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Sample records for acids molecular weight

  1. Production of high molecular weight polylactic acid

    SciTech Connect

    Bonsignore, P.V.

    1995-11-28

    A degradable high molecular weight poly(lactic acid) is described. The poly(lactic acid) has a terminal end group of one of carboxyl or hydroxyl groups with low molecular weight poly(lactic acid) units coupled with linking agents of di-isocyanates, bis-epoxides, bis-oxazolines and bis-ortho esters. The resulting high molecular weight poly(lactic acid) can be used for applications taking advantage of the improved physical properties.

  2. Production of high molecular weight polylactic acid

    SciTech Connect

    Bonsignore, Patrick V.

    1995-01-01

    A degradable high molecular weight poly(lactic acid). A poly(lactic acid) has a terminal end group of one of carboxyl or hydroxyl groups with low molecular weight poly(lactic acid) units coupled with linking agents of di-isocyanates, bis-epoxides, bis-oxazolines and bis-ortho esters. The resulting high molecular weight poly(lactic acid) can be used for applications taking advantage of the improved physical properties.

  3. Biodegradation of high molecular weight polylactic acid

    NASA Astrophysics Data System (ADS)

    Stloukal, Petr; Koutny, Marek; Sedlarik, Vladimir; Kucharczyk, Pavel

    2012-07-01

    Polylactid acid seems to be an appropriate replacement of conventional non-biodegradable synthetic polymer primarily due to comparable mechanical, thermal and processing properties in its high molecular weight form. Biodegradation of high molecular PLA was studied in compost for various forms differing in their specific surface area. The material proved its good biodegradability under composting conditions and all investigated forms showed to be acceptable for industrial composting. Despite expectations, no significant differences in resulting mineralizations were observed for fiber, film and powder sample forms with different specific surface areas. The clearly faster biodegradation was detected only for the thin coating on porous material with high specific surface area.

  4. Molecular weight of aquatic fulvic acids by vapor pressure osmometry

    USGS Publications Warehouse

    Aiken, G.R.; Malcolm, R.L.

    1987-01-01

    The molecular weights of aquatic fulvic acids extracted from five rivers were determined by vapor pressure osmometry with water and tetrahydrofuran as solvents. The values obtained ranged from 500 to 950 dallons, indicating that the molecular weights of aquatic fulvic acids are not as great as has been suggested in some other molecular weight studies. The samples were shown to be relatively monodisperse from radii of gyration measurements determined by small angle x-ray scattering. THF affords greater precision and accuracy than H2O in VPO measurements, and was found to be a suitable solvent for the determination of molecular weight of aquatic fulvic acid because it obviates the dissociation problem. An inverse correlation was observed with these samples between the concentration of Ca++ and Mg++ in the river water and the radii of gyration and molecular weights of the corresponding fulvic acid samples. ?? 1987.

  5. High Molecular Weight Hyaluronic Acid Inhibits Fibrosis of Endometrium

    PubMed Central

    Zhu, Yi; Hu, Jianguo; Yu, Tinghe; Ren, Yan; Hu, Lina

    2016-01-01

    Background Elevated fibrosis has been found in patients with intrauterine adhesion, which indicates that fibrotic factors may play a critical role in formation of intrauterine adhesion. The aim of this study was to identify the effect of hyaluronic acid (HA) at high and low molecular weight on fibrosis of the endometrium in a mouse model of Asherman’s syndrome. Material/Methods Endometrial fibrosis in a mouse model of Asherman’s syndrome was confirmed. Then HA at high and low molecular weight was injected into the uterine cavity. Endometrial fibrosis was compared among the control group, LMW-HA, and HMW-HA group. The extent of endometrial fibrosis was calculated using Masson stain. The fibrosis markers (TGFβ1, CTGF, collagen I, and collagen III) in endometrial tissue were detected using immunohistochemistry and Western blotting. Results The ratio of the area with endometrial fibrosis to total endometrial area in the HMW-HA group was significantly decreased compared to the control group (P<0.05). The expression of fibrosis markers (TGFβ1, CTGF, collagen I, and collagen III) in the endometrium was attenuated in the HMW-HA group compared to the control group, but the LMW-HA group had no similar effect. Conclusions Hyaluronic acid at high molecular weight may attenuate the degree of endometrial fibrosis after endometrial damage, which may contribute to preventing formation of intrauterine adhesions. PMID:27670361

  6. Determination of the presence of hyaluronic acid in preparations containing amino acids: the molecular weight characterization.

    PubMed

    Bellomaria, A; Nepravishta, R; Mazzanti, U; Marchetti, M; Piccioli, P; Paci, M

    2014-10-15

    Several pharmaceutical preparations contain hyaluronic acid in the presence of a large variety of low molecular weight charged molecules like amino acids. In these mixtures, it is particularly difficult to determine the concentration and the molecular weight of the hyaluronic acid fragments. In fact zwitterionic compounds in high concentration behave by masking the hyaluronic acid due to the electrostatic interactions between amino acids and hyaluronic acid. In such conditions the common colorimetric test of the hyaluronic acid determination appears ineffective and in the (1)H NMR spectra the peaks of the polymer disappear completely. By a simple separation procedure the presence of hyaluronic acid was revealed by the DMAB test and (1)H NMR while its average molecular weight in the final product was determined by DOSY NMR spectroscopy alone. The latter determination is very important due to the healthy effects of some sizes of this polymer's fragments. PMID:25078662

  7. Preparation of low-molecular-weight hyaluronic acid by ozone treatment.

    PubMed

    Wu, Yue

    2012-06-20

    Recently, low-molecular-weight hyaluronic acid has been reported to have novel features, such as free radical scavenging activities, antioxidant activities, promotion of excisional wound healing, etc. In the present work, degradation of native hyaluronic acid by ozone treatment was performed for preparation of low-molecular-weight hyaluronic acid. The molecular weight of native hyaluronic acid was reduced from 1535 to 87 kDa for 120 min at 40°C. The rate of reduction of molecular weight was 94.33%. The FT-IR, 13C NMR, and UV-vis spectra suggested that there was no obvious modification of chemical structure of low-molecular-weight hyaluronic acid. The use of degradation of native hyaluronic acid by ozone treatment can be a useful alternative for production of low-molecular-weight hyaluronic acid.

  8. Association between cationic liposomes and low molecular weight hyaluronic acid.

    PubMed

    Gasperini, Antonio A M; Puentes-Martinez, Ximena E; Balbino, Tiago Albertini; Rigoletto, Thais de Paula; Corrêa, Gabriela de Sá Cavalcanti; Cassago, Alexandre; Portugal, Rodrigo Villares; de La Torre, Lucimara Gaziola; Cavalcanti, Leide P

    2015-03-24

    This work presents a study of the association between low molecular weight hyaluronic acid (16 kDa HA) and cationic liposomes composed of egg phosphatidylcholine (EPC), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). The cationic liposome/HA complexes were evaluated to determine their mesoscopic structure, average size, zeta potential, and morphology as a function of the amount of HA in the system. Small angle X-ray scattering results revealed that neighboring cationic liposomes either stick together after a partial coating of low concentration HA or disperse completely in excess of HA, but they never assemble as multilamellar vesicles. Cryo-transmission electron microscopy images confirm the existence of unilamellar vesicles and large aggregates of unilamellar vesicles for HA fractions up to 80% (w/w). High concentrations of HA (> 20% w/w) proved to be efficient for coating extruded liposomes, leading to particle complexes with sizes in the nanoscale range and a negative zeta potential.

  9. Molecular dynamics simulations on the interactions of low molecular weight natural organic acids with C60.

    PubMed

    Sun, Qian; Xie, Hong-Bin; Chen, Jingwen; Li, Xuehua; Wang, Zhuang; Sheng, Lianxi

    2013-07-01

    As an important part of dissolved organic matter (DOM), low molecular weight organic acids (LOAs) may play a key role in the process for DOM stabilizing carbon nanomaterials (e.g. C60) suspensions in aquatic environment. In addition, both LOAs and C60 have been detected in the troposphere and therefore have a chance to interact with each other in the gaseous phase. However, the mechanism for LOAs-C60 interactions and their environmental implications need further investigations. In this study, molecular dynamics (MD) simulation was employed to investigate the interactions between both neutral and ionic LOAs with C60 in vacuum and water. The results showed that the adsorptions of all LOAs on C60 in energy are favorable, and the aromatic acids have stronger interactions with C60 than the aliphatic acids in vacuum and water. The interaction energies (Eint) of the LOA anions with C60 were weaker than those of their corresponding neutral LOA molecules. The models were also developed to predict and interpret Eint based on the results from MD simulations. Dispersion, induction and hydrophobic interactions were found to be the dominating factor in Eint. These findings indicate that cost-efficient MD simulation can be employed as an important tool to predict the adsorption behavior of LOAs on carbon nanomaterials.

  10. Effect of hyaluronic acid molecular weight on the morphology of quantum dot-hyaluronic acid conjugates.

    PubMed

    Kim, Jiseok; Park, Kitae; Hahn, Sei Kwang

    2008-01-01

    The morphological analysis of novel quantum dot-hyaluronic acid (QDot-HA) conjugates was carried out with a transmission electron microscope (TEM). Adipic acid dihydrazide-modified HA (HA-ADH) was synthesized and conjugated to quantum dots (QDots) having carboxyl terminal ligands which were activated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysulfosuccinimide (sulfo-NHS). HA molecules with a molecular weight (MW) of 20K, 234 K and 3000 K were used to investigate the effect of MW on the morphology of QDot-HA conjugates. The TEM micrographs of QDot-HA conjugates showed branched and multi-layered chain type morphology formed by inter- and intra-molecular conjugation of QDots to HA molecules. The size of QDot-HA conjugate increased with the MW of HA. QDot-HA conjugate could be successfully used for real-time bio-imaging of HA derivatives in nude mice. The novel QDot-HA conjugate will be further used to investigate the biological roles of HA with a different MW in the body. PMID:17936350

  11. Effect of oxygen and shear stress on molecular weight of hyaluronic acid.

    PubMed

    Duan, Xu-Jie; Yang, Li; Zhang, Xu; Tan, Wen-Song

    2008-04-01

    Dissolved oxygen (DO) and shear stress have pronounced effects on hyaluronic acid (HA) production, yet various views persist about their effect on the molecular weight of HA. Accordingly, this study investigated the effects of DO and shear stress during HA fermentation. The results showed that both cell growth and HA synthesis were suppressed under anaerobic conditions, and the HA molecular mass was only (1.22+/-0.02) x 106 Da. Under aerobic conditions, although the DO level produced no change in the biomass or HA yield, a high DO level favored the HA molecular mass, which reached a maximum value of (2.19+/- 0.05) x 106 Da at 50% DO. Furthermore, a high shear stress delayed the rate of HA synthesis and decreased the HA molecular weight, yet had no clear effect on the HA yield. Therefore, a high DO concentration and mild shear environment would appear to be essential to enhance the HA molecular weight.

  12. Low-molecular-weight carboxylic acids produced from hydrothermal treatment of organic wastes.

    PubMed

    Quitain, Armando T; Faisal, Muhammad; Kang, Kilyoon; Daimon, Hiroyuki; Fujie, Koichi

    2002-07-22

    This article reports production of low-molecular-weight carboxylic acids from the hydrothermal treatment of representative organic wastes and compounds (i.e. domestic sludge, proteinaceous, cellulosic and plastic wastes) with or without oxidant (H(2)O(2)). Organic acids such as acetic, formic, propionic, succinic and lactic acids were obtained in significant amounts. At 623 K (16.5 MPa), acetic acid of about 26 mg/g dry waste fish entrails was obtained. This increased to 42 mg/g dry waste fish entrails in the presence of H(2)O(2). Experiments on glucose to represent cellulosic wastes were also carried out, getting acetic acid of about 29 mg/g glucose. The study was extended to terephthalic acid and glyceraldehyde, reaction intermediates of hydrothermal treatment of polyethylene terephthalate (PET) plastic wastes and glucose, respectively. In addition, production of lactic acid, one of the interesting low-molecular-weight carboxylic acids, was discussed on the viewpoint of resources recovery. Studies on temperature dependence of formation of organic acids showed thermal stability of acetic acid, whereas, formic acid decomposed readily under hydrothermal conditions. In general, results demonstrated that the presence of oxidants favored formation of organic acids with acetic acid being the major product.

  13. Rheology, oxygen transfer, and molecular weight characteristics of poly(glutamic acid) fermentation by Bacillus subtilis.

    PubMed

    Richard, Andrew; Margaritis, Argyrios

    2003-05-01

    Poly(glutamic acid) (PGA) is a water-soluble, biodegradable biopolymer that is produced by microbial fermentation. Recent research has shown that PGA can be used in drug delivery applications for the controlled release of paclitaxel (Taxol) in cancer treatment. A fundamental understanding of the key fermentation parameters is necessary to optimize the production and molecular weight characteristics of poly(glutamic acid) by Bacillus subtilis for paclitaxel and other applications of pharmaceuticals for controlled release. Because of its high molecular weight, PGA fermentation broths exhibit non-Newtonian rheology. In this article we present experimental results on the batch fermentation kinetics of PGA production, mass transfer of oxygen, specific oxygen uptake rate, broth rheology, and molecular weight characterization of the PGA biopolymer.

  14. A log-normal distribution model for the molecular weight of aquatic fulvic acids

    USGS Publications Warehouse

    Cabaniss, S.E.; Zhou, Q.; Maurice, P.A.; Chin, Y.-P.; Aiken, G.R.

    2000-01-01

    The molecular weight of humic substances influences their proton and metal binding, organic pollutant partitioning, adsorption onto minerals and activated carbon, and behavior during water treatment. We propose a lognormal model for the molecular weight distribution in aquatic fulvic acids to provide a conceptual framework for studying these size effects. The normal curve mean and standard deviation are readily calculated from measured M(n) and M(w) and vary from 2.7 to 3 for the means and from 0.28 to 0.37 for the standard deviations for typical aquatic fulvic acids. The model is consistent with several types of molecular weight data, including the shapes of high- pressure size-exclusion chromatography (HP-SEC) peaks. Applications of the model to electrostatic interactions, pollutant solubilization, and adsorption are explored in illustrative calculations.The molecular weight of humic substances influences their proton and metal binding, organic pollutant partitioning, adsorption onto minerals and activated carbon, and behavior during water treatment. We propose a log-normal model for the molecular weight distribution in aquatic fulvic acids to provide a conceptual framework for studying these size effects. The normal curve mean and standard deviation are readily calculated from measured Mn and Mw and vary from 2.7 to 3 for the means and from 0.28 to 0.37 for the standard deviations for typical aquatic fulvic acids. The model is consistent with several type's of molecular weight data, including the shapes of high-pressure size-exclusion chromatography (HP-SEC) peaks. Applications of the model to electrostatic interactions, pollutant solubilization, and adsorption are explored in illustrative calculations.

  15. Isoleucine epimerization and amino acid composition in molecular-weight separations of Pleistocene Genyornis eggshell

    NASA Astrophysics Data System (ADS)

    Kaufman, Darrell S.; Miller, Gifford H.

    1995-07-01

    This study explores the geochronological utility and analytical reproducibility of separating the high-molecular-weight fraction (HMW) from eggshells of the extinct late Pleistocene ratite, Genyornis, using disposable, prepacked gel-filtration columns. The superior integrity of ratite eggshell for the retention of amino acids indicates that this biomineral is better suited for this type of investigation than previously studied molluscan shell. To evaluate the reproducibility of the gel-filtration technique, we analyzed triplicate subsamples of three eggshells of different ages. The reproducibility, based on the average intrashell variation (coefficient of variation; CV) in the extent of isoleucine epimerization (aIle/Ile) in the HMW (enriched in molecules ca. >10,000 MW) is 3%, well within the range appropriate for geochronological purposes. The average intrashell variation in the total amino acid concentration (Σ[aa]) of the HMW is 5%, somewhat better than for the total acid hydrolysate (TOTAL) of the same samples (7%). To evaluate the relation between molecular weight and the rate of isoleucine epimerization, three molecular-weight fractions were separated using gel filtration, plus the naturally hydrolyzed free fraction (FREE), for each of four fossil eggshells. AIle/Ile increases with decreasing molecular weight in all shells, with a ca. sixfold to ninefold difference in ratios between the HMW andFREE, and a ca. fivefold difference between the HMW andTOTAL. Although linear correlations between aIle/Ile measured in each molecular-weight fraction and in theTOTAL are all highly significant (r ⩾ 0.951), the relation between the extent of epimerization in the HMW and in the TOTAL is best expressed as an exponential function (r = 0.951). This relation is consistent with the idea that, as the epimerization reaction approaches equilibrium in theTOTAL (ca. aIle/Ile > 1.1), its rate decreases beyond that of the HMW. The amino acid composition (relative percent of

  16. DETERMINATION OF CERTAIN AMINO ACIDS IN CHYMOTRYPSINOGEN, AND ITS MOLECULAR WEIGHT

    PubMed Central

    Brand, Erwin; Kassell, Beatrice

    1941-01-01

    1. A preparation of chymotrypsinogen, obtained from Dr. M. Kunitz, was analyzed for sulfur, the sulfur amino acids, tyrosine, and tryptophane. 2. The protein sulfur of chymotrypsinogen was accounted for as methionine, cysteine, and cystine. 3. A method is presented for calculating the minimum molecular weight of a protein from the distribution of the sulfur amino acids. In the case of chymotrypsinogen, the calculated minimum molecular weight was found to be the actual molecular weight. 4. The molecular weight of chymotrypsinogen is 36,700 by amino acid analysis as compared to 36,000 by osmotic pressure measurements of Kunitz and Northrop. Chymotrypsinogen contains per mol 17 atoms of sulfur, 3 residues of methionine, 4 of cysteine, 10 of half-cystine (i.e. 5 S—S linkages), 6 of tyrosine, and 10 of tryptophane. 5. The tryptophane content of chymotrypsinogen (5.51 per cent) is the highest of any protein so far on record. 6. Chymotrypsinogen contains no reactive SH groups, although it yields cysteine on hydrolysis. This may be due either to preformed but unreactive SH groups or to S—X groups. The term S—X group is used to denote the substitution of the sulfhydryl hydrogen by a constituent X; hydrolysis yields SH groups: S—X + HOH = SH + X—OH. PMID:19873262

  17. High-molecular-weight polymers for protein crystallization: poly-gamma-glutamic acid-based precipitants.

    PubMed

    Hu, Ting Chou; Korczyńska, Justyna; Smith, David K; Brzozowski, Andrzej Marek

    2008-09-01

    Protein crystallization has been revolutionized by the introduction of high-throughput technologies, which have led to a speeding up of the process while simultaneously reducing the amount of protein sample necessary. Nonetheless, the chemistry dimension of protein crystallization has remained relatively undeveloped. Most crystallization screens are based on the same set of precipitants. To address this shortcoming, the development of new protein precipitants based on poly-gamma-glutamic acid (PGA) polymers with different molecular-weight ranges is reported here: PGA-LM (low molecular weight) of approximately 400 kDa and PGA-HM (high molecular weight) of >1,000 kDa. It is also demonstrated that protein precipitants can be expanded further to polymers with much higher molecular weight than those that are currently in use. Furthermore, the modification of PGA-like polymers by covalent attachments of glucosamine substantially improved their solubility without affecting their crystallization properties. Some preliminary PGA-based screens are presented here.

  18. [Effects of low molecular weight organic acids on redox reactions of mercury].

    PubMed

    Zhao, Shi-Bo; Sun, Rong-Guo; Wang, Ding-Yong; Wang, Xiao-Wen; Zhang, Cheng

    2014-06-01

    To study the effects of the main component of vegetation root exudates-low molecular weight organic acids on the redox reactions of mercury, laboratory experiments were conducted to investigate the roles of tartaric, citric, and succinic acid in the redox reactions of mercury, and to analyze their interaction mechanism. The results indicated that tartaric acid significantly stimulated the mercury reduction reaction, while citric acid had inhibitory effect. Succinic acid improved the reduction rate at low concentration, and inhibited the reaction at high concentration. The mercury reduction rate by tartaric acid treatment was second-order with respect to Hg2+ concentration, ranging from 0.0014 L x (ng x min)(-1) to 0.005 6 L x (ng x min)(-1). All three organic acids showed a capacity for oxidating Hg(0) in the early stage, but the oxidized Hg(0) was subsequently reduced. The oxidation capacity of the three organic acids was in the order of citric acid > tartaric acid > succinic acid.

  19. Photochemical alkylation of inorganic selenium in the presence of low molecular weight organic acids.

    PubMed

    Guo, Xuming; Sturgeon, Ralph E; Mester, Zoltán; Gardner, Graeme J

    2003-12-15

    Using a flow-through photochemical reactor and a low pressure mercury lamp as a UV source, alkyl selenium species are formed from inorganic selenium(IV) in the presence of low molecular weight organic acids (LMW acids). The volatile alkyl Se species were cryogenically trapped and identified by GC-MS and GC-ICP-MS. In the presence of formic, acetic, propionic and malonic acids, inorganic selenium(IV) is converted by UV irradiation to volatile selenium hydride and carbonyl, dimethylselenide and diethylselenide, respectively. Se(IV) was successfully removed from contaminated agricultural drainage waters (California, U.S.A.) using a batch photoreactor system Se. Photochemical alkylation may thus offer a promising means of converting toxic selenium salts, present in contaminated water, to less toxic dimethylselenide. The LMW acids and photochemical alkylation process may also be key to understanding the source of atmospheric selenium and are likely involved in its mobility in the natural anaerobic environment.

  20. Fluorescence quenching of three molecular weight fractions of a soil fulvic acid by UO(2)(II).

    PubMed

    Shin, H S; Hong, K H; Lee, M H; Cho, Y H; Lee, C W

    2001-01-01

    A soil fulvic acid isolated from a Korean forest was divided into three different molecular weight fractions (F1: less than 220 Da; F2: 220-1000 Da; and F3: 1000-4000 Da) by gel filtration chromatography and the fractions were studied by synchronous fluorescence (SyF) spectroscopy. Analysis of the SyF spectra for the fulvic acid fractions showed that the fractions with molecules of larger sizes have a higher content of condensed aromatic compounds. The information about their interaction with UO(2)(II) ions in an aqueous solution (100 mg l(-1) of fulvic acid, in 0.1 M NaClO(4) at pH 3.5) was obtained from the measurement of SyF spectra at increasing concentrations of metal ions. Self-modeling mixture analysis of the quenching spectra gives two distinct peak components having a maximum peak position of 386 (type I) and 498 nm (type II) for all the size-fractionated fulvic acids. From the analysis of the quenching profiles of the peaks, using a non-linear method, the concentration of binding sites (C(L)), and the corresponding stability constants (logK) were calculated. The stability constants of the UO(2)(II)-fulvate complexes ranged from 4.10 to 5.33, and increased with higher molecular weight fractions, which indicates a stronger affinity for UO(2)(II) in the fraction with molecules of larger size.

  1. Characterization of low-molecular-weight hyaluronic acid-based hydrogel and differential stem cell responses in the hydrogel microenvironments.

    PubMed

    Kim, Jungju; Park, Yongdoo; Tae, Giyoong; Lee, Kyu Back; Hwang, Chang Mo; Hwang, Soon Jung; Kim, In Sook; Noh, Insup; Sun, Kyung

    2009-03-15

    Hyaluronic acid is a natural glycosaminoglycan involved in biological processes. Low-molecular-weight hyaluronic acid (10 and 50 kDa)-based hydrogel was synthesized using derivatized hyaluronic acid. Hyaluronic acid was acrylated by two steps: (1) introduction of an amine group using adipic acid dihydrazide, and (2) acrylation by N-acryloxysuccinimide. Injectable hyaluronic acid-based hydrogel was prepared by using acrylated hyaluronic acid and poly(ethylene glycol) tetra-thiols via Michael-type addition reaction. Mechanical properties of the hydrogel were evaluated by varying the molecular weight of acrylated hyaluronic acid (10 and 50 kDa) and the weight percent of hydrogel. Hydrogel based on 50-kDa hyaluronic acid showed the shortest gelation time and the highest complex modulus. Next, human mesenchymal stem cells were cultured in cell-adhesive RGD peptide-immobilized hydrogels together with bone morphogenic protein-2 (BMP-2). Cells cultured in the RGD/BMP-2-incorporated hydrogels showed proliferation rates higher than that of control or RGD-immobilized hydrogels. Real-time RT-PCR showed that the expression of osteoblast marker genes such as CBFalpha1 and alkaline phosphatase was increased in hyaluronic acid-based hydrogel, and the expression level was dependent on the molecular weight of hyaluronic acid, RGD peptide, and BMP-2. This study indicates that low-molecular-weight hyaluronic acid-based hydrogel can be applied to tissue regeneration as differentiation guidance materials of stem cells. PMID:18384163

  2. Characterization of fatty acid liposome coated with low-molecular-weight chitosan.

    PubMed

    Tan, Hsiao Wei; Misran, Misni

    2012-12-01

    Preparation of chitosan-coated fatty acid liposomes is often restricted by the solubility of chitosan under basic conditions. In this experiment, the preparation of chitosan-coated oleic acid (OA) liposomes using low molecular weight (LMW) chitosan (10 and 25 kDA) was demonstrated. These selected LMW chitosans are water soluble. The coating of the chitosan layer on OA liposomes was confirmed by its microscope images and physicochemical properties, such as zeta potential and the size of the liposomes. The "peeling off" effect on the surface of chitosan-coated OA liposomes was observed in the atomic force microscope images and showed the occurrence of the chitosan layer on the surface of OA liposomes. The size of the chitosan-coated liposomes was at least 20 nm smaller than the OA liposomes, and the increase of zeta potential with the increasing amount of LMW chitosan further confirmed the presence of the surface modification of OA liposomes.

  3. [Effect of wheat and faba bean intercropping on root exudation of low molecular weight organic acids].

    PubMed

    Xiao, Jing-Xiu; Zheng, Yi; Tang, Li

    2014-06-01

    Pot experiment of wheat and faba bean intercropping was conducted and exudates from wheat and faba bean roots were collected at different growth stages. Low molecular weight organic acids (OA) in root exudates were examined by HPLC. The results showed that wheat and faba bean intercropping significantly increased the total amounts of OA exuded by roots. At tillering (57 d), booting (120 d) and filling stages (142 d), intercropping increased the total amounts of OA in wheat root exudates by 155%, 35.6% and 92.6% respectively, in comparison with that of monoculture wheat (MW). At branching (57 d) and filling stages (142 d), intercropping increased the total amounts of OA in faba bean root exudates by 87.4% and 38.7%, respectively, in comparison with that of monoculture faba bean (MF). Wheat and faba bean intercropping changed the types of OA exuded by roots. At tillering stage, lactic acid was identified in root exudates of intercropping wheat (IW), but not in that of MW. At jointing stage (98 d), citric acid was identified in root exudates of IW, but not in that of MW, and acetic acid was vice versa. At branching stage, acetic acid was identified in root exudates of intercropping faba bean (IF), but not in that of MF, and lactic acid was vice versa. At filling stage, lactic acid was identified in root exudates of IF, but not in that of MF. Wheat and faba bean intercropping increased the OA exudation rate of wheat. At booting stage, the exudation rates of citric and fumaric acid from IW were 179 and 184-times as that of from MW, respectively. At filling stage, the exudation rate of lactic acid from IW was 2.53-times as that from MW. In conclusion, wheat and faba bean intercropping increased the rate and total amount, and changed the types of OA exuded by roots.

  4. Membrane disruption by antimicrobial fatty acids releases low-molecular-weight proteins from Staphylococcus aureus.

    PubMed

    Parsons, Joshua B; Yao, Jiangwei; Frank, Matthew W; Jackson, Pamela; Rock, Charles O

    2012-10-01

    The skin represents an important barrier for pathogens and is known to produce fatty acids that are toxic toward gram-positive bacteria. A screen of fatty acids as growth inhibitors of Staphylococcus aureus revealed structure-specific antibacterial activity. Fatty acids like oleate (18:1Δ9) were nontoxic, whereas palmitoleate (16:1Δ9) was a potent growth inhibitor. Cells treated with 16:1Δ9 exhibited rapid membrane depolarization, the disruption of all major branches of macromolecular synthesis, and the release of solutes and low-molecular-weight proteins into the medium. Other cytotoxic lipids, such as glycerol ethers, sphingosine, and acyl-amines blocked growth by the same mechanisms. Nontoxic 18:1Δ9 was used for phospholipid synthesis, whereas toxic 16:1Δ9 was not and required elongation to 18:1Δ11 prior to incorporation. However, blocking fatty acid metabolism using inhibitors to prevent acyl-acyl carrier protein formation or glycerol-phosphate acyltransferase activity did not increase the toxicity of 18:1Δ9, indicating that inefficient metabolism did not play a determinant role in fatty acid toxicity. Nontoxic 18:1Δ9 was as toxic as 16:1Δ9 in a strain lacking wall teichoic acids and led to growth arrest and enhanced release of intracellular contents. Thus, wall teichoic acids contribute to the structure-specific antimicrobial effects of unsaturated fatty acids. The ability of poorly metabolized 16:1 isomers to penetrate the cell wall defenses is a weakness that has been exploited by the innate immune system to combat S. aureus.

  5. [Adsorption of aflatoxin on montmorillonite modified by low-molecular-weight humic acids].

    PubMed

    Yao, Jia-Jia; Kang, Fu-Xing; Gao, Yan-Zheng

    2012-03-01

    The adsorption of a typical biogenic toxin aflatoxin B1 on montmorillonite modified by low-molecular-weight humic acids (M(r) < 3 500) was investigated. The montmorillonite rapidly adsorbed the aflatoxin B1 until amounting to the maximal capacity, and then the adsorbed aflatoxin B1 slowly released into solution and reached the sorption equilibrium state after 12 h. The sorption isotherm of aflatoxin B1 by montmorillonite could be well described by Langmiur model, while the sorption isotherm by humic acid-modified montmorillonite was well fitted by using the Freundlich model. The modification of the montmorillonite with humic acids obviously enhanced its adsorption capacity for aflatoxin B1, and the amounts of aflatoxin adsorbed by modified montmorillonite were obviously higher than those by montmorillonite. The sorption enhancement by humic acid modification was attributed to (1) the enlarged adsorption sites which owed to the surface collapse of crystal layers induced by organic acids, and (2) the binding of aflatoxin with the humic acid sorbed on mineral surface. In addition, the adsorption amounts of aflatoxin by montmorillonite and modified montmorillonite increased with the increase of pH values in solution, and more significant enhancement was observed for the latter than the former, which attributed to the release of humic acids from the modified montmorillonite with the high pH values in solution. This indicates that increasing the pH values resulted in the enhanced hydrophilic property and the release of the organic acids presented in modified montmorillonite, and more sorption sites were available for aflatoxin on the modified montmorillonite. Results of this work would strengthen our understanding of the behavior and fate of biological contaminants in the environment.

  6. Controlling Internal Organization of Multilayer Poly(methacrylic acid) Hydrogels with Polymer Molecular Weight

    DOE PAGES

    Kozlovskaya, Veronika; Zavgorodnya, Oleksandra; Ankner, John F.; Kharlampieva, Eugenia

    2015-11-16

    Here, we report on tailoring the internal architecture of multilayer-derived poly(methacrylic acid) (PMAA) hydrogels by controlling the molecular weight of poly(N-vinylpyrrolidone) (PVPON) in hydrogen-bonded (PMAA/PVPON) layer-by-layer precursor films. The hydrogels are produced by cross-linking PMAA in the spin-assisted multilayers followed by PVPON release. We found that the thickness, morphology, and architecture of hydrogen-bonded films and the corresponding hydrogels are significantly affected by PVPON chain length. For all systems, an increase in PVPON molecular weight from Mw = 2.5 to 1300 kDa resulted in increased total film thickness. We also show that increasing polymer Mw smooths the hydrogen-bonded film surfaces butmore » roughens those of the hydrogels. Using deuterated dPMAA marker layers in neutron reflectometry measurements, we found that hydrogen-bonded films reveal a high degree of stratification which is preserved in the cross-linked films. We observed dPMAA to be distributed more widely in the hydrogen-bonded films prepared with small Mw PVPON due to the greater mobility of short-chain PVPON. Furthermore, these variations in the distribution of PMAA are erased after cross-linking, resulting in a distribution of dPMAA over about two bilayers for all Mw but being somewhat more widely distributed in the films templated with higher Mw PVPON. Finally, our results yield new insights into controlling the organization of nanostructured polymer networks using polymer molecular weight and open opportunities for fabrication of thin films with well-organized architecture and controllable function.« less

  7. Controlling Internal Organization of Multilayer Poly(methacrylic acid) Hydrogels with Polymer Molecular Weight

    SciTech Connect

    Kozlovskaya, Veronika; Zavgorodnya, Oleksandra; Ankner, John F.; Kharlampieva, Eugenia

    2015-11-16

    Here, we report on tailoring the internal architecture of multilayer-derived poly(methacrylic acid) (PMAA) hydrogels by controlling the molecular weight of poly(N-vinylpyrrolidone) (PVPON) in hydrogen-bonded (PMAA/PVPON) layer-by-layer precursor films. The hydrogels are produced by cross-linking PMAA in the spin-assisted multilayers followed by PVPON release. We found that the thickness, morphology, and architecture of hydrogen-bonded films and the corresponding hydrogels are significantly affected by PVPON chain length. For all systems, an increase in PVPON molecular weight from Mw = 2.5 to 1300 kDa resulted in increased total film thickness. We also show that increasing polymer Mw smooths the hydrogen-bonded film surfaces but roughens those of the hydrogels. Using deuterated dPMAA marker layers in neutron reflectometry measurements, we found that hydrogen-bonded films reveal a high degree of stratification which is preserved in the cross-linked films. We observed dPMAA to be distributed more widely in the hydrogen-bonded films prepared with small Mw PVPON due to the greater mobility of short-chain PVPON. Furthermore, these variations in the distribution of PMAA are erased after cross-linking, resulting in a distribution of dPMAA over about two bilayers for all Mw but being somewhat more widely distributed in the films templated with higher Mw PVPON. Finally, our results yield new insights into controlling the organization of nanostructured polymer networks using polymer molecular weight and open opportunities for fabrication of thin films with well-organized architecture and controllable function.

  8. Vapor-pressure osmometric study of the molecular weight and aggregation tendency of a reference-soil fulvic acid

    USGS Publications Warehouse

    Marinsky, J.A.; Reddy, M.M.

    1990-01-01

    The molecular weight and aggregation tendency of a reference-soil fulvic acid in Armadale horizon Bh were determined by vapor-pressure osmometry using tetrahydrofuran and water as solvents. With tetrahydrofuran, number-average molecular weight values of 767 ?? 34 and 699 ?? 8 daltons were obtained from two separate sets of measurements. Two sets of measurements with water also yielded values within this range (754 ?? 70 daltons) provided that the fulvic acid concentration in water did not exceed 7 mg ml-1; at higher concentrations (9.1-13.7 mg ml-1) a number-average molecular weight of 956 ?? 25 daltons was resolved, providing evidence of molecular aggregation. Extension of these studies to 80% neutralized fulvic acid showed that a sizeable fraction of the sodium counter ion is not osmotically active.

  9. [Low-molecular-weight organic acids in precipitation in Zunyi City, Guizhou province].

    PubMed

    Jiang, Wei; Lee, Xin-qing; Zeng, Yong; Huang, Rong-sheng; Tan, Ling; Xu, Gang; Wang, Bing

    2008-09-01

    Formic (HCOOH) and acetic (CH3COOH) acids are ubiquitous in troposphere. Studies on the low-molecular carboxylic acids help shed light on the biogeochemical cycles of carbon, hydrogen and oxygen, as well as on the formation of acid precipitation. As a city with severe acid precipitation, the city Zunyi in north Guizhou province, provide a typical background for gaining insight into the organic geochemistry in the heavily polluted atmospheric environment. We collected the precipitation in the downtown city for a whole year on the event basis, and measured inorganic and organic anions with ion chromatograph and cations with atomic absorption spectroscopy. The data demonstrate an annual average pH of 4.11, a clear indication of the acid atmosphere. The volume-weighted mean concentrations of [HCOO-]T and [CH3COO-]T were 9.29 micromol x L(-1) (ranged from 0.15 micromol x L(-1) to 46.14 micromol x L(-1)) and 6.47 micromol x L(-1) (ranged from 0.02 micromol x L(-1) to 19.11 micromol x L(-1)) respectively, accounting for 4.10% of the total anions. With a coefficient of 0.86, formic is significantly correlated with acetic acid, suggesting that both acids share common sources. The acids often decrease with time in a precipitation event, with occasional increases in the middle and last stages, indicating that the organic acids are primarily scavenged from blow cloud, with limited amount from the long distance transportation. The close range provenance of organic acids is facilitated by the local environmental condition, which is characterized by the mountain-enclosed valley with high humidity, low wind speed, and high atmospheric dust content. Based on the Henry's Law, we proposed the ratio of formic and acetic acids in the precipitation (F/A)aq as the indicator of the sources, and thus found that the anthropogenic sources are responsible for the organic compounds in the Spring and Winter, while vegetation emissions claim the sources in the Summer and Autumn.

