reservoirs contain 6% and 8%, respectively of the reserves. Minor reserves are accumulated in the discontinuous sandstones of the Oligocene Upper Carbonera Formation Geochemical analyses of the Cano Limon/Guafita oils indicate that these are aromatic intermediate to paraffinic-naphthenic, non degradated, genetically related to a common marine-derived type of kerogen. These oils were generated by a mature, marine clastic source rock with a small contribution of continental organic matter. The geochemistry of the hydrocarbon suggest a genetic relationship with the shales of the Chipaque formation, basin-ward equivalent of the K2 Formation, which presents kerogen type II organic matter and has been recognized as a good source rock. The petroleum system is hypothetical because a definite oil-source rock correlation is lacking. The development of the petroleum system is directly related to the history of movement of the Santa Maria, La Yuca, Caho Limon, and Matanegra wrench faults. It has been determined that these faults of pre-Cretaceous rifting origin, created the Santa Maria Graben of which the Espino Graben is the continuation in Venezuela.

  20. Chemical Modification Effect on the Mechanical Properties of Coir Fiber

    Directory of Open Access Journals (Sweden)

    Samia Sultana Mir

    2012-04-01

    Full Text Available Natural fiber has a vital role as a reinforcing agent due to its renewable, low cost, biodegradable, less abrasive and eco-friendly nature. Whereas synthetic fibers like glass, boron, carbon, metallic, ceramic and inorganic fibers are expensive and not eco-friendly. Coir is one of the natural fibers easily available in Bangladesh and cheap. It is derived from the husk of the coconut (Cocos nucifera. Coir has one of the highest concentrations of lignin, which makes it stronger. In recent years, wide range of research has been carried out on fiber reinforced polymer composites [4-13].The aim of the present research is to characterize brown single coir fiber for manufacturing polymer composites reinforced with characterized fibers. Adhesion between the fiber and polymer is one of factors affecting the strength of manufactured composites. In order to increase the adhesion, the coir fiber was chemically treated separately in single stage (with Cr2(SO43•12(H2O and double stages (with CrSO4 and NaHCO3. Both the raw and treated fibers were characterized by tensile testing, Fourier transform infrared (FTIR spectroscopic analysis, scanning electron microscopic analysis. The result showed that the Young’s modulus increased, while tensile strength and strain to failure decreased with increase in span length. Tensile properties of chemically treated coir fiber was found higher than raw coir fiber, while the double stage treated coir fiber had better mechanical properties compared to the single stage treated coir fiber. Scanning electron micrographs showed rougher surface in case of the raw coir fiber. The surface was found clean and smooth in case of the treated coir fiber. Thus the performance of coir fiber composites in industrial application can be improved by chemical treatment.

  1. Antimicrobial synergism and cytotoxic properties of Citrus limon L., Piper nigrum L. and Melaleuca alternifolia (Maiden and Betche) Cheel essential oils.

    Science.gov (United States)

    Nikolić, Miloš M; Jovanović, Katarina K; Marković, Tatjana Lj; Marković, Dejan Lj; Gligorijević, Nevenka N; Radulović, Siniša S; Kostić, Marina; Glamočlija, Jasmina M; Soković, Marina D

    2017-08-17

    The chemical composition, antimicrobial and synergistic effect, and cytotoxic activity of Citrus limon (lemon), Piper nigrum (green pepper) and Melaleuca alternifoila (tea tree) essential oils (EOs) were investigated. Chemical analyses of essential oils were tested by GC-FID and GC-MS spectroscopy. The antimicrobial activity assay was conducted using microdilution method against several oral bacteria and Candida spp. originating from the humans with oral disorders. The synergistic antimicrobial activity was evaluated using checkerboard method. The cytotoxicity evaluation of EOs was assessed using MTT test. Limonene (37.5%) and β-pinene (17.9%) were the major compounds in C. limon oil, β-pinene (34.4%), δ-3-carene (19.7%), limonene (18.7%) and α-pinene (10.4%) in P. nigrum oil and terpinen-4-ol (38.6%) and γ-terpinene (21.7%) in M. alternifolia oil. The broad-spectrum antimicrobial activity was achieved by tested three EOs, with C. limon oil being the strongest against bacteria and M. alternifolia oil strongest against fungi. The EOs demonstrated synergism; their combined application revealed an increase in antimicrobial activity. All tested essential oils showed lower cytotoxic activity in comparison with the positive control, and the obtained results confirmed a dose-dependent activity. The results of this study encourage use of tested EOs in development of a novel agent intended for prevention or therapy of corresponding oral disorders. © 2017 Royal Pharmaceutical Society.

  2. Selective edge modification in graphene and graphite by chemical oxidation.

    Science.gov (United States)

    Yang, Min; Moriyama, Satoshi; Higuchi, Masayoshi

    2014-04-01

    The effect of edge structures in graphene sheets has been well investigated theoretically but most experimental demonstrations of the functionalization have been for the bulk structures because of only a few reports on chemical methods to modify the edges selectively. We herein report a chemical method using the Lemieux-von Rudloff reagent that selectively oxidizes only the edges of graphene sheets. The selective oxidation at the edges of the graphene sheet was confirmed by thermogravimetric analysis (TGA), Raman mapping measurements, and X-ray photoelectron spectroscopy (XPS). The TGA result of the oxidized graphite with different particle sizes showed a slight weight loss at approximately 350 degrees C (2.29% for the middle particles (35 microm)), which indicates thermal decomposition of the oxidized edge part. The Raman mapping measurement in the inner part of graphene sheets didn't detect any defects or translational symmetry breaking after the oxidation. The XPS data clearly showed that the total carbon atom content present as C--O, C==O, and O--C==C increased from 4.65 to 6.18% by the oxidation. Using the obtained edge-oxidized graphene as a starting material, various functionalizations of the edge structure are expected in the future.

  3. Laser and chemical surface modifications of titanium grade 2 for medical application

    Energy Technology Data Exchange (ETDEWEB)

    Kwaśniak, P. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Pura, J., E-mail: jaroslawpura@gmail.com [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Zwolińska, M.; Wieciński, P. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Skarżyński, H.; Olszewski, L. [Institute of Physiology and Pathology of Hearing, Warsaw (Poland); World Hearing Center, Kajetany (Poland); Marczak, J. [Military University of Technology, Institute of Optoelectronics, Warsaw (Poland); Garbacz, H.; Kurzydłowski, K.J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland)

    2015-05-01

    Highlights: • DLIL technique and etching were used for functionalization of Ti grade 2 surface. • Modification was performed on semi-finished flat and curved Ti surfaces. • Modification results in periodic multimodal (micro and nano-size) Ti topography. - Abstract: The article presents combined, chemical and physical approach to titanium surface functionalization designed for biomedical applications. The topography modification has been obtained by employing the double laser beam interference technique and chemical etching. In the outcome, clean and smooth Ti surface as well as periodic striated topography with the roughness range from nano- to micrometers were created. The obtained structures were characterized in terms of shape, roughness, chemical composition, mechanical properties and microstructures. In order to achieve all information, numerous of research methods have been used: scanning electron microscopy, atomic force microscopy, optical profilometry and microhardness measurements. Demonstrated methodology can be used as an effective tool for manufacturing controlled surface structures improving the bone–implants interactions.

  4. Chemical Modification of Boron-Doped Diamond Electrodes for Applications to Biosensors and Biosensing.

    Science.gov (United States)

    Svítková, Jana; Ignat, Teodora; Švorc, Ľubomír; Labuda, Ján; Barek, Jiří

    2016-05-03

    Boron-doped diamond (BDD) is a prospective electrode material that possesses many exceptional properties including wide potential window, low noise, low and stable background current, chemical and mechanical stability, good biocompatibility, and last but not least exceptional resistance to passivation. These characteristics extend its usability in various areas of electrochemistry as evidenced by increasing number of published articles over the past two decades. The idea of chemically modifying BDD electrodes with molecular species attached to the surface for the purpose of creating a rational design has found promising applications in the past few years. BDD electrodes have appeared to be excellent substrate materials for various chemical modifications and subsequent application to biosensors and biosensing. Hence, this article presents modification strategies that have extended applications of BDD electrodes in electroanalytical chemistry. Different methods and steps of surface modification of this electrode material for biosensing and construction of biosensors are discussed.

  5. Modification of Textile Materials' Surface Properties Using Chemical Softener

    Directory of Open Access Journals (Sweden)

    Jurgita KOŽENIAUSKIENĖ

    2011-03-01

    Full Text Available In the present study the effect of technological treatment involving the processes of washing or washing and softening with chemical cationic softener "Surcase" produced in Great Britain on the surface properties of cellulosic textile materials manufactured from cotton, bamboo and viscose spun yarns was investigated. The changes in textile materials surface properties were evaluated using KTU-Griff-Tester device and FEI Quanta 200 FEG scanning electron microscope (SEM. It was observed that the worst hand properties and the higher surface roughness are observed of cotton materials if compared with those of bamboo and viscose materials. Also, it was shown that depending on the material structure the handle parameters of knitted materials are the better than the ones of woven fabrics.http://dx.doi.org/10.5755/j01.ms.17.1.249

  6. Chemical Modification on Reactive Dye Adsorption Capacity of Castor Seeds

    Directory of Open Access Journals (Sweden)

    V. Dharmalingam

    2011-01-01

    Full Text Available Abstract: The roles played by four major functional groups (amine, carboxyl, azo, hydroxyl groups in the biomass of castor seeds in adsorption of seven dyes were investigated. These functional groups in castor seeds were chemically modified individually to determine their contribution to the adsorption of ionic dyes. The dyes used were remazol red B, procino yellow, fast green FCF, brilliant cresyl blue, methylene blue, neutral red, red-141. It was found that hydroxyl group inhibited the adsorption of anionic dyes but it was major functional group in the adsorption of cationic dyes, hydroxyl group was important functional group in the adsorption of all seven dyes and the effect of methylation of amino group was not significant on the adsorption of seven dyes.

  7. Chemical modification and functionalisation of poly(ethylene terephthalate) fiber

    Energy Technology Data Exchange (ETDEWEB)

    Kim, I.H.; Kim, S.H. [Sungkyunkwan University, Suwon (Korea)

    2002-05-01

    Poly(ethylene terephthalate ) (PET) fibers were modified by deep UV irradiation which was produced by a low pressure mercury lamp. FT-IR and XPS analyses were used to elucidate the surface chemical composition of PET fibers treated with UV. Relative O{sub 1s} intensity increased considerably and it was found that oxygen was incorporated in the form of COO on the fiber surface. FT-IR and XPS analyses proved the existence of carboxylic groups on the surfaces and the adsorption test of cationic compound further supported these results. The concentration of carboxylic acid group on the surface increased remarkably with increasing irradiation time. XPS analysis and adsorption experiments proved that the surface structure of the UV{sub i}rradiated PET fibers were stable for 12 months. Antibacterial property and the deodorization rate of UV-irradiated PET fibers adsorbed with the berberine compound were investigated. reduction rates of bacteria increased by about 21 to 99% compared to unradiated PET fiber. Deodorization rates of 23% for unradiated PET fiber increased to about 75% for 30 min irradiated samples. (author). 33 refs., 3 tabs., 11 figs.

  8. Surface Modification through Chemically Adsorbed Monolayer of Thiophene Molecules

    Science.gov (United States)

    Yamamoto, Shin-ichi; Ogawa, Kazufumi

    2008-07-01

    Using a time-averaged dielectrophoretic force from an applied electric field, we have observed the assembly of a chemically adsorbed monomolecular layer (CAM) on microwires and connections and the formation of an electric path between a lithographically patterned array of two platinum (Pt) electrodes. A Pt electrode/monolayer/Pt electrode junction was fabricated by the self-assembly of a rigid monomolecular layer, namely 3-{6-[11-(trichlorosilyl)undecanoyl]hexyl} thiophene (TEN) with thiophene groups in the lateral direction between the Pt electrodes. Conductive probe AFM (CP-AFM) was used to investigate the forward bias conduction properties of a TEN film grown by a wet deposition process on a glass substrate. The self-assembly depends on the ideal rigidity of the CAM and the strong affinity of the thiophene end groups of the CAM for the Pt electrode. The current-voltage (I-V) characteristics of the conjugated thiophene junction exhibited stepwise features at room temperature. The I-V characteristics can be explained by electron transport through the junction. From the results of experiments carried out under ambient conditions, the conductivity of the laterally conjugated polythiophene groups was calculated to be 5.0 ×104 S/cm. Understanding and using these effects will allow the controlled fabrication and positioning of microwires or connections at densities much greater than those now achievable.

  9. Chemical surface modification of porous silicon with palladium and characterizations

    Energy Technology Data Exchange (ETDEWEB)

    Kanungo, J.; Maji, S.; Saha, H. [IC Design and Fabrication Centre, Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata 700032 (India); Basu, S., E-mail: sukumar_basu@yahoo.co.u [IC Design and Fabrication Centre, Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata 700032 (India)

    2010-03-15

    Porous silicon (PS) was formed on p-type crystalline silicon of (1 0 0) orientation and 2-5 OMEGA cm resistivity by the electrochemical anodization method using HF and ethanol as the electrolyte. Adjusting the current density and the HF concentration in the electrolyte the porosity of the samples were varied from 40% to 60%. The porous silicon surface was modified with PdCl{sub 2} solution by a low cost chemical method. Both the unmodified and the modified PS were thoroughly characterized by the EDAX analysis, the digital X-ray image mapping and the XPS study. Electrical characteristics were performed by the I-V measurements for both the lateral and the sandwich structures using Al metal contact. The I-V characteristics of the modified PS for all the porosity were more reproducible compared to the unmodified PS surfaces. It was further observed that the conductivity increased with the increasing porosity for the Pd-modified surfaces whereas it decreased for the unmodified PS.

  10. Chemical Modification of the Multi-Target Neuroprotective Compound Fisetin

    Science.gov (United States)

    Chiruta, Chandramouli; Schubert, David; Dargusch, Richard; Maher, Pamela

    2012-01-01

    Many factors are implicated in age-related CNS disorders making it unlikely that modulating only a single factor will provide effective treatment. Perhaps a better approach is to identify small molecules that have multiple biological activities relevant to the maintenance of brain function. Recently, we identified an orally active, neuroprotective and cognition-enhancing molecule, the flavonoid fisetin, that is effective in several animal models of CNS disorders. Fisetin has direct antioxidant activity and can also increase the intracellular levels of glutathione (GSH), the major endogenous antioxidant. In addition, fisetin has both neurotrophic and anti-inflammatory activity. However, its relatively high EC50 in cell based assays, low lipophilicity, high tPSA and poor bioavailability suggest that there is room for medicinal chemical improvement. Here we describe a multi-tiered approach to screening that has allowed us to identify fisetin derivatives with significantly enhanced activity in an in vitro neuroprotection model while at the same time maintaining other key activities. PMID:22192055

  11. Chemically Patterned Inverse Opal Created by a Selective Photolysis Modification Process.

    Science.gov (United States)

    Tian, Tian; Gao, Ning; Gu, Chen; Li, Jian; Wang, Hui; Lan, Yue; Yin, Xianpeng; Li, Guangtao

    2015-09-01

    Anisotropic photonic crystal materials have long been pursued for their broad applications. A novel method for creating chemically patterned inverse opals is proposed here. The patterning technique is based on selective photolysis of a photolabile polymer together with postmodification on released amine groups. The patterning method allows regioselective modification within an inverse opal structure, taking advantage of selective chemical reaction. Moreover, combined with the unique signal self-reporting feature of the photonic crystal, the fabricated structure is capable of various applications, including gradient photonic bandgap and dynamic chemical patterns. The proposed method provides the ability to extend the structural and chemical complexity of the photonic crystal, as well as its potential applications.

  12. Memory boosting effect of Citrus limon, Pomegranate and their combinations.

    Science.gov (United States)

    Riaz, Azra; Khan, Rafeeq Alam; Algahtani, Hussein A

    2014-11-01

    Memory is greatly influenced by factors like food, stress and quality of sleep, hence present study was designed to evaluate the effect of Citrus limon and Pomegranate juices on memory of mice using Harvard Panlab Passive Avoidance response apparatus controlled through LE2708 Programmer. Passive avoidance is fear-motivated tests used to assess short or long-term memory of small animals, which measures latency to enter into the black compartment. Animals at MCLD showed highly significant and significant increase in latency to enter into the black compartment after 3 and 24 hours respectively than control, animals at HCLD showed significant increase in latency only after 3hours. Animals both at low and moderate doses of pomegranate showed significant increase in test latency after 3 hours, while animals at high dose showed highly significant and significant increase in latency after 3 and 24 hours respectively. There was highly significant and significant increase in latency in animals at CPJ-1 combination after 3 and 24 hours respectively; however animals received CPJ-2 combination showed significant increase in latency only after 3 hours as compare to control. These results suggest that Citrus limon and Pomegranate has phytochemicals and essential nutrients which boost memory, particularly short term memory. Hence it may be concluded that flavonoids in these juices may be responsible for memory enhancing effects and a synergistic effect is observed by CPJ-1 and CPJ-2 combinations.

  13. A Study on Physical Dispersion and Chemical Modification of Graphene

    Energy Technology Data Exchange (ETDEWEB)

    Yim, Eun-Chae; Kim, Seong-Jun [Chonnam National University, Gwangju (Korea, Republic of)

    2015-12-15

    Graphene has a wide spectrum on its application field due to various and excellent physical properties. However, it is very difficult to apply that graphene exists as lump or fold condition in general organic solvents. Besides, graphene was difficult to maintain as uniform condition due to chemical inert and distributions with various size and shapes. Therefore, this study was focused to study dispersion and modifying methods of aggregated graphene. The dispersion methods contain as follow: i) physical milling using glass bead, ii) co-treatment of glass bead and ultrasonic waves, iii) dispersion in organic solvents, iv) modifying with dry-ice. Milling using glass bead with size 2.5 mm was effective to be size decrease of 36.4% in comparison with control group. Mixed treatment of glass bead (size 2.5 mm) and ultrasonic waves (225W, 10 min) showed relative size decrease of 76%, suggesting that the size decrease depends on the size of glass bead, intensity of ultrasonic waves and treatment time. Solvents of Ethyl acetate (EA) and Isoprophyl alcohol (IPA) were used in order to improve dispersion by modifying surface of graphene. IPA of them showed a favorable dispersion with more -CO functional groups in the FT-IR analysis. On the other hand, the oxygen content of graphene surface modified by dry-ice was highly increased from 0.8 to 4.9%. From the results, it was decided that the favorable dispersion state for a long time was obtained under the condition of -CO functional group increase in IPA solvent.

  14. Chemical Modification of the Inner and Outer Surfaces of Tobacco Mosaic Virus (TMV)

    OpenAIRE

    Bruckman, Michael A.; Steinmetz, Nicole F.

    2014-01-01

    Viral nanoparticles derive from tobacco mosaic virus (TMV) has broad applications in various fields. We report the purification and chemical engineering of TMV which is a hollow rod-shaped plant viral nanoparticle with modifiable interior and exterior surfaces. Here, we describe methods to isolate TMV from its tobacco plant host for spatially controlled interior and exterior chemical modification and to characterize the resulting TMV hybrid materials.

  15. Surface modification of silicon-containing fluorocarbon films prepared by plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Jin, Yoonyoung; Desta, Yohannes; Goettert, Jost; Lee, G. S.; Ajmera, P. K.

    2005-07-01

    Surface modification of silicon-containing fluorocarbon (SiCF) films achieved by wet chemical treatments and through x-ray irradiation is examined. The SiCF films were prepared by plasma-enhanced chemical vapor deposition, using gas precursors of tetrafluoromethane and disilane. As-deposited SiCF film composition was analyzed by x-ray photoelectron spectroscopy. Surface modification of SiCF films utilizing n-lithiodiaminoethane wet chemical treatment is discussed. Sessile water-drop contact angle changed from 95°+/-2° before treatment to 32°+/-2° after treatment, indicating a change in the film surface characteristics from hydrophobic to hydrophilic. For x-ray irradiation on the SiCF film with a dose of 27.4 kJ/cm3, the contact angle of the sessile water drop changed from 95°+/-2° before radiation to 39°+/-3° after x-ray exposure. The effect of x-ray exposure on chemical bond structure of SiCF films is studied using Fourier transform infrared measurements. Electroless Cu deposition was performed to test the applicability of the surface modified films. The x-ray irradiation method offers a unique advantage in making possible surface modification in a localized area of high-aspect-ratio microstructures. Fabrication of a Ti-membrane x-ray mask is introduced here for selective surface modification using x-ray irradiation.

  16. Active-site residues of procarboxypeptidase Y are accessible to chemical modification

    DEFF Research Database (Denmark)

    Sørensen, S O; Winther, Jakob R.

    1994-01-01

    The accessibility of the active-site cleft of procarboxypeptidase Y from Saccharomyces cerevisiae has been studied by chemical modifications of two specific amino-acid residues. Previous studies have shown that these residues, Cys-341 and Met-398 in the mature enzyme, are located in the S1 and S'1...

  17. Protective effects of essential oil of Citrus limon against aspirin-induced toxicity in IEC-6 cells.

    Science.gov (United States)

    Bouzenna, Hafsia; Hfaiedh, Najla; Giroux-Metges, Marie-Agnès; Elfeki, Abdelfattah; Talarmin, Hélène

    2017-05-01

    Aspirin, one of the widely used nonsteroidal anti-inflammatory drugs, is the most highly consumed pharmaceutical product in the world. However, it has several side effects in cells. This study was designed to investigate the antioxidative activity and cytoprotective effects of essential oil of Citrus limon (EOC) extracted from leaves against aspirin-induced damages in the rat small intestine epithelial cells (IEC-6). Biochemical indicators were used to assess cytotoxicity and oxidative damages caused by aspirin treatment on IEC-6. Our results showed that the chemical characterization of EOC identified 25 compounds representing 98.19% of the total oil. The major compounds from this oil were z-citral (53.21%), neryl acetate (13.06%), geranyl acetate (10.33%), and limonene (4.23%). Aspirin induced a decrease in cell viability as well as an increase in superoxide dismutase (SOD) and catalase (CAT) activities. Contrariwise, the co-exposure of cells to aspirin and EOC alleviated every above syndrome by an increase in cell survival and decrease in SOD and CAT activities. In conclusion, the essential oil of C. limon has a potent cytoprotective effect against aspirin-induced toxicity in IEC-6 cells.

  18. Chemical modification of amino acid residues in glycerinated Vorticella stalk and Ca(2+)-induced contractility.

    Science.gov (United States)

    Kono, R; Ochiai, T; Asai, H

    1997-01-01

    The glycerinated stalk of the peritrich ciliate Vorticella, was treated with various reagents to chemically modify the amino acid residues. The influences of these modifcations on spasmoneme contractility were investigated. First, it was confirmed that the spasmoneme contraction is not inhibited by alteration of SH groups. It was also demonstrated that chemical modification of methionine and tryptophan residues abolishes spasmoneme contractility. The reagents used for chemical modification were N-bromosuccinimide (NBS), chloramine T, and 2-hydroxy-5-nitrobenzyl bromide (HNBB), which abolished spasmoneme contractility at concentrations of 40-50 microM, 200-300 microM, and 4 mM, respectively. These results suggest that, along with Ca2+ binding proteins, there are other as yet to be identified proteins involved in contractility.

  19. Modification of optical and electrical properties of chemical bath deposited CdS using plasma treatments

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, G. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Krishnan, B. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Avellaneda, D.; Castillo, G. Alan; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Shaji, S., E-mail: sshajis@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

    2011-08-31

    Cadmium sulphide (CdS) is a well known n-type semiconductor that is widely used in solar cells. Here we report preparation and characterization of chemical bath deposited CdS thin films and modification of their optical and electrical properties using plasma treatments. CdS thin films were prepared from a chemical bath containing Cadmium chloride, Triethanolamine and Thiourea under various deposition conditions. Good quality thin films were obtained during deposition times of 5, 10 and 15 min. CdS thin films prepared for 10 min. were treated using a glow discharge plasma having nitrogen and argon carrier gases. The changes in morphology, optical and electrical properties of these plasma treated CdS thin films were analyzed in detail. The results obtained show that plasma treatment is an effective technique in modification of the optical and electrical properties of chemical bath deposited CdS thin films.

  20. Chemical modification of the third strand: differential effects on purine and pyrimidine triple helix formation.

    Science.gov (United States)

    Mills, Martin; Arimondo, Paola B; Lacroix, Laurent; Garestier, Thérèse; Klump, Horst; Mergny, Jean-Louis

    2002-01-08

    DNA triple helices offer exciting perspectives toward oligonucleotide-directed control of gene expression. Oligonucleotide analogues are routinely used with modifications in either the backbone or the bases to form more stable triple-helical structures or to prevent their degradation in cells. In this article, different chemical modifications are tested in a model system, which sets up a competition between the purine and pyrimidine motifs. For most modifications, the DeltaH degrees of purine triplex formation is close to zero, implying a nearly temperature-independent affinity constant. In contrast, the pyrimidine triplex is strongly favored at lower temperatures. The stabilization induced by modifications previously known to be favorable to the pyrimidine motif was quantified. Interestingly, modifications favorable to the GT motif (propynyl-U and dU replacing T) were also discovered. In a system where two third strands compete for triplex formation, replacement of the GA or GT strand by a pyrimidine strand may be observed at neutral pH upon lowering the temperature. This purine-to-pyrimidine triplex conversion depends on the chemical nature of the triplex-forming strands and the stability of the corresponding triplexes.

  1. Silent Encoding of Chemical Post-Translational Modifications in Phage-Displayed Libraries.

    Science.gov (United States)

    Tjhung, Katrina F; Kitov, Pavel I; Ng, Simon; Kitova, Elena N; Deng, Lu; Klassen, John S; Derda, Ratmir

    2016-01-13

    In vitro selection of chemically modified peptide libraries presented on phage, while a powerful technology, is limited to one chemical post-translational modification (cPTM) per library. We use unique combinations of redundant codons to encode cPTMs with "silent barcodes" to trace multiple modifications within a mixed modified library. As a proof of concept, we produced phage-displayed peptide libraries Ser-[X]4-Gly-Gly-Gly, with Gly and Ser encoded using unique combinations of codons (TCA-[X]4-GGAGGAGGA, AGT-[X]4-GGTGGTGGT, etc., where [X]4 denotes a random NNK library). After separate chemical modification and pooling, mixed-modified libraries can be panned and deep-sequenced to identify the enriched peptide sequence and the accompanying cPTM simultaneously. We panned libraries bearing combinations of modifications (sulfonamide, biotin, mannose) against matched targets (carbonic anhydrase, streptavidin, concanavalin A) to identify desired ligands. Synthesis and validation of sequences identified by deep sequencing revealed that specific cPTMs are significantly enriched in panning against the specific targets. Panning on carbonic anhydrase yielded a potent ligand, sulfonamide-WIVP, with Kd = 6.7 ± 2.1 nM, a 20-fold improvement compared with the control ligand sulfonamide-GGGG. Silent encoding of multiple cPTMs can be readily incorporated into other in vitro display technologies such as bacteriophage T7 or mRNA display.

  2. Controlled modification of the structure of polymer surfaces by chemically grafting inorganic species

    Directory of Open Access Journals (Sweden)

    Rodrigo Lambert Oréfice

    1999-07-01

    Full Text Available Many chemical and physical methods, such as plasma, e-beam, sputtering, CVD and others, have been used to modify the structure of polymer surfaces by depositing thin inorganic films. Most of these techniques are based upon the use of high energy sources that ultimately can damage either chemically or physically polymer surfaces. Moreover, these methods are usually not versatile enough to allow the design of structurally and chemically tailored surfaces through the control of the distribution of chemical functionalities throughout the surface. In this work, inorganic species were introduced onto polymer substrates in a controlled manner by performing a sequence of chemical reactions at the surface. Sulfonation followed by silanization reactions were used to graft alkoxysilane species at the surface of poly(aryl sulfones. The heterogeneous chemical modification of poly(aryl sulfones was monitored by FTIR-ATR (Attenuated Total Reflection - FTIR. Model compounds were used to study the chemical reactions occurring during the grafting procedure. The results showed that the developed procedure can allow a controlled introduction of inorganic species onto polymer surfaces. Furthermore, in order to prove that this procedure enables the deposition of specific chemical functionalities onto polymer surfaces that can be used to create chemically and structurally tailored surfaces, silicate films were deposited on previously silanated PAS bioactive glass composites. In vitro tests showed that the surface modified composite can enhance the rates of hydroxy-carbonate-apatite precipitation.

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

    Science.gov (United States)

    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.

  4. Chemical modification of amino acids by atmospheric-pressure cold plasma in aqueous solution

    Science.gov (United States)

    Takai, Eisuke; Kitamura, Tsuyoshi; Kuwabara, Junpei; Ikawa, Satoshi; Yoshizawa, Shunsuke; Shiraki, Kentaro; Kawasaki, Hideya; Arakawa, Ryuichi; Kitano, Katsuhisa

    2014-07-01

    Plasma medicine is an attractive new research area, but the principles of plasma modification of biomolecules in aqueous solution remain elusive. In this study, we investigated the chemical effects of atmospheric-pressure cold plasma on 20 naturally occurring amino acids in aqueous solution. High-resolution mass spectrometry revealed that chemical modifications of 14 amino acids were observed after plasma treatment: (i) hydroxylation and nitration of aromatic rings in tyrosine, phenylalanine and tryptophan; (ii) sulfonation and disulfide linkage formation of thiol groups in cysteine; (iii) sulfoxidation of methionine and (iv) amidation and ring-opening of five-membered rings in histidine and proline. A competitive reaction experiment using 20 amino acids demonstrated that sulfur-containing and aromatic amino acids were preferentially decreased by the plasma treatment. These data provide fundamental information for elucidating the mechanism of protein inactivation for biomedical plasma applications.

  5. Dissection of the DNA mimicry of the bacteriophage T7 Ocr protein using chemical modification

    OpenAIRE

    Stephanou, Augoustinos S.; Roberts, Gareth A; Cooper, Laurie P.; Clarke, David J.; Thomson, Andrew R; MacKay, C. Logan; Nutley, Margaret; Cooper, Alan; Dryden, David T.F

    2009-01-01

    The homodimeric Ocr (overcome classical restriction) protein of bacteriophage T7 is a molecular mimic of double-stranded DNA and a highly effective competitive inhibitor of the bacterial type I restriction/modification system. The surface of Ocr is replete with acidic residues that mimic the phosphate backbone of DNA. In addition, Ocr also mimics the overall dimensions of a bent 24-bp DNA molecule. In this study, we attempted to delineate these two mechanisms of DNA mimicry by chemically modi...

  6. Thermally reversible thermoset materials based on the chemical modification of alternating aliphatic polyketones

    OpenAIRE

    Araya Hermosilla, Rodrigo Andrés

    2016-01-01

    This thesis focused on the synthesis and characterization of different kinds of reversible thermosets and thermoset nanocomposite materials by using alternating aliphatic polyketone (PK) as raw material. Fundamental knowledge was generated regarding the molecular design of new polymers via chemical modification of PK with aliphatic and aromatic amine compounds. The resulting thermally reversible thermoset systems were investigated to outline the benefits for the synergistic cooperation betwee...

  7. Chemical Modifications of Antisense Morpholino Oligomers Enhance Their Efficacy against Ebola Virus Infection

    Science.gov (United States)

    2009-05-01

    specific PMOs in infected cells and mice during lethal Ebola virus challenge. Members of the Filoviridae family of viruses , Ebola virus (EBOV) and Marburg ...American Society for Microbiology. All Rights Reserved. Chemical Modifications of Antisense Morpholino Oligomers Enhance Their Efficacy against Ebola Virus ...sequence is complementary to a region spanning the start codon of VP24 mRNA were protected against lethal Ebola virus challenge. In the present study, we

  8. EFFECT OF CHEMICAL MODIFICATION TYPE ON PHYSICOCHEMICAL AND RHEOLOGICAL CHARACTERISTICS OF BANANA STARCH

    OpenAIRE

    D. Guerra-DellaValle; M. M. Sánchez-Rivera; P.B. Zamudio-Flores; G. Méndez-Montealvo; L.A. Bello-Pérez

    2009-01-01

    Isolation of non-conventional starches has increased in the last decade; chemical modification of these no conventional starches may produce starches with improved physicochemical and functional properties that are not available from commercial starches. Banana starch was acetylated and oxidized and the thermal, pasting and rheological characteristics were evaluated. The low carbonyl and carboxyl groups might be due to the starch source. The acetylated banana starch obtained had a low degree ...

  9. Altering the interfacial activation mechanism of a lipase by solid-phase selective chemical modification.

    Science.gov (United States)

    López-Gallego, Fernando; Abian, Olga; Guisán, Jose Manuel

    2012-09-04

    This study presents a combined protein immobilization, directed mutagenesis, and site-selective chemical modification approach, which was used to create a hyperactivated semisynthetic variant of BTL2. Various alkane chains were tethered at three different positions in order to mimic the lipase interfacial activation exogenously triggered by detergents. Optimum results were obtained when a dodecane chain was introduced at position 320 by solid-phase site-selective chemical modification. The resulting semisynthetic variant showed a 2.5-fold higher activity than the wild-type nonmodified variant in aqueous conditions. Remarkably, this is the maximum hyperactivation ever observed for BTL2 in the presence of detergents such as Triton X-100. We present evidence to suggest that the endogenous dodecane chain hyperactivates the enzyme in a similar fashion as an exogenous detergent molecule. In this way, we also observe a faster irreversible enzyme inhibition and an altered detergent sensitivity profile promoted by the site-selective chemical modification. These findings are also supported by fluorescence studies, which reveal that the structural conformation changes of the semisynthetic variant are different to those of the wild type, an effect that is more pronounced in the presence of detergent. Finally, the optimal immobilized semisynthetic variant was successfully applied to the selective synthesis of oxiran-2-yl butyrate. Significantly, this biocatalyst is 12-fold more efficient than the immobilized wild-type enzyme, producing the S-enantiomer with higher enantiospecificity (ee = 92%).

  10. FE-SEM COMPARATIVE STUDY ON SURFACE MODIFICATION OF WOOL FIBER AFTER DIFFERENT CHEMICAL TREATMENTS

    Directory of Open Access Journals (Sweden)

    BONET-ARACIL Marilés

    2016-05-01

    Full Text Available Wool surface comprehends numerous scales which are responsible of certain undesirable behavior of this fiber during its use and maintenance. One of the most significant issues is related to shrinkage, caused during washing, as a consequence of friction between the fibers. Chemical modification of wool is considered a useful option to avoid these kind of circumstances. During the last years, multiple alternatives for chemical modification of wool have been studied, comprising enzymes or acids amongst others. In this case of study, three different treatments were carried out in order to evaluate wool morphological appearance. The first treatment was an oxidative procedure, containing Basolan DC and sodium acetate as the main components. The second treatment was accomplished using Lanaperm VPO, a commercial finishing agent for wool fiber that claims to soften its surface. The third finishing process was performed employing Siligen FA, a commercial agent intended to act as an antimigrant for dye baths and also provide a smoother and regular surface. After said treatments, microphotographs of all treated and untreated fibers were taken so that a comparison between final appearance could be done. Analyzing results and conclusions, it can be stated that chemical modification of fiber does change its surface appearance and, consequently, its behaviour. Oxidation, Lanaperm, Siligen, wool cuticle, scales

  11. Soft X-ray induced chemical modification of polysaccharides in vascular plant cell walls

    Energy Technology Data Exchange (ETDEWEB)

    Cody, George D. [Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington, DC 20015 (United States)], E-mail: cody@gl.ciw.edu; Brandes, Jay [Skidaway Institute of Oceangraphy, Savannah, GA (United States); Jacobsen, Chris; Wirick, Susan [Department of Physics, State University of New York, Stony Brook, NY (United States)

    2009-03-15

    Scanning transmission X-ray microscopy and micro carbon X-ray Absorption Near Edge Spectroscopy (C-XANES) can provide quantitative information regarding the distribution of the biopolymers cellulose, hemicellulose, and lignin in vascular plant cell walls. In the case of angiosperms, flowering plants, C-XANES may also be able to distinguish variations in lignin monomer distributions throughout the cell wall. Polysaccharides are susceptible to soft X-ray irradiation induced chemical transformations that may complicate spectral analysis. The stability of a model polysaccharide, cellulose acetate, to variable doses of soft X-rays under conditions optimized for high quality C-XANES spectroscopy was investigated. The primary chemical effect of soft X-ray irradiation on cellulose acetate involves mass loss coincident with de-acetylation. A lesser amount of vinyl ketone formation also occurs. Reduction in irradiation dose via defocusing does enable high quality pristine spectra to be obtained. Radiation induced chemical modification studies of oak cell wall reveals that cellulose and hemicellulose are less labile to chemical modification than cellulose acetate. Strategies for obtaining pristine C-XANES spectra of polysaccharides are presented.

  12. Dissection of the DNA Mimicry of the Bacteriophage T7 Ocr Protein using Chemical Modification

    Science.gov (United States)

    Stephanou, Augoustinos S.; Roberts, Gareth A.; Cooper, Laurie P.; Clarke, David J.; Thomson, Andrew R.; MacKay, C. Logan; Nutley, Margaret; Cooper, Alan; Dryden, David T.F.

    2009-01-01

    The homodimeric Ocr (overcome classical restriction) protein of bacteriophage T7 is a molecular mimic of double-stranded DNA and a highly effective competitive inhibitor of the bacterial type I restriction/modification system. The surface of Ocr is replete with acidic residues that mimic the phosphate backbone of DNA. In addition, Ocr also mimics the overall dimensions of a bent 24-bp DNA molecule. In this study, we attempted to delineate these two mechanisms of DNA mimicry by chemically modifying the negative charges on the Ocr surface. Our analysis reveals that removal of about 46% of the carboxylate groups per Ocr monomer results in an ∼ 50-fold reduction in binding affinity for a methyltransferase from a model type I restriction/modification system. The reduced affinity between Ocr with this degree of modification and the methyltransferase is comparable with the affinity of DNA for the methyltransferase. Additional modification to remove ∼ 86% of the carboxylate groups further reduces its binding affinity, although the modified Ocr still binds to the methyltransferase via a mechanism attributable to the shape mimicry of a bent DNA molecule. Our results show that the electrostatic mimicry of Ocr increases the binding affinity for its target enzyme by up to ∼ 800-fold. PMID:19523474

  13. Identification of Hop stunt viroid infecting Citrus limon in China using small RNAs deep sequencing approach.

    Science.gov (United States)

    Su, Xiu; Fu, Shuai; Qian, Yajuan; Xu, Yi; Zhou, Xueping

    2015-07-07

    The advent of next generation sequencing technology has allowed for significant advances in plant virus discovery, particularly for identification of covert viruses and previously undescribed viruses. The Citrus limon Burm. f. (C. limon) is a small evergreen tree native to Asia, and . China is the world's top lemon-producing nation. In this work, lemon samples were collected from southwestern of China, where an unknown disease outbreak had caused huge losses in the lemon production industry. Using high-throughput pyrosequencing and the assembly of small RNAs, we showed that the Hop stunt viroid (HSVd) was present in C. limon leaf sample. The majority of it is a main lemon producing agricultural cultivarHop stunt viroid derived siRNAs (HSVd-siRNAs) in C. limon were 21 nucleotides in length, and nearly equal amount of HSVd-siRNAs originated from the plus-genomic RNA strand as from the complementary strand. A bias of HSVd-siRNAs toward sequences beginning with a 5'-Guanine was observed. Furthermore, hotspot analysis showed that a large amount of HSVd-siRNAs derived from the central and variant domains of the HSVd genome. Our results suggest that C. limon could set up a small RNA-mediated gene silencing response to Hop stunt viroid, Interestingly, based on bioinformatics analysis, our results also suggest that the large amounts of HSVd-siRNAs from central and variant domains might be involved in interference with host gene expression and affect symptom development.

  14. 77 FR 42721 - Limon Wind, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for...

    Science.gov (United States)

    2012-07-20

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Limon Wind, LLC; Supplemental Notice That Initial Market-Based Rate Filing...-referenced proceeding, of Limon Wind, LLC's application for market-based rate authority, with an accompanying...

  15. 77 FR 42721 - Limon Wind II, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request...

    Science.gov (United States)

    2012-07-20

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Limon Wind II, LLC; Supplemental Notice That Initial Market- Based Rate...-referenced proceeding, of Limon Wind II, LLC's application for market-based rate authority, with an...

  16. Chemical modification of coating of Pinus halepensis pollen by ozone exposure.

    Science.gov (United States)

    Naas, Oumsaad; Mendez, Maxence; Quijada, Melesio; Gosselin, Sylvie; Farah, Jinane; Choukri, Ali; Visez, Nicolas

    2016-07-01

    Pollen coating, located on the exine, includes an extractible lipid fraction. The modification of the pollen coating by air pollutants may have implications on the interactions of pollen with plant stigmas and human cells. Pinus halepensis pollen was exposed to ozone in vitro and the pollen coating was extracted with organic solvent and analyzed by GC-MS. Ozone has induced chemical changes in the coating as observed with an increase in dicarboxylic acids, short-chain fatty acids and aldehydes. 4-Hydroxybenzaldehyde was identified as the main reaction product and its formation was shown to occur both on native pollen and on defatted pollen. 4-Hydroxybenzaldehyde is very likely formed via the ozonolysis of acid coumaric-like monomers constitutive of the sporopollenin. Modification of pollen coating by air pollutants should be accounted for in further studies on effect of pollution on germination and on allergenicity.

  17. Physico-chemical Modification of the Fibrous Filter Nozzles for Purification Processes of Water and Air

    Science.gov (United States)

    Bordunov, S. V.; Galtseva, O. V.; Natalinova, N. M.; Rogachev, A. A.; Zhang, Ruizhi

    2017-01-01

    A set of experiments to study physical and chemical modification of the surface of fibers is conducted to expand the area of their application for purification of water, gas and air (including that in conditions of space). The possibility of modification of filter nozzles in the process of fiber formation by particles of coal of BAU type, copper sulfide and silver chloride is experimentally shown. The fraction of the copper sulfide powder less than 50 microns in size was crushed in a spherical mill; it was deposited on fiber at air temperature of 50° C and powder consumption of 0.5 g/l of air. The resulting material contained 6–18 CuS particles per 1 cm of the fiber length. An effective bactericidal fibrous material can be produced using rather cheap material – CuS and relatively cheap natural compounds of sulphides and oxides of heavy metals.

  18. Highly luminescent mono- and multilayers of immobilized CdTe nanocrystals: controlling optical properties through post chemical surface modification.

    Science.gov (United States)

    Tsuruoka, Takaaki; Takahashi, Rena; Nakamura, Toshihiro; Fujii, Minoru; Akamatsu, Kensuke; Nawafune, Hidemi

    2008-04-14

    The significant fluorescence enhancement of immobilized CdTe nanocrystals through chemical surface modifications is described, enabling us to fabricate stable, highly luminescent thin films and patterns of nanocrystal mono- and mutilayers.

  19. Chemical modifications and bioconjugate reactions of nanomaterials for sensing, imaging, drug delivery and therapy.

    Science.gov (United States)

    Biju, Vasudevanpillai

    2014-02-07

    As prepared nanomaterials of metals, semiconductors, polymers and carbon often need surface modifications such as ligand exchange, and chemical and bioconjugate reactions for various biosensor, bioanalytical, bioimaging, drug delivery and therapeutic applications. Such surface modifications help us to control the physico-chemical, toxicological and pharmacological properties of nanomaterials. Furthermore, introduction of various reactive functional groups on the surface of nanomaterials allows us to conjugate a spectrum of contrast agents, antibodies, peptides, ligands, drugs and genes, and construct multifunctional and hybrid nanomaterials for the targeted imaging and treatment of cancers. This tutorial review is intended to provide an introduction to newcomers about how chemical and bioconjugate reactions transform the surface of nanomaterials such as silica nanoparticles, gold nanoparticles, gold quantum clusters, semiconductor quantum dots, carbon nanotubes, fullerene and graphene, and accordingly formulate them for applications such as biosensing, bioimaging, drug and gene delivery, chemotherapy, photodynamic therapy and photothermal therapy. Nonetheless, controversial reports and our growing concerns about toxicity and pharmacokinetics of nanomaterials suggest the need for not only rigorous in vivo experiments in animal models but also novel nanomaterials for practical applications in the clinical settings. Further reading of original and review articles cited herein is necessary to buildup in-depth knowledge about the chemistry, bioconjugate chemistry and biological applications of individual nanomaterials.

  20. CHEMICAL MODIFICATION AND CHARACTERIZATION OF PECTIN AS A POTENTIAL DRUG RELEASE RETARDANT

    Directory of Open Access Journals (Sweden)

    Harika Puppala Satya Krishna

    2011-02-01

    Full Text Available The present study deals with the chemical modification of pectin by acetylation of their free hydroxyl groups to yield high ester pectin and to evaluate its solubility and swelling behaviour along with the effect on the release pattern of the drug. Modified pectins were prepared by acetylation process using various strengths of 20%, 40% and 60% v/v acetyl chloride in ethanol. The prepared modified pectins were subjected to various physico-chemical characteristics like solubility, gelling studies, acid value, saponification value and ester value. FTIR studies were carried out to confirm the chemical modification of pectin. Matrix tablets of tramadol were formulated using various strengths of modified pectins in different concentrations and its impact on drug release was studied. All the formulated batches were subjected to weight variation, hardness, friability, drug content and the values obtained were within the acceptable range. The in-vitro drug release characteristics from the formulated tablets were compared with commercial sustained release tablet of tramadol. The optimized tablet formulation F4 sustained the drug release over a period of 8hours as comparable to the marketed product. Thus the synthesized modified pectin proved to be an ideal drug release retarding polymer.

  1. UV Spectral Analysis of the Chemical Modification and Photolysis of Acetylacetone Modified Alumina Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    Chengbin JING; Xiujian ZHAO; Haizheng TAO; Xina WANG; Aiyun LIU

    2004-01-01

    Acetylacetone was firstly introduced into the aqueous media with the presence of aluminum sec-butoxide and peptizator. It was confirmed that the UV (ultraviolet) absorption band of acetylacetone underwent 14 nm of red-shift due to the formation of the six-membered ring of the complex between alumina and acetylacetone in the aqueous solution. It was also found that the chemical modification can be dissociated by the UV irradiation with a wavelength shorter than 286 nm as a result of the excitation of π-π* transition in the complex.

  2. Chemical modification of cotton fabrics for improving utilization of reactive dyes.

    Science.gov (United States)

    Fang, Long; Zhang, Xiaodong; Sun, Deshuai

    2013-01-02

    The cotton fabric was chemically modified with the acrylamide through Michael addition reaction and Hoffman degradation reaction. And the optimum chemical modification conditions were determined. The molecular structure of the modified cotton fabric was identified by Fourier transform infrared spectroscopy (FTIR). The structures of both the raw and modified cotton fabrics were investigated by X-ray diffraction and scanning electronic microscopy. The raw and modified cotton fabrics were dyed using commercial reactive dyes with vinyl-sulfone groups. The results showed that the total dye utilization of modified cotton fabrics in the salt-free dyeing was higher than that of raw cotton fabrics in the conventional dyeing. And the color fastness properties and tear strength of modified fabrics were both satisfactory.

  3. Chemical composition and antibacterial activity of essential oils against human pathogenic bacteria

    NARCIS (Netherlands)

    Sokovic, M.; Marin, P.D.; Brkic, D.; Griensven, van L.J.L.D.

    2008-01-01

    The chemical composition and antibacterial activity of essential oils from 10 aromatic plants Matricaria chamommilla, Mentha piperita, M. spicata, Lavandula angustifolia, Ocimum basilicum, Thymus vulgaris, Origanum vulgare, Salvia officinalis, Citrus limon and C. aurantium have been determined. Anti

  4. Chemical composition and antibacterial activity of essential oils against human pathogenic bacteria

    NARCIS (Netherlands)

    Sokovic, M.; Marin, P.D.; Brkic, D.; Griensven, van L.J.L.D.

    2008-01-01

    The chemical composition and antibacterial activity of essential oils from 10 aromatic plants Matricaria chamommilla, Mentha piperita, M. spicata, Lavandula angustifolia, Ocimum basilicum, Thymus vulgaris, Origanum vulgare, Salvia officinalis, Citrus limon and C. aurantium have been determined.

  5. Cell adhesive and antifouling polyvinyl chloride surfaces via wet chemical modification.

    Science.gov (United States)

    Gabriel, Matthias; Strand, Dennis; Vahl, Christian-Friedrich

    2012-09-01

    Polyvinyl chloride (PVC) is one of the most frequently used polymers for the manufacturing of medical devices. Limitations for its usage are based upon unfavorable surface properties of the polymer including its hydrophobicity and lack of functionalities in order to increase its versatility. To address this issue, wet chemical modification of PVC was performed through surface amination using the bifunctional compound ethylene diamine. The reaction was conducted in order to achieve maximum surface amination while leaving the bulk material unaffected. The initial activation step was characterized by means of various methods including contact angle measurements, colorimetric amine quantification, infrared spectroscopy, and gel permeation chromatography. Depth profiles were obtained by a confocal microscopic method using fluorescence labeling. Exclusive surface modification was thus confirmed. To demonstrate biological applications of the presented technique, two examples were chosen: The covalent immobilization of the cell adhesive Asp-Gly-Asp-Ser-peptide (RGD) onto PVC samples yielded a surface that strongly supported cellular adhesion and proliferation of fibroblasts. In contrast, the decoration of PVC with the hydrophilic polymer polyethylene glycol prevented cellular adhesion to a large extent. The impact of these modifications was demonstrated by cell culture experiments.

  6. Chemical Modifications of Cassava Peel as Adsorbent Material for Metals Ions from Wastewater

    Directory of Open Access Journals (Sweden)

    Daniel Schwantes

    2016-01-01

    Full Text Available Residues from the processing of cassava roots (Manihot esculenta Crantz, or cassava peels, are evaluated as chemically modified adsorbents with H2O2, H2SO4, and NaOH, in the removal of metal ions Cd(II, Pb(II, and Cr(III from contaminated water. Modified adsorbents were chemically characterized for their chemical composition and pHPZC (point of zero charge, while adsorption tests determined the best conditions of pH, adsorbent mass, and contact time between adsorbent and adsorbate in the process of removal of the metal ions. Isotherms obtained from the preliminary results were linearized by Langmuir’s and Freudlich’s models. The thermodynamic parameters, such as ΔH, ΔG, and ΔS, were also evaluated. The modifying solutions proposed were effective in the modification of adsorbents and resulted in high capacity sorption materials. Equilibrium time between adsorbent and adsorbate for the solutions contaminated with metals is about 40 minutes. The Langmuir model adjusted to most results, indicating monolayers adsorption of Cd(II, Pb(II, and Cr(III. The values obtained for Langmuir Qm show a higher adsorption capacity caused by chemical modifications, with values such as 19.54 mg Cd(II per g of M. NaOH, 42.46 mg of Pb(II per g of M. NaOH, and 43.97 mg of Cr(III per g of M H2O2. Results showed that modified cassava peels are excellent adsorbent, renewable, high availability, and low-cost materials and a feasible alternative in the removal of metals in industries.

  7. Chemical modification of glycerinated stalks shows tyrosine residues essential for spasmoneme contraction of Vorticella sp.

    Science.gov (United States)

    Fang, Jie; Zhang, Bei; Chen, Ning; Asai, Hiroshi

    2004-05-01

    Chemical modification of glycerinated stalks of Vorticella with TNM is used to investigate the role of tyrosine residues in the Ca(2+)-induced contraction of the spasmoneme. Tetranitromethane (TNM) is often employed as a specific reagent for the nitration of tyrosine residues in a protein at neutral and slightly alkaline pHs although TNM can also oxidize cysteine residues in the acidic and neutral pH range. Prior incubation with Ca(2+) of stalks to be treated with TNM can protect the spasmoneme from irreversible denaturation. On the other hand, TNM treatment in the absence of free Ca(2+) causes an irreversible denaturation of the spasmoneme. It was revealed by us that an isolated Ca(2+)-binding protein called spasmin could not bind with Ca(2+) after TNM treatment, even if the treatment was performed in the presence of Ca(2+). In an additional experiment, we confirmed that the chemical modification of cysteine residues in the spasmoneme with N-7-dimethyl-amino-4methyl- coumarinyl- maleimide (DACM) has no effect on the contractibility. These results suggest that tyrosine residues in spasmin are essential for spasmoneme contraction and are protected from TNM in the presence of Ca(2+) when spasmin binds with its receptor protein in the spasmoneme.

  8. Engineering specific chemical modification sites into a collagen-like protein from Streptococcus pyogenes.

    Science.gov (United States)

    Stoichevska, Violet; Peng, Yong Y; Vashi, Aditya V; Werkmeister, Jerome A; Dumsday, Geoff J; Ramshaw, John A M

    2017-03-01

    Recombinant bacterial collagens provide a new opportunity for safe biomedical materials. They are readily expressed in Escherichia coli in good yield and can be readily purified by simple approaches. However, recombinant proteins are limited in that direct secondary modification during expression is generally not easily achieved. Thus, inclusion of unusual amino acids, cyclic peptides, sugars, lipids, and other complex functions generally needs to be achieved chemically after synthesis and extraction. In the present study, we have illustrated that bacterial collagens that have had their sequences modified to include cysteine residue(s), which are not normally present in bacterial collagen-like sequences, enable a range of specific chemical modification reactions to be produced. Various model reactions were shown to be effective for modifying the collagens. The ability to include alkyne (or azide) functions allows the extensive range of substitutions that are available via "click" chemistry to be accessed. When bifunctional reagents were used, some crosslinking occurred to give higher molecular weight polymeric proteins, but gels were not formed. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 806-813, 2017.

  9. Physico-chemical modifications of conjugated linoleic acid for ruminal protection and oxidative stability

    Directory of Open Access Journals (Sweden)

    Choi Yun-Jaie

    2008-06-01

    Full Text Available Abstract Conjugated linoleic acid (CLA is a mixture of positional and geometric isomers of octadecadienoic acid [linoleic acid (LA, 18:2n-6]. Although ruminant milk and meat products represent the largest natural source of CLA and therefore, their concentration in ruminant lipids are of interest to human health, chemical or physical modifications of CLA should be needed as a means to enhance oxidative stability, to improve post-ruminal bioavailability, and to increase the clinical application. In fact, CLA are rapidly decomposed to form furan fatty acids when its are oxidized in air, and the effectiveness of dietary supplements of CLA may be related to the extent that their metabolisms by rumen bacteria are avoided. For these reasons, many scientists have examined the effect of manufacturing and protection on the stability of CLA in ruminants and food products. In this review, physico-chemical modifications of CLA for ruminal protection such as calcium salt (Ca, formaldehyde protection (FP, lipid encapsulation (LE, and amide linkage (AL, and for oxidative stability such as green tea catechin (GTC, cyclodextrin (CD, arginine (Arg, amylase, and PEGylation are proposed.

  10. Physico-chemical modifications of conjugated linoleic acid for ruminal protection and oxidative stability.

    Science.gov (United States)

    Moon, Hyun-Seuk; Lee, Hong-Gu; Chung, Chung-Soo; Choi, Yun-Jaie; Cho, Chong-Su

    2008-06-01

    Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of octadecadienoic acid [linoleic acid (LA), 18:2n-6]. Although ruminant milk and meat products represent the largest natural source of CLA and therefore, their concentration in ruminant lipids are of interest to human health, chemical or physical modifications of CLA should be needed as a means to enhance oxidative stability, to improve post-ruminal bioavailability, and to increase the clinical application. In fact, CLA are rapidly decomposed to form furan fatty acids when its are oxidized in air, and the effectiveness of dietary supplements of CLA may be related to the extent that their metabolisms by rumen bacteria are avoided. For these reasons, many scientists have examined the effect of manufacturing and protection on the stability of CLA in ruminants and food products. In this review, physico-chemical modifications of CLA for ruminal protection such as calcium salt (Ca), formaldehyde protection (FP), lipid encapsulation (LE), and amide linkage (AL), and for oxidative stability such as green tea catechin (GTC), cyclodextrin (CD), arginine (Arg), amylase, and PEGylation are proposed.

  11. Recent Progress in Chemical Modifications of Chlorophylls and Bacteriochlorophylls for the Applications in Photodynamic Therapy.

    Science.gov (United States)

    Staron, Jakub; Boron, Bożena; Karcz, Dariusz; Szczygieł, Małgorzata; Fiedor, Leszek

    2015-01-01

    Since photodynamic therapy emerged as a promising cancer treatment, the development of photosensitizers has gained great interest. In this context, the photosynthetic pigments, chlorophylls and bacteriochlorophylls, as excellent natural photosensitizers, attracted much attention. In effect, several (bacterio) chlorophyll-based phototherapeutic agents have been developed and (or are about to) enter the clinics. The aim of this review article is to give a survey of the advances in the synthetic chemistry of these pigments which have been made over the last decade, and which are pertinent to the application of their derivatives as photosensitizers for photodynamic therapy (PDT). The review focuses on the synthetic strategies undertaken to obtain novel derivatives of (bacterio)chlorophylls with both enhanced photosensitizing and tumorlocalizing properties, and also improved photo- and chemical stability. These include modifications of the C- 17-ester moiety, the isocyclic ring, the central binding pocket, and the derivatization of peripheral functionalities at the C-3 and C-7 positions with carbohydrate-, peptide-, and nanoparticle moieties or other residues. The effects of these modifications on essential features of the pigments are discussed, such as the efficiency of reactive oxygen species generation, photostability, phototoxicity and interactions with living organisms. The review is divided into several sections. In the first part, the principles of PDT and photosensitizer action are briefly described. Then the relevant photophysical features of (bacterio)chlorophylls and earlier approaches to their modification are summarized. Next, a more detailed overview of the progress in synthetic methods is given, followed by a discussion of the effects of these modifications on the photophysics of the pigments and on their biological activity.

  12. Influence of Chemical Surface Modification of Woven Fabrics on Ballistic and Stab Protection of Multilayer Packets

    Directory of Open Access Journals (Sweden)

    Diana GRINEVIČIŪTĖ

    2014-06-01

    Full Text Available In order to achieve enhanced protective and wear (flexibility, less bulkiness properties of ballistic and stab protecting panels the investigation of chemical surface modification of woven p-aramid fabrics was performed applying different chemical composition shear thickening fluid (STF which improves friction inside fabric structure. For the chemical treatment silicic acid and acrylic dispersion water solutions were used and influence of their different concentrations on panels’ protective properties were investigated. Results of ballistic tests of multilayer protective panel have revealed that shear thickening effect was negligible when shooting at high energy range (E > 440 J. Determination of stab resistance of p-aramid panels has shown that different chemical composition of STFs had different influence on protective properties of the panels. Application of low concentrations of silicic acid determined higher stab resistance values comparing to higher concentrations of acrylic dispersion water solutions. At this stage of research stab tests results as ballistic ones determined that STF application for multilayer p-aramid fabrics protective panels is more efficient at low strike energy levels. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.3138

  13. Chemical modification and organelle-specific localization of orlistat-like natural-product-based probes.

    Science.gov (United States)

    Yang, Peng-Yu; Liu, Kai; Zhang, Chongjing; Chen, Grace Y J; Shen, Yuan; Ngai, Mun Hong; Lear, Martin J; Yao, Shao Q

    2011-10-04

    Orlistat, also known as tetrahydrolipstatin (THL), is an FDA-approved anti-obesity drug with potential anti-cancer activity. Previously, we developed a chemical proteomic approach, based on the Orlistat-like probe (1a) for large-scale identification of unknown cellular targets of Orlistat in human hepatocytes. In this article, we report the chemical synthesis and biological evaluation of an expanded set of Orlistat-like compounds, with the intention to further dissect and manipulate potential cellular targets of Orlistat. In doing so, we carried out proteome-wide activity-based profiling and large-scale pull-down/LCMS analysis of these compounds in live HepG2 cells, and successfully identified many putative cellular targets for Orlistat and its structural analogues. By qualitatively assessing the spectra counts of potential protein hits against each of the seventeen Orlistat analogues, we obtained both common and unique targets of these probes. Our results revealed that subtle structural modifications of Orlistat led to noticeable changes in both the cellular potency and target profiles of the drug. In order to further improve the cellular activity of Orlistat, we successfully applied the well-established AGT/SNAP-tag technology to our cell-permeable, benzylguanine (BG)-containing Orlistat variant (4). We showed that the drug could be delivered and effectively retained in different sub-cellular organelles of living cells. This strategy may provide a general and highly effective chemical tool for the potential sub-cellular targeting of small molecule drugs.

  14. Physical and chemical basics of modification of poly(vinyl chloride) by means of polyisocyanate

    Science.gov (United States)

    Islamov, Anvar; Fakhrutdinova, Venera; Abdrakhmanova, Lyailya

    2016-01-01

    This research presents data relating to polyvinyl chloride (PVC) modification by means of reactive oligomer and measures technological, physical and mechanical properties of the modified composites. Polyisocyanate (PIC) has been chosen as the modifying reactive oligomer. It has been shown that insertion of the oligomer has a double effect on PVC. Primarily, PIC produces a plasticizing effect on PVC and in particular leads to an increase in thermal stability and melt flow index at the stage of processing. In addition, the molded PVC composites possess higher strength properties and lower deformability when exposed to temperature because of chemical transformations of PIC in polymer matrix and, as the result, the formation of cross-linked systems takes place. In this case, semi-interpenetrating structures are formed based on cross-linked products of PIC chemical transformations homogeneously distributed in the PVC matrix. It has been determined by means of IR-spectroscopy that the basic products of PIC curing are compounds with urea and biuret groups which leads to modifying effect on PVC especially: increase in strength, thermal and mechanical properties, and chemical resistance.

  15. In vitro and in vivo effect of Citrus limon essential oil against sarcoptic mange in rabbits

    Science.gov (United States)

    The effect of lemon oil (Citrus limon) on Sarcoptes scabiei var. cuniculi was evaluated in vitro and in vivo. The mite samples were collected from naturally infected rabbits. The lemon oil was prepared in six concentrations by dilution with distilled water (2.5, 5, 10, 20, 50, and 100 %). In vitro a...

  16. Hepatoprotective Effect of Citrus limon Fruit Extract against Carbofuran Induced Toxicity in Wistar Rats

    Directory of Open Access Journals (Sweden)

    Sunil Kumar Jaiswal

    2015-01-01

    Full Text Available Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranol methylcarbamate, is known to induce oxidative stress and to cause inhibition of acetylcholinesterase activity. The present work was envisaged to evaluate the effect of carbofuran on redox indices and its interactions with hepatic markers in rat. The ameliorating effect of Citrus limon fruit extract on carbofuran induced toxicity was also monitored. The results indicated that carbofuran treatment caused significant alterations in the levels of activities of AST, ALT, and LDH in liver tissues and serum. The levels of enzymatic oxidative stress markers such as SOD and catalase and nonenzymatic redox molecules such as total thiol, GSH, and protein thiol also showed significant perturbations in rat liver due to carbofuran treatment. The administration of Citrus limon fruit extract, however, was able to markedly ameliorate the toxicity of carbofuran by protecting the levels of aforesaid biomarkers to near normal levels. The ameliorative effect of Citrus limon fruit extract may be due to the presence of different antioxidants in it which may neutralize the ROS and RNS generated in the body tissue due to pesticide stress. These results suggested that Citrus limon fruit extract may be utilized as a potential supplement in proper management of pesticide intoxication in association with relevant therapeutics.

  17. Domain swapping of Citrus limon monoterpene synthases: impact on enzymatic activity and product specifity.

    NARCIS (Netherlands)

    Tamer, el M.K.; Lucker, J.; Bosch, D.; Verhoeven, H.A.; Verstappen, F.W.A.; Schwab, W.; Tunen, van A.J.; Voragen, A.G.J.; Maagd, de R.A.; Bouwmeester, H.J.

    2003-01-01

    Monoterpene cyclases are the key enzymes in the monoterpene biosynthetic pathway, as they catalyze the cyclization of the ubiquitous geranyl diphosphate (GDP) to the specific monoterpene skeletons. From Citrus limon, four monoterpene synthase-encoding cDNAs for a P-pinene synthase named

  18. Electronic structure of the layered nitride LiMoN2

    Science.gov (United States)

    Singh, D. J.

    1992-10-01

    Electronic-structure calculations are reported for the layered ternary nitride LiMoN2. It is found that the material is best described as a three-dimensional metal consisting of strongly covalent MoN2 sheets and Li ions between them. Highly unusual strong direct bonding between N atoms in opposing layers is found.

  19. Domain swapping of Citrus limon monoterpene synthases: impact on enzymatic activity and product specifity.

    NARCIS (Netherlands)

    Tamer, el M.K.; Lucker, J.; Bosch, D.; Verhoeven, H.A.; Verstappen, F.W.A.; Schwab, W.; Tunen, van A.J.; Voragen, A.G.J.; Maagd, de R.A.; Bouwmeester, H.J.

    2003-01-01

    Monoterpene cyclases are the key enzymes in the monoterpene biosynthetic pathway, as they catalyze the cyclization of the ubiquitous geranyl diphosphate (GDP) to the specific monoterpene skeletons. From Citrus limon, four monoterpene synthase-encoding cDNAs for a P-pinene synthase named Cl(-)betaPIN

  20. Evaluation of central nervous system effects of Citrus limon essential oil in mice

    Directory of Open Access Journals (Sweden)

    Lidianne Mayra Lopes Campêlo

    2011-08-01

    Full Text Available The central nervous system (CNS depressant and anticonvulsant activities of Citrus limon (L. Osbeck, Rutaceae, essential oil (EO were investigated in animal models. The EO (50, 100 and 150 mg/kg injected by oral route (p.o. in mice caused a significant decrease in the motor activity of animals when compared with the control group, up to thirty days after the administration and the dose of 150 mg/kg significantly reduced the remaining time of the animals on the Rota-rod apparatus. Additionally, C. limon essential oil was also capable to promote an increase of latency for development of convulsions induced by pentylenetetrazole (PTZ. The administration of FLU (10 mg/kg, i.p., GABA A-benzodiazepine (GABA-BZD receptor antagonist, antagonized the effect of C. limon essential oil at higher dose. This C. limon essential oil was also capable to promote an increase of latency for development of convulsions induced by picrotoxin (PIC at higher dose. In the same way, the anticonvulsant effect of the EO was affected by pretreatment with flumazenil, a selective antagonist of benzodiazepine site of GABA A receptor. These results suggest a possible CNS depressant and anticonvulsant activities in mice that needs further investigation.

  1. Surface modification of poly(ethylene terephthalate) fabric via photo-chemical reaction of dimethylaminopropyl methacrylamide

    Science.gov (United States)

    Mohamed, Nasser H.; Bahners, Thomas; Wego, Andreas; Gutmann, Jochen S.; Ulbricht, Mathias

    2012-10-01

    Photo-chemical reactions and surface modifications of poly(ethylene terephthalate) (PET) fabrics with the monomer dimethylaminopropyl methacrylamide (DMAPMA) and benzophenone (BP) as photo-initiator using a broad-band UV lamp source were investigated. The tertiary amino groups of the grafted poly(DMAPMA) chains were subsequently quaternized with alkyl bromides of different chain lengths to establish antibacterial activity. The surface composition, structure and morphology of modified PET fabrics were characterized by Fourier transform infrared spectroscopy (FTIR/ATR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). To evaluate the amount of quaternary and tertiary ammonium groups on the modified surface, PET was dyed with an acid dye which binds to the ammonium groups. Therefore, the color depth is a direct indicator of the amount of ammonium groups. The resulting antibacterial activity of the modified PET fabrics was tested with Escherichia coli. The results of all experiments show that a photochemical modification of PET is possible using DMAPMA, benzophenone and UV light. Also, the quaternization of tertiary amino groups as well as the increase in antibacterial activity of the modified PET by the established quaternary ammonium groups were successful.

  2. Nanolithography and nanochemistry: probe-related patterning techniques and chemical modification for nanometer-sized devices.