  10. [Effects of low molecular weight organic acids on speciation of exogenous Cu in an acid soil].

    PubMed

    Huang, Guo-Yong; Fu, Qing-Ling; Zhu, Jun; Wan, Tian-Ying; Hu, Hong-Qing

    2014-08-01

    In order to ascertain the effect of LMWOA (citric acid, tartaric acid, oxalic acid) on Cu-contaminated soils and to investigate the change of Cu species, a red soil derived from quartz sandstone deposit was added by Cu (copper) in the form of CuSO4 x 5H2O so as to simulate soil Cu pollution, keeping the additional Cu concentrations were 0, 100, 200, 400 mg x kg(-1) respectively. After 9 months, different LMWOA was also added into the simulated soil, keeping the additional LMWOAs in soil were 0, 5, 10, 20 mmol x kg(-1) respectively. After 2 weeks incubation, the modified sequential extraction method on BCR (European Communities Bureau of Reference) was used to evaluate the effects of these LMWOAs on the changes of copper forms in soil. The result showed that the percentage of weak acid dissolved Cu, the most effective form in the soil increased with three organic acids increase in quantity in the simulated polluted soil. And there was a good activation effect on Cu in the soil when organic acid added. Activation effects on Cu increased with concentration of citric acid increasing, but it showed a rise trend before they are basically remained unchanged in the case of tartaric acid and oxalic acid added in the soil. On the contrary, the state of the reduction of copper which was regarded as a complement for effective state decreased with the increased concentration of organic acid in the soil, especially with citric acid. When 20 mmol x kg(-1) oxalic acid and citric acid were added into the soil, the activation effect was the best; whereas for tartaric, the concentration was 10 mmol x kg(-1). In general, the effect on the changes of Cu forms in the soil is citric acid > tartaric acid > oxalic acid.

  11. Factors that affect molecular weight distribution of Suwannee river fulvic acid as determined by electrospray ionization/mass spectrometry

    USGS Publications Warehouse

    Rostad, C.E.; Leenheer, J.A.

    2004-01-01

    Effects of methylation, molar response, multiple charging, solvents, and positive and negative ionization on molecular weight distributions of aquatic fulvic acid were investigated by electrospray ionization/mass spectrometry. After preliminary analysis by positive and negative modes, samples and mixtures of standards were derivatized by methylation to minimize ionization sites and reanalyzed.Positive ionization was less effective and produced more complex spectra than negative ionization. Ionization in methanol/water produced greater response than in acetonitrile/water. Molar response varied widely for the selected free acid standards when analyzed individually and in a mixture, but after methylation this range decreased. After methylation, the number average molecular weight of the Suwannee River fulvic acid remained the same while the weight average molecular weight decreased. These differences are probably indicative of disaggregation of large aggregated ions during methylation. Since the weight average molecular weight decreased, it is likely that aggregate formation in the fulvic acid was present prior to derivatization, rather than multiple charging in the mass spectra. ?? 2004 Elsevier B.V. All rights reserved.

  12. Interactions of nano-oxides with low-molecular-weight organic acids in a contaminated soil.

    PubMed

    Vítková, Martina; Komárek, Michael; Tejnecký, Václav; Šillerová, Hana

    2015-08-15

    Various low-molecular-weight organic acids (LMWOAs) play an important role in the mobilisation of contaminants and their subsequent uptake by plants. Nano-maghemite (NM) and an amorphous Mn oxide (AMO) were investigated for their stabilisation potential under simulated rhizosphere conditions in terms of their use during chemical stabilisation and aided phytostabilisation of metal(loid)s in contaminated soils. In order to understand the reactivity of these potential sorbents of contaminants in soils and subsequent mobility of metal(loid)s, a set of time-dependent batch leaching experiments was performed using a mix of acetic, lactic, citric, malic and formic acids simulating root exudates. Despite being relatively unstable under given conditions, the AMO proved to be an efficient amendment for rapid stabilisation of both metals and As compared to NM. Generally, low pH (∼ 4) and the presence of citrate complexes resulted in higher mobility of metals in the non- and NM-amended soil. In contrast, the presence of AMO in the soil accelerated the neutralisation reactions related to pH increase and (co-) precipitation of secondary Fe/Mn/Al oxyhydroxides. Mineralogical transformations of the AMO showed to be crucial for contaminant immobilisation. PMID:25814334

  13. Marsh plant response to metals: Exudation of aliphatic low molecular weight organic acids (ALMWOAs)

    NASA Astrophysics Data System (ADS)

    Rocha, A. Cristina S.; Almeida, C. Marisa R.; Basto, M. Clara P.; Vasconcelos, M. Teresa S. D.

    2016-03-01

    Metal exposure is known to induce the production and secretion of substances, such as aliphatic low molecular weight organic acids (ALMWOAs), into the rhizosphere by plant roots. Knowledge on this matter is extensive for soil plants but still considerably scarce regarding marsh plants roots adapted to high salinity media. Phragmites australis and Halimione portulacoides, two marsh plants commonly distributed in European estuarine salt marshes, were used to assess the response of roots of both species, in terms of ALMWOAs exudation, to Cu, Ni and Cd exposure (isolated and in mixture since in natural environment, they are exposed to mixture of metals). As previous studies were carried out in unrealistic and synthetic media, here a more natural medium was selected. Therefore, in vitro experiments were carried out, with specimens of both marsh plants, and in freshwater contaminated with two different Cu, Ni and Cd concentrations (individual metal and in mixture). Both marsh plants were capable of liberating ALMWOAs into the surrounding medium. Oxalic, citric and maleic acids were found in P. australis root exudate solutions and oxalic and maleic acids in H. portulacoides root exudate solutions. ALMWOA liberation by both plants was plant species and metal-dependent. For instance, Cu affected the exudation of oxalic acid by H. portulacoides and of oxalic and citric acids by P. australis roots. In contrast, Ni and Cd did not stimulate any specific response. Regarding the combination of all metals, H. portulacoides showed a similar response to that observed for Cu individually. However, in the P. australis case, at high metal concentration mixture, a synergetic effect led to the increase of oxalic acid levels in root exudate solution and to a decrease of citric acid liberation. A correlation between ALMWOAs exudation and metal accumulation could not be established. P. australis and H. portulacoides are considered suitable metal phytoremediators of estuarine impacted areas

  14. Relationship of amino acid composition and molecular weight of antifreeze glycopeptides to non-colligative freezing point depression.

    PubMed

    Schrag, J D; O'Grady, S M; DeVries, A L

    1982-08-01

    Many polar fishes synthesize a group of eight glycopeptides that exhibit a non-colligative lowering of the freezing point of water. These glycopeptides range in molecular weight between 2600 and 33 700. The largest glycopeptides [1-5] lower the freezing point more than the small ones on a weight basis and contain only two amino acids, alanine and threonine, with the disaccharide galactose-N-acetyl-galactosamine attached to threonine. The small glycopeptides, 6, 7, and 8, also lower the freezing point and contain proline, which periodically substitutes for alanine. Glycopeptides with similar antifreeze properties isolated from the saffron cod and the Atlantic tomcod contain an additional amino acid, arginine, which substitutes for threonine in glycopeptide 6. In this study we address the question of whether differences in amino acid composition or molecular weight between large and small glycopeptides are responsible for the reduced freezing point depressing capability of the low molecular weight glycopeptides. The results indicate that the degree of amino acid substitutions that occur in glycopeptides 6-8 do not have a significant effect on the unusual freezing point lowering and that the observed decrease in freezing point depression with smaller glycopeptides can be accounted for on the basis of molecular weight.

  15. Phenylalanine-containing cyclic dipeptides--the lowest molecular weight hydrogelators based on unmodified proteinogenic amino acids.

    PubMed

    Kleinsmann, Alexander J; Nachtsheim, Boris J

    2013-09-14

    Cyclic dipeptides (diketopiperazines - DKPs) that are based on the proteinogenic amino acid phenylalanine in combination with serine, cysteine, glutamate, histidine and lysine are described as simple and remarkable low molecular weight hydrogelators. Blends of selected DKPs show remarkable pH-dependent properties and can be applied as easy to tune materials in drug delivery.

  16. Effect of CMC Molecular Weight on Acid-Induced Gelation of Heated WPI-CMC Soluble Complex.

    PubMed

    Huan, Yan; Zhang, Sha; Vardhanabhuti, Bongkosh

    2016-02-01

    Acid-induced gelation properties of heated whey protein isolate (WPI) and carboxymethylcellulose (CMC) soluble complex were investigated as a function of CMC molecular weight (270, 680, and 750 kDa) and concentrations (0% to 0.125%). Heated WPI-CMC soluble complex with 6% protein was made by heating biopolymers together at pH 7.0 and 85 °C for 30 min and diluted to 5% protein before acid-induced gelation. Acid-induced gel formed from heated WPI-CMC complexes exhibited increased hardness and decreased water holding capacity with increasing CMC concentrations but gel strength decreased at higher CMC content. The highest gel strength was observed with CMC 750 k at 0.05%. Gels with low CMC concentration showed homogenous microstructure which was independent of CMC molecular weight, while increasing CMC concentration led to microphase separation with higher CMC molecular weight showing more extensive phase separation. When heated WPI-CMC complexes were prepared at 9% protein the acid gels showed improved gel hardness and water holding capacity, which was supported by the more interconnected protein network with less porosity when compared to complexes heated at 6% protein. It is concluded that protein concentration and biopolymer ratio during complex formation are the major factors affecting gel properties while the effect of CMC molecular weight was less significant.

  17. [Influence of Three Low-Molecular-Weight Organic Acids on the Adsorption of Phenanthrene in Purple Soil].

    PubMed

    Xie, Li; Chen, Ben-shou; Zhang, Jin-zhong; Lu, Song; Jiang, Tao

    2016-03-15

    The effects of three low-molecular-weight organic acids (citric acid, malic acid and oxalic acid) on the adsorption of phenanthrene in purple soil were studied by static adsorption experiment. The results showed that the adsorption kinetic process of phenanthrene in purple soil could be described by the second-order kinetic model, and the adsorption rate constant would significantly decrease in the presence of the three low-molecular-weight organic acids ( LMWOAs). The adsorption thermodynamic process could be well described by linear adsorption model, which was dominated by distribution role. The three LMWOAs could promote the adsorption of phenantherene in purple soil when their concentrations were less than 5 mmol · L⁻¹, whereas inhibit the adsorption when their concentrations were more than 10 mmol · L⁻¹, and the inhibition would increase with increasing concentrations. Moreover, the inhibitory ability displayed a decreasing order of citric acid, oxalic acid, and malic acid when their concentrations were 20 mmol · L⁻¹, which is related to the molecular structure and acidity of the three LMWOAs. Compared with the control, the content of dissolved organic matter (DOM) released from purple soil showed a trend of first decrease and then increase with increasing LMWOAs concentration, and the adsorption capacity of phenanthrene in purple soil was negatively related to DOM content. PMID:27337897

  18. [Influence of Three Low-Molecular-Weight Organic Acids on the Adsorption of Phenanthrene in Purple Soil].

    PubMed

    Xie, Li; Chen, Ben-shou; Zhang, Jin-zhong; Lu, Song; Jiang, Tao

    2016-03-15

    The effects of three low-molecular-weight organic acids (citric acid, malic acid and oxalic acid) on the adsorption of phenanthrene in purple soil were studied by static adsorption experiment. The results showed that the adsorption kinetic process of phenanthrene in purple soil could be described by the second-order kinetic model, and the adsorption rate constant would significantly decrease in the presence of the three low-molecular-weight organic acids ( LMWOAs). The adsorption thermodynamic process could be well described by linear adsorption model, which was dominated by distribution role. The three LMWOAs could promote the adsorption of phenantherene in purple soil when their concentrations were less than 5 mmol · L⁻¹, whereas inhibit the adsorption when their concentrations were more than 10 mmol · L⁻¹, and the inhibition would increase with increasing concentrations. Moreover, the inhibitory ability displayed a decreasing order of citric acid, oxalic acid, and malic acid when their concentrations were 20 mmol · L⁻¹, which is related to the molecular structure and acidity of the three LMWOAs. Compared with the control, the content of dissolved organic matter (DOM) released from purple soil showed a trend of first decrease and then increase with increasing LMWOAs concentration, and the adsorption capacity of phenanthrene in purple soil was negatively related to DOM content.

  19. In situ injection of phenylboronic acid based low molecular weight gels for efficient chemotherapy.

    PubMed

    Gao, Wenxia; Liang, Yan; Peng, Xinyu; Hu, Yalong; Zhang, Longgui; Wu, Huayue; He, Bin

    2016-10-01

    Injectable low molecular weight gels (LMWGs) based on the derivatives of phenylboronic acid were prepared and used as substrates for efficient in situ chemotherapy. The gelators as well as LMWGs were characterized by (1)H NMR, UV-vis, FTIR, MS and SEM. Anticancer drug doxorubicin hydrochloride (DOX) was encapsulated in the gels. The rheological properties and rapid recovery capability of both blank and drug-loaded gels were tested. The LMWGs were non-toxic to both 3T3 fibroblasts and 4T1 breast cancer cells. The gels were formed rapidly after injected in vivo. The in vivo anticancer activities of DOX-loaded LMWGs were investigated in breast cancer bearing mice. The intratumoral injection of DOX loaded LMWGs with dose of 30 mg/kg revealed that the gels could coat around the tumor tissues to release DOX sustainingly and maintain effective DOX concentration for chemotherapy. The systemic toxicity of DOX was reduced significantly with the in situ administration of LMWGs formulations. The injectable LMWGs exhibited excellent therapeutic efficacy and low side effects in local chemotherapy. PMID:27497056

  20. Ancient low-molecular-weight organic acids in permafrost fuel rapid carbon dioxide production upon thaw.

    PubMed

    Drake, Travis W; Wickland, Kimberly P; Spencer, Robert G M; McKnight, Diane M; Striegl, Robert G

    2015-11-10

    Northern permafrost soils store a vast reservoir of carbon, nearly twice that of the present atmosphere. Current and projected climate warming threatens widespread thaw of these frozen, organic carbon (OC)-rich soils. Upon thaw, mobilized permafrost OC in dissolved and particulate forms can enter streams and rivers, which are important processors of OC and conduits for carbon dioxide (CO2) to the atmosphere. Here, we demonstrate that ancient dissolved organic carbon (DOC) leached from 35,800 y B.P. permafrost soils is rapidly mineralized to CO2. During 200-h experiments in a novel high-temporal-resolution bioreactor, DOC concentration decreased by an average of 53%, fueling a more than sevenfold increase in dissolved inorganic carbon (DIC) concentration. Eighty-seven percent of the DOC loss to microbial uptake was derived from the low-molecular-weight (LMW) organic acids acetate and butyrate. To our knowledge, our study is the first to directly quantify high CO2 production rates from permafrost-derived LMW DOC mineralization. The observed DOC loss rates are among the highest reported for permafrost carbon and demonstrate the potential importance of LMW DOC in driving the rapid metabolism of Pleistocene-age permafrost carbon upon thaw and the outgassing of CO2 to the atmosphere by soils and nearby inland waters. PMID:26504243

  1. Ancient low-molecular-weight organic acids in permafrost fuel rapid carbon dioxide production upon thaw.

    PubMed

    Drake, Travis W; Wickland, Kimberly P; Spencer, Robert G M; McKnight, Diane M; Striegl, Robert G

    2015-11-10

    Northern permafrost soils store a vast reservoir of carbon, nearly twice that of the present atmosphere. Current and projected climate warming threatens widespread thaw of these frozen, organic carbon (OC)-rich soils. Upon thaw, mobilized permafrost OC in dissolved and particulate forms can enter streams and rivers, which are important processors of OC and conduits for carbon dioxide (CO2) to the atmosphere. Here, we demonstrate that ancient dissolved organic carbon (DOC) leached from 35,800 y B.P. permafrost soils is rapidly mineralized to CO2. During 200-h experiments in a novel high-temporal-resolution bioreactor, DOC concentration decreased by an average of 53%, fueling a more than sevenfold increase in dissolved inorganic carbon (DIC) concentration. Eighty-seven percent of the DOC loss to microbial uptake was derived from the low-molecular-weight (LMW) organic acids acetate and butyrate. To our knowledge, our study is the first to directly quantify high CO2 production rates from permafrost-derived LMW DOC mineralization. The observed DOC loss rates are among the highest reported for permafrost carbon and demonstrate the potential importance of LMW DOC in driving the rapid metabolism of Pleistocene-age permafrost carbon upon thaw and the outgassing of CO2 to the atmosphere by soils and nearby inland waters.

  2. Ancient low–molecular-weight organic acids in permafrost fuel rapid carbon dioxide production upon thaw

    PubMed Central

    Drake, Travis W.; Wickland, Kimberly P.; Spencer, Robert G. M.; McKnight, Diane M.; Striegl, Robert G.

    2015-01-01

    Northern permafrost soils store a vast reservoir of carbon, nearly twice that of the present atmosphere. Current and projected climate warming threatens widespread thaw of these frozen, organic carbon (OC)-rich soils. Upon thaw, mobilized permafrost OC in dissolved and particulate forms can enter streams and rivers, which are important processors of OC and conduits for carbon dioxide (CO2) to the atmosphere. Here, we demonstrate that ancient dissolved organic carbon (DOC) leached from 35,800 y B.P. permafrost soils is rapidly mineralized to CO2. During 200-h experiments in a novel high–temporal-resolution bioreactor, DOC concentration decreased by an average of 53%, fueling a more than sevenfold increase in dissolved inorganic carbon (DIC) concentration. Eighty-seven percent of the DOC loss to microbial uptake was derived from the low–molecular-weight (LMW) organic acids acetate and butyrate. To our knowledge, our study is the first to directly quantify high CO2 production rates from permafrost-derived LMW DOC mineralization. The observed DOC loss rates are among the highest reported for permafrost carbon and demonstrate the potential importance of LMW DOC in driving the rapid metabolism of Pleistocene-age permafrost carbon upon thaw and the outgassing of CO2 to the atmosphere by soils and nearby inland waters. PMID:26504243

  3. Effect of preparation parameters on ultra low molecular weight chitosan/hyaluronic acid nanoparticles.

    PubMed

    Nazeri, Niloofar; Avadi, Mohammad Reza; Faramarzi, Mohammad Ali; Safarian, Shahrokh; Tavoosidana, Gholamreza; Khoshayand, Mohammad Reza; Amani, Amir

    2013-11-01

    Nanoparticles of ultra low molecular weight chitosan (ULMWCS)/hyaluronic acid (HA) were prepared by ion gelation. Three independent variables, namely, ratio of concentration of ULMWCS to HA (CS/HA), pH of solution and stirring time were studied to identify their effects on size, polydispersity and zeta potential of prepared nanoparticles using a Box-Behnken design. Results showed that pH and CS/HA have a direct effect on size, while increase of stirring time decreases the size of nanoparticles. Additionally, it was shown that all the independent parameters have direct effects on zeta potential. Also, the minimum polydispersity index was observed at lowest values of CS/HA. The model also predicted that the optimum values are 4.15, 4.14 and 180 (min) for the CS/HA, solution pH and stirring time, respectively. The obtained preparation had a size of 200 nm, polydispersity index of 0.37, and zeta potential of 13.0 mV.

  4. Branched chain amino acids maintain the molecular weight of poly(γ-glutamic acid) of Bacillus licheniformis ATCC 9945 during the fermentation.

    PubMed

    Mitsunaga, Hitoshi; Meissner, Lena; Büchs, Jochen; Fukusaki, Eiichiro

    2016-10-01

    Poly(γ-glutamic acid) mainly produced by Bacillus spp. is an industrially important compound due to several useful features. Among them, molecular weight is an important characteristic affecting on the physical properties such as viscosities and negative charge densities. However, it is difficult to control the molecular size of PGA since it decreases during fermentation. Previous study reported that PGA produced in the media containing different carbon sources such as glucose and glycerol showed differences in molecular weight. Therefore in this study, the effect of carbon source on the PGA molecular weight was examined; with the aim of developing a strategy to maintain the high molecular weight of PGA during fermentation. Our result showed that the weight average molecular weight (Mw) of PGA of Bacillus licheniformis ATCC 9945 cultivated in the media containing PTS-sugars were higher than the medium containing glycerol (non-PTS). The result of metabolome analysis indicated the possibility of CodY (a global regulator protein) activation in the cells cultivated in the media containing PTS-sugars. To mimic this effect, branched-chain amino acids (BCAAs), which are activators of CodY, were added to a medium containing glycerol. As the result, the Mw of PGA in the BCAAs-supplemented media were maintained and high during the early production phase compared to the non BCAAs-supplemented medium. These results indicate that BCAAs can repress the PGA molecular weight reduction during fermentation in B. licheniformis ATCC 9945.

  5. High molecular weight hyaluronic acid limits astrocyte activation and scar formation after spinal cord injury

    NASA Astrophysics Data System (ADS)

    Khaing, Zin Z.; Milman, Brian D.; Vanscoy, Jennifer E.; Seidlits, Stephanie K.; Grill, Raymond J.; Schmidt, Christine E.

    2011-08-01

    A major hurdle for regeneration after spinal cord injury (SCI) is the ability of axons to penetrate and grow through the scar tissue. After SCI, inflammatory cells, astrocytes and meningeal cells all play a role in developing the glial scar. In addition, degradation of native high molecular weight (MW) hyaluronic acid (HA), a component of the extracellular matrix, has been shown to induce activation and proliferation of astrocytes. However, it is not known if the degradation of native HA actually enhances glial scar formation. We hypothesize that the presence of high MW HA (HA with limited degradation) after SCI will decrease glial scarring. Here, we demonstrate that high MW HA decreases cell proliferation and reduces chondroitin sulfate proteoglycan (CSPG) production in cultured neonatal and adult astrocytes. In addition, stiffness-matched high MW HA hydrogels crosslinked to resist degradation were implanted in a rat model of spinal dorsal hemisection injury. The numbers of immune cells (macrophages and microglia) detected at the lesion site in animals with HA hydrogel implants were significantly reduced at acute time points (one, three and ten days post-injury). Lesioned animals with HA implants also exhibited significantly lower CSPG expression at ten days post-injury. At nine weeks post-injury, animals with HA hydrogel implants exhibited a significantly decreased astrocytic response, but did not have significantly altered CSPG expression. Combined, these data suggest that high MW HA, when stabilized against degradation, mitigates astrocyte activation in vitro and in vivo. The presence of HA implants was also associated with a significant decrease in CSPG deposition at ten days after SCI. Therefore, HA-based hydrogel systems hold great potential for minimizing undesired scarring as part of future repair strategies after SCI.

  6. High molecular weight hyaluronic acid limits astrocyte activation and scar formation after spinal cord injury.

    PubMed

    Khaing, Zin Z; Milman, Brian D; Vanscoy, Jennifer E; Seidlits, Stephanie K; Grill, Raymond J; Schmidt, Christine E

    2011-08-01

    A major hurdle for regeneration after spinal cord injury (SCI) is the ability of axons to penetrate and grow through the scar tissue. After SCI, inflammatory cells, astrocytes and meningeal cells all play a role in developing the glial scar. In addition, degradation of native high molecular weight (MW) hyaluronic acid (HA), a component of the extracellular matrix, has been shown to induce activation and proliferation of astrocytes. However, it is not known if the degradation of native HA actually enhances glial scar formation. We hypothesize that the presence of high MW HA (HA with limited degradation) after SCI will decrease glial scarring. Here, we demonstrate that high MW HA decreases cell proliferation and reduces chondroitin sulfate proteoglycan (CSPG) production in cultured neonatal and adult astrocytes. In addition, stiffness-matched high MW HA hydrogels crosslinked to resist degradation were implanted in a rat model of spinal dorsal hemisection injury. The numbers of immune cells (macrophages and microglia) detected at the lesion site in animals with HA hydrogel implants were significantly reduced at acute time points (one, three and ten days post-injury). Lesioned animals with HA implants also exhibited significantly lower CSPG expression at ten days post-injury. At nine weeks post-injury, animals with HA hydrogel implants exhibited a significantly decreased astrocytic response, but did not have significantly altered CSPG expression. Combined, these data suggest that high MW HA, when stabilized against degradation, mitigates astrocyte activation in vitro and in vivo. The presence of HA implants was also associated with a significant decrease in CSPG deposition at ten days after SCI. Therefore, HA-based hydrogel systems hold great potential for minimizing undesired scarring as part of future repair strategies after SCI.

  7. High molecular weight hyaluronic acid limits astrocyte activation and scar formation after spinal cord injury.

    PubMed

    Khaing, Zin Z; Milman, Brian D; Vanscoy, Jennifer E; Seidlits, Stephanie K; Grill, Raymond J; Schmidt, Christine E

    2011-08-01

    A major hurdle for regeneration after spinal cord injury (SCI) is the ability of axons to penetrate and grow through the scar tissue. After SCI, inflammatory cells, astrocytes and meningeal cells all play a role in developing the glial scar. In addition, degradation of native high molecular weight (MW) hyaluronic acid (HA), a component of the extracellular matrix, has been shown to induce activation and proliferation of astrocytes. However, it is not known if the degradation of native HA actually enhances glial scar formation. We hypothesize that the presence of high MW HA (HA with limited degradation) after SCI will decrease glial scarring. Here, we demonstrate that high MW HA decreases cell proliferation and reduces chondroitin sulfate proteoglycan (CSPG) production in cultured neonatal and adult astrocytes. In addition, stiffness-matched high MW HA hydrogels crosslinked to resist degradation were implanted in a rat model of spinal dorsal hemisection injury. The numbers of immune cells (macrophages and microglia) detected at the lesion site in animals with HA hydrogel implants were significantly reduced at acute time points (one, three and ten days post-injury). Lesioned animals with HA implants also exhibited significantly lower CSPG expression at ten days post-injury. At nine weeks post-injury, animals with HA hydrogel implants exhibited a significantly decreased astrocytic response, but did not have significantly altered CSPG expression. Combined, these data suggest that high MW HA, when stabilized against degradation, mitigates astrocyte activation in vitro and in vivo. The presence of HA implants was also associated with a significant decrease in CSPG deposition at ten days after SCI. Therefore, HA-based hydrogel systems hold great potential for minimizing undesired scarring as part of future repair strategies after SCI. PMID:21753237

  8. [Low molecular weight carboxylic acids in precipitation during the rainy season in the rural area of Anshun, West Guizhou Province].

    PubMed

    Zhang, Yan-Lin; Lee, Xin-Qing; Huang, Dai-Kuan; Huang, Rong-Sheng; Jiang, Wei

    2009-03-15

    40 rainwater samples were collected at Anshun from June 2007 to October 2007 and analysed in terms of pH values, electrical conductivity, major inorganic anions and soluble low molecular weight carboxylic acids. The results showed that pH of individual precipitation events ranged from 3.57-7.09 and the volume weight mean pH value was 4.57. The most abundant carboxylic acids were acetic (volume weight mean concentration 6.75 micromol x L(-1)) and formic (4.61 micromol x L(-1)) followed by oxalic (2.05 micromol x L(-1)). The concentration levels for these three species during summer especially June and July were comparatively high; it implied that organic acids in Anshun may came primarily from emissions from growing vegetations or products of the photochemical reactions of unsaturated hydrocarbons. Carboxylic acids were estimated to account for 32.2% to the free acidity in precipitation. The contribution was higher than in Guiyang rainwater, which indicated contamination by industry in Guiyang was more than in Anshun. The remarkable correlation(p = 0.01) between formic acid and acetic acid suggest that they have similar sources or similar intensity but different sources. And the remarkable correlation (p = 0.01) between and formic acid and oxalic acid showed that the precursors of oxalic acid and formic acid had similar sources. During this period, the overall wet deposition of carboxylic acids were 2.10 mmol/m2. And it appeared mainly in the summer, during which both concentration and contribution to free acidity were also relatively high. Consequently, it was necessary to control emission of organic acids in the summer to reduce frequence of acid rain in Anshun.

  9. The geochemical evolution of low-molecular-weight organic acids derived from the degradation of petroleum contaminants in groundwater

    USGS Publications Warehouse

    Cozzarelli, I.M.; Baedecker, M.J.; Eganhouse, R.P.; Goerlitz, D.F.

    1994-01-01

    The geochemical evolution of low-molecular-weight organic acids in groundwater downgradient from a crude-oil spill near Bemidji, Minnesota, was studied over a five year period (1986-1990). The organic acids are metabolic intermediates of the degradation of components of the crude oil and are structurally related to hydrocarbon precursors. The concentrations of organic acids, particularly aliphatic acids, increase as the microbial alteration of hydrocarbons progresses. The organic-acid pool changes in composition and concentration over time and in space as the degradation processes shift from Fe(III) reduction to methanogenesis. Over time, the aquifer system evolves into one in which the groundwater contains more oxidized products of hydrocarbon degradation and the reduced forms of iron, manganese, and nitrogen. Laboratory microcosm experiments with aquifer material support the hypothesis that organic acids observed in the groundwater originate from the microbial degradation of aromatic hydrocarbons under anoxic conditions. The geochemistry of two other shallow aquifers in coastal plain sediments, one contaminated with creosote waste and the other with gasoline, were compared to the Bemidji site. The geochemical evolution of the low-molecular-weight organic acid pool in these systems is controlled, in part, by the presence of electron acceptors available for microbially mediated electron-transfer reactions. The depletion of electron acceptors in aquifers leads to the accumulation of aliphatic organic acids in anoxic groundwater. ?? 1994.

  10. Inhibitory Effects of Medium Molecular Weight Heparinyl Amino Acid Derivatives on Ischemic Paw Edema in Mice.

    PubMed

    Takeda, Seiichi; Toda, Takao; Nakamura, Kazuki

    2016-01-01

    We investigated the radical-scavenging effects of heparin (HE), medium molecular weight heparinyl phenylalanine (MHF), and medium molecular weight heparinyl leucine (MHL) using ischemic paw edema in mice. We also examined the activated partial thromboplastin time (APTT) of mice that were administered these compounds as an index of their side-effects. HE had a preventative effect and significant reduced ischemic paw edema. However, its effect was not dose-dependent and the dose-response curve was bell-shaped. The effective dose of HE also exhibited a prolonged APTT. Pretreatment using MHF and MHL were effective against ischemic paw edema without a prolonged APTT. Remarkably, the action of MHF was not only preventively, but also therapeutically active. These results suggest that MHF and MHL are superior to HE as safe radical scavengers in vivo. PMID:27381605

  11. Formation and catalytic activity of high molecular weight soluble polymers produced by heating amino acids in a modified sea medium

    NASA Astrophysics Data System (ADS)

    Okihana, Hiroyuki

    1982-06-01

    Eighteen protein amino acids with milk casein composition were heated in a modified sea medium. Marigranules were formed in the precipitates and soluble polymers were formed in the supernatant. Time course of the reaction (ultraviolet spectra, the concentration of metal ions, and the concentration of amino acids in the supernatant) were measured. The time course of the formation of the soluble polymers was also studied by Bio-Gel P-2 column. High molecular weight soluble polymers (HMWSP) were separated from low molecular weight ones by dialysis. It was shown that these polymers catalyzed the dehydrogenation of NADH. These polymers also catalyzed the coupled reaction between dehydrogenation of NADH and reduction of resazurin. This coupled reaction was accelerated by the light.

  12. Effect of low molecular weight organic acids on phosphorus adsorption by ferric-alum water treatment residuals.

    PubMed

    Wang, Changhui; Wang, Ziyuan; Lin, Lu; Tian, Binghui; Pei, Yuansheng

    2012-02-15

    Effects of low molecular weight organic acids (LMWOAs; citric acid, oxalic acid and tartaric acid) on phosphorus (P) adsorption by ferric-alum water treatment residuals (FARs) were studied. Both batch and column experiments indicated that the effects of LMWOAs on P adsorption were closely related to adsorption time. Initially, all acids presented inhibitory function on P adsorption. The inhibition became weaker with time, eventually promoting P adsorption for citric acid and tartaric acid. In the column experiment with a 61-day duration, high P adsorption rates (>55%) were observed for the test groups containing citric acid and tartaric acid. Interestingly, higher pH likely enhanced P adsorption with the effects of LMWOAs and a distinct relationship between LMWOAs' effects on P adsorption and their concentrations was not observed. Moreover, fractionation of the adsorbed P from the FARs demonstrated that oxalic acid reduced P adsorption capacity, while citric acid and tartaric acid increased. Based on the forms of Fe and Al existing in the FARs and Fourier transform infrared spectroscopy analyses, LMWOAs can promote P adsorption through activating crystalline Fe/Al and preventing crystallization of amorphous Fe/Al to increase P adsorption sites, and can also inhibit P adsorption by competition with adsorption sites.

  13. Molecular weight determination of hyaluronic acid by gel filtration chromatography coupled to matrix-assisted laser desorption ionization mass spectrometry.

    PubMed

    Yeung, B; Marecak, D

    1999-08-13

    An analytical approach has been described for the molecular weight characterization of enzymatically degraded hyaluronic acid (HA). The approach involved the combined use of aqueous gel filtration chromatography (GFC) with matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). Microfractions were collected across an eluting peak from the chromatography system, followed by mass spectrometric analysis of these narrow fractions. The molecular mass determined by MALDI-MS and the signal obtained from the chromatography established a calibration curve for other hyaluronic acid samples analyzed by this GFC system. Results of one HA sample were obtained from both the calibration curve and direct fraction-by-fraction MALDI-MS analysis, and comparison of these results showed reasonable agreement. In contrast, molecular weights resulted from external calibration using dextran and pullullan standards showed drastically different numbers. Therefore, the GFC-MALDI-MS approach is a reliable method for the molecular weight characterization of polydisperse polysaccharides for which suitable calibration standards are unavailable for conventional GFC analysis. PMID:10481993

  14. Microbial production of low molecular weight hyaluronic acid by adding hydrogen peroxide and ascorbate in batch culture of Streptococcus zooepidemicus.

    PubMed

    Liu, Long; Du, Guocheng; Chen, Jian; Zhu, Yang; Wang, Miao; Sun, Jun

    2009-01-01

    Microbial production of low molecular weight hyaluronic acid (HA) by the addition of hydrogen peroxide and ascorbate during the batch culture of Streptococcus zooepidemicus was investigated. Hydrogen peroxide (1.0 mmol/g HA) and ascorbate (0.5 mmol/g HA) were added at 8h and 12h to degrade HA. With the redox depolymerization of HA, the HA molecular weight decreased from 1,300 kDa for the control to 80 kDa, and the average broth viscosity during 8-16 h decreased from 360 mPa s for the control to 290 mPa s. The average oxygen mass transfer coefficient K(L)a increased from 10h(-1) for the control to 35 h(-1) and the average dissolved oxygen level increased from 1% of air saturation in the control to 10%. HA production increased from 5.0 g/L for the control to 6.5 g/L, and contributed to the increased redox potential and energy charge. This novel process not only significantly enhanced production of low molecular weight HA, but also improved purification efficiency due to a decreased broth viscosity. Low molecular weight HA finds applications in biomedical and healthcare fields.

  15. Mineral Dissolution and Metal Mobility From Rhizosphere and Non-rhizosphere Soils by Low Molecular Weight Organic Acids

    NASA Astrophysics Data System (ADS)

    Little, D. A.; Field, J. B.; Welch, S. A.