    Science.gov (United States)

    Wouters, Daan; Schubert, Ulrich S

    2004-05-01

    The size regime for devices produced by photolithographic techniques is limited. Therefore, other patterning techniques have been intensively studied to create smaller structures. Scanning-probe-based patterning techniques, such as dip-pen lithography, local force-induced patterning, and local-probe oxidation-based techniques are highly promising because of their relative ease and widespread availability. The latter of these is especially interesting because of the possibility of producing nanopatterns for a broad range of chemical and physical modification and functionalization processes; both the production of nanometer-sized electronic devices and the formation of devices involving (bio)molecular recognition and sensor applications is possible. This Review highlights the development of various scanning probe systems and the possibilities of local oxidation methods, as well as giving an overview of state-of-the-art nanometer-sized devices, and a view of future development.

  3. Enhancing the properties of wood through chemical modification with palmitoyl chloride

    Science.gov (United States)

    Prakash, Gowdra K.; Mahadevan, Kittappa M.

    2008-01-01

    Hevea brassiliensis (rubber wood) was esterified with palmitoyl chloride, prepared from the reaction of palmitic acid with thionyl chloride. The weight gain of the wood increased with increasing reaction time and temperature, the esterified wood were evaluated for their photostability and dimensional stability. Fourier transform infrared spectroscopy (FTIR), solid-state cross-polarization/magic angle spinning 13C nuclear magnetic resonance spectroscopy (CP/MAS 13C NMR) were used to elucidate the characteristics of wood after esterification. The dimensional stability and photostability of the wood was improved by esterification. This is an important observation since chemical modification of wood with fatty acid chlorides has been found to induce thermo-plasticity into wood.

  4. Basic and Reactive Dyes Sorption Enhancement of Rice Hull through Chemical Modification

    Directory of Open Access Journals (Sweden)

    Siew-Teng Ong

    2010-01-01

    Full Text Available Problem statement: Many studies have been conducted on the removal of either anionic or cationic dyes. However, as a mixture of dyes does commonly exist together in wastewater, therefore it is of great interest to have a material that can remove both types of dyes. Approach: To prepare an inexpensive and efficient sorbent by chemically modifying rice hull for the removal of both basic and reactive dyes. Different chemical modifications were performed on rice hull and a comparison study on the uptake of dyes was carried out. Optimization study was carried out on most promising modified rice hull. Surface morphology of modified rice hull was examined and the functional groups present were determined using FTIR. Results: From the results, it appeared that by using EDA modified rice hull, an appreciable amount of both dyes could be sorbed. Varying the EDA/NRH ratios and heating temperatures affected the uptake of BB3 and RO16. The investigated sorbents were non-porous materials, due to the absence of pores and cavities. Sorption-desorption study showed that a complete recovery of BB3 can be obtained using high concentrations of H2SO4 and HCl but the desorption experiments of RO16 using NH3 and NaOH were not successful. Conclusion: The modification of rice hull with EDA under the optimum conditions (in a ratio of 1.00 g of NRH to 0.02 mole of EDA in a well stirred water bath at 80°C for 2 h resulted in the formation of a sorbent (MRH that could be used successfully to remove Both Basic (BB3 and Reactive dyes (RO16.

  5. Studies on the chemical modification of goat liver cystatin and the effect on its anti-papain inhibitory activity.

    Science.gov (United States)

    Shah, Aaliya; Aatif, Mohammad; Priyadarshini, Medha; Khan, Mohd Shahnawaz; Amin, Fakhra; Bano, Bilqees

    2012-11-01

    Goat liver cystatin was subjected to various chemical modifications in order to ascertain the amino acid residues responsible for its structural and functional integrity. Modification of tryptophan by HNBB led to the complete inactivation of the protein. The inactivation was also accompanied by the complete loss of tryptophan fluorescence at 340 nm. The reaction of liver cystatin with HNBB yielded a characteristic decrease in absorbance at 280 nm. Acetylation of the amino groups of liver cystatin was carried out in the presence of acetic anhydride. The acetylated cystatin showed a decrease in fluorescence intensity at 335 nm which could be attributed to the modification of tyrosine residue due to side reaction.

  6. Behavioral effects of Citrus limon and Punica granatum combinations in rats.

    Science.gov (United States)

    Riaz, Azra; Khan, Rafeeq Alam

    2017-02-01

    Dietary supplements are becoming more influential as viable treatment for common chronic diseases and to promote normal development and functions of all system including brain. Disorders like anxiety and depression may be managed through healthier variations is dietary pattern, since there are indications that diet rich in antioxidants and vitamins diminish anxiety and depression. Hence this investigation was planned to assess the behavioral effects of Citrus limon and Punica granatum in two combination doses i.e. 0.4 + 5 ml/kg and 0.2 + 8 ml/kg C. limon and P. granatum respectively in rats. Antidepressant and anxiolytic effects were explicitly judged twice during 15 days using forced swimming and open field tests and elevated plus maze. In open field test C. limon and P. granatum showed increase in distance travelled, number of central entries and number of rearing's at 0.4 + 5 ml/kg combination, in the elevated plus maze, number of open arm entries were found to be augmented and in forced swimming test, there was decline in duration of immobility and rise in duration of climbing at both combinations i.e. 0.4 + 5 ml/kg and 0.2 + 8 ml/kg C. limon and P. granatum. These results suggest that C. limon and P. granatum at 0.4 + 5 ml/kg combination have anxiolytic and antidepressant effect.

  7. Fungal inhibitory effect of Citrus Limon peel essential oil on Candida albicans

    Directory of Open Access Journals (Sweden)

    Iwan Hernawan

    2015-06-01

    Full Text Available Background: Oral candidiasis is an opportunistic infections due to Candida albicans that often found in people with HIV/AIDS. Anti-fungi, polyne and azole, are used in the treatment of oral candidiasis, but often cause persistence and recurrence. Citrus Limon peel contains terpenoids capable of inhibiting the synthesis of ergosterol, a component of the fungal cell wall that helps to maintain cell membrane permeability. Essential oil derived from citrus limon peel, thus, is expected to inhibit the growth of Candida albicans. Purpose: This research was aimed to know how essential oil derived from citrus Limon peel can inhibit the growth of Candida albicans. Method: This research was a laboratory experimental research carried out in three phases. First, essential oil was made with cold pressing method, and then the concentration of 100% was diluted to 50%, 12.5%, 6.25%, 3.125%, 1.56% and 0.78%. A test was conducted on the culture of Candida albicans in Sabouraud broth, accompanied by control (+ and (-. Second, the dilution of essential oil was conducted to alter the concentration with inhibitory power, from the strongest one to the weakest one, and then it was tested on the culture of Candida albicans. Third, spreading was carried out from liquid culture to agar media in order to measure the number of colonies. Result: Candida albicans did not grow on media with 100% essential oil treatment, but it grew on media with 50% essential oil treatment. In the second phase, dilution of 100%, 90%, 80%, 70%, 60% and 50% was conducted. The growth of Candida albicans was found on the treatment media of 60% and 50%. On the agar media, the growth occurred in the cultured medium treated with 70%. Conclusion: The minimum inhibitory power of essential oil derived from citrus Limon peel against Candida albicans was in the concentration of 80%. Essential oil derived from citrus Limon peel has antifungal effect and potential as a therapeutic agent for oral candidiasis.

  8. Glycan Reader is improved to recognize most sugar types and chemical modifications in the Protein Data Bank.

    Science.gov (United States)

    Park, Sang-Jun; Lee, Jumin; Patel, Dhilon S; Ma, Hongjing; Lee, Hui Sun; Jo, Sunhwan; Im, Wonpil

    2017-10-01

    Glycans play a central role in many essential biological processes. Glycan Reader was originally developed to simplify the reading of Protein Data Bank (PDB) files containing glycans through the automatic detection and annotation of sugars and glycosidic linkages between sugar units and to proteins, all based on atomic coordinates and connectivity information. Carbohydrates can have various chemical modifications at different positions, making their chemical space much diverse. Unfortunately, current PDB files do not provide exact annotations for most carbohydrate derivatives and more than 50% of PDB glycan chains have at least one carbohydrate derivative that could not be correctly recognized by the original Glycan Reader. Glycan Reader has been improved and now identifies most sugar types and chemical modifications (including various glycolipids) in the PDB, and both PDB and PDBx/mmCIF formats are supported. CHARMM-GUI Glycan Reader is updated to generate the simulation system and input of various glycoconjugates with most sugar types and chemical modifications. It also offers a new functionality to edit the glycan structures through addition/deletion/modification of glycosylation types, sugar types, chemical modifications, glycosidic linkages, and anomeric states. The simulation system and input files can be used for CHARMM, NAMD, GROMACS, AMBER, GENESIS, LAMMPS, Desmond, OpenMM, and CHARMM/OpenMM. Glycan Fragment Database in GlycanStructure.Org is also updated to provide an intuitive glycan sequence search tool for complex glycan structures with various chemical modifications in the PDB. http://www.charmm-gui.org/input/glycan and http://www.glycanstructure.org. wonpil@lehigh.edu. Supplementary data are available at Bioinformatics online.

  9. The effects of high electronic energy loss on the chemical modification of polyimide

    CERN Document Server

    SunYouMei; Jin Yun Fan; Liu Chang Long; LiuJie; Wang Zhi Guang; Zhang Qi; Zhu Zhi Yong

    2002-01-01

    In order to observe the role of electronic energy loss (dE/dX) sub e on chemical modification of polyimide (PI), the multi-layer stacks (corresponding to different dE/dX) were irradiated by different swift heavy ions (1.37 GeV Ar sup 4 sup 0 , 1.98 GeV Kr sup 8 sup 4 , 1.755 GeV Xe sup 1 sup 3 sup 6 and 2.636 GeV U sup 2 sup 3 sup 8) under vacuum and room temperature. The chemical changes of modified PI films were studied by Fourier transform infrared (FTIR) and ultraviolet/visible (UV/Vis) absorption spectroscopy. The degradation of PI was investigated in the fluence range from 1x10 sup 1 sup 0 to 5.5x10 sup 1 sup 2 ions/cm sup 2 and different electronic energy loss from 0.77 to 11.5 keV/nm. The FTIR results show the absorbance of the typical function group decrease exponentially as a function of fluence. The alkyne end group was found after irradiation and its formation radii were 5.6 and 5.9 nm corresponding to 8.8 and 11.5 keV/nm Xe irradiation respectively. UV/Vis analysis indicates the radiation induced...

  10. Chemical modifications accompanying blueschist facies metamorphism of Franciscan conglomerates, Diablo Range, California

    Science.gov (United States)

    Moore, Diane E.; Liou, J.G.; King, B.-S.

    1981-01-01

    As part of an investigation of blueschist-facies mineral parageneses in pebbles and matrix of some Franciscan metaconglomerates of the Diablo Range, California, textural and major-element chemical analyses were conducted on a number of igneous pebbles that comprise a range of rock types from granite and dacite to gabbro and basalt. Compositions of the igneous pebbles differ significantly from common igneous rocks, particularly with respect to Ca, K, Na, Si and H2O. The SiO2 and H2O contents are characteristically high and the K2O contents low. The CaO and Na2O contents may be relatively enriched or reduced in different pebbles. The igneous pebbles show little evidence of alteration prior to their incorporation into the Franciscan conglomerates, and the chemical modifications are considered to have been produced during metamorphism of the conglomerates to (lawsonite + albite + aragonite ?? jadeite)-bearing assemblages. The observed variations in the pebbles are shown to be functions of: (1) bulk chemistry; (2) the igneous mineral assemblage; (3) the stable metamorphic mineral assemblage; and (4) the composition of pore fluids in the conglomerates. The relative proportions of Mg and Fe in most of the pebbles apparently have been unaffected by the metamorphism, and these parameters, along with other textural and chemical factors, were used to determine the petrogenetic affinities of the igneous pebbles. The plutonic and most of the volcanic pebbles correspond to calc-alkaline rock series, whereas a few volcanic pebbles show apparent Fe-enrichment characteristic of tholeiitic rocks. A continental margin arc-batholith complex would be the best source for these igneous detrital assemblages. Conglomerates in local areas differ in igneous lithologies from conglomerates in other areas and probably differ somewhat in age, perhaps reflecting varying degrees of unroofing of such a complex during deposition of Franciscan sediments. ?? 1981.

  11. Surface modification of poly(ethylene terephthalate) fabric via photo-chemical reaction of dimethylaminopropyl methacrylamide

    Energy Technology Data Exchange (ETDEWEB)

    Mohamed, Nasser H. [Deutsches Textilforschungszentrum Nord-West e.V., Adlerstr. 1, 47798 Krefeld (Germany); Bahners, Thomas, E-mail: bahners@dtnw.de [Deutsches Textilforschungszentrum Nord-West e.V., Adlerstr. 1, 47798 Krefeld (Germany); Wego, Andreas [Deutsches Textilforschungszentrum Nord-West e.V., Adlerstr. 1, 47798 Krefeld (Germany); Gutmann, Jochen S. [Deutsches Textilforschungszentrum Nord-West e.V., Adlerstr. 1, 47798 Krefeld (Germany); Universitaet Duisburg-Essen, Physikalische Chemie, Universitaetsstr. 2, 45141 Essen (Germany); Ulbricht, Mathias [Deutsches Textilforschungszentrum Nord-West e.V., Adlerstr. 1, 47798 Krefeld (Germany); Universitaet Duisburg-Essen Technische Chemie II, Essen (Germany)

    2012-10-15

    Highlights: Black-Right-Pointing-Pointer PET fibers were UV-grafted with dimethylaminopropyl methacrylamide (DMAPMA). Black-Right-Pointing-Pointer The graft yield could be controlled by irradiation time and monomer concentration. Black-Right-Pointing-Pointer The tertiary amino groups of the grafted PDMAPMA were quaternized with alkyl bromides. Black-Right-Pointing-Pointer The quaternization reaction had a high yield, when bromides with shorter alkyl chain were employed. Black-Right-Pointing-Pointer The antimicrobial effect was highest, when samples were quaternized with 1-bromohexane and 1-bromooctane. - Abstract: Photo-chemical reactions and surface modifications of poly(ethylene terephthalate) (PET) fabrics with the monomer dimethylaminopropyl methacrylamide (DMAPMA) and benzophenone (BP) as photo-initiator using a broad-band UV lamp source were investigated. The tertiary amino groups of the grafted poly(DMAPMA) chains were subsequently quaternized with alkyl bromides of different chain lengths to establish antibacterial activity. The surface composition, structure and morphology of modified PET fabrics were characterized by Fourier transform infrared spectroscopy (FTIR/ATR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). To evaluate the amount of quaternary and tertiary ammonium groups on the modified surface, PET was dyed with an acid dye which binds to the ammonium groups. Therefore, the color depth is a direct indicator of the amount of ammonium groups. The resulting antibacterial activity of the modified PET fabrics was tested with Escherichia coli. The results of all experiments show that a photochemical modification of PET is possible using DMAPMA, benzophenone and UV light. Also, the quaternization of tertiary amino groups as well as the increase in antibacterial activity of the modified PET by the established quaternary ammonium groups were successful.

  12. Stormwater filtration of toxic heavy metal ions using lignocellulosic materials selection process, fiberization, chemical modification, and mat formation

    Science.gov (United States)

    James S. Han

    1999-01-01

    Lignocellulosic materials were evaluated for their effectiveness in filtering toxic heavy metals from stormwater. Kenaf, alfalfa, juniper, and aspen fibers were used as models to evaluate the effectiveness and limitations of chemical modification and the extent of fiber degradation. Individual and mixed aqueous solutions of nickel, copper, zinc, and cadmium in various...

  13. Mathematical modeling of chemical composition modification and etching of polymers under the atomic oxygen influence

    Science.gov (United States)

    Chirskaia, Natalia; Novikov, Lev; Voronina, Ekaterina

    2016-07-01

    Atomic oxygen (AO) of the upper atmosphere is one of the most important space factors that can cause degradation of spacecraft surface. In our previous mathematical model the Monte Carlo method and the "large particles" approximation were used for simulating processes of polymer etching under the influence of AO [1]. The interaction of enlarged AO particles with the polymer was described in terms of probabilities of reactions such as etching of polymer and specular and diffuse scattering of the AO particles on polymer. The effects of atomic oxygen on protected polymers and microfiller containing composites were simulated. The simulation results were in quite good agreement with the results of laboratory experiments on magnetoplasmadynamic accelerator of the oxygen plasma of SINP MSU [2]. In this paper we present a new model that describes the reactions of AO interactions with polymeric materials in more detail. Reactions of formation and further emission of chemical compounds such as CO, CO _{2}, H _{2}O, etc. cause the modification of the chemical composition of the polymer and change the probabilities of its consequent interaction with the AO. The simulation results are compared with the results of previous simulation and with the results of laboratory experiments. The reasons for the differences between the results of natural experiments on spacecraft, laboratory experiments and simulations are discussed. N. Chirskaya, M. Samokhina, Computer modeling of polymer structures degradation under the atomic oxygen exposure, WDS'12 Proceedings of Contributed Papers: Part III - Physics, Matfyzpress Prague, 2012, pp. 30-35. E. Voronina, L. Novikov, V. Chernik, N. Chirskaya, K. Vernigorov, G. Bondarenko, and A. Gaidar, Mathematical and experimental simulation of impact of atomic oxygen of the earth's upper atmosphere on nanostructures and polymer composites, Inorganic Materials: Applied Research, 2012, vol. 3, no. 2, pp. 95-101.

  14. Chemical modifications of polymer films induced by high energy heavy ions

    Science.gov (United States)

    Zhu, Zhiyong; Sun, Youmei; Liu, Changlong; Liu, Jie; Jin, Yunfan

    2002-06-01

    Polymer films including polyethylene terephthalate (PET), polystyrene (PS) and polycarbonate (PC) were irradiated at room temperature with ions of 35 MeV/u 40Ar, 25 MeV/u 84Kr, 15.1 MeV/u 136Xe and 11.4 MeV/u 238U to fluences ranging from 9×10 9 to 5.5×10 12 ions/cm 2. The radiation-induced chemical changes of the materials were investigated by Fourier-transform infrared (FTIR) and ultraviolet/visible spectroscopies. It is found that the absorbance in the ultraviolet and visible range induced by all irradiations follows a linear relationship with fluence. The radiation-induced absorbance normalized to one particle increases slowly with increasing of electronic energy loss below about 8 keV/nm followed by a sharp increase up to about 15 keV/nm above which saturation is reached. FTIR measurements reveal that the materials suffer serious degradation through bond breaking. The absorbance of the typical infrared bands decays exponentially with increase of ion fluence and the bond-disruption cross-section shows a sigmoid variation with electronic energy loss. In PET loss of crystallinity is attributed to the configuration transformation of the ethylene glycol residue from trans into the gauche. Alkyne end groups are induced in all the materials above certain electronic energy loss threshold, which is found to be about 0.8 keV/nm for PS and 0.4 keV/nm for PC. The production cross-section of alkyne end group increases with increasing of electronic energy loss and shows saturation at high electronic energy loss values. It is concluded that not only the physical processes but also the chemical processes of the energy deposition determine the modification of polymer.

  15. Chemical modifications of polymer films induced by high energy heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Zhiyong E-mail: zyzhu@impcas.ac.cn; Sun Youmei; Liu Changlong; Liu Jie; Jin Yunfan

    2002-06-01

    Polymer films including polyethylene terephthalate (PET), polystyrene (PS) and polycarbonate (PC) were irradiated at room temperature with ions of 35 MeV/u {sup 40}Ar, 25 MeV/u {sup 84}Kr, 15.1 MeV/u {sup 136}Xe and 11.4 MeV/u {sup 238}U to fluences ranging from 9x10{sup 9} to 5.5x10{sup 12} ions/cm{sup 2}. The radiation-induced chemical changes of the materials were investigated by Fourier-transform infrared (FTIR) and ultraviolet/visible spectroscopies. It is found that the absorbance in the ultraviolet and visible range induced by all irradiations follows a linear relationship with fluence. The radiation-induced absorbance normalized to one particle increases slowly with increasing of electronic energy loss below about 8 keV/nm followed by a sharp increase up to about 15 keV/nm above which saturation is reached. FTIR measurements reveal that the materials suffer serious degradation through bond breaking. The absorbance of the typical infrared bands decays exponentially with increase of ion fluence and the bond-disruption cross-section shows a sigmoid variation with electronic energy loss. In PET loss of crystallinity is attributed to the configuration transformation of the ethylene glycol residue from trans into the gauche. Alkyne end groups are induced in all the materials above certain electronic energy loss threshold, which is found to be about 0.8 keV/nm for PS and 0.4 keV/nm for PC. The production cross-section of alkyne end group increases with increasing of electronic energy loss and shows saturation at high electronic energy loss values. It is concluded that not only the physical processes but also the chemical processes of the energy deposition determine the modification of polymer.

  16. Negative thermal expansion in functional materials: controllable thermal expansion by chemical modifications.

    Science.gov (United States)

    Chen, Jun; Hu, Lei; Deng, Jinxia; Xing, Xianran

    2015-06-07

    Negative thermal expansion (NTE) is an intriguing physical property of solids, which is a consequence of a complex interplay among the lattice, phonons, and electrons. Interestingly, a large number of NTE materials have been found in various types of functional materials. In the last two decades good progress has been achieved to discover new phenomena and mechanisms of NTE. In the present review article, NTE is reviewed in functional materials of ferroelectrics, magnetics, multiferroics, superconductors, temperature-induced electron configuration change and so on. Zero thermal expansion (ZTE) of functional materials is emphasized due to the importance for practical applications. The NTE functional materials present a general physical picture to reveal a strong coupling role between physical properties and NTE. There is a general nature of NTE for both ferroelectrics and magnetics, in which NTE is determined by either ferroelectric order or magnetic one. In NTE functional materials, a multi-way to control thermal expansion can be established through the coupling roles of ferroelectricity-NTE, magnetism-NTE, change of electron configuration-NTE, open-framework-NTE, and so on. Chemical modification has been proved to be an effective method to control thermal expansion. Finally, challenges and questions are discussed for the development of NTE materials. There remains a challenge to discover a "perfect" NTE material for each specific application for chemists. The future studies on NTE functional materials will definitely promote the development of NTE materials.

  17. Advances in identification and validation of protein targets of natural products without chemical modification.

    Science.gov (United States)

    Chang, J; Kim, Y; Kwon, H J

    2016-05-04

    Covering: up to February 2016Identification of the target proteins of natural products is pivotal to understanding the mechanisms of action to develop natural products for use as molecular probes and potential therapeutic drugs. Affinity chromatography of immobilized natural products has been conventionally used to identify target proteins, and has yielded good results. However, this method has limitations, in that labeling or tagging for immobilization and affinity purification often result in reduced or altered activity of the natural product. New strategies have recently been developed and applied to identify the target proteins of natural products and synthetic small molecules without chemical modification of the natural product. These direct and indirect methods for target identification of label-free natural products include drug affinity responsive target stability (DARTS), stability of proteins from rates of oxidation (SPROX), cellular thermal shift assay (CETSA), thermal proteome profiling (TPP), and bioinformatics-based analysis of connectivity. This review focuses on and reports case studies of the latest advances in target protein identification methods for label-free natural products. The integration of newly developed technologies will provide new insights and highlight the value of natural products for use as biological probes and new drug candidates.

  18. Characterisation of waste derived biochar added biocomposites: chemical and thermal modifications

    Energy Technology Data Exchange (ETDEWEB)

    Das, Oisik [Department of Civil and Environmental Engineering, University of Auckland, Auckland 1142 (New Zealand); Sarmah, Ajit K., E-mail: a.sarmah@auckland.ac.nz [Department of Civil and Environmental Engineering, University of Auckland, Auckland 1142 (New Zealand); Zujovic, Zoran [School of Chemical Sciences, University of Auckland, Auckland 1142 (New Zealand); Bhattacharyya, Debes [Centre for Advanced Composite Materials, Department of Mechanical Engineering, University of Auckland, Auckland 1142 (New Zealand)

    2016-04-15

    A step towards sustainability was taken by incorporating waste based pyrolysed biochar in wood and polypropylene biocomposites. The effect of biochar particles on the chemistry and thermal makeup of the composites was determined by characterising them through an array of characterisation techniques such as 3D optical profiling, X-ray diffraction, transmission electron microscopy, electron spin/nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. It was observed that addition of biochar increased the presence of free radicals in the composite while also improving its thermal conductivity. Biochar particles did not interfere with the melting behaviour of polymer in the thermal regime. However, wood and biochar acted as nucleation agents consequently increasing the crystallisation temperature. The crystal structure of polypropylene was not disrupted by biochar inclusion in composite. Transmission electron microscopy images illustrated the aggregated nature of the biochar particles at higher loading levels. Nuclear magnetic resonance studies revealed the aromatic nature of biochar and the broadening of peak intensities of composites with increasing biochar levels due to its amorphous nature and presence of free radicals. Thus, this insight into the chemical and thermal modification of biochar added composites would allow effective engineering to optimise their properties while simultaneously utilising wastes. - Highlights: • Waste derived biochars were used to make polymer based biocomposites. • Composites were characterised by NMR, ESR, DSC, XRD, TEM etc. • Biochar increased the thermal conductivity of composites. • Biochar did not disrupt the crystal structure of polypropylene. • NMR revealed aromatic nature of biochar in composites.

  19. Modification of tapioca starch by non-chemical route using jet atmospheric argon plasma.

    Science.gov (United States)

    Wongsagonsup, Rungtiwa; Deeyai, Panakamol; Chaiwat, Weerawut; Horrungsiwat, Sawanee; Leejariensuk, Kesini; Suphantharika, Manop; Fuongfuchat, Asira; Dangtip, Somsak

    2014-02-15

    Non-chemical modification of tapioca starch was investigated using jet atmospheric argon plasma treatment. Two forms of starch slurry, i.e. granular starch (G) and cooked starch (C), were jet-treated by argon plasma generated by supplying input power of 50 W (denoted as G50 and C50 samples) and 100 W (denoted as G100 and C100 samples) for 5 min. Physical, rheological, and structural characteristics of the modified starch were investigated. The G50 and C100 samples had lower paste clarity but higher thermal stability and performed stronger gels (G50 only) compared to their control counterparts. On the other hand, the analyzed properties of the G100 and C50 samples showed the opposite trend. FTIR and (1)H NMR results revealed that the relative areas of COC and OH peaks were changed after the treatment. Cross-linking reaction seemed to predominantly take place for the G50 and C100 samples, whereas depolymerization predominated for the G100 and C50 samples.

  20. Properties of acid polysaccharides and their chemical modification; Sansei tato no seijo to kagaku shushoku

    Energy Technology Data Exchange (ETDEWEB)

    Kogamo, A. [Kitasato Univ., Tokyo (Japan)

    1997-03-25

    Polysaccharides are in presence throughout the kingdoms of animals, vegetables, and microbes, participating in biotic activities. It has been disclosed of late that they are closely related to biotic functions, and complex saccharides, such as glycosaminoglycan (CAG), which constitute the sugar chain are attracting attention above all. This report centers on CAG and discusses the properties of acid polysaccharides, their chemical modification, and applications. CAG in organisms combines with proteins such as collagen for the formation of connective tissues, and also combines in quantities in covalent bond with proteins that constitute thin and long high-molecular cores for the formation of gigantic molecules called proteoglycan. It is an acid sugar chain in which uronic acid and amino sugar having amino groups intertwine each other. The basic reactions to be utilized for the production of highly active saccharides on the basis of this structure are the lowering of molecular weight and sulfation. Activity against HIV (Human Immunodeficiency Virus) is observed in marine alga saccharide carageenan, and studies are under way for variously modifying it for development into medicine. 6 refs., 6 figs.

  1. Chemical modification of an alpha 3-fucosyltransferase; definition of amino acid residues essential for enzyme activity.

    Science.gov (United States)

    Britten, C J; Bird, M I

    1997-02-11

    The biosynthesis of the carbohydrate antigen sialyl Lewis X (sLe(x)) is dependent on the activity of an alpha 3-fucosyltransferase (EC 2.4.1.152, GDP-fucose:Gal beta (1-4)GlcNAc-R alpha (1-3)fucosyltransferase). This enzyme catalyses the transfer of fucose from GDP-beta-fucose to the 3-OH of N-acetylglucosamine present in lactosamine acceptors. In this report, we have investigated the amino acids essential for the activity of a recombinant alpha 3-fucosyltransferase (FucT-VI) through chemical modification of the enzyme with group-selective reagents. FucT-VI activity was found to be particularly sensitive to the histidine-selective reagent diethylpyrocarbonate and the cysteine reagent N-ethylmaleimide, with IC50 values of less than 200 microM. Reagents selective for arginine and lysine had no effect on enzyme activity. The inclusion of GDP-beta-fucose during preincubation with NEM reduces the rate of inactivation whereas inclusion of an acceptor saccharide for the enzyme, Gal beta (1-4)GlcNAc, had no effect. No protective effect with either GDP-beta-fucose or Gal beta (1-4)GlcNAc was observed on treatment of the enzyme with diethylpyrocarbonate. These data suggest that in addition to an NEM-reactive cysteine in, or adjacent to, the substrate-binding site of the enzyme, FucT-VI possesses histidine residue(s) that are essential for enzyme activity.

  2. Diverse functionalization of Aurora-A kinase at specified surface and buried sites by native chemical modification.

    Directory of Open Access Journals (Sweden)

    Fiona Rowan

    Full Text Available The ability to obtain a homogeneous sample of protein is invaluable when studying the effect of alterations such as post-translational modifications (PTMs. Selective functionalization of a protein to investigate the effect of PTMs on its structure or activity can be achieved by chemical modification of cysteine residues. We demonstrate here that one such technique, which involves conversion of cysteine to dehydroalanine followed by thiol nucleophile addition, is suitable for the site-specific installation of a wide range of chemical mimics of PTMs, including acetylated and dimethylated lysine, and other unnatural amino acids. These reactions, optimized for the clinically relevant kinase Aurora-A, readily proceed to completion as revealed by intact protein mass spectrometry. Moreover, these reactions proceed under non-denaturing conditions, which is desirable when working with large protein substrates. We have determined reactivity trends for a diverse range of thiol nucleophile addition reactions at two separate sites on Aurora-A, and we also highlight limitations when using thiol nucleophiles that contain basic functional groups. We show that chemical modification of cysteine residues is possible not only on a flexible surface-exposed loop, but also within a deep active site pocket at the conserved DFG motif, which reveals the potential use of this method in exploring enzyme function through modification of catalytic site residues.

  3. Chemical and plasma surface modification of lignocellulose coconut waste for the preparation of advanced biobased composite materials.

    Science.gov (United States)

    Kocaman, Suheyla; Karaman, Mustafa; Gursoy, Mehmet; Ahmetli, Gulnare

    2017-03-01

    In this study, surface-modified grinded coconut waste (CW) particles were used as bio-fillers to prepare polymeric composite materials with enhanced properties. Epoxy resin modified with acrylated and epoxidized soybean oil (AESO) was used as the polymer matrix. Two different strategies, namely chemical treatment and plasma enhanced chemical vapor deposition (PECVD) were utilized to modify the surface of CW particles for using them as compatible bio-fillers in composite preparation. Chemical modification involved the treatment of CW particles in a highly alkali NaOH solution, while PECVD modification involved coating of a thin film of hydrophobic poly(hexafluorobutyl acrylate) (PHFBA) around individual CW particle surfaces. Untreated and surface-modified CW particles were used in 10-50wt% for preparation of epoxy composites. FTIR analysis was performed to study the effect of modification on the structures of particles and as-prepared composites. The composite morphologies were investigated by XRD and SE. TGA test was conducted to study the thermal behavior of the composites. Also, the effects of CW particle surface modification on the mechanical and water sorption properties of epoxy resin composites were investigated in detail. It was observed that PECVD-treated CW particles had much more positive effects on the thermal, mechanical, wettability and flammability properties of composites. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. A GREEN CHEMICAL APPROACH OF CORN STARCH MODIFICATION FOR INNOVATIVE SOLUTIONS IN ADSORPTION OF POLYCYCLIC AROMATIC HYDROCARBONS

    Directory of Open Access Journals (Sweden)

    ANA MARIA ROŞU

    2017-03-01

    Full Text Available The aim of research is to achieve chemical modifications of corn starch. Therefore, the present study focuses on its chemical modifications, in order to increase its aqueous solubility and to ameliorate its adsorption properties for one hydrophobic pollutant, belonging to Polycyclic Aromatic Hydrocarbons (PAHs, benzo[a]pyrene (BaP, as a model. Starch chemical modifications are realized by alkylation reactions using ether (propylene oxide or ester (succinic anhydride alkyl agents. Starches obtained are characterized by 1H NMR technique in order to verify the alkylation procedure. Water solubility of the obtained product was determined and its capacity to adsorb the considered model pollutant was studied. According to the registered results, starch modification with succinic anhydride conducts to an aqueous solubility of 34.00 g·L-1, significantly increased in comparison with the solubility of native corn starch which is insoluble in water at room temperature. With this modified starch, promising results for BaP aqueous solubilisation were obtained.

  5. Antidiarrheal activity of hexane extract of Citrus limon peel in an experimental animal model.

    Science.gov (United States)

    Adeniyi, Olasupo Stephen; Omale, James; Omeje, Samuel Chukwuma; Edino, Victoria Ojimaojo

    2017-03-01

    Acute diarrhea is one of the major illnesses that cause death in children, despite clinical interventions and the use of oral rehydration therapy. Thus, there is need to discover other effective, affordable and accessible treatments for this disease. Therefore, this study was carried out to investigate the effects of hexane extract of Citrus limon peel (HECLP) on castor oil-induced diarrhea in rats. Diarrhea was induced in male albino Wistar rats weighing 100-150 g. The antidiarrheal activity of HECLP at different oral dosages (5, 10 and 20 mg/kg) was investigated by counting the number of wet fecal pellets. Animals were further treated with propranolol, prazosin, nifedipine and atropine to assess the effects of receptor blockers on the activities of the extract. The effects of HECLP on castor oil-induced enteropooling and the intestinal transit time of activated charcoal were also evaluated. Each of the 3 doses of C. limon significantly reduced (P limon peel possesses antidiarrheal effects through antisecretory and antimotility mechanisms that act through the β adrenergic system.

  6. Toxic effects of Citrus aurantium and C. limon essential oils on Spodoptera frugiperda (Lepidoptera: Noctuidae).

    Science.gov (United States)

    Villafañe, Emilio; Tolosa, Diego; Bardón, Alicia; Neske, Adriana

    2011-09-01

    Citrus aurantium and C. limon were selected in the search for natural plant insecticides. The essential oils of C. aurantium and C. limon and ethanol extracts of the seeds, pulp, albedo, and peel of C. aurantium were incorporated into the larval diet of the lepidopteran pest Spodoptera frugiperda. Larval and pupal mortality were quantified and adult malformation was observed. C aurantium essential oil had antifeedant action and the mixture of albedo ethanol extract and C aurantium essential oil had toxic effects on S. frugiperda larvae at early stages, when they had not yet produced major damage to the crop. Our results indicated that a mixture of ethanol extract of albedo and C. aurantium essential oil (250 microg of extract mix per g of diet) deterred feeding by 46% and had the highest larval mortality (100%) of the materials tested. The peel extract (250 microg per g of diet) produced an increment in growth rate and diet consumption. However, 40% of the larval and 45% of the pupal populations died after 96 h of treatment. The blend of essential oil and C. aurantium albedo ethanol extract showed the lowest consumption and a poor nutrient conversion into biomass. Finally, the presence of D-limonene and nootkatone in the peel ethanol extract, and C. limon and C. aurantium essential oils, may be the cause of the response in the feeding behavior and toxic effects found on S. frugiperda.

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

    Science.gov (United States)

    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.

  8. Purification and side chain selective chemical modifications of glutamate dehydrogenase from Bacillus subtilis natto.

    Science.gov (United States)

    Ni, Yinyun; Wang, Jiale; Qian, Bingjun; Song, Guangyan; Yao, Xiaomin; Zhang, Jian-hua

    2014-04-01

    Glutamate dehydrogenase (GDH) from Bacillus subtilis natto was purified to apparent homogeneity by ammonium sulfate precipitation, ion-exchange chromatography, size exclusion chromatography, and hydroxyapatite (HA) affinity chromatography. The GDH was purified 34-fold, with a yield of 41 % of total activity and a specific activity of 34.29 U/mg proteins. The molecular weight (Mr) of was measured at 47 kDa with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and 264 kDa with high-performance liquid chromatography (HPLC). The optimum pH and temperature for the deammoniation reaction were measured to be 7.5 and 30 °C, respectively. The active-site amino acid residues of GDH were investigated by chemical modification. The compounds 2,4,6-trinitrobenzenesulfonic acid (TNBS), phenylglyoxal (PG), and phenylmethanesulfonyl fluoride (PMSF) were used to modify lysine, arginine, and serine active site residues, respectively. After treatment with modifying reagents at concentrations of 1 mM, GDH activity fell to 10.7 % with TNBS, 83.3 % with PG, and 12.8 % with PMSF. However, with substrate protection, there was almost no loss in GDH activity following treatment with any modifying reagent. The kinetic parameters K m and V max were determined in each case. K m values for native GDH, 50 % TNBS-inactivated GDH, and 50 % PMSF-inactivated GDH were 0.037, 0.104, and 0.017 mM, respectively. V max values were 0.048, 0.022, and 0.031 mM/s, respectively. These results suggest that the active site contains one or more lysine residues that play a role in substrate binding and one or more serine residues that may maintain the enzyme conformation. However, arginine residues played less of a role in the activity of GDH.

  9. A spectrocolorimetric and chemical study on color modification of heat-treated wood during artificial weathering

    Science.gov (United States)

    Huang, Xianai; Kocaefe, Duygu; Kocaefe, Yasar; Boluk, Yaman; Pichette, Andre

    2012-05-01

    Effect of artificial weathering on the wood surface color modifications of three North American species (jack pine, aspen, and birch) heat-treated under different temperatures was studied by spectrocolorimetric colormeter (datacolor, CHECK TM). Data was analyzed using the reflectance spectra (400-700 nm) as well as the CIE-L*a*b* system and ΔE. Kubelka-Munk (K-M) spectra of samples were recorded as a function of artificial weathering time to obtain the absorption maxima of the chromophore woods formed during artificial weathering. The results were compared with those of the respective untreated (Kiln-dried) species. Analysis of chemical components shows that the lignin percent of jack pine, aspen, and birch increased after heat treatment (28.66-35.9%, 20.27-26.41%, and 19.04-22.71% respectively) which might be due to smaller influence of heat treatment on lignin content than hemicelluloses. This improves the resistance of heat-treated wood to photo-degradation. This is also supported by the smaller change observed in K-M spectra and total color parameters in CIE-L*a*b* system of heat-treated wood samples compared to those of untreated wood when weathered for72 h. However, the lignin percent of heat-treated woods reduce to maximum 2.5% after artificial weathering of 1512 h. This suggests that the weathering degrades most lignin matrix; consequently, both the colors of heat-treated woods and untreated woods are lighter and very similar after a long period of artificial weathering.

  10. A high-throughput UPLC method for the characterization of chemical modifications in monoclonal antibody molecules.

    Science.gov (United States)

    Stackhouse, Nicole; Miller, Amanda K; Gadgil, Himanshu S

    2011-12-01

    Development of high-throughput release and characterization assays is critical for the effective support of the rapidly growing biologics pipeline for biotherapeutics. Clipping of polypeptide chains is commonly monitored during process optimization, formulation development, and stability studies. A reduced capillary electrophoresis-sodium dodecyl sulfate (rCE -SDS) method is often used as a purity release assay for monitoring clips in monoclonal antibodies (mAbs); however, it has a cycle time of approximately 40 min, which is not suited for high-throughput screening. Additionally, the characterization of clips and variants from electropherograms is not straightforward and takes significant time. Reduced reversed-phase (RP) chromatography has been a popular assay for the characterization and identification of clips and variants because it can be directly coupled with online mass spectrometric analysis. However, the high-column temperature and low pH required for RP assays can induce on-column cleavage and therefore skew the results. To minimize on-column degradation, we have developed a high-throughput method with a significantly shorter cycle time of 5 min. The short cycle time was achieved using an ultra-high-pressure liquid chromatography (UPLC) system with a 1.7 μm phenyl column. This UPLC method allowed quantitation of hinge clipping in an IgG1 molecule and acid induced aspartic acid/proline (D/P) clip in an IgG2 molecule. The results from the UPLC method were comparable to those obtained with rCE-SDS. Additionally, the phenyl column offered partial resolution of oxidation and other chemical modifications, making this technique an attractive assay for high-throughput process characterization and formulation screens. Copyright © 2011 Wiley-Liss, Inc.

  11. An Alternative Way towards Preparation of Hydrophobically Associating Polyacrylamide:Chemical Post-Modification

    Institute of Scientific and Technical Information of China (English)

    FENG Yu-jun

    2004-01-01

    Hydrophobically associating polyacrylamides (HAPAMs) are derivatives from polyacrylamides by incorporating a small amount of hydrophobic moieties along the water-soluble mainchain. They are now becoming a class of promising candidates as thickeners or rheology modifiers in the formulations where rheology is necessary to be regulated, such as tertiary oil recovery, drilling fluids, hydraulic fracturing and coatings. Due to association of hydrophobes in nano-domains, their aqueous solutions exhibit very interesting rheological properties and better stability against salts than the unmodified precursor, polyacrylamide.Generally, there are two synthetic routes to introduce hydrophobic portion onto water-soluble polymer chains; i.e., direct copolymerization of hydrophobic and hydrophilic monomers, and post-polymerization functionalization[1]. In the case of HAPAM polymers, a commonly accepted method is micellar copolymerization in which an appropriate surfactant is employed to solubilize both monomers. However, it is widely reported[2] that the obtained polymers via micellar polymerization are characterized by: (i) blocky distribution of the hydrophobes; (ii) compositional inhomogeneity and (iii) strong dependence of solution properties on the block length.In this work, the alternative process, i.e., chemical post-modification, is employed to synthesize HAPAM polymers by direct N-alkylation of parent polyacrylamide (Figure 1) in dimethyl sulfoxide[3,4].PAM HAPAMFig. 1 Schematic route to prepare HAPAM by direct N-alkylation of PAMIt is found that the final incorporation of hydrophobic groups is in good agreement with the feed ratio[4], in contrast with that from micellar copolymerization which always brings about composition drift. Furthermore, unique rheological responses to shear rate, salt, temperature are also evidenced[5].

  12. A method for the chemical modification of polychlorinated biphenyls for improved affinity towards noble metal surfaces

    DEFF Research Database (Denmark)

    2015-01-01

    The present application discloses a method for the modification and analysis of a field sample suspected of containing contaminant(s) like polychlorinated biphenyls (PCBs). The invention also relates to a corresponding kit for the modification of samples suspected of containing such contaminant(s)....

  13. Novel method for chemical modification and patterning of the SU-8 photoresist

    DEFF Research Database (Denmark)

    Blagoi, Gabriela; Keller, Stephan Urs; Boisen, Anja;

    2007-01-01

    the wetting behaviour of SU-8. The resolution limit of the AQ photopatterning method was 20 μm when using an uncollimated light source. AQ modification followed by a reaction with amino groups of Alexa-647 cadaverine and a Biotin-amino derivative proved possible modification and patterning of polymeric...

  14. Novel method for chemical modification and patterning of the SU-8 photoresist

    DEFF Research Database (Denmark)

    Blagoi, Gabriela; Keller, Stephan Urs; Boisen, Anja

    2007-01-01

    the wetting behaviour of SU-8. The resolution limit of the AQ photopatterning method was 20 μm when using an uncollimated light source. AQ modification followed by a reaction with amino groups of Alexa-647 cadaverine and a Biotin-amino derivative proved possible modification and patterning of polymeric...

  15. Comparison of heat and mass transfer of different microwave-assisted extraction methods of essential oil from Citrus limon (Lisbon variety) peel.

    Science.gov (United States)

    Golmakani, Mohammad-Taghi; Moayyedi, Mahsa

    2015-11-01

    Dried and fresh peels of Citrus limon were subjected to microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME), respectively. A comparison was made between MAHD and SFME with the conventional hydrodistillation (HD) method in terms of extraction kinetic, chemical composition, and antioxidant activity. Higher yield results from higher extraction rates by microwaves and could be due to a synergy of two transfer phenomena: mass and heat acting in the same way. Gas chromatography/mass spectrometry (GC/MS) analysis did not indicate any noticeable differences between the constituents of essential oils obtained by MAHD and SFME, in comparison with HD. Antioxidant analysis of the extracted essential oils indicated that microwave irradiation did not have adverse effects on the radical scavenging activity of the extracted essential oils. The results of this study suggest that MAHD and SFME can be termed as green technologies because of their less energy requirements per ml of essential oil extraction.

  16. Modification of foxtail millet starch by combining physical, chemical and enzymatic methods.

    Science.gov (United States)

    Dey, Ashim; Sit, Nandan

    2017-02-01

    Modification of foxtail millet starch was carried out by heat moisture treatment (HT), acid hydrolysis (AH), enzymatic treatment (EH), Ultrasound treatment (UT) and their combinations. A total of 15 modified starches were prepared by combining the various methods and properties were compared with native starch. The solubilities of the starches modified by HT were found to decrease whereas for other single modifications it increased. It also increased with number of modifications applied. The swelling power decreased for all the modified starches and a decrease in swelling power was observed with increase in number of modifications. Freeze-thaw stability improved for starches modified by single physical modifications i.e. HT and UT. Decrease in viscosities was observed for the modified starches and was particularly affected by AH. The pasting temperature was found to increase for those modified starches where HT was carried out. The modified starches gave softer gels. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Effect of modification temperature on starch oxidation and its physico-chemical properties

    OpenAIRE

    Sławomir Pietrzyk; Teresa Fortuna; Elżbieta Pabiś

    2012-01-01

    Corn starch was oxidised by hydrogen peroxide at temperatures 20, 30, 40 and 50°C. The oxidised starches were examined for the content of carboxyl groups, carbonyl groups, amylose and for water binding capacity and water solubility. Susceptibility to retrogradation and pasting characteristics were also determined. The results indicate that the effectiveness of oxidation process increased with increased temperature of modification. Temperature of modification influenced content of amylose ...

  18. Structure-based chemical modification strategy for enzyme replacement treatment of phenylketonuria.

    Science.gov (United States)

    Wang, Lin; Gamez, Alejandra; Sarkissian, Christineh N; Straub, Mary; Patch, Marianne G; Han, Gye Won; Striepeke, Steve; Fitzpatrick, Paul; Scriver, Charles R; Stevens, Raymond C

    2005-01-01

    Structure-based protein engineering coupled with chemical modifications (e.g., pegylation) is a powerful combination to significantly improve the development of proteins as therapeutic agents. As a test case, phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) was selected for enzyme replacement therapy in phenylketonuria [C.R. Scriver, S. Kaufman, Hyperphenylalaninemia:phenylalanine Hydroxylase Deficiency. The Metabolic and Molecular Bases of Inherited Disease, McGraw-Hill, New York, 2001, Chapter 77], an inherited metabolic disorder (OMIM 261600) causing mental retardation due to deficiency of the enzyme l-phenylalanine hydroxylase (EC 1.14.16.1). Previous in vivo studies of recombinant PAL demonstrated a lowering of blood l-phenylalanine levels; yet, the metabolic effect was not sustained due to protein degradation and immunogenicity [C.N. Sarkissian, Z. Shao, F. Blain, R. Peevers, H. Su, R. Heft, T.M. Chang, C.R. Scriver, A different approach to treatment of phenylketonuria:phenylalanine degradation with recombinant phenylalanine ammonia lyase, Proc. Natl. Acad. Sci. USA 96 (1999) 2339; J.A. Hoskins, G. Jack, H.E. Wade, R.J. Peiris, E.C. Wright, D.J. Starr, J. Stern, Enzymatic control of phenylalanine intake in phenylketonuria, Lancet 1 (1980) 392; C.M. Ambrus, S. Anthone, C. Horvath, K. Kalghatgi, A.S. Lele, G. Eapen, J.L. Ambrus, A.J. Ryan, P. Li, Extracorporeal enzyme reactors for depletion of phenylalanine in phenylketonuria, Ann. Intern. Med. 106 (1987) 531]. Here, we report the 1.6A three-dimensional structure of Rhodosporidium toruloides PAL, structure-based molecular engineering, pegylation of PAL, as well as in vitro and in vivo PKU mouse model studies on pegylated PAL formulations. Our results show that pegylation of R. toruloides PAL leads to promising therapeutic efficacy after subcutaneous injection by enhancing the in vivo activity, lowering plasma phenylalanine, and leading to reduced immunogenicity. The three-dimensional structure of PAL provides a

  19. Effects of chemical modification on in vitro rate and extent of food starch digestion: an attempt to discover a slowly digested starch.

    Science.gov (United States)

    Wolf, B W; Bauer, L L; Fahey, G C

    1999-10-01

    Differences in glycemic and insulinemic responses to dietary starch are directly related to the rate of starch digestion. Chemical modification of starch may allow for the production of a slowly digested starch that could be used for the treatment of certain medical modalities. An in vitro method was utilized to evaluate the effects of chemical modification on the rate and extent of raw and cooked starch digestion. The extent of starch digestion was significantly reduced by dextrinization, etherification, and oxidation. However, the rate of starch digestion was not significantly affected by chemical modification. For most modified starches, as the degree of modification increased, the extent of digestion decreased, suggesting an increase in the amount of resistant starch. The results of this study suggest that chemically modified starch has a metabolizable energy value of <16.7 kJ/g. Chemically modified starch ingredients may serve as a good source of resistant starch in human and animal diets.

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

    Science.gov (United States)

    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.

  1. Structural, chemical surface and transport modifications of regenerated cellulose dense membranes due to low-dose {gamma}-radiation

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez, M.I. [Grupo de Caracterizacion Electrocinetica en Membranas e Interfases, Departamento de Fisica Aplicada I, Facultad de Ciencias, Universidad de Malaga, E-29071 Malaga (Spain); Heredia-Guerrero, J.A., E-mail: jose.alejandro@icmse.csic.es [Instituto de Ciencia de Materiales de Sevilla, Centro Mixto CSIC-Universidad de Sevilla, Avda, Americo Vespuccio 49, 41092 Sevilla (Spain); Galan, P. [Grupo de Caracterizacion Electrocinetica en Membranas e Interfases, Departamento de Fisica Aplicada I, Facultad de Ciencias, Universidad de Malaga, E-29071 Malaga (Spain); Benitez, J.J. [Instituto de Ciencia de Materiales de Sevilla, Centro Mixto CSIC-Universidad de Sevilla, Avda, Americo Vespuccio 49, 41092 Sevilla (Spain); Benavente, J. [Grupo de Caracterizacion Electrocinetica en Membranas e Interfases, Departamento de Fisica Aplicada I, Facultad de Ciencias, Universidad de Malaga, E-29071 Malaga (Spain)

    2011-04-15

    Research highlights: {yields} Low dose {gamma}-radiation causes slight structural, chemical and morphological changes on regenerated cellulose films. {yields} Induced structural changes increase the fragility of irradiated films. {yields} Structural modifications reduce ion permeability of films. - Abstract: Modifications caused in commercial dense regenerated cellulose (RC) flat membranes by low-dose {gamma}-irradiation (average photons energy of 1.23 MeV) are studied. Slight structural, chemical and morphological surface changes due to irradiation in three films with different RC content were determined by ATR-FTIR, XRD, XPS and AFM. Also, the alteration of their mechanical elasticity has been studied. Modification of membrane performance was determined from solute diffusion coefficient and effective membrane fixed charge concentration obtained from NaCl diffusion measurements. Induced structural changes defining new and effective fracture propagation directions are considered to be responsible for the increase of fragility of irradiated RC membranes. The same structural changes are proposed to explain the reduction of the membrane ion permeability through a mechanism involving either ion pathways elongation and/or blocking.

  2. Effect of modification temperature on starch oxidation and its physico-chemical properties

    Directory of Open Access Journals (Sweden)

    Sławomir Pietrzyk

    2012-12-01

    Full Text Available Corn starch was oxidised by hydrogen peroxide at temperatures 20, 30, 40 and 50°C. The oxidised starches were examined for the content of carboxyl groups, carbonyl groups, amylose and for water binding capacity and water solubility. Susceptibility to retrogradation and pasting characteristics were also determined. The results indicate that the effectiveness of oxidation process increased with increased temperature of modification. Temperature of modification influenced content of amylose in oxidised starch. Water binding capacity at 60 and 80°C and water solubility at 80°C increased with increased temperature of modification. Starch oxidised at 50°C had the lowest susceptibility to retrogradation and had the highest rheological stability.  

  3. Antioxidant and Antinociceptive Effects of Citrus limon Essential Oil in Mice

    Directory of Open Access Journals (Sweden)

    Lidianne Mayra Lopes Campêlo

    2011-01-01

    Full Text Available The antioxidant and antinociceptive activities of Citrus limon essential oil (EO were assessed in mice or in vitro tests. EO possesses a strong antioxidant potential according to the scavenging assays. Moreover, it presented scavenger activity against all in vitro tests. Orally, EO (50, 100, and 150 mg/kg significantly reduced the number of writhes, and, at highest doses, it reduced the number of paw licks. Whereas naloxone antagonized the antinociceptive action of EO (highest doses, this suggested, at least, the participation of the opioid system. Further studies currently in progress will enable us to understand the action mechanisms of EO.

  4. Development of a Pliocene mixed-carbonate siliciclastic reef (Limon, Costa Rica)

    Science.gov (United States)

    Bauch, Thorsten; Reijmer, John J. G.; McNeill, Donald F.; Schäfer, Priska

    2011-07-01

    The Miocene to Pleistocene Limon Group of Costa Rica is a mixed carbonate-siliciclastic succession that formed in association with the emergence of the Central American Isthmus. Our study focuses on a lower Late Pliocene reef unit, the newly excavated Contact Cut, which is located at the contact between the siliciclastic sediments of the Rio Banano Formation and the mixed reefal and coral bearing deposits and siliciclastic sediments of the Quebrada Chocolate Formation. The siliciclastic sediments were deposited in a thick, deltaic setting sourced by erosion of the Cordillera de Talamanca. Deposits of the Limon Group preserve a sequence of progressively shallowing, near-shore sediments that were exposed by uplift during the early to middle Pleistocene. The Contact Cut outcrop shows the first reef sequence in the stratigraphic sequence and thus illustrates the reestablishment of Caribbean coral reef predominance in the Neogene. It shows extensive reef growth during a rise in sea level and a slight progradation during the succeeding sea-level highstand. Three stages of reef evolution are recognized based on faunal diversity. The Contact Cut reef complex is comparable to the time equivalent reef of the Las Islas roadcut, situated west of Limon, which shows a rapid burial of the corals by siliciclastics. Both reefs document a distinct facies diversification during the final stages of the closing of the Central American Seaway. The reefs developed in an environment stressed by siliciclastic input, which ultimately caused a decrease in coral diversity and abundance followed by a temporary demise of the reefs. The biotic composition of the patch reefs that occurred during the sea-level rise, Las Islas and Contact Cut, did not differ from the reefs that developed during the final highstand in sea level, the reefs of the overlying Moin formation (Limon Group). Differences in the position on the shelf relative to the source of the siliciclastics might have been the cause for

  5. Enhanced Metal Contacts to Carbon Nanotube Networks through Chemical and Physical Modification

    Science.gov (United States)

    Cox, Nathanael David

    Carbon nanotubes (CNTs) are an emerging class of nano-structured carbon materials which are currently being studied for applications which would benefit from their desirable electrical and mechanical properties. Potential benefits such as improved current density, flexure tolerance, weight savings, and even radiation tolerance have led to their implementation into numerous devices and structures, many of which are slated for use in space environments. The role of CNTs can be quite diverse, with varied CNT electronic-types and morphologies dictated by the specific application. Despite numerous CNT types and morphologies employed by these technologies, a common link between nearly all of these devices and structures is metal contact to CNTs, where the metal components often provide the link between the carbon nanotubes and the external system. In this work, a variety of CNT-metal systems were characterized in terms of metal morphology analysis and CNT-metal electrical and mechanical interactions, in response to chemical and structural modifications. A large portion of the work additionally focuses on ion irradiation environments. A diverse number of experiments related to CNT-metal interactions will be discussed. For instance, electrochemical interactions between ion-irradiated single-wall CNTs (SWCNTs) and metal salt solutions were utilized to selectively deposit Au nanoparticles (Au-NPs) onto the SWCNTs. A direct correlation was established between defect density and Au-NP areal density, resulting in a method for rapid spatial profiling of ion-irradiation induced defects in SWCNTs. The effect of ion irradiation on the CNT-metal interface was also investigated and it was found that the contact resistance of Ag-SWCNT structures increases, while the specific contact resistance decreases. The increase in overall contact resistance was attributed to increased series resistance in the system due to damage of the bulk SWCNT films, while the decrease in specific contact

  6. The chemical modification of  -chymotrypsin with both hydrophobic and hydrophilic compounds stabilizes the enzyme against denaturation in water-organic media

    National Research Council Canada - National Science Library

    Vinogradov, A.A; Kudryashova, E.V; Grinberg, V.Ya; Grinberg, N.V; Burova, T.V; Levashov, A.V

    2001-01-01

    We considered [alpha]-chymotrypsin (CT) in homogeneous water-organic media as a model system to examine the influence of enzyme chemical modification with hydrophilic and hydrophobic substances on its stability, activity and structure...

  7. Comparison of some effects of modification of a polylactide surface layer by chemical, plasma, and laser methods

    Energy Technology Data Exchange (ETDEWEB)

    Moraczewski, Krzysztof, E-mail: kmm@ukw.edu.pl [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Rytlewski, Piotr [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Malinowski, Rafał [Institute for Engineering of Polymer Materials and Dyes, ul. M. Skłodowskiej–Curie 55, 87-100 Toruń (Poland); Żenkiewicz, Marian [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland)

    2015-08-15

    Highlights: • We modified polylactide surface layer with chemical, plasma or laser methods. • We tested selected properties and surface structure of modified samples. • We stated that the plasma treatment appears to be the most beneficial. - Abstract: The article presents the results of studies and comparison of selected properties of the modified PLA surface layer. The modification was carried out with three methods. In the chemical method, a 0.25 M solution of sodium hydroxide in water and ethanol was utilized. In the plasma method, a 50 W generator was used, which produced plasma in the air atmosphere under reduced pressure. In the laser method, a pulsed ArF excimer laser with fluency of 60 mJ/cm{sup 2} was applied. Polylactide samples were examined by using the following techniques: scanning electron microscopy (SEM), atomic force microscopy (AFM), goniometry and X-ray photoelectron spectroscopy (XPS). Images of surfaces of the modified samples were recorded, contact angles were measured, and surface free energy was calculated. Qualitative and quantitative analyses of chemical composition of the PLA surface layer were performed as well. Based on the survey it was found that the best modification results are obtained using the plasma method.

  8. In vitro/in vivo effect of Citrus limon (L. Burm. f.) juice on blood parameters, coagulation and anticoagulation factors in rabbits.

    Science.gov (United States)

    Riaz, Azra; Khan, Rafeeq Alam; Mirza, Talat; Mustansir, Tazeen; Ahmed, Mansoor

    2014-07-01

    The genus Citrus of the family Rutaceae includes many species e.g. Citrus indica, Citrus aurantifolia and Citrus limon, among which Citrus limon L. Burm. f. has been reported to have highest antimicrobial activity. It is used as antidote against certain venom, due to its platelet inhibitory effect and also reported to have hypocholesterolemic effect. However its anticoagulant and thrombolytic effect were not been investigated, hence a prospective in-vitro/in-vivo study was designed to determine the effect of Citrus limon on blood parameters, coagulation and anticoagulation factors. In-vitro tests revealed highly significant increase in thrombin time and activated partial thromboplastin time by Citrus limon, whereas fibrinogen concentration was significantly reduced in comparison to control, however prothrombin time was not affected significantly. In-vivo testing of Citrus limon was done at three different doses i.e. 0.2ml/kg, 0.4ml/kg and 0.6ml/kg in healthy rabbits. Significant changes were observed in hematological parameters such as erythrocytes, hemoglobin and mean corpuscular hemoglobin concentration. Bleeding time and thrombin time was significantly prolonged and there was increase in protein C and thrombin antithrombin complex levels. These results may be due to inactivation of thrombin because it significantly decreases fibrinogen concentration and inhibit platelet aggregation. Citrus limon showed maximal anticoagulant effect at 0.4ml/kg, which suggest that Citrus limon possesses an anti-thrombin component and could prevent thrombosis playing a cardio protective role.

  9. Chemical modification of nanocellulose with canola oil fatty acid methyl ester

    Science.gov (United States)

    Liqing Wei; Umesh P. Agarwal; Kolby C. Hirth; Laurent M. Matuana; Ronald C. Sabo; Nicole M. Stark

    2017-01-01

    Cellulose nanocrystals (CNCs), produced from dissolving wood pulp, were chemically functionalized by transesterification with canola oil fatty acid methyl ester (CME). CME performs as both the reaction reagent and solvent. Transesterified CNC (CNCFE) was characterized for their chemical structure, morphology, crystalline structure, thermal stability, and hydrophobicity...

  10. Surface etching, chemical modification and characterization of silicon nitride and silicon oxide - Selective functionalization of Si

    NARCIS (Netherlands)

    Liu, Li Hong; Michalak, David J.; Chopra, Tatiana P.; Pujari, Sidharam P.; Zuilhof, Han

    2016-01-01

    The ability to selectively chemically functionalize silicon nitride (Si3N4) or silicon dioxide (SiO2) surfaces after cleaning would open interesting technological applications. In order to achieve this goal, the chemical composition of surfaces needs to be careful

  11. Bentonite chemical modification for use in industrial effluents; Modificacao quimica de bentonita para uso em efluentes industriais

    Energy Technology Data Exchange (ETDEWEB)

    Laranjeira, E.; Pinto, M.R.O.; Rodrigues, D.P.; Costa, B.P.; Guimaraes, P.L.F. [Universidade Estadual da Paraiba (DQ/CCT/UEPB), Campina Grande (Brazil). CCT. Dept. de Quimica

    2010-07-01

    The present work aims at synthesizing organoclays using a layered silicate of regional importance, bentonite clay, for the treatment of industrial effluents. The choice of clay to be organophilized was based on cation exchange capacity (CEC). Bentonite with higher CTC was called AN 35 (92 meq/100 g), and therefore was the one that suffered the chemical modification with salt cetyl trimethyl ammonium Cetremide, provided by Vetec.The unmodified and modified clays were characterized by FTIR and XDR. The data obtained through the characterizations confirmed the acquisition of bentonite organoclay thus suggesting its subsequent application in the treatment of industrial effluents. (author)

  12. Integration of plasma-assisted surface chemical modification, soft lithography, and protein surface activation for single-cell patterning

    Science.gov (United States)

    Cheng, Q.; Komvopoulos, K.

    2010-07-01

    Surface patterning for single-cell culture was accomplished by combining plasma-assisted surface chemical modification, soft lithography, and protein-induced surface activation. Hydrophilic patterns were produced on Parylene C films deposited on glass substrates by oxygen plasma treatment through the windows of polydimethylsiloxane shadow masks. After incubation first with Pluronic F108 solution and then serum medium overnight, surface seeding with mesenchymal stem cells in serum medium resulted in single-cell patterning. The present method provides a means of surface patterning with direct implications in single-cell culture.

  13. Modification of the surface electronic and chemical properties of Pt(111) by subsurface 3d transition metals

    DEFF Research Database (Denmark)

    Kitchin, J. R.; Nørskov, Jens Kehlet; Barteau, M. A.;

    2004-01-01

    The modification of the electronic and chemical properties of Pt(111) surfaces by subsurface 3d transition metals was studied using density-functional theory. In each case investigated, the Pt surface d-band was broadened and lowered in energy by interactions with the subsurface 3d metals......, resulting in weaker dissociative adsorption energies of hydrogen and oxygen on these surfaces. The magnitude of the decrease in adsorption energy was largest for the early 3d transition metals and smallest for the late 3d transition metals. In some cases, dissociative adsorption was calculated...

  14. Carbon dots (C-dots) from cow manure with impressive subcellular selectivity tuned by simple chemical modification.

    Science.gov (United States)

    D'Angelis do E S Barbosa, Cintya; Corrêa, José R; Medeiros, Gisele A; Barreto, Gabrielle; Magalhães, Kelly G; de Oliveira, Aline L; Spencer, John; Rodrigues, Marcelo O; Neto, Brenno A D

    2015-03-23

    Improved cellular selectivity for nucleoli staining was achieved by simple chemical modification of carbon dots (C-dots) synthesized from waste carbon sources such as cow manure (or from glucose). The C-dots were characterized and functionalized (amine-passivated) with ethylenediamine, affording amide bonds that resulted in bright green fluorescence. The new modified C-dots were successfully applied as selective live-cell fluorescence imaging probes with impressive subcellular selectivity and the ability to selectively stain nucleoli in breast cancer cell lineages (MCF-7). The C-dots were also tested in four other cellular models and showed the same cellular selection in live-cell imaging experiments.

  15. Chemical modifications of graphene and their influence on properties of polyurethane composites: a review

    Science.gov (United States)

    Włodarczyk, D.; Urban, M.; Strankowski, M.

    2016-10-01

    Polyurethane composites are materials of great interest nowadays due to their wide range of available forms and applications in industry. Controlling and achieving unique properties via matrix modifications and addition of various specific nanofillers seems be one of the key elements to success. The purpose of this work is to briefly present some examples of graphene nanoderivatives, their syntheses, properties and influence on polyurethane matrix after application. Structural, mechanical and electrical properties of graphene nanofillers were analyzed before and after implementation into polymer matrices. Additionally properties of obtained composites were considered in the context of shape memory. The first chapter presents methods of synthesizing carbon nanofillers and some structure investigations via x-ray Diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy. The second part discusses influence of graphene modifications on polymer structure and changes in thermomechanical properties via stress-strain tests and Thermogravimetry (TG).

  16. Surface Modification of α-Fe Metal Particles by Chemical Surface Coating

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The structure of α-Fe metal magnetic recording particles coated with silane coupling agents have been studied by TEM, FT-IR, EXAFS, Mossbauer. The results show that a close, uniform, firm and ultra thin layer, which is beneficial to the magnetic and chemical stability, has been formed by the cross-linked chemical bond Si-O-Si. And the organic molecule has chemically bonded to the particle surface, which has greatly affected the surface Fe atom electronic structure. Furthermore, the covalent bond between metal particle surface and organic molecule has obvious effect on the near edge structure of the surface Fe atoms.

  17. Engineering a Chemical Switch into the Light-driven Proton Pump Proteorhodopsin by Cysteine Mutagenesis and Thiol Modification.

    Science.gov (United States)

    Harder, Daniel; Hirschi, Stephan; Ucurum, Zöhre; Goers, Roland; Meier, Wolfgang; Müller, Daniel J; Fotiadis, Dimitrios

    2016-07-25

    For applications in synthetic biology, for example, the bottom-up assembly of biomolecular nanofactories, modules of specific and controllable functionalities are essential. Of fundamental importance in such systems are energizing modules, which are able to establish an electrochemical gradient across a vesicular membrane as an energy source for powering other modules. Light-driven proton pumps like proteorhodopsin (PR) are excellent candidates for efficient energy conversion. We have extended the versatility of PR by implementing an on/off switch based on reversible chemical modification of a site-specifically introduced cysteine residue. The position of this cysteine residue in PR was identified by structure-based cysteine mutagenesis combined with a proton-pumping assay using E. coli cells overexpressing PR and PR proteoliposomes. The identified PR mutant represents the first light-driven proton pump that can be chemically switched on/off depending on the requirements of the molecular system.

  18. Differential effects of defined chemical modifications on antigenic and pharmacological activities of scorpion alpha and beta toxins.

    Science.gov (United States)

    el Ayeb, M; Darbon, H; Bahraoui, E M; Vargas, O; Rochat, H

    1986-03-03

    Specific chemical modifications of scorpion alpha and beta toxins have been used to study the involvement of particular residues in both the pharmacological and the antigenic sites of these toxins. Modification by 1,2-cyclohexanedione of arginine-27 of a beta toxin, Centruroides suffusus suffusus toxin II, drastically decrease the antigenic activity without any influence on the pharmacological activity. Conversely, modification by the same reagent of arginine-2 of an alpha toxin, Androctonus australis Hector toxin III, led to a 100-times less pharmacologically potent derivative and did not induce a significant loss of antigenic activity. Excision of the N-terminal pentapeptide of another alpha toxin, Buthus occitanus mardochei toxin III, by pepsin digestion led to a non-toxic derivative retaining full antigenic activity. Thus, the N-terminal part of the conserved hydrophobic surface of the toxin is highly implicated in the pharmacological activity, whereas the region of arginine-27, located in the alpha helix situated on the back surface, opposite the conserved hydrophobic region, is fully implicated in the antigenic activity and is far from the pharmacological site. These results are good arguments in favor of the idea that in scorpion toxins the surfaces implicated in the pharmacological and the antigenic activities do not overlap. Since the antigenic sites are present in highly variable sequence the development of an efficient polyvalent serotherapy is questionable.

  19. Chemical modification and pH dependence of kinetic parameters to identify functional groups in a glucosyltransferase from Strep. Mutans

    Energy Technology Data Exchange (ETDEWEB)

    Bell, J.E.; Leone, A.; Bell, E.T.

    1986-05-01

    A glucosyltransferase, forming a predominantly al-6 linked glucan, was partially purified from the culture filtrate of S. mutans GS-5. The kinetic properties of the enzyme, assessed using the transfer of /sup 14/C glucose from sucrose into total glucan, were studied at pH values from pH 3.5 to 6.5. From the dependence of km on pH, a group with pKa = 5.5 must be protonated to maximize substrate binding. From plots of V/sub max/ vs pH two groups, with pKa's of 4.5 and 5.5 were indicated. The results suggest the involvement of either two carboxyl groups (one protonated, one unprotonated in the native enzyme) or a carboxyl group (unprotonated) and some other protonated group such as histidine, cysteine. Chemical modification studies showed that Diethylyrocarbonate (histidine specific) had no effect on enzyme activity while modification with p-phydroxy-mercuribenzoate or iodoacetic acid (sulfhydryl reactive) and carbodimide reagents (carboxyl specific) resulted in almost complete inactivation. Activity loss was dependent upon time of incubation and reagent concentration. The disaccharide lylose, (shown to be an inhibitor of the enzyme with similar affinity to sucrose) offers no protection against modification by the sulfhydryl reactive reagents.

  20. Modification of Tau by 8-Nitroguanosine 3',5'-Cyclic Monophosphate (8-Nitro-cGMP): EFFECTS OF NITRIC OXIDE-LINKED CHEMICAL MODIFICATION ON TAU AGGREGATION.

    Science.gov (United States)

    Yoshitake, Jun; Soeda, Yoshiyuki; Ida, Tomoaki; Sumioka, Akio; Yoshikawa, Misato; Matsushita, Kenji; Akaike, Takaaki; Takashima, Akihiko

    2016-10-21

    Neurofibrillar tangles caused by intracellular hyperphosphorylated tau inclusion and extracellular amyloid β peptide deposition are hallmarks of Alzheimer's disease. Tau contains one or two cysteine residues in three or four repeats of the microtubule binding region following alternative splicing of exon 10, and formation of intermolecular cysteine disulfide bonds accelerates tau aggregation. 8-Nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP) acts as a novel second messenger of nitric oxide (NO) by covalently binding cGMP to cysteine residues by electrophilic properties, a process termed protein S-guanylation. Here we studied S-guanylation of tau and its effects on tau aggregation. 8-Nitro-cGMP exposure induced S-guanylation of tau both in vitro and in tau-overexpressed HEK293T cells. S-guanylated tau inhibited heparin-induced tau aggregation in a thioflavin T assay. Atomic force microscopy observations indicated that S-guanylated tau could not form tau granules and fibrils. Further biochemical analyses showed that S-guanylated tau was inhibited at the step of tau oligomer formation. In P301L tau-expressing Neuro2A cells, 8-nitro-cGMP treatment significantly reduced the amount of sarcosyl-insoluble tau. NO-linked chemical modification on cysteine residues of tau could block tau aggregation, and therefore, increasing 8-nitro-cGMP levels in the brain could become a potential therapeutic strategy for Alzheimer's disease. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  1. Monoterpene biosynthesis in lemon (Citrus limon) cDNA isolation and functional analysis of four monoterpene synthases

    NARCIS (Netherlands)

    Lücker, J.; Tamer, El M.K.; Schwab, W.; Verstappen, F.W.A.; Plas, van der L.H.W.; Bouwmeester, H.J.; Verhoeven, H.A.

    2002-01-01

    Citrus limon possesses a high content and large variety of monoterpenoids, especially in the glands of the fruit flavedo. The genes responsible for the production of these monoterpenes have never been isolated. By applying a random sequencing approach to a cDNA library from mRNA isolated from the

  2. The effect of ethyl acetate fraction of Citrus limon peel on mesenchymal cell proliferation and polybacterial growth

    Directory of Open Access Journals (Sweden)

    Astrid Marinna

    2015-09-01

    Full Text Available Background: Oral diseases remain to be global health problem. The common therapy involved the use of modern medicines with their various side effects. Citrus limon are potentials as anti-inflammatory, anti-fungal, anti-oxidant, anti-viral and anti-bacterial. Purpose: The purpose of this study was to determine the effect of ethyl acetate fraction of citrus limon peel extract on human gingival mesenchymal cell proliferation and palm commensal polybacterial growth. Method: This study was experimental study with post test only control group design. Citrus limon peel extracted and partitioned in order to obtain ethyl acetate fraction of 3.125%, 2.75%, 2.375%, 2%, and 1.5625%. Toxicity test was performed after 24 hours using the MTT Assays. Cell viability was measured by optical density formazonand read by ELISA reader 620 nm. Results: All treatment groups showed less than 60% cell viability. The highest cell was 19.36 (1.5625% concentration and the lowest was 12.65 (3.125% concentration. The highest anti-bacterial inhibition value was 8.9125 mm (3.125% concentration and the lowest was 6.0625 mm (1.5625% concentration. Conclusion: The higher concentration of ethyl acetate fraction Citrus limon peel extract, the higher toxicity and inhibitory properties against commensal palm polybacteria.

  3. Monoterpene biosynthesis in lemon (Citrus limon) cDNA isolation and functional analysis of four monoterpene synthases

    NARCIS (Netherlands)

    Lücker, J.; El Tamer, M.K.; Schwab, W.; Verstappen, F.W.A.; Plas, van der L.H.W.; Bouwmeester, H.J.; Verhoeven, H.A.

    2002-01-01

    Citrus limon possesses a high content and large variety of monoterpenoids, especially in the glands of the fruit flavedo. The genes responsible for the production of these monoterpenes have never been isolated. By applying a random sequencing approach to a cDNA library from mRNA isolated from the pe

  4. Thermally reversible thermoset materials based on the chemical modification of alternating aliphatic polyketones

    NARCIS (Netherlands)

    Araya Hermosilla, Rodrigo Andrés

    2016-01-01

    This thesis focused on the synthesis and characterization of different kinds of reversible thermosets and thermoset nanocomposite materials by using alternating aliphatic polyketone (PK) as raw material. Fundamental knowledge was generated regarding the molecular design of new polymers via chemical

  5. MECHANICAL AND CHEMICAL MODIFICATION OF WOOD MATERIALS – COMPRESSED WOOD AND OXIDIZED CHARCOAL

    National Research Council Canada - National Science Library

    Vasily I. Patyakin; Uzum U. Sugaipov; Alexei R. Birman; Sergei M. Bazarov; Yuri N. Pilshikov; Andrei A. Spitsyn; Howard D. Mettee

    2008-01-01

    Mechanical compression and electrolyte infusion of wood, pyrolysis, and chemical activation of the resulting charcoals produced enhanced abilities to adsorb lead ion and benzene from model polluted water solutions. Iodine number (F...

  6. Controllable end shape modification of ZnO nano-arrays/rods by a simple wet chemical etching technique

    Science.gov (United States)

    Sun, Jingchang; Zhao, Ting; Ma, Zhangwei; Li, Ming; Chang, Cheng; Liang, Hongwei; Bian, Jiming; Li, Chengren

    2015-09-01

    The well-aligned ZnO nano-arrays/rods synthesized by a chemical bath deposition method on a highly conductive Si substrate were chemically etched in an ammonia chloride aqueous solution. An obvious end shape modification of ZnO nano-arrays/rods was realized in this report. The hexagonal frustum end of ZnO nano-arrays/rods changed into a pyramid and the diameter of ZnO nano-arrays/rods decreased gradually with the increasing etching time. The evolution mechanism of the wet etching process was discussed based on a proposed evolution model. Photoluminescence measurements indicated that the near band edge emissions of ZnO nano-arrays/rods increased greatly after wet etching. The controllable end shape modification of ZnO nano-arrays/rods on a highly conductive Si substrate by this simple wet etching technique will further explore the application of ZnO in field emission devices and 1D based nano-devices with various end shapes.

  7. S-(2-Succinyl)cysteine: a novel chemical modification of tissue proteins by a Krebs cycle intermediate.

    Science.gov (United States)

    Alderson, Nathan L; Wang, Yuping; Blatnik, Matthew; Frizzell, Norma; Walla, Michael D; Lyons, Timothy J; Alt, Nadja; Carson, James A; Nagai, Ryoji; Thorpe, Suzanne R; Baynes, John W

    2006-06-01

    S-(2-Succinyl)cysteine (2SC) has been identified as a chemical modification in plasma proteins, in the non-mercaptalbumin fraction of human plasma albumin, in human skin collagen, and in rat skeletal muscle proteins and urine. 2SC increases in human skin collagen with age and is increased in muscle protein of diabetic vs. control rats. The concentration of 2SC in skin collagen and muscle protein correlated strongly with that of the advanced glycation/lipoxidation end-product (AGE/ALE), N(epsilon)-(carboxymethyl)lysine (CML). 2SC is formed by a Michael addition reaction of cysteine sulfhydryl groups with fumarate at physiological pH. Fumarate, but not succinate, inactivates the sulfhydryl enzyme, glyceraldehyde-3-phosphate dehydrogenase in vitro, in concert with formation of 2SC. 2SC is the first example of spontaneous chemical modification of protein by a metabolic intermediate in the Krebs cycle. These observations identify fumarate as an endogenous electrophile and suggest a role for fumarate in regulation of metabolism.

  8. Comparison of some effects of modification of a polylactide surface layer by chemical, plasma, and laser methods

    Science.gov (United States)

    Moraczewski, Krzysztof; Rytlewski, Piotr; Malinowski, Rafał; Żenkiewicz, Marian

    2015-08-01

    The article presents the results of studies and comparison of selected properties of the modified PLA surface layer. The modification was carried out with three methods. In the chemical method, a 0.25 M solution of sodium hydroxide in water and ethanol was utilized. In the plasma method, a 50 W generator was used, which produced plasma in the air atmosphere under reduced pressure. In the laser method, a pulsed ArF excimer laser with fluency of 60 mJ/cm2 was applied. Polylactide samples were examined by using the following techniques: scanning electron microscopy (SEM), atomic force microscopy (AFM), goniometry and X-ray photoelectron spectroscopy (XPS). Images of surfaces of the modified samples were recorded, contact angles were measured, and surface free energy was calculated. Qualitative and quantitative analyses of chemical composition of the PLA surface layer were performed as well. Based on the survey it was found that the best modification results are obtained using the plasma method.

  9. Chemical modification of peanut conglutin reduces IgE reactivity but not T cell reactivity in peanut-allergic patients.

    Science.gov (United States)

    van Hoffen, E; van der Kleij, H P M; den Hartog Jager, C F; van Doorn, W A; Knol, E F; Opstelten, D-J; Koppelman, S J; Knulst, A C

    2014-12-01

    Specific immunotherapy for peanut allergy is associated with significant side-effects. Chemically modified allergens may provide a safer alternative. This study aimed to analyse the immunogenicity and allergenicity of modified peanut conglutin. Native peanut conglutin and two modifications thereof were generated (RA and RAGA). Conglutin-specific T cell lines from 11 peanut-allergic patients were analysed for proliferation and cytokine production. Sera from 14 patients were analysed for IgE/IgG1/IgG4 binding by immunoblot and ELISA. IgE reactivity was analysed by direct and indirect basophil activation test (BAT), in presence and absence of patient plasma or CD32-blocking antibodies. T cell proliferation to RA was unchanged, and proliferation to RAGA was reduced compared to native conglutin. Cytokine profiles remained unchanged. IgE, IgG1 and IgG4 binding to RA and RAGA was significantly reduced. In the direct BAT, the relative potency of modified conglutin was decreased in 67% and increased/similar in 33% of the patients. In the indirect BAT, RA and RAGA were 10-100 times less potent than native conglutin. Addition of plasma to the indirect BAT increased the relative potency of modified conglutin in patients with high peanut-specific IgG levels. This was mediated via blocking of the response to native conglutin, most likely by soluble IgG, and not via CD32. Chemical modification of peanut conglutin by RA retains immunogenicity and reduces allergenicity and may be a promising approach for development of a curative treatment for peanut allergy. In a subgroup of patients, where the reactivity of native conglutin is already partially blocked by IgG, the effect of the modification of conglutin is less pronounced. © 2014 John Wiley & Sons Ltd.

  10. QUANTUM-CHEMICAL MODIFICATIONS OF SURFACE:NEW METHODS FOR PROTECTING MATERIALS FROM CORROSION

    Institute of Scientific and Technical Information of China (English)

    R. T. Malkhasyan

    2001-01-01

    A new method of corrosion-resistant coating of technical iron is presented. Processingby vibrationally excited hydrogen molecules of the iron surface covered with oxide filmof a-Fe2O3 results in modification of surface by creating a film of amorphous ironon it. The presence of iron films with crystalline and amorphous phases, having thedifferent Fermi levels, leads tO formation of potential differences between them. Thispotential difference is opposite to the external electric field, resulting in decrease ofanode current and increase of corrosion resistance.

  11. The protective effect of Citrus limon essential oil on hepatotoxicity and nephrotoxicity induced by aspirin in rats.

    Science.gov (United States)

    Bouzenna, Hafsia; Dhibi, Sabah; Samout, Noura; Rjeibi, Ilhem; Talarmin, Hélène; Elfeki, Abdelfattah; Hfaiedh, Najla

    2016-10-01

    Citrus limon is a member of the large Rutaceae family characterized by its therapeutic proprieties and has been widely used in traditional medicine to treat various diseases. This study investigates the protective effect of Citrus limon essential oil against a high dose of aspirin-induced acute liver and kidney damage in female Wistar albino rats. Twenty-eight adult female Wistar rats were divided into 4 groups of 7 each: (1) a control group; (2) a group of rats which was kept untreated for 56days then treated with aspirin (A) (600mg/kg) for 4 days; (3) a group fed with essential oil of Citrus limon for 56days then (A) for 4 days; and (4) a group of rats receiving essential oil of Citrus limon for 56 days, then given NaCl for 4 days. Estimations of biochemical parameters in blood were determined. Lipid peroxidation levels (TBARS), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidas (GPx) activities in liver and kidney was determined. A histopathological study was done. Under our experimental conditions, aspirin induced an increase of serum biochemical parameters and it resulted in an oxidative stress in both liver and kidney. This was evidenced by significant increase in TBARS in liver and kidney by 108% and 55%, respectively, compared to control. On the other hand, a decrease in the activities of SOD by 78% and 53%, CAT by 53% and 78%, and GPx by 78% and 51% in liver and kidney, respectively. Administration of EOC to rats attenuated the induced an effect of the high dose of aspirin induced in the afore mentioned serum biochemical parameters. In conclusion, our data suggest that treatment with essential oil of Citrus limon prevented the liver and kidney damage induced by aspirin.

  12. Non-additive gene regulation in a citrus allotetraploid somatic hybrid between C. reticulata Blanco and C. limon (L.) Burm.

    Science.gov (United States)

    Bassene, J B; Froelicher, Y; Dubois, C; Ferrer, R M; Navarro, L; Ollitrault, P; Ancillo, G

    2010-09-01

    Polyploid plants often produce new phenotypes, exceeding the range of variability existing in the diploid gene pool. Several hundred citrus allotetraploid hybrids have been created by somatic hybridization. These genotypes are interesting models to study the immediate effects of allopolyploidization on the regulation of gene expression. Here, we report genome-wide gene expression analysis in fruit pulp of a Citrus interspecific somatic allotetraploid between C. reticulata cv 'Willowleaf mandarin'+C. limon cv 'Eureka lemon', using a Citrus 20K cDNA microarray. Around 4% transcriptome divergence was observed between the two parental species, and 212 and 160 genes were more highly expressed in C. reticulata and C. limon, respectively. Differential expression of certain genes was confirmed by quantitative real-time RT-PCR. A global downregulation of the allotetraploid hybrid transcriptome was observed, as compared with a theoretical mid parent, for the genes displaying interspecific expression divergence between C. reticulata and C. limon. The genes underexpressed in mandarin, as compared with lemon, were also systematically repressed in the allotetraploid. When genes were overexpressed in C. reticulata compared with C. limon, the distribution of allotetraploid gene expression was far more balanced. Cluster analysis on the basis of gene expression clearly indicated the hybrid was much closer to C. reticulata than to C. limon. These results suggest there is a global dominance of the mandarin transcriptome, in consistence with our previous studies on aromatic compounds and proteomics. Interspecific differentiation of gene expression and non-additive gene regulation involved various biological pathways and different cellular components.

  13. Potencial antioxidante de extratos de sementes de limão (Citrus limon Antioxidant potential of lemon seed extracts (Citrus limon

    Directory of Open Access Journals (Sweden)

    Débora Maria Moreno Luzia

    2010-06-01

    Full Text Available O presente trabalho teve como principais objetivos avaliar o comportamento do óleo de soja acrescido de extratos de sementes de limão (Citrus limon, em diferentes concentrações, por meio da estabilidade oxidativa e medir a atividade antioxidante através do método do radical livre DPPH e compostos fenólicos totais. A concentração de 2.400 mg.kg-1 para o extrato de sementes de limão, variedade galego, foi a que conferiu melhor estabilidade oxidativa ao óleo de soja. As atividades antioxidantes máximas e os valores da concentração de extrato natural suficientes para obter 50% do efeito máximo, estimado em 100% (EC50, determinados pelo DPPH para o extrato e ácido gálico foram 70,58%, 69,94 μg.mL-1 e 75,07%, 64,73 μg.mL-1, respectivamente. A concentração de compostos fenólicos totais, determinada pelo método de Folin-Ciocalteu foi de 76 mg.g-1. Foi possível concluir que o extrato de sementes de limão galego possui ação antioxidante natural, podendo ser aplicado em alimentos.The present study aimed at evaluating the behavior of the soybean oil with the addition of lemon seed extracts (Citrus limon, in different concentrations, through oxidative stability and also at measuring the antioxidant activity using the DPPH free radical method and total phenolic compounds. The concentration of 2,400 mg.kg-1 for the lemon seed extract, galego variety, was the one that provided the soybean oil with the best oxidative stability. The maximum antioxidant activities and the concentration values of the natural extract sufficient to obtain 50% of maximum effect, estimated at 100% (EC50, determined by DPPH for the extract and gallic acid were 70.58%, 69.94 μg.mL-1 and 75.07%, 64.73 μg.mL-1, respectively. The concentration of total phenolic compounds, determined by the Folin-Ciocalteu method, was of 76 mg.g-1. Thus, it can be said that the lemon seed extract, galego, presents natural antioxidant action demonstrating potential to be used in

  14. Chemoproteomics Reveals Chemical Diversity and Dynamics of 4-Oxo-2-nonenal Modifications in Cells.

    Science.gov (United States)

    Sun, Rui; Fu, Ling; Liu, Ke-Ke; Tian, Cai-Ping; Yang, Yong; Tallman, Keri A; Porter, Ned A; Liebler, Daniel C; Yang, Jing

    2017-08-16

    4-Oxo-2-nonenal (ONE) derived from lipid peroxidation modifies nucleophiles and transduces redox signaling by its reactions with proteins. However, the molecular interactions between ONE and complex proteomes and their dynamics in situ remain largely unknown. Here we describe a quantitative chemoproteomic analysis of protein adduction by ONE in cells, in which the cellular target profile of ONE is mimicked by its alkynyl surrogate. The analyses reveal four types of ONE-derived modifications in cells, including ketoamide and Schiff-base adducts to lysine, Michael adducts to cysteine, and a novel pyrrole adducts to cysteine. ONE-derived adducts co-localize and crosstalk with many histone marks and redox sensitive sites. All four types of modifications derived from ONE can be reversed site-specifically in cells. Taken together, our study provides much-needed mechanistic insights into the cellular signaling and potential toxicities associated with this important lipid derived electrophile. Copyright © 2017, The American Society for Biochemistry and Molecular Biology.

  15. Electrochemical impedance spectroscopy for graphene surface modification and protein translocation through the chemically modified graphene nanopore

    Science.gov (United States)

    Tiwari, Purushottam; Shan, Yuping; Wang, Xuewen; Darici, Yesim; He, Jin

    2014-03-01

    The multilayer graphene surface has been modified using mercaptohexadecanoic acid (MHA) and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-750] (DPPE-PEG750). The surface modifications are evaluated using electrochemical impedance spectroscopy (EIS). EIS measurements show the better graphene surface passivation with DPPE-PEG750 than with MHA. After modification with ferritin, the MHA modified surface shows greater charge transfer resistance (Rct) change than DPPE-PEG750 modified surface. Based on these results the translocations of ferritin through modified graphene nanopore with diameter 5-20 nm are studied. The translocation is more successful through DPPE-PEG750 modified graphene nanopore. This concludes that that the attachment of ferritin to DPPE-PEG750 modified graphene nanopore is not significant compared to MHA modified pore for the ferritin translocation hindrance. These results nicely correlate with the EIS data for respective Rct change of ferritin modified surfaces. P. Tiwari would like to thank FIU School of Integrated Science & Humanity, College Arts & Sciences for the research assistantship.

  16. Effect of mechanical activation on structure changes and reactivity in further chemical modification of lignin.

    Science.gov (United States)

    Zhao, Xiaohong; Zhang, Yanjuan; Hu, Huayu; Huang, Zuqiang; Yang, Mei; Chen, Dong; Huang, Kai; Huang, Aimin; Qin, Xingzhen; Feng, Zhenfei

    2016-10-01

    Lignin was treated by mechanical activation (MA) in a customized stirring ball mill, and the structure and reactivity in further esterification were studied. The chemical structure and morphology of MA-treated lignin and the esterified products were analyzed by chemical analysis combined with UV/vis spectrometer, FTIR,NMR, SEM and particle size analyzer. The results showed that MA contributed to the increase of aliphatic hydroxyl, phenolic hydroxyl, carbonyl and carboxyl groups but the decrease of methoxyl groups. Moreover, MA led to the decrease of particle size and the increase of specific surface area and roughness of surface in lignin. The reactivity of lignin was enhanced significantly for the increase of hydroxyl content and the improvement of mass transfer in chemical reaction caused by the changes of molecular structure and morphological structure. The process of MA is green and simple, and is an effective method for enhancing the reactivity of lignin. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Absolute vacuum ultraviolet flux in inductively coupled plasmas and chemical modifications of 193 nm photoresist

    Science.gov (United States)

    Titus, M. J.; Nest, D.; Graves, D. B.

    2009-04-01

    Vacuum ultraviolet (VUV) photons in plasma processing systems are known to alter surface chemistry and may damage gate dielectrics and photoresist. We characterize absolute VUV fluxes to surfaces exposed in an inductively coupled argon plasma, 1-50 mTorr, 25-400 W, using a calibrated VUV spectrometer. We also demonstrate an alternative method to estimate VUV fluence in an inductively coupled plasma (ICP) reactor using a chemical dosimeter-type monitor. We illustrate the technique with argon ICP and xenon lamp exposure experiments, comparing direct VUV measurements with measured chemical changes in 193 nm photoresist-covered Si wafers following VUV exposure.

  18. Investigations of chemical modifications of amino-terminated organic films on silicon substrates and controlled protein immobilization.

    Science.gov (United States)

    Kim, Joonyeong; Cho, Joungmo; Seidler, Paul M; Kurland, Nicholas E; Yadavalli, Vamsi K

    2010-02-16

    Fourier transform infrared spectroscopy by grazing-angle attenuated total reflection (FTIR-GATR), ellipsometry, atomic force microscopy (AFM), UV-visible spectroscopy, and fluorescence microscopy were employed to investigate chemical modifications of amino-terminated organic thin films on silicon substrates, protein immobilization, and the biological activity and hydrolytic stability of immobilized proteins. Amino-terminated organic films were prepared on silicon wafers by self-assembling 3-aminopropyltriethoxysilane (APTES) in anhydrous toluene. Surface amino groups were derivatized into three different linkers: N-hydroxysuccinimide (NHS) ester, hydrazide, and maleimide ester groups. UV-visible absorption measurements and fluorescence microscopy revealed that more than 40% of surface amino groups were chemically modified. Protein immobilization was carried out on modified APTES films containing these linkers via coupling with primary amines (-NH(2)) in intact monoclonal rabbit immunoglobulin G (IgG), the aldehyde (-CHO) of an oxidized carbohydrate residue in IgG, or the sulfhydryl (-SH) of fragmented half-IgG, respectively. FTIR spectra contain vibrational signatures of these functional groups present in modified APTES films and immobilized IgGs. Changes in the APTES film thickness after chemical modifications and protein immobilization were also observed by ellipsometric measurements. The biological activity and long-term hydrolytic stability of immobilized IgGs on modified APTES films were estimated by fluorescence measurements of an adsorbed antigen, fluorescein isothiocyanate (FITC)-labeled goat anti-rabbit IgG (FITC-Ab). Our results indicate that the FITC-Ab binding capacity of half-IgG immobilized via maleimide groups is greater than that of the oxidized IgG and the intact IgG immobilized via hydrazide and NHS ester groups, respectively. In addition, IgGs immobilized using all coupling chemistries were hydrolytically stable in phosphate-buffered saline (PBS).

  19. Chemical modification of bitumen heavy ends and their non-fuel uses

    Energy Technology Data Exchange (ETDEWEB)

    Moschopedis, S.E.; Speight, J.G.

    1976-01-01

    Bitumen asphaltenes undergo a variety of simple chemical conversions. For example, asphaltenes can be oxidized, sulfonated, sulfomethylated, halogenated, and phosphorylated. The net result is the introduction of functional entities into the asphaltene structure which confers interesting properties on the products for which a variety of uses are proposed.

  20. Specific physical and chemical properties of two modifications of poly(N-vinylcaprolcatam)

    Science.gov (United States)

    Chihacheva, I. P.; Timaeva, O. I.; Kuz'micheva, G. M.; Dorohov, A. V.; Lobanova, N. A.; Amarantov, S. V.; Podbel'skiy, V. V.; Serousov, V. E.; Sadovskaya, N. V.

    2016-05-01

    Two modifications of poly(N-vinylcaprolactam)—PVCL25 and PVCL40 (drying of a PVCL solution at 25 and 40°C, respectively)—as powdered films and their solutions were systematically investigated for the first time. Powders were studied by X-ray diffraction, IR spectroscopy, scanning electron microscopy, low-temperature krypton adsorption, and differential scanning calorimetry. Solutions were studied by smallangle X-ray scattering and dynamic light scattering. It was demonstrated that powders of PVCL25 and PVCL40 differ in the characteristics of the sub- and microstructure and in the water content and the solutions differ in the particle size. The relationships between the characteristics of the systems in the solid and liquid state and between the hydrodynamic diameter of PVCL particles in solution and their coagulation time were found.

  1. Chemical modification of TiO2 surfaces with methylsilanes and characterization by infrared absorption spectroscopy

    Science.gov (United States)

    Finklea, H. O.; Vithanage, R.

    1982-01-01

    Infrared absorption spectra of methylsilanes bonded to a TiO2 powder were obtained. The reacting silanes include Me sub (4-n)SiX sub n (n=1-4; X=Cl, OMe) and hexamethyldisilazane (HMDS). Reactions were performed on hydroxylated-but-anhydrous TiO2 surfaces in the gas phase. IR spectra confirm the presence of a bonded silane layer. Terminal surface OH groups are found to react more readily than bridging OH groups. By-products of the modification adsorp tenaciously to the surface. The various silanes show only small differences in their ability to sequester surface OH groups. Following hydrolysis in moist air, Si-OH groups are observed only for the tetrafunctional silanes.

  2. Laser assisted modification and chemical metallization of electron-beam deposited ceria thin films

    Energy Technology Data Exchange (ETDEWEB)

    Krumov, E., E-mail: emodk@clf.bas.bg [Central Laboratory of Photoprocesses ' Acad. Jordan Malinowski' , Bulgarian Academy of Sciences, Acad. Georgy Bonchev Str., bl. 109, 1113 Sofia (Bulgaria); Starbov, N.; Starbova, K. [Central Laboratory of Photoprocesses ' Acad. Jordan Malinowski' , Bulgarian Academy of Sciences, Acad. Georgy Bonchev Str., bl. 109, 1113 Sofia (Bulgaria); Perea, A.; Solis, J. [Instituto de Optica ' Daza de Valdes' , CSIC, 28006 Madrid (Spain)

    2009-11-15

    Excimer laser processing is applied for tailoring the surface morphology and phase composition of CeO{sub 2} ceramic thin films. E-beam evaporation technique is used to deposit samples on stainless steel and silicate glass substrates. The films are then irradiated with ArF* excimer laser pulses under different exposure conditions. Scanning electron microscopy, optical spectrophotometry, X-ray diffractometry and EDS microanalysis are used to characterize the non-irradiated and laser-processed films. Upon UV laser exposure there is large increase of the surface roughness that is accompanied by photo-darkening and ceria reduction. It is shown that the laser induced changes in the CeO{sub 2} films facilitate the deposition of metal nano-aggregates in a commercial copper electroless plating bath. The significance of laser modification as a novel approach for the production of CeO{sub 2} based thin film catalysts is discussed.

  3. Protein adsorption to graphene surfaces controlled by chemical modification of the substrate surfaces.

    Science.gov (United States)

    Kamiya, Yasutaka; Yamazaki, Kenji; Ogino, Toshio

    2014-10-01

    We have investigated effects of the support substrate surfaces on properties of the attached graphene flakes by observing protein adsorption to the graphene surfaces on SiO2/Si substrates that are modified with self-assembled monolayers to control their hydrophilicity. Using atomic force microscopy operated in aqueous environment, we found that high-density clusters of agglomerated avidin molecules form on the graphene flakes in the areas supported by a hydrophobic substrate surface, whereas very low density of large avidin clusters form at the edge of graphene flakes in the area supported by a hydrophilic surface. These results demonstrate that hydrophilicity of the support surface affects hydrophilicity of the graphene surface also in aqueous environment and that surface modification of the support substrate is a useful technique to control protein adsorption phenomena on graphene surfaces for realization of high sensitive graphene biosensors.

  4. Comparative temporal analysis of multiwalled carbon nanotube oxidation reactions: Evaluating chemical modifications on true nanotube surface

    Science.gov (United States)

    Pacheco, Flávia G.; Cotta, Alexandre A. C.; Gorgulho, Honória F.; Santos, Adelina P.; Macedo, Waldemar A. A.; Furtado, Clascídia A.

    2015-12-01

    The influence of extensive purification on oxidized multiwalled carbon nanotube surface composition was studied through the characterization and differentiation of the actual surface submitted to three oxidation methods: microwave-assisted acid oxidation, hydrogen peroxide reflux, and Fenton reaction. The oxidized samples were purified by a multi-step procedure including the sequential use of basic reflux and dispersion in dimethylformamide (DMF). The results showed a significant increase in the amount of oxidation debris with hydrogen peroxide and Fenton reaction times longer than 8 h and strong surface characteristic modification. With regard to sample purification, basic reflux led to a reduction in oxygenated group concentration of only 10% in the samples treated by acid oxidation. On the other hand, the subsequent use of DMF led to a further decrease in concentration of 39%, proving to be a more efficient method for the removal of oxidation debris.

  5. Differential tolerance of 3 self-rooted Citrus limon cultivars to NaCl stress.

    Science.gov (United States)

    Tsabarducas, V; Chatzistathis, T; Therios, I; Koukourikou-Petridou, M; Tananaki, C

    2015-12-01

    One-year-old self-rooted cuttings of three Citrus limon cultivars (Nouvel Athos, Lisbon, Maglini) were grown in 1 L black plastic bags, containing a mixture of sand: perlite (1:1), in order to investigate: i) if genotypic differences to salt stress existed, ii) if KNO3 can alleviate salinity stress, iii) the role of carbohydrates (such as the sugars fructose, glucose and sucrose) and proline as possible osmoregulators in C. limon osmoprotection, and iv) if genotypic differences to salt stress tolerance exist among the 3 studied cultivars. The experiment included 3 treatments: i) control (C), i.e. 25% modified Hoagland (No2) solution (MHS)-NaCl, ii) T1, 25% MHS+80 mM NaCl, iii) T2, 25% MHS+80 mM NaCl+5 mM KNO3. Plant growth was negatively affected by high NaCl (T1); the highest Cl and Na quantities have been absorbed by Lisbon, while the lowest ones by Maglini. Salt stress reduced macronutrient and Zn concentrations, as well as the total carbohydrate concentration, and increased peroxidase (POD) activity and chlorophyll fluorescence in the leaves of the 3 C. limon cultivars studied; five mM KNO3 application alleviated the harmful effect of salt stress on leaf total carbohydrate concentration and leaf N and K concentrations. Sucrose was dramatically reduced in all the three genotypes studied, while leaf fructose concentration was significantly increased in Nouvel Nouvel Nouvel Athos and Maglini under salt stress. Leaf proline concentration of Maglini was significantly decreased by the high NaCl concentration, while Nouvel Athos and Lisbon had high proline concentration in their leaves. In conclusion, from the significantly decreased levels of proline for Maglini, together with the greatest reduction of the ratio Fv/Fm and the least enhancement of POD activity-compared to the other two cultivars-it can be concluded that Maglini was more susceptible to salinity, and should not be preferred for cultivation under NaCl stress. Finally, rich KNO3 application

  6. Physical and chemical modification of the surface of Venus by windblown particles

    Science.gov (United States)

    Greeley, Ronald; Marshall, John R.; Pollack, James B.

    1987-01-01

    The results of simulations of the Venusian surface environment involving windblown grains are presented which show that significant chemical and physical changes may occur even in the slow-moving winds recorded on Venus. The edges of grains beome worn and shed comminuted debris, which collects on weathered surfaces and grains alike. The resulting transfer of material from loose grains to bedrock surfaces (and vice versa) could yield misleading results on rock composition; moreover, the generation of comminuted debris would enhance chemical reactions that could affect the composition of the atmosphere. The results are thus relevant in assessing rates of surface degradation, the evolution of small-scale surface features as seen in images returned from the Soviet Venera missions, and in the interpretation of compositional data for surface materials.

  7. Ionic Liquids and Cellulose: Dissolution, Chemical Modification and Preparation of New Cellulosic Materials

    Directory of Open Access Journals (Sweden)

    Mehmet Isik

    2014-07-01

    Full Text Available Due to its abundance and a wide range of beneficial physical and chemical properties, cellulose has become very popular in order to produce materials for various applications. This review summarizes the recent advances in the development of new cellulose materials and technologies using ionic liquids. Dissolution of cellulose in ionic liquids has been used to develop new processing technologies, cellulose functionalization methods and new cellulose materials including blends, composites, fibers and ion gels.

  8. Physico-chemical Conditions of the Surface Modification Process of Steels by Vanadium, Carbon and Nitrogen

    Directory of Open Access Journals (Sweden)

    N.A. Harchenko

    2014-11-01

    Full Text Available Theoretical calculations of the physical and chemical conditions of the nitrogenvanading process of steels are performed. The diagrams of the equilibrium composition of the reaction medium are presented. The phase composition of gaseous and condensed states of the systems, the optimum saturation temperature and mixture composition are derived. The optimal temperature range of nitrogenvanading of steels is established as follows: 1100-1300 K.

  9. Modifications of chemical functional groups of Pandanus amaryllifolius Roxb and its effect towards biosorption of heavy metals

    Science.gov (United States)

    Abdullah, Mohd. Zamri; Ismail, Siti Salwa

    2015-07-01

    The utilization of non-living biomass as an alternative biosorbent for heavy metal removal has gain a tremendous consideration through the years. Pandanus amaryllifolius Roxb or pandan leaves, which is widely used as food additives in the South East Asia region, has been selected for its viability in the said effort due to the presence of chemical functional groups on its cellular network that enables the sorption to occur. In order to elucidate the possible mechanisms participated during the heavy metal removal process, the biosorbent undergone a series of modification techniques to alter the chemical functional groups present on its constituent. From the outcome of the chemically-modified biosorbent being subjected to the contact with metal cations, nitrogen- and oxygen-containing groups present on the biosorbent are believed to be responsible for the metal uptake to occur through complexation mechanism. Modifying amine groups causes 14% reduction of Cu(II) uptake, whereas removing protein element increases the uptake to 26% as compared to the unmodified biosorbent. Also, scanning electron micrographs further suggested that the adsorption mechanism could perform in parallel, as attributed to the evidence of porous structure throughout the biosorbent fibrous nature.

  10. Modifications of chemical functional groups of Pandanus amaryllifolius Roxb and its effect towards biosorption of heavy metals

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah, Mohd Zamri, E-mail: zamriab@petronas.com.my; Ismail, Siti Salwa [Chemical Engineering Department, Universiti Teknologi PETRONAS, 31750 Bandar Seri Iskandar, Perak (Malaysia)

    2015-07-22

    The utilization of non-living biomass as an alternative biosorbent for heavy metal removal has gain a tremendous consideration through the years. Pandanus amaryllifolius Roxb or pandan leaves, which is widely used as food additives in the South East Asia region, has been selected for its viability in the said effort due to the presence of chemical functional groups on its cellular network that enables the sorption to occur. In order to elucidate the possible mechanisms participated during the heavy metal removal process, the biosorbent undergone a series of modification techniques to alter the chemical functional groups present on its constituent. From the outcome of the chemically-modified biosorbent being subjected to the contact with metal cations, nitrogen- and oxygen-containing groups present on the biosorbent are believed to be responsible for the metal uptake to occur through complexation mechanism. Modifying amine groups causes 14% reduction of Cu(II) uptake, whereas removing protein element increases the uptake to 26% as compared to the unmodified biosorbent. Also, scanning electron micrographs further suggested that the adsorption mechanism could perform in parallel, as attributed to the evidence of porous structure throughout the biosorbent fibrous nature.

  11. Chemical modification with phthalic anhydride and chitosan: Viable options for the stabilization of raw starch digesting amylase from Aspergillus carbonarius.

    Science.gov (United States)

    Nwagu, Tochukwu Nwamaka; Okolo, Bartholomew; Aoyagi, Hideki; Yoshida, Shigeki

    2017-06-01

    The raw starch digesting type of amylase (RSDA) presents greater opportunities for process efficiency at cheaper cost and shorter time compared to regular amylases. Chemical modification is a simple and rapid method toward their stabilization for a wider application. RSDA from Aspergillus carbonarius was modified with either phthalic anhydride (PA) or chitosan. Activity retention was 87.3% for PA-modified and 80.9% for chitosan-modified RSDA. Optimum pH shifted from 5 to 7 after PA-modification. Optimum temperature changed from 30°C (native) to 30-40°C and 60°C for PA-modified and chitosan-modified, respectively. Activation energy (kJmol(-1)) for hydrolysis was 13.5, 12.7, and 10.2 while the activation energy for thermal denaturation was 32.8, 80.3, 81.9 for free, PA-modified and chitosan-modified, respectively. The specificity constants (Vmax/Km) were 73.2 for PA-modified, 63.1 for chitosan-modified and 77.1 for native RSDA. The half-life (h) of the RSDA at 80°C was increased from 6.1 to 25.7 for the PA-modified and 138.6 for the chitosan derivative. Modification also led to increase in D value, activation enthalpy and Gibbs free energy of enzyme deactivation. Fluorescence spectra showed that center of spectral mass decreased for the PA-modified RSDA but increased for chitosan modified RSDA. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Determining copper and lead binding in Larrea tridentata through chemical modification and X-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Polette, L.; Gardea-Torresdey, J.L.; Chianelli, R. [Univ. of Texas, El Paso, TX (United States). Dept. of Chemistry; Pickering, I.J.; George, G.N. [Stanford Synchrotron Radiation Lab., Menlo Park, CA (United States)

    1997-12-31

    Metal contamination in soils has become a widespread problem. Emerging technologies, such as phytoremediation, may offer low cost cleanup methods. The authors have identified a desert plant, Larrea tridentata (creosote bush), which naturally grows and uptakes copper and lead from a contaminated area near a smelting operation. They determined, through chemical modification of carboxyl groups with methanol, that these functional groups may be responsible for a portion of copper(II) binding. In contrast, lead binding was minimally affected by modification of carboxyl groups. X-ray absorption spectroscopy studies conducted at Stanford Synchrotron Radiation Laboratory (SSRL) further support copper binding to oxygen-coordinated ligands and also imply that the binding is not solely due to phytochelatins. The EXAFS data indicate the presence of both Cu-O and Cu-S back scatters, no short Cu-Cu interactions, but with significant Cu-Cu back scattering at 3.7 {angstrom} (unlike phytochelatins with predominantly Cu-S coordination and short Cu-Cu interactions at 2.7 {angstrom}). Cu EXAFS of roots and leaves also vary depending on the level of heavy metal contamination in the environment from which the various creosote samples were obtained. In contrast, Pb XANES data of roots and leaves of creosote collected from different contaminated sites indicate no difference in valence states or ligand coordination.

  13. Sisal fibers: surface chemical modification using reagent obtained from a renewable source; characterization of hemicellulose and lignin as model study.

    Science.gov (United States)

    Megiatto, Jackson D; Hoareau, William; Gardrat, Christian; Frollini, Elisabete; Castellan, Alain

    2007-10-17

    Sisal fibers have one of the greatest potentials among other lignocellulosic fibers to reinforce polymer matrices in composites. Sisal fibers have been modified to improve their compatibility with phenolic polymer matrices using furfuryl alcohol (FA) and polyfurfuryl alcohols (PFA) that can be obtained from renewable sources. The modification corresponded first to oxidation with ClO 2, which reacts mainly with guaiacyl and syringyl units of lignin, generating o- and p-quinones and muconic derivatives, followed by reaction with FA or PFA. The FA and PFA modified fibers presented a thin similar layer, indicating the polymer character of the coating. The untreated and treated sisal fibers were characterized by (13)C CP-MAS NMR spectrometry, thermal analysis, and scanning electron microscopy. Furthermore, for a better understanding of the reactions involved in the FA and PFA modifications, the sisal lignin previously extracted was also submitted to those reactions and characterized. The characterization of isolated lignin and hemicellulose provides some information on the chemical structure of the main constitutive macrocomponents of sisal fibers, such information being scarce in the literature.

  14. Chemical modification of chitosan film via surface grafting of citric acid molecular to promote the biomineralization

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang, E-mail: liuyang@cczu.edu.cn [Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou 213164 (China); Engineering Research Center of Nano-Geo Materials of Ministry of Education, China University of Geosciences, Wuhan 430074 (China); School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); Shen, Xin; Zhou, Huan [Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou 213164 (China); Wang, Yingjun [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); Deng, Linhong, E-mail: dlh@cczu.edu.cn [Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou 213164 (China)

    2016-05-01

    Graphical abstract: - Highlights: • Chitosan film was modified by surface grafting of citric acid. • The modified film has good hydrophilicity and moisture-retaining capacity. • The citric acid grafting treatment significantly promote the biomineralization. • MC3T3-E1 osteoblasts research confirms the biocompatibility of the film. - Abstract: We develop a novel chitosan–citric acid film (abbreviated as CS–CA) suitable for biomedical applications in this study. In this CS–CA film, the citric acid, which is a harmless organic acid has been extensively investigated as a modifying agent on carbohydrate polymers, was cross-linked by 1-Ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) onto the surface of chitosan (CS) film. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirms the graft copolymerization of the modified chitosan film (CS–CA). Surface wettability, moisturizing performance, the capacity of mineralization in vitro and biocompatibility of the films were characterized. After modification, this CS–CA film has good hydrophilicity. It is very evident that the citric acid grafting treatment significantly promotes the biomineralization of the chitosan based substrates. Cell experiments show that the MC3T3-E1 osteoblasts can adhere and proliferate well on the surface of CS–CA film. This CS–CA film, which can be prepared in large quantities and at low cost, should have potential application in bone tissue engineering.

  15. Isocyanate-terminated Polyethers Toughened Epoxy Resin: Chemical Modification, Thermal Properties, and Mechanical Strength

    Institute of Scientific and Technical Information of China (English)

    CAI Haopeng; WANG Jun; WANG Xiang; XU Renxin

    2007-01-01

    The toughening of the diglycidyl ether of bisphenol A epoxy resin with isocyanateterminated polyethers (ITPE) was investigated. The progress of the reaction and the structural changes during modification process were studied using FTIR spectroscopy. The studies support the proposition that TDI (tolylene diisocyanate) acts as a coupling agent between the epoxy and polyethers, forming a urethane linkage with the former and the latter, respectively. Me THPA-cured ER/ITPs blends were characterized using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). It is indicated the glass transition temperature (Tg) of systems was lower than the Tg of pure epoxy resin and overfull ITPE separated from the modified epoxy resin and formed another phase at an ITPE-content of more than 10wt%. The thermal stability was decreased by the introduction of ITPE. The impact strength and the flexural strength of the cured modifiedepoxy increased with increasing the ITPE content and a maximum plateau value of about 24.03 kJ/m2 and 130.56 MPa was measured in 10wt% ITPE. From scanning electron microscopy (SEM) studies of the fractrue surfaces of ER/ITPE systems, the nature of the micromechanisms responsible for the increases in toughness of the systems was identified.

  16. Effect of chemical modification on carbon dioxide adsorption property of mesoporous silica.

    Science.gov (United States)

    Zhao, Yi; Shen, Yanmei; Bai, Lu

    2012-08-01

    Three adsorbents were prepared by different modification methods, which were grafting silica gel with (3-aminopropyl) trimethoxysilane, grafting silica gel with acrylamide polymer, and impregnating silica gel with acrylamide polymer, respectively. The characterization of materials was carried out by N(2) adsorption experiments, Fourier transform infrared spectroscopy, scanning electron microscopy, thermo-gravimetric analysis, and elemental analyses. The results showed that the amine group was successfully loaded on all three modified adsorbents; among that, the polymer-modified silica adsorbents had higher amine content and larger surface area than the aminopropyl-grafted silica adsorbent and displayed higher thermal stability than the other polymer-modified silica materials previously reported. The CO(2) adsorption/desorption experiments performed at 25°C by TGA-DSC method showed that the highest CO(2) adsorption capacity (0.98 mmol/g) was observed for the polymer-impregnated silica adsorbent. CO(2) adsorbed on all samples was completely desorbed by purging with inert gas at 60°C except for the aminopropyl-grafted silica material, which showed the highest enthalpy of CO(2) adsorption.

  17. Chemical and structural modifications of laser treated WTi surfaces at different ambient conditions

    Science.gov (United States)

    Petrović, S.; Peruško, D.; Milovanović, D.; Siketić, Z.; Jakšić, M.; Kovač, J.; Gaković, B.; Milosavljević, M.; Trtica, M.

    2011-11-01

    In this work we have studied the influence of laser modification on the composition and structure of tungsten titanium (WTi) thin films, deposited on n-type (100) silicon wafers. After deposition, the samples were multi-pulse laser irradiated in a nitrogen, oxygen, and helium ambient. The composition of the WTi/Si sample was determined by Elastic Recoil Detection Analysis (ERDA). Surface morphology was monitored by Atomic Force Microscopy (AFM). In the experiment, typical laser output parameters were: wavelength 1064 nm, pulse duration 150 ps, and laser pulse energy 30 mJ. Surface concentrations of W and Ti, as well as the concentration of gas components nitrogen and oxygen were determinated before and after the action of laser radiation in different ambient conditions. The contents of W and Ti decreased after irradiation due to adsorbed gases from the surrounding atmosphere. After surface irradiation in the inert ambient (He), the concentrations of the components were not significantly changed. In other cases, oxygen was the dominant component at the surface, probably due to the high affinity of thin film components. Also, the morphological changes occurred at the surface of WTi, as an increase in the surface roughness and formation of the granular structures are a result of laser-induced surface oxidation and recrystallization.

  18. Chemical modification of chitosan film via surface grafting of citric acid molecular to promote the biomineralization

    Science.gov (United States)

    Liu, Yang; Shen, Xin; Zhou, Huan; Wang, Yingjun; Deng, Linhong

    2016-05-01

    We develop a novel chitosan-citric acid film (abbreviated as CS-CA) suitable for biomedical applications in this study. In this CS-CA film, the citric acid, which is a harmless organic acid has been extensively investigated as a modifying agent on carbohydrate polymers, was cross-linked by 1-Ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) onto the surface of chitosan (CS) film. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirms the graft copolymerization of the modified chitosan film (CS-CA). Surface wettability, moisturizing performance, the capacity of mineralization in vitro and biocompatibility of the films were characterized. After modification, this CS-CA film has good hydrophilicity. It is very evident that the citric acid grafting treatment significantly promotes the biomineralization of the chitosan based substrates. Cell experiments show that the MC3T3-E1 osteoblasts can adhere and proliferate well on the surface of CS-CA film. This CS-CA film, which can be prepared in large quantities and at low cost, should have potential application in bone tissue engineering.

  19. Modifications in physico-chemical properties of 100 MeV oxygen ions irradiated polyimide Kapton-H polymer

    Science.gov (United States)

    Gupta, Sanjeev Kumar; Gupta, Rashi; Singh, Paramjit; Kumar, Vikas; Jaiswal, Manoj Kumar; Chakarvarti, S. K.; Kumar, Rajesh

    2017-09-01

    The optical, structural and chemical properties of polyimide Kapton-H polymer thin film samples were modified by irradiation with 100 MeV O7+ ions (in the fluence range of 1 × 1011 to 5 × 1012 ions/cm2) and the modifications of these properties were observed by UV-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy respectively. The band gap energy of the polymer decreased considerably with discrete increment of the ion fluence (different fluence for each sample) and effective change for the sample irradiated at a fluence of 5 × 1012 ions/cm2 was observed from that of pristine sample. The amorphous nature of the polymer was observed to be decreased with increase of ion fluence. The vibrations of Ctbnd C appeared at mid fluences but the stretching vibrations of Osbnd H bond disappeared at these fluences due to the high LET of the oxygen ions.

  20. Microstructural modification of nc-Si/SiO{sub x} films during plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X.W. [State Key Laboratory of Silicon Materials Science, Zhejiang University, Hangzhou 310027 (China)

    2005-07-01

    Nanocrystalline-silicon embedded silicon oxide films are prepared by plasma-enhanced chemical vapor deposition (PECVD) at 300 C without post-heat treatment. Measurements of XPS, IR, XRD, and HREM are performed. Microstructural modifications are found occurring throughout the film deposition. The silica network with a high oxide state is suggested to be formed directly under the abduction of the former deposited layer, rather than processing repeatedly from the original low-oxide state of silica. Nanocrystalline silicon particles with a size of 6-10 nm are embedded in the SiO{sub x} film matrix, indicating the potential application in Si-based optoelectronic integrity. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. New insights into the biological properties of Crocus sativus L.: chemical modifications, human monoamine oxidases inhibition and molecular modeling studies.

    Science.gov (United States)

    De Monte, Celeste; Carradori, Simone; Chimenti, Paola; Secci, Daniela; Mannina, Luisa; Alcaro, Francesca; Petzer, Anél; N'Da, Clarina I; Gidaro, Maria Concetta; Costa, Giosuè; Alcaro, Stefano; Petzer, Jacobus P

    2014-07-23

    Although there are clinical trials and in vivo studies in literature regarding the anxiolytic and antidepressant activities of the components of Crocus sativus L., their effects on the human monoamine oxidases (hMAO-A and hMAO-B), enzymes which are involved in mental disorders and neurodegenerative diseases, have not yet been investigated. We have thus examined the hMAO inhibitory activities of crocin and safranal (the most important active principles in saffron) and, subsequently, designed a series of safranal derivatives to evaluate which chemical modifications confer enhanced inhibition of the hMAO isoforms. Docking simulations were performed in order to identify key molecular recognitions of these inhibitors with both isoforms of hMAO. In this regard, different mechanisms of action were revealed. This study concludes that safranal and crocin represent useful leads for the discovery of novel hMAO inhibitors for the clinical management of psychiatric and neurodegenerative disorders.

  2. A Novel β-1, 4-N, 6-O-Diacetylmuramidase from Streptomyces griseus and its Chemical Modification

    Institute of Scientific and Technical Information of China (English)

    Chang Kui SUN; Yu Zhen ZHANG; Ming CHEN

    2006-01-01

    A novel lysozyme named β-1, 4-N, 6-O-diacetylmuramidase R2 was purified and characterized from Streptomyces griseus. The molecular weight of the enzyme was determined by MALDI-TOF-MS as 23.5 kDa. The N-terminal amino acid sequence was DTSGVQGIDVSHWQG. Chemical modification of β-1, 4-N, 6-O-diacetylmuramidase R2 indicated that sulfhydryl group and carbamidine of arginine residues are not essential for the activity of the enzyme, but lysine residues and imidazole of histidine residues are essential for the activity. The number of essential tryptophan and carboxyl groups was found that only one tryptophan residue and three carboxyl groups in the active site.

  3. Online RPLC-GC via TOTAD method to isolate (+)-methyl epijasmonate from lemon (Citrus limon Burm.).

    Science.gov (United States)

    del Mar Caja, Maria; Blanch, Gracia Patricia; Ruiz del Castillo, Maria Luisa

    2008-07-23

    Pure (+)-methyl epijasmonate was isolated from lemon ( Citrus limon Burm.) for the first time. To that aim, two commercial essential oils and one homemade extract were included in the present paper. First, a study on the appropriate chromatographic conditions to avoid the epimerization from methyl epijasmonate to the more stable methyl jasmonate was accomplished. The results obtained are discussed. The presence of (+)-methyl epijasmonate in the three samples studied was initially established through the direct injection into GC-MS. However, the overlapping of (+)-methyl epijasmonate with other matrix components made it necessary to employ a multidimensional technique. RPLC-GC analysis via through-oven transfer adsorption-desorption (TOTAD) provided the selectivity and sensitivity required, reflecting that the homemade lemon extract was an adequate natural source to obtain pure (+)-methyl epijasmonate by means of the collection of the corresponding RPLC fraction.

  4. Controlled chemical and morphological surface modifications via pulsed plasma polymerizations: Synthesis of ultrahydrophobic surfaces

    Science.gov (United States)

    Qiu, Haibo

    The RF plasma polymerization of saturated linear and cyclic perfluoroalkane monomers and vinyl acetic acid were studied in this dissertation. Film chemical compositions, deposition rates, surface wettabilities and morphologies were characterized as functions of various plasma processing conditions. Large progressive changes in chemical compositions with sequential variations in plasma duty cycle were demonstrated in polymerization of both perfluoroalkane and vinyl acetic acid monomers. As anticipated, polymer films obtained from the perfluorocarbon monomers exhibited a general trend towards more linear structures with decreasing plasma duty cycles. However, completely unexpectedly, ultrahydrophobic films were obtained from some of these monomers under restricted duty cycle and power input conditions. SEM and XPS characterizations revealed that a rough, fibrous-like surface morphology is responsible for this ultrahydrophobicity, as opposed to unusual chemical compositions. The growth of the fibrous surface is believed to arise from nucleation and hillock-like growth patterns on selectively activated sites of the growing polymer film. Surface mobility of plasma generated reactive species apparently plays an important role in the growth of the fibrous ultrahydrophobic surfaces, as shown by substrate temperature studies. Additionally, the present study revealed a number of interesting new observations of significant differences in the chemical compositions and deposition rates of polymer films obtained from the diverse range of perfluorocarbon monomers employed in this work. The ultrahydrophobic fluorocarbon films discovered in this investigation were evaluated for use in several biomaterial applications. The results obtained show excellent marine antifouling properties for these surfaces, as documented in ocean testing experiments. These surfaces have also been shown to be useful in controlling protein and peptide surface adsorptions, as well as in the inflammatory

  5. Studies on chemical modification of papain by 5-chlorosulfonyl-2-oxobenzimidazole as biotin model compound

    OpenAIRE

    石橋, 文秀; 森藤, 昌樹; 根来, 千晴; 園田, 章; 片山, あずさ; 武部, 靖

    2009-01-01

     5-chlorosulfonyl-2-oxobenzimidazole(1) was synthesized.  On adding 1 to the suspension of papain in acetonitrile containing formamide, 1 was introduced into the papain in a yield of 7%, suggesting that 1 modified papain chemically to give 2-oxobenzimidazolesulfonyl papain(OBI- papain).  Also, it was found in-terestingly that papain activity of OBI-papain was maintained and that SH group in the active center in the large cleft of papain was free.  Accordingly, It expects that OBI-papain might...

  6. Structural and light-emission modification in chemically-etched porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Navarro-Urrios, D.; Oton, C.J. [Departamento de Fisica Basica, University of La Laguna, Avda. Astrofisico Fco. Sanchez, La Laguna (Spain); INFM and Dipartimento di Fisica, University of Trento, Via Sommarive 14, Povo, Trento (Italy); Perez-Padron, C.; Lorenzo, E.; Capuj, N.E. [Departamento de Fisica Basica, University of La Laguna, Avda. Astrofisico Fco. Sanchez, La Laguna (Spain); Gaburro, Z.; Pavesi, L. [INFM and Dipartimento di Fisica, University of Trento, Via Sommarive 14, Povo, Trento (Italy)

    2005-06-01

    After electrochemical etching, we have made a study of the effects generated on p{sup +}-type porous silicon layers when they are left in presence of the electrolyte for different post-etching times. Using an interferometric technique, we have monitored the change of its porosity during the post-etch process due to a chemical dissolution mechanism. These data are complemented with a study of photoluminescence and transmission electron microscopy measurements for different post-etching times. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Evaluation of Antibacterial Activities of Citrus limon, Citrus reticulata, and Citrus grandis Against Pathogenic Bacteria

    Directory of Open Access Journals (Sweden)

    Sholeh Saeb

    2016-11-01

    Full Text Available Background: Microorganisms resistant to most antibiotics are rapidly spreading, and there is an urgent and continuous need for novel antimicrobial compounds. The genus Citrus belongs to the family Rutaceae has many biologically active secondary metabolites. Objectives: The purpose of this study was to evaluate antimicrobial activity of essential oil and extract of Lemon (Citrus limon, Mandarin (Citrus reticulata and Pummelo (Citrus grandis against Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Salmonella typhi. Materials and Methods: The fresh Citrus leaves were shade-dried and powdered. Antimicrobial metabolites were extracted from them by 80% methanol for extract and using a Clevenger-type apparatus for essential oil. Eight different concentrations of the each leaf extract and essential oil were prepared. The antimicrobial susceptibility assay of Citrus leaves metabolites were subjected against four bacterial strains by agar disc diffusion and E-test method. Results: In this study, minimum inhibitory concentrations (MIC of different Citrus leaf extracts were determined against all four food-borne pathogens. The C. grandis leaf essential oil had potent antimicrobial activity against all four pathogens, and the C. limon leaf essential oil was effective on Gram-positive bacteria. S. typhi was resistant against two leaves essential oils. Conclusions: The results showed that there was no antimicrobial activity effect in all extracts on tested bacteria. In this study, the antibacterial effect of essential oil of Citrus leaves on four strains of pathogenic microorganisms was confirmed. The C. grandis leaf essential oil had the most powerful antimicrobial properties, suggesting its potential application as natural preservative in foods or an effective medicine against different pathogenic microbes. Key words: Antibacterial activity, E-test, Citr

  8. Chemical surface modification of glass beads for the treatment of paper machine process waters

    Energy Technology Data Exchange (ETDEWEB)

    Jradi, Khalil, E-mail: khalil.jradi@uqtr.c [Centre de Recherche en Pates et Papiers, Universite du Quebec a Trois Rivieres, 3351 boul. des forges, C.P. 500, Trois Rivieres, QC, G9A-5H7 (Canada); Daneault, Claude [Canada Research Chair in Value-Added Paper Manufacturing (Canada); Chabot, Bruno [Centre de Recherche en Pates et Papiers, Universite du Quebec a Trois Rivieres, 3351 boul. des forges, C.P. 500, Trois Rivieres, QC, G9A-5H7 (Canada)

    2011-04-29

    Adsorption of detrimental contaminants on a solid sorbent is proposed to remove these contaminants from process waters to increase water recycling and reduce effluent loads in the papermaking industry. A self-assembly process of attaching (covalent grafting) cationic aminosilane molecules to glass beads was investigated. The existence and the hydrolytic stability of self-assembled monolayers and multilayers were confirmed by X-Ray Photoelectron Spectroscopy and contact angle measurements. Effects of reaction time and curing on aminosilane layer structures are also discussed. The curing step after silanization seems to be crucial in the hydrophobization of the quaternary ammonium silane coated onto glass beads, and curing could affect the final chemical structure of the ammonium groups of grafted organosilane. Results indicated that modified glass beads have a strong hydrophobicity, which is attributed to the hydrophobic property of the longest carbon chain grafted onto the glass surface. Adsorption of a model contaminant (stearic acid) onto chemically modified glass beads was determined using colloidal titration. Hydrophobic interactions could be the main driving force involved between the long carbon chains of stearic acid and the carbon chains of the aminosilane layers on glass bead surfaces. Finally, self-assembly processes applied onto glass beads may have two promising applications for papermaking and self-cleaning systems.

  9. Direct synthesis of hydrophobic graphene-based nanosheets via chemical modification of exfoliated graphene oxide.

    Science.gov (United States)

    Wang, Jigang; Wang, Yongsheng; He, Dawei; Liu, Zhiyong; Wu, Hongpeng; Wang, Haiteng; Zhao, Yu; Zhang, Hui; Yang, Bingyang; Xu, Haiteng; Fu, Ming

    2012-08-01

    Hydrophobic graphene-based material at the nanoscale was prepared by treatment of exfoliated graphene oxide with organic isocyanates. The lipophilic modified graphene oxide (LMGO) can then be exfoliated into the functionalized graphene nanoplatelets that can form a stable dispersion in polar aprotic solvents. AFM image shows the thickness of LMGO is approximately 1 nm. Characterization of LMGO by elemental analysis suggested that the chemical treatment results in the functionalization of the carboxyl and hydroxyl groups in GO via formation of amides and carbamate esters, respectively. The degree of GO functionalization can be controlled via either the reactivity of the isocyanate or the reaction time. Then we investigated the thermal properties of the SPFGraphene by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the TGA curve shows a greater weight loss of approximately 20% occurred indicating removal of functional groups from the LMGO sheets and an obvious exothermic peak at 176 degrees can be observed from 150 to 250 degrees. We also compared the structure of graphene oxide with the structure of chemical treated graphene oxide by FT-IR spectroscopy. The morphology and microstructure of the LMGO nanosheets were also characterized by SEM and XRD. Graphene can be used to fabricate a wide range of simple electronic devices such as field-effect transistors, resonators, quantum dots and some other extensive industrial manufacture such as super capacitor, li ion battery, solar cells and even transparent electrodes in device applications.

  10. Versatile RHDV virus-like particles: incorporation of antigens by genetic modification and chemical conjugation.

    Science.gov (United States)

    Peacey, Matthew; Wilson, Sarah; Baird, Margaret A; Ward, Vernon K

    2007-12-01

    Virus-like particles have proved to be excellent molecular scaffolds, yet the individual characteristics and immune responses generated against each VLP requires the development of a wide range of capsids for use as vaccines, molecular delivery vessels, and nanoscale templates. Here we describe the development of Rabbit haemorrhagic disease virus (RHDV)-like particles as a rapidly versatile molecular workbench, overcoming limitations imposed by established genetic antigen incorporation procedures with chimeric VLP. Production of the RHDV capsid protein in a baculovirus system led to the self-assembly of VLP which were recovered at over 99% purity and manipulated both genetically and chemically. Fusion of small peptide sequences to RHDV VLP was well tolerated, forming chimeric capsids that enhanced the presentation of foreign peptide to hybridoma T helper cells 700-fold. Rapid and simple conjugation techniques employing the hetero-bifunctional chemical linker sulfo-SMCC enabled both small peptides and whole proteins to be conjugated to the surface of RHDV VLP, overcoming limitations imposed on VLP formation and yield experienced with chimeric VLP. Administration of VLP/ovalbumin conjugate provoked high titre ovalbumin-specific antibody in mice, demonstrating the immune stimulatory properties of the capsid were conferred to conjugated foreign antigen. VLP facilitated delivery of conjugated antigen to dendritic cells, eliciting proliferative responses in naïve TCR transgenic T helper cells that were at least 10-fold greater than ovalbumin antigen delivered alone.

  11. Modification of reservoir chemical and physical factors in steamfloods to increase heavy oil recovery

    Energy Technology Data Exchange (ETDEWEB)

    Yortsos, Y.C.

    1996-12-31

    Thermal methods, and particularly steam injection, are currently recognized as the most promising for the efficient recovery of heavy oil. Despite significant progress, however, important technical issues remain open. Specifically, still inadequate is our knowledge of the complex interaction between porous media and the various fluids of thermal recovery (steam, water, heavy oil, gases, and chemicals). While, the interplay of heat transfer and fluid flow with pore- and macro-scale heterogeneity is largely unexplored. The objectives of this contract are to continue previous work and to carry out new fundamental studies in the following areas of interest to thermal recovery: displacement and flow properties of fluids involving phase change (condensation-evaporation) in porous media; flow properties of mobility control fluids (such as foam); and the effect of reservoir heterogeneity on thermal recovery. The specific projects are motivated by and address the need to improve heavy oil recovery from typical reservoirs as well as less conventional fractured reservoirs producing from vertical or horizontal wells. During this past quarter, work continued on: the development of relative permeabilities during steam displacement; the optimization of recovery processes in heterogeneous reservoirs by using optical control methods; and in the area of chemical additives, work continued on the behavior of non-Newtonian fluid flow and on foam displacements in porous media.

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

    Science.gov (United States)

    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.

  13. Controlled chemical modification of the internal surface of photonic crystal fibers for application as biosensitive elements

    Science.gov (United States)

    Pidenko, Sergey A.; Burmistrova, Natalia A.; Pidenko, Pavel S.; Shuvalov, Andrey A.; Chibrova, Anastasiya A.; Skibina, Yulia S.; Goryacheva, Irina Y.

    2016-10-01

    Photonic crystal fibers (PCF) are one of the most promising materials for creation of constructive elements for bio-, drug and contaminant sensing based on unique optical properties of the PCF as effective nanosized optical signal collectors. In order to provide efficient and controllable binding of biomolecules, the internal surface of glass hollow core photonic crystal fibers (HC-PCF) has been chemically modified with silanol groups and functionalized with (3-aminopropyl) triethoxysilane (APTES). The shift of local maxima in the HC-PCF transmission spectrum has been selected as a signal for estimating the amount of silanol groups on the HC-PCF inner surface. The relationship between amount of silanol groups on the HC-PCF inner surface and efficiency of following APTES functionalization has been evaluated. Covalent binding of horseradish peroxidase (chosen as a model protein) on functionalized PCF inner surface has been performed successively, thus verifying the possibility of creating a biosensitive element.

  14. Structural modification of titanium surface by octacalcium phosphate via Pulsed Laser Deposition and chemical treatment

    Directory of Open Access Journals (Sweden)

    I.V. Smirnov

    2017-06-01

    Full Text Available In the present study, the Pulsed Laser Deposition (PLD technique was applied to coat titanium for orthopaedic and dental implant applications. Calcium carbonate (CC was used as starting coating material. The deposited CC films were transformed into octacalcium phosphate (OCP by chemical treatments. The results of X-ray diffraction (XRD, Raman, Fourier Transform Infrared Spectroscopy (FTIR and scanning electron microscopy (SEM studies revealed that the final OCP thin films are formed on the titanium surface. Human myofibroblasts from peripheral vessels and the primary bone marrow mesenchymal stromal cells (BMMSs were cultured on the investigated materials. It was shown that all the investigated samples had no short-term toxic effects on cells. The rate of division of myofibroblast cells growing on the surface and saturated BMMSs concentration for the OCP coating were about two times faster than of cells growing on the CC films.