    2005-12-01

    This research is part of an ongoing investigation of micro-biogeochemistry in the rhizosphere of co-occurring Eucalyptus mannifera and Acacia falciformis on the Southern Tablelands of New South Wales, Australia. While there is still considerable controversy in the literature regarding the roles of low molecular weight organic acids in soil processes there is growing evidence suggesting low molecular weight compounds, especially di-carboxylic acids, have large impacts on mineral dissolution and metal mobility in the rhizosphere. Rhizosphere and non-rhizosphere samples from adjacent E. mannifera and A. falciformis trees were subjected to four separate treatments in sets of 3 replicates; +oxalic acid, +malic acid, +citric acid or +NaCl control solution. These three acids were chosen because they are produced by rhizosphere species and they form stable complexes with nutrient elements such as Phosphorus (P), Iron (Fe), and Calcium (Ca). Solution samples were collected at day 1, day 8 and day 15 for pH measurement and analysed for major and trace elements by ICP-AES and ICP-MS. The results of the preliminary dissolution experiments show that milli-molar concentrations of individual organic acids, malate and oxalate, and in particular citrate, greatly increase the release of major and trace metals to solution compared to inorganic controls. Concentrations of Al and Fe in organic acid solutions were up to 10 times greater than in the inorganic controls. Si concentrations were a factor of 2-5 greater in the organic acid solutions, suggesting preferential weathering of Fe and Al oxyhydroxide phases rather than primary silicate minerals. Dissolution of elements such as Si, Al and Fe from rhizosphere soils were about twice that observed from non-rhizosphere soils, further supporting this. Interestingly Ti and Zr, which are usually considered to be immobile during chemical weathering and are not usually taken up by plants, were also mobilised from the rhizosphere soils

  16. Stereocomplexation of low molecular weight poly(L-lactic acid) and high molecular weight poly(D-lactic acid), radiation crosslinking PLLA/PDLA stereocomplexes and their characterization

    NASA Astrophysics Data System (ADS)

    Quynh, Tran Minh; Mai, Hoang Hoa; Lan, Pham Ngoc

    2013-02-01

    Poly(L-lactic acid)s (PLLAx) were synthesized from L-lactic acid by polycondensation. Different stereocomplexes were also obtained with equimolar mixtures of synthesized PLLAx and a commercial PDLA. The stereocomplexes were crosslinked with triallyl isocyanurate (TAIC) by gamma irradiation. Crosslinking density increased with radiation doses, the heavier the crosslinking network, the lower its swelling degree. The crosslinking structures were introduced in the stereocomplexes inhibiting the mobility for crystallization of PLLA molecules. Thermal and mechanical properties of PLA stereocomplexes were remarkably enhanced by radiation induced crosslinking. PLA stereocomplex does not seem to be degraded by PLLA degrading microorganisms existing in compost at room temperature, but the synthesized PLLA was significantly degraded.

  17. Ultra-high molecular weight polyethylene (UHMW-PE) and its application in microporous separators for lead/acid batteries

    NASA Astrophysics Data System (ADS)

    Wang, L. C.; Harvey, M. K.; Ng, J. C.; Scheunemann, U.

    The polyethylene (PE) used in separators for automotive lead/acid batteries is actually UHMW-PE (ultra high molecular weight polyethylene). Microporous PE separators were commercialized in the early 1970s. Since then, they have gained in popularity in the lead/acid battery industry, particularly in SLI (starting, lighting and ignition) automotive applications. This paper provides an introductory overview of the UHMW-PE polymer and its contributions to the PE battery separator manufacturing process, battery assembly and battery performance, in comparison with other conventional separators such as polyvinyl chloride (PVC) and glass fibre.

  18. Efficacy and Safety of a Low-Molecular Weight Hyaluronic Acid Topical Gel in the Treatment of Facial Seborrheic Dermatitis

    PubMed Central

    Rowland Powell, Callie

    2012-01-01

    Objective: Hyaluronic acid sodium salt gel 0.2% is a topical device effective in reducing skin inflammation. Facial seborrheic dermatitis, characterized by erythema and or flaking/scaling in areas of high sebaceous activity, affects up to five percent of the United States population. Despite ongoing studies, the cause of the condition is yet unknown, but has been associated with yeast colonization and resultant immune-derived inflammation. First-line management typically is with topical steroids as well as the immunosuppressant agents pimecrolimus and tacrolimus. The objective of this study was to evaluate the efficacy and safety of a topical anti-inflammatory containing low-molecular weight hyaluronic acid. Design and setting: Prospective, observational, non-blinded safety and efficacy study in an outpatient setting. Participants: Individuals 18 to 75 years of age with facial seborrheic dermatitis. Measurements: Outcome measures included scale, erythema, pruritus, and the provider global assessment, which were all measured on a five-point scale. Subjects were assessed at Baseline, Week 2, Week 4, and Week 8. Results: Interim data for 7 of 15 subjects are presented. Hyaluronic acid sodium salt gel 0.2% was shown through visual grading assessments to improve the provider global assessment by 47.62 percent from Baseline to Week 4. Reductions in scale, erythema, and pruritus were 66.67, 50, and 60 percent, respectively at Week 4. At Week 8, the provider global assessment was improved from baseline in 100 percent of subjects. Conclusion: Treatment with topical low-molecular weight hyaluronic acid resulted in improvement in the measured endpoints. Topical low-molecular weight hyaluronic acid is another option that may be considered for the treatment of facial seborrheic dermatitis in the adult population. Compliance and tolerance were excellent. PMID:23125886

  19. Amino acid composition, molecular weight distribution and gel electrophoresis of walnut (Juglans regia L.) proteins and protein fractionations.

    PubMed

    Mao, Xiaoying; Hua, Yufei; Chen, Guogang

    2014-01-27

    As a by-product of oil production, walnut proteins are considered as an additional source of plant protein for human food. To make full use of the protein resource, a comprehensive understanding of composition and characteristics of walnut proteins are required. Walnut proteins have been fractionated and characterized in this study. Amino acid composition, molecular weight distribution and gel electrophoresis of walnut proteins and protein fractionations were analyzed. The proteins were sequentially separated into four fractions according to their solubility. Glutelin was the main component of the protein extract. The content of glutelin, albumin, globulin and prolamin was about 72.06%, 7.54%, 15.67% and 4.73% respectively. Glutelin, albumin and globulin have a balanced content of essential amino acids, except for methionine, with respect to the FAO pattern recommended for adults. SDS-PAGE patterns of albumin, globulin and glutelin showed several polypeptides with molecular weights 14.4 to 66.2 kDa. The pattern of walnut proteins in two-dimension electrophoresis (2-DE) showed that the isoelectric point was mainly in the range of 4.8-6.8. The results of size exclusion chromatogram indicated molecular weight of the major components of walnut proteins were between 3.54 and 81.76 kDa.

  20. Amino Acid Composition, Molecular Weight Distribution and Gel Electrophoresis of Walnut (Juglans regia L.) Proteins and Protein Fractionations

    PubMed Central

    Mao, Xiaoying; Hua, Yufei; Chen, Guogang

    2014-01-01

    As a by-product of oil production, walnut proteins are considered as an additional source of plant protein for human food. To make full use of the protein resource, a comprehensive understanding of composition and characteristics of walnut proteins are required. Walnut proteins have been fractionated and characterized in this study. Amino acid composition, molecular weight distribution and gel electrophoresis of walnut proteins and protein fractionations were analyzed. The proteins were sequentially separated into four fractions according to their solubility. Glutelin was the main component of the protein extract. The content of glutelin, albumin, globulin and prolamin was about 72.06%, 7.54%, 15.67% and 4.73% respectively. Glutelin, albumin and globulin have a balanced content of essential amino acids, except for methionine, with respect to the FAO pattern recommended for adults. SDS-PAGE patterns of albumin, globulin and glutelin showed several polypeptides with molecular weights 14.4 to 66.2 kDa. The pattern of walnut proteins in two-dimension electrophoresis (2-DE) showed that the isoelectric point was mainly in the range of 4.8–6.8. The results of size exclusion chromatogram indicated molecular weight of the major components of walnut proteins were between 3.54 and 81.76 kDa. PMID:24473146

  1. Proton play in the formation of low molecular weight chitosan (LWCS) by hydrolyzing chitosan with a carbon based solid acid.

    PubMed

    Krishnan, R Akhil; Deshmukh, Pranjal; Agarwal, Siddharth; Purohit, Poorvi; Dhoble, Deepa; Waske, Prashant; Khandekar, Dileep; Jain, Ratnesh; Dandekar, Prajakta

    2016-10-20

    Low molecular weight chitosan (LWCS) constitute a special class of value added chemicals that are primarily obtained from crustacean shells, which are the main water pollutants from crabs and shrimp processing centers. Unlike chitin and chitosan, LWCS possess improved solubility in water and aqueous solutions, making them widely applicable in numerous fields ranging from drug delivery to waste water treatment. Among the methods employed for their production, chemical breakdown by strong liquid acids has yielded good success. However, this method is met with severe concerns arising from the harsh nature of liquid acids, which may corrode the reactors for commercial synthesis, and their limited reusability. The physical methods like ultrasound and microwave are energy intensive in nature, while the enzymatic methods are expensive and offers limited scope for reuse. We have attempted to overcome these problems by employing carbon based solid acid (CSA) for hydrolyzing chitosan to LWCS. CSA can be easily produced using activated carbon, a cost-effective and easily available raw material. Reactions were carried out between chitosan and CSA in a hydrothermal glass reactor and the products, separated by cold centrifugation, were purified and dried. The dried products were characterized for their molecular weight and solubility. Results indicated more than ten-fold decrease in the molecular weight of chitosan and the product exhibited water solubility. The CSA could be used upto four times, without regeneration, to give a consistent quality product. The aqueous solution of resulting LWCS exhibited a pH of 6.03±0.11, as against the acidic pH range of solutions of commercially available LWCS, indicating its suitability for biomedical applications. Our investigation facilitates a 'green approach' that may be employed for commercial production of value added chemicals from waste products of marine industry. PMID:27474584

  2. Exopolysaccharides from lactic acid bacteria: structural analysis, molecular weight effect on immunomodulation.

    PubMed

    Surayot, Utoomporn; Wang, Jianguo; Seesuriyachan, Phisit; Kuntiya, Ampin; Tabarsa, Mehdi; Lee, YongJin; Kim, Jin-Kyung; Park, WooJung; You, SangGuan

    2014-07-01

    Exopolysaccharides (EPS) obtained from the culture medium of Lactobacillus confusus TISTR 1498 were investigated to determine their molecular characteristics and the effect of molecular weight (Mw) on immunomodulatory activity. The EPS mainly consisted of carbohydrates (81.9±2.4%) with only one type of monosaccharide, D-glucose, which was mostly connected by α-(1→6) glycosidic linkages. The EPS itself was unable to stimulate RAW264.7 cells to produce pro-inflammatory mediator nitric oxide (NO) and cytokines. However, considerable stimulation of RAW264.7 cells was observed by the low Mw of EPSs having Mw values≤70×10(3)g/mol. The partially hydrolyzed EPS stimulated RAW264.7 cells to induce considerable NO and various cytokine production such as TNF-α, IL-1β, IL-6 and IL-10 via up-regulation of their mRNA expression. In addition, the degradation Iκ-B and the phosphorylation of c-Jun NH2-terminal kinase (JNK) were facilitated by BW-30 and MW-40, suggesting that the partially hydrolyzed EPS stimulated RAW264.7 cells through the activation of NF-κB and JNK pathways.

  3. Microencapsulation of linoleic acid with low- and high-molecular-weight components of soluble soybean polysaccharide and its oxidation process.

    PubMed

    Fang, Xu; Watanabe, Yoshiyuki; Adachi, Shuji; Matsumura, Yasuki; Mori, Tomohiko; Maeda, Hirokazu; Nakamura, Akihiro; Matsuno, Ryuichi

    2003-09-01

    Soluble soybean polysaccharide (SSPS) was fractionated into its low- (LMW) and high-molecular-weight (HMW) components to test their antioxidative and emulsifying properties. Linoleic acid was emulsified with an aqueous solution of SSPS, HMW, a mixture of LMW or HMW with maltodextrin, or maltodextrin alone. The emulsions prepared with SSPS, HWM and the mixture of HMW with maltodextrin were stable. These emulsions were spay-dried to produce microcapsules. The encapsulated linoleic acid was oxidized at 37 degrees C and at various levels of relative humidity. Linoleic acid encapsulated with the mixture of LMW with maltodextrin or HMW was stable to oxidation, and this stability increased as the weight fraction of LMW in the mixture was increased. The LMW components also had high DPPH-radical scavenging activity. These results indicate that LMW played an important role in suppressing or retarding the oxidation of linoleic acid encapsulated with SSPS. The oxidative stability of linoleic acid encapsulated with a mixture of the LMW and HMW components was high at low and high relative humidity, but not at intermediate levels of relative humidity.

  4. High molecular weight hyaluronic acid increases the differentiation potential of the murine chondrocytic ATDC5 cell line.

    PubMed

    Sato, Eiichi; Ando, Takashi; Ichikawa, Jiro; Okita, Genki; Sato, Nobutaka; Wako, Masanori; Ohba, Tetsuro; Ochiai, Satoshi; Hagino, Tetsuo; Jacobson, Richard; Haro, Hirotaka

    2014-12-01

    Osteoarthritis (OA) is a group of common, chronic, and painful inflammatory joint diseases. One important finding in OA patients is a remarkable decrease in the molecular weight of hyaluronic acid (HA) in the synovial fluid of affected joints. Therapeutic HA is available to patients in most parts of the world as a viscosupplementation product for the treatment of OA. Previous clinical reports show that high molecular weight HA (HMWHA) more effectively relieves pain than low molecular weight HA (LMWHA). However, the mechanism behind this finding remains unclear. In this study, we investigated whether a LMWHA (Low-0.9 MDa) and two types of HMWHA (High-1.9 MDa and 6 MDa) differentially affected chondroregulatory action. We tested this using ATDC5 cell, a murine chondrocytic cell line widely used in culture systems to study chondrogenic differentiation. We found that HMWHA, especially hylan G-F 20 (High-6 MDa), significantly induced aggrecan and proteoglycan accumulation, nodule formation, and mRNA expression of chondrogenic differentiation markers in a time- and dose-dependent manner. In addition, we showed that HMWHA prevented TNF-α induced inhibition of chondrogenic differentiation, with no effect on cell proliferation or viability. These results reveal that HMWHA significantly promotes chondrogenic differentiation of ATDC5 cells in vitro, and suggest that HMWHA plays a significant chondroregulatory role in vivo.

  5. An equation to estimate the difference between theoretically predicted and SDS PAGE-displayed molecular weights for an acidic peptide.

    PubMed

    Guan, Yihong; Zhu, Qinfang; Huang, Delai; Zhao, Shuyi; Jan Lo, Li; Peng, Jinrong

    2015-01-01

    The molecular weight (MW) of a protein can be predicted based on its amino acids (AA) composition. However, in many cases a non-chemically modified protein shows an SDS PAGE-displayed MW larger than its predicted size. Some reports linked this fact to high content of acidic AA in the protein. However, the exact relationship between the acidic AA composition and the SDS PAGE-displayed MW is not established. Zebrafish nucleolar protein Def is composed of 753 AA and shows an SDS PAGE-displayed MW approximately 13 kDa larger than its predicted MW. The first 188 AA in Def is defined by a glutamate-rich region containing ~35.6% of acidic AA. In this report, we analyzed the relationship between the SDS PAGE-displayed MW of thirteen peptides derived from Def and the AA composition in each peptide. We found that the difference between the predicted and SDS PAGE-displayed MW showed a linear correlation with the percentage of acidic AA that fits the equation y = 276.5x - 31.33 (x represents the percentage of acidic AA, 11.4% ≤ x ≤ 51.1%; y represents the average ΔMW per AA). We demonstrated that this equation could be applied to predict the SDS PAGE-displayed MW for thirteen different natural acidic proteins. PMID:26311515

  6. Distribution of heavy metals by the molecular-weight fractions of humic acids in the soils of long-term field experiments

    NASA Astrophysics Data System (ADS)

    Karpukhin, A. I.; Bushuev, N. N.

    2007-03-01

    The influence of different agricultural treatments on the contents of Cd, Zn, and Co in the organic matter and humic acids of soddy-podzolic and dark gray forest soils was studied in long-term field experiments. The use of gel chromatography proved the complicated molecular-weight composition of the humic acids in all the studied soils. The contents of heavy metals and their distribution by the molecular-weight fractions of humic acids were determined in the experimental soils and in the virgin podzolic soils. The complex nature of organomineral compounds of Cd and Zn with humic acids was shown by means of gel filtration. The thermodynamic stability of the organomineral complexes increased with the increasing weight of the initial molecular-weight fractions of humic acids.

  7. Low-molecular-weight (4.5S) ribonucleic acid in higher-plant chloroplast ribosomes.

    PubMed Central

    Whitfeld, P R; Leaver, C J; Bottomley, W; Atchison, B

    1978-01-01

    A species of RNA that migrates on 10% (w/v) polyacrylamide gels between 5S and 4S RNA was detected in spinach chloroplasts. This RNA (referred to as 4.5 S RNA) was present in amounts equimolar to the 5S RNA and its molecular weight was estimated to be approx. 33 000. Fractionation of the chloroplast components showed that the 4.5S RNA was associated with the 50 S ribosomal subunit and that it could be removed by washing the ribosomes with a buffer containing 0.01 M-EDTA and 0.5 M-KCl. It did not appear to be a cleavage product of the labile 23 S RNA of spinach chloroplast ribosomes. When 125I-labelled 4.5 S RNA was hybridized to fragments of spinach chloroplast DNA produced by SmaI restriction endonuclease, a single fragment (mol.wt. 1.15 times 10(6)) became labelled. The same DNA fragment also hybridized to chloroplast 5 S RNA and part of the 23 S RNA. It was concluded that the coding sequence for 4.5 S RNA was part of, or immediately adjacent to, the rRNA-gene region in chloroplast DNA . A comparable RNA species was observed in chloroplasts of tobacco and pea leaves. Images Fig. 8. PMID:743229

  8. A Delicate Balance When Substituting a Small Hydrophobe onto Low Molecular Weight Polyethylenimine to Improve Its Nucleic Acid Delivery Efficiency.

    PubMed

    Meneksedag-Erol, Deniz; KC, Remant Bahadur; Tang, Tian; Uludağ, Hasan

    2015-11-11

    High molecular weight (HMW) polyethylenimine (PEI) is one of the most versatile nonviral gene vectors that was extensively investigated over the past two decades. The cytotoxic profile of HMW PEI, however, encouraged a search for safer alternatives. Because of lack of cytotoxicity of low molecular weight (LMW) PEI, enhancing its performance via hydrophobic modifications has been pursued to this end. Since the performance of modified PEIs depends on the nature and extent of substituents, we systematically investigated the effect of hydrophobic modification of LMW (1.2 kDa) PEI with a short propionic acid (PrA). Moderate enhancements in PEI hydrophobicity resulted in enhanced cellular uptake of polyplexes and siRNA-induced silencing efficacy, whereas further increase in PrA substitution abolished the uptake as well as the silencing. We performed all-atom molecular dynamics simulations to elucidate the mechanistic details behind these observations. A new assembly mechanism was observed by the presence of hydrophobic PrA moieties, where PrA migrated to core of the polyplex. This phenomenon caused higher surface hydrophobicity and surface charge density at low substitutions, and it caused deleterious effects on surface hydrophobicity and cationic charge at higher substitutions. It is evident that an optimal balance of hydrophobicity/hydrophilicity is needed to achieve the desired polyplex properties for an efficient siRNA delivery, and our mechanistic findings should provide valuable insights for the design of improved substituents on nonviral carriers.

  9. The role of low molecular weight organic acids on controlling pH in coastal sea water

    NASA Astrophysics Data System (ADS)

    Ding, H.

    2015-12-01

    Series investigation of the Jiaozhou Bay, China, observed existences of three low molecular weight organic acids (LMWOAs), including lactic acid, acetic acid and formic acid, with high concentration in the sea water. Generally, their amount accounted for about 20% of DOC in the sea water of the bay. Human activities around the bay were considered as the major source of the LMWOAs. Also, long term detection showed that the pH value in the Jiaozhou Bay was lower than that in the adjacent Yellow Sea. On average, the difference of pH values between the bay and the Yellow was about 0.2. Due to higher concentrations of the LMWOAs, their contribution to lower pH value of the bay should not be ignored. To validate the effect of LMWOAs on the pH value of the bay, a new software was developed to calculate the pH value in the sea water samples based on alkalinity by adding three items of the three organic acids in the expression. Compared to the traditional pH calculating software, the new software could improve the calculating results significantly. Our results confirmed that LMWOAs was an important control factor to adjust pH values in coastal area.

  10. [Effect of low molecular weight organic acids on Pb2+ adsorption and desorption by constant charge soil colloids].

    PubMed

    Yang, Yati; Wang, Xudong; Zhang, Yiping; Qu, Aihua

    2003-11-01

    The isothermal curves of Pb2+ adsorption-desorption by soil colloids followed Freundlich and Langmuir equation. The adsorption constant Ka showed the trend of old manured loessal soil > yellow loessal soil > dark cultivated loessal soil > yellow cinamon soil, which was consistent with surface charge density sigma 0, an indicator of the strength of Pb2+ adsorption by each soil colloid. Low molecular-weight organic acids (LMWOAs) made Pb2+ adsorbed amount decreased and adsorption affinity increased, and the effect of citric acid was larger than that of oxalic acid. The constant Kd of residual Pb2+ adsorption after desorption showed the trend of old manured loessal soil > yellow cinamon soil > dark cultivated loessal soil > yellow loessal soil, which reflected the adsorption strength of residual Pb2+ after desorption, and was related to the contents of organic matter and free ferric oxide. The isothermal curves of Pb2+ desorption from soil colloids were obvious higher than those of Pb2+ adsorption. In NaNO3 and oxalic acid background solution, the isothermal curves of Pb2+ adsorption were far away from those of Pb2+ desorption, showing that the hysteretic degree between adsorption and desorption was very large. The isothermal curves of Pb2+ desorption from soil colloids were closed to those of Pb2+ adsorption in citric acid background solution, which showed that the Pb adsorption and desorption was reversible.

  11. Reducing THMFP by H2O2/UV oxidation for humic acid of small molecular weight.

    PubMed

    Yen, Hsing Yuan; Yen, Li Shuang

    2015-01-01

    In this study, the merits of using H2O2/UV oxidation for reducing trihalomethane formation potential (THMFP), colour, and dissolved organic carbon (DOC) of smaller molecular humic acid were investigated, especially the energy consumption based on EEO. The results show that THMFP decreases by increasing oxidation time, H2O2 dose and UV intensity. The reaction constant in descending order is kColour>kDOC>kTHMFP. Furthermore, EEO shows three trends. First, it decreases as H2O2 dose increases. That is, by increasing the amount of H2O2 dose, the electrical energy efficiency becomes better. Second, EEO,9 W>EEO,13 W, implying that higher UV power would result in a higher electrical energy efficiency. Third, EEO,THMFP>EEO,DOC>EEO,colour. That is, the electric energy efficiency is the best for colour removal, second for DOC removal, and third for THMFP reduction. The operation costs for 90% removal of colour, DOC, and THMFP are from 0.31 to 0.69, from 0.78 to 1.72, and from 1.11 to 2.29 US$/m3, respectively. However, reducing THMs to Taiwan's drinking water standard of 80 µg/L needs only 0.25-0.60 US$/m3. Therefore, the condition with UV of 9 W, H2O2 of 50 mg/L, and oxidation time of 23 min can be applied for THMs reduction as the cost is the smallest of 0.25 US$/m3, even lower than current Taiwan's drinking water price of 0.3 US$/m3.

  12. Phragmites australis response to Cu in terms of low molecular weight organic acids (LMWOAs) exudation: Influence of the physiological cycle

    NASA Astrophysics Data System (ADS)

    Rocha, A. Cristina S.; Almeida, C. Marisa R.; Basto, M. Clara P.; Vasconcelos, M. Teresa S. D.

    2014-06-01

    Plant roots have the ability to produce and secrete substances, such as aliphatic low molecular weight organic acids (ALMWOAs), into the rhizosphere for several purposes, including in response to metal contamination. Despite this, little is yet known about the exudation of such substances from marsh plants roots in response to metal exposure. This work aimed at assessing the influence of the physiological cycle of marsh plants on the exudation of ALMWOAs in response to Cu contamination. In vitro experiments were carried out with Phragmites australis specimens, collected in different seasons. Plant roots were exposed to freshwater contaminated with two different Cu concentrations (67 μg/L and 6.9 mg/L), being the ALMWOAs released by the roots measured. Significant differences (both qualitative and quantitative) were observed during the Phragmites australis life cycle. At growing stage, Cu stimulated the exudation of oxalic and formic acids but no significant stimulation was observed for citric acid. At developing stage, exposure to Cu caused inhibition of oxalic acid exudation whereas citric acid liberation was stimulated but only in the media spiked with the lowest Cu concentration tested. At the decaying stage, no significant variation on oxalic acid was observed, whereas the citric and formic acids release increased as a consequence of the plant exposure to Cu. The physiological cycle of Phragmites australis, and probably also of other marsh plants, is therefore an important feature conditioning plants response to Cu contamination, in terms of ALMWOAs exudation. Hence this aspect should be considered when conducting studies on rhizodeposition involving marsh plants exposed to metals and in the event of using marsh plants for phytoremediation purposes in contaminated estuarine areas.

  13. A novel method for determination of low molecular weight dicarboxylic acids in background atmospheric aerosol using ion chromatography.

    PubMed

    Tsai, Ying I; Hsieh, Li-Ying; Weng, Tzu-Hsiang; Ma, Yu-Chien; Kuo, Su-Ching

    2008-09-19

    This paper describes a novel gradient elution ion chromatographic method using a Dionex AS11 system for the determination of low molecular weight dicarboxylic acids (low-M(w) DCAs) in background atmospheric aerosol. Interference with the oxalic acid peak from sulfate in background PM(2.5) aerosol, 15.8 times the oxalic acid concentration, was remedied by removing sulfate using a barium cartridge, whilst interference with the malonic acid peak from carbonate was reduced by using a carbonate removal device. An alternative remedy to sulfate interference was use of an AS14 system using isocratic eluent, and this produced good resolution of oxalic acid from a high sulfate peak. In both the AS11 and the AS14 system, linear correlation coefficients were at all times >0.9990 with excellent linear range, the recoveries ranged from 92.8 to 106%, with relative standard deviation of 3.67-6.30%, whilst method detection limits (MDLs) ranged from 0.36microgL(-1) for malic acid to 3.87microgL(-1) for maleic acid. These data indicate that the analytical methods developed herein produce excellent separation efficiency and good determination of low-M(w) DCAs with satisfactory accuracy, recoveries, and MDLs. Samples left at room temperature (20 degrees C) for 300min in a simulation of the 'waiting time' involved in the proposed IC analysis decayed to between 86% (oxalic acid) and 39% (succinic and malonic acids) of their original concentration, whilst at 4 degrees C concentrations remained at 96-101% of original, indicating that maintaining samples at a low temperature prior to injection into the IC analyzer is vital for obtaining accurate results when analyzing low-M(w) DCAs. Oxalic acid was found to be the most prevalent low-M(w) DCA in background aerosol, comprising 57% of the total low-M(w) DCAs and 0.959% of the PM(2.5) aerosol mass, followed by succinic acid and malonic acid.

  14. Physicochemical properties and ecotoxicological effects of yttrium oxide nanoparticles in aquatic media: Role of low molecular weight natural organic acids.

    PubMed

    Zhang, Fan; Wang, Zhuang; Wang, Se; Fang, Hao; Chen, Mindong; Xu, Defu; Tang, Lili; Wang, Degao

    2016-05-01

    Understanding how engineered nanoparticles (ENPs) interact with natural organic acids is important to ecological risk assessment of ENPs, but this interaction remains poorly studied. Here, we investigate the dispersion stability, ion release, and toxicity of yttrium oxide nanoparticles (nY2O3) suspensions after exposure to two low molecular weight natural organic acids (LOAs), namely benzoic acid and gallic acid. We find that in the presence of LOAs the nY2O3 suspensions become more stable with surface zeta potential more positive or negative, accompanied by small agglomerated size. LOA interaction with nY2O3 is shown to promote the release of dissolved yttrium from the nanoparticles, depending on the concentrations of LOAs. Toxic effects of the nY2O3 suspensions incubated with LOAs on Scenedesmus obliquus as a function of their mixture levels show three types of signs: stimulation, inhibition, and alleviation. The mechanism of the effects of LOAs on the nY2O3 toxicity may be mainly associated with the degree of agglomeration, particle-induced oxidative stress, and dissolved yttrium. Our results stressed the importance of LOA impacts on the fate and toxicity of ENPs in the aquatic environment.

  15. Effects of surfactants on low-molecular-weight organic acids to wash soil zinc.

    PubMed

    Chen, Yue; Zhang, Shirong; Xu, Xiaoxun; Yao, Ping; Li, Ting; Wang, Guiyin; Gong, Guoshu; Li, Yun; Deng, Ouping

    2016-03-01

    Soil washing is an effective approach to the removal of heavy metals from contaminated soil. In this study, the effects of the surfactants sodium dodecyl sulfate, Triton X-100, and non-ionic polyacrylamide (NPAM) on oxalic acid, tartaric acid, and citric acid used to remove zinc from contaminated soils were investigated. The Zn removal efficiencies of all washing solutions showed a logarithmic increase with acid concentrations from 0.5 to 10.0 g/L, while they decreased as pH increased from 4 to 9. Increasing the reaction time enhanced the effects of surfactants on Zn removal efficiencies by the acids during washing and significantly (P < 0.05) improved the removal under some mixed cases. Oxalic acid suffered antagonistic effects from the three surfactants and seriously damaged soil nutrients during the removal of soil Zn. Notably, the three surfactants caused synergistic effects on tartaric and citric acid during washing, with NPAM leading to an increase in Zn removal by 5.0 g/L citric acid of 10.60 % (P < 0.05) within 2 h. NPAM also alleviated the loss of cation exchange capacity of washed soils and obviously improved soil nitrogen concentrations. Overall, combining citric acid with NPAM offers a promising approach to the removal of zinc from contaminated soil.

  16. Biosynthesis of high molecular weight hyaluronic acid by Streptococcus zooepidemicus using oxygen vector and optimum impeller tip speed.

    PubMed

    Lai, Zee-Wei; Rahim, Raha Abdul; Ariff, Arbakariya B; Mohamad, Rosfarizan

    2012-09-01

    The potential use of n-dodecane and n-hexadecane as oxygen vectors for enhancing hyaluronic acid (HA) biosynthesis by Streptococcus zooepidemicus ATCC 39920 was investigated using a 2-L stirred-tank bioreactor equipped with helical ribbon or Rushton turbine impellers. The volumetric fraction of the oxygen vector influenced the gas-liquid volumetric oxygen transfer coefficient (K(L)a) positively. Batch HA fermentation with 1% (v/v) n-dodecane or 0.5% (v/v) n-hexadecane addition was carried out at different impeller tip speeds. Even though cell growth was lower in the fermentation with oxygen vector addition, the HA productivity and molecular weight were higher when compared to the fermentation without oxygen vector at low impeller tip speed. The highest HA concentration (4.25 gHA/l) and molecular weight (1.54 × 10(7) Da) were obtained when 0.5% (v/v) n-hexadecane and 0.785 m/s impeller tip speed of helical ribbon were used.

  17. Biosynthesis of high molecular weight hyaluronic acid by Streptococcus zooepidemicus using oxygen vector and optimum impeller tip speed.

    PubMed

    Lai, Zee-Wei; Rahim, Raha Abdul; Ariff, Arbakariya B; Mohamad, Rosfarizan

    2012-09-01

    The potential use of n-dodecane and n-hexadecane as oxygen vectors for enhancing hyaluronic acid (HA) biosynthesis by Streptococcus zooepidemicus ATCC 39920 was investigated using a 2-L stirred-tank bioreactor equipped with helical ribbon or Rushton turbine impellers. The volumetric fraction of the oxygen vector influenced the gas-liquid volumetric oxygen transfer coefficient (K(L)a) positively. Batch HA fermentation with 1% (v/v) n-dodecane or 0.5% (v/v) n-hexadecane addition was carried out at different impeller tip speeds. Even though cell growth was lower in the fermentation with oxygen vector addition, the HA productivity and molecular weight were higher when compared to the fermentation without oxygen vector at low impeller tip speed. The highest HA concentration (4.25 gHA/l) and molecular weight (1.54 × 10(7) Da) were obtained when 0.5% (v/v) n-hexadecane and 0.785 m/s impeller tip speed of helical ribbon were used. PMID:22608992

  18. Interactions of low molecular weight aromatic acids and amino acids with goethite, kaolinite and bentonite with or without organic matter coating

    NASA Astrophysics Data System (ADS)

    Gao, Jiajia; Jansen, Boris; Cerli, Chiara; Kalbitz, Karsten

    2015-04-01

    Interaction of organic matter molecules with the soil's solid phase is a key factor influencing the stabilization of carbon in soils and thus forms a crucial aspect of the global carbon cycle. While subject of much research attention so far, we still have much to learn about such interactions at the molecular level; in particular in the light of competition between different classes of organic molecules and in the presence of previously adsorbed soil organic matter. We studied the interaction of a group of low molecular weight (LMW) aromatic acids (salicylic, syringic, vanillic and ferulic acid) and amino acids (lysine, glutamic, leucine and phenylalanine) on goethite, kaolinite and bentonite with and without previously adsorbed dissolved organic matter (DOM). For this we used batch experiments at pH = 6.0 where some of the organic compounds were positively charged (i.e. lysine) or negatively charged (i.e. glutamic and salicylic acid) while the minerals also displayed positively (i.e. goethite) or negatively charged surfaces (i.e. bentonite). We found much higher sorption of salicylic acid and lysine than other compounds. On the bare minerals we found a great variety of sorption strength, with salicylic acid strongly adsorbed, while syringic, vanillic and ferulic acid showed little or no adsorption. For the amino acids, protonated lysine showed a stronger affinity to negatively charged kaolinite and bentonite than other amino acids. While deprotonated glutamic acid showed the strongest adsorption on goethite. Leucine and phenylalanine showed hardly any adsorption on any of the minerals. When present concurrently, amino acids decreased the sorption of salicylic acid on the three types of mineral, while the presence of LMW aromatic acids increased the sorption of lysine on kaolinite and bentonite and the sorption of glutamic acid on goethite. The presence of previously adsorbed DOM reduced the sorption of salicylic acid and lysine. The results confirm that

  19. Gas/particle partitioning of low-molecular-weight dicarboxylic acids at a suburban site in Saitama, Japan

    NASA Astrophysics Data System (ADS)

    Bao, Linfa; Matsumoto, Mariko; Kubota, Tsutomu; Sekiguchi, Kazuhiko; Wang, Qingyue; Sakamoto, Kazuhiko

    2012-02-01

    Low-molecular-weight dicarboxylic acids (diacids) exhibit semivolatile behavior in the atmosphere, but their partitioning between the gaseous and particulate phases is still unclear. An annular denuder-filter pack system with a cyclone PM 2.5 was employed to investigate the gaseous and particulate phase concentrations of diacids, with high collection efficiency of most target compounds. Saturated diacids, unsaturated diacids, ketocarboxylic acids, and dicarbonyls were determined in gaseous and particulate samples collected from a suburban site in Japan, during 2007 summer, 2008 late-winter and early-winter. The concentrations of gaseous and particulate diacids in early-winter were lower than those in summer, but higher than those in late-winter. Individual diacid in gaseous phase showed a relatively good correlation with ambient oxidants, but a low correlation with NO gas (a primary pollutant). Particulate fraction to the total amount ( FP) of individual acid was larger in winter than in summer, and also was larger at night than in the daytime. In the same sample, individual diacid and ketocarboxylic acid had higher particulate phase occurrence ( FP > 56% in summer), whereas unsaturated diacid had higher gaseous phase occurrence ( FP < 18% in summer). In summer, gas/particle partitioning of diacids varied diurnally; FP values of oxalic and glyoxylic acids increased from their lowest values in the morning to their highest values at night, exhibiting the similar diurnal variation of relative humidity in the atmosphere. The higher humidity at night may lead to the formation of droplets in which water-soluble gaseous phases can dissolve, thus promoting gas-to-particle conversion. These results suggest that gas/particle partitioning of diacids depends not only on the concentrations in the gaseous phase by photochemical oxidation, but also on the characteristics of the atmosphere (e.g., temperature, sunlight, and relative humidity) and the aerosols (e.g., acidity

  20. Low molecular weight chemicals, hypersensitivity, and direct toxicity: the acid anhydrides.

    PubMed Central

    Venables, K M

    1989-01-01

    The acid anhydrides are a group of reactive chemicals used widely in alkyd and epoxy resins. The major hazards to health are mucosal and skin irritation and sensitisation of the respiratory tract. Most occupational asthma caused by acid anhydrides appears to be immunologically mediated. Immunological mechanisms have been proposed to explain an influenza-like syndrome and pulmonary haemorrhage, but direct toxicity may also be important in the aetiology of these conditions. PMID:2653411

  1. Stability of Chloropyromorphite in Ryegrass Rhizosphere as Affected by Root-Secreted Low Molecular Weight Organic Acids

    PubMed Central

    Wei, Wei; Wang, Yu; Wang, Zheng; Han, Ruiming; Li, Shiyin; Wei, Zhenggui; Zhang, Yong

    2016-01-01

    Understanding the stability of chloropyromorphite (CPY) is of considerable benefit for improving risk assessment and remediation strategies in contaminated water and soil. The stability of CPY in the rhizosphere of phosphorus-deficient ryegrass was evaluated to elucidate the role of root-secreted low molecular weight organic acids (LMWOAs) on the dissolution of CPY. Results showed that CPY treatments significantly reduced the ryegrass biomass and rhizosphere pH. The presence of calcium nitrate extractable lead (Pb) and phosphorus (P) suggested that CPY in the rhizosphere could be bioavailable, because P and Pb uptake by ryegrass potentially provided a significant concentration gradient that would promote CPY dissolution. Pb accumulation and translocation in ryegrass was found to be significantly higher in P-sufficient conditions than in P-deficient conditions. CPY treatments significantly enhanced root exudation of LMWOAs irrigated with P-nutrient solution or P-free nutrient solution. Oxalic acid was the dominant species in root-secreted LMWOAs of ryegrass under P-free nutrient solution treatments, suggesting that root-secreted oxalic acid may be the driving force of root-induced dissolution of CPY. Hence, our work, provides clarifying hints on the role of LMWOAs in controlling the stability of CPY in the rhizosphere. PMID:27494023

  2. Stability of Chloropyromorphite in Ryegrass Rhizosphere as Affected by Root-Secreted Low Molecular Weight Organic Acids.