  15. Chemical modification of cobalt ferrite nanoparticles with possible application as asphaltene flocculant agent

    Directory of Open Access Journals (Sweden)

    G. E. Oliveira

    2013-06-01

    Full Text Available Asphaltenes can cause enormous losses in the oil industry, because they are soluble only in aromatic solvents. Therefore, they must be removed from the petroleum before it is refined, using flocculant agents. Aiming to find new materials that can work as flocculant agents to asphaltenes, cobalt ferrite nanoparticles were chemically modified through acid-base reactions using dodecylbenzene sulfonic acid (DBSA to increase their lipophilicity. Nanoparticle synthesis was performed using the co-precipitation method followed by annealing of these nanoparticles, aiming to change the structural phase. Modified and unmodified nanoparticles were tested by FTIR-ATR, XRD and TGA/DTA. In addition, precipitation onset of the asphaltenes was performed using modified and unmodified nanoparticles. These tests showed that modified nanoparticles have a potential application as flocculant agents used to remove asphaltenes before oil refining, since the presence of nanoparticles promotes the asphaltene precipitation onset with the addition of a small amount of non-solvent.

  16. Chemical modification of cobalt ferrite nanoparticles with possible application as asphaltene flocculant agent

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, G.E.; Clarindo, J.E.S.; Santo, K.S.E., E-mail: geiza.oliveira@ufes.br [Universidade Federal do Espirito Santo (CCE/DQUI/UFES), Vitoria, ES (Brazil). Centro de Ciencias Exatas. Dept. de Quimica; Souza Junior, F.G. [Universidade Federal do Rio de Janeiro (IMA/UFRJ), Rio de Janeiro, RJ (Brazil). Instituto de Macromoleculas

    2013-11-01

    Asphaltenes can cause enormous losses in the oil industry, because they are soluble only in aromatic solvents. Therefore, they must be removed from the petroleum before it is refined, using flocculant agents. Aiming to find new materials that can work as flocculant agents to asphaltenes, cobalt ferrite nanoparticles were chemically modified through acid-base reactions using dodecylbenzene sulfonic acid (DBSA) to increase their lipophilicity. Nanoparticle synthesis was performed using the co-precipitation method followed by annealing of these nanoparticles, aiming to change the structural phase. Modified and unmodified nanoparticles were tested by FTIR-ATR, XRD and TGA/DTA. In addition, precipitation onset of the asphaltenes was performed using modified and unmodified nanoparticles. These tests showed that modified nanoparticles have a potential application as flocculant agents used to remove asphaltenes before oil refining, since the presence of nanoparticles promotes the asphaltene precipitation onset with the addition of a small amount of non-solvent (author)

  17. Modification of tubular ceramic membranes with carbon nanotubes using catalytic chemical vapor deposition.

    Science.gov (United States)

    Tran, Duc Trung; Thieffry, Guillemette; Jacob, Matthieu; Batiot-Dupeyrat, Catherine; Teychene, Benoit

    2015-01-01

    In this study, carbon nanotubes (CNTs) were successfully grown on tubular ceramic membranes using the catalytic chemical vapor deposition (CCVD) method. CNTs were synthesized at 650°C for 3-6 h under a 120 mL min(-1) flow of C2H6 on ceramic membranes impregnated with iron salt. The synthesis procedure was beforehand optimized in terms of catalyst amount, impregnation duration and reaction temperature, using small pieces of tubular ceramic membranes. The yield, size and structure of the CNTs produced were characterized using thermogravimetric analysis and microscopic imaging techniques. Afterwards, preliminary filtration tests with alginate and phenol were performed on two modified tubular membranes. The results indicate that the addition of CNTs on the membrane material increased the permeability of ceramic membrane and its ability to reject alginate and adsorb phenol, yet decreased its fouling resistance.

  18. Tuning the Electrical Properties of Graphene via Nitrogen Plasma-Assisted Chemical Modification.

    Science.gov (United States)

    Jung, Min Wook; Song, Wooseok; Jung, Dae Sung; Lee, Sun Sook; Park, Chong-Yun; An, Ki-Seok

    2016-03-01

    The control in electrical properties of graphene is essentially required in order to realize graphenebased nanoelectronics. In this study, N-doped graphene was successfully obtained via nitrogen plasma treatment. Graphene was synthesized on copper foil using thermal chemical vapor deposition. After N2 plasma treatment, the G-band of the graphene was blueshifted and the intensity ratio of 2D- to G-bands decreased with increasing the plasma power. Pyrrolic-N bonding configuration induced by N2 plasma treatment was studied by X-ray photoelectron spectroscopy. Remarkably, electrical characterization including Hall measurement and I-V characteristics of the N-doped graphene exhibit semiconducting behavior as well as the n-type doping effect.

  19. Surface modification of titanium membrane by chemical vapor deposition and its electrochemical self-cleaning

    Science.gov (United States)

    Li, X. W.; Li, J. X.; Gao, C. Y.; Chang, M.

    2011-10-01

    Membrane separation is applied widely in many fields, while concentration polarization and membrane fouling, limiting its promotion and application greatly, are the bottlenecks in membrane application. Among which, membrane fouling is irreversible, membrane must be periodically cleaned or even replaced to restore permeability. Membrane cleaning has become one of the key issues in membrane separation areas. Considering incomparable electrochemical advantages of boron-doped diamond (BDD) film electrode over conventional electrode, a new composite membrane Ti/BDD, made by depositing CVD (chemical vapor deposition) boron-doped diamond film on titanium(Ti) membrane to modify porous titanium surface, that can be cleaned electrochemically is proposed. Feasibility of its preparation and application is discussed in this paper. Results shows that based on the unique electrochemical properties of diamond, cleaning level of this composite Ti/BDD membrane is significantly increased, making membrane life and efficiency improved prominently.

  20. Chemical modification of TiO2 nanotube arrays for label-free optical biosensing applications

    Science.gov (United States)

    Terracciano, Monica; Galstyan, Vardan; Rea, Ilaria; Casalino, Maurizio; De Stefano, Luca; Sbervegleri, Giorgio

    2017-10-01

    In this study, we have fabricated TiO2 nanotube arrays by the potentiostatic anodic oxidation of Ti foils in fluoride-containing electrolyte and explored them as versatile devices for biosensing applications. TiO2 nanotubes have been chemically modified in order to bind Protein A as a specific target analyte for the optical biosensing. The obtained structures have been characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, water contact angle, fluorescence microscopy, spectroscopic reflectometry and photoluminescence. Investigations show that the prepared TiO2 nanotubes, 2.5 μm long and 75 nm thick, can be easily and efficiently bio-modified, and the obtained structures are strongly photoluminescent, thus suitable for the label-free biosensing applications in the range of μM, due to their peculiar optical properties.

  1. Effect of MWCNT surface and chemical modification on in vitro cellular response

    Science.gov (United States)

    Fraczek-Szczypta, Aneta; Menaszek, Elzbieta; Syeda, Tahmina Bahar; Misra, Anil; Alavijeh, Mohammad; Adu, Jimi; Blazewicz, Stanislaw

    2012-10-01

    The aim of this study was to evaluate the impact of multi-walled carbon nanotubes (MWCNTs with diameter in the range of 10-30 nm) before and after chemical surface functionalisation on macrophages response. The study has shown that the detailed analysis of the physicochemical properties of this particular form of carbon nanomaterial is a crucial issue to interpret properly its impact on the cellular response. Effects of carbon nanotubes (CNTs) characteristics, including purity, dispersity, chemistry and dimension upon the nature of the cell environment-material interaction were investigated. Various techniques involving electron microscopy (SEM, TEM), infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectrometry, X-ray photoelectron spectroscopy have been employed to evaluate the physicochemical properties of the materials. The results demonstrate that the way of CNT preparation prior to biological tests has a fundamental impact on their behavior, cell viability and the nature of cell-nanotube interaction. Chemical functionalisation of CNTs in an acidic ambient (MWCNT-Fs) facilitates interaction with cells by two possible mechanisms, namely, endocytosis/phagocytosis and by energy-independent passive process. The results indicate that MWCNT-F in macrophages may decrease the cell proliferation process by interfering with the mitotic apparatus without negative consequences on cell viability. On the contrary, the as-prepared MWCNTs, without any surface treatment produce the least reduction in cell proliferation with reference to control, and the viability of cells exposed to this sample was substantially reduced with respect to control. A possible explanation of such a phenomenon is the presence of MWCNT's agglomerates surrounded by numerous cells releasing toxic substances.

  2. Effect of MWCNT surface and chemical modification on in vitro cellular response

    Energy Technology Data Exchange (ETDEWEB)

    Fraczek-Szczypta, Aneta; Menaszek, Elzbieta [AGH-University of Science and Technology, Department of Biomaterials, Faculty of Materials Science and Ceramics (Poland); Syeda, Tahmina Bahar; Misra, Anil; Alavijeh, Mohammad [Pharmidex Pharmaceutical Services (United Kingdom); Adu, Jimi [University of Brighton, School of Pharmacy and Biomolecular Sciences (United Kingdom); Blazewicz, Stanislaw, E-mail: blazew@agh.edu.pl [AGH-University of Science and Technology, Department of Biomaterials, Faculty of Materials Science and Ceramics (Poland)

    2012-10-15

    The aim of this study was to evaluate the impact of multi-walled carbon nanotubes (MWCNTs with diameter in the range of 10-30 nm) before and after chemical surface functionalisation on macrophages response. The study has shown that the detailed analysis of the physicochemical properties of this particular form of carbon nanomaterial is a crucial issue to interpret properly its impact on the cellular response. Effects of carbon nanotubes (CNTs) characteristics, including purity, dispersity, chemistry and dimension upon the nature of the cell environment-material interaction were investigated. Various techniques involving electron microscopy (SEM, TEM), infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectrometry, X-ray photoelectron spectroscopy have been employed to evaluate the physicochemical properties of the materials. The results demonstrate that the way of CNT preparation prior to biological tests has a fundamental impact on their behavior, cell viability and the nature of cell-nanotube interaction. Chemical functionalisation of CNTs in an acidic ambient (MWCNT-Fs) facilitates interaction with cells by two possible mechanisms, namely, endocytosis/phagocytosis and by energy-independent passive process. The results indicate that MWCNT-F in macrophages may decrease the cell proliferation process by interfering with the mitotic apparatus without negative consequences on cell viability. On the contrary, the as-prepared MWCNTs, without any surface treatment produce the least reduction in cell proliferation with reference to control, and the viability of cells exposed to this sample was substantially reduced with respect to control. A possible explanation of such a phenomenon is the presence of MWCNT's agglomerates surrounded by numerous cells releasing toxic substances.

  3. Physical and chemical modifications of surface properties lead to alterations in osteoblast behavior

    Science.gov (United States)

    Dorst, Kathryn Elizabeth

    Proper formation of the bone extracellular matrix (ECM), or osteoid, depends on the surface properties of pre-existing tissue and the aqueous chemical environment. Both of these factors greatly influence osteoblast migration, cytoskeletal organization, and calcium nodule production, important aspects when considering the biocompatibility of bone implants. By perturbing the physical and/or chemical micro-environment, it may be possible to elucidate effects on cellular function. To examine these factors, murine pre-osteoblasts (MC3T3-E1 subclones 4 and 24) were seeded on polydimethylsiloxane (PDMS) substrates containing "wide" micro-patterned ridges (20 mum width, 30 mum pitch, & 2 mum height), "narrow" micro-patterned ridges (2 mum width, 10 mum pitch, 2 mum height), no patterns (flat PDMS), and standard tissue culture (TC) polystyrene as a control. Zinc concentration was adjusted to mimic deficient (0.23 muM), serum-level (3.6 muM), and zinc-rich (50 muM) conditions. It was found that cells exhibited distinct anisotropic migration in serum-level zinc and zinc-deficient media on the wide PDMS patterns, however this was disrupted under zinc-rich conditions. Production of differentiation effectors, activated metalloproteinase-2 (MMP-2) and transforming growth factor - beta 1 (TGF-beta1), was increased with the addition of exogenous zinc. Early stage differentiation, via alkaline phosphatase, was modified by zinc levels on patterned polydimethylsiloxane (PDMS) surfaces, but not on flat PDMS or tissue culture polystyrene (TC). Late stage differentiation, visualized through calcium phosphate nodules, was markedly different at various zinc levels when the cells were cultured on TC substrates. This susceptibility to zinc content can lead to differences in bone mineral production on certain substrates if osteoblasts are not able to maintain and remodel bone effectively, a process vital to successful biomaterial integration.

  4. Chemical characterization of Citrus limon var. pompia and incorporation in phospholipid vesicles for skin delivery.

    Science.gov (United States)

    Manconi, Maria; Manca, Maria Letizia; Marongiu, Francesca; Caddeo, Carla; Castangia, Ines; Petretto, Giacomo Luigi; Pintore, Giorgio; Sarais, Giorgia; D'hallewin, Guy; Zaru, Marco; Bacchetta, Gianluigi; Fadda, Anna Maria

    2016-06-15

    The components of pompia, a hybrid Citrus species cultivated only in Sardinia (Italy), were extracted using an environmentally-friendly method and food-grade solvents. Taking into account that only few data are available on pompia composition, the phytochemical fingerprint of its rind extract was obtained by accurate component separation and identification, combining HPLC and mass spectrometry. Different flavones such as naringin (23.77μg/mg), neoeriocitrin (46.53μg/mg) and neohesperidin (44.57μg/mg) were identified. Additionally, the antioxidant activity and phenolic content were confirmed by DPPH and Folin-Ciocalteu assays. The whole extract was incorporated in innovative phospholipid vesicles, namely glycerosomes, hyalurosomes and glycerol containing hyalurosomes, which were prepared using a high ratio of extract/phospholipid (1/3.5w/w). The in vitro biocompatibility of the nanoincorporated extract and its ability to potentiate the aptitude of the extract to counteract oxidative stress in skin cells were evaluated. The vesicles, especially glycerol containing hyalurosomes, were able to prevent oxidative damage and death of both keratinocytes and fibroblasts, promoting their viability. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Chemical Composition and Radical Scavenging Activity of Citrus Limon Peel Essential Oil

    Directory of Open Access Journals (Sweden)

    Mona Ghoorchibeigi

    2017-02-01

    Full Text Available The water distillated essential oil of Citruslimon collected from Ramsar, Province of Mazandaran, North of Iran collected in December 2013, was analyzed using gas chromatography (GC and gas chromatography-mass spectroscopy (GC-MS. The yield of oil was 0.23% w/w. Twenty-one components representing 100% of the essential oil were characterized. Limonene (61.4%, b-pinene (13.1% and g-terpinene (11.3% were identified as the main constituents in the volatile oil. The antioxidant ability of the oil was examined by free radical scavenging method using 2,2-diphenyl-1-picrylhydrazyl (DPPH radical at different concentration of the oil. The Citruslimon oil exhibited free-radical-scavenging properties with IC50 value of 284.71µg ml-1.

  6. The effect of chemical modification of SiO{sub 2} nanoparticles on the nanofiltration characteristics of polyamide membrane

    Energy Technology Data Exchange (ETDEWEB)

    Rakhshan, Nasim; Pakizeh, Majid [Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

    2015-12-15

    This study presents the synthesis and characterization of oleic acid (OA)-modified silica/polyamide (PA) nanocomposite membranes. The thin film composite (TFC) polyamide was prepared with M-phenylendiamine (MPD) and trimesoyl chloride (TMC) via interfacial polymerization over porous polysulfone. Five different thin film nanocomposite (TFN) membranes were fabricated by dispersing OA-modified silica nanoparticles in TMC solution. Chemical and thermal properties, surface morphology, roughness, film thickness and hydrophilicity of synthesized membranes were characterized by ATR-IR, TGA, FESEM, AFM, TEM and contact angle analysis. The results showed that incorporating OA-modified silica into thin film layer improved chemical and physical properties of nanocomposite membranes. The effects of modification of nano silica on pure water flux and MgSO{sub 4} rejection were investigated. OA-modified silica/PA membranes showed higher pure water flux in comparison with neat polyamide TFC membrane but lower than unmodified silica/PA membrane; while significant increase in salt rejection was exhibited for OA-modified silica/PA membranes. The maximum rejection for OA-modified and unmodified nanocomposite membrane was obtained about 98.7% and 95.2%, respectively.

  7. Chemical modification of hygroscopic magnesium carbonate into superhydrophobic and oleophilic sorbent suitable for removal of oil spill in water

    Energy Technology Data Exchange (ETDEWEB)

    Patowary, Manoj [Advanced Technology Development Center, Indian Institute of Technology Kharagpur, West Bengal 721302 (India); Ananthakrishnan, Rajakumar, E-mail: raja.iitchem@yahoo.com [Department of Chemistry, Indian Institute of Technology Kharagpur, West Bengal 721302 (India); Pathak, Khanindra [Department of Mining Engineering, Indian Institute of Technology Kharagpur, West Bengal 721302 (India)

    2014-11-30

    Graphical abstract: - Highlights: • A superhydrophobic and oleophilic sorbent powder was developed by surface modification of commercially available hygroscopic magnesium carbonate with palmitic acid. • The sorbent powder is capable of scavenging oil for about three times its weight. • Reusability test of the sorbent powder infers the retention of hydrophobic as well as oleophilic character even after three times of re-use. • The powder was found to possess sufficient buoyancy, high rate of uptake and selectivity towards oil which is necessary for oil spill clean-ups. - Abstract: The wettability of hygroscopic magnesium carbonate has been modified to develop a superhydrophobic and oleophilic sorbent for oil spill clean-ups via a simple chemical process using palmitic acid. The prepared material was characterized using X-ray diffraction, Fourier transform infra-red spectroscopy, and scanning electron microscopy. Wettability test infers that the sorbent has a static water contact angle of 154 ± 1°, thereby indicating its superhydrophobic character. The sorbent was capable of scavenging oil for about three times its weight, as determined from oil sorption studies, carried out using the sorbent on model oil-water mixture. Interestingly, the chemically modified sorbent has high selectivity, buoyancy, and rate of uptake of oil. Further, the reusability studies confirm the repeatable usage of the sorbent and its efficacy in oil spill remediation.

  8. A study of chemical modifications of a Nafion membrane by incorporation of different room temperature ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Martinez de Yuso, M.V.; Rodriguez-Castellon, E. [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Malaga (Spain); Neves, L.A.; Coelhoso, I.M.; Crespo, J.G. [REQUIMTE/CQFB, Departamento de Quimica, Universidade Nova de Lisboa, Caparica (Portugal); Benavente, J. [Departamento de Fisica Aplicada I, Facultad de Ciencias, Universidad de Malaga (Spain)

    2012-08-15

    Surface and bulk chemical changes in a Nafion membrane as a result of room temperature ionic liquids (RTILs) incorporation were determined by X-ray photoelectron spectroscopy (XPS) and elemental analysis, respectively. RTILs with different physicochemical properties were selected. Two imidazolium based RTIL-cations (1-octyl-3-methylimidazolium and 1-butyl-3-methylimidazolium) were used to detect the effect of cation size on membrane modification, while the effect of the RTIL hydrophilic/hydrophobic character was also considered by choosing different anions. Angle resolved XPS measurements (ARXPS) were carried out varying the angle of analysis between 15 and 75 to get elemental information on the Nafion/RTIL-modified membranes interactions for a deepness of around 10 nm. Moreover, changes in the RTIL-modified membranes associated to thermal effect were also considered by analyzing the samples after their heating at 120 C for 24 h. Agreement between both chemical techniques, bulk and destructive elemental analysis and surface and non-destructive XPS, were obtained. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. A review of chemical surface modification of bioceramics: effects on protein adsorption and cellular response.

    Science.gov (United States)

    Lee, Wing-Hin; Loo, Ching-Yee; Rohanizadeh, Ramin

    2014-10-01

    Calcium phosphates (CaPs) are ideal biomaterials for bone repair because of the similarities between their chemical structure and the mineral phase of hard biological tissues (e.g., bones and teeth). Since CaP bone grafts exhibit superior biocompatibility and strong osseointegration properties, they have been widely investigated for use as an in situ carrier for delivery of anti-resorptive and osteogenic drugs. The surface properties of CaP govern the affinity and the binding mechanisms between biological macromolecules (e.g., proteins) and the CaP surface, which indirectly determines the interactions between bone cells and implanted CaP biomaterials. These surface properties ultimately play a pivotal role in determining the success of CaP as bone implants and/or drug carriers. This review provides an in-depth discussion of the current methodologies used to regulate the surface chemistry of CaP and their subsequent effects in regards to protein adsorption and delivery, as well as cell/materials interactions.

  10. Modification of apparent fission yields by Chemical Fractionation following Fission (CFF)

    Science.gov (United States)

    Hohenberg, Charles; Meshik, Alex

    2008-04-01

    Grain-by-grain studies of the 2 billion year old Oklo natural reactor, using laser micro-extraction^1,2, yield detailed information about Oklo, a water-moderated pulsed reactor, cycle times, total neutron fluence and duration, but it also demonstrates Chemical Fractionation following Fission. In the CFF process, members of an isobaric yield chain with long half-lives are subject to migration before decay can occur. Of particular interest is the 129 isobar where 17 million ^129I can migrate out of the host grain before decay, and iodine compounds are water soluble. This is amply demonstated by the variation of Xe spectra between micron-sized uranium-bearing minerals and adjacent uranium-free minerals. Fission 129 yields for the spontaneous fission of ^238U generally come from measured ^129Xe in pitchblend^2, ores emplaced by aqueous activity, and are incorrect due to the CFF process. ^238U yields for the 131 and 129 chains, reported in Hyde^3, as 0.455 +- .02 and < 0.012, respectively, the latter being anomalously low. ^1A Meshik, C Hohenberg and O Pravdivtesva, PRL 93, 182302 (2004); A Meshik Sci. Am. Nov (2005), 55; ^2E K Hyde, Nucl Prop of Heavy Elements III (1964).

  11. Effects of chemical modifications of heme on kinetics of carbon monoxide binding to free home

    Energy Technology Data Exchange (ETDEWEB)

    Sono, M.; McCray, J.A.; Asakura, T.

    1977-11-10

    The rates of carbon monoxide recombination to six different kinds of chemically modified heme with various substituents at positions 2 and 4 have been studied in the protein-free state (free heme) by the laser flash photolysis method in a mixture of ethylene glycol and 0.02 N NaOH (80:20, v/v) (80% ethylene glycol). The carbon monoxide combination rate constants to the various free hemes obtained in 80% ethylene glycol at 22/sup 0/ were 1.4, 2.1, 2.1, 3.7, 4.5, and 6.4 x 10/sup 7/ M/sup -1/ s/sup -1/ for 2,4-diformyl-, spirographis (2-formyl-4-vinyl-), isospirographis (2-vinyl-4-formyl-) proto-(2,4-divinyl-), deutero-(2,4-dihydrogen-), and meso-(2,4-diethyl-), hemes, respectively. This order of increase in carbon monoxide combination rate constants for these hemes correlates exactly with decrease in electron attractivity of heme side chains (i.e., increase in pK/sub 3/, basicity of nitrogen base of prophyrin) and is completely opposite to that obtained for carbon monoxide binding to these hemes reconstituted with apomyoglobin. Contrary to the results for myoglobin, the two isomers of monoformyl-monovinylheme exhibited similar optical properties and the same combination rate constant indicating that the differences in the optical and kinetic results observed in myoglobin are due to different interactions of these isomeric hemes with protein.

  12. Diarylheptanoids, new phytoestrogens from the rhizomes of Curcuma comosa: Isolation, chemical modification and estrogenic activity evaluation.

    Science.gov (United States)

    Suksamrarn, Apichart; Ponglikitmongkol, Mathurose; Wongkrajang, Kanjana; Chindaduang, Anon; Kittidanairak, Suthadta; Jankam, Aroon; Yingyongnarongkul, Boon-ek; Kittipanumat, Narin; Chokchaisiri, Ratchanaporn; Khetkam, Pichit; Piyachaturawat, Pawinee

    2008-07-15

    Three new diarylheptanoids, a 1:2 mixture of (3S)- and (3R)-1-(4-methoxyphenyl)-7-phenyl-(6E)-6-hepten-3-ol (13a and 13b) and 1-(4-hydroxyphenyl)-7-phenyl-(6E)-6-hepten-3-one (15), together with two synthetically known diarylheptanoids 1,7-diphenyl-(1E,3E,5E)-1,3,5-triene (9) and 1-(4-hydroxyphenyl)-7-phenyl-(4E,6E)-4,6-heptadien-3-one (16), and nine known diarylheptanoids, 2, 8, 10-12, 14, a 3:1 mixture of 17a and 17b, and 18, were isolated from the rhizomes of Curcuma comosa Roxb. The absolute stereochemistry of the isolated compounds has also been determined using the modified Mosher's method. The isolated compounds and the chemically modified analogues were evaluated for their estrogenic-like transcriptional activity using RT-PCR in HeLa cell line. Some of the isolated diarylheptanoids and their modified analogues exhibited estrogenic activity comparable to or higher than that of the phytoestrogen genistein. Based on the transcriptional activation of both estrogenic targets, Bcl-xL and ERbeta gene expression, the structural features for a diarylheptanoid to exhibit high estrogenic activity are the presence of an olefinic function conjugated with the aromatic ring at the 7-position, a keto group at the 3-position, and a phenolic hydroxyl group at the p-position of the aromatic ring attached to the 1-position of the heptyl chain.

  13. Nitrone Derivatives as Therapeutics: From Chemical Modification to Specific-targeting.

    Science.gov (United States)

    Durand, Grégory; Poeggeler, Burkhard; Rosselin, Marie

    2017-03-03

    Nitrones have been extensively used for the detection of transient free radicals using electron paramagnetic resonance. Since the mid-80's, nitrones have also been widely used as protective agents against oxidative stress in several biological models. Due to the high potency of nitrones, there has been extensive research on the development of derivatives with improved biological and spin trapping properties as well as enhanced intra-cellular compartmentalization. The chemical and pharmacological properties of nitrones depend mainly on the connectivity as well as on the nature and the position of the substituents on the nitrone group. Therefore novel bioactive molecules have been designed and the development of specific nitrone derivatives is aimed at providing new therapeutic approaches and perspectives in prevention, treatment and rehabilitation. This review focusses on the effects that are exerted by the most promising nitrone antioxidants that are available. A comprehensive description of the unique molecular mechanism and mediators that are targeted by these compounds is given to guide and enable novel and successful approaches to the treatment of a broad spectrum of diseases associated with stress and aging. New promising nitrone compounds are now available for further development by translational medicine that exert superior bioactivity and efficacy.

  14. Impacts of chemical modification on the toxicity of diverse nanocellulose materials to developing zebrafish.

    Science.gov (United States)

    Harper, Bryan J; Clendaniel, Alicea; Sinche, Federico; Way, Daniel; Hughes, Michael; Schardt, Jenna; Simonsen, John; Stefaniak, Aleksandr B; Harper, Stacey L

    2016-06-01

    Cellulose is an abundant and renewable resource currently being investigated for utility in nanomaterial form for various promising applications ranging from medical and pharmaceutical uses to mechanical reinforcement and biofuels. The utility of nanocellulose and wide implementation ensures increasing exposure to humans and the environment as nanocellulose-based technologies advance. Here, we investigate how differences in aspect ratio and changes to surface chemistry, as well as synthesis methods, influence the biocompatibility of nanocellulose materials using the embryonic zebrafish. Investigations into the toxicity of neutral, cationic and anionic surface functionalities revealed that surface chemistry had a minimal influence on the overall toxicity of nanocellulose materials. Higher aspect ratio cellulose nanofibers produced by mechanical homogenization were, in some cases, more toxic than other cellulose-based nanofibers or nanocrystals produced by chemical synthesis methods. Using fluorescently labeled nanocellulose we were able to show that nanocellulose uptake did occur in embryonic zebrafish during development. We conclude that the benign nature of nanocellulose materials makes them an ideal platform to systematically investigate the inherent surface features driving nanomaterial toxicity in order to create safer design principles for engineered nanoparticles.

  15. Chemical modification of SWNT alters in vitro cell-SWNT interactions.

    Science.gov (United States)

    Nimmagadda, Aditya; Thurston, Karen; Nollert, Matthias U; McFetridge, Peter S

    2006-03-01

    Single-walled carbon nanotubes (SWNT) have been the focus of considerable attention as a material with extraordinary mechanical and electrical properties. SWNT have been proposed in a number of biomedical applications, including neural, bone, and dental tissue engineering. In these applications, it is clear that surrounding tissues will come into surface contact with SWNT composites, and compatibility between SWNT and host cells must be addressed. This investigation describes the gross physical and chemical effects of different SWNT preparations on in vitro cell viability and metabolic activity. Three different SWNT preparations were analyzed: as purchased (AP-NT), purified (PUR-NT), and functionalized with glucosamine (GA-NT), over concentrations of 0.001-1.0% (wt/vol). With the exception of the lowest SWNT concentrations, increasing concentrations of SWNT resulted in a decrease of cell viability, which was dependent on SWNT preparation. The metabolic activity of 3T3 cells was also dependent on SWNT preparation and concentration. These investigations have shown that these SWNT preparations have significant effects on in vitro cellular function that cannot be attributed to one factor alone, but are more likely the result of several unfavorable interactions. Effects, such as destabilizing the cell membrane, soluble toxic contaminants, and limitations in mass transfer as the SWNT coalesce into sheets, may all play a role in these interactions. Using comprehensive purification processes and modifying the NT-surface chemistry to introduce functional groups or reduce hydrophobicity or both, these interactions can be significantly improved.

  16. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study

    Science.gov (United States)

    Chuang, Cheng-Hao; Ray, Sekhar C.; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-02-01

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements.

  17. Chemical modification of projectile residues and target material in a MEMIN cratering experiment

    Science.gov (United States)

    Ebert, Matthias; Hecht, Lutz; Deutsch, Alexander; Kenkmann, Thomas

    2013-01-01

    In the context of the MEMIN project, a hypervelocity cratering experiment has been performed using a sphere of the iron meteorite Campo del Cielo as projectile accelerated to 4.56 km s-1, and a block of Seeberger sandstone as target material. The ejecta, collected in a newly designed catcher, are represented by (1) weakly deformed, (2) highly deformed, and (3) highly shocked material. The latter shows shock-metamorphic features such as planar deformation features (PDF) in quartz, formation of diaplectic quartz glass, partial melting of the sandstone, and partially molten projectile, mixed mechanically and chemically with target melt. During mixing of projectile and target melts, the Fe of the projectile is preferentially partitioned into target melt to a greater degree than Ni and Co yielding a Fe/Ni that is generally higher than Fe/Ni in the projectile. This fractionation results from the differing siderophile properties, specifically from differences in reactivity of Fe, Ni, and Co with oxygen during projectile-target interaction. Projectile matter was also detected in shocked quartz grains. The average Fe/Ni of quartz with PDF (about 20) and of silica glasses (about 24) are in contrast to the average sandstone ratio (about 422), but resembles the Fe/Ni-ratio of the projectile (about 14). We briefly discuss possible reasons of projectile melting and vaporization in the experiment, in which the calculated maximum shock pressure does not exceed 55 GPa.

  18. Colour and chemical changes of the lime wood surface due to CO2 laser thermal modification

    Science.gov (United States)

    Kubovský, Ivan; Kačík, František

    2014-12-01

    We studied colour and main wood components changes of lime wood caused by CO2 laser beam irradiation. The dry surface of lime wood (Tilia vulgaris L.) was irradiated with the CO2 laser beam (wavelength of 10.6 μm) at different exposures (expressed as the irradiation dose). Colour changes were monitored by the spectrophotometer, chemical changes were observed by the ATR-FTIR spectroscopy and carbohydrates were analysed by the HPLC method. With the growth of the irradiation dose (from 8.1 to 28.7 J cm-2) lightness (ΔL*) decrease and increase of the total colour difference (ΔE*) were observed. Higher values of the input energy lead to accelerating the mutual reaction of the functional groups resulting in the subsequent condensation of lignin. The total decrease in saccharides at the highest irradiation dose reaches 27.39% of the initial amount of saccharides in the reference sample. We have observed degradation and loss of hemicelluloses.

  19. Surface modification of ceria nanoparticles and their chemical mechanical polishing behavior on glass substrate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Zefang, E-mail: zfzhang@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shanghai Xinanna Electronic Technology Co., Ltd., Shanghai 201506 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Yu Lei [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Liu Weili, E-mail: rabbitlwl@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shanghai Xinanna Electronic Technology Co., Ltd., Shanghai 201506 (China); Song Zhitang [State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shanghai Xinanna Electronic Technology Co., Ltd., Shanghai 201506 (China)

    2010-04-01

    To improve their chemical mechanical polishing (CMP) performance, ceria nanoparticles were surface modified with {gamma}-aminopropyltriethoxysilane (APS) through silanization reaction with their surface hydroxyl group. The compositions, structures and dispersibility of the modified ceria particles were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), laser particle size analyzer, zeta potential measurement and stability test, respectively. The results indicated that APS had been successfully grafted onto the surface of ceria nanoparticles, which led to the modified ceria nanoparticles with better dispersibility and stability than unmodified ceria particles in aqueous fluids. Then, CMP performance of the modified ceria nanoparticles on glass substrate was investigated. Experimental results showed that the modified ceria particles exhibited lower material removal rate (MRR) but much better surface quality than unmodified ceria particles, which may be explained by the hardness reduction of ceria particles, the enhancement of lubrication of the particles and substrate surfaces, and the elimination of the agglomeration among the ceria particles.

  20. Chemical modification of silicon surfaces for the application in soft lithography

    Energy Technology Data Exchange (ETDEWEB)

    Gilles, S.

    2007-05-15

    The objective of this work was to chemically modify silicon surfaces by anchoring functional molecules. A major part was devoted to the investigation and improvement of the self-assembly process of organosilanes on oxidized silicon surfaces. The formation of a release agent layer with perfluorinated alkylsilanes was performed by vapor phase deposition. An advanced vapor phase deposition device, called CASINO device, was built to enhance the qualities of the thin films. It is possible to carry out cleaning and silanization in a closed chamber without exposing the samples to air in between. Thereby surface contamination is avoided. Experiments with the new device were performed following examples given in literature. To optimize the silanization process in the CASINO device, it was also planned to apply heat treatment of the sample during or after the deposition process. Surface layers of thiolterminated and of aminoterminated molecules were investigated as adhesive layer for the linkage of metal structures to silicon surfaces, e.g. Shuttle-Transfer Printing with gold crossbar electrodes. First, thiol- and aminoterminated organosilane SAMs were tested as adhesive layers for gold. The surface modified with thiolterminated silane molecules was further examined. Adhesion was promoted only after heat treatment of a thiolmodified silicon substrate with a gold layer on top. (orig.)

  1. Chemical modification of zinc hydroxide nitrate and Zn-Al-layered double hydroxide with dicarboxylic acids.

    Science.gov (United States)

    Arizaga, Gregorio Guadalupe Carbajal; Mangrich, Antonio Salvio; da Costa Gardolinski, José Eduardo Ferreira; Wypych, Fernando

    2008-04-01

    A zinc hydroxide nitrate (ZHN), Zn5(OH)8(NO3)2.2H2O, and a layered double hydroxide (LDH), Zn/Al-NO3 were doped with 0.2 mol% of Cu2+ during alkaline chemical precipitation. Both compounds were intercalated with adipate ((-)OOC(CH2)4COO(-)), azelate ((-)OOC(CH2)7COO(-)), and benzoate (C6H5COO(-)) ions through ion exchange reactions. Solid state 13C nuclear magnetic resonance spectroscopy showed only one signal of carboxylic carbon for adipate and azelate intercalated into LDH, indicating that the carboxylic ends of both acids were equivalent, whereas the signal split when the intercalation was into the ZHN matrix. The electron paramagnetic resonance (EPR) spectrum of copper in octahedral cation sites of LDH layers showed a Hamiltonian parameter ratio g ||/A ||=170 cm and, after intercalation of adipate, the change was not significant: g ||/A ||=174 cm. This result indicates that the carboxylate ions did not coordinate with copper centers. Nonetheless, the intercalation of azelate increased the ratio to g ||/A ||=194 cm, similar to the spectra of ZHN modified with adipate, g ||/A ||=199 cm, and azelate, g ||/A ||=183 and 190 cm, which are associated with the coordination of copper by weak carboxylate anion ligands. Copper occupies octahedral or tetrahedral sites in ZHN layers, and the EPR spectra indicate that the dicarboxylate anions reacted preferentially with octahedral sites, whereas benzoate reacted with both sites.

  2. Chemical modification and degradation of atrazine in Medicago sativa through multiple pathways.

    Science.gov (United States)

    Zhang, Jing Jing; Lu, Yi Chen; Yang, Hong

    2014-10-08

    Atrazine is a member of the triazine herbicide family intensively used to control weeds for crop production. In this study, atrazine residues and its degraded products in alfalfa (Medicago sativa) were characterized using UPLC-TOF-MS/MS. Most of atrazine absorbed in plants was found as chemically modified derivatives like deisopropylated atrazine (DIA), dehydrogenated atrazine (DHA), or methylated atrazine (MEA), and some atrazine derivatives were conjugated through different functional groups such as sugar, glutathione, and amino acids. Interestingly, the specific conjugates DHA+hGSH (homoglutathione) and MEA-HCl+hGSH in alfalfa were detected. These results suggest that atrazine in alfalfa can be degraded through different pathways. The increased activities of glycosyltransferase and glutathione S-transferase were determined to support the atrazine degradation models. The outcome of the work uncovered the detailed mechanism for the residual atrazine accumulation and degradation in alfalfa and will help to evaluate whether the crop is suitable to be cultivated in the atrazine-polluted soil.

  3. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study

    Science.gov (United States)

    Chuang, Cheng-Hao; Ray, Sekhar C.; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-01-01

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements. PMID:28186190

  4. Critical Chemical-Mechanical Couplings that Define Permeability Modifications in Pressure-Sensitive Rock Fractures

    Energy Technology Data Exchange (ETDEWEB)

    Derek Elsworth; Abraham Grader; Susan Brantley

    2007-04-25

    This work examined and quantified processes controlling changes in the transport characteristics of natural fractures, subjected to coupled thermal-mechanical-chemical (TMC) effects. Specifically, it examined the effects of mineral dissolution and precipitation mediated by mechanical effects, using laboratory through-flow experiments concurrently imaged by X-ray CT. These were conducted on natural and artificial fractures in cores using water as the permeant. Fluid and mineral mass balances are recorded and are correlated with in-sample saturation, porosity and fracture aperture maps, acquired in real-time by X-ray CT-imaging at a maximum spatial resolution of 15-50 microns per pixel. Post-test, the samples were resin-impregnated, thin-sectioned, and examined by microscopy to define the characteristics of dissolution and precipitation. The test-concurrent X-ray imaging, mass balances, and measurements of permeability, together with the post-test microscopy, were used to define dissolution/precipitation processes, and to constrain process-based models. These models define and quantify key processes of pressure solution, free-face dissolution, and shear-dilation, and the influence of temperature, stress level, and chemistry on the rate of dissolution, its distribution in space and time, and its influence on the mechanical and transport properties of the fracture.

  5. Modification of reservoir chemical and physical factors in steamfloods to increase heavy oil recovery

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-31

    Thermal methods, and particularly steam injection, are currently recognized as the most promising for the efficient recovery of heavy oil. Despite significant progress, however, important technical issues remain open. Specifically, still inadequate is our knowledge of the complex interaction between porous media and the various fluids of thermal recovery (steam, water, heavy oil, gases, and chemicals). While, the interplay of heat transfer and fluid flow with pore- and macro-scale heterogeneity is largely unexplored. The objectives of this contract are to continue previous work and to carry out new fundamental studies in the following areas of interest to thermal recovery: displacement and flow properties of fluids involving phase change (condensation-evaporation) in porous media; flow properties of mobility control fluids (such as foam); and the effect of reservoir heterogeneity on thermal recovery. The specific projects are motivated by and address the need to improve heavy oil recovery from typical reservoirs as well as less conventional fractured reservoirs producing from vertical or horizontal wells. During this quarter work continued on: development of relative permeabilities during steam injection; optimization of recovery processes in heterogeneous reservoirs by using optimal control methods; and behavior of non-Newtonian fluid flow and on foam displacements in porous media.

  6. Chemical surface modification of calcium carbonate particles with stearic acid using different treating methods

    Science.gov (United States)

    Cao, Zhi; Daly, Michael; Clémence, Lopez; Geever, Luke M.; Major, Ian; Higginbotham, Clement L.; Devine, Declan M.

    2016-08-01

    Calcium carbonate (CaCO3) is often treated with stearic acid (SA) to decrease its polarity. However, the method of application of the SA treatments has a strong influence on CaCO3 thermoplastic composite's interfacial structure and distribution. Several of papers describe the promising effects of SA surface treatment, but few compare the treatment process and its effect on the properties of the final thermoplastic composite. In the current study, we assessed a new SA treatment method, namely, complex treatment for polymer composite fabrication with HDPE. Subsequently, a comparative study was performed between the "complex" process and the other existing methods. The composites were assessed using different experiments included scanning electron microscopy (SEM), void content, density, wettability, differential scanning calorimetry (DSC), and tensile tests. It was observed that the "complex" surface treatment yielded composites with a significantly lower voids content and higher density compared to other surface treatments. This indicates that after the "complex" treatment process, the CaCO3 particles and HDPE matrix are more tightly packed than other methods. DSC and wettability results suggest that the "wet" and "complex" treated CaCO3 composites had a significantly higher heat of fusion and moisture resistance compared to the "dry" treated CaCO3 composites. Furthermore, "wet" and "complex" treated CaCO3 composites have a significantly higher tensile strength than the composites containing untreated and "dry" treated CaCO3. This is mainly because the "wet" and "complex" treatment processes have increased adsorption density of stearate, which enhances the interfacial interaction between matrix and filler. These results confirm that the chemical adsorption of the surfactant ions at the solid-liquid interface is higher than at other interface. From this study, it was concluded that the utilization of the "complex" method minimised the negative effects of void

  7. Chemical modification of methionines in a cobra venom cytotoxin differentiates between lytic and binding domains.

    Science.gov (United States)

    Stevens-Truss, R; Hinman, C L

    1996-08-01

    Cytotoxin-III from Naja naja atra (CTX) was chemically modified at either or both of its two methionine residues: Over 50% oxidation of methionine-26 occurred with a 1:1 molar ratio of chloramine-T:methionine; at a 5:1 molar ratio, methionine-26 was almost completely oxidized, while methionine-24 was modified only 26%; at a 10:1 molar ratio, both methionines were completely oxidized. Each oxidized derivative demonstrated a lower toxicity toward T-cells than toward heart cells. Conversely, binding to heart cells was affected more than binding to T-cells. Cyanogen bromide cleaved native CTX at both methionines, excising phenyl-alanine-25 and methionine-26 and converting methionine-24 to homoserine lactone. This treatment of CTX eliminated cytotoxicity toward both heart and T-cells, but had only a modest effect upon T-cell binding, as had 50% oxidation of methionine-26, suggesting that CTX lytic and binding regions may be distinct. A selective loss in heart cell binding following oxidation of methionine-24 further suggests that different parts of CTX may interact with the two types of target cells. Perturbation of the relatively flat hydrophobic surface of the CTX' triple-stranded beta-sheet could result from the introduction of negative charge due to methionine-24 oxidation. Alternatively, amino acid side chain participation in a CTX binding domain may be altered by the potential formation of a new hydrogen bond between tyrosine-51 and methionine-24 sulfoxide, as revealed by computer modeling of the completely oxidized CTX derivative.

  8. Swift heavy ion induced modification in morphological and physico-chemical properties of tin oxide nanocomposites

    Science.gov (United States)

    Jaiswal, Manoj Kumar; Kanjilal, D.; Kumar, Rajesh

    2013-11-01

    Nanocomposite thin films of tin oxide (SnO2)/titanium oxide (TiO2) were grown on silicon (1 0 0) substrates by electron beam evaporation deposition technique using sintered nanocomposite pellet of SnO2/TiO2 in the percentage ratio of 95:5. Sintering of the nanocomposite pellet was done at 1300 °C for 24 h. The thicknesses of these films were measured to be 100 nm during deposition using piezo-sensor attached to the deposition chamber. TiO2 doped SnO2 nanocomposite films were irradiated by 100 MeV Au8+ ion beam at fluence range varying from 1 × 1011 ions/cm2 to 5 × 1013 ions/cm2 at Inter University Accelerator Center (IUAC), New Delhi, India. Chemical properties of pristine and ion irradiation modified thin films were characterized by Fourier Transform Infrared (FTIR) spectroscopy. FTIR peak at 610 cm-1 confirms the presence of O-Sn-O bridge of tin (IV) oxide signifying the composite nature of pristine and irradiated thin films. Atomic Force Microscope (AFM) in tapping mode was used to study the surface morphology and grain growth due to swift heavy ion irradiation at different fluencies. Grain size calculations obtained from sectional analysis of AFM images were compared with results obtained from Glancing Angle X-ray Diffraction (GAXRD) measurements using Scherrer’s formulae. Phase transformation due to irradiation was observed from Glancing Angle X-ray Diffraction (GAXRD) results. The prominent 2θ peaks observed in GAXRD spectrum are at 30.67°, 32.08°, 43.91°, 44.91° and 52.35° in the irradiated films.

  9. Enhanced performance of electrostatic precipitators through chemical modification of particle resistivity and cohesion

    Energy Technology Data Exchange (ETDEWEB)

    Durham, M.D.; Baldrey, K.E.; Bustard, C.J. [ADA Technologies, Inc., Englewood, CO (United States)

    1995-11-01

    Control of fine particles, including particulate air toxics, from utility boilers is required near-term by state and federal air regulations. Electrostatic precipitators (ESP) serve as the primary air pollution control device for the majority of coal-fired utility boilers in the Eastern and Midwestern united States. Cost-effective retrofit technologies for fine particle control, including flue gas conditioning, are needed for the large base of existing ESPs. Flue has conditioning is an attractive option because it requires minimal structural changes and lower capital costs. For flue gas conditioning to be effective for fine particle control, cohesive and particle agglomerating agents are needed to reduce reentrainment losses, since a large percentage of particulate emissions from well-performing ESPs are due to erosion, rapping, and non-rapping reentrainment. A related and somewhat ironic development is that emissions reductions of SO{sub 2} from utility boilers, as required by the Title IV acid rain program of the 1990 Clean Air Act amendments, has the potential to substantially increase particulate air toxics from existing ESPs. The switch to low-sulfur coals as an SO{sub 2} control strategy by many utilities has exacerbated ESP performance problems associated with high resistivity flyash. The use of flue gas conditioning has increased in the past several years to maintain adequate performance in ESPs which were not designed for high resistivity ash. However, commercially available flue gas conditioning systems, including NH{sub 3}/SO{sub 3} dual gas conditioning systems, have problems and inherent drawbacks which create a need for alternative conditioning agents. in particular, NH{sub 3}/SO{sub 3} systems can create odor and ash disposal problems due to ammonia outgassing. In addition, there are concerns over chemical handling safety and the potential for accidental releases.

  10. Chemical modification of titanium isopropoxide for producing stable dispersion of titania nano-particles

    Energy Technology Data Exchange (ETDEWEB)

    Mahata, S. [National Institute of Science and Technology, Berhampur, Orissa (India); Mondal, B., E-mail: bnmondal@rediffmail.com [Centre for Advanced Materials Processing, Central Mechanical Engineering Research Institute, Durgapur 713 209 (India); Mahata, S.S. [National Institute of Science and Technology, Berhampur, Orissa (India); Usha, K. [Bengal College of Engineering and Technology, Durgapur (India); Mandal, N.; Mukherjee, K. [Centre for Advanced Materials Processing, Central Mechanical Engineering Research Institute, Durgapur 713 209 (India)

    2015-02-01

    Stable colloidal TiO{sub 2} nano-particles are synthesized through the controlled hydrolysis of chemically modified titanium (Ti) isopropoxide with acetylacetone and acetic acid whereas ammonium salts of poly(acrylic acid) is used as a dispersing agent. Acetylacetone and acetic acid used as chelating ligand to retard the hydrolysis and condensation rates. The process is found promising for producing homogeneous aqueous phase colloidal dispersion of TiO{sub 2} particles. Fourier transformed infrared and nuclear magnetic resonance spectra reveal the formation of monodentate bridging of ligands with Ti-isopropoxide. UV–Vis spectroscopy confirms the effective adsorption of poly(acrylic acid) within the modified Ti precursor. Zeta potential of modified titanium isopropoxide precursor is measured to understand its stability in different pH. The thermal stability of the precursors modified with different chelating ligands and dispersing agent has been studied using thermo-gravimetric in conjunction to differential thermal analysis (TG-DTA). Phase formation behavior and the morphological features of the synthesized particles are studied using X-ray diffraction and electron microscopy techniques. The sizes of the anatase phase particles are found in the range of 12–20 nm. - Highlights: • Nanosized colloidal TiO{sub 2} is prepared by controlled hydrolysis of Ti-isopropoxide. • Effect of chelating and dispersing agent on stability of colloidal TiO{sub 2} is studied. • Phase, morphology and stability of colloidal TiO{sub 2} are investigated. • The sizes of synthesized TiO{sub 2} particles are found in the range of 12–20 nm. • Suitable chelating and dispersing agent can improve particle loading in sol.

  11. Tailoring activated carbon by surface chemical modification with O, S, and N containing molecules

    Directory of Open Access Journals (Sweden)

    Rachel RibeiroVieira Azzi Rios

    2003-06-01

    Full Text Available In this work the surface of activated carbon was chemically modified in order to introduce O, S and N containing groups. The activated carbon surface was selectively oxidized with concentrated HNO3 under controlled conditions. Characterization by thermogravimetric analyses, infrared spectroscopy and NaOH titration suggested the formation of mainly -COOH and small amounts of -OH groups, with concentration of approximately 4.10(21 groups/g of carbon. These -COOH functionalized carbons showed high adsorption capacity for metal cations in aqueous solution in the following order: Pb+2>Cu+2>Ni+2 >Cd+2~Co+2>Ca+2 , suggesting a cation exchange mechanism via a surface complex [COO-M+2]. These -COOHsurf groups can be reacted with SOCl2 to produce a surface acylchloride group, -COCl. This surface -COCl group proved to be a very reactive and versatile intermediate for the grafting of different S and N containing molecules onto the carbon surface, such as 1,2-ethaneditiol (EDT-, HSCH2CH2SH 1,7-dimercapto-4-thioheptane (DMTH-HSCH2CH2CH2SCH2CH 2CH2SH or 1,2-ethylenediamine (EDA- NH2CH2CH2NH2 and triethyltetraamine, TEA (H2NCH2CH2NHCH2CH 2NHCH2CH2 NH2. The characterization of these materials was carried out by TG, IR and TPDMS (Temperature Programmed Decomposition Mass Spectrometry experiments suggesting the formation of thioesther and amide surface groups, i.e. -COSR and -CONHR, with yields of approximately 50 and 75% for the reaction with DME and EDA, respectively. Preliminary adsorption experiments showed that these materials can efficiently remove metals such as Pb+2, Cu+2 and Ni+2 from aqueous medium.

  12. Critical role of surface chemical modifications induced by length shortening on multi-walled carbon nanotubes-induced toxicity

    Directory of Open Access Journals (Sweden)

    Bussy Cyrill

    2012-11-01

    Full Text Available Abstract Given the increasing use of carbon nanotubes (CNT in composite materials and their possible expansion to new areas such as nanomedicine which will both lead to higher human exposure, a better understanding of their potential to cause adverse effects on human health is needed. Like other nanomaterials, the biological reactivity and toxicity of CNT were shown to depend on various physicochemical characteristics, and length has been suggested to play a critical role. We therefore designed a comprehensive study that aimed at comparing the effects on murine macrophages of two samples of multi-walled CNT (MWCNT specifically synthesized following a similar production process (aerosol-assisted CVD, and used a soft ultrasonic treatment in water to modify the length of one of them. We showed that modification of the length of MWCNT leads, unavoidably, to accompanying structural (i.e. defects and chemical (i.e. oxidation modifications that affect both surface and residual catalyst iron nanoparticle content of CNT. The biological response of murine macrophages to the two different MWCNT samples was evaluated in terms of cell viability, pro-inflammatory cytokines secretion and oxidative stress. We showed that structural defects and oxidation both induced by the length reduction process are at least as responsible as the length reduction itself for the enhanced pro-inflammatory and pro-oxidative response observed with short (oxidized compared to long (pristine MWCNT. In conclusion, our results stress that surface properties should be considered, alongside the length, as essential parameters in CNT-induced inflammation, especially when dealing with a safe design of CNT, for application in nanomedicine for example.

  13. Effects of intra-abdominal pressure on liver function assessed with the LiMON in critically ill patients.

    Science.gov (United States)

    Inal, Mehmet Turan; Memis, Dilek; Sezer, Y Atakan; Atalay, Meltem; Karakoc, Abdullah; Sut, Necdet

    2011-06-01

    Intra-abdominal pressure (IAP) and intra-abdominal hypertension (IAH) are associated with significant morbidity and mortality in critically ill patients. Our aim was to assess the effects of IAH on liver function using the noninvasive liver function monitoring system LiMON and to assess the prognostic value of IAP in critically ill patients. We conducted a retrospective analysis of critically ill patients who were treated in the intensive care unit (ICU). The IAP and indocyanine green plasma disappearance rate (ICG-PDR) measurements were made within 24 hours after admission to the ICU and repeated 12 hours later. Intra-abdominal pressure was measured via a Foley bladder catheter, and ICG elimination tests were conducted concurrently using the LiMON. We included 30 critically ill patients (17 women and 13 men aged 28-89 yr) in our analysis. Statistical analysis showed that the baseline IAP values were significantly higher among nonsurvivors than survivors (19.38 [standard deviation; SD 2.08] v. 13.07 [SD 0.99]). The twelfth-hour IAP values were higher than baseline measurements among nonsurvivors (21.50 [SD 1.96]) and lower than baseline measurements among survivors (11.71 [SD 1.54]); the difference between groups was significant (p LiMON is a good predictor of the effects of IAP on liver function and, thus, can be recommended for the evaluation of critically ill patients.

  14. Closely-related Xanthomonas citri subsp. citri isolates trigger distinct histological and transcriptional responses in Citrus limon

    Directory of Open Access Journals (Sweden)

    Ingrid Georgina Orce

    Full Text Available ABSTRACT Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc, has an important economic impact on the citrus industry. Extensive information is available about the disease but, nevertheless, the study of plant-pathogen interactions could provide new information in the understanding of citrus canker disease. A new isolate has been identified, Xcc AT, which has a high genetic similarity (> 90 % to the virulent Xcc T strain based on genetic clustering analyses of the rep-PCR fingerprinting patterns, but it does not produce cankerous lesions in Citrus limon. In this study, we compared C. limon responses to Xcc AT and to the virulent Xcc T strain at both histological and transcriptional levels. Histologically, leaves inoculated with Xcc AT exhibited neither a typical disordering of the spongy mesophyll, nor a swelling of epidermis. A particular content (undetermined was also found in mesophyll cells near the stomata, together with increased starch accumulation. The transcriptomic profiles were compared by cDNA-AFLP technique. A total of 121 fragments derived from transcript (TDF were either specifically induced or repressed by the isolates, and 62 were sequenced. Analysis of global expression identified different classes of genes known to be involved in plant-pathogen interactions. This study constitutes the first approach of the specific interaction between the avirulent Xcc AT isolate and C. limon.

  15. The Cytotoxic Effect of Essential Oil of Syrian Citrus limon Peel on Human Colorectal Carcinoma Cell Line (Lim1863

    Directory of Open Access Journals (Sweden)

    Mohammad Eyad Chatty

    2012-01-01

    Full Text Available Background: Essential oils are the volatile fraction of aromatic and medicinal plants created after extraction by steam or water distillation. Species of the genus Citrus(Rutaceae have been widely used in traditional medicine as volatile oils and are currently the subject of numerous research. Citrus essential oil consists of different terpens that have antitumor activities. This study determines the cytotoxic effect of the essential oils of Citrus limon L. peels on a colorectal cancer cell line (LIM1863.Methods: We harvested four samples from four locations in Syria. Essential oils were prepared by hydrodistillation and analyzed by Gas chromatography-mass spectrometry (GC-MS.Various concentrations ofessential oils (0.5-48 μg/ml were added to cultured cells and incubated for 72 h. Cell viability was evaluated byMTT-basedcytotoxicity assay.Results: We noted 18 components that represented 98.81% of the total oil content. The major components were: limonene (61.8%-73.8%, γ-terpinene (9.4%-10.4%, β-pinene (3.7%-6.9%, O-cymene(1%-2.4%,and citral (0.8%-5.4%.The obtained IC50 value range of Citrus limon essential oils was 5.75-7.92 μg/ml against LIM1863.Conclusion: This study revealed that Syrian Citrus limon essential oil has a cytotoxic effect on the human colorectalcarcinoma cell line LIM1863 when studied in vitro.

  16. Modifications in the chemical compounds and sensorial attributes of Engraulis anchoita fillet during marinating process

    Directory of Open Access Journals (Sweden)

    Maria Isabel Yeannes

    2008-12-01

    Full Text Available Marinated fish are fish products preserved by the combined action of salt and organic acids. The objective of this work was to analyze the variations in the chemical compounds of anchovy fillets that give them sensorial characteristics during the marinating process of Engraulis anchoita. The protein content decreased slightly and the TVB-N level decreased significantly in both the brining and marinating stages. In the marinating stage an increase in the total free aminoacids was observed. The NBV level in the brining and marinating solutions increased during these stages due to the solubilization of the non-protein nitrogenous compounds and the degradation of some protein compounds.The decrease of the contents of protein and TVB-N, and the increase of the acidity and the free aminoacids content during the marinating process give the marinated fillets the characteristic texture and aroma.Peixes marinados são produtos obtidos pela ação combinada de sal e ácidos orgânicos. O presente estudo teve como objetivo avaliar as alterações químicas e sensoriais em filés de anchoita (Engraulis anchoita durante o processo de marinado. O conteúdo de proteína apresentou decréscimo significativo durante a salga. O teor de Bases Voláteis Totais-N-BVT, apresentou uma diminuição considerável durante a salga e marinacão. Na fase de marinado, foi observado um aumento em aminoácidos livres totais. Foi constatada a presença de N-BVT na salmoura e na solução oriunda do processo de obtenção de marinado, devido à solubilização de nitrogênio não protéico, que podem ter sido acrescidos de alguns compostos de degradação protéica. A redução do conteúdo de proteína e N-BVT e o aumento de acidez e de aminoácidos livres gerados durante ou processo de elaboração do marinado fazem com que os filés marinados adquiram textura e aroma característicos.

  17. Chemical surface modification of calcium carbonate particles with stearic acid using different treating methods

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Zhi [Materials Research Institute, Athlone Institute of Technology, Athlone (Ireland); Daly, Michael [Mergon International, Castlepollard, Westmeath (Ireland); Clémence, Lopez [Polytech Grenoble, Grenoble (France); Geever, Luke M.; Major, Ian; Higginbotham, Clement L. [Materials Research Institute, Athlone Institute of Technology, Athlone (Ireland); Devine, Declan M., E-mail: ddevine@ait.ie [Materials Research Institute, Athlone Institute of Technology, Athlone (Ireland)

    2016-08-15

    strength than the composites containing untreated and “dry” treated CaCO{sub 3}. This is mainly because the “wet” and “complex” treatment processes have increased adsorption density of stearate, which enhances the interfacial interaction between matrix and filler. These results confirm that the chemical adsorption of the surfactant ions at the solid-liquid interface is higher than at other interface. From this study, it was concluded that the utilization of the “complex” method minimised the negative effects of void coalescence provides key information for the improvement of existing processes.

  18. Composição química e atividade anticolinesterásica de uma fração ativa do extrato de folhas de Citrus limon (L. Burm

    Directory of Open Access Journals (Sweden)

    Rusbene Bruno Fonseca de Carvalho

    2013-01-01

    Full Text Available This paper describes the chemical composition and acetylcholinesterase inhibition of an active chromatographic fraction of the EtOAc extract of Citrus limon leaves. The composition of the active fraction presented a mixture of two coumarins, 5,8-dimethoxy-psoralen and 5,7- dimethoxycoumarin, identified by ¹H and ¹³C NMR data analysis, including DEPT, COSY, HMBC and HSQC experiments. It was also demonstrated that this mixture presents qualitative and quantitative AChE inhibition. In vitro studies indicated a CE50 value of 340 µg/mL with 95% of confidence. In vivo studies (10 and 25 mg/kg revealed inhibition of 30.09 and 30.06% of AChE activity in relation to neostigmine, respectively.

  19. Cellular uptake and cytotoxic potential of respirable bentonite particles with different quartz contents and chemical modifications in human lung fibroblasts

    Energy Technology Data Exchange (ETDEWEB)

    Geh, Stefan; Rettenmeier, Albert W.; Dopp, Elke [University Hospital, Institute of Hygiene and Occupational Medicine, Essen (Germany); Yuecel, Raif [University Hospital, Institute of Cell Biology (Cancer Research), Essen (Germany); Duffin, Rodger [Institute of Environmental Health Research (IUF), Duesseldorf (Germany); University of Edinburgh, ELEGI COLT Lab, Scotland (United Kingdom); Albrecht, Catrin; Borm, Paul J.A. [Institute of Environmental Health Research (IUF), Duesseldorf (Germany); Armbruster, Lorenz [Verein fuer Technische Sicherheit und Umweltschutz e.V., Gotha (Germany); Raulf-Heimsoth, Monika; Bruening, Thomas [Research Institute for Occupational Medicine of the Institutions for Statutory Accident Insurance and Prevention (BGFA), Bochum (Germany); Hoffmann, Eik [University of Rostock, Institute of Biology, Department of Cell Biology and Biosystems Technology, Rostock (Germany)

    2006-02-01

    Considering the biological reactivity of pure quartz in lung cells, there is a strong interest to clarify the cellular effects of respirable siliceous dusts, like bentonites. In the present study, we investigated the cellular uptake and the cytotoxic potential of bentonite particles (Oe< 10 {mu}m) with an {alpha}-quartz content of up to 6% and different chemical modifications (activation: alkaline, acidic, organic) in human lung fibroblasts (IMR90). Additionally, the ability of the particles to induce apoptosis in IMR90-cells and the hemolytic activity was tested. All bentonite samples were tested for endotoxins with the in vitro-Pyrogen test and were found to be negative. Cellular uptake of particles by IMR90-cells was studied by transmission electron microscopy (TEM). Cytotoxicity was analyzed in IMR90-cells by determination of viable cells using flow cytometry and by measuring of the cell respiratory activity. Induced apoptotic cells were detected by AnnexinV/Propidiumiodide-staining and gel electrophoresis. Our results demonstrate that activated bentonite particles are better taken up by IMR90-cells than untreated (native) bentonite particles. Also, activated bentonite particles with a quartz content of 5-6% were more cytotoxic than untreated bentonites or bentonites with a quartz content lower than 4%. The bentonite samples induced necrotic as well as apoptotic cell death. In general, bentonites showed a high membrane-damaging potential shown as hemolytic activity in human erythrocytes. We conclude that cellular effects of bentonite particles in human lung cells are enhanced after chemical treatment of the particles. The cytotoxic potential of the different bentonites is primarily characterized by a strong lysis of the cell membrane. (orig.)

  20. Shifting Phases for Patchy Particles - Effect of mutagenesis and chemical modification on the phase diagram of human gamma D crystallin

    Science.gov (United States)

    McManus, Jennifer J.; James, Susan; McNamara, Ruth; Quinn, Michelle

    2014-03-01

    Single mutations in human gamma D crystallin (HGD), a protein found in the eye lens are associated with several childhood cataracts. Phase diagrams for several of these protein mutants have been measured and reveal that phase boundaries are shifted compared with the native protein, leading to condensation of protein in a physiologically relevant regime. Using HGD as a model protein, we have constructed phase diagrams for double mutants of the protein, incorporating two single amino acid substitutions for which phase diagrams are already known. In doing so, the characteristics of each of the single mutations are maintained but both are now present in the same protein particle. While these proteins are not of interest physiologically, this strategy allows the controlled synthesis of nano-scale patchy particles in which features associated with a known phase behavior can be included. It can also provide a strategy for the controlled crystallisation of proteins. Phase boundaries also change after the chemical modification of the protein, through the covalent attachment of fluorescent labels, for example, and this will also be discussed. The authors acknowledge Science Foundation Ireland Stokes Lectureship and Grant 11/RFP.1/PHY/3165. The authors also acknowledge the Irish Research Council and the John and Pat Hume Scholarship.

  1. Structural features of the pore formed by Staphylococcus aureus alpha-toxin inferred from chemical modification and primary structure analysis.

    Science.gov (United States)

    Menestrina, G; Belmonte, G; Parisi, V; Morante, S

    1992-09-01

    Staphylococcus aureus alpha-toxin makes cells and model membranes permeable to ions and uncharged molecules by opening oligomeric pores of uniform size. Its primary sequence reveals peculiar features which give some hints on the structure of the pore. A flexible region separating the toxin into two halves, several amphiphilic beta-strands and two amphiphilic alpha-helices long enough to span the hydrophobic core of the lipid bilayer are predicted. In analogy to bacterial porins, we propose that the inner walls of the pore are, at least in part, built by an amphiphilic beta-barrel. The model is consistent with circular dichroism data and with the electrophysiological properties of the pore. Functional information on this toxin were obtained by chemical modification of its four histidine residues. Specific carbethoxylation suggested they have different roles: one is required for specific receptor binding, one for oligomerisation and two for unspecific lipid binding. A tentative assignment of each histidine to its specific role is done on the basis of the structural predictions. A functionally related hemolysin, Aeromonas hydrophyla aerolysin, reveals remarkably similar features including the presence and location of histidines involved in receptor binding and oligomerisation.

  2. SMA chemical modification for application as diesel oil additive; Modificacao quimica do SMA visando aplicacao como aditivo para oleo diesel

    Energy Technology Data Exchange (ETDEWEB)

    Soldi, Rafael A.; Oliveira, Angelo R.S.; Zawadzki, Sonia F.; Cesar-Oliveira, Maria Aparecida F. [Parana Univ., Curitiba, PR (Brazil). Dept. de Quimica. Lab. de Polimeros Sinteticos]. E-mails: rafaelsoldi@hotmail.com, mafco@quimica.ufpr.br

    2003-07-01

    The deposition of paraffinic material during the crude oil and their derivatives production and transportation is one of the principal problems in the petroleum industry. Polymer derivatives obtained from styrene-maleic anhydride copolymers (SMA), containing long pendant hydrocarbon segments in the polymeric backbone, are known as efficient polymeric additives to prevent the wax deposition and to reduce the oil pour point. Nevertheless, this application for this class of polymer is not much evaluated in Brazil. In this work, a new procedure was developed for SMA synthesis and chemical modification using stearyl alcohol. The performance of these polymeric materials as pour point depressants were evaluated using a Brazilian diesel oil from REPAR/PETROBRAS. The best results were obtained for the polymeric additives with small amounts of octadecyl ester groups. When it was used only 25 ppm of one of these additives, the oil presented a pour point value of -17 deg C and the diesel oil containing 100 ppm of this same additive presented a pour point value of -30 deg C. This last result indicates a 24 deg C pour point decreasing. (author)

  3. Surface chemical modification of TEOS based silica aerogels synthesized by two step (acid-base) sol-gel process

    Energy Technology Data Exchange (ETDEWEB)

    Bhagat, Sharad D. [Air Glass Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004, Maharashtra (India); Rao, A. Venkateswara [Air Glass Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004, Maharashtra (India)]. E-mail: avrao_phy@unishivaji.ac.in

    2006-04-15

    The present paper describes the comparative studies on the hydrophobic and physical properties of the tetraethoxysilane (TEOS) based silica aerogels prepared by two step sol-gel process followed by supercritical drying. Silica alcogels were prepared by keeping the molar ratio of TEOS:methanol (MeOH):H{sub 2}O (acidic):H{sub 2}O (basic) constant at 1:33:3.5:3.5 with oxalic acid and ammonium hydroxide concentrations fixed at 0.001 and 1 M, respectively. In all, nine different co-precursors (CP) of the type R {sub n}SiX{sub 4-n}, have been used. The aerogels have been characterized by density, porosity, percentage of volume shrinkage, optical transmission, contact angle and thermal conductivity measurements. The surface chemical modification of silica aerogels was confirmed by the presence of C-H and Si-C peaks at 2900, 1450 and 840 cm{sup -1}, respectively, from the Fourier transform-infrared spectroscopy (FT-IR). The microstructure of the aerogels was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. In addition to these studies, the stability of the hydrophobic aerogels against an organic impurity (methanol, in the present studies) in water has also been studied.

  4. Surface chemical modification of TEOS based silica aerogels synthesized by two step (acid base) sol gel process

    Science.gov (United States)

    Bhagat, Sharad D.; Rao, A. Venkateswara

    2006-04-01

    The present paper describes the comparative studies on the hydrophobic and physical properties of the tetraethoxysilane (TEOS) based silica aerogels prepared by two step sol-gel process followed by supercritical drying. Silica alcogels were prepared by keeping the molar ratio of TEOS:methanol (MeOH):H 2O (acidic):H 2O (basic) constant at 1:33:3.5:3.5 with oxalic acid and ammonium hydroxide concentrations fixed at 0.001 and 1 M, respectively. In all, nine different co-precursors (CP) of the type R nSiX 4 - n, have been used. The aerogels have been characterized by density, porosity, percentage of volume shrinkage, optical transmission, contact angle and thermal conductivity measurements. The surface chemical modification of silica aerogels was confirmed by the presence of C sbnd H and Si sbnd C peaks at 2900, 1450 and 840 cm -1, respectively, from the Fourier transform-infrared spectroscopy (FT-IR). The microstructure of the aerogels was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. In addition to these studies, the stability of the hydrophobic aerogels against an organic impurity (methanol, in the present studies) in water has also been studied.

  5. Chemical modification of magnetite nanoparticles and preparation of acrylic-base magnetic nanocomposite particles via miniemulsion polymerization

    Science.gov (United States)

    Mahdieh, Athar; Mahdavian, Ali Reza; Salehi-Mobarakeh, Hamid

    2017-03-01

    Nowadays, magnetic nanocomposite particles have attracted many interests because of their versatile applications. A new method for chemical modification of Fe3O4 nanoparticles with polymerizable groups is presented here. After synthesis of Fe3O4 nanoparticles by co-precipitation method, they were modified sequentially with 3-aminopropyl triethoxysilane (APTES), acryloyl chloride (AC) and benzoyl chloride (BC) and all were characterized by FTIR, XRD, SEM and TGA analyses. Then the modified magnetite nanoparticles with unsaturated acrylic groups were copolymerized with methyl methacrylate (MMA), butyl acrylate (BA) and acrylic acid (AA) through miniemulsion polymerization. Although several reports exist on preparation of magnetite-base polymer particles, but the efficiency of magnetite encapsulationwith reasonable content and obtaining final stable latexes with limited aggregation ofFe3O4 are still important issues. These were considered here by controlling reaction parameters. Hence, a seriesofmagneticnanocomposites latex particlescontaining different amounts of Fe3O4 nanoparticles (0-10 wt%) were prepared with core-shell morphology and diameter below 200 nm and were characterized by FT-IR, DSC and TGA analyses. Their morphology and size distribution were studied by SEM, TEM and DLS analyses too. Magnetic properties of all products were also measuredby VSM analysis and the results revealed almost superparamagnetic properties for the obtained nanocomposite particles.

  6. Acid-induced structural modifications of unsaturated Fatty acids and phenolic olive oil constituents by nitrite ions: a chemical assessment.

    Science.gov (United States)

    Napolitano, Alessandra; Panzella, Lucia; Savarese, Maria; Sacchi, Raffaele; Giudicianni, Italo; Paolillo, Livio; d'Ischia, Marco

    2004-10-01

    The structural modifications of the unsaturated fatty acid components of triglycerides in extra virgin olive oil (EVOO) following exposure to nitrite ions in acidic media were determined by two-dimensional (2D) NMR spectroscopy, aided by (15)N labeling and GC analysis, allowing investigation of the matrix without fractionation steps. In the presence of excess nitrite ions in a 1% sulfuric acid/oil biphasic system, extensive double bond isomerization of the oleic/linoleic acid components of triglycerides was observed associated with nitration/oxidation processes. Structurally modified species were identified as E/Z-nitroalkene, 1,2-nitrohydroxy, and 3-nitro-1-alkene(1,5-diene) derivatives based on (1)H, (13)C, and (15)N 2D NMR analysis in comparison with model compounds. Minor constituents of EVOO, including phenolic compounds and tocopherols, were also substantially modified by nitrite-derived nitrating species, even under milder reaction conditions relevant to those occurring in the gastric compartments. Novel nitrated derivatives of tyrosol, hydroxytyrosol, and oleuropein (6-8) were identified by LC/MS analysis of the polar fraction of EVOO and by comparison with synthetic samples. Overall, these results provide the first systematic description at the chemical level of the consequences of exposing EVOO to nitrite ions at acidic pH and offer an improved basis for further investigations in the field of toxic nitrosation/nitration reactions and dietary antinitrosating agents.

  7. Preparation of conversion coating on Ti-6Al-4V alloy in mixed solution of phytic acid and ammonium fluoride through chemical modification

    Science.gov (United States)

    Li, Lanlan; He, Jian; Yang, Xu

    2016-05-01

    Conversion coatings on Ti-6Al-4V alloy was prepared through chemical modification in phytic acid and ammonium fluoride mixed solution. The influences of pH, time and the composition of solution on the microstructure of alloy surface were investigated. Scanning electron microscopy was used to observe the microstructure. The chemical composition of alloy surface before and after modification was investigated by energy dispersive X-ray spectroscopy. The results indicated that a conversion coating could be formed on the Ti-6Al-4V alloy in a mixed solution of phytic acid and ammonium fluoride, the growth and microstructure of the conversion coatings were critically dependent on the pH, time and concentration of phytic acid and ammonium fluoride. In 100 mg/ml phytic acid containing 125 mg/ml ammonium fluoride solution with a pH of 6, a compact conversion coating with the thickness of about 4.7 μm formed after 30 min immersion on Ti-6Al-4V alloy surface. The preliminary evaluation of bioactivity of conversion coating was performed by in vitro cell experiments. The results showed that this chemical modification method is a promising surface modification technique for Ti-6Al-4V alloy inplants.

  8. Chemical modification of Penicillium 1,2-alpha-D-mannosidase by water-soluble carbodi-imide: identification of a catalytically important aspartic acid residue.

    Science.gov (United States)

    Yoshida, T; Maeda, K; Kobayashi, M; Ichishima, E

    1994-01-01

    1,2-alpha-D-Mannosidase from Penicillium citrinum was inactivated by chemical modification with 1-ethyl-3-(3-dimethylamino-propyl)carbodi-imide (EDC). Most of the activity was lost after modification in the absence of a nucleophile, glycine ethyl ester. 1-Deoxymannojirimycin (dMM), a competitive inhibitor of the enzyme, showed partial protection against the inactivation. After the modification by EDC without the presence of a nucleophile, proteolytic digests of the enzyme were analysed by reversed-phase h.p.l.c. and a unique peptide was shown to decrease when dMM was present during the modification. The peptide was absent from the digests of unmodified enzyme. The amino acid sequence of the peptide (A; Ile-Gly-Pro) was identical in part with that of the adjacent peptide (B; Ile-Gly-Pro-Asp-Ser-Trp-Gly-Trp-Asp-Pro-Lys). When cholecystokinin tetrapeptide (Trp-Met-Asp-Phe-NH2) was modified by EDC alone, the modified peptide could be separated from unmodified peptide by reversed-phase h.p.i.c., and Edman degradation was stopped before the modified aspartic acid residue. This suggested that, in the enzyme, peptide A was derived from peptide B by the modification. Consequently, Asp-4 in peptide B was assumed to be masked by dMM during the modification, and to be involved in the interaction of the enzyme with its substrate. PMID:7945271

  9. Deficiency in the LIM-only protein Fhl2 impairs skin wound healing.

    Science.gov (United States)

    Wixler, Viktor; Hirner, Stephanie; Müller, Judith M; Gullotti, Lucia; Will, Carola; Kirfel, Jutta; Günther, Thomas; Schneider, Holm; Bosserhoff, Anja; Schorle, Hubert; Park, Jung; Schüle, Roland; Buettner, Reinhard

    2007-04-09

    After skin wounding, the repair process is initiated by the release of growth factors, cytokines, and bioactive lipids from injured vessels and coagulated platelets. These signal molecules induce synthesis and deposition of a provisional extracellular matrix, as well as fibroblast invasion into and contraction of the wounded area. We previously showed that sphingosine-1-phosphate (S1P) triggers a signal transduction cascade mediating nuclear translocation of the LIM-only protein Fhl2 in response to activation of the RhoA GTPase (Muller, J.M., U. Isele, E. Metzger, A. Rempel, M. Moser, A. Pscherer, T. Breyer, C. Holubarsch, R. Buettner, and R. Schule. 2000. EMBO J. 19:359-369; Muller, J.M., E. Metzger, H. Greschik, A.K. Bosserhoff, L. Mercep, R. Buettner, and R. Schule. 2002. EMBO J. 21:736-748.). We demonstrate impaired cutaneous wound healing in Fhl2-deficient mice rescued by transgenic expression of Fhl2. Furthermore, collagen contraction and cell migration are severely impaired in Fhl2-deficient cells. Consequently, we show that the expression of alpha-smooth muscle actin, which is regulated by Fhl2, is reduced and delayed in wounds of Fhl2-deficient mice and that the expression of p130Cas, which is essential for cell migration, is reduced in Fhl2-deficient cells. In summary, our data demonstrate a function of Fhl2 as a lipid-triggered signaling molecule in mesenchymal cells regulating their migration and contraction during cutaneous wound healing.

  10. Anxiolytic-like effect of Citrus limon (L. Burm f. essential oil inhalation on mice

    Directory of Open Access Journals (Sweden)

    M.D.M. VIANA

    2016-03-01

    Full Text Available ABSTRACT Experimental in vivo study aimed to characterize the anxiolytic-like effect of the Citrus limon fruit peel’s essential oil (CLEO in animal models of anxiety, besides evaluating the viability J774.A1 cells in vitro through the MTT reduction method at the concentrations of 10 and 100 µg/mL. The anxiolytic behavior was evaluated in Swiss mice (n = 8 using the methodology of Elevated Plus-Maze (EPM and Open-Field (OF. CLEO was tested by inhalation at the doses of 100, 200, and 400 µL, and as control, animals were subjected to inhalation of the vehicle (saline solution 0.9% + Tween80® and intraperitoneal administration of diazepam (1.5 mg/kg. In the cell viability assay, it was observed that none of the concentrations showed cytotoxicity. OF test showed significant anxiolytic activity at all tested doses of OECL, compared to the control group, without changing the motor performance of the animals. Corroborating OF data, the EPM test confirmed anxiolytic activity in at least two doses of the tested oil (200 and 400 µL, justified by the number of entries and increase in the percentage of time in the open arms. The data analysis of this study evidenced that inhalation of OECL was able to induce an anxiolytic behavior in mice; however, further studies are required to ensure its safe use by the population.

  11. Citrus limon extract: possible inhibitory mechanisms affecting testicular functions and fertility in male mice.

    Science.gov (United States)

    Singh, Nidhi; Singh, Shio Kumar

    2016-01-01

    The effect of oral administration of 50% ethanolic leaf extract of Citrus limon (500 and 1,000 mg/kg body weight/day) for 35 days on fertility and various male reproductive endpoints was evaluated in Parkes strain of mice. Testicular indices such as histology, 3β- and 17β-HSD enzymes activity, immunoblot expression of StAR and P450scc, and germ cell apoptosis by TUNEL and CASP- 3 expression were assessed. Motility, viability, and number of spermatozoa in the cauda epididymidis, level of serum testosterone, fertility indices, and toxicological parameters were also evaluated. Histologically, testes in extract-treated mice showed nonuniform degenerative changes in the seminiferous tubules. Treatment had adverse effects on steroidogenic markers in the testis and induced germ cell apoptosis. Significant reductions were noted in epididymal sperm parameters and serum level of testosterone in Citrus-treated mice compared to controls. Fertility of the extract-treated males was also suppressed, but libido remained unaffected. By 56 days of treatment withdrawal, alterations induced in the above parameters returned to control levels suggesting that Citrus treatment causes reversible suppression of spermatogenesis and fertility in Parkes mice. Suppression of spermatogenesis may result from germ cell apoptosis because of decreased production of testosterone. The present work indicated that Citrus leaves can affect male reproduction.

  12. Modification of asphaltic concrete with a mineral polymeric additive based on butadiene-styrene rubber and chemically precipitated calcium carbonate

    Directory of Open Access Journals (Sweden)

    S. I. Niftaliev

    2016-01-01

    Full Text Available Modification of asphaltic concrete with a mineral polymeric additive based on butadiene – styrene rubber and chemically precipitated calcium carbonate. This paper presents the results of the study of physical – mechanical and service properties of the asphaltic concrete modified with the mineral polymeric composition. Calcium carbonate is used both as a filler and a coagulant. The chalk was preliminarily ground and hydrophobizated by stearic acid. These operations contribute to even distribution of the filler and interfere with lump coagulation. As a result of the experiments, it was found that the best results were obtained by combining the operations of dispersion and hydrophobization. The optimal amount of stearic acid providing the finest grinding in a ball mill is a content from 3 to 5% by weight. The optimal grinding time of the filler was found (4–6 hours. With increasing dispersion time the particles form agglomerates. Filling the butadiene styrene latex with the hydrophobic fine-grained calcium carbonate was carried out in the laboratory mixer. As a result of the experimental works, it was found that the best distribution of the filler takes place with ratio of rubber: chalk – 100:400. The resulting modifier was subjected to the thermal analysis on the derivatograph to determine its application temperature interval. A marked reduction in weight of the mineral polymeric modifier begins at 350 °C. Thus, high temperature of the modifier destruction allows to use it at the temperature of the technological process of asphaltic concrete preparation (up to 170 °C. It was found that an increase in the amount of the carbonate filler in the rubber SKS 30АRК significantly increases its thermal resistance and connection of the polymer with the chalk in the composition.

  13. Chemical modification of poly(vinyl alcohol): evaluation of hydrophilic/lipophilic balance; Poli(alcool vinilico) modificado com cadeias hidrocarbonicas: avaliacao do balanco hidrofilo/lipofilo

    Energy Technology Data Exchange (ETDEWEB)

    Aranha, Isabele B.; Lucas, Elizabete F. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Macromoleculas Eloisa B. Mano]. E-mail: elucas@ima.ufrj.br

    2001-12-01

    Poly(vinyl alcohol) terpolymers have been obtained by reaction of partially hydrolized poly(vinyl alcohol) with different acid chlorides. The objective is the preparation of polymers with slight differences in their hydrophilic/lipophilic balance and in the interfacial activities of their solutions. The chemical modifications were characterized by means of {sup 1}H NMR and the polymer properties were evaluated in terms of changes in solubility and surface tension. By chemical modification, polymers with low percentage of hydrophobic group were obtained. The water-soluble polymers obtained did not have the surface tension of their solutions altered. The solubility of the modified polymers decreased markedly, even with low contents of hydrophobic groups. (author)

  14. Green synthesis of gold nanoparticles using Citrus fruits (Citrus limon, Citrus reticulata and Citrus sinensis) aqueous extract and its characterization.

    Science.gov (United States)

    Sujitha, Mohanan V; Kannan, Soundarapandian

    2013-02-01

    This study reports the biological synthesis of gold nanoparticles by the reduction of HAuCl(4) by using citrus fruits (Citrus limon, Citrus reticulata and Citrus sinensis) juice extract as the reducing and stabilizing agent. A various shape and size of gold nanoparticles were formed when the ratio of the reactants were altered with respect to 1.0mM chloroauric acid solution. The gold nanoparticles obtained were characterized by UV-visible spectra, transmission electron microscopy (TEM) and X-ray diffraction (XRD). TEM studies showed the particles to be of various shapes and sizes and particle size ranges from 15 to 80 nm. Selected-area electron diffraction (SAED) pattern confirmed fcc phase and crystallinity of the particles. The X-ray diffraction analysis revealed the distinctive facets (111, 200, 220 and 222 planes) of gold nanoparticles. Dynamic light scattering (DLS) studies revealed that the average size for colloid gp(3) of C. limon, C. reticulata and C. sinensis are 32.2 nm, 43.4 nm and 56.7 nm respectively. The DLS graph showed that the particles size was larger and more polydispersed compared to the one observed by TEM due to the fact that the measured size also includes the bio-organic compounds enveloping the core of the Au NPs. Zeta potential value for gold nanoparticles obtained from colloid gp(3) of C. limon, C. reticulata and C. sinensis are -45.9, -37.9 and -31.4 respectively indicating the stability of the synthesized nanoparticles. Herein we propose a novel, previously unexploited method for the biological syntheses of polymorphic gold nanoparticles with potent biological applications.

  15. Green synthesis of gold nanoparticles using Citrus fruits (Citrus limon, Citrus reticulata and Citrus sinensis) aqueous extract and its characterization

    Science.gov (United States)

    Sujitha, Mohanan V.; Kannan, Soundarapandian

    2013-02-01

    This study reports the biological synthesis of gold nanoparticles by the reduction of HAuCl4 by using citrus fruits (Citrus limon, Citrus reticulata and Citrus sinensis) juice extract as the reducing and stabilizing agent. A various shape and size of gold nanoparticles were formed when the ratio of the reactants were altered with respect to 1.0 mM chloroauric acid solution. The gold nanoparticles obtained were characterized by UV-visible spectra, transmission electron microscopy (TEM) and X-ray diffraction (XRD). TEM studies showed the particles to be of various shapes and sizes and particle size ranges from 15 to 80 nm. Selected-area electron diffraction (SAED) pattern confirmed fcc phase and crystallinity of the particles. The X-ray diffraction analysis revealed the distinctive facets (1 1 1, 2 0 0, 2 2 0 and 2 2 2 planes) of gold nanoparticles. Dynamic light scattering (DLS) studies revealed that the average size for colloid gp3 of C. limon, C. reticulata and C. sinensis are 32.2 nm, 43.4 nm and 56.7 nm respectively. The DLS graph showed that the particles size was larger and more polydispersed compared to the one observed by TEM due to the fact that the measured size also includes the bio-organic compounds enveloping the core of the Au NPs. Zeta potential value for gold nanoparticles obtained from colloid gp3 of C. limon, C. reticulata and C. sinensis are -45.9, -37.9 and -31.4 respectively indicating the stability of the synthesized nanoparticles. Herein we propose a novel, previously unexploited method for the biological syntheses of polymorphic gold nanoparticles with potent biological applications.

  16. Theoretical and experimental spectroscopic analysis by FTIR in the effect of the silanes on the chemical modification of the surface of rice husk

    OpenAIRE

    R. Salgado-Delgado; A.M. Salgado-Delgado

    2016-01-01

    The development of new fibrous composites with specific properties has attracted a big interest in the development of new technologies. One of the biggest problems in this area is the improvement of the fiber/matrix interface to increase the mechanical properties in the final composite. In this work, surface chemical modifications of the rice husk (by-product of the rice industry) were carried out to achieve a better compatibility with diverse polymeric matrices. These modificatio...

  17. Élaboration d’une nouvelle margarine additionnée des huiles essentielles de Citrus limon

    Directory of Open Access Journals (Sweden)

    Himed Louiza

    2014-01-01

    Full Text Available Ce travail s’est concentré sur la valorisation des huiles essentielles de Citrus limon. Ces dernières ont été extraites par pression à froid et par hydrodistillation, les rendements obtenus sont équivalents, respectivement, à 1,02 % et 2,18 %. L’activité antioxydante des huiles extraites a été étudiée par le test de DPPH°, ce radical puissant a été efficacement réduit par l’HE1, par l’HE2 par comparaison au Tocoblend. Ces résultats ont été confirmés par le test de blanchissement du β-carotène. Les deux tests ont permis de classer les huiles essentielles de Citrus limon extraites parmi les antioxydants plus puissants par rapport au Tocoblend. L’essai de formulation des margarines de table additionnées d’huiles essentielles de Citrus limon a été expérimenté, en vue de les exploiter et de substituer un additif synthétique (le Tocoblend. Les caractéristiques physico-chimiques des margarines élaborées (gras, non gras et point de fusion s’avèrent conformes à la recette préétablie. En outre, l’indice de peroxyde est conforme aux normes. L’analyse des acides gras a été faite par CPG, elle a montré la richesse de nos margarines en acides gras essentiels avec un rapport AGPI/AGS de 0,85. L’évaluation de la stabilité oxydative est réalisée par les tests de Rancimat et Schaal, les résultats obtenus ont montré que les margarines à huiles essentielles de Citrus limon étaient plus résistantes que celle au Tocoblend et que la margarine à l’HE1 était la plus résistante vis-à-vis de l’oxydation forcée. La métrologie sensorielle a été faite par les assesseurs de la margarinerie de CEVITAL et indique que les margarines aux huiles essentielles obtenues sont considérées comme étant homogènes, de couleur, de saveur et d’odeur acceptables et appréciées.

  18. In vitro xanthine oxidase inhibitory activity of leaves, fruits and peel extracts of Citrus aurantium, Citrus limetta and Citrus limon

    Directory of Open Access Journals (Sweden)

    Muthiah PL

    2012-07-01

    Full Text Available Aim of the study: To evaluate the in vitro xanthine oxidase inhibitory activity of the extract of leaves, fruits and peel of Citrus aurantium, Citrus limetta and Citrus limon.   Materials and Methods: Xanthine oxidase inhibitory activity was assayed spectrophotometrically under aerobic conditions and the degree of enzyme inhibition was determined by measuring the increase in absorbance at 295nm associated with uric acid formation.   Results: Among the extracts tested, the C.limetta peel extract exhibited highest potency of xanthine oxidase inhibition (IC50 40.16±0.88μg/ml. This was followed by C.aurantium peel (IC50 51.50±2.05μg/ml, C.limon peel (IC50 64.90±1.24μg/ml, C.aurantium leaf (IC5073.50±1.26μg/ml, C.limetta leaf (IC50 74.83±2.42μg/ml, C.limon leaf (IC50 76.83±2.02μg/ml, C.limetta fruit (IC50 95.16±0.60μg/ml extracts compared with the IC50 value of standard allopurinol was 6.6μg/ml.   Conclusion: Recent findings show that the occurrence of gout is increasing worldwide, possibly due to the changes in dietary habits like intake of food rich in nucleic acids, such as meat, sea foods, etc. Xanthine oxidase inhibitors such as allopurinol is the drug of choice, however it has been observed more side effects.  An alternative to allopurinol is the use of medicinal plants, We thus began our program to look for xanthine oxidase inhibitors of phytochemical origin. In conclusion, the study suggests that the leaves and peel extracts of Citrus aurantium, Citrus limetta and Citrus limon possess xanthine oxidase inhibitory activity that might be helpful in preventing or slowing the progress of gout and related disorders.

  19. A Chemical-Adsorption Strategy to Enhance the Reaction Kinetics of Lithium-Rich Layered Cathodes via Double-Shell Surface Modification.

    Science.gov (United States)

    Guo, Lichao; Li, Jiajun; Cao, Tingting; Wang, Huayu; Zhao, Naiqin; He, Fang; Shi, Chunsheng; He, Chunnian; Liu, Enzuo

    2016-09-21

    Sluggish surface reaction kinetics hinders the power density of Li-ion battery. Thus, various surface modification techniques have been applied to enhance the electronic/ionic transfer kinetics. However, it is challenging to obtain a continuous and uniform surface modification layer on the prime particles with structure integration at the interface. Instead of classic physical-adsorption/deposition techniques, we propose a novel chemical-adsorption strategy to synthesize double-shell modified lithium-rich layered cathodes with enhanced mass transfer kinetics. On the basis of experimental measurement and first-principles calculation, MoO2S2 ions are proved to joint the layered phase via chemical bonding. Specifically, the Mo-O or Mo-S bonds can flexibly rotate to bond with the cations in the layered phase, leading to the good compatibility between the thiomolybdate adsorption layer and layered cathode. Followed by annealing treatment, the lithium-excess-spinel inner shell forms under the thiomolybdate adsorption layer and functions as favorable pathways for lithium and electron. Meanwhile, the nanothick MoO3-x(SO4)x outer shell protects the transition metal from dissolution and restrains electrolyte decomposition. The double-shell modified sample delivers an enhanced discharge capacity almost twice as much as that of the unmodified one at 1 A g(-1) after 100 cycles, demonstrating the superiority of the surface modification based on chemical adsorption.

  20. FTIR spectroscopy of cysteine as a ready-to-use method for the investigation of plasma-induced chemical modifications of macromolecules

    Science.gov (United States)

    Kogelheide, Friederike; Kartaschew, Konstantin; Strack, Martin; Baldus, Sabrina; Metzler-Nolte, Nils; Havenith, Martina; Awakowicz, Peter; Stapelmann, Katharina; Lackmann, Jan-Wilm

    2016-03-01

    A rapid screening method for the investigation of plasma-induced chemical modifications was developed by analyzing cysteine using Fourier Transform Infrared (FTIR) spectroscopy. Cysteine is a key amino acid in proteins due to the presence of a thiol group which provides unique structural features by offering the possibility to form disulfide bonds. Its chemical composition makes cysteine a well-suited model for the investigation of plasma-induced modifications at three functional groups—the amino, the carboxyl and the thiol group—all highly abundant in proteins. FTIR spectroscopy is present in most physical laboratories and offers a fast way to assess changes in the chemical composition of cysteine substrates due to plasma treatment and to compare different treatment conditions or plasma sources with each other. Significant changes in the fingerprint spectra of cysteine samples treated with a dielectric barrier discharge (DBD) compared to untreated controls were observed using a FTIR spectrometer. The loss of the thiol signal and the simultaneous increase of bands originating from oxidized sulfur and nitrogen species indicate that the thiol group of cysteine is modified by reactive oxygen and nitrogen species during DBD treatment. Furthermore, other plasma-induced modifications, such as changes of the amino and carbonyl groups, could be observed. Complementary mass spectrometry measurements confirmed these results.

  1. In vitro and in vivo effect of Citrus limon essential oil against sarcoptic mange in rabbits.

    Science.gov (United States)

    Aboelhadid, S M; Mahrous, Lilian N; Hashem, Shimaa A; Abdel-Kafy, E M; Miller, Robert J

    2016-08-01

    The effect of lemon oil (Citrus limon) on Sarcoptes scabiei var. cuniculi was evaluated in vitro and in vivo. The mite samples were collected from naturally infected rabbits. The lemon oil was prepared in six concentrations by dilution with distilled water (2.5, 5, 10, 20, 50, and 100 %). In vitro application was done in five replicates for each concentration in petri dishes in the laboratory. The treated mites were observed at 1, 12, and 24 h post application (PA) for lemon oil effect. In addition, oxidative stress profile was evaluated for the treated mite. Dependent on in vitro results, 20 % lemon oil was used in vivo trial. Twenty-four naturally infected rabbits were divided into three groups of eight: 20 % lemon oil, deltamethrin, and untreated control. The infected parts of rabbits were treated topically once a week for four successive weeks. In vitro application results showed that lemon oil 10 and 20 % diluted in water caused mortality to 100 % of mites after 24 h PA. The oxidative stress profile revealed that mites treated with 20 % lemon oil had significantly (P < 0.05) higher hydrogen peroxide and malondialdehyde when compared with mites treated with deltamethrin or distilled water. In vivo application of 20 % lemon oil on naturally infected rabbits showed complete recovery from clinical signs, absence of mite in microscopic examination from the second week of treatment. In addition, productive performance was significantly better than infected untreated group. Also, the treated tissue showed stoppage of scale formation and hair growth faster than deltamethrin-treated rabbits. Consequently, lemon oil has remarkable miticidal activity in vitro and in vivo applications.

  2. Modification of alumina matrices through chemical etching and electroless deposition of nano-Au array for amperometric sensing

    Directory of Open Access Journals (Sweden)

    Valinčius Gintaras

    2007-01-01

    Full Text Available AbstractSimple nanoporous alumina matrix modification procedure, in which the electrically highly insulating alumina barrier layer at the bottom of the pores is replaced with the conductive layer of the gold beds, was described. This modification makes possible the direct electron exchange between the underlying aluminum support and the redox species encapsulated in the alumina pores, thus, providing the generic platform for the nanoporous alumina sensors (biosensors with the direct amperometric signal readout fabrication.

  3. Increasing antibiotic activity against a multidrug-resistant Acinetobacter spp by essential oils of Citrus limon and Cinnamomum zeylanicum.

    Science.gov (United States)

    Guerra, Felipe Queiroga Sarmento; Mendes, Juliana Moura; Sousa, Janiere Pereira de; Morais-Braga, Maria F B; Santos, Bernadete Helena Cavalcante; Melo Coutinho, Henrique Douglas; Lima, Edeltrudes de Oliveira

    2012-01-01

    The genus Acinetobacter has gained importance in recent years due to involvement in serious infections and antimicrobial resistance. Many plants have been evaluated not only for direct antimicrobial activity, but also as resistance modifying agents. The Essential oil of Citrus limon (EOCL) addition at 156.25 µgmL(-1) (MIC/8) sub-inhibitory concentration in the growth medium led to MIC decrease for amikacin, imipenem and meropenem. The Essential oil of Cinnamomum zeylanicum (EOCZ) addition at 78.125 µg mL(-1) (MIC/8) sub-inhibitory concentrations in the growth medium caused drastic MIC reduction of amikacin. Results of combining antibiotics and essential oils had shown us a synergistic effect with both essential oils/amikacin combinations. An additive effect was observed with the combinations of both essential oils and gentamicin. The results of this study suggest that essential oil of C. limon and C. zeylanicum may suppress the growth of Acinetobacter species and could be a source of metabolites with antibacterial modifying activity.

  4. In vitro effect of essential oils from Cinnamomum aromaticum, Citrus limon and Allium sativum on two intestinal flagellates of poultry, Tetratrichomonas gallinarum and Histomonas meleagridis

    Directory of Open Access Journals (Sweden)

    Zenner L.

    2003-06-01

    Full Text Available Essential oils may be effective preventive or curative treatments against several flagelated poultry parasites and may become primordial either to organic farms, or as more drugs are bannished. The anti-flagellate activity of essential oils obtained from fresh leaves of Cinnamomum aromaticum, Citrus limon pericarps and Allium sativum bulbs was investigated in vitro on Tetratrichomonas gallinarum and Histomonas meleagridis. On T. gallinarum, the minimal lethal concentration (MLC at 24 hours was 0.25 μl/ml for C. aromaticum oil, and 0.125 μl/ml for C. limon and A. sativum oils. On H. meleagridis, MLC was 0.5 μl/ml for C. aromaticum oil and 1 μl/m l for C. limon and A. sativum oils at 24 and 48 hours. Moreover, no synergistic effects were evidenced in vitro. The essential oil constituents, based on their GC retention times have been also identified. The major component is trans-cinnamaldehyde (79 % for C. aromaticum; limonene for C. limon (71 % and diallyl tri- and disulfide (79 % for A. sativum. Even if concentration and protocol adaptations are required for successful in vivo treatments, it appears that these oils may be useful as chemotherapeutic agents against several poultry parasites.

  5. Chemical modification of chitosan in the absence of solvent for diclofenac sodium removal: pH and kinetics studies

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Kerlaine Alexandre Araujo; Osorio, Luizangela Reis; Silva, Marcos Pereira; Silva Filho, Edson Cavalcanti da, E-mail: edsonfilho@ufpi.edu.br [Universidade Federal do Piaui (UFPI/CCN), Teresina, PI (Brazil). Centro de Ciencias da Natureza. Lab. Interdisciplinar de Materiais Avancados; Sousa, Kaline Soares [Universidade Federal da Paraiba (UFPB/CCEN), Joao Pessoa, PB (Brazil). Centro de Ciencias Exatas e da Natureza. Dept. de Quimica

    2014-08-15

    Chitosan was modified with acetylacetone and ethylenediamine in the absence of solvent. The new biopolymer obtained from the modification was characterized by elemental analysis and NMR 13C and applied in the removal of diclofenac sodium aqueous solution varying the pH and time. Through elemental analysis was possible to verify a decreasing in C/N relation after reaction with acetylacetone and an increasing after modification with ethylenediamine. From NMR analysis was verified the appearance of peaks around 160-210 ppm in both materials due to free carbonyl groups in the first step of the modification, besides the formation of imine bonds. The adsorption tests showed that the highest value occurred at pH 4 and from the results of the kinetic study was found that maximum adsorption occurred within 45 minutes and experimental data adjusted better to linear adjustment, following pseudo second-order model. The results show a material efficient in the removal of emerging pollutants. (author)

  6. Chemical Synthesis Elucidates the Immunological Importance of a Pyruvate Modification in the Capsular Polysaccharide of Streptococcus pneumoniae Serotype 4.

    Science.gov (United States)

    Pereira, Claney L; Geissner, Andreas; Anish, Chakkumkal; Seeberger, Peter H

    2015-08-17

    Carbohydrate modifications are believed to strongly affect the immunogenicity of glycans. Capsular polysaccharides (CPS) from bacterial pathogens are frequently equipped with a pyruvate that can be placed across the 4,6-, 3,4-, or 2,3-positions. A trans-2,3-linked pyruvate is present on the CPS of the Gram-positive bacterium Streptococcus pneumoniae serotype 4 (ST4), a pathogen responsible for pneumococcal infections. To assess the immunological importance of this modification within the CPS repeating unit, the first total synthesis of the glycan was carried out. Glycan microarrays containing a series of synthetic antigens demonstrated how antibodies raised against natural ST4 CPS specifically recognize the pyruvate within the context of the tetrasaccharide repeating unit. The pyruvate modification is a key motif for designing minimal synthetic carbohydrate vaccines for ST4.

  7. Beneficial effect of Citrus limon peel aqueous methanol extract on experimentally induced urolithic rats.

    Science.gov (United States)

    Sridharan, Badrinathan; Michael, Shiju T; Arya, Ramachandran; Mohana Roopan, Selvaraj; Ganesh, Rajesh N; Viswanathan, Pragasam

    2016-01-01

    Citrus limon (L.) Burm.f. (Rutaceace) is a commonly available fruit variety with high medicinal and industrial values. Lemon peel (LP) extract was studied as a potent preventive and curative agent for experimentally induced hyperoxaluric rats. Gas chromatography-mass spectrometry (GC-MS) analyses and toxicity study were performed for aqueous methanol LP extract. Twenty-four Wistar rats were segregated into four groups. Group 1: Control; Group 2: Urolithic (ethylene glycol (EG) - 0.75%); Group 3: Preventive study (EG + LP extract administration from 0th to 7th week); Group 4: Curative study (EG + LP extract administration from 4th to 7th week). Animals received LP extract daily by oral administration (100 mg/kg body weight) for 7 weeks. GC-MS analyses revealed that compound 6 was abundant in the LP extract (32%) followed by compound 1 (∼21%). The LD50 value of LP extract was found to be >5000 mg/kg of body weight. Urolithic rats showed significantly higher urinary calcium and oxalate (4.47 ± 0.44 and 18.86 ± 0.55 mg/24 h, respectively) excretion compared with control and experimental rats. Renal function parameters like urea (84 ± 8.5 and 96.1 ± 3.6 mg/dL), creatinine (1.92 ± 0.27 and 1.52 ± 0.22 mg/dL), and urinary protein (2.03 ± 0.02 and 2.13 ± 0.16 mg/24 h) were also reduced by LP extract (p < 0.001) and corroborated with tissue analyses (SOD, catalase, and MDA levels) and histological studies in normal and experimental animals. Immunohistochemical staining of THP and NF-κB in urolithic animals showed elevated expression than the control, while LP extract suppressed the expression of these proteins. In conclusion, lemon peel is effective in curing kidney stone disease and also can be used to prevent the disease and its recurrence.

  8. 均相体系中纤维素化学改性研究概述%Progress on homogeneously chemical modification of cellulose

    Institute of Scientific and Technical Information of China (English)

    周金平; 甘蔚萍; 张俐娜

    2012-01-01

    Cellulose, as an environmentally friendly renewable resource, has received more and more attention. It has been investigated extensively by both academic and industrial researchers Because of the depletion of oil resources, the increasing pollution of the environment and the urgent need for sustainable development. Based on the unique structure and reactivity of cellulose, chemical modifications play dominant roles in improving the overall utilization of this bioresource. Cellulose derivatives have been found in numerous applications in a variety of fields, including the paper and textile, food, cosmetics, chemical, and pharmaceutical industries. Moreover, homogeneous modification of cellulose has been one focus of cellulose research for a long time. In this review, research development of chemical modification of cellulose in the homogeneously systems in the recent 10 years was summarized and 155 references were cited. Esterification, etherification and graft copolymerization of cellulose in LiCl/AyV-dimethylacetamide, dimethyl sufoxide/tertrabutylammonium fluoride, ionic liquids, and NaOH/urea aqueous solutions have been described in detail.%本文概述了近十年来纤维素在均相体系中化学改性的研究成果,重点介绍了纤维素在氯化锂/N,N-二甲基乙酰胺(LiCl/DMAc)、二甲基亚砜/三水合四丁基氟化铵(DMSO/TBAF·3H2O)、离子液体、碱/尿素体系中的均相酯化、醚化以及接枝共聚合反应.同时,总结了纤维素在这些溶剂中的反应特性及其衍生化产物的结构、性质和应用.

  9. Simple Fabrication of Gd(III)-DTPA-Nanodiamond Particles by Chemical Modification for Use as Magnetic Resonance Imaging (MRI) Contrast Agent

    Science.gov (United States)

    Nakamura, Takako; Ohana, Tsuguyori; Yabuno, Hajime; Kasai, Rumiko; Suzuki, Tetsuya; Hasebe, Terumitsu

    2013-01-01

    We have developed a simple and useful process for fabricating nanodiamond (ND) particles modified with an organogadolinium moiety by chemical modification for their use as a magnetic resonance imaging (MRI) contrast agent. The introduction of the organogadolinium moiety on the surface of the ND particles was performed by the condensation of ND and diethylenetriaminepentaacetic acid (DTPA) followed by treatment with GdCl3. The modified surfaces were evaluated by X-ray photoelectron spectroscopy, diffuse reflectance Fourier transform infrared spectroscopy, mass spectroscopy, and inductively coupled plasma atomic emission spectroscopy analyses. MRI experiments on the Gd-DTPA-ND particles indicated their high signal intensity on T1-weighted images.

  10. A post-modification approach to independent component analysis for resolution of overlapping GC/MS signals: from independent components to chemical components

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; CAI WenSheng; SHAO XueGuang

    2007-01-01

    Independent component analysis (ICA) has demonstrated its power to extract mass spectra from overlapping GC/MS signal. However, there is still a problem that mass spectra with negative peaks at some m/z will be obtained in the resolved results when there are overlapping peaks in the mass spectra of a mixture. Based on a detail theoretical analysis of the preconditions for ICA and the non-negative property of GC/MS signals, a post-modification based on chemical knowledge (PMBK) strategy is proposed to solve this problem. By both simulated and experimental GC/MS signals, it was proved that the PMBK strategy can improve the resolution effectively.

  11. Reconstituted voltage-sensitive sodium channel from Electrophorus electricus: chemical modifications that alter regulation of ion permeability.

    Science.gov (United States)

    Cooper, E C; Tomiko, S A; Agnew, W S

    1987-01-01

    At equilibrium, voltage-sensitive sodium channels normally are closed at all potentials. They open transiently in response to changes in membrane voltage or chronically under the influence of certain neurotoxins. Covalent modifications that result in chronic opening may help identify molecular domains involved in conductance regulation. Here, the purified sodium channel from electric eel electroplax, reconstituted in artificial liposomes, has been used to screen for such modifications. When the liposomes were treated with the alkaloid neurotoxin batrachotoxin, sodium-selective ion fluxes were produced, with permeability ratios PNa greater than PTl greater than PK greater than PRb greater than PCs. When the liposomes were treated with either of two oxidizing reagents (N-bromoacetamide or N-bromosuccinimide), or with Pronase or trypsin, ion-selective fluxes also were stimulated. These were blocked by tetrodotoxin and the anesthetic QX-314 in a manner suggesting that only modification of the cytoplasmic protein surface resulted in stimulation. Limited exposure to trypsin resulted in strong flux activation, with the concomitant appearance of peptide fragments with masses of approximately equal to 130, 70, and 38 kDa and fragments with masses of 45 and 24 kDa appearing later. We propose that characterization of these fragments may allow identification of channel domains important for inactivation gating. Images PMID:2442755

  12. Anti-Inflammatory Properties and Chemical Characterization of the Essential Oils of Four Citrus Species.

    Science.gov (United States)

    Amorim, Jorge Luis; Simas, Daniel Luiz Reis; Pinheiro, Mariana Martins Gomes; Moreno, Daniela Sales Alviano; Alviano, Celuta Sales; da Silva, Antonio Jorge Ribeiro; Fernandes, Patricia Dias

    2016-01-01

    Citrus fruits have potential health-promoting properties and their essential oils have long been used in several applications. Due to biological effects described to some citrus species in this study our objectives were to analyze and compare the phytochemical composition and evaluate the anti-inflammatory effect of essential oils (EO) obtained from four different Citrus species. Mice were treated with EO obtained from C. limon, C. latifolia, C. aurantifolia or C. limonia (10 to 100 mg/kg, p.o.) and their anti-inflammatory effects were evaluated in chemical induced inflammation (formalin-induced licking response) and carrageenan-induced inflammation in the subcutaneous air pouch model. A possible antinociceptive effect was evaluated in the hot plate model. Phytochemical analyses indicated the presence of geranial, limonene, γ-terpinene and others. EOs from C. limon, C. aurantifolia and C. limonia exhibited anti-inflammatory effects by reducing cell migration, cytokine production and protein extravasation induced by carrageenan. These effects were also obtained with similar amounts of pure limonene. It was also observed that C. aurantifolia induced myelotoxicity in mice. Anti-inflammatory effect of C. limon and C. limonia is probably due to their large quantities of limonene, while the myelotoxicity observed with C. aurantifolia is most likely due to the high concentration of citral. Our results indicate that these EOs from C. limon, C. aurantifolia and C. limonia have a significant anti-inflammatory effect; however, care should be taken with C. aurantifolia.

  13. Anti-Inflammatory Properties and Chemical Characterization of the Essential Oils of Four Citrus Species.

    Directory of Open Access Journals (Sweden)

    Jorge Luis Amorim

    Full Text Available Citrus fruits have potential health-promoting properties and their essential oils have long been used in several applications. Due to biological effects described to some citrus species in this study our objectives were to analyze and compare the phytochemical composition and evaluate the anti-inflammatory effect of essential oils (EO obtained from four different Citrus species. Mice were treated with EO obtained from C. limon, C. latifolia, C. aurantifolia or C. limonia (10 to 100 mg/kg, p.o. and their anti-inflammatory effects were evaluated in chemical induced inflammation (formalin-induced licking response and carrageenan-induced inflammation in the subcutaneous air pouch model. A possible antinociceptive effect was evaluated in the hot plate model. Phytochemical analyses indicated the presence of geranial, limonene, γ-terpinene and others. EOs from C. limon, C. aurantifolia and C. limonia exhibited anti-inflammatory effects by reducing cell migration, cytokine production and protein extravasation induced by carrageenan. These effects were also obtained with similar amounts of pure limonene. It was also observed that C. aurantifolia induced myelotoxicity in mice. Anti-inflammatory effect of C. limon and C. limonia is probably due to their large quantities of limonene, while the myelotoxicity observed with C. aurantifolia is most likely due to the high concentration of citral. Our results indicate that these EOs from C. limon, C. aurantifolia and C. limonia have a significant anti-inflammatory effect; however, care should be taken with C. aurantifolia.

  14. Genotype and harvest time influence the phytochemical quality of Fino lemon juice (Citrus limon (L.) Burm. F.) for industrial use.

    Science.gov (United States)

    González-Molina, Elena; Moreno, Diego A; García-Viguera, Cristina

    2008-03-12

    Two clonal selections of lemon tree (Citrus limon Burm. f. cv. Fino), named Fino-49-5 and Fino-95, were studied to ascertain the influence of genetic (clone) and environmental (season) factors on the human-health bioactive compounds of lemon juice (vitamin C and flavonoids) and the possible relationship between composition and in vitro antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl, 2,2'-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid), and ferric reducing antioxidant power) of the juice. The cultivar Fino-49-5 performed better in terms of flavonoid and vitamin C contents. Variability in the weather conditions determined, at least in part, differences in the content of lemon juice bioactives more importantly than the genetic background did. Therefore, the food industry would have phytochemically rich and nutritive lemons with practically complete independence of the harvest time and the selected cultivar.

  15. Agrobacterium-Mediated Transfer of Arabidopsis ICE1 Gene into Lemon (Citrus Limon (L.) Burm. F. cv. Eureka)

    Institute of Scientific and Technical Information of China (English)

    HUANG Jia-quan; SUN Zhong-hai

    2005-01-01

    The Arabidopsis ICE1 (inducer of CBF expression 1) gene was cloned through RT-PCR of Arabidopsis cDNAs and introduced into the lemon (Citrus Limon (L.) Burm. F. cv. Eureka) genome using Agrobacterium-mediated transformation method. Epicotyl segments from in vitro grown lemon seedlings were co-cultivated with A. tumefaciens strain EHA 105 carrying the binary plasmid pMVICE1, whose T-DNA region contain ICE1 gene driven by 35S CaMV promoter. Among 320 epicotyl segments inoculated, 71 explants responded and regenerated 51 elongated shoots. These shoots were subjected to an extra month of kanamycin exposure. In this way, the number of escapes reduced. Thirteen of 31 survived shoots formed roots and 7 were tested positive using PCR technique. Southern blot analyses confirmed PCR results and demonstrated that more than two copies of the ICE1 gene were integrated into the lemon genome.

  16. Extensive Chemical Modifications in the Primary Protein Structure of IgG1 Subvisible Particles Are Necessary for Breaking Immune Tolerance.

    Science.gov (United States)

    Boll, Björn; Bessa, Juliana; Folzer, Emilien; Ríos Quiroz, Anacelia; Schmidt, Roland; Bulau, Patrick; Finkler, Christof; Mahler, Hanns-Christian; Huwyler, Jörg; Iglesias, Antonio; Koulov, Atanas V

    2017-04-03

    A current concern with the use of therapeutic proteins is the likely presence of aggregates and submicrometer, subvisible, and visible particles. It has been proposed that aggregates and particles may lead to unwanted increases in the immune response with a possible impact on safety or efficacy. The aim of this study was thus to evaluate the ability of subvisible particles of a therapeutic antibody to break immune tolerance in an IgG1 transgenic mouse model and to understand the particle attributes that might play a role in this process. We investigated the immunogenic properties of subvisible particles (unfractionated, mixed populations, and well-defined particle size fractions) using a transgenic mouse model expressing a mini-repertoire of human IgG1 (hIgG1 tg). Immunization with proteinaceous subvisible particles generated by artificial stress conditions demonstrated that only subvisible particles bearing very extensive chemical modifications within the primary amino acid structure could break immune tolerance in the hIgG1 transgenic mouse model. Protein particles exhibiting low levels of chemical modification were not immunogenic in this model.

  17. Thermo-chemical structure of the North China Craton from multi-observable probabilistic inversion: extent and causes of cratonic lithosphere modification

    Science.gov (United States)

    Guo, Z.; Afonso, J. C.; Qashqai, M.; Yang, Y.; Chen, J.

    2016-12-01

    Although the North China Craton (NCC) is one of the best documented cases of cratonic lithosphere modification, the actual causes, processes, and extent of lithospheric modification still are a matter of debate. Here, we present the first thermo-chemical model of the NCC from the surface down to 350 km by jointly inverting surface wave phase velocity data, geoid height, surface heat flow and absolute elevation with a novel multi-observable probabilistic inversion method. Our model reveals a thin ( 65-100 km) and chemically fertile lithosphere (8790) lithospheric mantle is imaged beneath the central TNCO and Ordos Block, reaching depths > 260 km. This lithospheric "keel" is surrounded to the east by a high-temperature sublithospheric anomaly that originates at depths > 280 km. The spatial distribution of this anomaly and its correlation with the location of recent volcanism in the region suggest that the anomaly represents a deep mantle upwelling being diverted by the cratonic keel and spreading onto regions of shallow lithosphere. Our results indicate that the present-day thermochemical structure beneath the NCC is the result of a complex interaction between a large-scale return flow associated with the subduction of the Pacific slab and the shallow lithospheric structure.

  18. Estudo da modificação química de polidienos do tipo SBR e BR Study of chemical modification of SBR and BR polydiene

    Directory of Open Access Journals (Sweden)

    Tatiana L. A. C. Rocha

    2004-12-01

    Full Text Available A utilização de modificações químicas de polidienos comerciais tem sido estudada como um meio alternativo à síntese de novos polímeros, para otimização das propriedades finais destes materiais através da introdução de diferentes grupamentos reativos na cadeia polimérica. A modificação química pode ser feita através de diferentes métodos, os quais podem ser realizados tanto em solução como em massa, onde podem ser destacadas as reações de epoxidação, sulfonação, maleinização, carboxilação, etc. Neste trabalho foi estudado o método de epoxidação de borrachas do tipo SBR e BR. Foi possível observar que mesmo pequenos graus de modificação química causam mudanças marcantes nas propriedades finais dos polímeros, como determinado para a temperatura de transição vítrea.Chemical modification of polydiene has been studied as an alternative route to obtain modified polymers with improved final properties. This improvement is due to the introduction of different kinds of reactive groups into a polymer chain, and it can be done in solution as well as in bulk. The chemical modification can be carried out by different methods such as epoxidation, maleination, carboxylation, sulfonation etc. In this work we show that in the epoxidation of SBR and BR even a small degree of modification can change the final properties of the polymer, as it occurred for the glass transition temperature.

  19. Research Progress in Chemical Modification Methods of Polysaccharide%多糖化学修饰方法的研究进展

    Institute of Scientific and Technical Information of China (English)

    方金红

    2014-01-01

    多糖是一类重要的生物大分子物质,具有抗肿瘤、抗病毒、抗氧化、免疫活性调节等生物活性。多糖的生物活性与其结构有直接关系,对多糖结构通过适当的方法进行修饰能提高或赋予多糖活性、降低某些多糖的毒副作用,修饰的方法包括化学法、物理法和生物法。该文综述了多糖化学修饰的方法、结构分析与鉴定技术及其研究进展,以期为多糖类药物的进一步研究提供依据。%Polysaccharide is an important class of biological macromolecules. It has a variety of biological activity, such as antitumor, an-tivirus, anti-oxidation, immune activity regulation. The biological activity of polysaccharide has a direct relationship with its struc-ture. Thus the structural modification of polysaccharide by an appropriate method can increase its biological activity and decrease some side effects, which including the chemical, physical and biological methods. The chemical modification method, structural analysis, identifi-cation technique and their research progress of polysaccharide modification are outlined so as to provide the basis for the further study on the polysaccharide drugs.

  20. Chemical modification of a plant origin biomass using cationic surfactant ABDAC and the biosorptive decolorization of RR45 containing solutions.

    Science.gov (United States)

    Akar, Tamer; Ozkara, Esra; Celik, Sema; Turkyilmaz, Serpil; Akar, Sibel Tunali

    2013-01-01

    This study focused on the improvement of the decolorization potential of biomass derived from Pyracantha coccinea. Alkyl benyzldimethyl ammonium chloride (ABDAC) was used as modification agent. Batch mode decolorization potential of modified biosorbent was explored at different operating conditions. ABDAC modification significantly increased the biosorption yield to 97.27%, which was 3.88 times higher than that of natural biomass. The prepared biosorbent was effectively used for the decolorization of Reactive Red 45 contaminated solutions after the optimization of biosorption conditions. The non-linear regression analysis was used to evaluate the isotherm and kinetic model parameters. Process followed the Langmuir isotherm model and the highest monolayer capacity of 152.49 mg g(-1) was obtained with a small amount of modified biosorbent. Kinetic studies indicated fast decolorization rate of the process following the pseudo-first-order model. Biosorption performance of the prepared biosorbent was tested in RR45 containing real wastewater sample. The possible dye biosorbent interactions in the biosorption process were explored by zeta potential, scanning electron microscobe and FTIR analysis.

  1. Role of strain and ligand effects in the modification of the electronic and chemical properties of bimetallic surfaces

    DEFF Research Database (Denmark)

    Kitchin, J.R.; Nørskov, Jens Kehlet; Barteau, M.A.;

    2004-01-01

    Periodic density functional calculations are used to illustrate how the combination of strain and ligand effects modify the electronic and surface chemical properties of Ni, Pd, and Pt monolayers supported on other transition metals. Strain and the ligand effects are shown to change the width...

  2. Chemical modification of silica gel with synthesized new Schiff base derivatives and sorption studies of cobalt (II) and nickel (II)

    Energy Technology Data Exchange (ETDEWEB)

    Kursunlu, Ahmed Nuri, E-mail: ankursunlu@gmail.com [Department of Chemistry, Selcuk University, Campus, 42075, Konya (Turkey); Guler, Ersin; Dumrul, Hakan; Kocyigit, Ozcan; Gubbuk, Ilkay Hilal [Department of Chemistry, Selcuk University, Campus, 42075, Konya (Turkey)

    2009-08-15

    In this study, three Schiff base ligands and their complexes were synthesized and characterized by infrared spectroscopy (IR), thermogravimetric analyses (TGA), nuclear magnetic resonance (NMR), elemental analysis and magnetic susceptibility apparatuses. Silica gel was respectively modified with Schiff base derivatives, (E)-2-[(2-chloroethylimino)methyl]phenol, (E)-4-[(2-chloroethylimino)methyl]phenol and N,N'-[1,4-phenilendi(E)methylidene]bis(2-chloroethanamine), after silanization of silica gel by (3-aminopropyl)trimethoxysilane (APTS) by using a suitable method. Characterization of the surface modification was also performed with IR, TGA and elemental analysis. The immobilized surfaces were used for Co(II) and Ni(II) sorption from aqueous solutions and values of sorption were detected by atomic absorption spectrometer (AAS).

  3. Fracture Toughness, Mechanical Property, And Chemical Characterization Of A Critical Modification To The NASA SLS Solid Booster Internal Material System

    Science.gov (United States)

    Pancoast, Justin; Garrett, William; Moe, Gulia

    2015-01-01

    A modified propellant-liner-insulation (PLI) bondline in the Space Launch System (SLS) solid rocket booster required characterization for flight certification. The chemical changes to the PLI bondline and the required additional processing have been correlated to mechanical responses of the materials across the bondline. Mechanical properties testing and analyses included fracture toughness, tensile, and shear tests. Chemical properties testing and analyses included Fourier transform infrared (FTIR) spectroscopy, cross-link density, high-performance liquid chromatography (HPLC), gas chromatography (GC), gel permeation chromatography (GPC), and wave dispersion X-ray fluorescence (WDXRF). The testing identified the presence of the expected new materials and found the functional bondline performance of the new PLI system was not significantly changed from the old system.

  4. Chemical modification of hygroscopic magnesium carbonate into superhydrophobic and oleophilic sorbent suitable for removal of oil spill in water

    Science.gov (United States)

    Patowary, Manoj; Ananthakrishnan, Rajakumar; Pathak, Khanindra

    2014-11-01

    The wettability of hygroscopic magnesium carbonate has been modified to develop a superhydrophobic and oleophilic sorbent for oil spill clean-ups via a simple chemical process using palmitic acid. The prepared material was characterized using X-ray diffraction, Fourier transform infra-red spectroscopy, and scanning electron microscopy. Wettability test infers that the sorbent has a static water contact angle of 154 ± 1°, thereby indicating its superhydrophobic character. The sorbent was capable of scavenging oil for about three times its weight, as determined from oil sorption studies, carried out using the sorbent on model oil-water mixture. Interestingly, the chemically modified sorbent has high selectivity, buoyancy, and rate of uptake of oil. Further, the reusability studies confirm the repeatable usage of the sorbent and its efficacy in oil spill remediation.

  5. Evaluation of the chemical modifications in petroleum asphalt cement with the addition of polypropylene; Avaliacao das modificacoes quimicas no cimento asfaltico de petroleo com a adicao de polipropileno

    Energy Technology Data Exchange (ETDEWEB)

    Marcondes, C.P.; Sales, M.J.A.; Resck, I.S., E-mail: mjsales@unb.b [Universidade de Brasilia (LabPol/UnB), DF (Brazil). Inst. de Quimica. Lab. de Pesquisa em Polimeros; Farias, M.M.; Souza, M.V.R. [Universidade de Brasilia (UnB), DF (Brazil). Dept. de Engenharia Civil e Ambiental

    2010-07-01

    Studies show that the common distress mode in the Brazilian highway network are fatigue cracks and plastic deformation, which are associated with the type of material used in the pavement layers, structural project, excessive traffic load and weathering. To minimize these defects, research on modifiers such as polymers, added to asphalt binders have been developed to provide physical, chemical and rheological improvement. This paper investigates chemical modifications of the binders with the addition of PP by FTIR, NMR and DSC. FTIR spectra of pure and modified binder showed no differences in absorption. NMR analysis showed no strong chemical bonds between the binder and PP. DSC curve of PP showed a melting temperature of 160 deg C ({Delta}H = 94J/g) and the pure binder presented an endothermic transition between 20 and 40 deg C ({Delta}H = 2J/g). In the DSC curves of mixtures, these transitions are not significant, indicating possible interactions between asphalt binder and PP. (author)

  6. Chemical display of pyrimidine bases flipped out by modification-dependent restriction endonucleases of MspJI and PvuRts1I families.

    Directory of Open Access Journals (Sweden)

    Evelina Zagorskaitė

    Full Text Available The epigenetic DNA modifications 5-methylcytosine (5mC and 5-hydroxymethylcytosine (5hmC in eukaryotes are recognized either in the context of double-stranded DNA (e.g., by the methyl-CpG binding domain of MeCP2, or in the flipped-out state (e.g., by the SRA domain of UHRF1. The SRA-like domains and the base-flipping mechanism for 5(hmC recognition are also shared by the recently discovered prokaryotic modification-dependent endonucleases of the MspJI and PvuRts1I families. Since the mechanism of modified cytosine recognition by many potential eukaryotic and prokaryotic 5(hmC "readers" is still unknown, a fast solution based method for the detection of extrahelical 5(hmC would be very useful. In the present study we tested base-flipping by MspJI- and PvuRts1I-like restriction enzymes using several solution-based methods, including fluorescence measurements of the cytosine analog pyrrolocytosine and chemical modification of extrahelical pyrimidines with chloroacetaldehyde and KMnO4. We find that only KMnO4 proved an efficient probe for the positive display of flipped out pyrimidines, albeit the method required either non-physiological pH (4.3 or a substitution of the target cytosine with thymine. Our results imply that DNA recognition mechanism of 5(hmC binding proteins should be tested using a combination of all available methods, as the lack of a positive signal in some assays does not exclude the base flipping mechanism.

  7. Novel biosorbent with high adsorption capacity prepared by chemical modification of white pine (Pinus durangensis) sawdust. Adsorption of Pb(II) from aqueous solutions.

    Science.gov (United States)

    Salazar-Rabago, J J; Leyva-Ramos, R

    2016-03-15

    The natural sawdust (NS) from white pine (Pinus durangensis) was chemically modified by a hydrothermal procedure using citric, malonic and tartaric acids. The adsorption capacity of modified sawdust (MS) towards Pb(II) was considerably enhanced due to the introduction of carboxylic groups on the surface of MS during the modification, and the adsorption capacity was almost linearly dependent on the concentration of carboxylic sites. The NS surface was acidic, and the MS surface became more acidic after the modification. At T = 25 °C and pH = 5, the maximum adsorption capacity of the optimal MS towards Pb(II) was 304 mg/g, which is exceptionally high compared to NS and other MS reported previously. The adsorption capacity of MS was considerably reduced from 304 to 154 mg/g by decreasing the solution pH from 5 to 3 due to electrostatic interactions. The adsorption of Pb(II) on MS was reversible at pH = 2, but not at pH = 5. The contribution percentage of ion exchange to the overall adsorption capacity ranged from 70 to 99% and 10-66% at the initial pH of 3 and 5, respectively. Hence, the adsorption of Pb(II) on MS was mainly due to ion exchange at pH = 3 and to both ion exchange and electrostatic attraction at pH = 5.

  8. Modifications of the chemical structure of phenolics differentially affect physiological activities in pulvinar cells of Mimosa pudica L. I. Multimode effect on early membrane events.

    Science.gov (United States)

    Rocher, Françoise; Dédaldéchamp, Fabienne; Saeedi, Saed; Fleurat-Lessard, Pierrette; Chollet, Jean-Francois; Roblin, Gabriel

    2014-11-01

    A study of the structure-activity relationship carried out on several benzoic acid-related phenolics indicates that this type of compounds hinders the osmocontractile reaction of pulvinar cells in the range of 0-100%. Tentatively, we tried to find a way that could explain this differential action. With this aim, the relationship between the inhibitory effect and important molecular physico-chemical parameters (namely lipophilicity and degree of dissociation) was drawn. In addition, the effect of a variety of these compounds was investigated on their capacity to modify the electrical transmembrane potential and induce modifications in proton fluxes. Finally, using plasma membrane vesicles purified from pulvinar tissues, we examined the effects of some selected compounds on the proton pump activity and catalytic activity of the plasma membrane H(+)-ATPase. Taken together, the results indicate that a modification of the molecular structure of phenolics may induce important variation in the activity of the compound on these early membrane events. Among the tested phenolics, salicylic acid (SA) and acetylsalicylic acid (ASA, aspirin) are of particuler note, as they showed atypical effects on the physiological processes studied. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  9. Isolation and chemical modification of clerodane diterpenoids from Salvia species as potential agonists at the kappa-opioid receptor.

    Science.gov (United States)

    Li, Yiqiang; Husbands, Stephen M; Mahon, Mary F; Traynor, John R; Rowan, Michael G

    2007-07-01

    The clerodane diterpenoid salvinorin A (1), the main active component of the psychotropic herb Salvia divinorum, has been reported to be a potent agonist at the kappa-opioid receptor. Computer modeling suggested that splendidin (2) from S. splendens, as well as related compounds, might possess similar activities. In the present study, this hypothesis was tested by determination of the binding properties of a series of structural congeners, compounds 2-8, at the mu-, delta-, and kappa-opioid receptors. However, none of these compounds showed significant binding to any of the opioid-receptor subtypes, thus disproving the above hypothesis. The novel compounds 7 and 8 were obtained semi-synthetically by selective modification of salvifarin (5), isolated from Salvia farinacea, upon epoxide-ring opening with AcOH in the presence of indium(III) triflate. Also, the X-ray crystal structure of salvifaricin (6; Fig.), obtained from S. farinacea, was determined for the first time and used, in combination with in-depth NMR experiments, to elucidate the absolute configurations of the new products. Our experiments demonstrate that the relatively well-accessible diterpenoid 6 could be used as starting material for future studies into the structure-activity relationship at the kappa-opioid receptor.

  10. Stevia Glycosides: Chemical and Enzymatic Modifications of Their Carbohydrate Moieties to Improve the Sweet-Tasting Quality.

    Science.gov (United States)

    Gerwig, Gerrit J; Te Poele, Evelien M; Dijkhuizen, Lubbert; Kamerling, Johannis P

    2016-01-01

    Stevia glycosides, extracted from the leaves of the plant Stevia rebaudiana Bertoni, display an amazing high degree of sweetness. As processed plant products, they are considered as excellent bio-alternatives for sucrose and artificial sweeteners. Being noncaloric and having beneficial properties for human health, they are the subject of an increasing number of studies for applications in food and pharmacy. However, one of the main obstacles for the successful commercialization of Stevia sweeteners, especially in food, is their slight bitter aftertaste and astringency. These undesirable properties may be reduced or eliminated by modifying the carbohydrate moieties of the steviol glycosides. A promising procedure is to subject steviol glycosides to enzymatic glycosylation, thereby introducing additional monosaccharide residues into the molecules. Depending on the number and positions of the monosaccharide units, the taste quality and sweetness potency of the compounds will vary. Many studies have been performed already, and this review summarizes the structures of native steviol glycosides and the recent data of modifications of the carbohydrate moieties that have been published to provide an overview of the current progress.

  11. Studies on Wheat Gluten and Its Chemical Modification%小麦面筋蛋白及其化学改性研究

    Institute of Scientific and Technical Information of China (English)

    钟耕; 陈宗道; 闵燕萍; 艾平

    2001-01-01

    介绍了国际上小麦面筋蛋白的研究开发途径,阐述了面筋蛋白进行深度加工与利用的目的意义,并且对化学改性小麦面筋蛋白的原理、方法及非食品应用进行了重点介绍。%The international exploitation ways of wheat gluten were presented. The targets of the deep processing and the utilization of wheat gluten were expounded. The principles and methods for chemical modification of wheat gluten as well as the non-food application were introduced emphatically.

  12. Studies on chemical modification and biology of a natural product, gambogic acid (II): Synthesis and bioevaluation of gambogellic acid and its derivatives from gambogic acid as antitumor agents.

    Science.gov (United States)

    Wang, Jinxin; Ma, Junhai; You, Qidong; Zhao, Li; Wang, Fan; Li, Chong; Guo, Qinglong

    2010-09-01

    Gambogic acid (GA) has been reported to be a potent apoptosis inducer. The fact that it is amenable to chemical modification makes GA an attractive molecule for the development of anticancer agents. We firstly reported the synthesis of gambogellic acid, which was generated under acid catalysis from readily available GA by a base-catalyzed diene intramolecular annelation. Sequentially, thirteen new compounds were synthesized and their inhibitory activity on HT-29, Bel-7402, BGC-823, and A549 cell lines were evaluated in vitro by MTT assay, and (38, 40)-epoxy-33-chlorogambogellic acid (4) was identified as a BGC-823 cell apoptosis inducer through MTT cell assay, observations of morphological changes, and Annexin-V/PI double-staining assay. Compound 4 showed significant effects in inducing apoptosis and might serve as a potential lead compound for discovery of new anticancer drugs. Further structure-activity relationships (SARs) of gambogic acid derivatives were discussed.

  13. A post-modification approach to independent compo-nent analysis for resolution of overlapping GC/MS signals:from independent components to chemical components

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Independent component analysis (ICA) has demonstrated its power to extract mass spectra from over-lapping GC/MS signal. However, there is still a problem that mass spectra with negative peaks at some m/z will be obtained in the resolved results when there are overlapping peaks in the mass spectra of a mixture. Based on a detail theoretical analysis of the preconditions for ICA and the non-negative property of GC/MS signals, a post-modification based on chemical knowledge (PMBK) strategy is pro-posed to solve this problem. By both simulated and experimental GC/MS signals, it was proved that the PMBK strategy can improve the resolution effectively.

  14. An example of deep crustal brines effecting large-scale chemical modification of the crust during assembly of the Paleoproterozoic Columbia supercontinent

    Science.gov (United States)

    Glassley, W. E.; Korstgard, J. A.; Sørensen, K.