    PubMed

    Wei, Wei; Wang, Yu; Wang, Zheng; Han, Ruiming; Li, Shiyin; Wei, Zhenggui; Zhang, Yong

    2016-01-01

    Understanding the stability of chloropyromorphite (CPY) is of considerable benefit for improving risk assessment and remediation strategies in contaminated water and soil. The stability of CPY in the rhizosphere of phosphorus-deficient ryegrass was evaluated to elucidate the role of root-secreted low molecular weight organic acids (LMWOAs) on the dissolution of CPY. Results showed that CPY treatments significantly reduced the ryegrass biomass and rhizosphere pH. The presence of calcium nitrate extractable lead (Pb) and phosphorus (P) suggested that CPY in the rhizosphere could be bioavailable, because P and Pb uptake by ryegrass potentially provided a significant concentration gradient that would promote CPY dissolution. Pb accumulation and translocation in ryegrass was found to be significantly higher in P-sufficient conditions than in P-deficient conditions. CPY treatments significantly enhanced root exudation of LMWOAs irrigated with P-nutrient solution or P-free nutrient solution. Oxalic acid was the dominant species in root-secreted LMWOAs of ryegrass under P-free nutrient solution treatments, suggesting that root-secreted oxalic acid may be the driving force of root-induced dissolution of CPY. Hence, our work, provides clarifying hints on the role of LMWOAs in controlling the stability of CPY in the rhizosphere. PMID:27494023

  3. In situ forming hydrogels composed of oxidized high molecular weight hyaluronic acid and gelatin for nucleus pulposus regeneration.

    PubMed

    Chen, Yu-Chun; Su, Wen-Yu; Yang, Shu-Hua; Gefen, Amit; Lin, Feng-Huei

    2013-02-01

    Encapsulation of nucleus pulposus (NP) cells within in situ forming hydrogels is a novel biological treatment for early stage intervertebral disc degeneration. The procedure aims to prolong the life of the degenerating discs and to regenerate damaged tissue. In this study we developed an injectable oxidized hyaluronic acid-gelatin-adipic acid dihydrazide (oxi-HAG-ADH) hydrogel. High molecular weight (1900 kDa) hyaluronic acid was crosslinked with various concentrations of gelatin to synthesize the hydrogels and their viscoelastic properties were analyzed. Interactions between the hydrogels, NP cells, and the extracellular matrix (ECM) were also evaluated, as were the effects of the hydrogels on NP cell gene expression. The hydrogels possess several clinical advantages, including sterilizability, low viscosity for injection, and ease of use. The viscoelastic properties of the hydrogels were similar to native tissue, as reflected in the complex shear modulus (∼11-14 kPa for hydrogels, 11.3 kPa for native NP). Cultured NP cells not only attached to the hydrogels but also survived, proliferated, and maintained their round morphology. Importantly, we found that hydrogels increased NP cell expression of several crucial ECM-related genes, such as COL2A1, AGN, SOX-9, and HIF-1A. PMID:23041783

  4. Carbon isotope composition of low molecular weight hydrocarbons and monocarboxylic acids from Murchison meteorite

    NASA Astrophysics Data System (ADS)

    Yuen, G.; Blair, N.; Des Marais, D. J.; Chang, S.

    1984-01-01

    Carbon isotopic compositions have been measured for individual hydrocarbons and monocarboxylic acids from the Murchison meteorite, a C2 carbonaceous chondrite which fell in Australia in 1969. With few exceptions, notably benzene, the volatile products are substantially isotopically heavier than their terrestrial counterparts, signifying their extraterrestrial origin. For both classes of compounds, the ratio of C-13 to C-12 decreases with increasing carbon number in a roughly parallel manner, and each carboxylic acid exhibits a higher isotopic ratio than the hydrocarbon containing the same number of carbon atoms. These trends are consistent with the kinetically controlled synthesis of higher homologues from lower ones. The results suggest the possibility that the production mechanisms for hydrocarbons and carboxylic acids may be similar, and impose constraints on the identity of the reactant species.

  5. Understanding the effect low molecular weight organic acids on the desorption and availability of soil phosphorus

    NASA Astrophysics Data System (ADS)

    Blackburn, Daniel; Zhang, Hao; Stutter, Marc; Giles, Courtney; George, Timothy; Shand, Charles; Lumsdon, David; Cooper, Pat; Wendler, Renate; Brown, Lawrie; Blackwell, Martin; Darch, Tegan; Wearing, Catherine; Haygarth, Philip

    2016-04-01

    The mobility and resupply of inorganic phosphorus (P) from the soil solid phase after equilibration with increasing doses of citric acid (CA) and oxalic acid (OA) were studied in 2 soils with contrasting P status. The combined methods of diffusive gradients in thin films (DGT), diffusive equilibration in thin films (DET) and the DGT-induced fluxes in sediments model (DIFS) were used as tools to evaluate the changes in solid-to-solution interchange kinetics. A significant effect of CA and OA in soil solution P was observed only for doses over 1 mMol kg-1. Curiously, low organic acid doses (0.5-1 mMol kg-1) were associated with a steep increase in microbial biomass P, which was not seen for doses over 2 mMol kg-1. The trivalent CA was able to promote a higher increase in soil solution P than the bivalent OA for both soils. Organic phosphorus was only significantly mobilized by organic acids in the low P soil, possibly because in the high P soil these P forms were less labile than inorganic P. Both CA and OA promoted a decrease in the adsorbed-to-solution distribution coefficient, desorption rate constants and an increase in the response time of solution P equilibration. The extent of this effect was shown to be both soil specific and organic acid specific. Since both organic acids negatively affected the kinetics of P interchange between the soil matrix and the soil solution, their net effect on P bioavailability is expected to be much lower than the observed increase in solution concentration.

  6. Chitosan grafted low molecular weight polylactic acid for protein encapsulation and burst effect reduction.

    PubMed

    Di Martino, Antonio; Kucharczyk, Pavel; Zednik, Jiri; Sedlarik, Vladimir

    2015-12-30

    Chitosan and chitosan-grafted polylactic acid as a matrix for BSA encapsulation in a nanoparticle structure were prepared through a polyelectrolyte complexation method with dextran sulfate. Polylactic acid was synthetized via a polycondensation reaction using the non-metal-based initiator methanesulfonic acid and grafted to the chitosan backbone by a coupling reaction, with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide as the condensing agent. The effect of concentration of the polymer matrix utilized herein on particle diameter, ζ-potential, encapsulation efficiency, and the release kinetic of the model protein bovine serum albumin at differing pH levels was investigated. The influence of pH and ionic strength on the behavior of the nanoparticles prepared was also researched. Results showed that grafting polylactic acid to chitosan chains reduced the initial burst effect in the kinetics of BSA release from the structure of the nanoparticles. Furthermore, a rise in encapsulation efficiency of the bovine serum albumin and diminishment in nanoparticle diameter were observed due to chitosan modification. The results suggest that both polymers actually show appreciable encapsulation efficiency; and release rate of BSA. CS-g-PLA is more suitable than unmodified CS as a carrier for controlled protein delivery. PMID:26453778

  7. Chitosan grafted low molecular weight polylactic acid for protein encapsulation and burst effect reduction.

    PubMed

    Di Martino, Antonio; Kucharczyk, Pavel; Zednik, Jiri; Sedlarik, Vladimir

    2015-12-30

    Chitosan and chitosan-grafted polylactic acid as a matrix for BSA encapsulation in a nanoparticle structure were prepared through a polyelectrolyte complexation method with dextran sulfate. Polylactic acid was synthetized via a polycondensation reaction using the non-metal-based initiator methanesulfonic acid and grafted to the chitosan backbone by a coupling reaction, with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide as the condensing agent. The effect of concentration of the polymer matrix utilized herein on particle diameter, ζ-potential, encapsulation efficiency, and the release kinetic of the model protein bovine serum albumin at differing pH levels was investigated. The influence of pH and ionic strength on the behavior of the nanoparticles prepared was also researched. Results showed that grafting polylactic acid to chitosan chains reduced the initial burst effect in the kinetics of BSA release from the structure of the nanoparticles. Furthermore, a rise in encapsulation efficiency of the bovine serum albumin and diminishment in nanoparticle diameter were observed due to chitosan modification. The results suggest that both polymers actually show appreciable encapsulation efficiency; and release rate of BSA. CS-g-PLA is more suitable than unmodified CS as a carrier for controlled protein delivery.

  8. Molecular Weight and Molecular Weight Distributions in Synthetic Polymers.

    ERIC Educational Resources Information Center

    Ward, Thomas Carl

    1981-01-01

    Focuses on molecular weight and molecular weight distributions (MWD) and models for predicting MWD in a pedagogical way. In addition, instrumental methods used to characterize MWD are reviewed with emphasis on physical chemistry of each, including end-group determination, osmometry, light scattering, solution viscosity, fractionation, and…

  9. Polyacrylamide gel analysis of high molecular weight ribonucleic Acid from etiolated and green cucumber cotyledons.

    PubMed

    Vedel, F; D'Aoust, M J

    1970-07-01

    Cucumis sativus L. seeds and 5-day-old dark-grown cotyledons contain 25 and 18 S cytoplasmic ribosomal RNAs as main components. The major increase in nucleic acid content in both green and etiolated cotyledons occurs between days 5 and 7 of germination. This increase is characterized by an important synthesis of 23 and 16 S plastid (chloroplast and proplastid) ribosomal RNAs. Proplastid RNA synthesis appears to continue for a longer period in the dark-grown cotyledons, despite a total RNA content considerably less than in the light-grown cotyledons.The nonribosomal distribution of the chloroplast and proplastid ribosomal RNAs observed in all cases (after extraction and fractionation) results from the lability of the 23 S component. This degradation increases if the chloroplasts and proplastids are isolated prior to extraction of their nucleic acid.

  10. Rheological and molecular weight comparisons of approved hyaluronic acid products - preliminary standards for establishing class III medical device equivalence.

    PubMed

    Braithwaite, Gavin J C; Daley, Michael J; Toledo-Velasquez, David

    2016-01-01

    Hyaluronic acid of various molecular weights has been in use for the treatment of osteoarthritis knee pain for decades. Worldwide, these products are regulated as either as drugs or devices and in some countries as both. In the US, this class of products is regulated as Class III medical devices, which places specific regulatory requirements on developers of these materials under a Pre-Market Approval process, typically requiring data from prospective randomized controlled clinical studies. In 1984 pharmaceutical manufacturers became able to file an Abbreviated New Drug Application for approval of a generic drug, thus establishing standards for demonstrating equivalence to an existing chemical entity. Recently, the first biosimilar, or 'generic biologic', was approved. Biosimilars are biological products that are approved by the FDA because they are 'highly similar' to a reference product, and have been shown to have no clinically meaningful differences from the reference product. For devices, Class II medical devices have a pathway for declaring equivalence to an existing product by filing a 510 k application for FDA clearance. However, until recently no equivalent regulatory pathway was available to Class III devices. In this paper, we consider the critical mechanical performance parameters for intra-articular hyaluronic products to demonstrate indistinguishable characteristics. Analogous to the aforementioned pathways that allow for a demonstration of equivalence, we examine these parameters for an existing, marketed device and compare molecular weight and rheological properties of multiple batches of a similar product. We propose that this establishes a scientific rationale for establishing Class III medical device equivalence.

  11. The short-term effect of cadmium on low molecular weight organic acid and amino acid exudation from mangrove (Kandelia obovata (S., L.) Yong) roots.

    PubMed

    Xie, Xiangyu; Weiss, Dominik J; Weng, Bosen; Liu, Jingchun; Lu, Haoliang; Yan, Chongling

    2013-02-01

    The aim of this study was to evaluate short-term concentration and time effects of cadmium on Kandelia obovata (S., L.) Yong root exudation, thereby evaluating and predicting the ecophysiological effects of mangrove to heavy metals at the root level. Mature K. obovata propagules were cultivated in a sandy medium for 3 months, and then six concentrations of Cd (0, 2.5, 5, 10, 20, and 40 mg L(-1)) were applied. After exposure time of 24 h and 7 days, respectively, the root exudates of K. obovata were collected and low molecular weight organic acids (LMWOAs) and amino acids of which were analyzed. In addition, we measured glutathione, soluble protein content, and Cd concentration in the plant. We found 10 and 15 types of LMWOAs and amino acids in root exudates of K. obovata with total concentrations ranging from 29.54 to 43.08 mg g(-1) dry weight (DW) roots and from 737.35 to 1,452.46 ng g(-1) DW roots, respectively. Both of them varied in quality and quantity under different Cd treatment strengths and exposure times. Oxalic, acetic, L-malic, tartaric acid, tyrosine, methionine, cysteine, isoleucine, and arginine were dominant. Both LMWOAs and amino acids excreted from K. obovata roots play a key role in Cd toxicity resistance. The responsiveness of amino acids was less than that of LMWOAs. We suggest that the ecological effect of root-excreted free amino acids in the rhizosphere is mainly based on the role of nutrients, supplemented with detoxification to heavy metals. PMID:22729874

  12. Molecular weight distribution of soluble fiber fractions and short chain fatty acids in ileal digesta of growing pigs.

    PubMed

    Ivarsson, E; Andersson, R; Lindberg, J E

    2012-12-01

    The effect of dietary fiber source on molecular weight (MW) distribution of soluble fiber fractions and short chain fatty acids (SCFA) in ileal digesta of 7 post valve T-cecum (PVTC) cannulated growing pigs was studied. Pigs were fed semisynthetic diets with sugar beet (Beta vulgaris) pulp (SBP) or chicory (Cichorium intybus) forage (CFO) as fiber sources of which the soluble nonstarch polysaccharide (NSP) fraction originated mainly from pectin. Three MW intervals were selected-large MW (MWL): 10,000,000 to 1,000,000 g/mol, medium MW (MWM): 1,000,000 to 200,000 g/mol, and small MW (MWS): 200,000 to 10,000 g/mol-and the relative distribution (% of total) of molecules in each interval was calculated. The MWM fraction was higher (P < 0.05) in ileal digesta of pigs fed diet SBP and the MWS fraction was higher (P < 0.05) in ileal digesta of pigs fed diet CFO. The mole/100 mole of propionic acid (HPr) was higher (P < 0.010) in pigs fed diet SBP whereas pigs fed diet CFO had higher (P < 0.010) mole/100 mole of acetic acid (HAc). The proportion of the MWL and MWM fractions in ileal digesta were negatively correlated to HAc (r = -0.52, P = 0.05, and r = -0.62, P = 0.02, respectively). The proportion of MWM in ileal digesta was positively correlated to HPr (r = 0.83; P = 0.001) whereas MWS and HPr were negatively correlated (r = -0.76; P = 0.002). In conclusion, the bacterial degradation of the soluble NSP fraction is selective and MW distribution may explain differences in SCFA production.

  13. Lipoic acid modified low molecular weight polyethylenimine mediates nontoxic and highly potent in vitro gene transfection.

    PubMed

    Zheng, Meng; Zhong, Yinan; Meng, Fenghua; Peng, Rui; Zhong, Zhiyuan

    2011-12-01

    The clinical success of gene therapy intimately relies on the development of safe and efficient gene carrier systems. We found here that 1.8 kDa polyethylenimine (PEI) following hydrophobic modification with lipoic acid (LA) mediated nontoxic and highly potent in vitro gene transfection in both HeLa and 293T cells. 1.8 kDa PEI-LA conjugates were prepared with controlled degree of substitution (DS) by coupling LA to PEI using carbodiimide chemistry. Gel electrophoresis measurements showed that the DNA binding ability of 1.8 kDa PEI was impaired by lipoylation, in which an N/P ratio of 2/1 and 4-6/1 was required for 1.8 kDa PEI and 1.8 kDa PEI-LA conjugates, respectively, to completely inhibit DNA migration. Interestingly, dynamic light scattering measurements (DLS) revealed that PEI-LA conjugates condensed DNA into much smaller sizes (183-84 nm) than unmodified 1.8 kDa PEI (444-139 nm) at N/P ratios ranging from 20/1 to 60/1. These polyplexes revealed similar surface charges of ca. +22 to +30 mV. 1.8 kDa PEI-LA(2) polyplexes formed at an N/P ratio of 10/1 were stable against exchange with 12-fold excess of negatively charged dextran sodium sulfate (DSS) relative to DNA phosphate groups while 1.8 kDa PEI controls dissociated at 6-fold excess of DSS, indicating that lipoylation of 1.8 kDa PEI resulted in stronger binding with DNA. Importantly, DNA was released from 1.8 kDa PEI-LA(2) polyplexes upon addition of 10 mM dithiothreitol (DTT). Reduction-triggered unpacking of 1.8 kDa PEI-LA(2) polyplexes was also confirmed by DLS. MTT assays demonstrated that all PEI-LA conjugates and polyplexes were essentially nontoxic to HeLa and 293T cells up to a tested concentration of 50 μg/mL and an N/P ratio of 80/1, respectively. The in vitro gene transfection studies in HeLa and 293T cells showed that lipoylation of 1.8 kDa PEI markedly boosted its transfection activity. For example, 1.8 kDa PEI-LA(2) polyplexes displayed 400-fold and 500-fold higher levels of gene expression

  14. Highly hydrophilic ultra-high molecular weight polyethylene powder and film prepared by radiation grafting of acrylic acid

    NASA Astrophysics Data System (ADS)

    Wang, Honglong.; Xu, Lu.; Li, Rong.; Pang, Lijuan.; Hu, Jiangtao.; Wang, Mouhua.; Wu, Guozhong.

    2016-09-01

    The surface properties of ultra-high molecular weight polyethylene (UHMWPE) are very important for its use in engineering or composites. In this work, hydrophilic UHMWPE powder and film were prepared by γ-ray pre-irradiation grafting of acrylic acid (AA) and further neutralization with sodium hydroxide solution. Variations in the chemical structure, grafting yield and hydrophilicity were investigated and compared. FT-IR and XPS analysis results showed that AA was successfully grafted onto UHMWPE powder and film; the powder was more suitable for the grafting reaction in 1 wt% AA solution than the film. Given a dose of 300 kGy, the grafting yield of AA was ∼5.7% for the powder but ∼0.8% for the film under identical conditions. Radiation grafting of a small amount of AA significantly improved the hydrophilicity of UHMWPE. The water contact angle of the UHMWPE-g-PAA powder with a grafting yield of AA at ∼5.7% decreased from 110.2° to 68.2°. Moreover, the grafting powder (UHMWPE-g-PAA) exhibited good dispersion ability in water.

  15. Effect of organic molecular weight on mineralization and energy consumption of humic acid by H2O2/UV oxidation.

    PubMed

    Yen, Hsing Yuan; Kang, Shyh Fang

    2016-09-01

    In this study, the effect of molecular weights (MWs) on mineralization, energy consumption, kinetic reaction, and trihalomethane formation potential (THMFP) of humic acid was evaluated by the process of H2O2/UV oxidation. Three ranges of MWs of 100 k-10 kDa (sample A), 10 k-1 kDa (sample B), and less than 1 kDa (sample C) were investigated. The results showed that the reaction constant k increased with either increased UV intensity or increased H2O2 dose; the order of k was kA > kB > kC, for all UV intensities from 16 to 64 W and H2O2 dose from 25 to 100 mg L(-1). In terms of EEO and EEM, the energy consumption decreased as the H2O2 dose increased with the descending order of sample C > sample B > sample A. The three samples had an initial dissolved organic carbon (DOC) of 20 mg L(-1) with the related values of THMFP of 325, 359, and 468 μg L(-1) for samples A, B, and C, respectively. After H2O2/UV oxidation, the combination of a higher UV power with a shorter time was a better treatment condition for samples A and B as residual DOC and THMFP were smaller.

  16. Phenylboronic Acid Appended Pyrene-Based Low-Molecular-Weight Injectable Hydrogel: Glucose-Stimulated Insulin Release.

    PubMed

    Mandal, Deep; Mandal, Subhra Kanti; Ghosh, Moumita; Das, Prasanta Kumar

    2015-08-17

    A pyrene-containing phenylboronic acid (PBA) functionalized low-molecular-weight hydrogelator was synthesized with the aim to develop glucose-sensitive insulin release. The gelator showed the solvent imbibing ability in aqueous buffer solutions of pH values, ranging from 8-12, whereas the sodium salt of the gelator formed a hydrogel at physiological pH 7.4 with a minimum gelation concentration (MGC) of 5 mg mL(-1) . The aggregation behavior of this thermoreversible hydrogel was studied by using microscopic and spectroscopic techniques, including transmission electron microscopy, FTIR, UV/Vis, luminescence, and CD spectroscopy. These investigations revealed that hydrogen bonding, π-π stacking, and van der Waals interactions are the key factors for the self-assembled gelation. The diol-sensitive PBA part and the pyrene unit in the gelator were judiciously used in fluorimetric sensing of minute amounts of glucose at physiological pH. The morphological change of the gel due to addition of glucose was investigated by scanning electron microscopy, which denoted the glucose-responsive swelling of the hydrogel. A rheological study indicated the loss of the rigidity of the native gel in the presence of glucose. Hence, the glucose-induced swelling of the hydrogel was exploited in the controlled release of insulin from the hydrogel. The insulin-loaded hydrogel showed thixotropic self-recovery property, which hoisted it as an injectable soft composite. Encouragingly, the gelator was found to be compatible with HeLa cells.

  17. Evaluation of the Oral Bioavailability of Low Molecular Weight Heparin Formulated With Glycyrrhetinic Acid as Permeation Enhancer.

    PubMed

    Motlekar, Nusrat A; Srivenugopal, Kalkunte S; Wachtel, Mitchell S; Youan, Bi-Botti C

    2006-02-01

    Low molecular weight heparin (LMWH) is the agent of choice for anticoagulant therapy and prophylaxis of thrombosis and coronary syndromes. However, its therapeutic use is limited due to poor oral bioavailability. The aim of this study was to investigate the oral delivery of LMWH, ardeparin formulated with 18-beta glycyrrhetinic acid (GA), as an alternative to currently used subcutaneous (sc) delivery. Drug transport through Caco-2 cell monolayers was monitored in the presence and absence of GA by scintillation counting and transepithelial electrical resistance. Regional permeability studies using rat intestine were performed using a modified Ussing chamber. Cell viability in the presence of various concentrations of enhancer was determined by MTT assay. The absorption of ardeparin after oral administration in rats was measured by an anti-factor Xa assay. Furthermore, the eventual mucosal epithelial damage was histologically evaluated. Higher ardeparin permeability (~7-fold) compared to control was observed in the presence of 0.02 % GA. Regional permeability studies indicated predominant absorption in the duodenal segment. Cell viability studies showed no significant cytotoxicity below 0.01 % GA. Ardeparin oral bioavailability was significantly increased (F(relative)/(S.C). = 13.3%) without causing any damage to the intestinal tissues. GA enhanced the oral absorption of ardeparin both in vitro and in vivo. The oral formulation of ardeparin with GA could be absorbed in the intestine. These results suggest that GA may be used as an absorption enhancer for the oral delivery of LMWH. PMID:17710191

  18. LMWOA (low molecular weight organic acid) exudation by salt marsh plants: Natural variation and response to Cu contamination

    NASA Astrophysics Data System (ADS)

    Mucha, Ana P.; Almeida, C. Marisa R.; Bordalo, Adriano A.; Vasconcelos, M. Teresa S. D.

    2010-06-01

    This work aimed to evaluate, in vitro, the capability of roots of two salt marsh plants to release low molecular weight organic acids (LMWOAs) and to ascertain whether Cu contamination would stimulate or not organic acids exudation. The sea rush Juncus maritimus and the sea-club rush Scirpus maritimus, both from the lower Douro river estuary (NW Portugal), were used. Plants were collected seasonally, four times a year in 2004, during low tide. After sampling, plant roots were washed for removal of adherent particles and immersed for 2 h in a solution that matched salinity (3) and pH (7.5) of the pore water from the same location to obtain plant exudates. In one of the seasons, similar experiments were carried out but spiking the solution with different amounts of Cu in order to embrace the range between 0 and 1600 nM. In the final solutions as well as in sediment pore water LMWOAs were determined by high performance liquid chromatography. Plants were able to release, in a short period of time, relatively high amounts of LMWOAs (oxalate, citrate, malate, malonate, and succinate). In the sediment pore water oxalate, succinate and acetate were also detected. Therefore, plant roots probably contributed to the presence of some of these organic compounds in pore water. Exudation differed between the plant species and also showed some seasonally variation, particularly for S. maritimus. The release of oxalate by J. maritimus increased with Cu increase in the media. However, exudation of the other LMWOAs did not seem to be stimulated by Cu contamination in the media. This fact is compatible with the existence of alternative internal mechanisms for Cu detoxification, as denoted by the fact that in media contaminated with Cu both plant species accumulated relatively high amounts (29-83%) of the initially dissolved Cu. This study expands our knowledge on the contribution of globally dominant salt marsh plants to the release of LMWOAs into the environment.

  19. A review of environmental characteristics and effects of low-molecular weight organic acids in the surface ecosystem.

    PubMed

    Xiao, Min; Wu, Fengchang

    2014-05-01

    Low molecular weight organic acids (LMWOAs) are prevalent on the earth's surface. They are vital intermediate products during metabolic pathways of organic matter and participate in the tricarboxylic acid cycle during life activities. Photochemical reactions are pivotal for LMWOAs' origination and play a large role in determining their diversity and their ultimate fate. Within the long time that organic matter is preserved in sediments, it can be decomposed and converted to release organic and inorganic pollutants as well as C, N, and P nutrients, which are of potential ecological risk in causing secondary pollution to lake water. The sediment pool is a comprehensive and complex compartment closely associated with overlying water by various biochemical processes, during which LMWOAs play critical roles to transport and transform elements. This article elucidates geochemical behaviors of LMWOAs in the surface environment in details, taking natural water, soil, and aerosol as examples, focusing on reviewing research developments on sources and characteristics, migration and mineralization of LMWOAs and relevant environmental effects. Simultaneously, this review article depicts the categories and contents of LMWOAs or their contribution to DOC in environmental media, and evaluates their importance during organic matter early diagenesis. Through concluding and discussing the conversion mechanisms and influencing factors, the next research orientations on LMWOAs in lake ecosystems are determined, mainly concerning relationships with hydrochemical parameters and microorganisms, and interactions with pollutants. This will enrich the knowledge on organic matter degradation and related environmental effects, and help reconstruct a theoretical framework for organic compound succession and influencing factors, providing basic data for lake eutrophication and ecological risk assessment, conducive to better control over water pollution and proper management of water quality.

  20. Effects of cadmium amendments on low-molecular-weight organic acid exudates in rhizosphere soils of tobacco and sunflower.

    PubMed

    Chiang, Po-Neng; Wang, Ming Kuang; Chiu, Chih Yu; Chou, Shu-Yen

    2006-10-01

    To recognize physiological response of plants to cadmium (Cd) toxicity in rhizosphere of plants, the pot experiments were employed to investigate how low-molecular-weight organic acids (LMWOAs) were exudated from tobacco and sunflower roots of Cd-amended soils. The aims of this study were to assess the effect of LMWOAs on uptake of Cd by tobacco and sunflower under pot experiments, thus comparing the ability of tobacco and sunflower for phytoremediation. Surface soils (0-20 cm) were collected from Taichung Experiment Station (TC) (silty loam). Cadmium chloride (CdCl(2)) was amended into TC soil, giving Cd concentrations of 1, 5, 10 mg kg(-1) soil. Soils with different concentrations of Cd were put into 12 cm (i.d.) pots for incubation, and then 2-week-old tobacco and sunflower seedlings were transplanted into the pots. Tobacco and sunflower were grown in greenhouse for 50 days, respectively. The rhizosphere and bulk soils, and fresh plant tissues were collected after harvest. The Cd concentrations in the plant and transfer factor values in the sunflower were higher than that in the tobacco. No LMWOAs were detected by gas chromatograph in bulk soils, and low amounts of LMWOAs were found in uncontaminated rhizosphere soils. Acetic, lactic, glycolic, malic, maleic, and succinic acids were found in the tobacco and sunflower rhizosphere soils. Concentrations of LMWOAs increased with increasing amendment of Cd concentrations in tobacco and sunflower rhizosphere soils. Correlation coefficient (r) of concentrations of Cd amendment versus LMWOAs exudates of tobacco and sunflower were 0.85 and 0.98, respectively. These results suggest that the different levels of LMWOAs present in the rhizosphere soil play an important role in the solubilization of Cd that bound with soil particle into soil solution and then uptake by plants.

  1. Apparatus for molecular weight separation

    DOEpatents

    Smith, Richard D.; Liu, Chuanliang

    2001-01-01

    The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations (0-2.5 mM NH4OAc) of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, (4) conducting a two-stage separation or (5) any combination of (1), (2), (3) and (4).

  2. Comparative studies on chitosan and polylactic-co-glycolic acid incorporated nanoparticles of low molecular weight heparin.

    PubMed

    Yang, Tianzhi; Nyiawung, Divine; Silber, Alexandra; Hao, Jiukuan; Lai, Leanne; Bai, Shuhua

    2012-12-01

    This study was performed to test the feasibility of chitosan and polylactic-co-glycolic acid (PLGA) incorporated nanoparticles as sustained-release carriers for the delivery of negatively charged low molecular weight heparin (LMWH). Fourier transform infrared (FTIR) spectrometry was used to evaluate the interactions between chitosan and LMWH. The shifts, intensity, and broadening of the characteristic peaks for the functional groups in the FTIR spectra indicated that strong interactions occur between the positively charged chitosans and the negatively charged LMWHs. Three types of LMWH nanoparticles (NP-1, NP-2, and NP-3) were prepared using chitosan with or without PLGA: NP-1 nanoparticles were formed by polyelectrolyte complexation after single mixing, NP-2 nanoparticles were prepared by polyelectrolyte complexation after single emulsion-diffusion-evaporation, and NP-3 nanoparticles were optimized by double emulsion-diffusion-evaporation. NP-3 nanoparticles of LMWH prepared by the emulsion-diffusion-evaporation method showed significant differences in particle morphology, size, zeta potential, and drug release profile compared to NP-1 nanoparticles formed by polyelectrolyte complexation. Another ionic complex of LMWH with chitosan-incorporated PLGA nanoparticles (NP-2) showed lower drug entrapment efficiency than that of NP-1 and NP-3. The drug release rate of NP-3 was slower than the release rates of NP-1 and NP-2, although particle morphology of NP-3 was similar to that of NP-2. Cell viability was not adversely affected when cells were treated with all three types of nanoparticles. The data presented in this study demonstrate that nanoparticles formulated with chitosan-PLGA could be a safe sustained-release carrier for the delivery of LMWH.

  3. Do soil Fe transformation and secretion of low-molecular-weight organic acids affect the availability of Cd to rice?

    PubMed

    Chen, Xue; Yang, Yazhou; Liu, Danqing; Zhang, Chunhua; Ge, Ying

    2015-12-01

    The bioavailability of cadmium (Cd) to rice may be complicated by chemical and biological factors in the rhizosphere. The aim of this work is to investigate how soil iron (Fe) redox transformations and low-molecular-weight organic acid (LMWOA) exudation from root affect Cd accumulation in rice. Two soils (a paddy soil and a saline soil) with different physicochemical properties were used in this study. Soil redox conditions were changed by flooding and addition of organic matter (OM). Two days after the soil treatments, rice seedlings were transplanted in a vermiculite-soil system and grown for 10 days. We measured pH and Eh, LMWOA, Fe and Cd contents in rice, and their fractions in the soils and vermiculite. Cadmium accumulation in rice declined in both soils upon the flooding and OM treatment. Iron dissolution in the paddy soil and its deposition in the rhizosphere significantly increased upon the OM addition, but the concentration of Fe plaque on the rice root significantly declined. Conversely, although Fe transformed into less active fractions in the saline soil, Fe accumulation on the surface and in the tissue of root was considerably enhanced. The secretion of LMWOA was remarkably induced when the OM was amended in the saline soil, but the same effect was not observed in the paddy soil. Reduction of Cd uptake by rice could be attributed to different factors in the two soils. For the paddy soil, the lowered Cd bioavailability was likely due to the competition of Fe and Cd for the binding sites on the vermiculite surface. For the saline soil, however, rice responded to the low Fe mobility through more LMWOA exudation and Fe plaque formation, and their increases could explain the decrease of rice Cd.

  4. Do soil Fe transformation and secretion of low-molecular-weight organic acids affect the availability of Cd to rice?

    PubMed

    Chen, Xue; Yang, Yazhou; Liu, Danqing; Zhang, Chunhua; Ge, Ying

    2015-12-01

    The bioavailability of cadmium (Cd) to rice may be complicated by chemical and biological factors in the rhizosphere. The aim of this work is to investigate how soil iron (Fe) redox transformations and low-molecular-weight organic acid (LMWOA) exudation from root affect Cd accumulation in rice. Two soils (a paddy soil and a saline soil) with different physicochemical properties were used in this study. Soil redox conditions were changed by flooding and addition of organic matter (OM). Two days after the soil treatments, rice seedlings were transplanted in a vermiculite-soil system and grown for 10 days. We measured pH and Eh, LMWOA, Fe and Cd contents in rice, and their fractions in the soils and vermiculite. Cadmium accumulation in rice declined in both soils upon the flooding and OM treatment. Iron dissolution in the paddy soil and its deposition in the rhizosphere significantly increased upon the OM addition, but the concentration of Fe plaque on the rice root significantly declined. Conversely, although Fe transformed into less active fractions in the saline soil, Fe accumulation on the surface and in the tissue of root was considerably enhanced. The secretion of LMWOA was remarkably induced when the OM was amended in the saline soil, but the same effect was not observed in the paddy soil. Reduction of Cd uptake by rice could be attributed to different factors in the two soils. For the paddy soil, the lowered Cd bioavailability was likely due to the competition of Fe and Cd for the binding sites on the vermiculite surface. For the saline soil, however, rice responded to the low Fe mobility through more LMWOA exudation and Fe plaque formation, and their increases could explain the decrease of rice Cd. PMID:26260840

  5. Effect of a high molecular weight hyaluronic acid (HA) preparation on the stimulation of polymorphonulcear leukocytes (PMNL)

    SciTech Connect

    McNeil, J.; Chow, D.C.; Skosey, J.L.