    2009-12-01

    The Nagssugtoqidian Mobile Belt (NMB) is a 300 km wide, 800 km long orogenic zone in central Greenland. It is part of the >20,000 km long complex of orogenic belts that formed between 1.7 and 2.0 Gya during assembly of the first supercontinent, Columbia,. The NMB is composed of several major crustal-scale shear zones that intervene between coherent blocks of high-grade metamorphic rocks. By combining detailed field, laboratory and aeromagnetic studies along the most northern of the shear zones (the Nordre Stromfjord Shear Zone - NSSZ), we have been able to document large scale chemical modification of the crust caused by the invasion of brines generated during continent-continent collision. The tectonic framework for this process is the following: 1. At 1,923 +/- 20 Mya: Emplacement of a calc-alkaline complex within and on ca. 2.8 Gya continental crust. The basal cumulate portion of the complex is well preserved and records invasion of multiple magma pulses. Coeval pillow basalts and cogenetic porphyritic mafics are also present. 2. 1,900 to 1,800 Mya: Tectonic emplacement of mafic and ultramafic rocks under high pressure (>2.5 GPa), eclogite facies conditions. The emplacement of these lenses probably occurred prior to or during thrust stacking associated with continent-continent collision. The age of the high pressure metamorphism makes these the oldest known eclogite facies metamorphic rocks in the world. 3. 1760 to 1720 Mya: Development of the transcurrent NSSZ, with displacements in excess of a hundred kilometers. Profound chemical enrichment of potassium and phosphorus along the entire length of the NSSZ unequivocally demonstrates that the shear zone was the focus of massive fluid movement. Detailed analysis of phase relationships documents a P-T path identical in form to that of Alpine metamorphic rocks, but displaced toward higher temperatures. These observations provide compelling evidence that assembly of this segment of Columbia involved subduction of

  15. Modification of the titanium oxide morphology and composition by a combined chemical-electrochemical treatment on cp Ti

    Directory of Open Access Journals (Sweden)

    Ernesto Peláez-Abellán

    2012-02-01

    Full Text Available A combined chemical-electrochemical oxidation method to obtain porous bioactive TiO2 films on titanium is reported. In this case, a titanium chemical pre-etching followed by the micro-arc oxidation (MAO treatment is proposed and optimized, to obtain a high-roughness and porous surface which benefits the titanium/bone integration. The MAO treatment at various rates (different current densities allowed to define the influence of the oxide growth rate on the surface morphology and to design the best features for each case. Titanium samples were pre-etched using a 2% HF solution as a function of the etching time, and then anodized by the MAO treatment in a 0.5 M H3PO4 solution at current densities in the 10 to 90 mA.cm-2 range. High porosity (0.5 to 1 µm-diameter pores and higher phosphorous content for TiO2 films were achieved by first etching the Ti sample for 180 seconds in the HF solution, and then applying current densities in the 80 to 90 mA.cm-2 range for the micro-arc oxidation process.

  16. Chemical modification of extracellular matrix by cold atmospheric plasma-generated reactive species affects chondrogenesis and bone formation.

    Science.gov (United States)

    Eisenhauer, Peter; Chernets, Natalie; Song, You; Dobrynin, Danil; Pleshko, Nancy; Steinbeck, Marla J; Freeman, Theresa A

    2016-09-01

    The goal of this study was to investigate whether cold plasma generated by dielectric barrier discharge (DBD) modifies extracellular matrices (ECM) to influence chondrogenesis and endochondral ossification. Replacement of cartilage by bone during endochondral ossification is essential in fetal skeletal development, bone growth and fracture healing. Regulation of this process by the ECM occurs through matrix remodelling, involving a variety of cell attachment molecules and growth factors, which influence cell morphology and protein expression. The commercially available ECM, Matrigel, was treated with microsecond or nanosecond pulsed (μsp or nsp, respectively) DBD frequencies conditions at the equivalent frequencies (1 kHz) or power (~1 W). Recombinant human bone morphogenetic protein-2 was added and the mixture subcutaneously injected into mice to simulate ectopic endochondral ossification. Two weeks later, the masses were extracted and analysed by microcomputed tomography. A significant increase in bone formation was observed in Matrigel treated with μsp DBD compared with control, while a significant decrease in bone formation was observed for both nsp treatments. Histological and immunohistochemical analysis showed Matrigel treated with μsp plasma increased the number of invading cells, the amount of vascular endothelial growth factor and chondrogenesis while the opposite was true for Matrigel treated with nsp plasma. In support of the in vivo Matrigel study, 10 T1/2 cells cultured in vitro on μsp DBD-treated type I collagen showed increased expression of adhesion proteins and activation of survival pathways, which decreased with nsp plasma treatments. These results indicate DBD modification of ECM can influence cellular behaviours to accelerate or inhibit chondrogenesis and endochondral ossification. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  17. Structure-Function, Stability, and Chemical Modification of the Cyanobacterial Cytochrome b6f Complex from Nostoc sp. PCC 7120*

    Science.gov (United States)

    Baniulis, Danas; Yamashita, Eiki; Whitelegge, Julian P.; Zatsman, Anna I.; Hendrich, Michael P.; Hasan, S. Saif; Ryan, Christopher M.; Cramer, William A.

    2009-01-01

    The crystal structure of the cyanobacterial cytochrome b6f complex has previously been solved to 3.0-Å resolution using the thermophilic Mastigocladus laminosus whose genome has not been sequenced. Several unicellular cyanobacteria, whose genomes have been sequenced and are tractable for mutagenesis, do not yield b6f complex in an intact dimeric state with significant electron transport activity. The genome of Nostoc sp. PCC 7120 has been sequenced and is closer phylogenetically to M. laminosus than are unicellular cyanobacteria. The amino acid sequences of the large core subunits and four small peripheral subunits of Nostoc are 88 and 80% identical to those in the M. laminosus b6f complex. Purified b6f complex from Nostoc has a stable dimeric structure, eight subunits with masses similar to those of M. laminosus, and comparable electron transport activity. The crystal structure of the native b6f complex, determined to a resolution of 3.0Å (PDB id: 2ZT9), is almost identical to that of M. laminosus. Two unique aspects of the Nostoc complex are: (i) a dominant conformation of heme bp that is rotated 180° about the α- and γ-meso carbon axis relative to the orientation in the M. laminosus complex and (ii) acetylation of the Rieske iron-sulfur protein (PetC) at the N terminus, a post-translational modification unprecedented in cyanobacterial membrane and electron transport proteins, and in polypeptides of cytochrome bc complexes from any source. The high spin electronic character of the unique heme cn is similar to that previously found in the b6f complex from other sources. PMID:19189962

  18. Enzymatic modification of starch

    DEFF Research Database (Denmark)

    Jensen, Susanne Langgård

    In the food industry approaches for using bioengineering are investigated as alternatives to conventional chemical and physical starch modification techniques in development of starches with specific properties. Enzyme-assisted post-harvest modification is an interesting approach to this, since...... branching connecting larger chain segments. In case of high BE activity this transfer happened prior to hydration and phase separation. The starch substrates thereby became locked in their granular structure and blocked furher access of BE. Transferase-based modification of starch has today almost...... exclusively been conducted on gelatinized starch. This study provides a new concept for transferase-based modification of starches in granular state....

  19. Simultaneous chemical modification and structural transformation of Stöber silica spheres for integration of nanocatalysts

    KAUST Repository

    Yao, Kexin

    2012-01-10

    A synthetic approach has been devised to convert conventional Stöber silica (SiO 2) spheres into a new type of porous structural platform for supporting multicomponent catalysts. With this approach, we have first prepared zinc-doped SiO 2 (Zn-SiO 2) hollow spheres, on which zinc oxide (ZnO) phase and ruthenium (Ru) nanoparticles have been deposited and assembled sequentially in solution phase. A series of complex Ru/ZnO/Zn-SiO 2 nanocatalysts has been thus been integrated onto the zinc-doped SiO 2 supports after additional thermal treatment and reduction. To test their workability under harsh reactive environments, we have further evaluated the above prepared catalysts using arene hydrogenation as model reactions. These integrated nanocatalysts have shown superior activity, high robustness, and easy recovery in the studied heterogeneous catalysis. © 2011 American Chemical Society.

  20. Sputtering yields and surface chemical modification of tin-doped indium oxide in hydrocarbon-based plasma etching

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hu; Karahashi, Kazuhiro; Hamaguchi, Satoshi, E-mail: hamaguch@ppl.eng.osaka-u.ac.jp [Center for Atomic and Molecular Technologies, Osaka University, Yamadaoka 2-1, Suita 565-0871 (Japan); Fukasawa, Masanaga; Nagahata, Kazunori; Tatsumi, Tetsuya [Device and Material R& D Group, RDS Platform, Sony Corporation, Kanagawa 243-0014 (Japan)

    2015-11-15

    Sputtering yields and surface chemical compositions of tin-doped indium oxide (or indium tin oxide, ITO) by CH{sup +}, CH{sub 3}{sup +}, and inert-gas ion (He{sup +}, Ne{sup +}, and Ar{sup +}) incidence have been obtained experimentally with the use of a mass-selected ion beam system and in-situ x-ray photoelectron spectroscopy. It has been found that etching of ITO is chemically enhanced by energetic incidence of hydrocarbon (CH{sub x}{sup +}) ions. At high incident energy incidence, it appears that carbon of incident ions predominantly reduce indium (In) of ITO and the ITO sputtering yields by CH{sup +} and CH{sub 3}{sup +} ions are found to be essentially equal. At lower incident energy (less than 500 eV or so), however, a hydrogen effect on ITO reduction is more pronounced and the ITO surface is more reduced by CH{sub 3}{sup +} ions than CH{sup +} ions. Although the surface is covered more with metallic In by low-energy incident CH{sub 3}{sup +} ions than CH{sup +} ions and metallic In is in general less resistant against physical sputtering than its oxide, the ITO sputtering yield by incident CH{sub 3}{sup +} ions is found to be lower than that by incident CH{sup +} ions in this energy range. A postulation to account for the relation between the observed sputtering yield and reduction of the ITO surface is also presented. The results presented here offer a better understanding of elementary surface reactions observed in reactive ion etching processes of ITO by hydrocarbon plasmas.

  1. Effect of pH on the chemical modification of quercetin and structurally related flavonoids characterized by optical (UV-visible and Raman) spectroscopy.

    Science.gov (United States)

    Jurasekova, Z; Domingo, C; Garcia-Ramos, J V; Sanchez-Cortes, S

    2014-07-07

    In this work we report the study of the chemical modifications undergone by flavonoids, especially by quercetin (QUC), under alkaline conditions by UV-visible absorption, Raman and surface-enhanced Raman scattering (SERS) spectroscopy, the study was performed in aqueous solution and also on Ag nanoparticles (AgNPs). Several processes are involved in the effect of alkaline pH both in solution and on AgNPs: autoxidation affecting mainly the C-ring of the molecule and giving rise to the molecular fragmentation leading to simpler molecular products, and/or the dimerization and further polymerization leading to species with a higher molecular weight. In addition, there exists a clear structure-instability correlation concerning mainly particular groups in the molecule: the C3-OH group in the C-ring, the catechol moiety in the B-ring and the C2=C3 bond also existing in the C-ring. QUC possesses all these groups and exhibits high instability in alkaline solution. The SERS spectra registered at different pH revealed a change in the dimerization protocol of QUC going from the A- and C-rings-like-condensation to B-ring-like-condensation. Increasing the knowledge of the chemical properties of these compounds and determining the structure-activity relationship under specific environmental factors allow us to improve their beneficial properties for health as well as the preservation of Cultural Heritage objects, for example, by preventing their degradation.

  2. Reactive Extrusion for In-situ Chemical Modification of Cellulose with De-Octenyl succinic anhydride (DDSA in presence of Ionic liquid

    Directory of Open Access Journals (Sweden)

    Magdi Elamin Gibril

    2012-07-01

    Full Text Available Modification of microcrystalline cellulose by means of DDSA through the reactive extrusion process was preformed. The process was carried out by twin screw extruder in the presence of ionic liquids (IL, 1-butyl-3- methylimidazolium chloride [Bmim]Cl. The suitable composition for cellulose/IL mixture and optimum conditions for extrusion process were determined. Degree of substitution (DS for modified cellulose was found to be in the range of 0.100- 0.284. In order to study the chemical structure and the physical properties of the modified cellulose, characterization was done by FT-IR, solid-state CP/MAS 13CNMR, and theromgravimetric analysis. FT-IR data were found to have a new peak in contrast to original reactant which clearly indicated the presence of a chemical group. CP/MAS 13CNMR analysis approved the existence of succinylation between cellulose and DDSA. The TGA analysis showed that the thermal stability of modified cellulose was decreased upon increasing of the degree of substitution (DS or the increasing of the amount of DDSA in the samples.

  3. 碱基的化学修饰与功能核酸研究%Chemical modifications of nucleobases in functional nucleic acids

    Institute of Scientific and Technical Information of China (English)

    何军林

    2014-01-01

    The diversity of functional nucleic acids is being explored from nature and in vitro selections,including ribozyme catalysis,aptamer binding to target molecules with high specific and affinity,and RNA interference and modulation of gene expression. The great potential of chemical and biological activity of four nucleobases and the sugar-phosphate backbone in various specific tertiary structures is beyond our present imagination,and more functions remain to be found. Therefore,developing insight into the structural basis of these functional nucleic acids is invaluable in understanding their mechanisms and exploring the applications. With a special focus on the four nucleobases,we learnt that nucleobases could contribute to the functions by base stacking,electrostatic interactions,complexion with metal ions,hydrogen bonding,and even act as general acid-base in specific functions. Deletion and substitution of each nucleobases demonstrated the conservation of all the natural and unnatural functional nucleic acids. But from the success of chemical modifications at the level of functional groups on 10-23 DNAzyme,there is still room for the optimization of functional nucleic acids,for practical applications as research tools and genetic therapeutics. It is a big challenge for any functional nucleic acids,to conduct the chemical modification in a right way in the complex tertiary structures, including which residue could be used for chemical modification and which functional groups could be introduced for an expected positive effect.%核酸的多样化功能正在逐渐被揭示出来,从核酶的催化功能,适配体特异性结合靶分子,到小 RNA 分子对于基因的干扰和调控,4种碱基和核糖-磷酸单元骨架借助多样化的高级结构展现出的化学活性和生物活性远非我们现在的认识水平,或许还有更多的功能等待开发出来。从这些天然和非天然功能核酸的结构和机制研究中,碱基替换和消

  4. Modification of chemical, optical and structural properties of Bayfol CR-6-2 using gamma and neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Shehata, Mohamed M.; Radwan, Samh I.; Hassan, Amin [Atomic Energy Authority, Cairo (Egypt). Nuclear Research Centre; Waly, Sayed A. [Atomic Energy Authority, Cairo (Egypt). Second Research Reactor; Badawy, Zaynab M. [Atomic Energy Authority, Cairo (Egypt). Experimental Nuclear Physics Dept.

    2016-08-01

    The effects of gamma and neutron irradiations on the chemical, optical and structural properties of Bayfol CR-6-2 were investigated. The samples were irradiated by γ-rays from a {sup 60}Co source at various doses ranging between 16 and 900 kGy at room temperature in atmospheric air. For neutrons, an Am-Be neutron facility was used for the sample irradiation in thermal mode which had an activity of 185 GBq. Samples were irradiated with different doses of neutrons ranging from 15.7 to 564.2 mGy. The changes induced were analyzed using UV-Vis and Fourier transform infrared (FTIR) spectrometry. The results demonstrated an occurrence of oxidative degradation, resulting in the formation of carbonyl groups at 1700 cm{sup -1}. Simultaneous thermo-gravimetric investigation (TGA) has been performed on the samples of 0.3 mm thickness. The results obtained indicate that cross-linking predominates at small neutron doses and main chain scission happens at higher doses.

  5. Comprehensive profiling of zebrafish hepatic proximal promoter CpG island methylation and its modification during chemical carcinogenesis

    Directory of Open Access Journals (Sweden)

    Gong Zhiyuan

    2011-01-01

    Full Text Available Abstract Background DNA methylation is an epigenetic mechanism associated with regulation of gene expression and it is modulated during chemical carcinogenesis. The zebrafish is increasingly employed as a human disease model; however there is a lack of information on DNA methylation in zebrafish and during fish tumorigenesis. Results A novel CpG island tiling array containing 44,000 probes, in combination with immunoprecipitation of methylated DNA, was used to achieve the first comprehensive methylation profiling of normal adult zebrafish liver. DNA methylation alterations were detected in zebrafish liver tumors induced by the environmental carcinogen 7, 12-dimethylbenz(aanthracene. Genes significantly hypomethylated in tumors were associated particularly with proliferation, glycolysis, transcription, cell cycle, apoptosis, growth and metastasis. Hypermethylated genes included those associated with anti-angiogenesis and cellular adhesion. Of 49 genes that were altered in expression within tumors, and which also had appropriate CpG islands and were co-represented on the tiling array, approximately 45% showed significant changes in both gene expression and methylation. Conclusion The functional pathways containing differentially methylated genes in zebrafish hepatocellular carcinoma have also been reported to be aberrantly methylated during tumorigenesis in humans. These findings increase the confidence in the use of zebrafish as a model for human cancer in addition to providing the first comprehensive mapping of DNA methylation in the normal adult zebrafish liver.

  6. Surface modification of reverse osmosis desalination membranes by thin-film coatings deposited by initiated chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ozaydin-Ince, Gozde, E-mail: gozdeince@sabanciuniv.edu [Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Matin, Asif, E-mail: amatin@mit.edu [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Khan, Zafarullah, E-mail: zukhan@mit.edu [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Zaidi, S.M. Javaid, E-mail: zaidismj@kfupm.edu.sa [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Gleason, Karen K., E-mail: kkgleasn@mit.edu [Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2013-07-31

    Thin-film polymeric reverse osmosis membranes, due to their high permeation rates and good salt rejection capabilities, are widely used for seawater desalination. However, these membranes are prone to biofouling, which affects their performance and efficiency. In this work, we report a method to modify the membrane surface without damaging the active layer or significantly affecting the performance of the membrane. Amphiphilic copolymer films of hydrophilic hydroxyethylmethacrylate and hydrophobic perfluorodecylacrylate (PFA) were synthesized and deposited on commercial RO membranes using an initiated chemical vapor deposition technique which is a polymer deposition technique that involves free-radical polymerization initiated by gas-phase radicals. Relevant surface characteristics such as hydrophilicity and roughness could be systematically controlled by varying the polymer chemistry. Increasing the hydrophobic PFA content in the films leads to an increase in the surface roughness and hydrophobicity. Furthermore, the surface morphology studies performed using the atomic force microscopy show that as the thickness of the coating increases average surface roughness increases. Using this knowledge, the coating thickness and chemistry were optimized to achieve high permeate flux and to reduce cell attachment. Results of the static bacterial adhesion tests show that the attachment of bacterial cells is significantly reduced on the coated membranes. - Highlights: • Thin films are deposited on reverse osmosis membranes. • Amphiphilic thin films are resistant to protein attachment. • The permeation performance of the membranes is not affected by the coating. • The thin film coatings delayed the biofouling.

  7. Thermal and chemical modification of titanium-aluminum-vanadium implant materials: effects on surface properties, glycoprotein adsorption, and MG63 cell attachment.

    Science.gov (United States)

    MacDonald, D E; Rapuano, B E; Deo, N; Stranick, M; Somasundaran, P; Boskey, A L

    2004-07-01

    The microstructure, chemical composition and wettability of thermally and chemically modified Ti-6Al-4V alloy disks were characterized and correlated with the degree of radiolabeled fibronectin-alloy surface adsorption and subsequent adhesion of osteoblast-like cells. Heating either in pure oxygen or atmosphere (atm) resulted in an enrichment of Al and V within the surface oxide. Heating (oxygen/atm) and peroxide treatment both followed by butanol treatment resulted in a reduction in content of V, but not in Al. Heating (oxygen/atm) or peroxide treatment resulted in a thicker oxide layer and a more hydrophilic surface when compared with passivated controls. Post-treatment with butanol, however, resulted in less hydrophilic surfaces than heating or peroxide treatment alone. The greatest increases in the adsorption of radiolabeled fibronectin following treatment were observed with peroxide/butanol-treated samples followed by peroxide/butanol and heat/butanol, although binding was only increased by 20-40% compared to untreated controls. These experiments with radiolabeled fibronectin indicate that enhanced adsorption of the glycoprotein was more highly correlated with changes in chemical composition, reflected in a reduction in V content and decrease in the V/Al ratio, than with changes in wettability. Despite promoting only a modest elevation in fibronectin adsorption, the treatment of disks with heat or heat/butanol induced a several-fold increase in the attachment of MG63 cells promoted by a nonadhesive concentration of fibronectin that was used to coat the pretreated disks compared to uncoated disks. Therefore, results obtained with these modifications of surface properties indicate that an increase in the absolute content of Al and/or V (heat), and/or in the Al/V ratio (with little change in hydrophilicity; heat+butanol) is correlated with an increase in the fibronectin-promoted adhesion of an osteoblast-like cell line. It would also appear that the thermal

  8. Modification on epoxy-based adhesive

    Institute of Scientific and Technical Information of China (English)

    ZhengXiaoxia; QianChunxiang

    2003-01-01

    This research adopted four methods to toughen epoxy adhesives. They were liquid hydroxyl group terminated polybutadiene (HTPB) rubber modification, silicon rubber modification, polyacrylate multiplicity elastomer particulates emulsion modification and chemical grafting modification. After modification, the shearing strength and the rapture elongation were tested. The interface and the chemical reaction between the modifiers and the epoxy were analyzed by scanning electron microscope (SEM) and infrared optical spectrum. The results show that the elastomer particulates modification and the chemical grafting modification can reach the better toughening effects.

  9. Tandem Mass Spectrometry of Heparan Sulfate Negative Ions: Sulfate Loss Patterns and Chemical Modification Methods for Improvement of Product Ion Profiles

    Science.gov (United States)

    Shi, Xiaofeng; Huang, Yu; Mao, Yang; Naimy, Hicham; Zaia, Joseph

    2012-09-01

    Heparan sulfate (HS) is a polysaccharide modified with sulfation, acetylation, and epimerization that enable its binding with protein ligands and regulation of important biological processes. Tandem mass spectrometry has been employed to sequence linear biomolecules e.g., proteins and peptides. However, its application in structural characterization of HS is limited due to the neutral loss of sulfate (SO3) during collisional induced dissociation (CID). In this report, we studied the dissociation patterns of HS disaccharides and demonstrate that the N-sulfate (N-S) bond is especially facile during CID. We identified factors that influence the propensities of such losses from precursor ions and proposed a Free Proton Index (FPI) to help select ions that are able to produce meaningful backbone dissociations. We then investigated the thermodynamics and kinetics of SO3 loss from sulfates that are protonated, deprotonated, and metal-adducted using density functional theory computations. The calculations showed that sulfate loss from a protonated site was much more facile than that from a deprotonated or metal-adducted site. Further, the loss of SO3 from N-sulfate was energetically favored by 3-8 kcal/mol in transition states relative to O-sulfates, making it more prone to this process by a substantial factor. In order to reduce the FPI, representing the number of labile sulfates in HS native chains and oligosaccharides, we developed a series of chemical modifications to selectively replace the N-sulfates of the glucosamine with deuterated acetyl group. These modifications effectively reduced the sulfate density on the HS oligosaccharides and generated considerably more backbone dissociation using on-line LC/tandem MS.

  10. Biomimetic synthesis of silver nanoparticles by Citrus limon (lemon) aqueous extract and theoretical prediction of particle size.

    Science.gov (United States)

    Prathna, T C; Chandrasekaran, N; Raichur, Ashok M; Mukherjee, Amitava

    2011-01-01

    In the present study, silver nanoparticles were rapidly synthesized at room temperature by treating silver ions with the Citrus limon (lemon) extract. The effect of various process parameters like the reductant concentration, mixing ratio of the reactants and the concentration of silver nitrate were studied in detail. In the standardized process, 10(-2)M silver nitrate solution was interacted for 4h with lemon juice (2% citric acid concentration and 0.5% ascorbic acid concentration) in the ratio of 1:4 (vol:vol). The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance as determined by UV-Visible spectra in the range of 400-500 nm. X-ray diffraction analysis revealed the distinctive facets (111, 200, 220, 222 and 311 planes) of silver nanoparticles. We found that citric acid was the principal reducing agent for the nanosynthesis process. FT-IR spectral studies demonstrated citric acid as the probable stabilizing agent. Silver nanoparticles below 50 nm with spherical and spheroidal shape were observed from transmission electron microscopy. The correlation between absorption maxima and particle sizes were derived for different UV-Visible absorption maxima (corresponding to different citric acid concentrations) employing "MiePlot v. 3.4". The theoretical particle size corresponding to 2% citric acid concentration was compared to those obtained by various experimental techniques like X-ray diffraction analysis, atomic force microscopy, and transmission electron microscopy.

  11. Surface modification and characterization of γ-Fe{sub 2}O{sub 3} nanoparticles synthesized by chemically-induced transition

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Longlong [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Li, Jian, E-mail: aizhong@swu.edu.cn [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Lin, Yueqiang; Liu, Xiaodong; Lin, Lihua [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Li, Decai [School of Mechanical and Control Engineering, Beijing Jiaotong University, Beijing 100044 (China)

    2013-09-16

    γ-Fe{sub 2}O{sub 3} nanoparticles have been synthesized by chemically-induced transition in FeCl{sub 2} solution (sample(0)). Surface modification of the particles in a post-synthesis step using Fe(NO{sub 3}){sub 3} solution (sample (1)) and during synthesis by adding ZnCl{sub 2} (sample (2)) has been attempted, and the morphologies, crystal structures, chemical compositions and magnetizations of the resultant samples have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray energy-dispersive spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry (VSM). The size of the particles was of the order of 10 nm. Particles in samples (1) and (2) had a γ-Fe{sub 2}O{sub 3} core while sample (1) had a Fe(NO{sub 3}){sub 3}·9H{sub 2}O shell, and sample (2) had an external shell of ZnFe{sub 2}O{sub 4}, and FeCl{sub 3}·6H{sub 2}O as an outermost layer. Adsorption on the surface of the nanoparticles lowered their diffraction intensity, such that diameters of the grains of the spinel structure estimated by XRD were larger than the average particle diameter obtained by TEM for samples (0) and (2). Sample magnetization depended mainly on the content of the γ-Fe{sub 2}O{sub 3} phase. The molar and mass ratios of the phases have been estimated from the characterization results for each sample. - Highlights: • Surface modifications of Fe{sub 2}O{sub 3} particles in post and during synthesis are performed. • The surface structure of the modified particles is revealed. • The molar and mass rations of phases in the modified particles are estimated. • A new route for the preparation of γ-Fe{sub 2}O{sub 3} based composite nanoparticles is proposed.

  12. Chemical modification of the urokinase-type plasminogen activator and its receptor using tetranitromethane. Evidence for the involvement of specific tyrosine residues in both molecules during receptor-ligand interaction

    DEFF Research Database (Denmark)

    Ploug, M; Rahbek-Nielsen, H; Ellis, V

    1995-01-01

    ., Ellis, V., & Danø, K. (1994) Biochemistry 33, 8991-8997]. To identify residues engaged in the uPAR-uPA interaction, we have performed a "protein-protein footprinting" study on preformed uPAR-GFD complexes by chemical modification with tetranitromethane. All six tyrosine residues in uPAR and the single...

  13. Chemical generation and modification of peptides containing multiple dehydroalanines† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5cc05469a Click here for additional data file.

    Science.gov (United States)

    Morrison, Philip M.; Foley, Patrick J.; Warriner, Stuart L.

    2015-01-01

    Chemical formation of dehydroalanine has been widely used for the post-translational modification of proteins and peptides, however methods to incorporate multiple dehydroalanine residues into a single peptide have not been defined. We report the use of methyl 2,5-dibromovalerate which can be used to cleanly carry out this transformation. PMID:26219458

  14. Improved renal clearance and tumor targeting of {sup 99m}Tc-labeled anti-Tac monoclonal antibody Fab by chemical modifications

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Meyoung-kon; Jeong, Hyeh-Jean; Kao, Chih-Hao K.; Yao, Zhengsheng; Paik, David S.; Pie, Jae Eun; Kobayashi, Hisataka; Waldmann, Thomas A.; Carrasquillo, Jorge A.; Paik, Chang H. E-mail: cpaik@mail.cc.nih.gov

    2002-02-01

    This study was undertaken to improve the renal clearance and tumor targeting properties of {sup 99m}Tc-labeled humanized anti-Tac (HuTac) monoclonal antibody Fab fragments using two chemical approaches: 1) labeling with a renal secretion agent {sup 99m}Tc-mercaptoacetyltriglycine (MAG3) and 2) lowering its isoelectric point (pI) by acylation. HuTac Fab (3.3 mg/mL) was reacted with a trifluorophenyl ester (TFP) of {sup 99m}Tc-MAG3 alone or was additionally reacted with TFP-glycolate to reduce the pI. In Balb/c mice, {sup 99m}Tc-MAG3-Fab (pI>9.3) rapidly accumulated in the kidneys (177% injected dose [ID]/g at 15 min) and then gradually cleared out of the kidneys. In contrast, the glycolation (pI 4.6{approx}6.6) drastically reduced the renal uptake (31% ID/g) and also the whole-body retention (82% ID vs 101% for the nonglycolated) at 15 min, indicating that the glycolated {sup 99m}Tc-MAG3-Fab (pI 4.6{approx}6.6) was rapidly excreted. The glycolated remained in the blood longer than the nonglycolated (1.2% vs 0.3% ID/g at 360 min), but this effect was less drastic than the effect shown on the renal uptake. In nude mice bearing receptor-positive (ATAC4) tumors, the glycolated {sup 99m}Tc-MAG3-Fab increased the peak tumor uptake to 14.8% ID/g from 8.3% ID/g for {sup 99m}Tc-MAG3-Fab, whereas the glycolation resulted in a drastic reduction of the renal uptake at 15 min. We demonstrated that the renal clearance and the tumor targeting of Fab could be optimized by chemical modifications.

  15. 乙二胺四乙酸二酐对草酸脱羧酶的修饰改性%Chemical modification of oxalate decarboxylase with ethylenediaminetetraacetic dianhydride

    Institute of Scientific and Technical Information of China (English)

    贺俊斌; 林日辉; 龙寒; 巫佳; 蔡杏华; 杨颖; 陈盛峰

    2016-01-01

    为提高草酸脱羧酶(Oxdc)在预防治疗泌尿系结石症方面的稳定性和应用性能,采用乙二胺四乙酸二酐(EDTAD)对Oxdc进行化学修饰,并初步优化了修饰条件:当修饰反应时间为8 h、EDTAD/Oxdc的摩尔比为50:1、反应 pH 为7.0、反应温度为37℃时,修饰率为71.91%,酶活回收率为75.42%。聚丙烯酰胺凝胶电泳(SDS-PAGE)和超高效液相色谱-质谱(UPLC-MS)联用分析证明Oxdc和EDTAD共价结合成功。紫外-可见吸收光谱(UV)和圆二色性光谱(CD)分析结果表明,修饰后Oxdc的空间结构发生了一定程度的改变。同时,部分酶学性质研究表明,经EDTAD修饰后的Oxdc较游离的Oxdc,最适pH向碱性方向偏移了约1.5个单位,耐热性和耐胰蛋白酶酶解的能力均显著增强。此外,修饰后的 Oxdc 在草酸钙上的吸附量明显提高。结果说明修饰后的Oxdc的稳定性显著增强,应用性能有所改善。%In order to improve the stability and application performance of oxalate decarboxylase (Oxdc) in the prevention and treatment of urinary calculi, chemical modification of Oxdc with ethylenediaminetetraacetic dianhydride (EDTAD) was investigated. The results of single-factor experiment showed that the extent of modification and the recovery rate of the enzymatic activity were 71.91% and 75.42%, respectively, when the reaction time was 8 h, the molar ratio of EDTAD/Oxdc was 50:1, pH 7.0, and the temperature was 37℃. The analysis results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS) indicated that Oxdc and EDTAD have been covalently bound. The ultraviolet-visible spectrum (UV) and circular dichroic (CD) measurement showed that the structure and conformation of Oxdc were tinily altered after modification by EDTAD. The enzymology changes of Oxdc were also analyzed, the results showed the

  16. Effects of Surface Modification of Nanodiamond Particles for Nucleation Enhancement during Its Film Growth by Microwave Plasma Jet Chemical Vapour Deposition Technique

    Directory of Open Access Journals (Sweden)

    Chii-Ruey Lin

    2014-01-01

    Full Text Available The seedings of the substrate with a suspension of nanodiamond particles (NDPs were widely used as nucleation seeds to enhance the growth of nanostructured diamond films. The formation of agglomerates in the suspension of NDPs, however, may have adverse impact on the initial growth period. Therefore, this paper was aimed at the surface modification of the NDPs to enhance the diamond nucleation for the growth of nanocrystalline diamond films which could be used in photovoltaic applications. Hydrogen plasma, thermal, and surfactant treatment techniques were employed to improve the dispersion characteristics of detonation nanodiamond particles in aqueous media. The seeding of silicon substrate was then carried out with an optimized spin-coating method. The results of both Fourier transform infrared spectroscopy and dynamic light scattering measurements demonstrated that plasma treated diamond nanoparticles possessed polar surface functional groups and attained high dispersion in methanol. The nanocrystalline diamond films deposited by microwave plasma jet chemical vapour deposition exhibited extremely fine grain and high smooth surfaces (~6.4 nm rms on the whole film. These results indeed open up a prospect of nanocrystalline diamond films in solar cell applications.

  17. Chemical modification of paclitaxel (Taxol) reduces P-glycoprotein interactions and increases permeation across the blood-brain barrier in vitro and in situ.

    Science.gov (United States)

    Rice, Antonie; Liu, Yanbin; Michaelis, Mary Lou; Himes, Richard H; Georg, Gunda I; Audus, Kenneth L

    2005-02-10

    The purpose of this work was to introduce a chemical modification into the paclitaxel (Taxol) structure to reduce interactions with the product of the multidrug resistant type 1 (MDR1) gene, P-glycoprotein (Pgp), resulting in improved blood-brain barrier (BBB) permeability. Specifically, a taxane analogue, Tx-67, with a succinate group added at the C10 position of Taxol, was synthesized and identified as such a candidate. In comparison studies, Tx-67 had no apparent interactions with Pgp, as demonstrated by the lack of enhanced uptake of rhodamine 123 by brain microvessel endothelial cells (BMECs) in the presence of the agent. By contrast, Taxol exposure substantially enhanced rhodamine 123 uptake by BMECs through inhibition of Pgp. The transport across BMEC monolayers was polarized for both Tx-67 and Taxol with permeation in the apical to basolateral direction greater for Tx-67 and substantially reduced for Taxol relative to basolateral to apical permeation. Taxol and cyclosporin A treatments also did not enhance Tx-67 permeation across BMEC monolayers. In an in situ rat brain perfusion study, Tx-67 was demonstrated to permeate across the BBB at a greater rate than Taxol. These results demonstrate that the Taxol analogue Tx-67 had a reduced interaction with Pgp and, as a consequence, enhanced permeation across the blood-brain barrier in vitro and in situ.

  18. Modification of chemical properties of cell walls by silicon and its role in regulation of the cell wall extensibility in oat leaves.

    Science.gov (United States)

    Hossain, Mohammad Talim; Soga, Kouichi; Wakabayashi, Kazuyuki; Kamisaka, Seiichiro; Fujii, Shuhei; Yamamoto, Ryoichi; Hoson, Takayuki

    2007-04-01

    Effects of silicon on the mechanical and chemical properties of cell walls in the second leaf of oat (Avena sativa L.) seedlings were investigated. The cell wall extensibility in the basal region of the second leaf was considerably higher than that in the middle and subapical regions. Externally applied silicon increased the cell wall extensibility in the basal region, but it did not affect the extensibility in the middle and subapical regions. The amounts of cell wall polysaccharides and phenolic compounds, such as diferulic acid (DFA) and ferulic acid (FA), per unit length were lower in the basal region than in the middle and subapical regions of the leaf, and silicon altered these amounts in the basal region. In this region, silicon decreased the amounts of matrix polymers and cellulose per unit length and of DFA and FA, both per unit length and unit matrix polymer content. Silicon treatment also lowered the activity of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) in the basal region. In contrast, the amount of silicon in cell walls increased in response to silicon treatment in three regions. These results suggest that in the basal region, silicon reduces the net wall mass and the formation of phenolic acid-mediated cross-linkages between wall polysaccharides. Such modifications of wall architecture may be responsible for the silicon-induced increase in the cell wall extensibility in oat leaves.

  19. 卡拉胶的生物活性及分子修饰研究进展%Research Progress on Biological Activity and Chemical Modification of Carrageenan

    Institute of Scientific and Technical Information of China (English)

    田秀芳; 李平

    2012-01-01

    Carrageenan,as a family of sulfated polysaccharides with unique structure,had many kinds of biological activity.However,its application in biomedicine field was limited because of large molecular weight.Research on the biological activity of carrageenan in antivirus,antitumor and anticoagulant were synopsis introduced,emphasizing to introduce the research progress on the chemical modification and derivatives of carrageenan.%卡拉胶作为一种结构独特的硫酸多糖,具有多种生物活性,但因分子量过大,使其在生物医药领域的应用受到限制。文章简要介绍了近年来有关卡拉胶抗病毒、抗肿瘤、抗凝血等生物活性的研究,进一步介绍了卡拉胶分子修饰及其衍生物生物活性的研究进展。

  20. Can Small Chemical Modifications of Natural Pan-inhibitors Modulate the Biological Selectivity? The Case of Curcumin Prenylated Derivatives Acting as HDAC or mPGES-1 Inhibitors.

    Science.gov (United States)

    Iranshahi, Mehrdad; Chini, Maria Giovanna; Masullo, Milena; Sahebkar, Amirhossein; Javidnia, Azita; Chitsazian Yazdi, Mahsa; Pergola, Carlo; Koeberle, Andreas; Werz, Oliver; Pizza, Cosimo; Terracciano, Stefania; Piacente, Sonia; Bifulco, Giuseppe

    2015-12-24

    Curcumin, or diferuloylmethane, a polyphenolic molecule isolated from the rhizome of Curcuma longa, is reported to modulate multiple molecular targets involved in cancer and inflammatory processes. On the basis of its pan-inhibitory characteristics, here we show that simple chemical modifications of the curcumin scaffold can regulate its biological selectivity. In particular, the curcumin scaffold was modified with three types of substituents at positions C-1, C-8, and/or C-8' [C5 (isopentenyl, 5-8), C10 (geranyl, 9-12), and C15 (farnesyl, 13, 14)] in order to make these molecules more selective than the parent compound toward two specific targets: histone deacetylase (HDAC) and microsomal prostaglandin E2 synthase-1 (mPGES-1). From combined in silico and in vitro analyses, three selective inhibitors by proper substitution at position 8 were revealed. Compound 13 has improved HDAC inhibitory activity and selectivity with respect to the parent compound, while 5 and 9 block the mPGES-1 enzyme. We hypothesize about the covalent interaction of curcumin, 5, and 9 with the mPGES-1 binding site.

  1. Physical-chemical stability of fluorinated III-N surfaces: Towards the understanding of the (0001) AlxGa1-xN surface donor modification by fluorination

    Science.gov (United States)

    Reiner, Maria; Schellander, Josef; Denifl, Günter; Stadtmueller, Michael; Schmid, Michael; Frischmuth, Tobias; Schmid, Ulrich; Pietschnig, Rudolf; Ostermaier, Clemens

    2017-06-01

    Gallium nitride based high electron mobility transistors are widely known for their operational instabilities regarding interface defects to the dielectric. In this paper, we discuss a III-N surface treatment that results in an electrically more defined interface and hence a narrower distribution of electrically present interface states compared to the original, untreated interface. This surface modification is caused by a remote plasma fluorination of the III-N surface. We show that it is a very distinctive surface processing which cannot be reproduced by other plasma techniques or ion implantation. Applying physical and chemical analyses, the fluorination is found to have a remarkable stability towards temperatures up to 700 °C and is also stable in air for up to 180 h. However, an aqueous clean allows the surface to return to its original state. Even though the exact physical origin of the responsible surface donor cannot be inferred, we suggest that fluorine itself might not directly represent the new surface donor but that it rather activates the III-N surface prior to the dielectric deposition or even substitutes and hence reduces the concentration of surface hydroxides.

  2. Comparative Studies on Dyeability with Direct, Acid and Reactive Dyes after Chemical Modification of Jute with Mixed Amino Acids Obtained from Extract of Waste Soya Bean Seeds

    Science.gov (United States)

    Bhaumik, Nilendu Sekhar; Konar, Adwaita; Roy, Alok Nath; Samanta, Ashis Kumar

    2017-06-01

    Jute fabric was treated with mixed natural amino acids obtained from waste soya bean seed extract for chemical modification of jute for its cataionization and to enhance its dyeability with anionic dyes (like direct, reactive and acid dye) as well enabling soya modified jute for salt free dyeing with anionic reactive dyes maintaining its eco-friendliness. Colour interaction parameters including surface colour strength were assessed and compared for both bleached and soya-modified jute fabric for reactive dyeing and compared with direct and acid dye. Improvement in K/S value (surface colour strength) was observed for soya-modified jute even in absence of salt applied in dye bath for reactive dyes as well as for direct and acid dyes. In addition, reactive dye also shows good dyeability even in acid bath in salt free conditions. Colour fastness to wash was evaluated for bleached and soya-modified jute fabric after dyeing with direct, acid and reactive dyes are reported. Treatment of jute with soya-extracted mixed natural amino acids showed anchoring of some amino/aldemine groups on jute cellulosic polymer evidenced from Fourier Transform Infra-Red (FTIR) Spectroscopy. This amino or aldemine group incorporation in bleached jute causes its cationization and hence when dyed in acid bath for reactive dye (instead of conventional alkali bath) showed dye uptake for reactive dyes. Study of surface morphology by Scanning Electron Microscopy (SEM) of said soya-modified jute as compared to bleached jute was studied and reported.

  3. CHEMICALS

    CERN Document Server

    Medical Service

    2002-01-01

    It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546

  4. Enzymatic modification of starch

    DEFF Research Database (Denmark)

    Jensen, Susanne Langgård

    substrate, and granular products were only obtained at low hydration of the starch. Hence, limiting hydration and gelatinization by using low-phosphate starch and high substrate oncentration was required for obtaining these products. Also high BE activity was a requirement and could partly compensate...... exclusively been conducted on gelatinized starch. This study provides a new concept for transferase-based modification of starches in granular state.......In the food industry approaches for using bioengineering are investigated as alternatives to conventional chemical and physical starch modification techniques in development of starches with specific properties. Enzyme-assisted post-harvest modification is an interesting approach to this, since...

  5. Surface chemical modification of nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Helms, Brett Anthony; Milliron, Delia Jane; Rosen, Evelyn Louise; Buonsanti, Raffaella; Llordes, Anna

    2017-03-14

    Nanocrystals comprising organic ligands at surfaces of the plurality of nanocrystals are provided. The organic ligands are removed from the surfaces of the nanocrystals using a solution comprising a trialkyloxonium salt in a polar aprotic solvent. The removal of the organic ligands causes the nanocrystals to become naked nanocrystals with cationic surfaces.

  6. Structural and chemical modification of Fe-rich smectite associated with microbial Fe-respiration by psychrophilic bacteria in King George Island, West Antarctica

    Science.gov (United States)

    Jung, J.; Kim, J. Y.; Lim, H. S.; Lee, Y. K.; Kim, O. S.; Park, K.; Lee, J.; Yoon, H.; Kim, J. W.

    2015-12-01

    -fixation. Vivianite precipitation suggesting the reductive dissolution of nontronite were observed in 4 months enrichment samples at 4 ℃ and 15 ℃. The present study, therefore, indicates the feasibility of biological effects on chemical/structural modification in clay minerals in cold environment suggesting a new pathway of Fe-supply into the Antarctic Ocean.

  7. Intraoperative simulation of remnant liver function during anatomic liver resection with indocyanine green clearance (LiMON) measurements.

    Science.gov (United States)

    Thomas, Michael N; Weninger, Ernst; Angele, Martin; Bösch, Florian; Pratschke, Sebastian; Andrassy, Joachim; Rentsch, Markus; Stangl, Manfred; Hartwig, Werner; Werner, Jens; Guba, Markus

    2015-06-01

    Post-hepatectomy liver failure (PHLF) is the major cause of death following liver resection. The aim of this study was to evaluate the feasibility of an intraoperative simulation of post-resection liver function. Intraoperative liver function was measured by indocyanine green (ICG) clearance using the LiMON technology. In 20 patients undergoing anatomic liver resection, ICG plasma disappearance rate (PDR (%/min) and ICG retention at 15 min (R15 ) (%) were measured immediately after the induction of anaesthesia (t0 ), after selective arterial and portovenous inflow trial clamping (TC) of the resected liver segments (t1 ), after the completion of resection (t2 ) and before the closure of the abdominal cavity (t3 ). The median baseline (t0 ) PDR was 16.5%/min. Trial clamping of the inflow (t1 ) resulted in a significant reduction in PDR to 10.5%/min. Results under TC were similar to those obtained after resection (t2 ) (median PDR: 10.5%/min). Linear regression modelling showed that post-resection liver volume could be accurately predicted by TC of liver inflow (P < 0.0001), but not by determining the resected liver volume. Simulated post-resection liver function under TC correlated well with PHLF and length of hospital stay. Intraoperative ICG clearance measurements allow real-time monitoring of intraoperative liver function during surgery. Trial clamping of arterial and portovenous inflow accurately predicts immediate post-resection liver function. The intraoperative measurement of liver function and simulation of post-resection liver function may help to avoid PHLF. © 2015 International Hepato-Pancreato-Biliary Association.

  8. The LIM-only protein FHL2 mediates ras-induced transformation through cyclin D1 and p53 pathways.

    Directory of Open Access Journals (Sweden)

    Charlotte Labalette

    Full Text Available BACKGROUND: Four and a half LIM-only protein 2 (FHL2 has been implicated in multiple signaling pathways that regulate cell growth and tissue homeostasis. We reported previously that FHL2 regulates cyclin D1 expression and that immortalized FHL2-null mouse embryo fibroblasts (MEFs display reduced levels of cyclin D1 and low proliferative activity. METHODOLOGY/PRINCIPAL FINDINGS: Here we address the contribution of FHL2 in cell transformation by investigating the effects of oncogenic Ras in FHL2-null context. We show that H-RasV12 provokes cell cycle arrest accompanied by accumulation of p53 and p16(INK4a in immortalized FHL2(-/- MEFs. These features contrast sharply with Ras transforming activity in wild type cell lines. We further show that establishment of FHL2-null cell lines differs from conventional immortalization scheme by retaining functional p19(ARF/p53 checkpoint that is required for cell cycle arrest imposed by Ras. However, after serial passages of Ras-expressing FHL2(-/- cells, dramatic increase in the levels of D-type cyclins and Rb phosphorylation correlates with the onset of cell proliferation and transformation without disrupting the p19(ARF/p53 pathway. Interestingly, primary FHL2-null cells overexpressing cyclin D1 undergo a classical immortalization process leading to loss of the p19(ARF/p53 checkpoint and susceptibility to Ras transformation. CONCLUSIONS/SIGNIFICANCE: Our findings uncover a novel aspect of cellular responses to mitogenic stimulation and illustrate a critical role of FHL2 in the signalling network that implicates Ras, cyclin D1 and p53.

  9. Structural and Chemical Modification of Fe-Rich Smectite Associated with Microbial Fe-Respiration By Psychrophilic Bacteria in King George Island, West Antarctica

    Science.gov (United States)

    Jung, J.; Kim, J.; Lim, H. S.; Yoon, H.; Lee, Y. K.; Park, K.; Lee, J.; Kim, J. W.

    2014-12-01

    Surface soil samples were collected from Antarctic exploration (2010/2011, 2011/2012) at Barton Peninsula, King George Island, West Antarctica to determine the feasible biological alteration of clay minerals in Antarctica where the physical weathering is considered to be a major process. Seven areas (1226-1, 1226-2, 0101-4, 0105-1, 0105-2, 0107-2, 0107-3) from the coast toward the inland were investigated. The duration of exposure of soil samples to the air depending on the retraction of ice to the inland may affect the microbial activity resulting in the biogeochemical mineral alteration. The multiline of techniques for example, X-ray diffraction (XRD), Scanning Electron Microscope (SEM), wet chemistry analysis including the extent of Fe(III) reduction, and batch experiments of microbe-mineral interaction under the low temperature that mimics the Antarctic condition to understand the mechanism of biogeochemical alteration of clay minerals. Clay minerals of smectite, mica, chlorite and kaolinite were detected in the XRD profiles. The variation of relative amount of clay minerals in the regions indicated that the physical/biological alteration might be different depending on the duration of ice retraction. From the batch experiment using Nontronite (NAu-1), moreover, we confirm that Psychrophilic bacteria (Shewanella sp. isolated from King George Island) reduce structural Fe(III) of clay mineral, and occur structural change of smectite at low temperature (4℃ and 15℃). The present study, therefore, would present the feasibility of biological effects on chemical modification through the structural changes in clay mineral in cold environment and suggest a new pathway of Fe-supply into the Antarctic Ocean.

  10. Modification of REE distribution of ordinary chondrites from Atacama (Chile) and Lut (Iran) hot deserts: Insights into the chemical weathering of meteorites

    Science.gov (United States)

    Pourkhorsandi, Hamed; D'Orazio, Massimo; Rochette, Pierre; Valenzuela, Millarca; Gattacceca, Jérôme; Mirnejad, Hassan; Sutter, Brad; Hutzler, Aurore; Aboulahris, Maria

    2017-09-01

    The behavior of rare earth elements (REEs) during hot desert weathering of meteorites is investigated. Ordinary chondrites (OCs) from Atacama (Chile) and Lut (Iran) deserts show different variations in REE composition during this process. Inductively coupled plasma-mass spectrometry (ICP-MS) data reveal that hot desert OCs tend to show elevated light REE concentrations, relative to OC falls. Chondrites from Atacama are by far the most enriched in REEs and this enrichment is not necessarily related to their degree of weathering. Positive Ce anomaly of fresh chondrites from Atacama and the successive formation of a negative Ce anomaly with the addition of trivalent REEs are similar to the process reported from Antarctic eucrites. In addition to REEs, Sr and Ba also show different concentrations when comparing OCs from different hot deserts. The stability of Atacama surfaces and the associated old terrestrial ages of meteorites from this region give the samples the necessary time to interact with the terrestrial environment and to be chemically modified. Higher REE contents and LREE-enriched composition are evidence of contamination by terrestrial soil. Despite their low degrees of weathering, special care must be taken into account while working on the REE composition of Atacama meteorites for cosmochemistry applications. In contrast, chondrites from the Lut desert show lower degrees of REE modification, despite significant weathering signed by Sr content. This is explained by the relatively rapid weathering rate of the meteorites occurring in the Lut desert, which hampers the penetration of terrestrial material by forming voluminous Fe oxide/oxyhydroxides shortly after the meteorite fall.

  11. 水飞蓟宾及其类似物的化学修饰研究进展%Advances in Chemical Modification of Silybin and Its Analogues

    Institute of Scientific and Technical Information of China (English)

    刘伟; 余燕影; 曹树稳

    2012-01-01

    On the basis of flavonoid lead compounds with biological activity,studying the relationship between structures and bioavailability and modifying their structures is an important means of innovation of new drugs. Silybum marianum ( L. ) Gaertn. Has been used for more than 2000 years to treat liver and gallbladder disorders. Silybin, derived from the milk thistle plant, has received considerable attention due to its hepatoprotective, anti-inflammatory and anticancer effects,however,the bioavailability and therapeutic efficiency of silybin is rather limited by its very low solubility. To solve this problem, silybin is modified or altered via various chemical and physical methods by domestic and foreign scholars,and have obtained a certain achievement. In this paper,the chemical modification of silybin and its analogues in recent years are reviewed.%以天然黄酮类化合物为活性先导物,研究其化学结构与生物活性的关系,进而进行化学修饰研究,是目前创新药物的一条重要思路.药用植物水飞蓟用来治疗肝胆疾病已有2000多年的历史,水飞蓟宾作为水飞蓟素的主要活性成分具有保肝、抗炎和抗癌等活性而备受人们关注,但由于水飞蓟宾极低的溶解性极大地限制了其生物利用度.为此,国内外学者通过化学和物理等方法对其进行修饰和改造,并取得了一定的成果.本文就近10年来水飞蓟宾及其类似物的化学修饰研究进行综述.

  12. Isolation and characterization of total volatile components from leaves of citrus limon linn.

    Directory of Open Access Journals (Sweden)

    Kadambari Tomer

    2010-01-01

    Full Text Available The isolation of the essential oil of whole fresh leaves of Citrus lemon by steam distillation is described. The chemical composition of the oil was investigated by means of Gas-Liquid Chromatography (GLC, Column Chromatography (CC and coupled Gas Chromatography-Mass Spectrometry (GC-MS. The 27 most important volatile components were identified. The volatile components were identified by comparing their retention times of GC chromatograph with those of literature. Further identification was done by GC- MS. The components of the oil, percentage of each constituent, their RI values and their Eight Peak Index were also summarized and reviewed with standard available literature.

  13. ISOLATION AND CHARACTERIZATION OF TOTAL VOLATILE COMPONENTS FROM LEAVES OF CITRUS LIMON LINN.

    Directory of Open Access Journals (Sweden)

    Vijendra Singh

    2010-03-01

    Full Text Available The isolation of the essential oil of whole fresh leaves of Citrus lemon by steamdistillation is described. The chemical composition of the oil was investigated by meansof Gas-Liquid Chromatography (GLC, Column Chromatography (CC and coupled GasChromatography-Mass Spectrometry (GC-MS. The 27 most important volatilecomponents were identified. The volatile components were identified by comparing theirretention times of GC chromatograph with those of literature. Further identification wasdone by GC- MS. The components of the oil, percentage of each constituent, their RIvalues and their Eight Peak Index were also summarized and reviewed with standardavailable literature.

  14. Identification, synthesis, and characterization of novel sulfur-containing volatile compounds from the in-depth analysis of Lisbon lemon peels (Citrus limon L. Burm. f. cv. Lisbon).

    Science.gov (United States)

    Cannon, Robert J; Kazimierski, Arkadiusz; Curto, Nicole L; Li, Jing; Trinnaman, Laurence; Jańczuk, Adam J; Agyemang, David; Da Costa, Neil C; Chen, Michael Z

    2015-02-25

    Lemons (Citrus limon) are a desirable citrus fruit grown and used globally in a wide range of applications. The main constituents of this sour-tasting fruit have been well quantitated and characterized. However, additional research is still necessary to better understand the trace volatile compounds that may contribute to the overall aroma of the fruit. In this study, Lisbon lemons (C. limon L. Burm. f. cv. Lisbon) were purchased from a grove in California, USA, and extracted by liquid-liquid extraction. Fractionation and multidimensional gas chromatography-mass spectrometry were utilized to separate, focus, and enhance unidentified compounds. In addition, these methods were employed to more accurately assign flavor dilution factors by aroma extract dilution analysis. Numerous compounds were identified for the first time in lemons, including a series of branched aliphatic aldehydes and several novel sulfur-containing structures. Rarely reported in citrus peels, sulfur compounds are known to contribute significantly to the aroma profile of the fruit and were found to be aroma-active in this particular study on lemons. This paper discusses the identification, synthesis, and organoleptic properties of these novel volatile sulfur compounds.

  15. Cold pressed versus solvent extracted lemon (Citrus limon L.) seed oils: yield and properties.

    Science.gov (United States)

    Yilmaz, Emin; Güneşer, Buket Aydeniz

    2017-06-01

    During the processing of lemon fruit, a large quantity of seeds is produced as a by-product. These seeds contain valuable components; therefore, required to be evaluated. This study aimed to compare the cold pressed with hexane-extracted lemon seed oils and determine their physicochemical and thermal properties. Cold pressing yielded significantly lower oil (36.84%) than hexane extraction (71.29%). In addition, the concentrations of free fatty acids, peroxides, and p-anisidine were lower in the cold pressed oil. Cold pressed oil showed higher total phenolics, α-tocopherol and antioxidant capacity. The major fatty acids found in the cold pressed oil were linoleic and palmitic acids, whereas β-sitosterol and campesterol were the dominant sterols. The crystallization and melting temperatures and enthalpies were also elucidated. In conclusion, this study proved that high quality of lemon seed oils can be produced by the cold pressing technique; this oil can be used in industries such as the food, cosmetic or chemical industries.

  16. Effect of thermal and chemical modifications on the mechanical and release properties of paracetamol tablet formulations containing corn, cassava and sweet potato starches as filler-binders

    Directory of Open Access Journals (Sweden)

    Mariam Vbamiunomhene Lawal

    2015-07-01

    Conclusions: Modification of the experimental starches improved the mechanical and release properties of directly compressed paracetamol tablet formulations. Thus, they can be developed for use as pharmaceutical excipients in specific formulations.

  17. Functionalised Polymers by Surface Modification

    Institute of Scientific and Technical Information of China (English)

    Jon-Paul Griffiths; M. G. Moloney

    2005-01-01

    @@ 1Introduction Surface-active polymers are of substantial importance in many diverse aspects of modern technology, with applications ranging from solid phase chemical synthesis related to drug discovery and chemical catalysis to biocompatible/bioactive medical implants and prostheses, and to surface-modified fabrics. Whilst there are a number of existing physical (e. g. corona or plasma discharge, ion beam irradiation[1] ) and chemical (e. g.silanisation, oxidation, chlorination, acylation and quaternisation[2-4]) methods for the surface modification of polymers, the frequent requirement for significant infrastructure, harsh reaction conditions, and limitation to specific polymer types (e. g. polybutadiene[5] ), which must possess suitable chemical functionality capable of direct modification, led us to consider alternative chemical methods. Desirable was an alternative that would be amenable to a large range of polymers, permitting direct chemical modification under mild conditions and using inexpensive reagents.

  18. Chemical modification of PDMS surface without impacting the viscoelasticity: Model systems for a better understanding of elastomer/elastomer adhesion and friction

    OpenAIRE

    DIRANY, Mohammed; DIES, Laëtitia; Restagno, Frédéric; Léger, Liliane; Poulard, Christophe; MIQUELARD-GARNIER, Guillaume

    2015-01-01

    The influence of both viscoelastic and interfacial parameters on the surface properties of elastomers is difficult to study. Here, we describe a simple route to achieve surface modification of PDMS without impacting the viscoelastic properties of the bulk. PEG modified PDMS surfaces were synthesized by two step surface modification based on hydrosilylation. The covalent grafting of PEG on the surface has been evidenced by AFM and ATR-FTIR, and its effect on the hydrophilicity characterized by...

  19. Preparation of an antitumor and antivirus agent: chemical modification of α-MMC and MAP30 from Momordica Charantia L. with covalent conjugation of polyethyelene glycol.

    Science.gov (United States)

    Meng, Yao; Liu, Shuangfeng; Li, Juan; Meng, Yanfa; Zhao, Xiaojun

    2012-01-01

    Alpha-momorcharin (α-MMC) and momordica anti-HIV protein (MAP30) derived from Momordica charantia L. have been confirmed to possess antitumor and antivirus activities due to their RNA-N-glycosidase activity. However, strong immunogenicity and short plasma half-life limit their clinical application. To solve this problem, the two proteins were modified with (mPEG)(2)-Lys-NHS (20 kDa). In this article, a novel purification strategy for the two main type I ribosome-inactivating proteins (RIPs), α-MMC and MAP30, was successfully developed for laboratory-scale preparation. Using this dramatic method, 200 mg of α-MMC and about 120 mg of MAP30 was obtained in only one purification process from 200 g of Momordica charantia seeds. The homogeneity and some other properties of the two proteins were assessed by gradient SDS-PAGE, electrospray ionization quadruple mass spectrometry, and N-terminal sequence analysis as well as Western blot. Two polyethylene glycol (PEG)ylated proteins were synthesized and purified. Homogeneous mono-, di-, or tri-PEGylated proteins were characterized by matrix-assisted laser desorption ionization-time of flight mass spectrometry. The analysis of antitumor and antivirus activities indicated that the serial PEGylated RIPs preserved moderate activities on JAR choriocarcinoma cells and herpes simplex virus-1. Furthermore, both PEGylated proteins showed about 60%-70% antitumor and antivirus activities, and at the same time decreased 50%-70% immunogenicity when compared with their unmodified counterparts. α-MMC and MAP30 obtained from this novel purification strategy can meet the requirement of a large amount of samples for research. Their chemical modification can solve the problem of strong immunogenicity and meanwhile preserve moderate activities. All these findings suggest the potential application of PEGylated α-MMC and PEGylated MAP30 as antitumor and antivirus agents. According to these results, PEGylated RIPs can be constructed with

  20. Ubiquitin modifications

    OpenAIRE

    Swatek, Kirby N.; Komander, David

    2016-01-01

    Protein ubiquitination is a dynamic multifaceted post-translational modification involved in nearly all aspects of eukaryotic biology. Once attached to a substrate, the 76-amino acid protein ubiquitin is subjected to further modifications, creating a multitude of distinct signals with distinct cellular outcomes, referred to as the 'ubiquitin code'. Ubiquitin can be ubiquitinated on seven lysine (Lys) residues or on the N-terminus, leading to polyubiquitin chains that can encompass complex top...

  1. Comparative Study of Surface Chemical Composition and Oxide Layer Modification upon Oxygen Plasma Cleaning and Piranha Etching on a Novel Low Elastic Modulus Ti25Nb21Hf Alloy

    Science.gov (United States)

    Paredes, Virginia; Salvagni, Emiliano; Rodríguez-Castellón, Enrique; Manero, José María

    2017-08-01

    Metals are widely employed for many biological artificial replacements, and it is known that the quality and the physical/chemical properties of the surface are crucial for the success of the implant. Therefore, control over surface implant materials and their elastic moduli may be crucial to avoid undesired effects. In this study, surface modification upon cleaning and activation of a low elastic modulus Ti alloy (Ti25Hf21Nb) was investigated. Two different methods, oxygen plasma (OP) cleaning and piranha (PI) solution, were studied and compared. Both surface treatments were effective for organic contaminant removal and to increase the Ti-oxide layer thickness rather than other metal-oxides present at the surface, which is beneficial for biocompatibility of the material. Furthermore, both techniques drastically increased hydrophilicity and introduced oxidation and hydroxylation (OH)-functional groups at the surface that may be beneficial for further chemical modifications. However, these treatments did not alter the surface roughness and bulk material properties. The surfaces were fully characterized in terms of surface roughness, wettability, oxide layer composition, and hydroxyl surface density through analytical techniques (interferometry, X-ray photoelectron spectroscopy (XPS), contact angle, and zinc complexation). These findings provide essential information when planning surface modifications for cleanliness, oxide layer thickness, and surface hydroxyl density, as control over these factors is essential for many applications, especially in biomaterials.

  2. Effect of Amino Acid Residue and Oligosaccharide Chain Chemical Modifications on Spectral and Hemagglutinating Activity of Millettia dielsiana Harms. ex Diels. Lectin

    Institute of Scientific and Technical Information of China (English)

    Shun GAO; Jie AN; Chuan-Fang WU; Ying GU; Fang CHEN; Yuan YU; Qia-Qing WU; Jin-Ku BAO

    2005-01-01

    The effects of modifying the carbohydrate chain and amino acids on the conformation and activity of Millettia dielsiana Harms. ex Diels. lectin (MDL) were studied by hemagglutination, fluorescence and circular dichroism analysis. The modification of tryptophan residues led to a compete loss of hemagglutinating activity; however, the addition of mannose was able to prevent this loss of activity. The results indicate that two tryptophan residues are involved in the carbohydrate-binding site. Modifications of the carboxyl group residues produced an 80% loss of activity, but the presence of mannose protected against the modification. The results suggest that the carboxyl groups of aspartic and glutamic acids are involved in the carbohydrate-binding site of the lectin. However, oxidation of the carbohydrate chain and modification of the histidine and arginine residues did not affect the hemagglutinating activity of MDL. Fluorescence studies of MDL indicate that tryptophan residues are present in a relatively hydrophobic region, and the binding of mannose to MDL could quench tryptophan fluorescence without any change in λmax. The circular dichroism spectrum showed that all of these modifications affected the conformation of the MDL molecule to different extents, except the modification of arginine residues. Fluorescence quenching showed that acrylamide and iodoacetic acids are able to quench 77% and 98% of the fluorescence of tryptophan in MDL, respectively.However, KI produced a barely perceptible effect on the fluorescence of MDL, even when the concentration of I- was 0.15 M. This demonstrates that most of tryptophan residues are located in relatively hydrophobic or negatively charged areas near the surface of the MDL molecule.

  3. ReportSites - A Computational Method to Extract Positional and Physico- Chemical Information from Large-Scale Proteomic Post-Translational Modification Datasets

    DEFF Research Database (Denmark)

    Edwards, Alistair; Edwards, Gregory; Larsen, Martin Røssel

    2012-01-01

    environment of a particular amino acid residue, or group of residues, within large-scale proteomic data sets, using peptide sequences characterized by mass spectrometry combined with protein sequence databases. The program is ideally suited to distilling regional and spatial information from post...... descriptive factors (such as modification of binding domains or protein structure).This makes it a versatile tool with the potential to aid in revealing new aspects of post-translational modification distribution. The code is freely available from the authors upon request and is accessible online....

  4. "Repellent Effect of Extracts and Essential Oils of Citrus limon (Rutaceae and Melissa officinalis (Labiatae Against Main Malaria Vector, Anopheles stephensi (Diptera: Culicidae"

    Directory of Open Access Journals (Sweden)

    "MA Oshaghi

    2003-10-01

    Full Text Available Repellet effect of extracts and essential oils of Citrus limon (L. Burm.F., (lemon and Melissa officinalis, (balm were evaluated against Anopheles stephensi in laboratory on animal and human and compared with synthetic repellent, N,Ndiethyl- 3-methylbenzamide (Deet as a standard. Results of statistical analysis revealed significant differences between oils and extracts (P< 0.05 against the tested species, thus oils were more effective than extracts. There was no significant difference between Deet and lemon oil, whereas the difference between lemon and melissa oils was significant. Relative efficacy of lemon oil to Deet was 0.88 whereas it was 0.71 for melissa oil. The results were found marginally superior in repellency for animals than human. Due to advantages of botanic compounds to synthetic compounds we recommend lemon essential oil as an effective alternative to Deet with potential as a means of personal protection against mosquito vectors of disease.

  5. Preparation of an antitumor and antivirus agent: chemical modification of α-MMC and MAP30 from Momordica Charantia L. with covalent conjugation of polyethyelene glycol

    Directory of Open Access Journals (Sweden)

    Meng Y

    2012-06-01

    virus-1. Furthermore, both PEGylated proteins showed about 60%–70% antitumor and antivirus activities, and at the same time decreased 50%–70% immunogenicity when compared with their unmodified counterparts.Conclusion/significance: α-MMC and MAP30 obtained from this novel purification strategy can meet the requirement of a large amount of samples for research. Their chemical modification can solve the problem of strong immunogenicity and meanwhile preserve moderate activities. All these findings suggest the potential application of PEGylated α-MMC and PEGylated MAP30 as antitumor and antivirus agents. According to these results, PEGylated RIPs can be constructed with nanomaterials to be a targeting drug that can further decrease immunogenicity and side effects. Through nanotechnology we can make them low-release drugs, which can further prolong their half-life period in the human body.Keywords: ribosome-inactivating proteins, alpha-momorcharin, momordica anti-HIV protein, antitumor, antivirus, (mPEG2-Lys-NHS (20 kDa, immunogenicity

  6. Pin-point chemical modification of RNA with diverse molecules through the functionality transfer reaction and the copper-catalyzed azide-alkyne cycloaddition reaction.

    Science.gov (United States)

    Onizuka, Kazumitsu; Shibata, Atsushi; Taniguchi, Yosuke; Sasaki, Shigeki

    2011-05-07

    The internal modification of RNA has been successfully achieved by the functionality transfer reaction (FTR) and following click chemistry with diverse azide compounds. The benefits of the FTR have been demonstrated by its specificity, rapidity, broad applicability, and procedure simplicity. © The Royal Society of Chemistry 2011

  7. Effect of surface topological structure and chemical modification of flame sprayed aluminum coatings on the colonization of Cylindrotheca closterium on their surfaces

    Science.gov (United States)

    Chen, Xiuyong; He, Xiaoyan; Suo, Xinkun; Huang, Jing; Gong, Yongfeng; Liu, Yi; Li, Hua

    2016-12-01

    Biofouling is one of the major problems for the coatings used for protecting marine infrastructures during their long-term services. Regulation in surface structure and local chemistry is usually the key for adjusting antifouling performances of the coatings. In this study, flame sprayed multi-layered aluminum coatings with micropatterned surfaces were constructed and the effects of their surface structure and chemistry on the settlement of typical marine diatoms were investigated. Micropatterned topographical morphology of the coatings was constructed by employing steel mesh as a shielding plate during the coating deposition. A silicone elastomer layer for sealing and interconnection was further brush-coated on the micropatterned coatings. Additional surface modification was made using zwitterionic molecules via DOPA linkage. The surface-modified coatings resist effectively colonization of Cylindrotheca closterium. This is explained by the quantitative examination of a simplified conditioning layer that deteriorated adsorption of bovine calf serum proteins on the zwitterionic molecule-treated samples is revealed. The colonization behaviors of the marine diatoms are markedly influenced by the micropatterned topographical morphology. Either the surface micropatterning or the surface modification by zwitterionic molecules enhances antimicrobial ability of the coatings. However, the combined micropatterned structure and zwitterionic modification do not show synergistic effect. The results give insight into anti-corrosion/fouling applications of the modified aluminum coatings in the marine environment.

  8. Chemical modification of HTPB for application as polymeric additives for diesel fuel. 1 - phenyl ethers; Modificacao quimicado PBLH para aplicacao como aditivos polimericos para oleo diesel. 1. eteres fenilicos

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, Agne R.; Prezibella, Alysson M.; Ferraz, Fernando A.; Soldi, Rafael A.; Oliveira, Angelo R.S.; Cesar-Oliveira, Maria Aparecida F. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Quimica. Lab. de Polimeros Sinteticos

    2007-07-01

    The petroleum industry faces several problems related to the crystallization of paraffins, in petroleum and its derivatives, with the reduction of the service temperature. To solve this problem polymeric additives are used, of which the esters have been enough studied in several areas of the world, except in Brazil. In this work, this class of pour point depressant additives it was obtained through the chemical modification of Hydroxyl Terminate Polybutadiene (HTPB) that present a hydrocarbon chemical structure containing one double bound in each repetitive unit and hydroxyl groups of the primary and secondary allylic types - functional groups potentially reactive. The obtained products were characterized by Fourier transformed infrared spectroscopy and nuclear magnetic resonance, and they are being tested as additive for the pour point reduction of a diesel oil samples (REPAR-PETROBRAS). (author)

  9. 天然斜发沸石的氨氮改性吸附与化学再生%Modification and chemical regeneration of natural clinoptilolite for ammonium nitrogen adsorption

    Institute of Scientific and Technical Information of China (English)

    张新颖; 余杨波; 王美银; 许冉冉; 李杰

    2016-01-01

    Modification and chemical regeneration methods were adopted to explore the optimum condition of natural clinoptilolite for ammonium nitrogen adsorption.Salt modification,thermal modification and organic modification results indicated that inorganic salt (NaCl) solution modification method was the best and the ammonium adsorption capacity increased nearly 20%,with 1 mol· L-1 NaCl.Thermal modification method did not improve the ammonia nitrogen adsorption capacity significantly.On the contrary,the structure of clinoptilolite was destroyed by high temperature.When sodium dodecyl benzene sulfonate modification method was used,there were new positive ion adsorption sites on the surface of modified clinoptilolite and its ammonium adsorption capacity increased.However,cetyl trimethyl ammonium bromide modification increased negative ion adsorption sites,which were ammonium repellent,and decreased the ammonium adsorption capacity.Chemical regeneration tests showed that,KCl solution was the best regeneration method of ammonium saturated clinoptilolite,with suitable KCl concentration of 0.1-0.2 mol· L-1.KClmodified clinoptilolite which were remodified by NaCl solution might have longer life cycle and higher adsorption capacity than before.%本文采用改性与化学再生方法,探索天然斜发沸石对氨氮吸附的最佳改性及化学再生条件.无机盐改性、热改性、有机改性试验结果表明,最佳改性方法为无机盐NaCl法,改性沸石吸附量较天然沸石提升了近20%,最佳NaCl浓度为1 mol·L-1;热改性法不能显著提高沸石的氨氮吸附容量,相反高温会破坏其结构;十二烷基苯磺酸钠改性法可以使改性沸石在其表面形成了新的阳离子吸附点,使其吸附性能提升;而十六烷基三甲基溴化铵改性沸石表面形成的是阴离子吸附点,对带正电的NH4+会产生排斥,导致其吸铵性能下降.化学再生试验表明,KCl溶液对铵饱和沸石的再生效果最

  10. Wood Chemical Modification: the State of the Art of Technologies and Commercialization%木材化学功能改良技术进展与产业现状

    Institute of Scientific and Technical Information of China (English)

    谢延军; 符启良; 王清文; 王海刚

    2012-01-01

    Wood modification is the technologies with which the properties of wood are permanently altered by heating at high temperatures or reacting with low molecular weight monomers or oligomers. The specific properties of wood are consequently improved and certain new characteristics imparted due to the modification. The modified woods can resultantly serve for a longer term compared to the non-modified ones. As a result, the tension due to the lack of wood resource can be reduced. In this paper, the development and the state of the art of wood modification are systematically reviewed. The typical modification technologies such as thermal treatment, acetylation, treatments with N-methylol compounds, furfurylation, and impregnation with thermoset resins are introduced. The effects of chemical modification on the properties of the resulting wood are analyzed and the commercialization status of modified products presented. Consequently, an outlook for the development trends and challenges of wood modification is given.%木材化学功能改良旨在通过物理或化学的方法(主要是利用热或具有反应活性官能团的低分子单体/低聚体),对木材细胞壁成分进行永久改变和/或对木材细胞腔进行物理填充,由此改善木材的各项物理力学性能,并赋予其特定的新功能,提高木材的附加值,延长木材的使用寿命,从而实现木材的高效节约利用,缓解木材资源紧张的局面.对国内、国际上木材功能改良技术的发展和现状进行系统回顾,介绍炭化处理、乙酰化、氮甲氧基树脂处理、糠醇处理、热固性树脂处理等典型改性技术的原理、产品性能的优缺点及其商业化现状,展望木材功能改良技术发展面临的机遇与挑战.

  11. Inactivation of glyceraldehyde-3-phosphate dehydrogenase by fumarate in diabetes: formation of S-(2-succinyl)cysteine, a novel chemical modification of protein and possible biomarker of mitochondrial stress.

    Science.gov (United States)

    Blatnik, Matthew; Frizzell, Norma; Thorpe, Suzanne R; Baynes, John W

    2008-01-01

    (2-succinyl)cysteine (2SC) is formed by a Michael addition reaction of the Krebs cycle intermediate, fumarate, with cysteine residues in protein. We investigated the role of fumarate in chemical modification and inhibition of the sulfhydryl enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), in vitro and in tissues of diabetic rats. GAPDH was incubated with fumarate in PBS to assess effects of fumarate on enzyme activity in vitro. Sites of 2SC formation were determined by analysis of tryptic peptides by high-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry. 2SC and fumarate in gastrocnemius muscle of control and streptozotocin-induced diabetic rats were measured by liquid chromatography/tandem mass spectrometry and by gas chromatography/mass spectrometry, respectively. GAPDH was isolated from muscle by immunoprecipitation, and sites of modification of GAPDH were determined by mass spectrometry analysis. 2SC was found, both in vitro and in vivo, about equally at active-site Cys-149 and nucleophilic Cys-244. Inactivation of GAPDH by fumarate in vitro correlated with formation of 2SC. In diabetic compared with control rats, fumarate and 2SC concentration increased approximately fivefold, accompanied by an approximately 25% decrease in GAPDH specific activity. The fractional modification of GAPDH by 2SC was significantly increased in diabetic versus control animals, consistent with the decreased specific activity of GAPDH in muscle of diabetic animals. Fumarate contributes to inactivation of GAPDH in diabetes. 2SC may be a useful biomarker of mitochondrial stress in diabetes. Modification of GAPDH and other enzymes and proteins by fumarate may contribute to the metabolic changes underlying the development of diabetes complications.

  12. Advances in chemical modification of xylan and application of their derivatives%木聚糖的化学修饰及其衍生物的应用研究进展

    Institute of Scientific and Technical Information of China (English)

    李和平; 何利霞

    2009-01-01

    在简要介绍木聚糖的结构特点及反应性的基础上,对木聚糖的醚化、酯化、氧化、交联、复合等化学修饰及其衍生物的合成研究现状,应用领域及发展趋势进行了重点评述,从合成路线、特征结构、非常规木聚糖衍生物、物理化学性质、生物活性、构效关系等方面依次对不同类型的修饰产物即木聚糖衍生物进行了分类介绍.此外,还简要叙述了木聚糖的功能化修饰如木聚糖微粒子和纳米粒子,聚合物磁性粒子的制备原理与工艺进展.指出了木聚糖及其衍生物在新领域的应用和今后的研究方向.%This review starts with a brief introduction to the structural characteristics of xyaln and its reactivity, then the chemical modifications, the application fields as well as the development trend about its derivatives are discussed. The chemical modifications of xylan include etherization, esterification, oxidation, cross linking and composite preparation. Different types of xylan derivatives are introduced in such aspects as typical synthesis routes, efficient structure characterization, unconventional xylan derivatives, physicochemical properties, biological activity, structure-property relationships and so on. Besides, functionalized modifications of xylan such as the preparation of micro and nanoparticles as well as xylan-coated magnetite microparticles are also described. New application areas and future research directions are discussed also.

  13. Surface etching, chemical modification and characterization of silicon nitride and silicon oxide—selective functionalization of Si3N4 and SiO2

    Science.gov (United States)

    Liu, Li-Hong; Michalak, David J.; Chopra, Tatiana P.; Pujari, Sidharam P.; Cabrera, Wilfredo; Dick, Don; Veyan, Jean-François; Hourani, Rami; Halls, Mathew D.; Zuilhof, Han; Chabal, Yves J.

    2016-03-01

    The ability to selectively chemically functionalize silicon nitride (Si3N4) or silicon dioxide (SiO2) surfaces after cleaning would open interesting technological applications. In order to achieve this goal, the chemical composition of surfaces needs to be carefully characterized so that target chemical reactions can proceed on only one surface at a time. While wet-chemically cleaned silicon dioxide surfaces have been shown to be terminated with surficial Si-OH sites, chemical composition of the HF-etched silicon nitride surfaces is more controversial. In this work, we removed the native oxide under various aqueous HF-etching conditions and studied the chemical nature of the resulting Si3N4 surfaces using infrared absorption spectroscopy (IRAS), x-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), and contact angle measurements. We find that HF-etched silicon nitride surfaces are terminated by surficial Si-F and Si-OH bonds, with slightly subsurface Si-OH, Si-O-Si, and Si-NH2 groups. The concentration of surficial Si-F sites is not dependent on HF concentration, but the distribution of oxygen and Si-NH2 displays a weak dependence. The Si-OH groups of the etched nitride surface are shown to react in a similar manner to the Si-OH sites on SiO2, and therefore no selectivity was found. Chemical selectivity was, however, demonstrated by first reacting the -NH2 groups on the etched nitride surface with aldehyde molecules, which do not react with the Si-OH sites on a SiO2 surface, and then using trichloro-organosilanes for selective reaction only on the SiO2 surface (no reactivity on the aldehyde-terminated Si3N4 surface).

  14. Surface etching, chemical modification and characterization of silicon nitride and silicon oxide--selective functionalization of Si3N4 and SiO2.

    Science.gov (United States)

    Liu, Li-Hong; Michalak, David J; Chopra, Tatiana P; Pujari, Sidharam P; Cabrera, Wilfredo; Dick, Don; Veyan, Jean-François; Hourani, Rami; Halls, Mathew D; Zuilhof, Han; Chabal, Yves J

    2016-03-09

    The ability to selectively chemically functionalize silicon nitride (Si3N4) or silicon dioxide (SiO2) surfaces after cleaning would open interesting technological applications. In order to achieve this goal, the chemical composition of surfaces needs to be carefully characterized so that target chemical reactions can proceed on only one surface at a time. While wet-chemically cleaned silicon dioxide surfaces have been shown to be terminated with surficial Si-OH sites, chemical composition of the HF-etched silicon nitride surfaces is more controversial. In this work, we removed the native oxide under various aqueous HF-etching conditions and studied the chemical nature of the resulting Si3N4 surfaces using infrared absorption spectroscopy (IRAS), x-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), and contact angle measurements. We find that HF-etched silicon nitride surfaces are terminated by surficial Si-F and Si-OH bonds, with slightly subsurface Si-OH, Si-O-Si, and Si-NH2 groups. The concentration of surficial Si-F sites is not dependent on HF concentration, but the distribution of oxygen and Si-NH2 displays a weak dependence. The Si-OH groups of the etched nitride surface are shown to react in a similar manner to the Si-OH sites on SiO2, and therefore no selectivity was found. Chemical selectivity was, however, demonstrated by first reacting the -NH2 groups on the etched nitride surface with aldehyde molecules, which do not react with the Si-OH sites on a SiO2 surface, and then using trichloro-organosilanes for selective reaction only on the SiO2 surface (no reactivity on the aldehyde-terminated Si3N4 surface).

  15. Chemical modification of contractile 3-nm-diameter filaments in Vorticella spasmoneme by diethyl-pyrocarbonate and its reversible renaturation by hydroxylamine.

    Science.gov (United States)

    Fang, Jie; Zhang, Bei; Asai, Hiroshi

    2003-10-31

    A peritrich ciliate possesses a zooid and a long stalk consisting of a bundle of 3-nm-diameter filaments. Glycerinated stalks can contract in the presence of free Ca(2+) and re-extend in the absence of free Ca(2+). In the present study, we demonstrated that histidine residue(s) played a critical role in spasmoneme contraction by using glycerinated stalk of Vorticella. Concentration-dependent inhibition of spasmoneme contraction was observed in the presence of reversible histidine-modifying reagent named diethyl-pyrocarbonate (DEPC). In addition, the contractility degree of DEPC-modified spasmoneme could be partially restored by hydroxylamine treatment. The 244nm absorption of modified spasmoneme protein(s) increased with rising DEPC concentration and decreased following the addition of hydroxylamine treatment. Adding Ca(2+) before DEPC modification could prevent the spasmoneme contraction from inhibition of DEPC. Those results suggested that histidine residues were actively involved in spasmoneme contraction. Ca(2+)-binding ability of spasmin was not inhibited by DEPC modification, which suggested that the essential histidine residues were not on the calcium-binding site of spasmin.

  16. Constituintes químicos e estudos toxicológicos do óleo essencial extraído das folhas de Citrus limon Burn (Rutaceae

    Directory of Open Access Journals (Sweden)

    L.M.L. Campelo

    2013-01-01

    Full Text Available A caracterização química do óleo essencial de folhas de Citrus limon (Rutaceae resultou na identificação de mistura de monoterpenos (limoneno, linalol, cis-óxido de limoneno, trans-óxido de limoneno, citronelal, neral, geranial, nerol e acetato de geranil. As estruturas dos compostos do óleo essencial foram identificadas por GC/MS, por comparação com dados da literatura. Os efeitos da administração crônica oral do óleo essencial de folhas de Citrus limon foram investigados sobre parâmetros bioquímicos e hematológicos em camundongos Swiss machos. Os animais (n = 10/grupo foram tratados por via oral diariamente durante 30 dias com óleo essencial de folhas de Citrus limon, nas doses de 50, 100 ou 150 mg kg-1 de massa corporal e os parâmetros bioquímicos e hematológicos avaliados. O tratamento não causou nenhuma morte ou toxicidade nos animais. A administração do óleo essencial não alterou os parâmetros bioquímicos e hematológicos e a massa dos órgãos, exceto por diminuição de 21 e 11% em uréia e ácido úrico, respectivamente, e 9%, nos níveis plasmáticos de aspartato transaminase (AST. Para os parâmetros hematológicos, houve pequenas mudanças nas contagens de neutrófilos, linfócitos, eosinófilos e monócitos, mas estes não foram diferentes dos valores de referência. Além disso, houve diminuição significativa nos triglicerídeos detectado nos animais tratados com dose de 150 mg kg-1 de óleo essencial. Em conclusão, a administração crônica de óleo essencial não induziu nenhum efeito de risco na maioria dos parâmetros bioquímicos e hematológicos estudados em camundongos Swiss machos. No entanto, a diminuição dos níveis de uréia e ácido úrico em doses elevadas, sugere um possível efeito de insuficiência renal e aumento no teor de AST, sugerindo possível sobrecarga hepática que deve ser investigada com mais detalhe.

  17. Chemical modification of a bitumen and its non-fuel uses. [Reactions of tar sand asphaltenes in synthesis of non-fuel products

    Energy Technology Data Exchange (ETDEWEB)

    Moschopedis, S.E.; Speight, J.G.

    1974-01-01

    Simple reactions are described whereby tar sand bitumen can be converted to a whole range of materials. Examples are given to illustrate the non-fuel uses of the products. The following reactions of Athabasca asphaltenes are considered: oxidation, halogenation, sulfonation and sulfomethylation, phosphorylation, hydrogenation, reactions with S and O, reactions with metal salts, and miscellaneous chemical conversions. (JGB)

  18. Studies on phospholipase a and its zymogen from porcine pancreas IV. The influence of chemical modification of the lecithin structure on substrate properties

    NARCIS (Netherlands)

    Bonsen, P.P.M.; Haas, Gerard H. de; Pieterson, W.A.; Deenen, L.L.M. van

    1972-01-01

    1. 1. A series of chemically modified lecithins were used to investigate by kinetic analyses their substrate c.q. inhibitor properties for porcine pancreatic phospholipase A. The substrate analogues used were systematically modified in: the stereochemical configuration, the susceptible ester bond,

  19. Studies on phospholipase a and its zymogen from porcine pancreas IV. The influence of chemical modification of the lecithin structure on substrate properties

    NARCIS (Netherlands)

    Bonsen, P.P.M.; Haas, Gerard H. de; Pieterson, W.A.; Deenen, L.L.M. van

    1972-01-01

    1. 1. A series of chemically modified lecithins were used to investigate by kinetic analyses their substrate c.q. inhibitor properties for porcine pancreatic phospholipase A. The substrate analogues used were systematically modified in: the stereochemical configuration, the susceptible ester bond, t

  20. Effect of thermal and chemical modifications on the mechanical and release properties of paracetamol tablet formulations containing corn, cassava and sweet potato starches as filler-binders

    Institute of Scientific and Technical Information of China (English)

    Mariam; Vbamiunomhene; Lawal; Michael; Ayodele; Odeniyi; Oludele; Adelanwa; Itiola

    2015-01-01

    Objective: To investigate the effects of acetylation and pregelatinization of cassava and sweet potato starches on the mechanical and release properties of directly compressed paracetamol tablet formulations in comparison with official corn starch.Methods: The native starches were modified by acetylation and pregelatinization. The tablets were assessed using friability(Fr), crushing strength(Cs), disintegration time(Dt) and dissolution parameters. Results: Starch acetylation produced paracetamol tablets that were stronger and had the best balance of mechanical and disintegration properties, while pregelatinization produced tablets that were more friable but had a better overall strength in relation to disintegration than formulations made from natural starches. Correlations mainly existed between Dt and the dissolution parameters t80, t2 and k1 in the formulations. Conclusions: Modification of the experimental starches improved the mechanical and release properties of directly compressed paracetamol tablet formulations. Thus, they can be developed for use as pharmaceutical excipients in specific formulations.

  1. XPS and electrochemical evaluation of two-dimensional organic films obtained by chemical modification of self-assembled monolayers of (3-mercaptopropyl)trimethoxysilane on copper surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sinapi, Fabrice; Delhalle, Joseph; Mekhalif, Zineb

    2002-12-01

    In this study, a protective film consisting of an ultrathin two-dimensional polymer was prepared by hydrolysis of a (3-mercaptopropyl)trimethoxysilane (ethanol, 10{sup -3} M) self-assembled monolayer grafted onto copper and a subsequent modification with 3(heptofluoroisopropoxy)propyltrichlorosilane (toluene, 10{sup -3} M). Each stage of the preparation was characterized by X-ray photoelectron spectroscopy (XPS) while copper's corrosion-inhibitive properties were assessed by cyclic voltammetry measurements carried on in a 0.1 M NaOH medium. A remarkable enhancement of the copper's corrosion protection was obtained by the formation of lateral siloxane linkages between MPTS molecules absorbed followed by the grafting of the second molecular layer.

  2. Pectin modifications: a review.

    Science.gov (United States)

    Chen, Jun; Liu, Wei; Liu, Cheng-Mei; Li, Ti; Liang, Rui-Hong; Luo, Shun-Jing

    2015-01-01

    In recent years, the interest in studying modification of pectin has increased. A number of hydroxyl and carboxyl groups distributed along the backbone as well as a certain amount of neutral sugars presented as side chains make pectin capable of preparing a broad spectrum of derivatives. By forming pectin derivatives, their properties may be modified and some other new functional properties may be created. This article attempts to review the information about various methods used for pectin modification, including substitution (alkylation, amidation, quaternization, thiolation, sulfation, oxidation, etc.), chain elongation (cross-linking and grafting) and depolymerization (chemical, physical, and enzymatic degradation). Characteristics and applications of some pectin derivatives are also presented. In addition, the safety and regulatory status of pectin and its derivatives were reviewed.

  3. Surface modification of cellulose nanocrystals

    Science.gov (United States)

    Eyley, Samuel; Thielemans, Wim

    2014-06-01

    Chemical modification of cellulose nanocrystals is an increasingly popular topic in the literature. This review analyses the type of cellulose nanocrystal modification reactions that have been published in the literature thus far and looks at the steps that have been taken towards analysing the products of the nanocrystal modifications. The main categories of reactions carried out on cellulose nanocrystals are oxidations, esterifications, amidations, carbamations and etherifications. More recently nucleophilic substitutions have been used to introduce more complex functionality to cellulose nanocrystals. Multi-step modifications are also considered. This review emphasizes quantification of modification at the nanocrystal surface in terms of degree of substitution and the validity of conclusions drawn from different analysis techniques in this area. The mechanisms of the modification reactions are presented and considered with respect to the effect on the outcome of the reactions. While great strides have been made in the quality of analytical data published in the field of cellulose nanocrystal modification, there is still vast scope for improvement, both in data quality and the quality of analysis of data. Given the difficulty of surface analysis, cross-checking of results from different analysis techniques is fundamental for the development of reliable cellulose nanocrystal modification techniques.

  4. Efeito dos fungicidas Fosetil-Al e Metalaxil na colonização de mudas de Citrus sinensis (L. Osbeck enxertadas em C. limon (L. Burmf Effect of the fungicides Fosetyl-Al and Metalaxyl on arbuscular mycorrhizal colonization of seedlings of Citrus sinensis (L. Osbeck grafted onto C. limon (L. Burmf

    Directory of Open Access Journals (Sweden)

    Luiz Antônio Graciolli

    2000-05-01

    Full Text Available O efeito dos fungicidas Fosetil-Al e Metalaxil, recomendados para prevenção e controle da gomose, sobre o desenvolvimento de fungos micorrízicos arbusculares (FMA em Citrus sinensis Osbeck enxertado em C. limon Burmf foi investigado. Três experimentos foram realizados em 1990 e 1992, em Casa Branca e Ilha Solteira, estado de São Paulo, Brasil, respectivamente. Coletas de raízes foram feitas após a aplicação dos fungicidas, em intervalos mensais e semanais em Casa Branca, e a cada três dias em Ilha Solteira, para avaliar-se a percentagem de colonização radical por FMA. De modo geral, Fosetil-Al não apresentou efeito deletério no desenvolvimento dos micobiontes. Ao contrário, Metalaxil reduziu a colonização radical; e quando ambos os fungicidas foram aplicados juntos, a colonização radical foi diminuída, particularmente nos experimentos mais curtosWe investigated the effect of the fungicides Fosetyl-Al and Metalaxyl, recommended for prevention and control of gummosis, on the development of arbuscular mycorrhizal fungi (AMF in Citrus sinensis Osbeck grafted onto C. limon (L.Burmf. Three experiments were performed in 1990 and 1992, in Casa Branca and Ilha Solteira, State of São Paulo, Brazil, respectively. Root samples were collected after fungicide application at long (monthly and short (weekly periods at Casa Branca and every three days at Ilha Solteira, in order to evaluate the percentage of root colonization by AMF. Fosetyl-Al generally did not show a deleterious effect on the development of mycobionts. In contrast, Metalaxyl reduced root colonization by AMF, and when both fungicides were applied together, mycorrhizal colonization was decreased, particularly in the shorter time experiments

  5. Donor–Acceptor Copolymers of Relevance for Organic Photovoltaics: A Theoretical Investigation of the Impact of Chemical Structure Modifications on the Electronic and Optical Properties

    KAUST Repository

    Pandey, Laxman

    2012-08-28

    We systematically investigate at the density functional theory level how changes to the chemical structure of donor-acceptor copolymers used in a number of organic electronics applications influences the intrinsic geometric, electronic, and optical properties. We consider the combination of two distinct donors, where a central five-membered ring is fused on both sides by either a thiophene or a benzene ring, with 12 different acceptors linked to the donor either directly or through thienyl linkages. The interplay between the electron richness/deficiency of the subunits as well as the evolution of the frontier electronic levels of the isolated donors/acceptors plays a significant role in determining the electronic and optical properties of the copolymers. © 2012 American Chemical Society.

  6. Citrus limon-derived nanovesicles inhibit cancer cell proliferation and suppress CML xenograft growth by inducing TRAIL-mediated cell death.

    Science.gov (United States)

    Raimondo, Stefania; Naselli, Flores; Fontana, Simona; Monteleone, Francesca; Lo Dico, Alessia; Saieva, Laura; Zito, Giovanni; Flugy, Anna; Manno, Mauro; Di Bella, Maria Antonietta; De Leo, Giacomo; Alessandro, Riccardo

    2015-08-14

    Nanosized vesicles are considered key players in cell to cell communication, thus influencing physiological and pathological processes, including cancer. Nanovesicles have also been found in edible-plants and have shown therapeutic activity in inflammatory bowel diseases; however information on their role in affecting cancer progression is missing.Our study identify for the first time a fraction of vesicles from lemon juice (Citrus limon L.), obtained as a result of different ultracentrifugation, with density ranging from 1,15 to 1,19 g/ml and specific proteomic profile. By using an in vitro approach, we show that isolated nanovesicles inhibit cancer cell proliferation in different tumor cell lines, by activating a TRAIL-mediated apoptotic cell death. Furthermore, we demonstrate that lemon nanovesicles suppress CML tumor growth in vivo by specifically reaching tumor site and by activating TRAIL-mediated apoptotic cell processes. Overall, this study suggests the possible use of plant-edible nanovesicles as a feasible approach in cancer treatment.

  7. Confined direct analysis in real time ion source and its applications in analysis of volatile organic compounds of Citrus limon (lemon) and Allium cepa (onion).

    Science.gov (United States)

    Li, Yue

    2012-05-30

    The DART (direct analysis in real time) ion source is a novel atmospheric pressure ionization technique that enables efficient ionization of gases, liquids and solids with high throughput. A major limit to its wider application in the analysis of gases is its poor detection sensitivity caused by open-air sampling. In this study, a confined interface between the DART ion source outlet and mass spectrometer sampling orifice was developed, where the plasma generated by the atmospheric pressure glow discharge collides and ionizes gas-phase molecules in a Tee-shaped flow tube instead of in open air. It leads to significant increase of collision reaction probability between high energy metastable molecules and analytes. The experimental results show that the ionization efficiency was increased at least by two orders of magnitude. This technique was then applied in the real time analysis of volatile organic compounds (VOCs) of Citrus Limon (lemon) and wounded Allium Cepa (onion). The confined DART ion source was proved to be a powerful tool for the studies of plant metabolomics.

  8. Influence of the chemical modification and content of the clay on the mechanical properties of polypropylene and national bentonite composites; Influencia da modificacao quimica e do teor de argila nas propriedades mecanicas de compositos de polipropileno e bentonita nacional

    Energy Technology Data Exchange (ETDEWEB)

    Libano, Elaine V.D.G., E-mail: elainelibano@uezo.rj.gov.br [Centro Universitario Estadual da Zona Oeste - UEZO - RJ (Brazil); Pacheco, Elen B.A.V.; Visconte, Leila L.Y. [Universidade Federal do Rio de Janeiro - UFRJ, Instituto de Macromoleculas Professora Eloisa Mano - IMA, RJ (Brazil)

    2011-07-01

    The polypropylene/national clay composite was prepared by melt intercalation in a counter-rotating twin screw extruder, using bentonite as filler either in the natural (BENT) form or modified with the ammonium salt, cetyltrimethylammonium chloride (BENT-org). The clay was used in 1, 3 and 5%w. The influence of the modification and content of clay on the mechanical properties of this system was analysed. The analyses of infrared spectroscopy (FTIR) and X-ray diffraction (XRD) showed that clay organophilization did occur. The tensile modulus and the tensile strength at the yield point were not affected by chemical modification (BENT and BENT-org) or clay content. On the other hand, it was evidenced that the elongation at the yield point decreased with the addition of BENT and BENT-org to polypropylene. According to the thermogravimetric results, it was evidenced that the incorporation of clay into polypropylene improved thermal stability of the polymer in the composites with 5%w of BENT and 3 and 5%w of BENT-org. (author)

  9. Research Progress of Surface chemical Modification of Magnesium Hydroxide Flame Retardant%氢氧化镁阻燃剂表面改性技术研究进展

    Institute of Scientific and Technical Information of China (English)

    赵丽; 盖广清; 王立艳; 毕菲; 肖珊珊

    2015-01-01

    氢氧化镁具有阻燃、抑烟、填充的三大功能,是一种新型的绿色环保无机阻燃剂,具有广泛的用途。介绍了氢氧化镁阻燃剂的特点、阻燃机理,重点阐述了氢氧化镁表面改性技术的现状,展望了氢氧化镁阻燃剂表面改性的研究方向。%As new green and environment-friendly inorganic flame retardant, magnesium hydroxide has three functions including inflaming retarding, smoke abatement and filling, so it has been widely applied. In this paper, property characteristics and flame retardant mechanism of magnesium hydroxide flame retardant were introduced.The surface chemical modification methods of magnesium hydroxide were mainly expounded. And the development direction of the surface modification of magnesium hydroxide flame retardant was prospected.

  10. Studies on chemical structure modification and biology of a natural product, gambogic acid (I): Synthesis and biological evaluation of oxidized analogues of gambogic acid.

    Science.gov (United States)

    Wang, Jinxin; Zhao, Li; Hu, Yang; Guo, Qinglong; Zhang, Lei; Wang, Xiaojian; Li, Nianguang; You, Qidong

    2009-06-01

    Gambogic acid (GA), a natural product, exhibits high potency in inhibiting cancer cell growth through the effective induction of apoptosis. In order to investigate the structure-activity relationships of GA derivatives, 11 oxidized derivatives of GA were synthesized. Some of them showed strong inhibitory effects on HT-29, Bel-7402, BGC-823, A549, and SKOV 3 cell lines. Moreover, in this paper the cellular growth inhibitor 39-hydroxy-6-methoxy-gambogic acid methyl ester (10) was identified as a HepG2 cell apoptosis inhibitor through Annexin-V/PI double staining assay and the expression of the related apoptotic proteins (Bax and Bcl-2). Compound 10 may serve as a potential lead compound for the development of new anticancer drugs. Further SAR studies of GA derivatives indicated that modification of carbon-carbon double bond at C-32/33 or C-37/38 and of the methyl groups at C-39/C-35 can improve antitumor activity.

  11. Coupling of importin beta binding peptide on plasmid DNA: transfection efficiency is increased by modification of lipoplex's physico-chemical properties

    Directory of Open Access Journals (Sweden)

    Escriou Virginie

    2003-09-01

    Full Text Available Abstract Background Non-viral vectors for gene transfer are less immunogenic than viral vectors but also less efficient. Significant effort has focused on enhancing non-viral gene transfer efficiency by increasing nuclear import of plasmid DNA, particularly by coupling nuclear localization peptidic sequences to plasmid DNA. Results We have coupled a 62-aminoacid peptide derived from hSRP1α importin beta binding domain, called the IBB peptide to plasmid DNA by using the heterobifunctional linker N-(4-azido-2,3,5,6 tetrafluorobenzyl-6-maleimidyl hexanamide (TFPAM-6. When covalently coupled to plasmid DNA, IBB peptide did not increase the efficiency of cationic lipid mediated transfection. The IBB peptide was still able to interact with its nuclear import receptor, importin β, but non-specifically. However, we observed a 20-fold increase in reporter gene expression with plasmid DNA / IBB peptide complexes under conditions of inefficient transfection. In which case, IBB was associated with plasmid DNA through self assembling ionic interaction. Conclusions The improvement of transfection activity was not due to an improved nuclear import of DNA, but rather by the modification of physicochemical properties of IBB peptide / plasmid complexes. IBB peptide increased lipoplex size and these larger complexes were more efficient for gene transfer.

  12. Chemical modification of organoclay cloisite ®30B with silane 3-aminopropyltriethoxysilane; Modificacao quimica da argila organofilica cloisite ®30B com o silano 3-aminopropiltrietoxisilano

    Energy Technology Data Exchange (ETDEWEB)

    Bertuoli, P.T.; Frizzo, V.P.; Zattera, A.J., E-mail: paulabertuoli@hotmail.com [Universidade de Caxias do Sul (UCS), RS (Brazil). Programa de Pos-Graduacao em Engenharia de Processos e Tecnologias; Scienza, L.C. [Universidade Federal do Rio Grande do Sul (UFRGS), RS (Brazil). Departamento de Materiais

    2014-07-01

    The montmorillonite (MMT) is the inorganic phase more used in obtaining polymer nanocomposites. To improve the compatibility and dispersion of MMT in the polymer resin, many researchers have performed the process of functionalization of the clay with silane. This study was performed with the objective of modifying the Cloisite®30B clay with 3-aminopropyltriethoxysilane (APS). The modification was carried out by ion-exchange method using 10 g of clay Cloisite®30B (MMT-30B), 500 mL of hydroalcoholic solution (75/25 v/v) and 10 g of silane. The clay modified with silane (S-MMT{sub 30B}) was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR). Through the XRD was observed an increase in the basal spacing d{sub 001} of 1.82 to 2.2 nm. With the analysis of TGA was observed that S-MMT{sub 30B} showed greater weight loss than MMT-30B due to decomposition of the silane. The presence of band at 1562 cm-1 in the FTIR spectrum of S-MMT{sub 30B} confirmed the presence of silane in the structure of the modified clay. (author)

  13. Systematic evaluation and optimization of modification reactions of oligonucleotides with amines and carboxylic acids for the synthesis of DNA-encoded chemical libraries.

    Science.gov (United States)

    Franzini, Raphael M; Samain, Florent; Abd Elrahman, Maaly; Mikutis, Gediminas; Nauer, Angela; Zimmermann, Mauro; Scheuermann, Jörg; Hall, Jonathan; Neri, Dario

    2014-08-20

    DNA-encoded chemical libraries are collections of small molecules, attached to DNA fragments serving as identification barcodes, which can be screened against multiple protein targets, thus facilitating the drug discovery process. The preparation of large DNA-encoded chemical libraries crucially depends on the availability of robust synthetic methods, which enable the efficient conjugation to oligonucleotides of structurally diverse building blocks, sharing a common reactive group. Reactions of DNA derivatives with amines and/or carboxylic acids are particularly attractive for the synthesis of encoded libraries, in view of the very large number of building blocks that are commercially available. However, systematic studies on these reactions in the presence of DNA have not been reported so far. We first investigated conditions for the coupling of primary amines to oligonucleotides, using either a nucleophilic attack on chloroacetamide derivatives or a reductive amination on aldehyde-modified DNA. While both methods could be used for the production of secondary amines, the reductive amination approach was generally associated with higher yields and better purity. In a second endeavor, we optimized conditions for the coupling of a diverse set of 501 carboxylic acids to DNA derivatives, carrying primary and secondary amine functions. The coupling efficiency was generally higher for primary amines, compared to secondary amine substituents, but varied considerably depending on the structure of the acids and on the synthetic methods used. Optimal reaction conditions could be found for certain sets of compounds (with conversions >80%), but multiple reaction schemes are needed when assembling large libraries with highly diverse building blocks. The reactions and experimental conditions presented in this article should facilitate the synthesis of future DNA-encoded chemical libraries, while outlining the synthetic challenges that remain to be overcome.

  14. Control of oil-wetting on technical textiles by means of photo-chemical surface modification and its relevance to the performance of compressed air filters

    Energy Technology Data Exchange (ETDEWEB)

    Bahners, Thomas, E-mail: bahners@dtnw.de [Deutsches Textilforschungszentrum Nord-West gGmbH (DTNW), Adlerstr. 1, 47798 Krefeld (Germany); Mölter-Siemens, Wolfgang; Haep, Stefan [Institut für Energie- und Umwelttechnik e.V. (IUTA), Bliersheimer Str. 60, 47229 Duisburg (Germany); Gutmann, Jochen S. [Deutsches Textilforschungszentrum Nord-West gGmbH (DTNW), Adlerstr. 1, 47798 Krefeld (Germany); Universität Duisburg-Essen, Physikalische Chemie and CENIDE, Universitätsstr. 2, 45141 Essen (Germany)

    2014-09-15

    Highlights: • The oil repellence of textile fabrics was increased following the Wenzel concept. • Fiber surfaces were micro-roughened by means of pulsed UV laser irradiation. • Subsequent UV-induced grafting yielded pronounced oil repellence. • The grafting process conserved the delicate topography of the fiber surfaces. • The modified fabrics showed favorable drainage behavior in oil droplet separation. - Abstract: A two-step process comprising a surface roughening step by excimer laser irradiation and a post-treatment by photo-grafting to decrease the surface free energy was employed to increase the oil repellence of technical fabrics made of poly(ethylene terephthalate) (PET). The modification was designed to improve the performance of multi-layer filters for compressed air filtration, in which the fabrics served to remove, i.e. drain, oil separated from the air stream. In detail, the fibers surfaces were roughened by applying several laser pulses at a wavelength of 248 nm and subsequently photo-grafted with 1H,1H,2H,2H-perfluoro-decyl acrylate (PPFDA). The oil wetting behavior was increased by the treatments from full wetting on the as-received fabrics to highly repellent with oil contact angles of (131 ± 7)°. On surfaces in the latter state, oil droplets did not spread or penetrate even after one day. The grafting of PPFDA alone without any surface roughening yielded an oil contact angle of (97 ± 11)°. However, the droplet completely penetrated the fabric over a period of one day. The drainage performance was characterized by recording the pressure drop over a two-layer model filter as a function of time. The results proved the potential of the treatment, which reduced the flow resistance after 1-h operation by approximately 25%.

  15. Mitochondrial protein acetylation as a cell-intrinsic, evolutionary driver of fat storage: chemical and metabolic logic of acetyl-lysine modifications.

    Science.gov (United States)

    Ghanta, Sirisha; Grossmann, Ruth E; Brenner, Charles

    2013-01-01

    Hormone systems evolved over 500 million years of animal natural history to motivate feeding behavior and convert excess calories to fat. These systems produced vertebrates, including humans, who are famine-resistant but sensitive to obesity in environments of persistent overnutrition. We looked for cell-intrinsic metabolic features, which might have been subject to an evolutionary drive favoring lipogenesis. Mitochondrial protein acetylation appears to be such a system. Because mitochondrial acetyl-coA is the central mediator of fuel oxidation and is saturable, this metabolite is postulated to be the fundamental indicator of energy excess, which imprints a memory of nutritional imbalances by covalent modification. Fungal and invertebrate mitochondria have highly acetylated mitochondrial proteomes without an apparent mitochondrially targeted protein lysine acetyltransferase. Thus, mitochondrial acetylation is hypothesized to have evolved as a nonenzymatic phenomenon. Because the pKa of a nonperturbed Lys is 10.4 and linkage of a carbonyl carbon to an ε amino group cannot be formed with a protonated Lys, we hypothesize that acetylation occurs on residues with depressed pKa values, accounting for the propensity of acetylation to hit active sites and suggesting that regulatory Lys residues may have been under selective pressure to avoid or attract acetylation throughout animal evolution. In addition, a shortage of mitochondrial oxaloacetate under ketotic conditions can explain why macronutrient insufficiency also produces mitochondrial hyperacetylation. Reduced mitochondrial activity during times of overnutrition and undernutrition would improve fitness by virtue of resource conservation. Micronutrient insufficiency is predicted to exacerbate mitochondrial hyperacetylation. Nicotinamide riboside and Sirt3 activity are predicted to relieve mitochondrial inhibition.

  16. Structure-Function, Stability, and Chemical Modification of the Cyanobacterial Cytochrome b[subscript 6]f Complex from Nostoc sp. PCC 7120

    Energy Technology Data Exchange (ETDEWEB)

    Baniulis, Danas; Yamashita, Eiki; Whitelegge, Julian P.; Zatsman, Anna I.; Hendrich, Michael P.; Hasan, S. Saif; Ryan, Christopher M.; Cramer, William A.; (Semel); (Purdue); (Osaka)

    2009-06-08

    The crystal structure of the cyanobacterial cytochrome b{sub 6}f complex has previously been solved to 3.0-{angstrom} resolution using the thermophilic Mastigocladus laminosus whose genome has not been sequenced. Several unicellular cyanobacteria, whose genomes have been sequenced and are tractable for mutagenesis, do not yield b{sub 6}f complex in an intact dimeric state with significant electron transport activity. The genome of Nostoc sp. PCC 7120 has been sequenced and is closer phylogenetically to M. laminosus than are unicellular cyanobacteria. The amino acid sequences of the large core subunits and four small peripheral subunits of Nostoc are 88 and 80% identical to those in the M. laminosus b{sub 6}f complex. Purified b{sub 6}f complex from Nostoc has a stable dimeric structure, eight subunits with masses similar to those of M. laminosus, and comparable electron transport activity. The crystal structure of the native b{sub 6}f complex, determined to a resolution of 3.0{angstrom} (PDB id: 2ZT9), is almost identical to that of M. laminosus. Two unique aspects of the Nostoc complex are: (i) a dominant conformation of heme b{sub p} that is rotated 180 deg. about the {alpha}- and {gamma}-meso carbon axis relative to the orientation in the M. laminosus complex and (ii) acetylation of the Rieske iron-sulfur protein (PetC) at the N terminus, a post-translational modification unprecedented in cyanobacterial membrane and electron transport proteins, and in polypeptides of cytochrome bc complexes from any source. The high spin electronic character of the unique heme cn is similar to that previously found in the b{sub 6}f complex from other sources.

  17. Rapid Selection of Phage Se-scFv with GPX Activity via Combination of Phage Display Antibody Library with Chemical Modification

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Glutathione peroxidase (GPX) plays an important role in scavenging reactive oxygen species. A series of catalytic antibodies with GPX activity have been generated by the authors of this study. To obtain humanized catalytic antibodies, the phage-displayed human antibody library was used to select novel antibodies by repetitive screening. Phage antibodies, scFv-B8 and scFv-H6 with the GSH-binding site, were obtained from the library by enzyme-linked immunosorbent assay(ELISA) analysis with 4 rounds of selection against their respective haptens, S-2,4-dinitriphenyl t-butyl ester(GSH-s-DNP-Bu) and S-2,4-dinitriphenyl t-hexyl ester(GSH-s-DNP-He). Nevertheless, several studies need to be conducted to determine whether scFv-B8 and scFv-H6 possess GPX activity. To enhance the speed of the selection, selenocysteine(Sec, the catalytic group of GPX) was incorporated directly into the phages, scFv-B8 and scFv-H6, by chemical mutation to form the phages Se-scFv-B8 and Se-scFv-H6. The GPX activities were found to be 3012 units/μmol and 2102 units/μmol, respectively. To improve the GPX activity of the phage Se-scFv-B8, DNA shuffling was used to construct a secondary library and another positive phage antibody scFv-B9 was screened out by another panning against GSH-s-DNP-Bu. When Sec was incorporated via chemical mutation into the phage antibody scFv-B9, its GPX activity reached 3560 units/μmol, which is 1.17-fold higher than the phage antibody Se-scFv-B8and almost approached the order of magnitude of native GPX. The rapid selection is the prerequisite for generating humanized Se-scFv with GPX activity.

  18. Covalent modification of a melanoma-derived antigenic peptide with a natural quinone methide. Preliminary chemical, molecular modelling and immunological evaluation studies.

    Science.gov (United States)

    Douat-Casassus, Céline; Marchand-Geneste, Nathalie; Diez, Elisabeth; Aznar, Céline; Picard, Philippe; Geoffre, Serge; Huet, Aline; Bourguet-Kondracki, Marie-Lise; Gervois, Nadine; Jotereau, Francine; Quideau, Stéphane

    2006-05-01

    A LigandFit shape-directed docking methodology was used to identify the best position at which the melanoma-derived MHC class-I HLA-A2-binding antigenic peptide ELAGIGILTV could be modified by attaching a small molecule capable of fitting at the interface of complementary determining regional (CDR) loops of a T-cell receptor (TCR) while triggering T-cell responses. The small molecule selected here for determining the feasibility of this alternative track to chemical alteration of antigenic peptides was the electrophilic quinone methide (+)-puupehenone (), a natural product that belongs to a family of marine metabolites capable of expressing immunomodulatory activities. A preliminary chemical reactivity model study revealed the efficacy of the thiol group of a cysteine (C) side-chain in its nucleophilic addition reaction with in a regio- and diastereoselective manner. The best TCR/HLA-A2 ligand [i.e., ELAGCGILTV-S-puupehenol ()] then identified by the LigandFit docking procedure was synthesized and used to pulse HLA-A2(+) T2 cells for T-cell stimulation. Among the ELAGIGILTV-specific T-cell clones we tested, five of them recognized the conjugate in spite of its low binding affinity for the HLA-A2 molecules. The resulting T-cell stimulation was determined through the intracytoplasmic secretion of IFN-gamma and the percentage of T-cells thus activated. These highly encouraging results indicate that small non-peptidic natural product-derived molecules attached onto the central part of an antigenic peptide can fit at the TCR/HLA-A2 interface with induction of T-cell responses.

  19. Modification of reservoir chemical and physical factors in steamfloods to increase heavy oil recovery. [Quarterly report], January 1--March 31, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Yortsos, Y.C. [University of Southern California, Los Angeles, CA (United States)

    1997-08-01

    Thermal methods, and particularly steam injection, are currently recognized as the most promising for the efficient recovery of heavy oil. Despite significant progress, however, important technical issues remain open. Specifically, still inadequate is our knowledge of the complex interaction between porous media and the various fluids of thermal recovery (steam, water, heavy oil, gases, and chemicals). While, the interplay of heat transfer and fluid flow with pore- and macro-scale heterogeneity is largely unexplored. The objectives of this contract are to continue previous work and to carry out new fundamental studies in the following areas of interest to thermal recovery: displacement and flow properties of fluids involving phase change (condensation-evaporation) in porous media; flow properties of mobility control fluids (such as foam); and the effect of reservoir heterogeneity on thermal recovery. The specific projects are motivated by and address the need to improve heavy oil recovery from typical reservoirs as well as less conventional fractured reservoirs producing from vertical or horizontal wells. During this quarter, work continued on the development of relative permeabilities during steam displacement. Most of the work concentrated on the representation of the three-phase flow in terms of a double-drainage process. Work continued on the optimization of recovery processes in heterogeneous reservoirs by using optimal control methods. The effort at present is concentrating in fine-tuning the optimization algorithm as well as in developing control methodologies with different constraints. In parallel, we continued experiments in a Hele-Shaw cell with two controlled injection wells and one production well. In the area of chemical additives work continued on the behavior of non-Newtonian fluid flow and on foam displacements in porous media.

  20. Synthesis and chemical modifications of in-situ grown anatase TiO2 microspheres with isotropically exposed {0 0 1} facets for superhydrophobic and self-cleaning properties

    Science.gov (United States)

    Hu, Wanbiao; Yu, Yuanlie; Chen, Hua; Lau, Kenny; Craig, Vincent; Brink, Frank; Withers, Ray L.; Liu, Yun

    2015-12-01

    Excellent and robust hydrophobic materials generally benefit from specifically exposed surfaces i.e. always the low-energy surfaces, and well-defined micro/nano-structures that are achieved through advanced facilities and complicated process with a high cost. We hereof demonstrate that the superhydrophobicity and further self-cleaning properties are also attainable based on high-energy crystalline facets by an appropriate chemical modification. Specifically, anatase TiO2 microspheres were large-scale synthesized to exhibit isotropically exposed high-energy {0 0 1} facets through optimizing the HF/H2O2/H2O ratio during hydrothermal processes. The formation of the microspheres was uncovered to be an in-situ ;growth-cum-assembly; grown mechanism. Such high-energy {0 0 1} facets facilitate the strong coupling between the resultant TiO2 microspheres and the modifier (2,2,3,3,4,4,5,5-octafluoro-1-pentanol) because the {0 0 1} facets offer abundant active sites for chemical bonding, showing great merits for superhydrophobicity (with water contact angle of 154 ± 2°, 6 μl droplets), and further stably surface self-cleaning i.e. easily removing surface contamination (e.g. Al2O3 powders). This integrated strategy represents a milestone in design and fabrication of delicate composites with high-energy surfaces for specific functions and properties.

  1. Modification of chemical and physical factors in steamflood to increase heavy oil recovery. Annual report, October 1, 1991--September 30, 1992

    Energy Technology Data Exchange (ETDEWEB)

    Yortsos, Y.C.

    1993-07-01

    This report covers work performed in the various physicochemical factors for the improvement of oil recovery efficiency. In this context, three general areas were studied: (i) The understanding of vapor-liquid flow in porous media, whether the flow is internal (boiling), external (steam injection) or countercurrent (as in vertical heat pipes); (ii) The effect of reservoir heterogeneity, particularly as it regards fractured systems; (iii) The flow properties of additives for the improvement of recovery efficiency, in particular the injection of caustic and foams. The studies completed under this contract involved ap three research tools, analysis, computation and experiments. We have focused on pore level modeling using pore networks and on flow visualization using Hele-Shaw cells. Experiments involving core samples were conducted for the chemical additives investigation. Finally, simulation at the pore scale, pore network scale and reservoir scale were also undertaken. Part of the work has been detailed in five DOE Technical Reports as shown at the end of this report.

  2. Thermal Modification of a-SiC:H Films Deposited by Plasma Enhanced Chemical Vapour Deposition from CH4+SiH4 Mixtures

    Institute of Scientific and Technical Information of China (English)

    刘玉学; 王宁会; 刘益春; 申德振; 范希武; 李灵燮

    2001-01-01

    The effects of thermal annealing on photoluminescence (PL) and structural properties of a-Si1-xCx :H films deposited by plasma enhanced chemical vapour deposition from CH4+SiH4 mixtures are studied by using infrared, PL and transmittance-reflectance spectra. In a-SiC:H network, high-temperature annealing gives rise to the effusion of hydrogen from strongly bonded hydrogen in SiH, SiH2, (SiH2)n, SiCHn and CHn configurations and the break of weak C-C, Si-Si and C-Si bonds. A structural rearrangement will occur, which causes a significant correlation of the position and intensity of the PL signal with the annealing temperature. The redshift of the PL peak is related to the destruction of the confining power of barriers. However, the PL intensity does not have a significant correlation with the annealing temperature for a C-rich a-SiC:H network, which refers to the formation of π-bond cluster as increasing carbon content. It is indicated that the thermal stability of C-rich a-Si1-xCx:H films is better than that of Si-like a-Si1-xCx :H films.

  3. Modification of chemical and physical factors in steamflood to increase heavy oil recovery. Annual report, October 1, 1992--September 30, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Yortsos, Y.C.

    1994-10-01

    Thermal methods, and particularly steam injection, are currently recognized as the most promising for the efficient recovery of heavy oil. Despite significant progress, however, important technical issues remain open. Specifically, still inadequate is our knowledge of the complex interaction between porous media and the various fluids of thermal recovery (steam, water, heavy oil, gases, and chemicals). While, the interplay of heat transfer and fluid flow with pore- and macro-scale heterogeneity is largely unexplored. Objectives of this work contract are to carry out new studies in the following areas: displacement and flow properties of fluids involving phase change in porous media; flow properties of mobility control fluids (such as foam); and the effect of reservoir heterogeneity on thermal recovery. Specific projects address the need to improve heavy oil recovery from typical reservoirs as well as less conventional fractured reservoirs producing from vertical or horizontal wells. In the area of vapor-liquid flow, we present the continuation of work on the pore network modeling of bubble growth in porous media driven by the application of a prescribed heat flux or superheat. The scaling of bubble growth in porous media is also discussed. In another study we study the problem of steam injection in fractured systems using visualization in micromodels. The interplay of drainage, imbibition and bubble growth problems is discussed.

  4. Chemical modification of wheat protein-based natural polymers: grafting and cross-linking reactions with poly(ethylene oxide) diglycidyl ether and ethyl diamine.

    Science.gov (United States)

    Kurniawan, Lusiana; Qiao, Greg G; Zhang, Xiaoqing

    2007-09-01

    Mobile poly(ethylene oxide) diglycidyl ether (PEODGE) segments were chemically grafted onto a soluble wheat protein (WP), and different network structures were formed via coupling reactions with ethyl diamine (EDA) in different PEODGE/EDA (PE) ratios. When the PE ratio was 1:1, linear PEs were the predominant segments grafted onto WP chains and the whole WP-PEODGE-EDA (WPE) system was still soluble with an increased molecular weight. Reducing the amount of EDA in the systems produced insoluble cross-linked WPE networks. The broad distribution of network structures and chain mobility resulted in a broad glass transition for the WPE materials. However, the glass transition started at lower temperatures, and the materials became flexible at room temperature. The PE segments were present in all rigid, intermediate, and mobile phases in WPE networks, while the proportion of mobile WP chains was increased as a result of the plasticization effect from the mobile PE segments. The mobility of the most mobile component lipid was also restricted to some extent when forming the cross-linked WPE networks. The study demonstrated that the formation of different network structures with PE segments could significantly improve the flexibility of WP materials, vary the solubility, and modify the mechanical performance of WP-based natural polymer materials.

  5. Modification of chemical and conformational properties of natural organic matter by click chemistry as revealed by ESI-Orbitrap mass spectrometry.

    Science.gov (United States)

    Nebbioso, Antonio; Piccolo, Alessandro

    2015-11-01

    A click reaction is reported here for the first time as a useful technique to control the conformational stability of natural organic matter (NOM) suprastructures. Click conjugates were successfully formed between a previously butynylated NOM hydrophobic fraction and a hydrophilic polyethylene glycol (PEG)-amino chain. The click products were shown by size exclusion chromatography (HPSEC) hyphenated with Orbitrap mass spectrometry (MS) in electrospray ionization (ESI) (+), while precursors were visible in ESI (-). Despite their increase in molecular weight, HPSEC elution of click conjugates occurred after that of precursors, thus showing their departure from the NOM supramolecular association. This indicates that the click-conjugated NOM molecules were varied in their hydrophilic and cationic character and lost the capacity to accommodate in the original hydrophobic suprastructures. The most abundant product had the C16H30O5N4 formula, a click conjugate of butanoic acid, while other products were short-chained (C4-C8) linear unsaturated and hydroxylated carboxylic acids. Tandem MS revealed formation of triazole rings in clicked conjugates and their two fragmentations at the ester and the C-N alkyl-aryl bonds. The behavior of NOM molecules modified by click chemistry confirms that hydrophobicity and ionic charge of humic molecules play a pivotal role in stabilizing intermolecular forces in NOM. Moreover, the versatility of the click reaction may become useful to decorate NOM molecules with a variety of substrates, in order to alter NOM conformational and chemical properties and diversify its applications in the environment.

  6. Aplicación de modelos matemáticos al proceso de secado asistido por infrarrojos de descartes de limón (citrus limon (l.) burm. f. cv. genova)

    OpenAIRE

    PUENTE-DÍAZ, LUIS; ECHEGARAY- PACHECO, ERIC; CASTRO- MONTERO, EDUARDO; Di Scala,Karina

    2013-01-01

    Los desechos agroindustriales son uno de los principales problemas ambientales a nivel mundial. Debido a las altas exigencias de calidad, la comercialización de limones de exportación genera grandes cantidades de desechos. Los descartes de limón contienen fi bra, pectina, potasio, calcio y vitamina C. Por lo tanto, es importante desarrollar alternativas de procesamiento de estos sub-productos para agregarles valor y aumentar su vida útil. El objetivo de la presente investigación fue la aplica...

  7. Aplicación de modelos matemáticos al proceso de secado asistido por infrarrojos de descartes de limón (Citrus limon (L.) Burm. F. Cv. Genova)

    OpenAIRE

    Luis Puente-Díaz; Eric Echegaray-Pacheco; Eduardo Castro- Montero; Karina Di Scala

    2013-01-01

    Los desechos agroindustriales son uno de los principales problemas ambientales a nivel mundial. Debido a las altas exigencias de calidad, la comercialización de limones de exportación genera grandes cantidades de desechos. Los descartes de limón contienen fibra, pectina, potasio, calcio y vitamina C. Por lo tanto, es importante desarrollar alternativas de procesamiento de estos sub-productos para agregarles valor y aumentar su vida útil. El objetivo de la presente investigación fue la aplicac...

  8. Chemical strategies for modifications of the solar cell process, from wafering to emitter diffusion; Chemische Ansaetze zur Neuordnung des Solarzellenprozesses ausgehend vom Wafering bis hin zur Emitterdiffusion

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Kuno

    2009-11-06

    The paper describes the classic standard industrial solar cell based on monocrystalline silicon and describes new methods of fabrication. The first is an alternative wafering concept using laser microjet cutting instead of multiwire cutting. This method originally uses pure, deionized water; it was modified so that the liquid jet will not only be a liquid light conductor but also a transport medium for etching fluids supporting thermal abrasion of silicon by the laser jet. Two etching fluids were tested experimentally; it was found that water-free fluids based on perfluorinated solvents with very slight additions of gaseous chlorine are superior to all other options. In the second section, the wet chemical process steps between wafering and emitter diffusion (i.e. the first high-temperature step) was to be modified. Alternatives to 2-propanol were to be found in the experimental part. Purification after texturing was to be rationalized in order to reduce the process cost, either by using less chemical substances or by achieving shorter process times. 1-pentanol and p-toluolsulfonic acid were identified as two potential alternatives to 2-propanol as texture additives. Finally, it could be shown that wire-cut substrates processed with the new texturing agents have higher mechanical stabilities than substrates used with the classic texturing agent 2-propanol. [German] Im ersten Kapitel wird die klassische Standard-Industrie-Solarzelle auf der Basis monokristallinen Siliziums vorgestellt. Der bisherige Herstellungsprozess der Standard-Industrie-Solarzelle, der in wesentlichen Teilen darauf abzielt, diese Verluste zu minimieren, dient als Referenz fuer die Entwicklung neuer Fertigungsverfahren, wie sie in dieser Arbeit vorgestellt werden. Den ersten thematischen Schwerpunkt bildet die Entwicklung eines alternativen Wafering-Konzeptes zum Multi-Drahtsaegen. Die Basis des neuen, hier vorgestellten Wafering-Prozesses bildet das Laser-Micro-Jet-Verfahren. Dieses System

  9. Improving the antiprotozoal effect of saponins in the rumen by combination with glycosidase inhibiting iminosugars or by modification of their chemical structure

    Science.gov (United States)

    de la Fuente, Gabriel; Nash, Robert J.; Braganca, Radek; Duval, Stephane; Bouillon, Marc E.; Lahmann, Martina; Newbold, C. Jamie

    2017-01-01

    The antiprotozoal effect of saponins is transitory, as when saponins are deglycosylated to sapogenins by rumen microorganisms they become inactive. We hypothesised that the combination of saponins with glycosidase-inhibiting iminosugars might potentially increase the effectiveness of saponins over time by preventing their deglycosylation in the rumen. Alternatively, modifying the structure of the saponins by substituting the sugar moiety with other small polar residues might maintain their activity as the sugar substitute would not be enzymatically cleaved. The aim of this in vitro study was to evaluate the acute antiprotozoal effect and the stability of this effect over a 24 h incubation period using ivy saponins, a stevia extract rich in iminosugars, ivy saponins with stevia extract, and a chemically modified ivy saponin, hederagenin bis-succinate (HBS). The effects on fermentation parameters and rumen bacterial communities were also studied. Ivy saponins with stevia and HBS had a greater antiprotozoal effect than ivy saponins, and this effect was maintained after 24 h of incubation (Pstevia extracts was more effective in shifting the fermentation pattern towards higher propionate (+39%) and lower butyrate (-32%) and lower ammonia concentration (-64%) than the extracts incubated separately. HBS caused a decrease in butyrate (-45%) and an increase in propionate (+43%) molar proportions. However, the decrease in ammonia concentration (-42%) observed in the presence of HBS was less than that caused by ivy saponins, either alone or with stevia. Whereas HBS and stevia impacted on bacterial population in terms of community structure, only HBS had an effect in terms of biodiversity (Pstevia and the modified saponin HBS had a strong antiprotozoal effect, although they differed in their effects on fermentation parameters and bacteria communities. Ivy saponins combined with an iminosugar-rich stevia extract and/or HBS should be evaluated to determine their antiprotozoal

  10. Modification of reservoir chemical and physical factors in steamfloods to increase heavy oil recovery. [Quarterly report], January 1--March 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Yortsos, Y.C.

    1996-07-01

    Thermal methods, and particularly steam injection, are currently recognized as the most promising for the efficient recovery of heavy oil. Despite significant progress, however, important technical issues remain open. Specifically, still inadequate is our knowledge of the complex interaction between porous media and the various fluids of thermal recovery (steam, water, heavy oil, gases, and chemicals). While, the interplay of heat transfer and fluid flow with pore- and macro-scale heterogeneity is largely unexplored. The objectives of this contract are to continue previous work and to carry out new fundamental studies in the following areas of interest to thermal recovery: displacement and flow properties of fluids involving phase change in porous media; flow properties of mobility control fluids (such as foam); and the effect of reservoir heterogeneity on thermal recovery. During this quarter, we focused on the development of relative permeabilities during steam displacement. Two particular directions were pursued: One involves the derivation of relative permeabilities based on a recently completed work on the pore-level mechanics of steam displacement. Progress has been made to relate the relative permeabilities to effects such as heat transfer and condensation, which are specific to steam injection problems. The second direction involves the development of three-phase relative permeabilities using invasion percolation concepts. We have developed models that predict the specific dependence of the permeabilities of three immiscible phases (e.g. awe, water and gas) on saturations and the saturation history. Both works are still in progress. In addition, work continues in the analysis of the stability of phase change fronts in porous media using a macroscopic approach.

  11. Study on the chemical constitents of Citrus limon leaves oil%柠檬叶挥发性成分分析

    Institute of Scientific and Technical Information of China (English)

    周丽珠; 梁忠云; 李月娟; 文彩琳

    2013-01-01

    用挥发油提取器提取柠檬叶中挥发油,利用气相色谱-质谱分析其中的化学成分,采用GC峰面积归一化法定量,鉴定出29种化合物,占挥发油总量的96.45%以上,主要成分为d-柠檬烯(28.69%) 、β-蒎烯(19.77%)、香茅醛(16.82%)、桧烯(5.10%)等.

  12. Developmental stimuli and stress factors affect expression of ClGLP1, an emerging allergen-related gene in Citrus limon.

    Science.gov (United States)

    Bruno, Leonardo; Spadafora, Natasha Damiana; Iaria, Domenico; Chiappetta, Adriana; Bitonti, Maria Beatrice

    2014-06-01

    Germins and germin-like proteins (GLPs) constitute an ubiquitous family of plant proteins that seem to be involved in many developmental and stress related processes. A novel GLP cDNA was isolated from Citrus limon and structural features and genomic organization were investigated by in silico and Southern blots analysis. In lemon, the ClGLP1 encodes a 24.38 kDa which possesses a conserved motif of plant GLPs proteins. A phylogetic analysis mapped ClGLP1 as belonging to the GER3 subfamily into the GLP1 group of large GLP family. ClGLP1 was differentially expressed in the various organs and was highest in mature fruit. Moreover, expression in the fruit was tissue- and stage-related as well as dependent on agricultural practice (organic vs conventional). ClGLP1 transcripts increased during the transition from the green (180 days after blooming) to the yellow (240 days after blooming) mature fruit and were strongly enhanced in yellow mature fruit from organic compared with conventional culture. A sudden and systemic increase in ClGLP1 expression level was observed in leaves injured by wounding, together with an increase of endogenous H2O2 amount. Notably, an enhancement of H202 was observed in fruit peel during transition from green to yellow fruit stage. All together our data showed that ClGLP1 expression can be modulated in relation to both developmental stimuli and culture practices; evidence is also provided that through an oxidase activity this gene could play a role in fruit maturation as well as in stress responses. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  13. Experiment of Aseptic Sowing Technique of Lemon[Citrus limon (L.) Burm.f.]%柠檬无菌播种试验

    Institute of Scientific and Technical Information of China (English)

    麦丽瑶; 岑惠锋; 吴道洲; 孙伟冰; 郭丽英; 吉前华

    2014-01-01

    [目的]研究柠檬[Citrus limon(L.) Burm.f.]种子萌发的适宜处理方法.[方法]以不同种皮剥离程度的柠檬种子(不剥种皮、只剥外种皮、剥除内外种皮)为试材,应用不同消毒剂[4%(V/V)蓝月亮、0.1%升汞]消毒不同时间(7、15、23 min),进行柠檬播种试验.[结果]0.1%升汞消毒8 min的效果优于4% (V/V)蓝月亮消毒15 min,但差异性不大;种子在剥除内、外种皮后萌发率、生长势情况都好于只剥外种皮和未剥除种皮的.[结论]考虑到升汞具有致癌变、致突变性等危害,在试验操作中不提倡使用,故以4% (V/V)蓝月亮处理15 min为柠檬种子消毒的最佳方式.该研究可为柠檬组织培养及柑橘无病毒苗木培育提供参考依据.