    1986-03-01

    During the process of joint inflammation PMNL are attracted into the joint space by chemotactic agents and are stimulated by immune complexes, particular matter (eg, crystals, cartilage debris) and other phlogistic agents. This process occurs in an environment rich in HA. The authors have examined the effect of high molecular weight HA. They have examined the effect of high molecular weight HA upon PMNL stimulation. PMNL were isolated from human blood and stimulated with either opsonized zymosan or formyl-methionyl-leucyl-phenylalanine (fmlp). The authors assessed stimulation by measuring the ability of cell supernatants to promote the release of /sup 35/S from chips of rabbit articular cartilage labeled in vivo, and the enhancement of oxidation of (1-/sup 14/C)glucose to /sup 14/CO/sub 2/. Stimulation of cells with zym in the presence of HA, 0.125-2.5 mg/ml, resulted in enhanced /sup 35/S release (33-59% over zym alone) and /sup 14/CO/sub 2/ production (0.5-64%). However, HA failed to enhance responses when fmlp (+cytochalasin B) was used as the stimulus. It has been demonstrated that high molecular weight HA inhibits phagocytosis of both latex and aggregated IgG. In our studies, it is likely that HA interference with ingestion of zym leads to frustrated phagocytosis and enhancement of PMNL responses. Similar modification of responses of inflammatory mediator cells could occur in inflamed joints.

  6. Effects of low molecular-weight organic acids and dehydrogenase activity in rhizosphere sediments of mangrove plants on phytoremediation of polycyclic aromatic hydrocarbons.

    PubMed

    Wang, Yuanyuan; Fang, Ling; Lin, Li; Luan, Tiangang; Tam, Nora F Y

    2014-03-01

    This work evaluated the roles of the low-molecular-weight organic acids (LMWOAs) from root exudates and the dehydrogenase activity in the rhizosphere sediments of three mangrove plant species on the removal of mixed PAHs. The results showed that the concentrations of LMWOAs and dehydrogenase activity changed species-specifically with the levels of PAH contamination. In all plant species, the concentration of citric acid was the highest, followed by succinic acid. For these acids, succinic acid was positively related to the removal of all the PAHs except Chr. Positive correlations were also found between the removal percentages of 4-and 5-ring PAHs and all LMWOAs, except citric acid. LMWOAs enhanced dehydrogenase activity, which positively related to PAH removal percentages. These findings suggested that LMWOAs and dehydrogenase activity promoted the removal of PAHs. Among three mangrove plants, Bruguiera gymnorrhiza, the plant with the highest root biomass, dehydrogenase activity and concentrations of LMWOAs, was most efficient in removing PAHs. PMID:24287262

  7. Effects of low molecular-weight organic acids and dehydrogenase activity in rhizosphere sediments of mangrove plants on phytoremediation of polycyclic aromatic hydrocarbons.

    PubMed

    Wang, Yuanyuan; Fang, Ling; Lin, Li; Luan, Tiangang; Tam, Nora F Y

    2014-03-01

    This work evaluated the roles of the low-molecular-weight organic acids (LMWOAs) from root exudates and the dehydrogenase activity in the rhizosphere sediments of three mangrove plant species on the removal of mixed PAHs. The results showed that the concentrations of LMWOAs and dehydrogenase activity changed species-specifically with the levels of PAH contamination. In all plant species, the concentration of citric acid was the highest, followed by succinic acid. For these acids, succinic acid was positively related to the removal of all the PAHs except Chr. Positive correlations were also found between the removal percentages of 4-and 5-ring PAHs and all LMWOAs, except citric acid. LMWOAs enhanced dehydrogenase activity, which positively related to PAH removal percentages. These findings suggested that LMWOAs and dehydrogenase activity promoted the removal of PAHs. Among three mangrove plants, Bruguiera gymnorrhiza, the plant with the highest root biomass, dehydrogenase activity and concentrations of LMWOAs, was most efficient in removing PAHs.

  8. Effects of certain atmospheric pollutants (SO2, NO2 and CO) on the soluble amino acids, molecular weight and antigenicity of some airborne pollen grains.

    PubMed

    Ruffin, J; Liu, M Y; Sessoms, R; Banerjee, S; Banerjee, U C

    1986-01-01

    The pure pollen grains of Red Oak (Quercus rubra), Meadow Fescue (Festuca elatior) and Chinese Elm (Ulmas pumila) were exposed to carbon monoxide (CO), sulphur dioxide (SO2) and nitrogen dioxide (NO2). After exposure, the soluble free amino acids were determined from the extracts using two-dimensional thin layer chromatography, and the molecular weight of the extracts were determined by SDS-gel electrophoresis (PAGE). The results indicated that after contamination, both the amino acids and molecular weight profiles were changed. In addition, the double immunodiffusion method was used against rabbit-antisera to determine the antigenicity of contaminated and non-contaminated pollen grain extracts. The results also showed that there were antigenic changes after contamination.

  9. Adhesion, phenotypic expression, and biosynthetic capacity of corneal keratocytes on surfaces coated with hyaluronic acid of different molecular weights.

    PubMed

    Lai, Jui-Yang; Tu, I-Hao

    2012-03-01

    In ophthalmology, hyaluronic acid (HA) is an important extracellular matrix (ECM) component and is appropriate for use in generating a microenvironment for cell cultivation. The aim of this work was to evaluate the rabbit corneal keratocyte (RCK) growth in response to HA coatings under serum-free conditions. After modification with HA of varying molecular weights (MWs: 35-1500kDa), the surfaces were characterized by atomic force microscopy and contact angle measurements, and were used for cell culture studies. Our data indicated that the substrates coated with higher negatively charged HA become rougher and are more hydrophilic, resulting in the decrease of cell adhesion and cell-matrix interaction. This early cellular event was likely responsible for the determination of keratocyte configuration. Additionally, for the growth of RCKs on dry HA coatings with surface roughness of 1.1-1.7 nm, a strong cell-cell interaction was observed, which may facilitate the formation of multicellular spheroid aggregates and maintenance of mitotically quiescent state. At each culture time point from 1 to 5 days, a better biosynthetic capacity associated with a higher prevalence of elevated ECM production was found for the cells in a spherical configuration. Irrespective of polysaccharide MW of surface coatings, the RCKs presented good viability without hypoxia-induced death. As compared with a monolayer of adherent keratocytes on tissue culture polystyrene plates and low MW HA-modified samples, the cell spheroids (76-110 μm in diameter) showed significantly higher expressions of keratocan and lumican and lower expressions of biglycan, similar to those of keratocytes in vivo. Moreover, the expression levels of corneal crystallin aldehyde dehydrogenase (7-9-fold increase) and nestin (10-16-fold increase) were greater in larger-sized spheroids, indicating higher ability to maintain cellular transparency and self-renewal potential. It is concluded that the cultured RCKs on surfaces

  10. Effect of low-molecular-weight organic acids on photo-degradation of phenanthrene catalyzed by Fe(III)-smectite under visible light.

    PubMed

    Jia, Hanzhong; Chen, Hongxia; Nulaji, Gulimire; Li, Xiyou; Wang, Chuanyi

    2015-11-01

    The photolysis of polycyclic aromatic hydrocarbons (PAHs) is potentially an important process for its transformation and fate on contaminated soil surfaces. In this study, phenanthrene is employed as a model to explore PAH photodegradation with the assistance of Fe(III)-smectite under visible-light while focusing on roles played by five low-molecular-weight organic acids (LMWOAs), i.e., malic acid, oxalic acid, citric acid, ethylenediaminetetraacetic acid (EDTA), and nitrilotriacetic acid. Our results show that oxalic acid is most effective in promoting the photodegradation of phenanthrene, while only a slight increase in the rate of phenanthrene photodegradation is observed in the presence of malic acid. Electron paramagnetic resonance experiments confirm the formation of CO2(-) radicals in the presence of malic and oxalic acid, which provides strong evidence for generating OH and subsequent photoreaction pathways. The presence of EDTA or nitrilotriacetic acid significantly inhibits both Fe(II) formation and phenanthrene photodegradation because these organic anions tend to chelate with Fe(III), leading to decreases in the electron-accepting potential of Fe(III)-smectite and a weakened interaction between phenanthrene and Fe(III)-smectite. These observations provide valuable insights into the transformation and fate of PAHs in the natural soil environment and demonstrate the potential for using some LMWOAs as additives for the remediation of contaminated soil. PMID:26091867

  11. Effect of low-molecular-weight organic acids on photo-degradation of phenanthrene catalyzed by Fe(III)-smectite under visible light.

    PubMed

    Jia, Hanzhong; Chen, Hongxia; Nulaji, Gulimire; Li, Xiyou; Wang, Chuanyi

    2015-11-01

    The photolysis of polycyclic aromatic hydrocarbons (PAHs) is potentially an important process for its transformation and fate on contaminated soil surfaces. In this study, phenanthrene is employed as a model to explore PAH photodegradation with the assistance of Fe(III)-smectite under visible-light while focusing on roles played by five low-molecular-weight organic acids (LMWOAs), i.e., malic acid, oxalic acid, citric acid, ethylenediaminetetraacetic acid (EDTA), and nitrilotriacetic acid. Our results show that oxalic acid is most effective in promoting the photodegradation of phenanthrene, while only a slight increase in the rate of phenanthrene photodegradation is observed in the presence of malic acid. Electron paramagnetic resonance experiments confirm the formation of CO2(-) radicals in the presence of malic and oxalic acid, which provides strong evidence for generating OH and subsequent photoreaction pathways. The presence of EDTA or nitrilotriacetic acid significantly inhibits both Fe(II) formation and phenanthrene photodegradation because these organic anions tend to chelate with Fe(III), leading to decreases in the electron-accepting potential of Fe(III)-smectite and a weakened interaction between phenanthrene and Fe(III)-smectite. These observations provide valuable insights into the transformation and fate of PAHs in the natural soil environment and demonstrate the potential for using some LMWOAs as additives for the remediation of contaminated soil.

  12. Efficacy and Safety of a Low Molecular Weight Hyaluronic Acid Topical Gel in the Treatment of Facial Seborrheic Dermatitis Final Report

    PubMed Central

    Rowland Powell, Callie

    2014-01-01

    Objective: Hyaluronic acid sodium salt gel 0.2% is a topical device effective in reducing skin inflammation. Facial seborrheic dermatitis, characterized by erythema and or flaking/scaling in areas of high sebaceous activity, affects up to five percent of the United States population. Despite ongoing study, the cause of the condition is yet unknown, but has been associated with yeast colonization and resultant immune derived inflammation. First-line management typically is with keratolytics, topical steroids, and topical antifungals as well as the targeted immunosuppressant agents pimecrolimus and tacrolimus. The objective of this study was to evaluate the efficacy and safety of a novel topical antiinflammatory containing low molecular weight hyaluronic acid. Design and setting: Prospective, observational, non-blinded safety and efficacy study in an outpatient setting. Participants: Individuals 18 to 75 years of age with facial seborrheic dermatitis. Measurements: Outcome measures included scale, erythema, pruritus, and the provider global assessment, all measured on a five-point scale. Subjects were assessed at baseline, Week 2, Week 4, and Week 8. Results: Final data with 13 of 17 subjects are presented. Hyaluronic acid sodium salt gel 0.2% was shown through visual grading assessments to improve the provider global assessment by 65.48 percent from baseline to Week 4. Reductions in scale, erythema, and pruritus were 76.9, 64.3, and 50 percent, respectively, at Week 4. At Week 8, the provider global assessment was improved from baseline in 92.3 percent of subjects. Conclusion: Treatment with topical low molecular weight hyaluronic acid resulted in improvement in the measured endpoints. Final data reveal continued improvement from that seen in the interim data shown previously. Topical low molecular weight hyaluronic acid is another option that may be considered for the treatment of facial seborrheic dermatitis in the adult population. Compliance and tolerance were

  13. Contributions of low molecular weight carboxylic acids to aerosols and wet deposition in a natural subtropical broad-leaved forest environment

    NASA Astrophysics Data System (ADS)

    Tsai, Ying I.; Kuo, Su-Ching

    2013-12-01

    The carboxylic acid component of autumn aerosol and wet deposition (fog water and rainwater) in a broad-leaved forest in central Taiwan was investigated. High levels of low molecular weight carboxylic acids (LMWCAs) were noted in all deposition types. Acetic acid, oxalic acid and formic acid were the most prevalent carboxylic acids, together accounting for 72.2% (fog water), 86.7% (rain water), 77.2% (PM2.5) and 88.3% (PM2.5-10) of total carboxylic acid. The forest fog water contained 2453.9 ± 1030.5 ng mL-1 of carboxylic acid, 2.71 times more than was contained in forest rainwater. In PM, most carboxylic acid existed in the fine PM2.5 aerosol (576.6 ± 254.1 ng m-3 or 6.28 times more than was contained in PM2.5-10. Most carboxylic acids in PM had higher concentrations during the day. Pyruvic acid concentration was higher during the night (2.97 times), however, owing to its rapid photodegradation during the day. Citric acid accounted for 9.1% of the total carboxylic acid in fog water compared with just 1.8% in rainwater, confirming its origin from emissions from leaves. Raman spectroscopy was used to observe the photochemical conversion of citric acid into intermediate products and this observation confirmed that the carboxylic acids identified in the forest dry and wet depositions originated directly from biological emissions in the forest environment.

  14. [Effects of Low-Molecular-Weight Organic Acids on the Speciation of Pb in Purple Soil and Soil Solution].

    PubMed

    Liu, Jiang; Jiang, Tao; Huang, Rong; Zhang, Jin-zhong; Chen, Hong

    2016-04-15

    Lead (Pb) in purple soil was selected as the research target, using one-step extraction method with 0.01 mol · L⁻¹ sodium nitrate as the background electrolyte to study the release effect of citric acid (CA), tartaric acid (TA) and acetic acid (AC) with different concentrations. Sequential extraction and geochemical model (Visual Minteq v3.0) were applied to analyze and predict the speciation of Pb in soil solid phase and soil solution phase. Then the ebvironmental implications and risks of low-molecule weight organic acid (LMWOA) on soil Pb were analyzed. The results indicated that all three types of LMWOA increased the desorption capacity of Pb in purple soil, and the effect followed the descending order of CA > TA > AC. After the action of LMWOAs, the exchangeable Pb increased; the carbonate-bound Pb and Fe-Mn oxide bound Pb dropped in soil solid phase. Organic bound Pb was the main speciation in soil solution phase, accounting for 45.16%-75.05%. The following speciation of Pb in soil solution was free Pb, accounting for 22.71%-50.25%. For CA and TA treatments, free Pb ions and inorganic bound Pb in soil solution increased with increasing LMWOAs concentration, while organic bound Pb suffered a decrease in this process. An opposite trend for AC treatment was observed compared with CA and TA treatments. Overall, LMWOAs boosted the bioavailability of Pb in purple soil and had a potential risk to contaminate underground water. Among the three LMWOAs in this study, CA had the largest potential to activate soil Pb. PMID:27548978

  15. [Effects of Low-Molecular-Weight Organic Acids on the Speciation of Pb in Purple Soil and Soil Solution].

    PubMed

    Liu, Jiang; Jiang, Tao; Huang, Rong; Zhang, Jin-zhong; Chen, Hong

    2016-04-15

    Lead (Pb) in purple soil was selected as the research target, using one-step extraction method with 0.01 mol · L⁻¹ sodium nitrate as the background electrolyte to study the release effect of citric acid (CA), tartaric acid (TA) and acetic acid (AC) with different concentrations. Sequential extraction and geochemical model (Visual Minteq v3.0) were applied to analyze and predict the speciation of Pb in soil solid phase and soil solution phase. Then the ebvironmental implications and risks of low-molecule weight organic acid (LMWOA) on soil Pb were analyzed. The results indicated that all three types of LMWOA increased the desorption capacity of Pb in purple soil, and the effect followed the descending order of CA > TA > AC. After the action of LMWOAs, the exchangeable Pb increased; the carbonate-bound Pb and Fe-Mn oxide bound Pb dropped in soil solid phase. Organic bound Pb was the main speciation in soil solution phase, accounting for 45.16%-75.05%. The following speciation of Pb in soil solution was free Pb, accounting for 22.71%-50.25%. For CA and TA treatments, free Pb ions and inorganic bound Pb in soil solution increased with increasing LMWOAs concentration, while organic bound Pb suffered a decrease in this process. An opposite trend for AC treatment was observed compared with CA and TA treatments. Overall, LMWOAs boosted the bioavailability of Pb in purple soil and had a potential risk to contaminate underground water. Among the three LMWOAs in this study, CA had the largest potential to activate soil Pb.

  16. Determination of low-molecular-weight organic acids in non-small cell lung cancer with a new liquid chromatography-tandem mass spectrometry method.

    PubMed

    Klupczynska, Agnieszka; Plewa, Szymon; Dyszkiewicz, Wojciech; Kasprzyk, Mariusz; Sytek, Natalia; Kokot, Zenon J

    2016-09-10

    As compared to other classes of metabolites, determination of organic acids is an underrepresented field in cancer research and till now there has been a lack of appropriate analytical procedure for determination of serum levels of organic acids potentially associated with cancer development. The aim of the study was to develop a new rapid liquid chromatography-tandem mass spectrometry method for the quantification of six low-molecular-weight organic acids in human serum and to apply this method in an analysis of samples collected from non-small cell lung cancer (NSCLC) patients and a matched control group. The samples were prepared by solid phase extraction (Clean-up CUQAX, UCT). Chromatography was conducted on a Synergi Hydro-RP column (Phenomenex) and a gradient run of 15min. Detection was performed using a negative multiple reaction monitoring mode. The calibration ranges were as follows: 0.24-38.42μmol/L for 2-hydroxybutyric acid, 0.09-17.23μmol/L for fumaric acid, 0.08-15.13μmol/L for glutaric acid, 0.11-2.22mmol/L for lactic acid, 0.39-30.98μmol/L for pyroglutamic acid, and 0.08-16.93μmol/L for succinic acid. Mean relative recovery range was 85.99-114.42% and the determined intra- and inter day coefficients of variation were ≤14%. Among the studied acids, pyroglutamic acid showed the best discriminating potential and enabled to identify accurately NSCLC patients and control subjects regardless of the cancer stage. Further investigations of serum organic acids may allow us to better understand the underlying mechanisms involved in NSCLC and develop novel means of its detection and treatment. The developed method may be also a valuable tool to study metabolic changes associated with other types of cancer. PMID:27454081

  17. Determination of low-molecular-weight organic acids in non-small cell lung cancer with a new liquid chromatography-tandem mass spectrometry method.

    PubMed

    Klupczynska, Agnieszka; Plewa, Szymon; Dyszkiewicz, Wojciech; Kasprzyk, Mariusz; Sytek, Natalia; Kokot, Zenon J

    2016-09-10

    As compared to other classes of metabolites, determination of organic acids is an underrepresented field in cancer research and till now there has been a lack of appropriate analytical procedure for determination of serum levels of organic acids potentially associated with cancer development. The aim of the study was to develop a new rapid liquid chromatography-tandem mass spectrometry method for the quantification of six low-molecular-weight organic acids in human serum and to apply this method in an analysis of samples collected from non-small cell lung cancer (NSCLC) patients and a matched control group. The samples were prepared by solid phase extraction (Clean-up CUQAX, UCT). Chromatography was conducted on a Synergi Hydro-RP column (Phenomenex) and a gradient run of 15min. Detection was performed using a negative multiple reaction monitoring mode. The calibration ranges were as follows: 0.24-38.42μmol/L for 2-hydroxybutyric acid, 0.09-17.23μmol/L for fumaric acid, 0.08-15.13μmol/L for glutaric acid, 0.11-2.22mmol/L for lactic acid, 0.39-30.98μmol/L for pyroglutamic acid, and 0.08-16.93μmol/L for succinic acid. Mean relative recovery range was 85.99-114.42% and the determined intra- and inter day coefficients of variation were ≤14%. Among the studied acids, pyroglutamic acid showed the best discriminating potential and enabled to identify accurately NSCLC patients and control subjects regardless of the cancer stage. Further investigations of serum organic acids may allow us to better understand the underlying mechanisms involved in NSCLC and develop novel means of its detection and treatment. The developed method may be also a valuable tool to study metabolic changes associated with other types of cancer.

  18. Stable carbon isotopic compositions of low-molecular-weight dicarboxylic acids, oxocarboxylic acids, α-dicarbonyls, and fatty acids: Implications for atmospheric processing of organic aerosols

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-Lin; Kawamura, Kimitaka; Cao, Fang; Lee, Meehye

    2016-04-01

    Stable carbon isotopic compositions (δ13C) were measured for 23 individual organic species including 9 dicarboxylic acids, 7 oxocarboxylic acids, 1 tricarboxylic acid, 2 α-dicarbonyls, and 4 fatty acids in the aerosols from Gosan background site in East Asia. δ13C values of particle phase glyoxal and methylglyoxal are significantly larger than those previously reported for isoprene and other precursors. The values are consistently less negative in oxalic acid (C2, average -14.1‰), glyoxylic acid (-13.8‰), pyruvic acid (-19.4‰), glyoxal (-13.5‰), and methylglyoxal (-18.6‰) compared to other organic species (e.g., palmitic acid, -26.3‰), which can be explained by the kinetic isotope effects during atmospheric oxidation of pre-aged precursors (e.g., isoprene) and the subsequent gas-particle partitioning after the evaporation of clouds or wet aerosols. The δ13C values of C2 is positively correlated with C2 to organic carbon ratio, indicating that photochemical production of C2 is more pronounced than its degradation during long-range atmospheric transport. The isotopic results also suggest that aqueous phase oxidation of glyoxal and methylglyoxal is a major formation process of oxalic acid via the intermediates such as glyoxylic acid and pyruvic acid. This study provides evidence that organic aerosols are intensively photochemically aged in the western North Pacific rim.

  19. Stearic acid and high molecular weight PEO as matrix for the highly water soluble metoprolol tartrate in continuous twin-screw melt granulation.

    PubMed

    Monteyne, Tinne; Adriaensens, Peter; Brouckaert, Davinia; Remon, Jean-Paul; Vervaet, Chris; De Beer, Thomas

    2016-10-15

    Granules with release-sustaining properties were developed by twin screw hot melt granulation (HMG) using a combination of stearic acid (SA) and high molecular weight polyethylene oxide (PEO) as matrix for a highly water soluble model drug, metoprolol tartrate (MPT). Earlier studies demonstrated that mixing molten SA and PEO resulted in hydrogen bond formation between hydroxyl groups of fatty acid molecules and ether groups in PEO chains. These molecular interactions might be beneficial in order to elevate the sustained release effect of drugs from a SA/PEO matrix. This study aims to investigate the continuous twin screw melt granulation technique to study the impact of a SA/PEO matrix on the dissolution rate of a highly water soluble drug (MPT). Decreasing the SA/PEO ratio improved the release-sustaining properties of the matrix. The solid state of the granules was characterized using differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) and near infrared chemical imaging (NIR-CI) in order to understand the dissolution behavior. The results revealed a preferential interaction of the MPT molecules with stearic acid impeding the PEO to form hydrogen bonds with the stearic acid chains. However, this allowed the PEO chains to recrystallize inside the stearic acid matrix after granulation, hence, elevating the release-sustaining characteristics of the formulation.

  20. Stearic acid and high molecular weight PEO as matrix for the highly water soluble metoprolol tartrate in continuous twin-screw melt granulation.

    PubMed

    Monteyne, Tinne; Adriaensens, Peter; Brouckaert, Davinia; Remon, Jean-Paul; Vervaet, Chris; De Beer, Thomas

    2016-10-15

    Granules with release-sustaining properties were developed by twin screw hot melt granulation (HMG) using a combination of stearic acid (SA) and high molecular weight polyethylene oxide (PEO) as matrix for a highly water soluble model drug, metoprolol tartrate (MPT). Earlier studies demonstrated that mixing molten SA and PEO resulted in hydrogen bond formation between hydroxyl groups of fatty acid molecules and ether groups in PEO chains. These molecular interactions might be beneficial in order to elevate the sustained release effect of drugs from a SA/PEO matrix. This study aims to investigate the continuous twin screw melt granulation technique to study the impact of a SA/PEO matrix on the dissolution rate of a highly water soluble drug (MPT). Decreasing the SA/PEO ratio improved the release-sustaining properties of the matrix. The solid state of the granules was characterized using differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) and near infrared chemical imaging (NIR-CI) in order to understand the dissolution behavior. The results revealed a preferential interaction of the MPT molecules with stearic acid impeding the PEO to form hydrogen bonds with the stearic acid chains. However, this allowed the PEO chains to recrystallize inside the stearic acid matrix after granulation, hence, elevating the release-sustaining characteristics of the formulation. PMID:27452420

  1. Stable carbon isotopic compositions of low-molecular-weight dicarboxylic acids, oxocarboxylic acids, α-dicarbonyls, and fatty acids: implications for atmospheric processing of organic aerosols

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Kawamura, K.; Cao, F.; Lee, M.

    2015-12-01

    Stable carbon isotopic compositions (δ13C) were measured for 23 individual organic species including 9 dicarboxylic acids, 7 oxocarboxylic acids, 1 tricarboxylic acid, 2 α-dicarbonyls and 4 fatty acids in the aerosols from Gosan background site in East Asia. δ13C of particle-phase glyoxal and methylglyoxal are significantly higher than those previously reported for isoprene and other precursors, associated with isotope fractionation during atmospheric oxidation. 13C is consistently more enriched for oxalic acid (C2), glyoxylic acid, pyruvic acid, glyoxal and methylglyoxal compared to other organic compounds identified, which can be explained by the kinetic isotope effects during aqueous-phase processing and the subsequent gas-particle partitioning after clouds or wet aerosols evaporation δ13C of C2 is positively correlated with C2 and organic carbon ratio, indicating that a photochemical production of C2 is more pronounced than its degradation process during long-range transport. The 13C results also suggest that aqueous-phase oxidation of glyoxal and methylglyoxal is major formation process of oxalic acid production via the major intermediates glyoxylic acid and pyruvic acid. This study provides evidence that organic aerosols are intensively photo-chemically aged in this region.

  2. The Molecular Weight Distribution of Polymer Samples

    ERIC Educational Resources Information Center

    Horta, Arturo; Pastoriza, M. Alejandra

    2007-01-01

    Various methods for the determination of the molecular weight distribution (MWD) of different polymer samples are presented. The study shows that the molecular weight averages and distribution of a polymerization completely depend on the characteristics of the reaction itself.

  3. Structures of Human Cyctochrome P450 2E1: Insights Into the Binding of Inhibitors And Both Small Molecular Weight And Fatty Acid Substrates

    SciTech Connect

    Porubsky, P.R.; Meneely, K.M.; Scott, E.E.

    2009-05-21

    Human microsomal cytochrome P-450 2E1 (CYP2E1) monooxygenates >70 low molecular weight xenobiotic compounds, as well as much larger endogenous fatty acid signaling molecules such as arachidonic acid. In the process, CYP2E1 can generate toxic or carcinogenic compounds, as occurs with acetaminophen overdose, nitrosamines in cigarette smoke, and reactive oxygen species from uncoupled catalysis. Thus, the diverse roles that CYP2E1 has in normal physiology, toxicity, and drug metabolism are related to its ability to metabolize diverse classes of ligands, but the structural basis for this was previously unknown. Structures of human CYP2E1 have been solved to 2.2 {angstrom} for an indazole complex and 2.6 {angstrom} for a 4-methylpyrazole complex. Both inhibitors bind to the heme iron and hydrogen bond to Thr{sup 303} within the active site. Complementing its small molecular weight substrates, the hydrophobic CYP2E1 active site is the smallest yet observed for a human cytochrome P-450. The CYP2E1 active site also has two adjacent voids: one enclosed above the I helix and the other forming a channel to the protein surface. Minor repositioning of the Phe{sup 478} aromatic ring that separates the active site and access channel would allow the carboxylate of fatty acid substrates to interact with conserved {sup 216}QXXNN{sup 220} residues in the access channel while positioning the hydrocarbon terminus in the active site, consistent with experimentally observed {omega}-1 hydroxylation of saturated fatty acids. Thus, these structures provide insights into the ability of CYP2E1 to effectively bind and metabolize both small molecule substrates and fatty acids.

  4. Influence of average molecular weights of poly(DL-lactic acid-co-glycolic acid) copolymers 50/50 on phase separation and in vitro drug release from microspheres.

    PubMed

    Ruiz, J M; Busnel, J P; Benoît, J P

    1990-09-01

    The phase separation of fractionated poly(DL-lactic acid-co-glycolic acid) copolymers 50/50 was determined by silicone oil addition. Polymer fractionation by preparative size exclusion chromatography afforded five different microsphere batches. Average molecular weight determined the existence, width, and displacement of the "stability window" inside the phase diagrams, and also microsphere characteristics such as core loading and amount released over 6 hr. Further, the gyration and hydrodynamic radii were measured by light scattering. It is concluded that the polymer-solvent affinity is largely modified by the variation of average molecular weights owing to different levels of solubility. The lower the average molecular weight is, the better methylene chloride serves as a solvent for the coating material. However, a paradoxical effect due to an increase in free carboxyl and hydroxyl groups is noticed for polymers of 18,130 and 31,030 SEC (size exclusion chromatography) Mw. For microencapsulation, polymers having an intermediate molecular weight (47,250) were the most appropriate in terms of core loading and release purposes. PMID:2235892

  5. Influence of average molecular weights of poly(DL-lactic acid-co-glycolic acid) copolymers 50/50 on phase separation and in vitro drug release from microspheres.

    PubMed

    Ruiz, J M; Busnel, J P; Benoît, J P

    1990-09-01

    The phase separation of fractionated poly(DL-lactic acid-co-glycolic acid) copolymers 50/50 was determined by silicone oil addition. Polymer fractionation by preparative size exclusion chromatography afforded five different microsphere batches. Average molecular weight determined the existence, width, and displacement of the "stability window" inside the phase diagrams, and also microsphere characteristics such as core loading and amount released over 6 hr. Further, the gyration and hydrodynamic radii were measured by light scattering. It is concluded that the polymer-solvent affinity is largely modified by the variation of average molecular weights owing to different levels of solubility. The lower the average molecular weight is, the better methylene chloride serves as a solvent for the coating material. However, a paradoxical effect due to an increase in free carboxyl and hydroxyl groups is noticed for polymers of 18,130 and 31,030 SEC (size exclusion chromatography) Mw. For microencapsulation, polymers having an intermediate molecular weight (47,250) were the most appropriate in terms of core loading and release purposes.

  6. Influence of season and salinity on the exudation of aliphatic low molecular weight organic acids (ALMWOAs) by Phragmites australis and Halimione portulacoides roots

    NASA Astrophysics Data System (ADS)

    Rocha, A. Cristina S.; Almeida, C. Marisa R.; Basto, M. Clara P.; Vasconcelos, M. Teresa S. D.

    2015-01-01

    Plant roots have the ability to produce and secrete substances, such as aliphatic low molecular weight organic acids (ALMWOAs), into the rhizosphere. This phenomenon occurs for several purposes, for instance, the detoxification of pollutants. Nevertheless, knowledge about the exudation of such substances from marsh plants roots is still scarce. This work aimed at studying: 1) the ability of marsh plants, freshly collected in estuarine marshes, to liberate ALMWOAs into the surrounding medium and 2) the influence of the physiological cycle of these plants on the exudation of those substances. In vitro experiments were carried out, in different seasons, with Phragmites australis and Halimione portulacoides (two marsh plants widely distributed in Europe). Root exudates were collected in freshwater to which plant specimens, in different physiological stages, were exposed. Both marsh plants were capable of liberating oxalic and citric acids into the surrounding medium. Formic acid was also released by P. australis roots and acetic acid by H. portulacoides. There was a seasonal effect on the liberation of ALMWOAs by both plant roots. Marked changes were registered in the nature and levels of the ALMWOAs liberated and such changes depended upon the season in which the specimens were collected. In growing season, a significantly higher liberation of oxalic and citric acids (and acetic acid but only in H. portulacoides case) was observed. For P. australis, formic acid was only found in the decaying stage (autumn and winter). The nature of the medium (in particular, salinity) was a feature conditioning the exudation of ALMWOAs. Both plants were shown to contribute for the presence of ALMWOAs in marsh rhizosediments (some ALMWOAs were found in pore waters extracted). The nature and extent of this contribution will be however dependent upon plants' physiological stage, in addition to plant species. Therefore, these features should be taken into consideration in the event of

  7. Effect of molecular weight on polyphenylquinoxaline properties

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.

    1991-01-01

    A series of polyphenyl quinoxalines with different molecular weight and end-groups were prepared by varying monomer stoichiometry. Thus, 4,4'-oxydibenzil and 3,3'-diaminobenzidine were reacted in a 50/50 mixture of m-cresol and xylenes. Reaction concentration, temperature, and stir rate were studied and found to have an effect on polymer properties. Number and weight average molecular weights were determined and correlated well with viscosity data. Glass transition temperatures were determined and found to vary with molecular weight and end-groups. Mechanical properties of films from polymers with different molecular weights were essentially identical at room temperature but showed significant differences at 232 C. Diamine terminated polymers were found to be much less thermooxidatively stable than benzil terminated polymers when aged at 316 C even though dynamic thermogravimetric analysis revealed only slight differences. Lower molecular weight polymers exhibited better processability than higher molecular weight polymers.

  8. Photo-induced cold vapor generation with low molecular weight alcohol, aldehyde, or carboxylic acid for atomic fluorescence spectrometric determination of mercury.

    PubMed

    Han, Chunfang; Zheng, Chengbin; Wang, Jun; Cheng, Guanglei; Lv, Yi; Hou, Xiandeng

    2007-06-01

    With UV irradiation, Hg(2+) in aqueous solution can be converted into Hg(0) cold vapor by low molecular weight alcohols, aldehydes, or carboxylic acids, e.g., methanol, formaldehyde, acetaldehyde, glycol, 1,2-propanediol, glycerol, acetic acid, oxalic acid, or malonic acid. It was found that the presence of nano-TiO(2) more or less improved the efficiency of the photo-induced chemical/cold vapor generation (photo-CVG) with most of the organic reductants. The nano-TiO(2)-enhanced photo-CVG systems can be coupled to various analytical atomic spectrometric techniques for the determination of ultratrace mercury. In this work, we evaluated the application of this method to the atomic fluorescence spectrometric (AFS) determination of mercury in cold vapor mode. Under the optimized experimental conditions, the instrumental limits of detection (based on three times the standard deviation of 11 measurements of a blank solution) were around 0.02-0.04 microg L(-1), with linear dynamic ranges up to 15 microg L(-1). The interference of transition metals and the mechanism of the photo-CVG are briefly discussed. Real sample analysis using the photo-CVG-AFS method revealed that it was promising for water and geological analysis of ultralow levels of mercury.

  9. Influence of Ca/Mg ratio on phytoextraction properties of Salix viminalis. II. Secretion of low molecular weight organic acids to the rhizosphere.

    PubMed

    Magdziak, Z; Kozlowska, M; Kaczmarek, Z; Mleczek, M; Chadzinikolau, T; Drzewiecka, K; Golinski, P

    2011-01-01

    A hydroponic experiment in a phytotron was performed to investigate the effect of two different Ca/Mg ratios (4:1 and 1:10) and trace element ions (Cd, Cu, Pb and Zn) in solution on the efficiency of low molecular weight organic acid (LMWOA) formation in Salix viminalis rhizosphere. Depending on the Ca/Mg ratio and presence of selected trace elements at 0.5mM concentration, the amount and kind of LMWOAs in the rhizosphere were significantly affected. In physiological 4:1 Ca/Mg ratio the following complex of acids was observed: malonic (Pb, Zn), citric, lactic, maleic and succinic (Zn) acids. Under 1:10 Ca/Mg ratio, citric (Cd, Zn), maleic and succinic (Cd, Cu, Pb, Zn) acids were seen. Additionally, high accumulation of zinc and copper in all systems was observed, with the exception of those where one of the metals was at higher concentration. Summing up, the results indicate a significant role of LMWOAs in Salix phytoremediation abilities. Both effects can be modulated depending on the mutual Ca/Mg ratio.

  10. Evaluation of diethylenetriaminepentaacetic acid-manganese(II) complexes modified by narrow molecular weight distribution of chitosan oligosaccharides as potential magnetic resonance imaging contrast agents.

    PubMed

    Huang, Yan; Zhang, Xiaoyan; Zhang, Qi; Dai, Xueqin; Wu, Jingbo

    2011-05-01

    Novel conjugates of narrow molecular weight distribution of chitosan oligosaccharides (CSn; n=6, 8, 11) with manganese-diethylenetriaminepentaacetic acid (Mn-DTPA) as potential magnetic resonance imaging (MRI) contrast agents were synthesized. The structures were characterized by means of Fourier transform infrared spectra, (13)C nuclear magnetic resonance, size exclusion chromatography and inductively coupled plasma atomic emission spectrometry. The characterization results showed that Mn-DTPA was successfully linked to aminated CSn by an amide function. The magnetic properties were characterized by in vitro and T(1)-weighted FLASH image experiments. Relaxivities studies indicated that Mn-DTPA-CSn (n=8, 11) provided higher relaxivity, either in aqueous or bovine serum albumin solution (0.725 mM), than commercial contrast agent Gd-DTPA. The stability results showed that Mn-DTPA-CSn in aqueous were stable enough to prevent Mn(II) ions from releasing. The preliminary in vitro and T(1)-weighted FLASH image studies suggested that Mn-DTPA-CSn had the advantage of becoming promising MRI contrast agents.

  11. Effect of enhanced UV-B radiation on methane emission in a paddy field and rice root exudation of low-molecular-weight organic acids.

    PubMed

    He, Yongmei; Zhan, Fangdong; Li, Yuan; Xu, Weiwei; Zu, Yanqun; Yue, Ming

    2016-06-01

    A local rice variety, "Baijiaolaojing", was grown in a paddy field in the Yuanyang rice terraces under ambient and supplemental levels of ultraviolet-B (UV-B, 280-315 nm) radiation. The effects of enhanced UV-B radiation (5 and 10 kJ m(-2) d(-1)) on methane emissions in the paddy field were evaluated using a closed-chamber gas chromatography-based system, and the contents of low-molecular-weight organic acids (LMWOAs) in root exudates were determined by high-performance liquid chromatography (HPLC). Peaks in methane emissions in the paddy field were detected at 60, 80 and 100 days after rice transplantation. The highest level of cumulative methane emissions occurred at the tillering stage, followed by the jointing-booting and maturity stages. The lowest level was found at the flowering stage. The enhanced UV-B radiation did not change the seasonal variation in methane emissions in the paddy field; however, it induced a significant increase in the flux of methane emissions at the jointing-booting and maturity stages, as well as a significant increase in the cumulative flux of methane emissions throughout the growth period. In addition, the enhanced UV-B radiation caused an increase in the contents of oxalic acid and succinic acid and a decrease in the contents of tartaric acid and malic acid in rice root exudates. Furthermore, a significant positive correlation (r = 0.725, p < 0.01) was found between the content of oxalic acid and the methane emissions in the paddy field. The results indicated that enhanced UV-B radiation promoted methane emissions in the paddy field, which was closely associated with its impact on the exudation of LMWOAs by rice roots. PMID:27194164

  12. Effects of low molecular weight organic acids on the immobilization of aqueous Pb(II) using phosphate rock and different crystallized hydroxyapatite.

    PubMed

    Wei, Wei; Cui, Jing; Wei, Zhenggui

    2014-06-01

    Understanding the effects of low molecular weight organic acids (LMWOAs) on the transformation of Pb(II) to geochemically stable pyromorphite (PY) by apatite materials (AMs), has considerable benefits for risk assessment and remediation strategies for contaminated water and soil. In this study, we systematically investigated the immobilization of Pb(II) from aqueous solution by natural phosphate rock (PR) and different crystallized hydroxyapatite (HAp) in the absence and presence of LMWOAs (oxalic, malic and citric acids). The results indicated that the effectiveness of PR and HAp in immobilizing Pb(II) followed in descending order by HAp2 (the poorly crystallized HAp), HAp1 (the well crystallized HAp) and PR, regardlessof the presence of LMWOAs. The presence of malic and citric acids significantly decreased the immobilizationefficiency of Pb(II) by HAp1 and PR, clarifying the lower adsorption affinities of Pb(II)-organic acid complexes on HAp1 and PR rather than Pb(II) ion. On thecontrary, oxalic acid could markedly enhance the removal of Pb(II) from aqueous solution by HAp1 and PR through the formation of lead oxalate, which was confirmed by FT-IR and XRDanalysis. Results also showed that LMWOAs had little promoting or inhibiting effect on the immobilization of Pb(II) by HAp2. This study suggested that the ubiquity of LMWOAs in natural environments could retard the transformation efficiency of Pb(II) to PY by AMs, especiallyin thepresenceof oxalic acid, and the poorly crystallized HAp2 had great potential to remediate Pb(II)-contaminated water and soil due to its insusceptibility to LMWOAs.

  13. Method for characterization of low molecular weight organic acids in atmospheric aerosols using ion chromatography mass spectrometry.

    PubMed

    Brent, Lacey C; Reiner, Jessica L; Dickerson, Russell R; Sander, Lane C

    2014-08-01

    The structural composition of PM2.5 monitored in the atmosphere is usually divided by the analysis of organic carbon, black (also called elemental) carbon, and inorganic salts. The characterization of the chemical composition of aerosols represents a significant challenge to analysts, and studies are frequently limited to determination of aerosol bulk properties. To better understand the potential health effects and combined interactions of components in aerosols, a variety of measurement techniques for individual analytes in PM2.5 need to be implemented. The method developed here for the measurement of organic acids achieves class separation of aliphatic monoacids, aliphatic diacids, aromatic acids, and polyacids. The selective ion monitoring capability of a triple quadropole mass analyzer was frequently capable of overcoming instances of incomplete separations. Standard Reference Material (SRM) 1649b Urban Dust was characterized; 34 organic acids were qualitatively identified, and 6 organic acids were quantified.

  14. Soluble high molecular weight polyimide resins

    NASA Technical Reports Server (NTRS)

    Jones, R. J.; Lubowitz, H. R.

    1970-01-01

    High molecular weight polyimide resins have greater than 20 percent /by weight/ solubility in polar organic solvents. They permit fabrication into films, fibers, coatings, reinforced composite, and adhesive product forms. Characterization properties for one typical polyimide resin are given.

  15. Low molecular weight dicarboxylic acids, ketoacids, and dicarbonyls in the fine particles from a roadway tunnel: possible secondary production from the precursors.

    PubMed

    Wang, Haobo; Kawamura, Kimitaka; Ho, K F; Lee, S C

    2006-10-15

    Low molecular weight dicarboxylic acids (DCAs), ketoacids, and alpha-dicarbonyls have been determined for the PM2.5 samples in a Hong Kong roadway tunnel, using a water extraction followed by a butyl ester and/or dibutyl acetal derivatization technique. For the most wintertime sampling runs, outlet and inlet concentrations of the quantified compounds were found to be quite similar (ca. 10% differences), leading to the conclusion that direct emissions of the organic compounds are insignificant from vehicles in hot-stabilized operations although vehicular emissions can provide important precursors to them. In contrast, a significant concentration increase of most compounds was observed at the outlet station compared to the inlet station in the summertime runs, which might be explained by the secondary production of aerosols in the tunnel. The organic compounds studied comprised a small fraction (<1%) of aerosol organic carbon (OC). In winter, their abundances relative to that of OC in outlet samples were found to be significantly less than those in inlet samples. On the basis of the summer data, apparent secondary production factors of the compounds were calculated, which indicate that adipic and m-phthalic acids can be favorably formed in the tunnel. However, like other DCAs, direct emissions of adipic, m-phthalic, and p-phthalic acids from automobiles are suggested to be insignificant.

  16. Impacts of low-molecular-weight organic acids on aquatic behavior of graphene nanoplatelets and their induced algal toxicity and antioxidant capacity.

    PubMed

    Wang, Zhuang; Gao, Yucheng; Wang, Se; Fang, Hao; Xu, Defu; Zhang, Fan

    2016-06-01

    Knowledge of the interaction between graphene-based materials and low-molecular-weight organic acids (LOAs) is essential to understand fate and effects of graphene-based materials in the aquatic environment, but this interaction remains poorly elucidated. In this study, the effects of LOAs on the physicochemical properties of graphene nanoplatelets (GNPs) in an aqueous medium and on the GNP toxicity to algae were studied. The unicellular green alga Scenedesmus obliquus was exposed to GNP suspensions in the presence of benzoic acid or gallic acid at various concentrations. The GNPs had smaller hydrodynamic sizes and the GNP suspensions were more stable and had higher or lower surface zeta potentials in the presence of LOAs than when LOAs were not present. The toxic effects in S. obliquus cultures incubated with GNP suspensions containing LOAs were related to the LOA concentration, and the presence of LOAs caused three effects: stimulation, alleviation, and synergistic inhibition. The intensities of the effects mainly correlated with the LOA concentration, the extent of agglomeration, and particle-induced oxidative stress. The results indicate that the environmental fates and toxicities of GNPs are strongly affected by the binding of GNPs to LOAs. PMID:26898932

  17. Direct chromatographic enantioresolution of fully constrained β-amino acids: exploring the use of high-molecular weight chiral selectors.

    PubMed

    Sardella, Roccaldo; Ianni, Federica; Lisanti, Antonella; Scorzoni, Stefania; Marini, Francesca; Sternativo, Silvia; Natalini, Benedetto

    2014-05-01

    To the best of our knowledge enantioselective chromatographic protocols on β-amino acids with polysaccharide-based chiral stationary phases (CSPs) have not yet appeared in the literature. Therefore, the primary objective of this work was the development of chromatographic methods based on the use of an amylose derivative CSP (Lux Amylose-2), enabling the direct normal-phase (NP) enantioresolution of four fully constrained β-amino acids. Also, the results obtained with the glycopeptide-type Chirobiotic T column employed in the usual polar-ionic (PI) mode of elution are compared with those achieved with the polysaccharide-based phase. The Lux Amylose-2 column, in combination with alkyl sulfonic acid containing NP eluent systems, prevailed over the Chirobiotic T one, when used under the PI mode of elution, and hence can be considered as the elective choice for the enantioseparation of this class of rigid β-amino acids. Moreover, the extraordinarily high α (up to 4.60) and R S (up to 10.60) values provided by the polysaccharidic polymer, especially when used with camphor sulfonic acid containing eluent systems, make it also suitable for preparative-scale enantioisolations.

  18. Polar organic marker compounds in atmospheric aerosol in the Po Valley during the Supersito campaigns - Part 1: Low molecular weight carboxylic acids in cold seasons

    NASA Astrophysics Data System (ADS)

    Pietrogrande, Maria Chiara; Bacco, Dimitri; Visentin, Marco; Ferrari, Silvia; Poluzzi, Vanes

    2014-04-01

    In the framework of the “Supersito” project, three intensive experimental campaigns were conducted in the Po Valley (Northern Italy) in cold seasons, such as late autumn, pre-winter and deep-winter, over three years from 2011 to 2013. As a part of a study on polar marker compounds, including carboxylic acids, sugar derivatives and lignin phenols, the present study reports a detailed discussion on the atmospheric concentrations of 14 low molecular weight carboxylic acids, mainly dicarboxylic and oxo-hydroxy carboxylic acids, as relevant markers of primary and secondary organic aerosols. PM2.5 samples were collected in two monitoring sites, representing urban and rural background stations. The total quantities of carboxylic acids were 262, 167 and 249 ng m-3 at the urban site and 308, 115, 248 ng m-3 at the rural site in pre-winter, fall and deep-winter, respectively. These high concentrations can be explained by the large human emission sources in the urbanized region, combined with the stagnant atmospheric conditions during the cold seasons that accumulate the organic precursors and accelerate the secondary atmospheric reactions. The distribution profiles of the investigated markers suggest the dominant contributions of primary anthropogenic sources, such as traffic, domestic heating and biomass burning. These results are confirmed by comparison with additional emission tracers, such as anhydro-saccharides for biomass burning and fatty acids originated from different anthropogenic sources. In addition, some secondary constituents were detected in both sites, as produced by in situ photo-chemical reactions from both biogenic (e.g. pinonic acid) and anthropogenic precursors (e.g. phthalic and adipic acids). The impact of different sources from human activities was elucidated by investigating the week pattern of carboxylic and fatty acid concentrations. The weekly trends of analytes during the warmer campaign (fall 2012; mean temperature: 12 °C) may be related to

  19. Effects of Low-Molecular-Weight Organic Acids on the Dissolution of Hydroxyapatite Nanoparticles in Batch and Column Experiments: A Perspective from Phosphate Oxygen Isotope Fractionation

    NASA Astrophysics Data System (ADS)

    Wang, D.; Jaisi, D. P.; Jin, Y.

    2015-12-01

    Hydroxyapatite nanoparticles (HANPs) are increasingly being advocated as an efficient and environment-friendly "green" phosphorus nanofertilizer attributed to their nanoscale dimension, large reactive surface area, and low leaching potential. However, knowledge of how naturally occurring low-molecular-weight organic acids (LMWOAs) that are secreted by plant roots mediate the dissolution of HANPs (releasing PO43- ion for plant growth) is nonexistent. Here three most commonly encountered LMWOAs (acetic acid, oxalic acid, and citric acid) at environmentally relevant concentration (1 mM) were evaluated for their effects on HANPs' dissolution in static batch and dynamic column systems. Particularly, phosphate oxygen isotope fractionation of HANPs during dissolution was examined to disentangle mechanisms controlling the evolution of O-isotopic composition of dissolved PO43- ion. Our results reveal that in batch experiments the dissolution of HANPs was fast but the overall dissolution efficiency of HANPs was limited (≤30%). In contrast, ~100% HANPs were dissolved in columns where LMWOAs were continuously injected. The limited dissolution of HANPs in static batch systems was due primarily to pH buffer effect (pH increased sharply when LMWOA was added in HANPs suspension), whereas in dynamic column systems the HANPs were continuously dissolved by low pH LMWOAs and leached away. Regardless of LMWOA type and experimental system, the isotopically light phosphate (P16O4) was preferentially released during dissolution and the O-isotopic composition of dissolved PO43- ion increased gradually with increasing dissolution due to equilibrium isotope effect between dissolved PO43- ion and HANPs. However, the overall magnitude of O-isotopic fractionation of dissolved PO43- ion was less in batch than in column systems, due to less mass transfer between dissolved PO43- ions and HANPs in batch relative to column experiments. Our findings provide new insights into bioavailability

  20. Enhancing the intestinal absorption of low molecular weight chondroitin sulfate by conjugation with α-linolenic acid and the transport mechanism of the conjugates.

    PubMed

    Xiao, Yuliang; Li, Pingli; Cheng, Yanna; Zhang, Xinke; Sheng, Juzheng; Wang, Decai; Li, Juan; Zhang, Qian; Zhong, Chuanqing; Cao, Rui; Wang, Fengshan

    2014-04-25

    The purpose of this report was to demonstrate the effect of amphiphilic polysaccharides-based self-assembling micelles on enhancing the oral absorption of low molecular weight chondroitin sulfate (LMCS) in vitro and in vivo, and identify the transepithelial transport mechanism of LMCS micelles across the intestinal barrier. α-Linolenic acid-low molecular weight chondroitin sulfate polymers(α-LNA-LMCS) were successfully synthesized, and characterized by FTIR, (1)HNMR, TGA/DSC, TEM, laser light scattering and zeta potential. The significant oral absorption enhancement and elimination half-life (t₁/₂) extension of LNA-LMCS2 in rats were evidenced by intragastric administration in comparison with CS and LMCS. Caco-2 transport studies demonstrated that the apparent permeability coefficient (Papp) of LNA-LMCS2 was significantly higher than that of CS and LMCS (p<0.001), and no significant effects on the overall integrity of the monolayer were observed during the transport process. In addition, α-LNA-LMCS micelles accumulated around the cell membrane and intercellular space observed by confocal laser scanning microscope (CLSM). Furthermore, evident alterations in the F-actin cytoskeleton were detected by CLSM observation following the treatment of the cell monolayers with α-LNA-LMCS micelles, which further certified the capacity of α-LNA-LMCS micelles to open the intercellular tight junctions rather than disrupt the overall integrity of the monolayer. Therefore, LNA-LMCS2 with low cytotoxicity and high bioavailability might be a promising substitute for CS in clinical use, such as treating osteoarthritis, atherosclerosis, etc.

  1. Improving the mining soil quality for a vegetation cover after addition of sewage sludges: inorganic ions and low-molecular-weight organic acids in the soil solution.

    PubMed

    Peña, Aránzazu; Mingorance, Ma Dolores; Guzmán-Carrizosa, Ignacio; Fernández-Espinosa, Antonio J

    2015-03-01

    We assessed the effects of applying stabilized sewage sludge (SSL) and composted sewage sludge (CLV), at 5 and 10% to an acid mining soil. Limed soil (NCL) amended or not with SSL and CLV was incubated for 47 days. We studied the cations and organic and inorganic anions in the soil solution by means of ion chromatography. Liming led to big increases in Ca(2+) and SO4(2-) and to significant decreases in K(+), Mg(2+), NH4(+) and NO3(-). Addition of both organic amendments increased some cations (NH4(+), K(+), Mg(2+), Na(+)) and anions (Cl(-), NO3(-) only with CLV and PO4(3-) only with SSL) and provided a greater amount of low-molecular-weight organic acids (LMWOAs) (SSL more than CLV). Incubation led to decreases in all cations, particularly remarkable for Ca(2+) and Mg(2+) in SSL-10. A decrease in NH4(+) was associated with variations in NO2(-) and NO3(-) resulting from nitrification reactions. During incubation the LMWOAs content tended to decrease similarly to the cations, especially in SSL-10. Chemometric tools revealed a clear discrimination between SSL, CLV and NCL. Furthermore, treatment effects depended upon dose, mainly in SSL. Amendment nature and dose affect the quality of a mining soil and improve conditions for plant establishment.

  2. Pharmacokinetics of a paclitaxel-loaded low molecular weight heparin-all-trans-retinoid acid conjugate ternary nanoparticulate drug delivery system.

    PubMed

    Hou, Lin; Yao, Jing; Zhou, Jianping; Zhang, Qiang

    2012-07-01

    Amphiphilic low molecular weight heparin-all-trans-retinoid acid (LHR) conjugate, as a drug carrier for cancer therapy, was found to have markedly low toxicity and to form self-assembled nanoparticles for simultaneous delivery of paclitaxel (PTX) and all-trans-retinoid acid (ATRA) in our previous study. In the present study, PTX-loaded LHR nanoparticles were prepared and demonstrated a spherical shape with particle size of 108.9 nm. Cellular uptake analysis suggested rapid internalization and nuclear transport of LHR nanoparticles. In order to investigate the dynamic behaviors and targeting ability of LHR nanoparticles on tumor-bearing mice, near-infrared fluorescent (NIFR) dye DiR was encapsulated into the nanoparticles for ex vivo optical imaging. The results indicated that LHR nanoparticles could enhance the targeting and residence time in tumor site. Furthermore, in vivo biodistribution study also showed that the area under the plasma concentration time curve (AUC (0→inf)) values of PTX and ATRA for PTX-loaded LHR nanoparticles in tumor were 1.56 and 1.62-fold higher than those for PTX plus ATRA solution. Finally, PTX-loaded LHR nanoparticles demonstrated greater tumor growth inhibition effect in vivo without unexpected side effects, compared to PTX solution and PTX plus ATRA solution. These results suggest that PTX-loaded LHR nanoparticles can be considered as promising targeted delivery system for combination cancer chemotherapy to improve therapeutic efficacy and minimize adverse effects.

  3. Improving the mining soil quality for a vegetation cover after addition of sewage sludges: inorganic ions and low-molecular-weight organic acids in the soil solution.

    PubMed

    Peña, Aránzazu; Mingorance, Ma Dolores; Guzmán-Carrizosa, Ignacio; Fernández-Espinosa, Antonio J

    2015-03-01

    We assessed the effects of applying stabilized sewage sludge (SSL) and composted sewage sludge (CLV), at 5 and 10% to an acid mining soil. Limed soil (NCL) amended or not with SSL and CLV was incubated for 47 days. We studied the cations and organic and inorganic anions in the soil solution by means of ion chromatography. Liming led to big increases in Ca(2+) and SO4(2-) and to significant decreases in K(+), Mg(2+), NH4(+) and NO3(-). Addition of both organic amendments increased some cations (NH4(+), K(+), Mg(2+), Na(+)) and anions (Cl(-), NO3(-) only with CLV and PO4(3-) only with SSL) and provided a greater amount of low-molecular-weight organic acids (LMWOAs) (SSL more than CLV). Incubation led to decreases in all cations, particularly remarkable for Ca(2+) and Mg(2+) in SSL-10. A decrease in NH4(+) was associated with variations in NO2(-) and NO3(-) resulting from nitrification reactions. During incubation the LMWOAs content tended to decrease similarly to the cations, especially in SSL-10. Chemometric tools revealed a clear discrimination between SSL, CLV and NCL. Furthermore, treatment effects depended upon dose, mainly in SSL. Amendment nature and dose affect the quality of a mining soil and improve conditions for plant establishment. PMID:25506677

  4. Relationship between lead uptake by lettuce and water-soluble low-molecular-weight organic acids in rhizosphere as influenced by transpiration.

    PubMed

    Liao, Yuan Chung; Chang Chien, Shui-Wen; Wang, Min-Chao; Shen, Yuan; Seshaiah, Kalluru

    2007-10-17

    The relationship between Pb uptake by leaf lettuce ( Lactuca sativa L.) and water-soluble low-molecular-weight organic acids (LMWOAs) in rhizosphere, as influenced by transpiration (high and low), has been studied. Studies were carried out by culturing lettuce plants grown for 2 weeks in pots filled with quartz sand mixed with anion-exchange resin and then for 30 days in a greenhouse. The potted lettuce plants were subjected to stress by the addition of Pb(NO 3) 2 solutions (100, 200, and 300 mg of Pb L (-1)) and by high and low transpiration treatments for another 10-day period. Blank experiments (without addition of Pb(NO 3) 2 solutions to the pots) were also run. There were no significant differences in the growth of the plants with the addition of Pb(NO 3) 2 solutions in either of the transpirations studies. Uptake of Pb by the shoots and roots of the plants was found to be proportional to the concentration of Pb solutions added, and more accumulation was observed in the roots than in the shoots at the end of days 3 and 10. High transpiration caused more Pb uptake than did low transpiration. One volatile acid (propionic acid) and nine nonvolatile acids (lactic, glycolic, oxalic, succinic, fumaric, oxalacetic, d-tartaric, trans-aconitic, and citric acids) in rhizosphere quartz sand or anion-exchange resin were identified and quantified by gas chromatography analysis with a flame ionization detector. The amount of LMWOAs in rhizosphere quartz sand or anion-exchange resin increased with higher amounts of Pb in quartz sand solution and also with longer duration of the study. The total quantities of the LMWOAs in the rhizosphere quartz sand or anion-exchange resin were significantly higher under high and low transpiration with a 300 mg of Pb L (-1) solution addition at the end of day 10. Compared with our previous related studies (published work), the present study shows that the presence of LMWOAs in rhizosphere does not significantly affect Pb uptake by lettuce

  5. Effect of a bioabsorbable, super-high molecular weight poly-D,L-lactic acid plate containing recombinant human bone morphogenetic protein-2 for fracture healing

    PubMed Central

    ZHOU, NING-FENG; HUANG, YU-FENG; WANG, JIN-WU

    2015-01-01

    The aim of this study was to investigate the effect of a bioabsorbable, super-high molecular weight poly-D,L-lactic acid (PDLLA) plate exhibiting the sustained release of recombinant human bone morphogenetic protein-2 (rhBMP-2) (PDLLA-rhBMP-2) on the treatment of fracture with internal fixation. A total of 32 New Zealand rabbits were randomly allocated to one of four groups (2, 4, 8 and 12 weeks), and a 2.5-mm middle ulnar osteotomy was performed bilaterally. The right side (experimental side) was fixed internally with PDLLA-rhBMP-2, and the left side (control side) was fixed with a normal PDLLA plate. At 2, 4, 8 and 12 weeks after surgery, the gross pathology of the ulnas was examined and radiographic, histological and computer image analyses were performed. The results demonstrated that the ulna fractures were fixed stably with the two bioactive plates at 2, 4, 8 and 12 weeks after surgery. At the 8-week time-point, 7 rabbits exhibited good healing at the osteotomy site on the experimental side. At 12 weeks after surgery, 8 rabbits exhibited good healing at the osteotomy site on both sides, but the experimental side showed enhanced compatibility between the plates and surrounding tissue, faster bone formation, a greater bone regeneration mass and better medullary canal structure compared with the control side. In conclusion, PPLLA-rhBMP-2 may be effectively used to treat fracture or nonunion at a non-weight-bearing site. PMID:26640559

  6. High molecular weight β-poly(L-malic acid) produced by A. pullulans with Ca²⁺ added repeated batch culture.

    PubMed

    Cao, Weifeng; Chen, Xiangrong; Luo, Jianquan; Yin, Junxiang; Qiao, Changsheng; Wan, Yinhua

    2016-04-01

    β-Poly(malic acid) (PMLA) has attracted increasing attentions because of its potential application in medicine and other industries. In this study, the variation of PMLA molecular weight (Mw) in the batch culture and the strategies to enhance PMLA Mw were studied. Adding exogenous Ca(2+) (0.1g/L CaCl2) to the medium caused a significant increase in both PMLA concentration and Mw (11.38% and 26.3%, respectively) when Na2CO3 was used as the neutralizer. The Mw of PMLA during the process of batch culture, which associated with the specific PMLA production per unit cell mass (Yp/x) before glucose was depleted, increased from 12.522 KDa to its maximum 18.693 KDa and then kept decreasing until the end of the culture. Compared with the results in batch culture, Mw increased by 84.4% (up to 19.51 kDa) with a productivity of 1.1 gh(-1)L(-1) when the cells were maintained in exponential growth phase during Ca(2+) added repeated batch culture. The present work provides an efficient approach to obtain superior quality PMLA product with high Mw.

  7. Different types of degradable vectors from low-molecular-weight polycation-functionalized poly(aspartic acid) for efficient gene delivery.

    PubMed

    Dou, X B; Hu, Y; Zhao, N N; Xu, F J

    2014-03-01

    Poly(aspartic acid) (PAsp) has been employed as the potential backbone for the preparation of efficient gene carriers, due to its low cytotoxicity, good biodegradability and excellent biocompatibility. In this work, the degradable linear or star-shaped PBLA was first prepared via ring-opining polymerization of β-benzyl-L-aspartate N-carboxy anhydride (BLA-NCA) initiated by ethylenediamine (ED) or ED-functionalized cyclodextrin cores. Then, PBLA was functionalized via aminolysis reaction with low-molecular-weight poly(2-(dimethylamino)ethyl methacrylate) with one terminal primary amine group (PDMAEMA-NH2), followed by addition of excess ED or ethanolamine (EA) to complete the aminolysis process. The obtained different types of cationic PAsp-based vectors including linear or star PAsp-PDM-NH2 and PAsp-PDM-OH exhibited good condensation capability and degradability, benefiting gene delivery process. In comparison with gold standard polyethylenimine (PEI, ∼ 25 kDa), the cationic PAsp-based vectors, particularly star-shaped ones, exhibited much better transfection performances.

  8. Collagen-low molecular weight hyaluronic acid semi-interpenetrating network loaded with gelatin microspheres for cell and growth factor delivery for nucleus pulposus regeneration.

    PubMed

    Tsaryk, Roman; Gloria, Antonio; Russo, Teresa; Anspach, Laura; De Santis, Roberto; Ghanaati, Shahram; Unger, Ronald E; Ambrosio, Luigi; Kirkpatrick, C James

    2015-07-01

    Intervertebral disc (IVD) degeneration is one of the main causes of low back pain. Current surgical treatments are complex and generally do not fully restore spine mobility. Development of injectable extracellular matrix-based hydrogels offers an opportunity for minimally invasive treatment of IVD degeneration. Here we analyze a specific formulation of collagen-low molecular weight hyaluronic acid (LMW HA) semi-interpenetrating network (semi-IPN) loaded with gelatin microspheres as a potential material for tissue engineering of the inner part of the IVD, the nucleus pulposus (NP). The material displayed a gel-like behavior, it was easily injectable as demonstrated by suitable tests and did not induce cytotoxicity or inflammation. Importantly, it supported the growth and chondrogenic differentiation potential of mesenchymal stem cells (MSC) and nasal chondrocytes (NC) in vitro and in vivo. These properties of the hydrogel were successfully combined with TGF-β3 delivery by gelatin microspheres, which promoted the chondrogenic phenotype. Altogether, collagen-LMW HA loaded with gelatin microspheres represents a good candidate material for NP tissue engineering as it combines important rheological, functional and biological features.

  9. The influence of γ-ray irradiation on the thermal stability and molecular weight of Poly(L-Lactic acid) and its nanocomposites

    NASA Astrophysics Data System (ADS)

    Yıldırım, Yeliz; Oral, Ayhan

    2014-03-01

    The gamma (γ) radiation effects on the thermal properties of Poly(L-Lactic acid) (PLLA), and three PLLA nanocomposites containing 1, 3 and 5% montmorillonite MK10 clay were investigated in different solvents such as tetrahydrofuran, chloroform and 1,4 dioxane. The polymers were irradiated by gamma radiation at low absorbed doses of 1, 5, and 10 kGy. The thermal properties and molecular weight of the unirradiated and irradiated PLLA and its nanocomposites were characterized by Thermogravimetry (TG) and Gel Permeation Chromatography (GPC), respectively. The TG curves showed that the thermal degradation of the unirradiated PLLA and its nanocomposites occurred in only one stage. The activation energies of thermal degradation (E) for irradiated and unirradiated PLLA and its nanocomposites were determined by the Flynn-Wall-Ozawa (FWO) method. The E values of the polymer irradiated with gamma radiation seem to be smaller than those of unirradiated sample due to polymer bond scission. In addition, the calculated G values of the polymer and nanocomposites showed that the polymer structure was less stable when exposed to radiation with increasing % MK10 content.

  10. Different types of degradable vectors from low-molecular-weight polycation-functionalized poly(aspartic acid) for efficient gene delivery.

    PubMed

    Dou, X B; Hu, Y; Zhao, N N; Xu, F J

    2014-03-01

    Poly(aspartic acid) (PAsp) has been employed as the potential backbone for the preparation of efficient gene carriers, due to its low cytotoxicity, good biodegradability and excellent biocompatibility. In this work, the degradable linear or star-shaped PBLA was first prepared via ring-opining polymerization of β-benzyl-L-aspartate N-carboxy anhydride (BLA-NCA) initiated by ethylenediamine (ED) or ED-functionalized cyclodextrin cores. Then, PBLA was functionalized via aminolysis reaction with low-molecular-weight poly(2-(dimethylamino)ethyl methacrylate) with one terminal primary amine group (PDMAEMA-NH2), followed by addition of excess ED or ethanolamine (EA) to complete the aminolysis process. The obtained different types of cationic PAsp-based vectors including linear or star PAsp-PDM-NH2 and PAsp-PDM-OH exhibited good condensation capability and degradability, benefiting gene delivery process. In comparison with gold standard polyethylenimine (PEI, ∼ 25 kDa), the cationic PAsp-based vectors, particularly star-shaped ones, exhibited much better transfection performances. PMID:24388816

  11. Microdialysis unit for molecular weight separation

    SciTech Connect

    Smith, R.D.; Liu, C.

    1999-09-21

    The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, or (4) any combination of (1), (2), and (3).

  12. Microdialysis unit for molecular weight separation

    DOEpatents

    Smith, Richard D.; Liu, Chuanliang

    1999-01-01

    The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations (0-2.5 mM NH4OAc) of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, or (4) any combination of (1), (2), and (3).

  13. Polyelectrolyte Complexes of Low Molecular Weight PEI and Citric Acid as Efficient and Nontoxic Vectors for in Vitro and in Vivo Gene Delivery.

    PubMed

    Giron-Gonzalez, M Dolores; Salto-Gonzalez, Rafael; Lopez-Jaramillo, F Javier; Salinas-Castillo, Alfonso; Jodar-Reyes, Ana Belen; Ortega-Muñoz, Mariano; Hernandez-Mateo, Fernando; Santoyo-Gonzalez, Francisco

    2016-03-16

    Gene transfection mediated by the cationic polymer polyethylenimine (PEI) is considered a standard methodology. However, while highly branched PEIs form smaller polyplexes with DNA that exhibit high transfection efficiencies, they have significant cell toxicity. Conversely, low molecular weight PEIs (LMW-PEIs) with favorable cytotoxicity profiles display minimum transfection activities as a result of inadequate DNA complexation and protection. To solve this paradox, a novel polyelectrolyte complex was prepared by the ionic cross-linking of branched 1.8 kDa PEI with citric acid (CA). This system synergistically exploits the good cytotoxicity profile exhibited by LMW-PEI with the high transfection efficiencies shown by highly branched and high molecular weight PEIs. The polyectrolyte complex (1.8 kDa-PEI@CA) was obtained by a simple synthetic protocol based on the microwave irradiation of a solution of 1.8 kDa PEI and CA. Upon complexation with DNA, intrinsic properties of the resulting particles (size and surface charge) were measured and their ability to form stable polyplexes was determined. Compared with unmodified PEIs the new complexes behave as efficient gene vectors and showed enhanced DNA binding capability associated with facilitated intracellular DNA release and enhanced DNA protection from endonuclease degradation. In addition, while transfection values for LMW-PEIs are almost null, transfection efficiencies of the new reagent range from 2.5- to 3.8-fold to those of Lipofectamine 2000 and 25 kDa PEI in several cell lines in culture such as CHO-k1, FTO2B hepatomas, L6 myoblasts, or NRK cells, simultaneously showing a negligible toxicity. Furthermore, the 1.8 kDa-PEI@CA polyelectrolyte complexes retained the capability to transfect eukaryotic cells in the presence of serum and exhibited the capability to promote in vivo transfection in mouse (as an animal model) with an enhanced efficiency compared to 25 kDa PEI. Results support the polyelectrolyte complex

  14. Polyelectrolyte Complexes of Low Molecular Weight PEI and Citric Acid as Efficient and Nontoxic Vectors for in Vitro and in Vivo Gene Delivery.

    PubMed

    Giron-Gonzalez, M Dolores; Salto-Gonzalez, Rafael; Lopez-Jaramillo, F Javier; Salinas-Castillo, Alfonso; Jodar-Reyes, Ana Belen; Ortega-Muñoz, Mariano; Hernandez-Mateo, Fernando; Santoyo-Gonzalez, Francisco

    2016-03-16

    Gene transfection mediated by the cationic polymer polyethylenimine (PEI) is considered a standard methodology. However, while highly branched PEIs form smaller polyplexes with DNA that exhibit high transfection efficiencies, they have significant cell toxicity. Conversely, low molecular weight PEIs (LMW-PEIs) with favorable cytotoxicity profiles display minimum transfection activities as a result of inadequate DNA complexation and protection. To solve this paradox, a novel polyelectrolyte complex was prepared by the ionic cross-linking of branched 1.8 kDa PEI with citric acid (CA). This system synergistically exploits the good cytotoxicity profile exhibited by LMW-PEI with the high transfection efficiencies shown by highly branched and high molecular weight PEIs. The polyectrolyte complex (1.8 kDa-PEI@CA) was obtained by a simple synthetic protocol based on the microwave irradiation of a solution of 1.8 kDa PEI and CA. Upon complexation with DNA, intrinsic properties of the resulting particles (size and surface charge) were measured and their ability to form stable polyplexes was determined. Compared with unmodified PEIs the new complexes behave as efficient gene vectors and showed enhanced DNA binding capability associated with facilitated intracellular DNA release and enhanced DNA protection from endonuclease degradation. In addition, while transfection values for LMW-PEIs are almost null, transfection efficiencies of the new reagent range from 2.5- to 3.8-fold to those of Lipofectamine 2000 and 25 kDa PEI in several cell lines in culture such as CHO-k1, FTO2B hepatomas, L6 myoblasts, or NRK cells, simultaneously showing a negligible toxicity. Furthermore, the 1.8 kDa-PEI@CA polyelectrolyte complexes retained the capability to transfect eukaryotic cells in the presence of serum and exhibited the capability to promote in vivo transfection in mouse (as an animal model) with an enhanced efficiency compared to 25 kDa PEI. Results support the polyelectrolyte complex

  15. [Effect of Low Molecular Weight Organic Acids on the Chemical Speciation and Activity of Mercury in the Soils of the Water-Level-Fluctuating Zone of the Three Gorges Reservoir].