  14. Profundidade de amostragem do solo para avaliação do enxofre disponível em pomar de limão siciliano (Citrus limon Burm. Soil sampling depth for available sulphur evaluation in sicilian lemon (Citrus limon Burm. orchard

    Directory of Open Access Journals (Sweden)

    L.I. Prochnow

    1995-04-01

    Full Text Available Em um Latossolo Vermelho Escuro, textura média, no qual foram estabelecidos diferentes teores de enxofre, através da aplicação de doses crescentes de gesso agrícola (0, 1, 2 e 4 t/ha, estudou-se a profundidade adequada para coleta de amostras de terra para avaliação do S-SO4-2 "disponível" para o limão siciliano (Citrus limon Burm. enxertado sobre porta enxerto Volkameriano. As quantidades de sulfato no solo, extraídas pelo NH4OAc 0,5 M em HOAc 0,25 M, foram determinadas aos 6, 12 e 24 meses após a aplicação do produto nas seguintes profundidades: 0-5, 5-10, 10-20, 20-40, 40-80 e 80-120 cm. As quantidades de enxofre nas folhas do limão siciliano foram também determinadas na mesma época. Os dados obtidos e os estudos de correlação que se seguiram demonstraram evidências de que o limão siciliano teria, no período considerado, extraído enxofre, principalmente, da camada de O a 20 cm de profundidade, e assim sendo, fornece indícios de que esta deve ser a camada amostrada para fins da avaliação deste importante elemento nesta cultura.On a medium-textured Dark-Red Latosol (Typic Hapludox, in which increasing levels of sulfate were established by the application of different rates of phosphogypstim (0, 1, 2 e 4 t/ha, a study was carried out to obtain information about the depth of soil samples collected in order to evaluate the S-SO4-2 availability for the Sicilian lemon (Citrus limon Burm. grafted on "Volkameriano" rootstocks. Sulfate contents at different depths (0-5, 5-10, 10-20, 20-40, 40-80 and 80-120 cm were determined, by using the NH4OAc 0,5 M in HOAc 0,25 M extractor, 6,12 and 24 months after phosphogypsum application. Sulphur content in the leaves of the lemon plants were also determined at the same dates. Analytical data obtained and the correlation studies that followed, showed that the Sicilian lemon extracted sulphur mainly from the layer 0-20 cm and, therefore, this layer is considered representative for soil

  15. Preliminary study of microstructural properties and chemical modifications of interlayer shear weakness zone in Baihetan%白鹤滩层间错动带微结构特性及其化学改性初探

    Institute of Scientific and Technical Information of China (English)

    史存鹏; 冯夏庭; 江权; 徐鼎平

    2013-01-01

      白鹤滩水电站层间错动带结构疏松、性状软弱、空间展布范围大、力学强度低,严重影响着地下厂房洞室的稳定性。为了揭示并改良层间错动带的力学特性,首先通过矿物成分分析试验、扫描电镜试验和压汞试验,从微观结构角度对层间错动带的矿物组成特征、颗粒排列规律、孔隙分布规律进行了详细的研究,阐明了层间错动带的微观结构特性及其对灌浆材料选择的影响,进而开展了层间错动带化学溶液浸泡对比试验。试验表明,硅酸钠溶液可以有效改善层间错动带的完整性,明显提高层间错动带的弹性波速、抗压强度、弹性模量和凝聚力。其研究结果对白鹤滩层间错动带的工程加固和改性设计具有一定的借鉴意义。%Interlayer shear weakness zone has a series of features such as loose structure, easy to be softening, large spatial distribution and poor mechanical properties in Baihetan hydropower station. The existence of interlayer shear weakness zone seriously affects the stability of underground cavern groups of hydropower station. In order to reveal and improve the mechanical properties of interlayer shear weakness zone, X-ray diffractometer, scanning electron microscope and mercury intrusion porosimetry tests are applied separately to observe and determine the main mineral composition, the orientated range of particles and the distribution of pore structure in samples. Microstructural properties of interlayer shear weakness zone and its effect on the selection of grouting materials are discussed in detail combining with the testing data. What’s more, chemical modification experiments are carried out based on above experiments. Comparative experiment between samples immersed with or without sodium silicate solution indicates that chemical modification can improve the integrality, elastic wave velocity, compressive strength, elastic modulus and cohesion of

  16. 化学改性淀粉基木材胶黏剂的研究概况%Progress in Chemical Modification of Starch-based Wood Adhesives

    Institute of Scientific and Technical Information of China (English)

    王古月; 朱锦; 刘小青

    2011-01-01

    普通的淀粉胶黏剂耐水性和力学性能差,难以满足木材胶黏剂的使用要求,通过对其进行改性以提高其综合使用性能,从而开发廉价高性能淀粉基木材胶黏剂已成为人们研究的热点.笔者综述了国内外对淀粉的改性方法,重点介绍了化学改性的进展,并针对目前淀粉类胶黏剂普遍存在的问题指出了未来的发展方向.%Traditional starch-based adhesives can hardly meet the requirements for wood adhesion due to their poor water-resistance and low strength. How to improve their performance and then develop the affordable starch-based wood adhesive with outstanding properties has been a hot research topic. In this article, the modifications on starch, especially the chemical methods, were reviewed. At last, the future of starch-based wood adhesives was pointed out.

  17. Enzymatic Modification of Sphingomyelin

    DEFF Research Database (Denmark)

    Due to its major role in maintaining the water-retaining properties of the epidermis, ceramide is of great commercial potential in cosmetic and pharmaceuticals such as hair and skin care products. Currently, chemical synthesis of ceramide is a costly process, and developments of alternative cost......-efficient, high yield production methods are of great interest. In the present study, the potential of producing ceramide through the enzymatic hydrolysis of sphingomyelin have been studied. sphingomyelin is a ubiquitous membrane-lipid and rich in dairy products or by-products. It has been verified...... that sphingomyelin modification gives a feasible approach to the potential production of ceramide. The reaction system has been improved through system evaluation and the optimization of several important factors, and phospholipase C from Clostridium perfringens shows higher activity towards the hydrolysis reaction...

  18. Surface modification for corrosion resistance

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.

    1993-06-01

    The raw gas environments that arise from coal gasification have chemical compositions that are low in pO{sub 2} and moderate-to-high in pS{sub 2}. Metallic materials for service in such an environment undergo predominantly sulfidation attack at temperatures of 400 to 700{degree}C. Modification of alloy compositions in bulk can alter the scaling processes and lead to improvements in corrosion resistance, but the benefits can only be attained at temperatures much higher than the service temperatures of the components. Modification of surfaces of structural components by several of the coating techniques examined in this study showed substantial benefit in corrosion resistance when tested in simulated coal gasification environments. The paper presents several examples of surface modification and their corrosion performance.

  19. Readers of histone modifications

    Institute of Scientific and Technical Information of China (English)

    Miyong Yun; Jun Wu; Jerry L Workman; Bing Li

    2011-01-01

    Histone modifications not only play important roles in regulating chromatin structure and nuclear processes but also can be passed to daughter cells as epigenetic marks.Accumulating evidence suggests that the key function of histone modifications is to signal for recruitment or activity of downstream effectors. Here, we discuss the latest discovery of histone-modification readers and how the modification language is interpreted.

  20. Chemical modification of muscle protein in diabetes.

    Science.gov (United States)

    Alt, Nadja; Carson, James A; Alderson, Nathan L; Wang, Yuping; Nagai, Ryoji; Henle, Thomas; Thorpe, Suzanne R; Baynes, John W

    2004-05-15

    Levels of glycation (fructose-lysine, FL) and advanced glycoxidation and lipoxidation end-products (AGE/ALEs) were measured in total skeletal (gastrocnemius) muscle and myofibril protein and compared to levels of the same compounds in insoluble skin collagen of control and diabetic rats. Levels of FL in total muscle and myofibril protein were 3-5% the level of FL in skin collagen. The AGE/ALEs, N(epsilon)-(carboxymethyl)lysine (CML) and N(epsilon)-(carboxyethyl)lysine, were also significantly lower in total muscle and myofibril protein, approximately 25% of levels in skin collagen. The newly described sulfhydryl AGE/ALE, S-(carboxymethyl)cysteine (CMC), was also measured in muscle; levels of CMC were comparable to those of CML and increased similarly in response to diabetes. Although FL and AGE/ALEs increased in muscle protein in diabetes, the relative increase was less than that seen in skin collagen. These data indicate that muscle protein is partially protected against the increase in both glycation and AGE/ALE formation in diabetes.

  1. Chemical modification and characterization of quaternized polysulfones.

    CSIR Research Space (South Africa)

    Nonjola, P

    2008-12-01

    Full Text Available moisture than Nafion film (ca. 1mg respectively). Measurements were conducted by purging compressed air through the saturated solutions of MgCl (RH = 33%), Li(NO ) (RH = 47%), NH NO (RH = 61%), KBr (RH = 2 3 4 3 80%), BaCl (RH = 90%) and pure water... (RH = 100%). 2 Figure 1: FT-IR spectra of (3a), (3b) and (3c) respectively. Figure 2: TG curves of compounds (1b), (2b) and (3b). All samples were o heated at 10 C/min under N . 2 Figure 3: Water sorptions of the o thin films of 3b...

  2. Chemical modification of flax reinforced polypropylene composites

    CSIR Research Space (South Africa)

    Jacob John, Maya

    2009-04-01

    Full Text Available ) and ∆Ea is the activation energy for the relaxation. The slope of Arrhenius plot obtained by plotting log f versus 1/T will give the activation energy for that process. Table 3 presents the activation energy of the composites and it can be observed... at the temperature where the loss modulus is maximum indicating a relaxation phenomenon. The increase in loss modulus is attributed to the increase in energy absorption caused by the addition of fibres. 5.4.1.3 Mechanical damping factor (tan δ) Page 9 of 26...

  3. Chemical Modification of Cotton for Industrial Applications

    Science.gov (United States)

    Cotton (cellulose) is a known favorite in the textile industry and is the most used natural fiber-cloth to date. As we move to use more biodegradable, renewable and sustainable resources, cellulose, a natural polymer, is attracting attention and finding application in oil recovery, cosmetics, surfac...

  4. Micropropagation of seedless lemon (Citrus limon L. cv. Kaghzi Kalan) and assessment of genetic fidelity of micropropagated plants using RAPD markers.

    Science.gov (United States)

    Goswami, Komal; Sharma, R; Singh, P K; Singh, Govind

    2013-01-01

    A micropropagation protocol was developed for multiplication of seedless lemon (Citrus limon L. cv. Kaghzi Kalan) using nodal explants. The maximum shoot regeneration was observed on low level of BAP (0.1 mg l(-1)) or kinetin (0.5 mg l(-1)). BA was recorded to be better than kinetin in terms of number of days taken to bud break. The maximum number of shoots per explant was observed on 0.1 mg l(-1) BA and 0.5 mg l(-1) kinetin. Shoot proliferation decreased with increasing concentration of BA alone, but in case of a combination of BA and NAA (0.1 mg l(-1) each), it increased with increasing concentration of BA up to 10.0 mg l(-1). None of the treatments including BA or kinetin alone or BA in combination with NAA produced significantly more shoots for commercial exploitation. In the case of a combination of BA + kinetin + IBA, the maximum (5.5 shoots per explants) proliferation was observed on MS medium containing 1.0 mg l(-1) BA + 0.5 mg l(-1) kinetin + 0.5 mg l(-1) IBA or 0.25 mg l(-1) BA + 1.0 mg l(-1) kinetin + 1.0 mg l(-1) IBA. Regenerated shoots showed root induction on MS basal medium or on MS medium containing 1.0 mg l(-1) IBA. It is concluded that a five-fold increase (1.0 mg l(-1) BA + 0.5 mg l(-1) kinetin + 0.5 mg l(-1) IBA) in axillary shoot proliferation, while seven-fold increase (0.25 mg/l mg l(-1) BA + 1.0 mg l(-1) kinetin + 1.0 mg l(-1) IBA) during the second cycle of multiplication could be obtained using the two plant growth regulator combinations. PCR amplification with 14 different random primers confirmed no somaclonal variant up to two cycles of shoot multiplication.

  5. 二氧化硅粒子的表面化学修饰——方法、原理及应用%Chemical Modification of Silica: Method, Mechanism, and Application

    Institute of Scientific and Technical Information of China (English)

    陈凯玲; 赵蕴慧; 袁晓燕

    2013-01-01

    Silica is one of the most important inorganic materials, and has been drawing a growing number of attentions in the field of organic/inorganic composite materials. In this paper, research progress on methods and mechanisms of chemical modification as well as applications of modified silica particles are reviewed in detail. Mechanisms of coupling method, surface grafting methods ( "grafting from" and "grafting onto" included) and one-step method are discussed along with the comments on key points and advantages of these methods. The methods of "grafting from" based on conventional free radical polymerization, atom transfer radical polymerization and reversible addition-fragmentation chain transfer polymerization are discussed, whereas "grafting on" based on ring-opening addition reaction, "click chemistry" and esterification reaction are described. Generally, endowing silica surface with functional groups for further reaction by silane coupling agents is essential, and silane coupling agents and their modification mechanisms are introduced firstly. In addition, one-step method is also discussed here. At the same time, significances of surface modification which are improvement on dispeisibility, endowing silica with functionality and improvement on compatibility are summarized. The dispersibility of surface modified silica particles in organic solvents or organic matrix is improved. The modified silica particles are functioned by the groups or polymers which are grafted on their surfaces. The adhesive forces between organic phase and inorganic phase are enhanced since the modified silica particles are dispersed well in the organic matrix. And the modified silica particles are expected applications in fabricating new materials.%本文综述了近年来国内外对二氧化硅粒子表面化学修饰的研究成果,主要介绍了偶联剂法、表面接枝法和一步法的反应原理,探讨了各种改性方法的关键问题和优势,

  6. Synthesis and magnetic properties of a new family of macrocyclic M(II)3Ln(III) complexes: insights into the effect of subtle chemical modification on single-molecule magnet behavior.

    Science.gov (United States)

    Feltham, Humphrey L C; Clérac, Rodolphe; Ungur, Liviu; Vieru, Veacheslav; Chibotaru, Liviu F; Powell, Annie K; Brooker, Sally

    2012-10-15

    Thirteen tetranuclear mixed-metal complexes of the hexaimine macrocycle (L(Pr))(6-) have been prepared in a one-pot 3:1:3:3 reaction of copper(II) acetate hydrate, the appropriate lanthanide(III) nitrate hydrate, 1,4-diformyl-2,3-dihydroxybenzene (1), and 1,3-diaminopropane. The resulting family of copper(II)-lanthanide(III) macrocyclic complexes has the general formula Cu(II)(3)Ln(III)(L(Pr))(NO(3))(3)·solvents (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Tb, Ho, Er, Tm, or Yb). X-ray crystal structure determinations carried out on [Cu(3)Ce(L(Pr))(NO(3))(3)(MeOH)(3)] and [Cu(3)Dy(L(Pr))(NO(3))(3)(MeOH)(3)] confirmed that the large Ln(III) ion is bound in the central O(6) site and the three square pyramidal Cu(II) ions in the outer N(2)O(2) sites (apical donor either nitrate anion or methanol molecule) of the Schiff base macrocycle. Only the structurally characterized Cu(3)Tb complex, reported earlier, is a single-molecule magnet (SMM): the other 12 complexes do not exhibit an out-of-phase ac susceptibility signal or hysteresis of magnetization in a dc field. Ab initio calculations allowed us to rationalize the observed magnetic properties, including the significant impact of subtle chemical modification on SMM behavior. Broken-symmetry density functional theory (BS-DFT) calculations show there is a subtle structural balance as to whether the Cu···Cu exchange coupling is ferro- or antiferromagnetic. Of the family of 13 magnetically characterized tetranuclear Cu(II)(3)Ln(III) macrocyclic complexes prepared, only the Tb(III) complex is an SMM: the theoretical reasons for this are discussed.

  7. Electrostatic interactions play an essential role in the binding of oleic acid with α-lactalbumin in the HAMLET-like complex: a study using charge-specific chemical modifications.

    Science.gov (United States)

    Xie, Yongjing; Min, Soyoung; Harte, Níal P; Kirk, Hannah; O'Brien, John E; Voorheis, H Paul; Svanborg, Catharina; Hun Mok, K

    2013-01-01

    Human α-lactalbumin made lethal to tumor cells (HAMLET) and its analogs are partially unfolded protein-oleic acid (OA) complexes that exhibit selective tumoricidal activity normally absent in the native protein itself. To understand the nature of the interaction between protein and OA moieties, charge-specific chemical modifications of lysine side chains involving citraconylation, acetylation, and guanidination were employed and the biophysical and biological properties were probed. Upon converting the original positively-charged lysine residues to negatively-charged citraconyl or neutral acetyl groups, the binding of OA to protein was eliminated, as were any cytotoxic activities towards osteosarcoma cells. Retention of the positive charges by converting lysine residues to homoarginine groups (guanidination); however, yielded unchanged binding of OA to protein and identical tumoricidal activity to that displayed by the wild-type α-lactalbumin-oleic acid complex. With the addition of OA, the wild-type and guanidinated α-lactalbumin proteins underwent substantial conformational changes, such as partial unfolding, loss of tertiary structure, but retention of secondary structure. In contrast, no significant conformational changes were observed in the citraconylated and acetylated α-lactalbumins, most likely because of the absence of OA binding. These results suggest that electrostatic interactions between the positively-charged basic groups on α-lactalbumin and the negatively-charged carboxylate groups on OA molecules play an essential role in the binding of OA to α-lactalbumin and that these interactions appear to be as important as hydrophobic interactions. Copyright © 2012 Wiley Periodicals, Inc.

  8. Ocorrência do vírus "vein enation (woody gall" em limão verdadeiro (Citrus limon burm. cv siciliano em Santa Catarina Occurrence of the "vein enetion (woody gall" virus in lemon (Citrus limon Burm. cv siciliano in the Santa Catarina state

    Directory of Open Access Journals (Sweden)

    O.L. KOLLER

    1998-01-01

    Full Text Available Relata-se a ocorrência do vírus causador da doença "vein enation", também conhecida por "woody gall", em plantas de limão verdadeiro, em Santa Catarina, introduzido em pomar comercial através de mudas adquiridas em São Paulo. Limão `Volkameriano' enxertado com material contaminado desenvolveu os sintomas característicos de "woody gall", com grande intensidade no Alto Vale do Itajaí, e com menor intensidade no Litoral Norte de Santa Catarina. Constatou-se redução no desenvolvimento das plantas e na produção de frutos. Todo material sabidamente contaminado foi erradicado. Sugere-se às instituições oficiais de pesquisa a realização de testes de indexação para esta virose em seus bancos de germoplasma, uma vez que grande parte das variedades cítricas não desenvolve os sintomas da doença.The presence of the vein enation virus, also known as woody gall virus, in Citrus limon, in Santa Catarina State, is reported. The virus was introduced through contamined nursery plants acquired in the São Paulo State. `Volkamer' lemon budded with contamined buds has developed typical woody gall symptoms, more frequently in Alto Vale do Itajaí (High Itajaí River Valley, and less frequently in Santa Catarina's Northern Coast. A significant decrease in plant development and fruit yield was been observed. All known contaminated material was erradicated. It is suggested that official research institutions carry out indexing tests for this virosis at their germplasm banks, since part of the citrus varieties fail to develop symptoms of this disease.

  9. Behavior Modification in Coaching.

    Science.gov (United States)

    Lynch, Annette Rutt; Stillman, Stephen M.

    1979-01-01

    An example of behavior modification used in athletic coaching is presented. The case study involves a member of a women's basketball team and details the use of behavior modification for both weight reduction and skill improvement. (JMF)

  10. Optimization of the ultrasonic extraction of limonin from Citrus limon seeds by central composite design%中心组合设计优化超声提取柠檬籽中的柠檬苦素

    Institute of Scientific and Technical Information of China (English)

    张霞忠; 王丹; 董垠红; 周文俊

    2016-01-01

    目的 采用中心组合设计优化超声提取柠檬Citrus limon (L.) Burm.f.籽中的柠檬苦素.方法 以乙醇为提取溶剂,超声提取柠檬籽中的柠檬苦素.在单因素试验基础上,中心组合设计对提取工艺进行优化.结果 最佳条件为液固比17∶1,70%乙醇,提取时间33 min,提取温度50 ℃,平均提取率达0.454 5 mg/g.结论 该方法重复性较好,可为柠檬苦素的提取提供一种新方法.

  11. Establishment and Optimization of Genetic Transformation System of Lemon[Citrus limon (L.)Burm.f.]%柠檬遗传转化体系的建立及优化

    Institute of Scientific and Technical Information of China (English)

    仝铸; 何利刚; 吴黎明; 王志静; 蒋迎春; 孙中海

    2014-01-01

    以pCAMBIA1391Z为载体,对农杆菌EHA105介导的柠檬[Citrus limon (L.)Burm.f.]遗传转化体系进行了优化。结果表明,培养基中植物激素的浓度、农杆菌浸染浓度以及浸染后共培养的时间对柠檬的再生和遗传转化效率均有明显影响。1.0 mg/L 6-BA和0.1 mg/L的NAA有利于柠檬上胚轴不定芽的再生,并且再生芽的质量最佳。农杆菌的浸染浓度以OD600 nm=0.6为最佳,浸染后共培养2 d,在含5.0 mg/L潮霉素的筛选培养基上筛选,有利于柠檬不定芽再生率的提高。%Using pCAMBIA1391Z as vector, the genetic transformation system of lemon [Citrus limon (L.) Burm.f.]with A-grobacterium-mediated by EHA105 was optimized. The results showed that concentration of plant hormones, inoculum density and co-cultivation time had significant effects on lemon regeneration and transformation. It was most conducive to the regener-ation of adventitious buds lemon epicotyl by adding 1.0 mg/L 6-BA and 0.1 mg/L NAA in MT medium. The best inoculum density and co-cultivation time were 0.6 (OD600 nm) and two days. For the adventitious bud regeneration of lemon, the most benifical screening concentration of hygromycin was 5.0 mg/L.

  12. Türkiye’de Limon Üretim Bölgesine Yakın Yerlerde Kullanılan Doğal Depoların Mevcut Durumu ile Sıcaklık ve Nem Durumlarının Araştırılması

    Directory of Open Access Journals (Sweden)

    İhsan CANAN

    2015-12-01

    Full Text Available Bu araştırma ile; iki muhafaza sezonu boyunca Mersin ili yayla limon depoları ve Ürgüp Ortahisar’daki depoların iç ve dış sıcaklığı ile oransal nem değerleri incelerek mevcut durumları ortaya konmuş, eksik ve yanlış uygulamalar tespit edilmiş ve halen Ürgüp depolarına götürülen limonların üretim bölgesinde depolanma imkanları araştırılmıştır. Mersin ili yayla limon depoları oransal nem konusunda yeterlidir ancak özellikle Temmuz ve Ağustos aylarında limon depolamak için birkaç derece (15-19 °C sıcaktır. Bu aylarda gerektiğinde serinletme yapılmalıdır. Ortahisar depolarının sıcaklık değerlerinin limon muhafazası için çok uygundur, ancak diğer kalite kriterleri ve derim sonrası kayıpların yayla depoları ile aynı, hatta bazı durumlarda daha fazla olduğu görülmektedir. Ortahisar depolarında yüksek oransal nem vardır ve depo havası yeterince tahliye edilememektedir. Tüm depolarda Aralık ayında limon taşımak için depo içi sıcaklıklar düşüktür ve bu ayda limon taşımak için gerektiğinde ısıtma yapılmalıdır. Tüm depolarda havalandırma sorunları vardır ve havalandırma en iyi olacak şekilde tedbirler alınmalıdır.

  13. Chemical Composition of Different Botanical Origin Honeys Produced by Sicilian Black Honeybees (Apis mellifera ssp. sicula).

    Science.gov (United States)

    Mannina, Luisa; Sobolev, Anatoly P; Di Lorenzo, Arianna; Vista, Silvia; Tenore, Gian Carlo; Daglia, Maria

    2015-07-01

    In 2008 a Slow Food Presidium was launched in Sicily (Italy) for an early warning of the risk of extinction of the Sicilian native breed of black honeybee (Apis mellifera L. ssp sicula). Today, the honey produced by these honeybees is the only Sicilian honey produced entirely by the black honeybees. In view of few available data regarding the chemical composition of A. mellifera ssp. sicula honeys, in the present investigation the chemical compositions of sulla honey (Hedysarum coronarium L.) and dill honey (Anethum graveolens L.) were studied with a multimethodological approach, which consists of HPLC-PDA-ESI-MSn and NMR spectroscopy. Moreover, three unifloral honeys (lemon honey (obtained from Citrus limon (L.) Osbeck), orange honey (Citrus arantium L.), and medlar honey (Eriobotrya japonica (Thunb.) Lindl)), with known phenol and polyphenol compositions, were studied with NMR spectroscopy to deepen the knowledge about sugar and amino acid compositions.

  14. Soy protein modification: A review

    Directory of Open Access Journals (Sweden)

    Barać Miroljub B.

    2004-01-01

    Full Text Available Soy protein products such as flour, concentrates and isolates are used in food formulation because of their functionality, nutritional value and low cost. To obtain their optimal nutritive and functional properties as well as desirable flavor different treatments are used. Soybean proteins can be modified by physical, chemical and enzymatic treatments. Different thermal treatments are most commonly used, while the most appropriate way of modifying soy proteins from the standpoint of safety is their limited proteolysis. These treatments cause physical and chemical changes that affect their functional properties. This review discusses three principal methods used for modification of soy protein products, their effects on dominant soy protein properties and some biologically active compounds.

  15. Post-Translational Modifications of TRP Channels

    Directory of Open Access Journals (Sweden)

    Olaf Voolstra

    2014-04-01

    Full Text Available Transient receptor potential (TRP channels constitute an ancient family of cation channels that have been found in many eukaryotic organisms from yeast to human. TRP channels exert a multitude of physiological functions ranging from Ca2+ homeostasis in the kidney to pain reception and vision. These channels are activated by a wide range of stimuli and undergo covalent post-translational modifications that affect and modulate their subcellular targeting, their biophysical properties, or channel gating. These modifications include N-linked glycosylation, protein phosphorylation, and covalent attachment of chemicals that reversibly bind to specific cysteine residues. The latter modification represents an unusual activation mechanism of ligand-gated ion channels that is in contrast to the lock-and-key paradigm of receptor activation by its agonists. In this review, we summarize the post-translational modifications identified on TRP channels and, when available, explain their physiological role.

  16. Surface Modification of Water Purification Membranes.

    Science.gov (United States)

    Miller, Daniel J; Dreyer, Daniel R; Bielawski, Christopher W; Paul, Donald R; Freeman, Benny D

    2017-04-18

    Polymeric membranes are an energy-efficient means of purifying water, but they suffer from fouling during filtration. Modification of the membrane surface is one route to mitigating membrane fouling, as it helps to maintain high levels of water productivity. Here, a series of common techniques for modification of the membrane surface are reviewed, including surface coating, grafting, and various treatment techniques such as chemical treatment, UV irradiation, and plasma treatment. Historical background on membrane development and surface modification is also provided. Finally, polydopamine, an emerging material that can be easily deposited onto a wide variety of substrates, is discussed within the context of membrane modification. A brief summary of the chemistry of polydopamine, particularly as it may pertain to membrane development, is also described. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Lysine Glutarylation Is a Protein Posttranslational Modification Regulated by SIRT5

    DEFF Research Database (Denmark)

    Tan, Minjia; Peng, Chao; Anderson, Kristin A.

    2014-01-01

    We report the identification and characterization of a five-carbon protein posttranslational modification (PTM) called lysine glutarylation (Kglu). This protein modification was detected by immunoblot and mass spectrometry (MS), and then comprehensively validated by chemical and biochemical metho...

  18. Surface modification of bioceramics

    Science.gov (United States)

    Monkawa, Akira

    Hydroxyapatite [Ca10(PO4)6(OH)2, HAp] is a major inorganic component of bone and teeth tissues and has the excellent biocompatibility and high osteoconductivity. The interactions between HAp and protein or cell have been studied. The HAp related bioceramics such as bone substitute, coating substance of metal implants, inorganic-polymer composites, and cell culture. We described two methods; (1) surface modification of HAp using organosilane; (2) fabrication of HAp ultra-thin layer on gold surface for protein adsorption analyzed with QCM-D technique. The interfacial interaction between collagen and HAp in a nano-region was controlled by depositing the organosilane of n-octadecyltrimethoxysilane (ODS: -CH3) or aminopropyltriethoxysilane (APTS: -NH2) with a chemical vapor deposition method. The morphologies of collagen adsorbed on the surfaces of HAp and HAp deposited with APTS were similar, however that of the surface with ODS was apparently different, due to the hydrophobic interaction between the organic head group of -CH3 and residual groups of collagen. We present a method for coating gold quartz crystal microbalance with dissipation (QCM-D) sensor with ultra-thin layer of hydroxyapatite nanocrystals evenly covering and tightly bound to the surface. The hydroxyapatite sensor operated in liquid with high stability and sensitivity. The in-situ adsorption mechanism and conformational change of fibrinogen on gold, titanium and hydroxyapatite surfaces were investigated by QCM-D technique and Fourier-transform infrared spectroscopy. The study indicates that the hydroxyapatite sensor is applicable for qualitative and conformational analysis of protein adsorption.

  19. Licensing by modification Licensing by modification

    Directory of Open Access Journals (Sweden)

    Veneeta Dayal

    2008-04-01

    Full Text Available Abstract: This paper looks at the phenomena of licensing by modification, whereby an unacceptable noun phrase is redeemed by the presence of a modifier or an unavailable reading for a noun phrase is made available with the addition of a modifier. It argues that an optimal account of such phenomena should derive these effects from the interaction of the meanings of individual expressions in the sentence rather than by positing a formal licensing relation between the modifier and the noun it modifies. The general approach is explicated by considering the distribution of bare plurals in Italian and the availability of generic readings for plural definites in English. The overall goal is a modest one. It seeks to draw attention to properties of modification that go beyond set intersection by focusing on phenomena that have not so far been closely scrutinized in the literature. It uses the particular results to draw some conclusions about questions of general interest.Licensing by modification Abstract: This paper looks at the phenomena of licensing by modification, whereby an unacceptable noun phrase is redeemed by the presence of a modifier or an unavailable reading for a noun phrase is made available with the addition of a modifier. It argues that an optimal account of such phenomena should derive these effects from the interaction of the meanings of individual expressions in the sentence rather than by positing a formal licensing relation between the modifier and the noun it modifies. The general approach is explicated by considering the distribution of bare plurals in Italian and the availability of generic readings for plural definites in English. The overall goal is a modest one. It seeks to draw attention to properties of modification that go beyond set intersection by focusing on phenomena that have not so far been closely scrutinized in the literature. It uses the particular results to draw some conclusions about questions of general

  20. Permit application modifications

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-11-01

    This document contains the Permit Application Modifications for the Y-12 Industrial Landfill V site on the Oak Ridge Reservation. These modifications include the assessment of stability of the proposed Landfill V under static and loading conditions. Analyses performed include the general slope stability, veneer stability of the bottom liner and cover system, and a liquefaction potential assessment of the foundation soils.

  1. A general strategy for the ultrafast surface modification of metals

    OpenAIRE

    Shen, Mingli; Zhu, Shenglong; Wang, Fuhui

    2016-01-01

    Surface modification is an essential step in engineering materials that can withstand the increasingly aggressive environments encountered in various modern energy-conversion systems and chemical processing industries. However, most traditional technologies exhibit disadvantages such as slow diffusion kinetics, processing difficulties or compatibility issues. Here, we present a general strategy for the ultrafast surface modification of metals inspired by electromigration, using aluminizing au...

  2. Modificação química e física do amido de quirera de arroz para aproveitamento na indústria de alimentos Chemical and physical modification of broken rice starch (Oryza sativa L. for use in food industry

    Directory of Open Access Journals (Sweden)

    Valéria Maria Limberger

    2008-01-01

    Full Text Available The study evaluated the efficiency of chemical (phosphorylation and physical (extrusion modifications of the starch of broken rice. Results demonstrated a reduction in the moisture content of extruded and phosphorylated broken rice and an increase in the ash content of phosphorylated broken rice. Both phosphorylation and extrusion increased cold water binding capacity, swelling power, and solubility. Extruded and phosphorylated pastes were stable under refrigeration, but only extruded paste was stable when submitted to freezing. Phosphorylated paste had the lowest viscosity and the highest stability during heating, while the extruded one gelatinized without heating, but had higher losses during heating.

  3. Benign Weather Modification

    Science.gov (United States)

    2007-11-02

    operational interest in modifying weather to support combat operations increased, ultimately leading to a multi-service effort called PROJECT POPEYE . The goal...This, coupled with the revelations concerning weather modification use in the Vietnam War (PROJECT POPEYE ), was a double blow to weather modification...AWS-TR-74-247, June 1984. Cobb, James T., Jr., et. al. Project Popeye : Final Report. China Lake, CA: Naval Weapons Center, 1967. Langmuir, Irving

  4. Antimicrobial Modifications of Polymers

    OpenAIRE

    Sedlarik, Vladimir

    2013-01-01

    This chapter is focused on antimicrobial modifications of polymer materials intended for medical devices production. Firstly, a brief introduction into the field of medical application of polymers is presented. Considering the fact that polymer medical devices are often connected with occurrence of nosocomial infections, the next part refers to this phenomenon and its causes. One of the possibilities of reducing of the infection occurrence is aimed at polymer modification. It is a key topic o...

  5. Modification as a propositional act

    DEFF Research Database (Denmark)

    Rijkhoff, Jan

    2014-01-01

    in Functional Discourse Grammar. Apart from Attitudinal Modification, there are at least five Subacts of Modification that are required for an adequate functional analysis of noun phrases and clauses: classifying modification, qualifying modification, quantifying modification, localizing modification......A complete functional theory of grammar should be able to specify the communicative function of each constituent in a sentence (or rather ‘Discourse Act’). Whereas predicating and referring have been given due attention in functional approaches to grammar, the modifying function of linguistic...

  6. Human Rights and Behavior Modification

    Science.gov (United States)

    Roos, Philip

    1974-01-01

    Criticisms of behavior modification, which charge that it violates ethical and legal principles, are discussed and reasons are presented to explain behavior modification's susceptibility to attack. (GW)

  7. Chemical synthesis on SU-8

    DEFF Research Database (Denmark)

    Qvortrup, Katrine; Taveras, Kennedy; Thastrup, Ole

    2011-01-01

    In this paper we describe a highly effective surface modification of SU-8 microparticles, the attachment of appropriate linkers for solid-supported synthesis, and the successful chemical modification of these particles via controlled multi-step organic synthesis leading to molecules attached...

  8. Chemical synthesis on SU-8.

    Science.gov (United States)

    Qvortrup, Katrine; Taveras, Kennedy M; Thastrup, Ole; Nielsen, Thomas E

    2011-01-28

    In this paper we describe a highly effective surface modification of SU-8 microparticles, the attachment of appropriate linkers for solid-supported synthesis, and the successful chemical modification of these particles via controlled multi-step organic synthesis leading to molecules attached in an unambiguous manner to the support surface.

  9. Aplicación de modelos matemáticos al proceso de secado asistido por infrarrojos de descartes de limón (Citrus limon (L. Burm. F. Cv. Genova

    Directory of Open Access Journals (Sweden)

    Luis Puente-Díaz

    2013-01-01

    Full Text Available Los desechos agroindustriales son uno de los principales problemas ambientales a nivel mundial. Debido a las altas exigencias de calidad, la comercialización de limones de exportación genera grandes cantidades de desechos. Los descartes de limón contienen fibra, pectina, potasio, calcio y vitamina C. Por lo tanto, es importante desarrollar alternativas de procesamiento de estos sub-productos para agregarles valor y aumentar su vida útil. El objetivo de la presente investigación fue la aplicación del secado asistido por infrarrojos, como tecnología emergente, para estudiar el efecto de la temperatura de proceso sobre las cinéticas de secado de descartes de limón a 30, 40 y 50°C. Se utilizaron seis modelos matemáticos de capa fina encontrados en literatura para representar la cinética experimental. Basándose en análisis estadístico, el modelo Logarítmico presentó el mejor ajuste. Los valores de la difusividad efectiva del agua se estimaron en el rango de 9.45× 10-10 – 3.71× 10-9 m/s2. El valor de la energía de activación fue 55.90 kJ/mol.

  10. 毛细管电泳与MALDI-TOF/MS联用测定血清转甲状腺素蛋白的化学修饰%The determination of serum transthyretin chemical modification by capillary electrophoresis combined with MALDI-TOF/MS analysis

    Institute of Scientific and Technical Information of China (English)

    张文亮; 宋林; 李优鑫; 魏殿军; 胡可胜; 孙续国

    2012-01-01

    Objective To establish a combined method for analysis of serum transthyretin ( TTR) chemical modification using capillary electrophoresis ( CE) with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry ( MALDI-TOF/MS) analysis. Methods Enzyme-linked immunosorbent assay ( ELISA) was used to determine serum TTR in 20 senile systemic amyloidosis ( SSA) patients and 20 healthy subjects. Serum TTR was separated by CE. Determination of TTR chemical modification was analyzed by MALDI-TOF/MS. Results The levels of serum TTR was (0. 25 ± 0. 04 ) g/L in control group and (0. 26 ± 0. 03 ) g/L in SSA patients, and there was no significant difference between control group and SSA patients (P > 0. 05). The chemical modification of TTR found 4 TTR chemical modification peaks, as native TTR [mass-to-charge ratio (m/z) : 13 750. 86 ± 1. 48] , sul-TTR ( m/z ratio: 13 830. 63 ±2. 76) , cys-TTR (m/z ratio; 13 871. 70 ±2. 70) and cysgly-TTR (m/z ratio; 13 919.00 + 14.77) by MALDI-TOF/MS analysis. Conclusions The combined method of CE with MALDI-TOF/MS analysis can be used directly to determine the chemical modification of TTR.%目的 建立一种毛细管电泳(CE)与基质辅助激光解吸/电离飞行时间质谱(MALDI-TOF/MS)联用测定血清转甲状腺素蛋白(TTR)化学修饰的方法.方法 用酶联免疫吸附法(ELISA)测定20例老年性淀粉样变( SSA)患者及20名健康体检者血清TTR浓度;CE法分离血清TTR并利用MALDI-TOF/MS测定TTR的化学修饰.结果 健康对照组及SSA组血清TTR浓度分别为0.25±0.04、(0.26 ±0.03) g/L,2组间差异无统计学意义(P> 0.05);MALDI-TOF/MS分析共发现4个TTR化学修饰峰,质/荷比(m/z)分别为:13 750.86±1.48、13 830.63±2.76、13 871.70 ±2.70、13 919.00±14.77;分别对应未修饰-TTR、磺化-TTR、半胱氨酸-TTR和半胱氨酸甘氨酸-TTR.结论 CE法分离血清TTR能够直接利用MALDI-TOF-MS测定其化学修饰,可用于临床检测血清TTR的化学修饰.

  11. Surface Modification for Microreactor Fabrication

    Directory of Open Access Journals (Sweden)

    Wladyslaw Torbicz

    2006-04-01

    Full Text Available In this paper, methods of surface modification of different supports, i.e. glass andpolymeric beads for enzyme immobilisation are described. The developed method ofenzyme immobilisation is based on Schiff’s base formation between the amino groups onthe enzyme surface and the aldehyde groups on the chemically modified surface of thesupports. The surface of silicon modified by APTS and GOPS with immobilised enzymewas characterised by atomic force microscopy (AFM, time-of-flight secondary ion massspectroscopy (ToF-SIMS and infrared spectroscopy (FTIR. The supports withimmobilised enzyme (urease were also tested in combination with microreactors fabricatedin silicon and Perspex, operating in a flow-through system. For microreactors filled withurease immobilised on glass beads (Sigma and on polymeric beads (PAN, a very high andstable signal (pH change was obtained. The developed method of urease immobilisationcan be stated to be very effective.

  12. Identification and Interrogation of Combinatorial Histone Modifications

    Directory of Open Access Journals (Sweden)

    Kelly R Karch

    2013-12-01

    Full Text Available Histone proteins are dynamically modified to mediate a variety of cellular processes including gene transcription, DNA damage repair, and apoptosis. Regulation of these processes occurs through the recruitment of non-histone proteins to chromatin by specific combinations of histone post-translational modifications (PTMs. Mass spectrometry has emerged as an essential tool to discover and quantify histone PTMs both within and between samples in an unbiased manner. Developments in mass spectrometry that allow for characterization of large histone peptides or intact protein has made it possible to determine which modifications occur simultaneously on a single histone polypeptide. A variety of techniques from biochemistry, biophysics, and chemical biology have been employed to determine the biological relevance of discovered combinatorial codes. This review first describes advancements in the field of mass spectrometry that have facilitated histone PTM analysis and then covers notable approaches to probe the biological relevance of these modifications in their nucleosomal context.

  13. Alkyl- and fluoroalkyltrialkoxysilanes for wettability modification

    Energy Technology Data Exchange (ETDEWEB)

    Dopierala, Katarzyna, E-mail: katarzyna.dopierala@put.poznan.pl [Institute of Chemical Technology and Engineering, Poznan University of Technology, Pl. Marii Skłodowskiej-Curie 2, Poznań 60-965 (Poland); Maciejewski, Hieronim [Poznań Science and Technology Park, Rubież 46, Poznań 61-612 (Poland); Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, Poznań 60-780 (Poland); Karasiewicz, Joanna [Poznań Science and Technology Park, Rubież 46, Poznań 61-612 (Poland); Prochaska, Krystyna [Institute of Chemical Technology and Engineering, Poznan University of Technology, Pl. Marii Skłodowskiej-Curie 2, Poznań 60-965 (Poland)

    2013-10-15

    Alkyl- and fluoroalkyltriethoxysilanes were investigated as potential surface modifiers. Many aspects concerning trialkoxysilanes were discussed, starting from hydrolysis of silanes in water solutions, the effect of this hydrolysis on the surface tension, wettability of the modified surface to the morphology of the modified surface. Surface tension and contact angle measurements as well as scanning electron microscopy were used to characterise alkyl- and fluoroalkyltriethoxysilanes and their ability to modify the wettability of glass. The effect of such modification was superhydrophobic surface with high values of contact angles. Superhydrophobic behaviour was observed as a result of two-step modification providing increased surface roughness thanks to the use of different size silica particles and surface chemical modification with fluorosilane molecules.

  14. Structural dynamic modification

    Indian Academy of Sciences (India)

    A Sestieri

    2000-06-01

    Vibration and acoustic requirements are becoming increasingly important in the design of mechanical structures, but they are not usually of primary concern in the design process. So the need to vary the structural behaviour to solve noise and vibration problems often occurs at the prototype stage, giving rise to the so-called structural modification problem. In this paper, the direct problem of determing the new response of a system, after some modifications are introduced into the sestem, is analysed using two different databases: the modal database and the frequency response function database. The limitaions of the modal database are discussed. Structural modifications that can be accounted for are lumped masses, springs, dampers and dynamic absorbers.

  15. Chemical constituents of Parmotrema lichexanthonicum Eliasaro and Alder: isolation, structure modification and evaluation of antibiotic and cytotoxic activities; Constituintes quimicos de Parmotrema lichexanthonicum Eliasaro and Adler: isolamento, modificacoes estruturais e avaliacao das atividades antibiotica e citotoxica

    Energy Technology Data Exchange (ETDEWEB)

    Micheletti, Ana C.; Beatriz, Adilson; Lima, Denis Pires de; Honda, Neli K. [Universidade Federal de Mato Grosso do Sul (UFMS), Campo Grande, MS (Brazil). Dept. de Quimica]. E-mail: nkhonda@nin.ufms.br; Pessoa, Claudia do O; Moraes, Manoel Odorico de; Lotufo, Leticia Veras; Magalhaes, Hemerson Iury Ferreira [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Fisiologia e Farmacologia; Carvalho, Nadia C.P. [Universidade Federal de Mato Grosso do Sul (UFMS), Campo Grande, MS (Brazil). Hospital Universitario. Lab. de Microbiologia

    2009-07-01

    From the lichen Parmotrema lichexantonicum were isolated the depsidone salazinic acid, the xanthone lichexanthone, and the depside atranorin. The two major compounds, salazinic acid and lichexanthone, were selected for structure modifications. Salazinic acid afforded O-alkyl salazinic acids, some of them potentially cytotoxic against tumor cell lines (HCT-8, SF-295 and MDA/ MB - 435). From lichexanthone were obtained norlichexanthone, 3-O-methylnorlichexanthone, 3-O-methyl-6-O-prenylnorlichexanthone, 3,6-di-O-prenyl-norlichexanthone, 3,6-bis[(3,3-dimethyloxyran-2-il)methoxy] -1-hydroxy-8-methyl-9H-xanten-9-one and 3,6-bis[3-(dimethylamine)propoxy]-1-hydroxy-8-methyl- 9H-xanten-9-one. The last compound was the most active against S. aureus. (author)

  16. Organic modification of carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The organic modification of carbon nanotubes is a novel research field being developed recently. In this article, the history and newest progress of organic modification of carbon nanotubes are reviewed from two aspects:organic covalent modification and organic noncovalent modification of carbon nanotubes. The preparation and properties of organic modified carbon nanotubes are discussed in detail. In addition, the prospective development of organic modification of carbon nanotubes is suggested.

  17. Modifications of the chemical structure of phenolics differentially affect physiological activities in pulvinar cells of Mimosa pudica L. II. Influence of various molecular properties in relation to membrane transport.

    Science.gov (United States)

    Rocher, Françoise; Roblin, Gabriel; Chollet, Jean-François

    2017-03-01

    Early prediction of compound absorption by cells is of considerable importance in the building of an integrated scheme describing the impact of a compound on intracellular biological processes. In this scope, we study the structure-activity relationships of several benzoic acid-related phenolics which are involved in many plant biological phenomena (growth, flowering, allelopathy, defense processes). Using the partial least squares (PLS) regression method, the impact of molecular descriptors that have been shown to play an important role concerning the uptake of pharmacologically active compounds by animal cells was analyzed in terms of the modification of membrane potential, variations in proton flux, and inhibition of the osmocontractile reaction of pulvinar cells of Mimosa pudica leaves. The hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA), polar surface area (PSA), halogen ratio (Hal ratio), number of rotatable bonds (FRB), molar volume (MV), molecular weight (MW), and molar refractivity (MR) were considered in addition to two physicochemical properties (logD and the amount of non-dissociated form in relation to pKa). HBD + HBA and PSA predominantly impacted the three biological processes compared to the other descriptors. The coefficient of determination in the quantitative structure-activity relationship (QSAR) models indicated that a major part of the observed seismonasty inhibition and proton flux modification can be explained by the impact of these descriptors, whereas this was not the case for membrane potential variations. These results indicate that the transmembrane transport of the compounds is a predominant component. An increasing number of implicated descriptors as the biological processes become more complex may reflect their impacts on an increasing number of sites in the cell. The determination of the most efficient effectors may lead to a practical use to improve drugs in the control of microbial attacks on plants.

  18. Biblical behavior modification.

    Science.gov (United States)

    Lasure, L C; Mikulas, W L

    1996-07-01

    Although we may have formalized and systematized the field of behavior modification in the last few decades, people around the world have been using behavioral change strategies throughout history. Premack's (1965) theory of reinforcement is often called "Grandma's rule" because grandmothers have long been using it (e.g. You must finish your vegetables before you may go out and play). Franks (1969, p. 4), in one of the first behavioral texts, gave historical examples from China, Turkey, France, and Italy. Knapp and Shodahl (1974) showed how Benjamin Franklin used behavior modification. And de Silva (1984, 1985) gave examples of behavior modification by the Buddha and other early Buddhists. Conspicuously absent from our literature are examples from the Judeo-Christian tradition. In this paper, we provide a number of behavior modification examples from the Bible (New International Version). Footnotes provide references for many more examples. In the discussion, we explore implications for education and therapy. Examples are grouped by the following categories: operant conditioning, respondent conditioning, modeling, and cognitive interventions. However, the Biblical examples, like contemporary case studies, do not always fall neatly into discrete categories. They often are a combination, particularly operant and respondent conditioning interweaving.

  19. Context modification in action

    NARCIS (Netherlands)

    Visser, A.

    2008-01-01

    In this paper we develop the positive fragment of Context Modification Logic. This logical system is a variant of Dynamic Predicate Logic that employs multiple-access variables and that treats argument places in the same way as Latin. The positive fragment is purely incremental.

  20. Posttranslational protein modification in Archaea.

    Science.gov (United States)

    Eichler, Jerry; Adams, Michael W W

    2005-09-01

    One of the first hurdles to be negotiated in the postgenomic era involves the description of the entire protein content of the cell, the proteome. Such efforts are presently complicated by the various posttranslational modifications that proteins can experience, including glycosylation, lipid attachment, phosphorylation, methylation, disulfide bond formation, and proteolytic cleavage. Whereas these and other posttranslational protein modifications have been well characterized in Eucarya and Bacteria, posttranslational modification in Archaea has received far less attention. Although archaeal proteins can undergo posttranslational modifications reminiscent of what their eucaryal and bacterial counterparts experience, examination of archaeal posttranslational modification often reveals aspects not previously observed in the other two domains of life. In some cases, posttranslational modification allows a protein to survive the extreme conditions often encountered by Archaea. The various posttranslational modifications experienced by archaeal proteins, the molecular steps leading to these modifications, and the role played by posttranslational modification in Archaea form the focus of this review.

  1. Evaluation des activités antioxydante et antibactérienne de l’huile essentielle de Citrus limon (variété Lisbon extraite par hydrodistillation

    Directory of Open Access Journals (Sweden)

    Louiza HIMED

    2016-03-01

    Full Text Available La présente étude porte sur l’évaluation des propriétés antioxydante et antibactérienne de l’huile essentielle de Citrus limon (Lisbon extraite par hydrodistillation et analysée par GC-MS. Le pouvoir antioxydant est évalué par le test au DPPH et le test de blanchissement du β-carotène. L’activité antibactérienne vis-à-vis de neuf souches bactériennes (deux à Gram positif et sept à Gram négatif est évaluée par la méthode des aromatogrammes et la méthode de dilution d’agar pour déterminer les CMI. L’extraction a donné un rendement moyen de 1,34±0,012%. Cette huile essentielle a montré des propriétés antioxydante et antibactérienne importantes. La concentration efficace qui réduit 50 % du DPPH en solution est de 0,09±0,001 µg/ml qui exprime une activité antioxydante plus importante que celle de α-tocopherol, ce résultat a été confirmé par le test de blanchissement du β-carotène. Les bactéries testées ont montré une sensibilité à l’huile essentielle. Ces activités sont liées à la richesse de l’huile essentielle en monoterpènes (81,01%.

  2. Geometrically Consistent Mesh Modification

    KAUST Repository

    Bonito, A.

    2010-01-01

    A new paradigm of adaptivity is to execute refinement, coarsening, and smoothing of meshes on manifolds with incomplete information about their geometry and yet preserve position and curvature accuracy. We refer to this collectively as geometrically consistent (GC) mesh modification. We discuss the concept of discrete GC, show the failure of naive approaches, and propose and analyze a simple algorithm that is GC and accuracy preserving. © 2010 Society for Industrial and Applied Mathematics.

  3. Chemical carcinogenesis

    Directory of Open Access Journals (Sweden)

    Paula A. Oliveira

    2007-12-01

    Full Text Available The use of chemical compounds benefits society in a number of ways. Pesticides, for instance, enable foodstuffs to be produced in sufficient quantities to satisfy the needs of millions of people, a condition that has led to an increase in levels of life expectancy. Yet, at times, these benefits are offset by certain disadvantages, notably the toxic side effects of the chemical compounds used. Exposure to these compounds can have varying effects, ranging from instant death to a gradual process of chemical carcinogenesis. There are three stages involved in chemical carcinogenesis. These are defined as initiation, promotion and progression. Each of these stages is characterised by morphological and biochemical modifications and result from genetic and/or epigenetic alterations. These genetic modifications include: mutations in genes that control cell proliferation, cell death and DNA repair - i.e. mutations in proto-oncogenes and tumour suppressing genes. The epigenetic factors, also considered as being non-genetic in character, can also contribute to carcinogenesis via epigenetic mechanisms which silence gene expression. The control of responses to carcinogenesis through the application of several chemical, biochemical and biological techniques facilitates the identification of those basic mechanisms involved in neoplasic development. Experimental assays with laboratory animals, epidemiological studies and quick tests enable the identification of carcinogenic compounds, the dissection of many aspects of carcinogenesis, and the establishment of effective strategies to prevent the cancer which results from exposure to chemicals.A sociedade obtém numerosos benefícios da utilização de compostos químicos. A aplicação dos pesticidas, por exemplo, permitiu obter alimento em quantidade suficiente para satisfazer as necessidades alimentares de milhões de pessoas, condição relacionada com o aumento da esperança de vida. Os benefícios estão, por

  4. Involvement of cytoskeletal proteins in the barrier function of the human erythrocyte membrane. III. Permeability of spectrin-depleted inside-out membrane vesicles to hydrophilic nonelectrolytes. Formation of leaks by chemical or enzymatic modification of membrane proteins.

    Science.gov (United States)

    Klonk, S; Deuticke, B

    1992-04-29

    Spectrin-depleted inside-out vesicles (IOV's) prepared from human erythrocyte membranes were characterized in terms of size, ground permeability to hydrophilic nonelectrolytes and their sensitivity to modification by SH reagents, DIDS and trypsin. IOV's proved to have the same permeability of their lipid domain to erythritol as native erythrocytes, in contrast to resealed ghosts (Klonk, S. and Deuticke, B. (1992) Biochim. Biophys. Acta 1106, 126-136 (Part I in this series)), which have a residual leak. On the other hand, IOV's have a slightly elevated permeability for mannitol and sucrose, nonelectrolytes which are almost (mannitol) or fully (sucrose) impermeant in the native membrane. These increased fluxes, which have a high activation energy and can be stimulated by phloretin, are, however, also much smaller than the corresponding leak fluxes observed in resealed ghosts. In view of these differences, formation of IOV's can be concluded to go along with partial annealing of barrier defects persisting in the erythrocyte membrane after preparation of resealed ghosts. Oxidation of SH groups of the IOV membrane by diamide produces an enhancement of permeability for hydrophilic nonelectrolytes which is much less pronounced than that induced by a similar treatment of erythrocytes or ghosts (Klonk, S. and Deuticke, B. (1992) Biochim. Biophys. Acta 1106, 126-136 (Part I in this series)). Moreover, proteolytic treatment of the vesicle membrane, although leading to a marked digestion of integral membrane proteins, only induces a minor, saturating increase of permeability, much lower than that in trypsinized resealed ghosts (Klonk, S. and Deuticke, B. (1992) Biochim. Biophys. Acta 1106, 137-142 (Part II of this series)). Since absence of the cytoskeletal proteins, spectrin and actin, is the major difference between IOV's and resealed ghosts, these results may be taken as further evidence for a dependence of the barrier properties of the erythrocyte membrane bilayer domain

  5. Enzymatic modification of phospholipids forfunctional applications and human nutrition

    DEFF Research Database (Denmark)

    Guo, Zheng; Vikbjerg, Anders / Falk; Xu, Xuebing

    2005-01-01

    Rapid progress in biochemistry of phospholipids and evolution of modern bioengineering has brought forth a number of novel concepts and technical advancements in the modification of phospholipids for industrial applications and human nutrition. Highlights cover preparation of novel phospholipid...... analogs based on the latest understanding of pivotal role of phospholipids in manifold biological processes, exploration of remarkable application potentials of phospholipids in meliorating human health, as well as development of new chemical and biotechnological approaches applied to the modification...

  6. Thermal modification of birch using saturated and superheated steam

    OpenAIRE

    Dagbro, Ola; Torniainen, Petteri; Morén, Tom

    2011-01-01

    During the thermal modification, wood is normally exposed to temperatures between 160 - 220°C. As a result physical and chemical changes are taking place and some of the wood properties are changed. Dimensional stability and weather resistance are improved. On the other hand the mechanical strength properties are usually negatively affected by the treatment. The visual appearance is also changed. There were two different types of thermal modification processes used in this study. One of them ...

  7. Synthesis and chemical modification of polymeric resins for the treatment of cations and aromatic hydrocarbons in produced oily water; Sintese de modificacao quimica de resina polimerica e aplicacao na remocao de cations e hidrocarbonetos aromaticos presentes em agua produzida

    Energy Technology Data Exchange (ETDEWEB)

    Aversa, Thiago M.; Rodrigues, Monique F.; Vieira, Helida V.P.; Queiros, Yure G.C.; Lucas, Elizabete F. [Universidade Federal do Rio de Janeiro, Instituto de Macromoleculas, Lab. de Macromoleculas e Coloides na Industria do Petroleo, Rio de Janeiro, RJ (Brazil)], e-mail: thiagoaversa@ima.ufrj.br

    2011-07-01

    The use of chemically modified resins in oily water treatment process is not very developed yet. Because of this, this work suggests to study the styrene and divinylbenzene sulfonation effect on oil and grease, aniline and calcium removal from the water. The aniline, oils and greases belong to a class of toxic organic compounds, with the Brazilian maximum limits established for disposal in CONAMA 393/2007, while the calcium ions belong to the group of cations of alkaline earth metals which improve hardness to the water, may cause fouling as carbonates and sulfates form. By using sulfonated resins in oily water treatment it is possible to remove not only oils and greases but also calcium and aniline. These kinds of polar compounds are removed because of the cation exchange capacity of resin. (author)

  8. Modification of carbon screen-printed electrodes by adsorption of chemically synthesized Bi nanoparticles for the voltammetric stripping detection of Zn(II), Cd(II) and Pb(II).

    Science.gov (United States)

    Rico, Ma Angeles Granado; Olivares-Marín, Mara; Gil, Eduardo Pinilla

    2009-12-15

    A simple procedure for the chemical synthesis of bismuth nanoparticles and subsequent adsorption on commercial screen-printed carbon electrodes offer reliable quantitation of trace zinc, cadmium and lead by anodic stripping square-wave voltammetry in nondeareated water samples. The influence of two hydrodynamic configurations (convective cell and flow cell) and the effect of various experimental variables upon the stripping signals at the bismuth-coated sensor are explored. The square-wave peak current signal is linear over the low ng mL(-1) range (120 s deposition), with detections limits ranging from 0.9 to 4.9 ng mL(-1) and good precision. Applicability to waste water certified reference material and drinking water samples is demonstrated. The attractive behaviour of the new disposable Bi nanoparticles modified carbon strip electrodes, coupled with the negligible toxicity of bismuth, hold great promise for decentralized heavy metal testing in environmental and industrial effluents waters.

  9. Starch--value addition by modification.

    Science.gov (United States)

    Tharanathan, Rudrapatnam N

    2005-01-01

    Starch is one of the most important but flexible food ingredients possessing value added attributes for innumerable industrial applications. Its various chemically modified derivatives offer a great scope of high technological value in both food and non-food industries. Modified starches are designed to overcome one or more of the shortcomings, such as loss of viscosity and thickening power upon cooking and storage, particularly at low pH, retrogradation characteristics, syneresis, etc., of native starches. Oxidation, esterification, hydroxyalkylation, dextrinization, and cross-linking are some of the modifications commonly employed to prepare starch derivatives. In a way, starch modification provides desirable functional attributes as well as offering economic alternative to other hydrocolloid ingredients, such as gums and mucilages, which are unreliable in quality and availability. Resistant starch, a highly retrograded starch fractionformed upon food processing, is another useful starch derivative. It exhibits the beneficial physiological effects of therapeutic and nutritional values akin to dietary fiber. There awaits considerable opportunity for future developments, especially for tailor-made starch derivatives with multiple modifications and with the desired functional and nutritional properties, although the problem of obtaining legislative approval for the use of novel starch derivatives in processed food formulations is still under debate. Nevertheless, it can be predicted that new ventures in starch modifications and their diverse applications will continue to be of great interest in applied research.

  10. Polylactic acid (PLA) synthesis and modifications: a review

    Institute of Scientific and Technical Information of China (English)

    Yanling CHENG; Shaobo DENG; Paul CHEN; Roger RUAN

    2009-01-01

    This article reviews various methods of synthesizing polycondensation and ring-opening polymerization and modifying properties of polylactic acid (PLA), which may be used as biomaterials, such as a drug carrier in a drug delivery system, as a cell scaffold and suture in tissue engineering, and as packaging materials in packaging engineering field. Copolymerization of lactide with other monomers or polymers such as malic acid, polyethylene glycol (PEG), polyglycolic acid (PGA), or dextran, as well as blending polylactide with natural derivatives and other methods of modification are discussed. Surface modifications of PLA-type copolymers, such as surface coating,chemical modification, and plasma treatment are described.

  11. Chromatin modifications, epigenetics, and how protozoan parasites regulate their lives.

    Science.gov (United States)

    Croken, Matthew M; Nardelli, Sheila C; Kim, Kami

    2012-05-01

    Chromatin structure plays a vital role in epigenetic regulation of protozoan parasite gene expression. Epigenetic gene regulation impacts upon parasite virulence, differentiation and cell-cycle control. Recent work in many laboratories has elucidated the functions of proteins that regulate parasite gene expression by chemical modification of constituent nucleosomes. A major focus of investigation has been the characterization of post-translational modifications (PTMs) of histones and the identification of the enzymes responsible. Despite conserved features and specificity common to all eukaryotes, parasite enzymes involved in chromatin modification have unique functions that regulate unique aspects of parasite biology.

  12. Surface modification: advantages, techniques, and applications

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.

    2000-03-01

    Adequate performance of materials at elevated temperatures is a potential problem in many systems within the chemical, petroleum, process, and power-generating industries. Degradation of materials occurs because of interaction between the structural material and the exposure environment. These interactions are generally undesired chemical reactions that can lead to accelerated wastage and alter the functional requirements and/or structural integrity of the materials. Therefore, material selection for high-temperature applications must be based not only on a material strength properties but also on resistance to the complex environments prevalent in the anticipated exposure environment. As plants become larger, the satisfactory performance and reliability of components play a greater role in plant availability and economics. However, system designers are becoming increasingly concerned with finding the least expensive material that will satisfactorily perform the design function for the desired service life. This present paper addresses the benefits of surface modification and identified several criteria for selection and application of modified surfaces in the power sector. A brief review is presented on potential methods for modification of surfaces, with the emphasis on coatings. In the final section of the paper, several examples address the requirements of different energy systems and surface modification avenues that have been applied to resolve the issues.

  13. In vitro study of morphological and chemical modification threshold of bovine dental enamel irradiated by the holmium laser; Estudo in vitro das alteracoes morfologicas e quimicas do esmalte dental bovino irradiado pelo laser de holmio

    Energy Technology Data Exchange (ETDEWEB)

    Eduardo, Patricia Lerro de Paula

    2001-07-01

    The aim of this study is to investigate the Ho:YLF laser effects on the dental enamel surface with regards to its morphology, thermal variations during its irradiation in the pulp chamber and its increased resistance to demineralization through quantitative analysis of calcium and phosphorous atoms reactive concentrations in samples. Twenty samples of bovine enamel were used and divided in four groups: control - acidulated phosphate fluoride (APF) application followed by demineralization treatment with lactic acid; irradiation with Ho:YLF laser (100 J/cm{sup 2}) followed by APF topic application and demineralization treatment with lactic acid; irradiation with Ho:YLF laser (350 J/cm{sup 2}) followed by APF topic application and demineralization treatment with lactic acid: and irradiation with Ho:YLF laser ( 450 J/cm{sup 2}) followed by APF topic application and demineralization treatment with lactic acid. Ali samples were quantified according to their calcium and phosphorous atoms relative concentrations before and after the treatments above. X-Ray fluorescence spectrochemical analysis and scanning electron microscopy were carried out. It was observed an increase on the calcium and phosphorous atoms concentration ratio and therefore the enamel demineralization reduction as a result of the lactic acid treatment in the samples irradiated with the holmium laser followed by the APF application. In order to evaluate the feasibility of this study for clinical purposes, morphological changes caused by the holmium laser irradiation were analyzed. Such modifications were characterized by melted and re-solidified regions of the enamel with consequent changes on its permeability and solubility. Temperature changes of ten human pre-molars teeth irradiated with 350 J/cm{sup 2} and 450 J/cm{sup 2} were also monitored in the pulp chamber in real time. Temperature increases over 4,20 C did not occur. The results obtained from this study along with the results from previous

  14. Genetic modification and genetic determinism.

    Science.gov (United States)

    Resnik, David B; Vorhaus, Daniel B

    2006-06-26

    In this article we examine four objections to the genetic modification of human beings: the freedom argument, the giftedness argument, the authenticity argument, and the uniqueness argument. We then demonstrate that each of these arguments against genetic modification assumes a strong version of genetic determinism. Since these strong deterministic assumptions are false, the arguments against genetic modification, which assume and depend upon these assumptions, are therefore unsound. Serious discussion of the morality of genetic modification, and the development of sound science policy, should be driven by arguments that address the actual consequences of genetic modification for individuals and society, not by ones propped up by false or misleading biological assumptions.

  15. Chitosan Modification and Pharmaceutical/Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Jiali Zhang

    2010-06-01

    Full Text Available Chitosan has received much attention as a functional biopolymer for diverse applications, especially in pharmaceutics and medicine. Our recent efforts focused on the chemical and biological modification of chitosan in order to increase its solubility in aqueous solutions and absorbability in the in vivo system, thus for a better use of chitosan. This review summarizes chitosan modification and its pharmaceutical/biomedical applications based on our achievements as well as the domestic and overseas developments: (1 enzymatic preparation of low molecular weight chitosans/chitooligosaccharides with their hypocholesterolemic and immuno-modulating effects; (2 the effects of chitin, chitosan and their derivatives on blood hemostasis; and (3 synthesis of a non-toxic ion ligand—D-Glucosaminic acid from Oxidation of D-Glucosamine for cancer and diabetes therapy.

  16. Chitosan Modification and Pharmaceutical/Biomedical Applications

    Science.gov (United States)

    Zhang, Jiali; Xia, Wenshui; Liu, Ping; Cheng, Qinyuan; Tahirou, Talba; Gu, Wenxiu; Li, Bo

    2010-01-01

    Chitosan has received much attention as a functional biopolymer for diverse applications, especially in pharmaceutics and medicine. Our recent efforts focused on the chemical and biological modification of chitosan in order to increase its solubility in aqueous solutions and absorbability in the in vivo system, thus for a better use of chitosan. This review summarizes chitosan modification and its pharmaceutical/biomedical applications based on our achievements as well as the domestic and overseas developments: (1) enzymatic preparation of low molecular weight chitosans/chitooligosaccharides with their hypocholesterolemic and immuno-modulating effects; (2) the effects of chitin, chitosan and their derivatives on blood hemostasis; and (3) synthesis of a non-toxic ion ligand—D-Glucosaminic acid from Oxidation of D-Glucosamine for cancer and diabetes therapy. PMID:20714418

  17. Mechanism of Surface Modification for Sericite

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Surface modification of sericite by wet method was conducted with the addition of 1.0% (w/w) silane. The resulting wetting contact angle and activity ratio of sericite were 130° and 98% respectively.Good pre-evaluation indexes of oil value (40.8%) and dispersivity (14.0 mL) were obtained. When 30% of sericite was filled into acrylonitrile butadiene styrene(ABS) plastic, the bending strength and tensile strength of the composite material were reduced by 7% and 14.3% in comparison to those of pure ABS plastic, while the rigidity was increased by 3 times, and the impact strength and breaking elongation were reduced significantly.The mechanism of surface modification was investigated and the configuration of silane coupling agent on the surface of sericite was given. Infrared (IR) spectroscopic analysis indicates that the adsorption of silane on the surface of sericite belongs to chemical adsorption.

  18. Quantitative proteomic approaches to studying histone modifications.

    Science.gov (United States)

    Zee, Barry M; Young, Nicolas L; Garcia, Benjamin A

    2011-01-01

    Histone post-translational modifications (PTMs) positively and negatively regulate gene expression, and are consequently a vital influence on the genomic profile of all eukaryotic species. The study of histone PTMs using classical methods in molecular biology, such as immunofluorescence and Western blotting, is challenging given the technical issues of the approaches, and chemical diversity and combinatorial patterns of the modifications. In light of these many technical limitations, mass spectrometry (MS) is emerging as the most unbiased and rigorous experimental platform to identify and quantify histone PTMs in a high-throughput manner. This review covers the latest developments in mass spectrometry for the analysis of histone PTMs, with the hope of inspiring the continued integration of proteomic, genomic and epigenetic research.

  19. Bioactive Surface Modification of Hydroxyapatite

    Directory of Open Access Journals (Sweden)

    Yasuhiko Abe

    2013-01-01

    Full Text Available The purpose of this study was to establish an acid-etching procedure for altering the Ca/P ratio of the nanostructured surface of hydroxyapatite (HAP by using surface chemical and morphological analyses (XPS, XRD, SEM, surface roughness, and wettability and to evaluate the in vitro response of osteoblast-like cells (MC3T3-E1 cells to the modified surfaces. This study utilized HAP and HAP treated with 10%, 20%, 30%, 40%, 50%, or 60% phosphoric acid solution for 10 minutes at 25°C, followed by rinsing 3 times with ultrapure water. The 30% phosphoric acid etching process that provided a Ca/P ratio of 1.50, without destruction of the grain boundary of HAP, was selected as a surface-modification procedure. Additionally, HAP treated by the 30% phosphoric acid etching process was stored under dry conditions at 25°C for 12 hours, and the Ca/P ratio approximated to 1.00 accidentally. The initial adhesion, proliferation, and differentiation (alkaline phosphatase (ALP activity and relative mRNA level for ALP of MC3T3-E1 cells on the modified surfaces were significantly promoted (P<0.05 and 0.01. These findings show that the 30% phosphoric acid etching process for the nanostructured HAP surface can alter the Ca/P ratio effectively and may accelerate the initial adhesion, proliferation, and differentiation of MC3T3-E1 cells.

  20. Apparatus and methods for detecting chemical permeation

    Science.gov (United States)

    Vo-Dinh, Tuan

    1994-01-01

    Apparatus and methods for detecting the permeation of hazardous or toxic chemicals through protective clothing are disclosed. The hazardous or toxic chemicals of interest do not possess the spectral characteristic of luminescence. The apparatus and methods utilize a spectrochemical modification technique to detect the luminescence quenching of an indicator compound which upon permeation of the chemical through the protective clothing, the indicator is exposed to the chemical, thus indicating chemical permeation.