    PubMed

    You, Rui; Liang, Li; Qin, Cai-qing; Deng, Han; Wang, Ding-yong

    2016-01-15

    To investigate the effect of low molecular weight organic acids ( LMWOA) on the ability of migration and the species of mercury in the soil of the Water-Level-Fluctuating Zone of the Three Gorges Reservoir, citric acid, tartaric acid and oxalic acid were dded into the soil to conduct simulation experiments. The results showed that the percentage of exchangeable mercury increased with the increase of the concentration of citric acid, but the value declined slightly as the concentration of tartaric acid and oxalic acid increased. While all three acids elevated the bioavailability of mercury, which increased with the increase of the concentration of acids. Vhen the concentration of citric acid reached 15 mmol x L(-1), the activation effect was the best. But for oxalic acid and citric acid, 10 mmol x L(-1) was the optimal concentration. In general, the effect of three organic acids on the activation of mercury in the soil followed the trend of citric acid > tartaric acid > oxalic acid. In the soil supplemented with 15 mmol x L(-1) citric acid, the change of mercury pecies was more and more striking with the prolonged incubation, and the conversion did not stop until 14 d, at that time the stomach cid dissolved mercury increased obviously, which was mainly converted from elemental mercury.

  16. [Effect of Low Molecular Weight Organic Acids on the Chemical Speciation and Activity of Mercury in the Soils of the Water-Level-Fluctuating Zone of the Three Gorges Reservoir].

    PubMed

    You, Rui; Liang, Li; Qin, Cai-qing; Deng, Han; Wang, Ding-yong

    2016-01-15

    To investigate the effect of low molecular weight organic acids ( LMWOA) on the ability of migration and the species of mercury in the soil of the Water-Level-Fluctuating Zone of the Three Gorges Reservoir, citric acid, tartaric acid and oxalic acid were dded into the soil to conduct simulation experiments. The results showed that the percentage of exchangeable mercury increased with the increase of the concentration of citric acid, but the value declined slightly as the concentration of tartaric acid and oxalic acid increased. While all three acids elevated the bioavailability of mercury, which increased with the increase of the concentration of acids. Vhen the concentration of citric acid reached 15 mmol x L(-1), the activation effect was the best. But for oxalic acid and citric acid, 10 mmol x L(-1) was the optimal concentration. In general, the effect of three organic acids on the activation of mercury in the soil followed the trend of citric acid > tartaric acid > oxalic acid. In the soil supplemented with 15 mmol x L(-1) citric acid, the change of mercury pecies was more and more striking with the prolonged incubation, and the conversion did not stop until 14 d, at that time the stomach cid dissolved mercury increased obviously, which was mainly converted from elemental mercury. PMID:27078955

  17. Purified membrane and soluble folate binding proteins from cultured KB cells have similar amino acid compositions and molecular weights but differ in fatty acid acylation.

    PubMed Central

    Luhrs, C A; Pitiranggon, P; da Costa, M; Rothenberg, S P; Slomiany, B L; Brink, L; Tous, G I; Stein, S

    1987-01-01

    A membrane-associated folate binding protein (FBP) and a soluble FBP, which is released into the culture medium, have been purified from human KB cells using affinity chromatography. By NaDodSO4/PAGE, both proteins have an apparent Mr of approximately 42,000. However, in the presence of Triton X-100, the soluble FBP eluted from a Sephadex G-150 column with an apparent Mr of approximately 40,000 (similar to NaDodSO4/PAGE) but the membrane-associated FBP eluted with an apparent Mr of approximately 160,000, indicating that this species contains a hydrophobic domain that interacts with the detergent micelles. The amino acid compositions of both forms of FBP were similar, especially with respect to the apolar amino acids. In addition, the 18 amino acids at the amino termini of both proteins were identical. The membrane FBP, following delipidation with chloroform/methanol, contained 7.1 mol of fatty acid per mol of protein, of which 4.7 mol was amide-linked and 2.4 mol was ester-linked. The soluble FBP contained only 0.05 mol of fatty acid per mol of protein. These studies indicate that the membrane FBP of KB cells contains covalently bound fatty acids that may serve to anchor the protein in the cell membrane. Images PMID:3476960

  18. Purified membrane and soluble folate binding proteins from cultured KB cells have similar amino acid compositions and molecular weights but differ in fatty acid acylation

    SciTech Connect

    Luhrs, C.A.; Pitiranggon, P.; Costa, M.D.; Rothenberg, S.P.; Slomiany, B.L.; Brink, L.; Tous, G.I.; Stein, S.

    1987-09-01

    A membrane-associated folate binding protein (FBP) and a soluble FBP, which is released into the culture medium, have been purified from human KB cells using affinity chromatography. By NaDodSO/sub 4/PAGE, both proteins have an apparent M/sub r/ of approx. 42,000. However, in the presence of Triton X-100, the soluble FBP eluted from a Sephadex G-150 column with an apparent M/sub r/ of approx. 40,000 (similar to NaDodSO/sub 4/PAGE) but the membrane-associated FBP eluted with an apparent M/sub r/ of approx. = 160,000, indicating that this species contains a hydrophobic domain that interacts with the detergent micelles. The amino acid compositions of both forms of FBP were similar, especially with respect to the apolar amino acids. In addition, the 18 amino acids at the amino termini of both proteins were identical. The membrane FBP, following delipidation with chloroformmethanol, contained 7.1 mol of fatty acid per mol of protein, of which 4.7 mol was amide-linked and 2.4 mol was ester-linked. The soluble FBP contained only 0.05 mol of fatty acid per mol of protein. These studies indicate that the membrane FBP of KB cells contains covalently bound fatty acids that may serve to anchor the protein in the cell membrane.

  19. Evaluation of in vitro drug release, pH change, and molecular weight degradation of poly(L-lactic acid) and poly(D,L-lactide-co-glycolide) fibers.

    PubMed

    Crow, B B; Borneman, A F; Hawkins, D L; Smith, G M; Nelson, K D

    2005-01-01

    Biodegradable fibers of poly(L-lactic acid) (PLLA) and poly(D,L-lactide-co-glycolide) (PLGA) that encapsulated a water-soluble drug were created by a patented technique consisting of wet-spinning a water-in-oil emulsion. These fibers are 2.4% by mass drug, which is slowly released, making these fibers potential candidates for implantation as drug delivery devices and/or tissue-engineering substrates. Drug release kinetics and changes in molecular weight were investigated over time. This study demonstrated that drug release rates and molecular weight degradation are a function of the amount of aqueous phase added as an emulsion during fabrication. The type of polymer used (PLLA or PLGA) determines the molecular weight degradation rates, but has little effect on drug release kinetics.

  20. Combination chemotherapy of doxorubicin, all-trans retinoic acid and low molecular weight heparin based on self-assembled multi-functional polymeric nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhang, Ting; Xiong, Hui; Zohra Dahmani, Fatima; Sun, Li; Li, Yuanke; Yao, Li; Zhou, Jianping; Yao, Jing

    2015-04-01

    Based on the complementary effects of doxorubicin (DOX), all-trans retinoic acid (ATRA) and low molecular weight heparin (LMWH), the combination therapy of DOX, ATRA and LMWH was expected to exert the enhanced anti-tumor effects and reduce the side effects. In this study, amphiphilic LMWH-ATRA conjugate was synthesized for encapsulating the DOX. In this way, DOX, ATRA and LMWH were assembled into a single nano-system by both chemical and physical modes to obtain a novel anti-tumor targeting drug delivery system that can realize the simultaneous delivery of multiple drugs with different properties to the tumor. LMWH-ATRA nanoparticles exhibited good loading capacities for DOX with excellent physico-chemical properties, good biocompatibility, and good differentiation-inducing activity and antiangiogenic activity. The drug-loading capacity was up to 18.7% with an entrapment efficiency of 78.8%. It was also found that DOX-loaded LMWH-ATRA nanoparticles (DHR nanoparticles) could be efficiently taken up by tumor cells via endocytic pathway, and mainly distributed in cytoplasm at first, then transferred into cell nucleus. Cell viability assays suggested that DHR nanoparticles maintained the cytotoxicity effect of DOX on MCF-7 cells. Moreover, the in vivo imaging analysis indicated that DiR-loaded LMWH-ATRA nanoparticles could target the tumor more effectively as compared to free DiR. Furthermore, DHR nanoparticles possessed much higher anticancer activity and reduced side effects compared to free drugs solution. These results suggested that DHR nanoparticles could be considered as a promising targeted delivery system for combination cancer chemotherapy with lower adverse effects.

  1. In vivo hair growth promotion effects of ultra-high molecular weight poly-γ-glutamic acid from Bacillus subtilis (Chungkookjang).

    PubMed

    Choi, Jae-Chul; Uyama, Hiroshi; Lee, Chul-Hoon; Sung, Moon-Hee

    2015-03-01

    We investigated the effect of ultra-high molecular weight poly-γ-glutamic acid (UHMW γ-PGA) on hair loss in vitro and in vivo. 5-Alpha reductase is an enzyme that metabolizes the male hormone testosterone into dihydrotestosterone. By performing an in vitro experiment to analyze the inhibitory effects of UHMW γ-PGA on 5-alpha reductase activity, we determined that UHMW γ-PGA did in fact inhibit 5-alpha reductase activity, indicating the use of UHMW γ-PGA as a potential 5-alpha reductase inhibitor in the treatment of men with androgenetic alopecia. To evaluate the promotion of hair growth in vivo, we topically applied UHMW γ-PGA and minoxidil on the shaved dorsal skin of telogenic C57BL/6 mice for 4 weeks. At 4 weeks, the groups treated with UHMW γ-PGA showed hair growth on more than 50% of the shaved skin, whereas the control group showed less hair growth. To investigate the progression of hair follicles in the hair cycle, hematoxylin and eosin staining was performed. Histological observations revealed that the appearance of hair follicles was earlier in the UHMW γ-PGA-treated group than in the control group. The number of hair follicles on the relative area of shaved skin in the UHMW γ-PGA-treated group was higher than that observed on the shaved skin in the control group. These results indicate that UHMW γ-PGA can promote hair growth by effectively inducing the anagen phase in telogenic C57BL/6 mice. PMID:25502822

  2. Effects of cadmium alone and in combination with low molecular weight chitosan on metallothionein, glutathione-S-transferase, acid phosphatase, and ATPase of freshwater crab Sinopotamon yangtsekiense.

    PubMed

    Li, Ruijin; Zhou, Yanying; Wang, Lan; Ren, Guorui; Zou, Enmin

    2014-03-01

    Cadmium (Cd) is an environmental contaminant showing a variety of deleterious effects, including the potential threat for the ecological environment and human health via food chains. Low molecular weight chitosan (LMWC) has been demonstrated to be an effective antioxidant. Metallothionein (MT) mRNA levels and activities of glutathione-S-transferase (GST), superoxide dismutase (SOD), acid phosphatase (ACP), Na(+),K(+)-ATPase, and Ca(2+)-ATPase as well as malondialdehyde (MDA) contents in the gills of the freshwater crab Sinopotamon yangtsekiense were analyzed in vivo in order to determine the injury of Cd exposure on the gill tissues as well as the protective effect of LMWC against this injury. The results showed that there was an apparent accumulation of Cd in the gills, which was lessened by the presence of LMWC. Moreover, Cd(2+) significantly increased the gill MT mRNA levels, ACP activity and MDA content while decreasing the activities of SOD, GST, Na(+),K(+)-ATPase, and Ca(2+)-ATPase in the crabs relative to the control. Cotreatment with LMWC reduced the levels of MT mRNA and ACP but raised the activities of GST, Na(+),K(+)-ATPase, and Ca(2+)-ATPase in gill tissues compared with the crabs exposed to Cd(2+) alone. These results suggest that LMWC may exert its protective effect through chelating Cd(2+) to form LMWC-Cd(2+) complex, elevating the antioxidative activities of GST, Na(+),K(+)-ATPase, and Ca(2+)-ATPase as well as alleviating the stress pressure on MT and ACP, consequently protecting the cell from the adverse effects of Cd.

  3. Coordination nature of aluminum (oxy)hydroxides formed under the influence of low molecular weight organic acids and a soil humic acid studied by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Xu, R. K.; Hu, Y. F.; Dynes, J. J.; Zhao, A. Z.; Blyth, R. I. R.; Kozak, L. M.; Huang, P. M.

    2010-11-01

    Organic ligands in the environment hinder the formation of crystalline Al precipitation products by perturbing the hydrolytic and polymeric reactions of Al resulting in the formation of short-range ordered (SRO) mineral colloids with varying degrees of crystallinity. However, the effect of these ligands on the mechanisms of their formation and nature of the transformation products of Al (oxy)hydroxides at the atomic and molecular levels is not well understood. In this study, the coordination structure of Al in Al (oxy)hydroxides formed under the influence of varying concentrations of low molecular weight (LMW) organic acids such as citric, malic, salicylic and acetic acids and a humic acid (HA) was investigated with X-ray absorption near edge structure (XANES) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction analysis. The Al K- and L-edge XANES spectra showed that with increasing LMW organic acid concentration the coordination number of Al changed from 6-fold to a mixture of 4- and 6-fold, except for acetate as acetate was unable to perturb the formation of Al (oxy)hydroxides at the acetate/Al molar ratio (MR) = 0.1. The proportion of 4-fold to 6-fold coordinated Al in the Al precipitation products depended on the structure and functionality of the LMW organic acids. The incorporation of the LMW organic acid into the network structure of Al (oxy)hydroxides prevented the formation of sheets/inter-layer H-bonding that was required for the formation of crystalline Al (oxy)hydroxides. The HA used in this study only slightly perturbed the crystallization of the Al (oxy)hydroxides at the concentrations used. The Al K-edge data showed that Al coordination number had not been altered in the presence of HA. The findings obtained in the present study are of fundamental significance in understanding the physicochemical behavior of soils and sediments, and their relation to the accumulation and transport of nutrients and pollutants in the

  4. Rheological investigation of highly filled polymers: Effect of molecular weight

    NASA Astrophysics Data System (ADS)

    Hnatkova, Eva; Hausnerova, Berenika; Hales, Andrew; Jiranek, Lukas; Vera, Juan Miguel Alcon

    2015-04-01

    The paper deals with rheological properties of highly filled polymers used in powder injection molding. Within the experimental framework seven PIM feedstocks based on superalloy Inconel 718 powder were prepared. Each feedstock contains the fixed amount of powder loading and the same composition of binder system consisting of three components: polyethylene glycol (PEG) differing in molecular weight, poly (methyl methacrylate) (PMMA) and stearic acid (SA). The aim is to investigate the influence of PEG's molecular weight on the flow properties of feedstocks. Non-Newtonian indices, representing the shear rate sensitivity of the feedstocks, are obtained from a polynomial fit, and found to vary within measured shear rates range from 0.2 to 0.8. Temperature effect is considered via activation energies, showing decreasing trend with increasing of molecular weight of PEG (except of feedstock containing 1,500 g.mol-1 PEG).

  5. Low-molecular-weight organic acids in the Tibetan Plateau: Results from one-year of precipitation samples at the SET station

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Kang, Shichang; Sun, Jimin; Wan, Xin; Wang, Yongjie; Gao, Shaopeng; Cong, Zhiyuan

    2014-04-01

    Background atmospheric organic acids: formic (F), acetic (A), oxalic (O), and methanesulfonic (MSA, abbreviated to M) acids in the southern Tibetan Plateau (TP), were determined in one-year of precipitation measurements at a remote alpine station. These organic acids were dominated by oxalic (volume-weighted mean of 0.51 μmol l-1)/formic acid (0.38 μmol l-1), followed by acetic acid (0.20 μmol l-1) and MSA (0.10 μmol l-1). Their levels were comparable with those from other remote sites, while they were lower than those found in populated areas. The South Asian monsoon is responsible for the seasonal variation of organic acid concentration: a relative abundance of MSA and lower concentrations of other organic acids (by the dilution effect) in the monsoon season, while opposite in the non-monsoon season. Diverse sources were identified by principal component analysis combined with the corresponding tracers. These were anthropogenic disturbances (which explain 41% of the variance), marine emission (24%), and biogenic emission (16%). Moreover, the variances of F/A, M/(F + A), and O/(F + A) in monsoonal versus non-monsoonal samples, were involved with the changes of sources. Furthermore, these chemical indexes suggest that active photochemistry over the TP was significant for the production of organic acids and consequently enhanced the ratios of M/(F + A) and O/(F + A) in monsoonal rainfalls. The elevated organic compounds within the ascending tropical moisture imply potential significances for the secondary formation of organic acids in the high-altitude and the changes of the Asian monsoon.

  6. Equivalent weight of humic acid from peat

    USGS Publications Warehouse

    Pommer, A.M.; Breger, I.A.

    1960-01-01

    By means of discontinuous titration, the equivalent weight of humic acid isolated from a peat was found to increase from 144 to 183 between the third and fifty-second day after the humic acid was dissolved. Infra-red studies showed that the material had probably condensed with loss of carbonyl groups. ?? 1960.

  7. Influence of Molecular Weight and Degree of Deacetylation of Low Molecular Weight Chitosan on the Bioactivity of Oral Insulin Preparations

    PubMed Central

    Qinna, Nidal A.; Karwi, Qutuba G.; Al-Jbour, Nawzat; Al-Remawi, Mayyas A.; Alhussainy, Tawfiq M.; Al-So’ud, Khaldoun A.; Al Omari, Mahmoud M. H.; Badwan, Adnan A.

    2015-01-01

    The objective of the present study was to prepare and characterize low molecular weight chitosan (LMWC) with different molecular weight and degrees of deacetylation (DDA) and to optimize their use in oral insulin nano delivery systems. Water in oil nanosized systems containing LMWC-insulin polyelectrolyte complexes were constructed and their ability to reduce blood glucose was assessed in vivo on diabetic rats. Upon acid depolymerization and testing by viscosity method, three molecular weights of LMWC namely, 1.3, 13 and 18 kDa were obtained. As for the DDA, three LMWCs of 55%, 80% and 100% DDA were prepared and characterized by spectroscopic methods for each molecular weight. The obtained LMWCs showed different morphological and in silico patterns. Following complexation of LMWCs with insulin, different aggregation sizes were obtained. Moreover, the in vivo tested formulations showed different activities of blood glucose reduction. The highest glucose reduction was achieved with 1.3 kDa LMWC of 55% DDA. The current study emphasizes the importance of optimizing the molecular weight along with the DDA of the incorporated LMWC in oral insulin delivery preparations in order to ensure the highest performance of such delivery systems. PMID:25826718

  8. Influence of molecular weight and degree of deacetylation of low molecular weight chitosan on the bioactivity of oral insulin preparations.

    PubMed

    Qinna, Nidal A; Karwi, Qutuba G; Al-Jbour, Nawzat; Al-Remawi, Mayyas A; Alhussainy, Tawfiq M; Al-So'ud, Khaldoun A; Al Omari, Mahmoud M H; Badwan, Adnan A

    2015-03-27

    The objective of the present study was to prepare and characterize low molecular weight chitosan (LMWC) with different molecular weight and degrees of deacetylation (DDA) and to optimize their use in oral insulin nano delivery systems. Water in oil nanosized systems containing LMWC-insulin polyelectrolyte complexes were constructed and their ability to reduce blood glucose was assessed in vivo on diabetic rats. Upon acid depolymerization and testing by viscosity method, three molecular weights of LMWC namely, 1.3, 13 and 18 kDa were obtained. As for the DDA, three LMWCs of 55%, 80% and 100% DDA were prepared and characterized by spectroscopic methods for each molecular weight. The obtained LMWCs showed different morphological and in silico patterns. Following complexation of LMWCs with insulin, different aggregation sizes were obtained. Moreover, the in vivo tested formulations showed different activities of blood glucose reduction. The highest glucose reduction was achieved with 1.3 kDa LMWC of 55% DDA. The current study emphasizes the importance of optimizing the molecular weight along with the DDA of the incorporated LMWC in oral insulin delivery preparations in order to ensure the highest performance of such delivery systems.

  9. Bioavailable concentrations of germanium and rare earth elements in soil as affected by low molecular weight organic acids and root exudates

    NASA Astrophysics Data System (ADS)

    Wiche, Oliver; Székely, Balázs; Kummer, Nicolai-Alexeji; Heinemann, Ute; Tesch, Silke; Heilmeier, Hermann

    2014-05-01

    Availability of elements in soil to plant is generally dependent on the solubility and mobility of elements in soil solution which is controlled by soil, elemental properties and plant-soil interactions. Low molecular organic acids or other root exudates may increase mobility and availability of certain elements for plants as an effect of lowering pH in the rhizosphere and complexation. However, these processes take place in a larger volume in soil, therefore to understand their nature, it is also important to know in which layers of the soil what factors modify these processes. In this work the influence of citric acid and root exudates of white lupin (Lupinus albus L.) on bioavailable concentrations of germanium, lanthan, neodymium, gadolinium and erbium in soil solution and uptake in root and shoot of rape (Brassica napus L.), comfrey (Symphytum officinale L.), common millet (Panicum milliaceum L.) and oat (Avena sativa L.) was investigated. Two different pot experiments were conducted: (1) the mentioned plant species were treated with nutrient solutions containing various amount of citric acid; (2) white lupin was cultivated in mixed culture (0 % lupin, 33 % lupin) with oat (Avena sativa L.) and soil solution was obtained by plastic suction cups placed at various depths. As a result, addition of citric acid significantly increased germanium concentrations in plant tissue of comfrey and rape and increased translocation of germanium, lanthan, neodymium, gadolinium and erbium from root to shoot. The cultivation of white lupin in mixed culture with oat led to significantly higher concentrations of germanium and increasing concentrations of lanthan, neodymium, gadolinium and erbium in soil solution and aboveground plant tissue. In these pots concentrations of citric acid in soil solution were significantly higher than in the control. The results show, that low molecular organic acids exuded by plant roots are of great importance for the mobilization of germanium

  10. Calculation of molecular weights of humic substances from colligative data: Application to aquatic humus and its molecular size fractions

    NASA Astrophysics Data System (ADS)

    Reuter, J. H.; Perdue, E. M.

    1981-11-01

    A rigorous mathematical expression for the dependence of colligative properties on acid dissociation of water soluble humic substances is presented. New data for number average molecular weights of a river derived humic material and its gel permeation Chromatographic fractions are compared with M¯n values obtained by a reevaluation of previously published experimental observations on soil and water fulvic acids. The results reveal a remarkable similarity of fulvic acids from widely different sources with respect to number-average molecular weight.

  11. Biocompatible composites of ultrahigh molecular weight polyethylene

    NASA Astrophysics Data System (ADS)

    Panin, S. V.; Kornienko, L. A.; Suan, T. Nguen; Ivanova, L. P.; Korchagin, M. A.; Chaikina, M. V.; Shilko, S. V.; Pleskachevskiy, Yu. M.

    2015-10-01

    Mechanical and tribotechnical characteristics of biocompatible, antifriction and extrudable composites based on ultrahigh molecular weight polyethylene (UHMWPE) as well as hybrid matrix "UHMWPE + PTFE" with biocompatible hydroxyapatite filler under the dry friction and boundary lubrication were investigated. A comparative analysis of effectiveness of adding the hydroxyapatite to improve the wear resistance of composites based on these two matrices was performed. It is shown that the wear intensity of nanocomposites based on the hybrid matrix is lower than that for the composites based on pure UHMWPE. Possibilities of using the composites of the polymer "UHMWPE-PTFE" mixture as a material for artificial joints implants are discussed.

  12. Polymer Molecular Weight Analysis by [Superscript 1]H NMR Spectroscopy

    ERIC Educational Resources Information Center

    Izunobi, Josephat U.; Higginbotham, Clement L.

    2011-01-01

    The measurement and analysis of molecular weight and molecular weight distribution remain matters of fundamental importance for the characterization and physical properties of polymers. Gel permeation chromatography (GPC) is the most routinely used method for the molecular weight determination of polymers whereas matrix-assisted laser…

  13. Determinations of molecular weight and molecular weight distribution of high polymers by the rheological properties

    NASA Technical Reports Server (NTRS)

    Huang, J. Y.; Hou, T. H.; Tiwari, S. N.

    1989-01-01

    Several methods are reviewed by which the molecular weight (MW) and the molecular weight distribution (MWD) of polymeric material were determined from the rheological properties. A poly(arylene ether) polymer with six different molecular weights was used in this investigation. Experimentally measured MW and MWD were conducted by GPC/LALLS (gel permeation chromatography/low angle laser light scattering), and the rheological properties of the melts were measured by a Rheometric System Four rheometer. It was found that qualitative information of the MW and MWD of these polymers could be derived from the viscoelastic properties, with the methods proposed by Zeichner and Patel, and by Dormier et al., by shifting the master curves of the dynamic storage modulus, G', and the loss modulus, G'', along the frequency axis. Efforts were also made to calculate quantitative profiles of MW and MWD for these polymers from their rheological properties. The technique recently proposed by Wu was evaluated. It was found that satisfactory results could only be obtained for polymers with single modal distribution in the molecular weight.

  14. Composition of the amino acid and amino sugar for molecular weight fractions of hot-water extractable soil organic matters from soils with plant residue compost or mineral fertilization

    NASA Astrophysics Data System (ADS)

    Moriizumi, M.; Matsunaga, T.; Uezono, I.; Kato, N.

    2009-04-01

    The hot-water extractable organic nitrogen is well known as a laboratory index of mineralizable nitrogen. This available nitrogen is indispensable for growth of plants because of being absorbed in crops. We measured the composition of the amino acid and amino sugar for molecular weight fractions in hot-water extractable organic matters to understand the source of the available nitrogen in soils inserted a compost. Two soil samples were collected from fields (Soil Type; Andosol) in National Agricultural Research Center in Tsukuba, Japan. A plant residue compost of 2 kga-1y-1 during 25 year has been applied to a soil and another soil was under the mineral fertilization. Organic matters were extracted from the soils of 3 g in the water of 50 ml at 80 degree centigrade for16 hours. The molecular size distribution of the hot-water extractable organic matters was analyzed by HPSCE (column YMC Diol-120, elution; 50mM phosphate buffer under pH=7.0, flow rate 1 mlmin-1), and 20 fractions were collected at regular intervals in the retention time. The chromatograms were monitored under the absorbance at 280 nm and fluorescence intensity at Ex.280 nm: Em.330nm. The concentrations of the 15 amino acids and three amino sugars (muramic acid, glucosamine, and galactosamine) for the molecule weight fractions were measured by HPLC as o-phthaldialdehyde (OPA) derivatives after the vapor HCl hydrolysis. Organic nitrogen concentrations of the hot-water extractable organic matters in the soil inserted the compost (C-soil) and the mineral fertilization soil (M-soil) were 133 and 35 mgkg-1, respectively. The extracted organic matters had the variable molecule weight (103- 104 Da). The concentrations of the amino acid and amino sugar of organic nitrogen in the C-soil were higher than those in the M-soil in all fractions. The fractions were classified into 3 groups (LW, MW, and SW) based on the molecule weight and spectroscopic characteristics. Each group had unique composition of the amino

  15. Unexpected molecular weight effect in polymer nanocomposites

    DOE PAGES

    Cheng, Shiwang; Holt, Adam P.; Wang, Huiqun; Fan, Fei; Bocharova, Vera; Martin, Halie J.; Etampawala, Thusitha N.; White, Benjamin Tyler; Saito, Tomonori; Kang, Nam -Goo; et al

    2016-01-22

    Here, the properties of the interfacial layer between the polymer matrix and nanoparticles largely determine the macroscopic properties of polymer nanocomposites (PNCs). Although the static thickness of the interfacial layer was found to increase with the molecular weight (MW), the influence of MW on segmental relaxation and the glass transition in this layer remains to be explored. In this Letter, we show an unexpected MW dependence of the interfacial properties in PNC with attractive polymer-nanoparticle interactions: the thickness of the interfacial layer with hindered segmental relaxation decreases as MW increases, in sharp constrast to theoretical predictions. Further analyses reveal amore » reduction in mass density of the interfacial layer with increasing MW, which can explain these unexpected dynamic effects. Our observations call for a significant revision of the current understandings of PNCs and suggest interesting ways to tailor their properties.« less

  16. PolyPEGA with predetermined molecular weights from enzyme-mediated radical polymerization in water.

    PubMed

    Ng, Yeap-Hung; di Lena, Fabio; Chai, Christina L L

    2011-06-14

    The preparation of acrylic polymers with predetermined molecular weights using metalloenzymes as catalysts, ascorbic acid as reducing agent and alkyl halides as initiators is reported. The mechanism of polymerization resembles an ARGET ATRP process. PMID:21552589

  17. Soluble, High Molecular Weight Polysilsesquioxanes with Carboxylate Functionalities

    SciTech Connect

    RAHIMIAN,KAMYAR; LOY,DOUGLAS A.; WHEELER,DAVID R.

    2000-07-14

    Trialkoxysilyl-containing monomers of the type (RO){sub 3}Si(CH{sub 2}){sub 3}C(O)OtBu (R = Me, Et) were prepared by hydrosilation of the corresponding vinylic tert-butyl esters CH{sub 3}CHCH{sub 2}C(O)OtBu. Acid- or base-catalyzed polymerization of the monomers leads to very high molecular weight polymers with relatively narrow polydispersities. The polymerization results in complete condensation of the alkoxy groups while the tert-butyl ester functionality remains fully intact. Partial or full deprotection of the tert-butyl group can easily be achieved to yield the corresponding carboxylic acid polymers. The ester and carboxylic acid functionalities of these new materials allow for their potential use in a variety of applications such as scavenging of heavy metals.

  18. Structure, subunit composition, and molecular weight of RD-114 RNA.

    PubMed Central

    Kung, H J; Bailey, J M; Davidson, N; Nicolson, M O; McAllister, R M

    1975-01-01

    The properties and subunit composition of the RNA extracted from RD-114 virions have been studied. The RNA extracted from the virion has a sedimentation coefficient of 52S in a nondenaturing aqueous electrolyte. The estimated molecular weight by sedimentation in nondenaturing and weakly denaturing media is in the range 5.7 X 10(6) to 7.0 X 10(6). By electron microscopy, under moderately denaturing conditions, the 52S molecule is seen to be an extended single strand with a contour length of about 4.0 mum corresponding to a molecular weight of 5.74 X 10(6). It contains two characteristic secondary structure features: (i) a central Y- or T-shaped structure (the rabbit ears) with a molecular weight of 0.3 X 10(6), (ii) two symmetreically disposed loops on each side of and at equal distance from the center. The 52S molecule consists of two half-size molecules, with molecular weight 2.8 X 10(6), joined together within the central rabbit ears feature. Melting of the rabbit ears with concomitant dissociation of the 52S molecule into subunits, has been caused by either one of two strongly denaturing treatments: incubation in a mixture of CH3HgOH and glyoxal at room temperature, or thermal dissociation in a urea-formamide solvent. When half-size molecules are quenched from denaturing temperatures, a new off-center secondary structure feature termed the branch-like structure is seen. The dissociation behavior of the 52S complex and the molecular weight of the subunits have been confirmed by gel electrophoresis studies. The loop structures melt at fairly low temperatures; the dissociation of the 52S molecule into its two subunits occurs at a higher temperature corresponding to a base composition of about 63% guanosine plus cytosine. Polyadenylic acid mapping by electron microscopy shows that the 52S molecule contains two polyadenylic acid segments, one at each end. It thus appears that 52S RD-114 RNA consists of two 2.8 X 10(6) dalton subunits, each with a characteristic

  19. Effect of heavy metals and organic matter on root exudates (low molecular weight organic acids) of herbaceous species: An assessment in sand and soil conditions under different levels of contamination.

    PubMed

    Montiel-Rozas, M M; Madejón, E; Madejón, P

    2016-09-01

    Bioavailability of heavy metals can be modified by different root exudates. Among them, low molecular weight organic acids (LMWOAs) play an important role in this process. Three plant species (Poa annua, Medicago polymorpha and Malva sylvestris), potentially used for phytoremediation, have been assessed for both metal uptake and LMWOAs excretion in contaminated environments with different concentrations of Cd, Cu and Zn. The experiments have been carried out in washed sand and in three contaminated soils where two organic amendments were added (biosolid compost and alperujo compost). The most abundant LMWOAs excreted by all studied plants were oxalic and malic acids, although citric and fumaric acids were also detected. The general tendency was that plants responded to an increase of heavy metal stress releasing higher amounts of LMWOAs. This is an efficient exclusion mechanism reducing the metal uptake and allowing the plant growth at high levels of contamination. In the experiment using wash sand as substrate, the organic acids composition and quantity depended mainly on plant species and metal contamination. M. polymorpha was the species that released the highest concentrations of LMWOAs, both in sand and in soils with no amendment addition, whereas a decrease of these acids was observed with the addition of amendments. Our results established a clear effect of organic matter on the composition and total amount of LMWOAs released. The increase of organic matter and nutrients, through amendments, improved the soil quality reducing phytotoxicity. As a result, organic acids exudates decreased and were solely composed of oxalic acid (except for M. polymorpha). The release of LMWOAs has proved to be an important mechanism against heavy metal stress, unique to each species and modifiable by means of organic amendment addition. PMID:27267743

  20. Aluminium Uptake and Translocation in Al Hyperaccumulator Rumex obtusifolius Is Affected by Low-Molecular-Weight Organic Acids Content and Soil pH

    PubMed Central

    Vondráčková, Stanislava; Száková, Jiřina; Drábek, Ondřej; Tejnecký, Václav; Hejcman, Michal; Müllerová, Vladimíra; Tlustoš, Pavel

    2015-01-01

    Background and Aims High Al resistance of Rumex obtusifolius together with its ability to accumulate Al has never been studied in weakly acidic conditions (pH > 5.8) and is not sufficiently described in real soil conditions. The potential elucidation of the role of organic acids in plant can explain the Al tolerance mechanism. Methods We established a pot experiment with R. obtusifolius planted in slightly acidic and alkaline soils. For the manipulation of Al availability, both soils were untreated and treated by lime and superphosphate. We determined mobile Al concentrations in soils and concentrations of Al and organic acids in organs. Results Al availability correlated positively to the extraction of organic acids (citric acid < oxalic acid) in soils. Monovalent Al cations were the most abundant mobile Al forms with positive charge in soils. Liming and superphosphate application were ambiguous measures for changing Al mobility in soils. Elevated transport of total Al from belowground organs into leaves was recorded in both lime-treated soils and in superphosphate-treated alkaline soil as a result of sufficient amount of Ca available from soil solution as well as from superphosphate that can probably modify distribution of total Al in R. obtusifolius as a representative of “oxalate plants.” The highest concentrations of Al and organic acids were recorded in the leaves, followed by the stem and belowground organ infusions. Conclusions In alkaline soil, R. obtusifolius is an Al-hyperaccumulator with the highest concentrations of oxalate in leaves, of malate in stems, and of citrate in belowground organs. These organic acids form strong complexes with Al that can play a key role in internal Al tolerance but the used methods did not allow us to distinguish the proportion of total Al-organic complexes to the free organic acids. PMID:25880431

  1. Recovery of petroleum with chemically treated high molecular weight polymers

    SciTech Connect

    Gibb, C.L.; Rhudy, J.S.

    1980-11-18

    Plugging of reservoirs with high molecular weight polymers, e.g. Partially hydrolyzed polyacrylamide, is overcome by chemically treating a polymer having an excessively high average molecular weight prior to injection into a reservoir with an oxidizing chemical, e.g. sodium hypochlorite, and thereafter incorporating a reducing chemical, e.g., sodium sulfite, to stop degradation of the polymer when a desired lower average molecular weight and flooding characteristics are attained.

  2. Low-molecular-weight xylanase from Trichoderma viride

    SciTech Connect

    Ujiie, M.; Roy, C.; Yaguchi, M. )

    1991-06-01

    An endo-1,4-{beta}-xylanase (1,4-{beta}-D-xylan xylanohydrolase, EC 3.2.1.8) has been isolated from a commercial proparation of Trichoderma viride. The molecular weight was 22,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the pI value was 9.3. The xylanase was a true xylanase without cellulase activity. When the N-terminal amino acid sequence of thew first 50 residues was compared with that of a xylanase from Schizophyllum commune, strong evidence for homology was found, with more than 50% amino acid identity. T. viride xylanase also possessed extensive identity with a proposed amino-terminal consensus sequence of xylanases from bacteria.

  3. Microbial detection with low molecular weight RNA

    NASA Technical Reports Server (NTRS)

    Kourentzi, K. D.; Fox, G. E.; Willson, R. C.

    2001-01-01

    The need to monitor microorganisms in the environment has increased interest in assays based on hybridization probes that target nucleic acids (e.g., rRNA). We report the development of liquid-phase assays for specific bacterial 5S rRNA sequences or similarly sized artificial RNAs (aRNAs) using molecular beacon technology. These beacons fluoresce only in the presence of specific target sequences, rendering as much as a 27-fold fluorescence enhancement. The assays can be used with both crude cell lysates and purified total RNA preparations. Minimal sample preparation (e.g., heating to promote leakage from cells) is sufficient to detect many Gram-negative bacteria. Using this approach it was possible to detect an aRNA-labeled Escherichia coli strain in the presence of a large background of an otherwise identical E. coli strain. Finally, by using a longer wavelength carboxytetramethylrhodamine beacon it was possible to reduce the fraction of the signal due to cellular autofluorescence to below 0.5%.

  4. Microbial detection with low molecular weight RNA.

    PubMed

    Kourentzi, K D; Fox, G E; Willson, R C

    2001-12-01

    The need to monitor microorganisms in the environment has increased interest in assays based on hybridization probes that target nucleic acids (e.g., rRNA). We report the development of liquid-phase assays for specific bacterial 5S rRNA sequences or similarly sized artificial RNAs (aRNAs) using molecular beacon technology. These beacons fluoresce only in the presence of specific target sequences, rendering as much as a 27-fold fluorescence enhancement. The assays can be used with both crude cell lysates and purified total RNA preparations. Minimal sample preparation (e.g., heating to promote leakage from cells) is sufficient to detect many Gram-negative bacteria. Using this approach it was possible to detect an aRNA-labeled Escherichia coli strain in the presence of a large background of an otherwise identical E. coli strain. Finally, by using a longer wavelength carboxytetramethylrhodamine beacon it was possible to reduce the fraction of the signal due to cellular autofluorescence to below 0.5%.

  5. Low-molecular-weight heparins and angiogenesis.

    PubMed

    Norrby, Klas

    2006-02-01

    The involvement of the vascular system in malignancy encompasses not only angiogenesis, but also systemic hypercoagulability and a pro-thrombotic state, and there is increasing evidence that pathways of blood coagulation and angiogenesis are reciprocally linked. In fact, cancer atients often display hypercoagulability resulting in markedly increased thromboembolism, which requires anti-coagulant treatment using heparins, for example. Clinical trials reveal that treatment with various low-molecular-weight heparins (LMWHs) improves the survival time in cancer patients receiving chemotherapy compared with those receiving unfractionated standard heparin (UFH) or no heparin treatment, as well as in cancer patients receiving LMWH as thrombosis prophylaxis during primary surgery. This anti-tumor effect of the heparins appears to be unrelated to their anti-coagulant activity, but the mechanisms involved are not fully understood. Tumor growth and spread are dependent on angiogenesis and it is noteworthy that the most potent endogenous pro- and anti-angiogenic factors are heparin-binding proteins that may be affected by systemic treatment with heparins. Heparin and other glycosaminoglycans play a role in vascular endothelial cell function, as they are able to modulate the activities of angiogenic growth factors by facilitating the interaction with their receptor and promoting receptor activation. To date, preclinical studies have demonstrated that only LMWH fragments produced by the heparinase digestion of UFH, i.e. tinzaparin, exert anti-angiogenic effects in any type of tissue in vivo. These effects are fragment-mass-specific and angiogenesis-type-specific. Data on the effect of various LMWHs and UFH on endothelial cell capillary tube formation and proliferation in vitro are also presented. We hope that this paper will stimulate and facilitate future research designed to elucidate whether the anti-angiogenic or anti-tumor effects of commercial LMWHs in their own right are

  6. Large Molecular Weight Polymer Solar Cells with Strong Chain Alignment Created by Nanoimprint Lithography.

    PubMed

    Yang, Yi; Mielczarek, Kamil; Zakhidov, Anvar; Hu, Walter

    2016-03-23

    In this work, strong chain alignment in large molecular weight polymer solar cells is for the first time demonstrated by nanoimprint lithography (NIL). The polymer crystallizations in nonimprinted thin films and imprinted nanogratings with different molecular weight poly(3-hexylthiophene-2,5-diyl) (P3HT) are compared. We first observe that the chain alignment is favored by medium molecular weight (Mn = 25 kDa) P3HT for nonimprinted thin films. However, NIL allows large molecular weight P3HT (>40 kDa) to organize more strongly, which has been desired for efficient charge transport but is difficult to achieve through any other technique. Consequently P3HT/[6,6]-penyl-C61-butyric-acid-methyl-ester (PCBM) solar cells with large molecular weight P3HT nanogratings show a high power conversion efficiency of 4.4%, which is among the best reported P3HT/PCBM photovoltaics devices.

  7. Molecular Weight Effects on the Viscoelastic Response of a Polyimide

    NASA Technical Reports Server (NTRS)

    Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.

    2000-01-01

    The effect of molecular weight on the viscoelastic performance of an advanced polymer (LaRC -SI) was investigated through the use of creep compliance tests. Testing consisted of short-term isothermal creep and recovery with the creep segments performed under constant load. The tests were conducted at three temperatures below the glass transition temperature of each material with different molecular weight. Through the use of time-aging-time superposition procedures, the material constants, material master curves and aging-related parameters were evaluated at each temperature for a given molecular weight. The time-temperature superposition technique helped to describe the effect of temperature on the timescale of the viscoelastic response of each molecular weight. It was shown that the low molecular weight materials have increased creep compliance and creep compliance rate, and are more sensitive to temperature than the high molecular weight materials. Furthermore, a critical molecular weight transition was observed to occur at a weight-average molecular weight of approximately 25000 g/mol below which, the temperature sensitivity of the time-temperature superposition shift factor increases rapidly.

  8. Inhibition of cell adhesion by high molecular weight kininogen

    PubMed Central

    1992-01-01

    An anti-cell adhesion globulin was purified from human plasma by heparin-affinity chromatography. The purified globulin inhibited spreading of osteosarcoma and melanoma cells on vitronectin, and of endothelial cells, platelets, and mononuclear blood cells on vitronectin or fibrinogen. It did not inhibit cell spreading on fibronectin. The protein had the strongest antiadhesive effect when preadsorbed onto the otherwise adhesive surfaces. Amino acid sequence analysis revealed that the globulin is cleaved (kinin-free) high molecular weight kininogen (HKa). Globulin fractions from normal plasma immunodepleted of high molecular weight kininogen (HK) or from an individual deficient of HK lacked adhesive activity. Uncleaved single- chain HK preadsorbed at neutral pH, HKa preadsorbed at pH greater than 8.0, and HKa degraded further to release its histidine-rich domain had little anti-adhesive activity. These results indicate that the cationic histidine-rich domain is critical for anti-adhesive activity and is somehow mobilized upon cleavage. Vitronectin was not displaced from the surface by HKa. Thus, cleavage of HK by kallikrein results in both release of bradykinin, a potent vasoactive and growth-promoting peptide, and formation of a potent anti-adhesive protein. PMID:1370494

  9. Crosslinked self-assemblies of lipoid acid-substituted low molecular weight (1800 Da) polyethylenimine as reductive-sensitive non-viral gene vectors

    NASA Astrophysics Data System (ADS)

    Chen, Xiaojiao; Yuan, Zhefan; Yi, Xiaoqing; Zhuo, Renxi; Li, Feng

    2012-10-01

    In this study, amphiphilic polyethylenimine-graft-thioctic acid (PEI-TA) and polyethylenimine-graft-lauric acid (PEI-LA) were synthesized. Both PEI-TA and PEI-LA could self-assemble into micelles. Due to the existence of disulfide-linked rings at the end of hydrophobic moieties, PEI-TA could form stable micelles with disulfide crosslinked cores (PEI-TA-SS). In comparison with the PEI-LA micelle, PEI-TA-SS possessed higher DNA binding ability according to the gel retardation assay and heparin replacement assay. In vitro transfection experiments indicated that PEI-TA-SS showed comparably high transfection efficiency as compared to 25 kDa PEI. More interestingly, the luciferase expression of PEI-TA-SS was superior to that of PEI-LA at low N/P ratio, which might be ascribed to the stronger binding capacity of PEI-TA-SS facilitating the entering of PEI-TA-SS/pDNA complexes into cells.

  10. Efficacy and tolerance of an injectable medical device containing stable hybrid cooperative complexes of high- and low-molecular-weight hyaluronic acid: a monocentric 16 weeks open-label evaluation

    PubMed Central

    Sparavigna, Adele; Tenconi, Beatrice

    2016-01-01

    Background An injectable medical device containing stable hybrid cooperative complexes of high- and low-molecular-weight hyaluronic acid (HA) has been developed with characteristics suited for a global improvement of facial esthetics. Objective To evaluate the HA product performance in improving some key facial esthetic features. The study employed clinical scales, subjective evaluations, and facial skin objective measurements. Methods A single Italian site treated 64 female subjects aged 38–60 years, with injections at five predetermined points, on each side of the face, with a 4-week time lapse between the first and the second product administration. Subjects were evaluated after 4, 8, 12, and 16 weeks, using validated clinical scales, subjective evaluation, and objective quantitative outcome measures. Assessment of esthetic results included photographic documentation. Results Both the clinical and subjective assessments, and the majority of objective instrumental parameters indicated an improvement throughout the study and were already significant at week 4 or 8 and were still significant at week 16 (3 months after the second treatment). Minor and temporary local skin reactions were observed in 23% of subjects at the site of the injections, and the global judgment on tolerability was good or excellent, both in the investigators’ opinion and volunteers’ self-evaluation. Conclusion Both subjective and objective improvement of the facial parameters was consistent with the bio-remodeling purpose, and persistent and still statistically significant at the end of the study. The tolerability and safety profile of the product were judged good or excellent both by investigators and volunteers. This study supports the claim for bio-remodeling of these stable hybrid cooperative complexes of low- and high-molecular-weight HA. PMID:27713647

  11. Size-exclusion chromatography of ultrahigh molecular weight methylcellulose ethers and hydroxypropyl methylcellulose ethers for reliable molecular weight distribution characterization.

    PubMed

    Li, Yongfu; Shen, Hongwei; Lyons, John W; Sammler, Robert L; Brackhagen, Meinolf; Meunier, David M

    2016-03-15

    Size-exclusion chromatography (SEC) coupled with multi-angle laser light scattering (MALLS) and differential refractive index (DRI) detectors was employed for determination of the molecular weight distributions (MWD) of methylcellulose ethers (MC) and hydroxypropyl methylcellulose ethers (HPMC) having weight-average molecular weights (Mw) ranging from 20 to more than 1,000kg/mol. In comparison to previous work involving right-angle light scattering (RALS) and a viscometer for MWD characterization of MC and HPMC, MALLS yields more reliable molecular weight for materials having weight-average molecular weights (Mw) exceeding about 300kg/mol. A non-ideal SEC separation was observed for cellulose ethers with Mw>800kg/mol, and was manifested by upward divergence of logM vs. elution volume (EV) at larger elution volume at typical SEC flow rate such as 1.0mL/min. As such, the number-average molecular weight (Mn) determined for the sample was erroneously large and polydispersity (Mw/Mn) was erroneously small. This non-ideality resulting in the late elution of high molecular weight chains could be due to the elongation of polymer chains when experimental conditions yield Deborah numbers (De) exceeding 0.5. Non-idealities were eliminated when sufficiently low flow rates were used. Thus, using carefully selected experimental conditions, SEC coupled with MALLS and DRI can provide reliable MWD characterization of MC and HPMC covering the entire ranges of compositions and molecular weights of commercial interest. PMID:26794765

  12. Size-exclusion chromatography of ultrahigh molecular weight methylcellulose ethers and hydroxypropyl methylcellulose ethers for reliable molecular weight distribution characterization.

    PubMed

    Li, Yongfu; Shen, Hongwei; Lyons, John W; Sammler, Robert L; Brackhagen, Meinolf; Meunier, David M

    2016-03-15

    Size-exclusion chromatography (SEC) coupled with multi-angle laser light scattering (MALLS) and differential refractive index (DRI) detectors was employed for determination of the molecular weight distributions (MWD) of methylcellulose ethers (MC) and hydroxypropyl methylcellulose ethers (HPMC) having weight-average molecular weights (Mw) ranging from 20 to more than 1,000kg/mol. In comparison to previous work involving right-angle light scattering (RALS) and a viscometer for MWD characterization of MC and HPMC, MALLS yields more reliable molecular weight for materials having weight-average molecular weights (Mw) exceeding about 300kg/mol. A non-ideal SEC separation was observed for cellulose ethers with Mw>800kg/mol, and was manifested by upward divergence of logM vs. elution volume (EV) at larger elution volume at typical SEC flow rate such as 1.0mL/min. As such, the number-average molecular weight (Mn) determined for the sample was erroneously large and polydispersity (Mw/Mn) was erroneously small. This non-ideality resulting in the late elution of high molecular weight chains could be due to the elongation of polymer chains when experimental conditions yield Deborah numbers (De) exceeding 0.5. Non-idealities were eliminated when sufficiently low flow rates were used. Thus, using carefully selected experimental conditions, SEC coupled with MALLS and DRI can provide reliable MWD characterization of MC and HPMC covering the entire ranges of compositions and molecular weights of commercial interest.

  13. High Molecular Weight Forms of Mammalian Respiratory Chain Complex II

    PubMed Central

    Nůsková, Hana; Holzerová, Eliška; Vrbacký, Marek; Pecina, Petr; Hejzlarová, Kateřina; Kľučková, Katarína; Rohlena, Jakub; Neuzil, Jiri; Houštěk, Josef

    2013-01-01

    Mitochondrial respiratory chain is organised into supramolecular structures that can be preserved in mild detergent solubilisates and resolved by native electrophoretic systems. Supercomplexes of respiratory complexes I, III and IV as well as multimeric forms of ATP synthase are well established. However, the involvement of complex II, linking respiratory chain with tricarboxylic acid cycle, in mitochondrial supercomplexes is questionable. Here we show that digitonin-solubilised complex II quantitatively forms high molecular weight structures (CIIhmw) that can be resolved by clear native electrophoresis. CIIhmw structures are enzymatically active and differ in electrophoretic mobility between tissues (500 – over 1000 kDa) and cultured cells (400–670 kDa). While their formation is unaffected by isolated defects in other respiratory chain complexes, they are destabilised in mtDNA-depleted, rho0 cells. Molecular interactions responsible for the assembly of CIIhmw are rather weak with the complexes being more stable in tissues than in cultured cells. While electrophoretic studies and immunoprecipitation experiments of CIIhmw do not indicate specific interactions with the respiratory chain complexes I, III or IV or enzymes of the tricarboxylic acid cycle, they point out to a specific interaction between CII and ATP synthase. PMID:23967256

  14. Impact of molecular weight in four-branched star vectors with narrow molecular weight distribution on gene delivery efficiency.

    PubMed

    Nemoto, Yasushi; Borovkov, Alexey; Zhou, Yue-Min; Takewa, Yoshiaki; Tatsumi, Eisuke; Nakayama, Yasuhide

    2009-12-01

    A series of star-shaped cationic polymers, termed star vectors (SVs), has been developed as effective nonviral gene delivery carriers. In this study, we separated SVs into several fractions having different molecular weights with very narrow molecular weight distributions in order to examine in detail the influence of the molecular weight of the SVs on the gene transfection efficiency. As a model compound for several types of SVs, 4-branched poly(N,N-dimethylaminopropyl acrylamide) having a molecular weight (M(n)) of approximately 35 kDa and polydispersity of 1.6 was prepared by iniferter-based radical polymerization. The SVs were separated using size-exclusion chromatography to obtain seven fractions having M(n) ranging from 27 kDa to 73 kDa with polydispersity ranging from 1.1 to 1.2. All the fractionated SVs have similar pH of 10.2-10.4 and were able to interact with and condense luciferase-encoding plasmid deoxyribonucleic acid (DNA) to yield SV/DNA polyplexes. A water-soluble tetrazolium-1 (WST) assay showed that all SVs had minimal cellular cytotoxicity under an N/P charge ratio of 10. The critical micellar concentration decreased with an increase in the M(n) of the fractionated SVs; however, the particle size of the polyplexes, exclusion activity of ethidium bromide, and zeta-potential of the polyplexes increased. An in vitro evaluation using COS-1 cells at an N/P ratio of 10 showed that transfection activity increased almost linearly with M(n). The highest transfection activity was obtained for SVs with the highest M(n) (73 kDa), which was over 7 times that for the SVs with the lowest M(n) (27 kDa), the nonfractionated original SV, or PEI standard. The transfection efficiency was more correlated with the amphiphilicity or hydrophobicity of the SVs and the surface potential and condensate density of the polyplexes than with the particle size.

  15. Locked nucleic acid molecular beacons.

    PubMed

    Wang, Lin; Yang, Chaoyong James; Medley, Colin D; Benner, Steven A; Tan, Weihong

    2005-11-16

    A novel LNA-MB (molecular beacon based on locked nucleic acid bases) has been designed and investigated. It exhibits very high melting temperature and is thermally stable, shows superior single base mismatch discrimination capability, and is stable against digestion by nuclease and has no binding with single-stranded DNA binding proteins. The LNA-MB will be widely useful in a variety of areas, especially for in vivo hybridization studies.

  16. Free volume variation with molecular weight of polymers

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Eftekhari, Abe; Hinkley, Jeffrey A.; St.clair, Terry L.; Jensen, Brian J.

    1992-01-01

    Free volume measurements were made in several molecular weight fractions of two different geometries of poly(arylene ether ketone)s. Free volumes were measured using positron lifetime spectroscopy. It has been observed that the free volume cell size V(sub f) varies with the molecular weight M of the test samples according to an equation of the form V(sub f) = AM(B), where A and B are constants. The molecular weights computed from the free volume cell sizes are in good agreement with the values measured by gel permeation chromatography.

  17. Low molecular weight species in humic and fulvic fractions

    USGS Publications Warehouse

    Wilson, M.A.; Collin, P.J.; Malcolm, R.L.; Perdue, E.M.; Cresswell, P.

    1988-01-01

    Fourier transform solution 1H nuclear magnetic resonance (NMR) spectrometry with homogated water peak irradiation is a useful method for detecting low molecular weight substances in humic extracts. Succinate, acetate, methanol, formate, lactate and some aryl methoxyl compounds have been detected in extracts from a wide range of sources. In view of the controversy over whether low molecular weight substances are contaminants in humic extracts introduced by the concentration procedure, we report that some of these materials are not contaminants since 1H-NMR can be used to follow their formation from higher molecular weight species. ?? 1988.

  18. Do Low Molecular Weight Agents Cause More Severe Asthma than High Molecular Weight Agents?

    PubMed Central

    Meca, Olga; Cruz, María-Jesús; Sánchez-Ortiz, Mónica; González-Barcala, Francisco-Javier; Ojanguren, Iñigo; Munoz, Xavier

    2016-01-01

    Introduction The aim of this study was to analyse whether patients with occupational asthma (OA) caused by low molecular weight (LMW) agents differed from patients with OA caused by high molecular weight (HMW) with regard to risk factors, asthma presentation and severity, and response to various diagnostic tests. Methods Seventy-eight patients with OA diagnosed by positive specific inhalation challenge (SIC) were included. Anthropometric characteristics, atopic status, occupation, latency periods, asthma severity according to the Global Initiative for Asthma (GINA) control classification, lung function tests and SIC results were analysed. Results OA was induced by an HMW agent in 23 patients (29%) and by an LMW agent in 55 (71%). A logistic regression analysis confirmed that patients with OA caused by LMW agents had a significantly higher risk of severity according to the GINA classification after adjusting for potential confounders (OR = 3.579, 95% CI 1.136–11.280; p = 0.029). During the SIC, most patients with OA caused by HMW agents presented an early reaction (82%), while in patients with OA caused by LMW agents the response was mainly late (73%) (p = 0.0001). Similarly, patients with OA caused by LMW agents experienced a greater degree of bronchial hyperresponsiveness, measured as the difference in the methacholine dose-response ratio (DRR) before and after SIC (1.77, range 0–16), compared with patients with OA caused by HMW agents (0.87, range 0–72), (p = 0.024). Conclusions OA caused by LMW agents may be more severe than that caused by HMW agents. The severity of the condition may be determined by the different mechanisms of action of these agents. PMID:27280473

  19. Ultra-low-molecular-weight heparins: precise structural features impacting specific anticoagulant activities.

    PubMed

    Lima, Marcelo A; Viskov, Christian; Herman, Frederic; Gray, Angel L; de Farias, Eduardo H C; Cavalheiro, Renan P; Sassaki, Guilherme L; Hoppensteadt, Debra; Fareed, Jawed; Nader, Helena B

    2013-03-01

    Ultra-low-molecular-weight heparins (ULMWHs) with better efficacy and safety ratios are under development; however, there are few structural data available. The main structural features and molecular weight of ULMWHs were studied and compared to enoxaparin. Their monosaccharide composition and average molecular weights were determined and preparations studied by nuclear magnetic resonance spectroscopy, scanning ultraviolet spectroscopy, circular dichroism and gel permeation chromatography. In general, ULMWHs presented higher 3-O-sulphated glucosamine and unsaturated uronic acid residues, the latter being comparable with their higher degree of depolymerisation. The analysis showed that ULMWHs are structurally related to LMWHs; however, their monosaccharide/oligosaccharide compositions and average molecular weights differed considerably explaining their different anticoagulant activities. The results relate structural features to activity, assisting the development of new and improved therapeutic agents, based on depolymerised heparin, for the prophylaxis and treatment of thrombotic disorders.

  20. Simple nanoparticle-based luminometric method for molecular weight determination of polymeric compounds.

    PubMed

    Pihlasalo, Sari; Virtamo, Maria; Legrand, Nicolas; Hänninen, Pekka; Härmä, Harri

    2014-01-21

    A nanoparticle-based method utilizing time-resolved luminescence resonance energy transfer (TR-LRET) was developed for molecular weight determination. This mix-and-measure nanoparticle method is based on the competitive adsorption between the analyte and the acceptor-labeled protein to donor Eu(III) nanoparticles. The size-dependent adsorption of molecules enables the molecular weight determination of differently sized polymeric compounds down to a concentration level of micrograms per liter. The molecular weight determination from 1 to 10 kDa for polyamino acids and from 0.3 to 70 kDa for polyethylene imines is demonstrated. The simple and cost-effective nanoparticle method as microtiter plate assay format shows great potential for the detection of the changes in molecular weight or for quantification of differently sized molecules in biochemical laboratories and in industrial polymeric processes.

  1. Molecular-Weight-Controlled, End-Capped Polybenzimidazoles

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Hergenrother, Paul M.; Smith, Joseph G., Jr.

    1993-01-01

    Novel molecular-weight-controlled end-capped poly(arylene ether benzimidazole)s (PAEBI's) prepared by nucleophilic displacement reaction of di(hydroxyl)benzimidazole monomers with activated aromatic dihalides. Polymers prepared at various molecular weights by upsetting stoichiometry of monomers and end-capped with monohydroxybenzimidazole. Exhibit favorable physical and mechanical properties, improved solubility in polar aprotic solvents and better compression moldability. Potential applications as adhesives, coatings, films, fibers, membranes, moldings, and composite matrix resins.

  2. Evaluation of a Viscosity-Molecular Weight Relationship.

    ERIC Educational Resources Information Center

    Mathias, Lon J.

    1983-01-01

    Background information, procedures, and results are provided for a series of graduate/undergraduate polymer experiments. These include synthesis of poly(methylmethacrylate), viscosity experiment (indicating large effect even small amounts of a polymer may have on solution properties), and measurement of weight-average molecular weight by light…

  3. Permeability of low molecular weight organics through nanofiltration membranes.

    PubMed

    Meylan, Sébastien; Hammes, Frederik; Traber, Jacqueline; Salhi, Elisabeth; von Gunten, Urs; Pronk, Wouter

    2007-09-01

    The removal of natural organic matter (NOM) using nanofiltration (NF) is increasingly becoming an option for drinking water treatment. Low molecular weight (LMW) organic compounds are nevertheless only partially retained by such membranes. Bacterial regrowth and biofilm formation in the drinking water distribution system is favoured by the presence of such compounds, which in this context are considered as the assimilable organic carbon (AOC). In this study, the question of whether NF produces microbiologically stable water was addressed. Two NF membranes (cut-off of about 300Da) were tested with different natural and synthetic water samples in a cross-flow filtration unit. NOM was characterised by liquid chromatography with organic carbon detection (LC-OCD) using a size-exclusion column in addition to specific organic acid measurements, while AOC was measured in a batch growth bioassay. Similarly to high molecular weight organic compounds like polysaccharides or humic substances that have a permeability lower than 1%, charged LMW organic compounds were efficiently retained by the NF membranes tested and showed a permeability lower than 3%. However, LMW neutrals and hydrophobic organic compounds permeate to a higher extent through the membranes and have a permeability of up to 6% and 12%, respectively. Furthermore, AOC was poorly retained by NF and the apparent AOC concentration measured in the permeated water was above the proposed limit for microbiologically stable water. This indicates that the drinking water produced by NF might be biologically unstable in the distribution system. Nevertheless, in comparison with the raw water, NF significantly reduced the AOC concentration.

  4. Purification of a Low Molecular Weight Fucoidan for SPECT Molecular Imaging of Myocardial Infarction

    PubMed Central

    Saboural, Pierre; Chaubet, Frédéric; Rouzet, Francois; Al-Shoukr, Faisal; Ben Azzouna, Rana; Bouchemal, Nadia; Picton, Luc; Louedec, Liliane; Maire, Murielle; Rolland, Lydia; Potier, Guy; Le Guludec, Dominique; Letourneur, Didier; Chauvierre, Cédric

    2014-01-01

    Fucoidans constitute a large family of sulfated polysaccharides with several biochemical properties. A commercial fucoidan from brown algae, containing low molecular weight polysaccharidic species constituted of l-fucose, uronic acids and sulfate groups, was simply treated here with calcium acetate solution. This treatment led to a purified fraction with a yield of 45%. The physicochemical characterizations of the purified fucoidan using colorimetric assay, MALLS, dRI, FT-IR, NMR, exhibited molecular weight distributions and chemical profiles similar for both fucoidans whereas the sulfate and l-fucose contents increased by 16% and 71%, respectively. The biodistribution study in rat of both compounds labeled with 99mTc evidenced a predominant renal elimination of the purified fucoidan, but the crude fucoidan was mainly retained in liver and spleen. In rat myocardial ischemia-reperfusion, we then demonstrated the better efficiency of the purified fucoidan. This purified sulfated polysaccharide appears promising for the development of molecular imaging in acute coronary syndrome. PMID:25251032

  5. Enzymatic degradation processes of poly[(R)-3-hydroxybutyric acid] and poly[(R)-3-hydroxybutyric acid-co-(R)-3-hydroxyvaleric acid] single crystals revealed by atomic force microscopy: effects of molecular weight and second-monomer composition on erosion rates.

    PubMed

    Numata, Keiji; Kikkawa, Yoshihiro; Tsuge, Takeharu; Iwata, Tadahisa; Doi, Yoshiharu; Abe, Hideki

    2005-01-01

    Enzymatic degradation processes of poly[(R)-3-hydroxybutyric acid] (P(3HB)) and poly[(R)-3-hydroxybutyric acid-co-(R)-3-hydroxyvaleric acid] (P(3HB-co-3HV)) single crystals in the presence of PHB depolymerase from Ralstonia pickettii T1 were studied by real-time and static atomic force microscopy (AFM) observations. Fibril-like crystals were generated along the long axis of single crystals during the enzymatic degradation, and then the dimensions of fibril-like crystals were analyzed quantitatively. The morphologies and sizes of fibril-like crystals were dependent on the molecular weight and copolymer composition of polymers. For all samples, the crystalline thickness gradually decreased toward a tip from the root of a fibril-like crystal after enzymatic degradation for 1 h. The thinning of fibril-like crystals may be attributed to the destruction of chain-packing structure toward crystallographic c axis by the adsorption of enzyme. From the real-time AFM images, it was found that at the initial stage of degradation the enzymatic erosion started from the disordered chain-packing region in single crystals to form the grooves along the a axis. The generated fibril-like crystals deformed at a constant rate along the a axis with a constant rate after the induction time. The erosion rate at the grooves along the a axis increased with a decrease of molecular weight and with an increase of copolymer composition. On the other hand, the erosion rate along the a axis, at the tip of the fibril-like crystal, was dependent on only the copolymer composition, and the value increased with an increase in the copolymer composition. The morphologies and sizes of fibril-like crystals were governed by both the erosion rates along the a axis at the grooves and tip of fibril-like crystals. In addition, we were able to estimated the overall enzymatic erosion rate of single crystals by PHB depolymerase from the volumetric analysis.

  6. Synthesis, characterization, and controlled release of selenium nanoparticles stabilized by chitosan of different molecular weights.

    PubMed

    Zhang, Chunyue; Zhai, Xiaona; Zhao, Guanghua; Ren, Fazheng; Leng, Xiaojing

    2015-12-10

    Chitosan-stabilized selenium nanoparticles (SeNPs) have been reported, but there is no information on the effect of the chitosan molecular weight on the structure, stability, and selenium release properties of the SeNPs. Herein, we compared the uniform Se(0) spherical nanoparticles prepared through the reduction of seleninic acid with ascorbic acid in the presence of chitosan with different molecular weights (Mws). We found that both low and high molecular weight chitosan-stabilized selenium nanoparticles exhibited core-shell microstructures with a size of about 103 nm after 30 days growing through the "bottom-up approach" and "top-down approach," respectively. Moreover, both chitosan SeNPs processed excellent stability towards pH and enzyme treatment. In contrast, selenium was easily released to different extents from these two chitosan SeNPs upon treatment with different free radicals. This makes these materials potentially useful as oral antioxidant supplements. PMID:26428112

  7. Low molecular-weight phenols in Tannat wines made by alternative winemaking procedures.

    PubMed

    Favre, Guzmán; Peña-Neira, Álvaro; Baldi, Cecilia; Hernández, Natalia; Traverso, Sofía; Gil, Graciela; González-Neves, Gustavo

    2014-09-01

    Low molecular weight phenols of Tannat red wines produced by Traditional Maceration (TM), Prefermentative Cold Maceration (PCM), Maceration Enzyme (ENZ) and grape-Seed Tannins additions (ST), were performed and discussed. Alternatives to TM increased wine phenolic contents but unequally, ST increased mainly smaller flavans-3-ol, PCM anthocyanins and ENZ proanthocyanidins (up to 2250 mg/L). However low molecular weight flavan-3-ols remained below 9 mg/L in all wines, showing that there is not necessarily a correspondence between wine richness in total tannins and flavan-3-ols contents at low molecular weight. PCM wines had particularly high concentrations of tyrosol and tryptophol, yeast metabolism derived compounds. The use of grape-seed enological tannins did not increase grape seed derived phenolic compounds such as gallic acid. Caftaric acid was found in concentrations much higher than those reported in other grape varieties. Wine phenolic content and composition was considerably affected by the winemaking procedures tested.

  8. Synthesis, characterization, and controlled release of selenium nanoparticles stabilized by chitosan of different molecular weights.

    PubMed

    Zhang, Chunyue; Zhai, Xiaona; Zhao, Guanghua; Ren, Fazheng; Leng, Xiaojing

    2015-12-10

    Chitosan-stabilized selenium nanoparticles (SeNPs) have been reported, but there is no information on the effect of the chitosan molecular weight on the structure, stability, and selenium release properties of the SeNPs. Herein, we compared the uniform Se(0) spherical nanoparticles prepared through the reduction of seleninic acid with ascorbic acid in the presence of chitosan with different molecular weights (Mws). We found that both low and high molecular weight chitosan-stabilized selenium nanoparticles exhibited core-shell microstructures with a size of about 103 nm after 30 days growing through the "bottom-up approach" and "top-down approach," respectively. Moreover, both chitosan SeNPs processed excellent stability towards pH and enzyme treatment. In contrast, selenium was easily released to different extents from these two chitosan SeNPs upon treatment with different free radicals. This makes these materials potentially useful as oral antioxidant supplements.

  9. Low molecular weight heparin in prevention of perioperative thrombosis.

    PubMed Central

    Leizorovicz, A.; Haugh, M. C.; Chapuis, F. R.; Samama, M. M.; Boissel, J. P.

    1992-01-01

    OBJECTIVE--To determine whether prophylactic treatment with low molecular weight heparin reduces the incidence of thrombosis in patients who have had general or orthopaedic surgery. DESIGN--Meta-analysis of results from 52 randomised, controlled clinical studies (29 in general surgery and 23 in orthopaedic surgery) in which low molecular weight heparin was compared with placebo, dextran, or unfractionated heparin. SUBJECTS--Patients who had had general or orthopaedic surgery. INTERVENTION--Once daily injection of a low molecular weight heparin compared with placebo, dextran, or unfractionated heparin. MAIN OUTCOME MEASURES--Incidence of deep venous thrombosis, pulmonary embolism, major haemorrhages, and death. RESULTS--The results confirm that low molecular weight heparins are more efficacious for the prophylactic treatment of deep venous thrombosis than placebo (common odds ratio 0.31, 95% confidence interval 0.22 to 0.43; p < 0.001) and dextran (0.44, 0.30 to 0.65; p < 0.001). The results suggest that low molecular weight heparins are also more efficacious than unfractionated heparin (0.85, 0.74 to 0.97; p = 0.02), with no significant difference in the incidence of major haemorrhages (1.06, 0.93 to 1.20; p = 0.62). CONCLUSIONS--Low molecular weight heparins seem to have a higher benefit to risk ratio than unfractionated heparin in preventing perioperative thrombosis. However, it remains to be shown in a suitably powered clinical trial whether low molecular weight heparin reduces the risk of fatal pulmonary embolism compared with heparin. PMID:1281030

  10. Sorption of carboxylic acid from carboxylic salt solutions at PHS close to or above the pK.sub.a of the acid, with regeneration with an aqueous solution of ammonia or low-molecular-weight alkylamine

    DOEpatents

    King, C. Judson; Tung, Lisa A.

    1992-01-01

    Carboxylic acids are sorbed from aqueous feedstocks at pHs close to or above the acids' pH.sub.a into a strongly basic organic liquid phase or onto a basic solid adsorbent or moderately basic ion exchange resin. the acids are freed from the sorbent phase by treating it with aqueous alkylamine or ammonia thus forming an alkylammonium or ammonium carobxylate which dewatered and decomposed to the desired carboxylic acid and the alkylamine or ammonia.

  11. Sorption of carboxylic acid from carboxylic salt solutions at pHs close to or above the pK[sub a] of the acid, with regeneration with an aqueous solution of ammonia or low-molecular-weight alkylamine

    DOEpatents

    King, C.J.; Tung, L.A.

    1992-07-21

    Carboxylic acids are sorbed from aqueous feedstocks at pHs close to or above the acids' pH[sub a] into a strongly basic organic liquid phase or onto a basic solid adsorbent or moderately basic ion exchange resin. The acids are freed from the sorbent phase by treating it with aqueous alkylamine or ammonia thus forming an alkylammonium or ammonium carboxylate which dewatered and decomposed to the desired carboxylic acid and the alkylamine or ammonia. 8 figs.

  12. Endogenous ethanol affects biopolyester molecular weight in recombinant Escherichia coli.

    PubMed

    Hiroe, Ayaka; Hyakutake, Manami; Thomson, Nicholas M; Sivaniah, Easan; Tsuge, Takeharu

    2013-11-15

    In biopolyester synthesis, polyhydroxyalkanoate (PHA) synthase (PhaC) catalyzes the polymerization of PHA in bacterial cells, followed by a chain transfer (CT) reaction in which the PHA polymer chain is transferred from PhaC to a CT agent. Accordingly, the frequency of CT reaction determines PHA molecular weight. Previous studies have shown that exogenous alcohols are effective CT agents. This study aimed to clarify the effect of endogenous ethanol as a CT agent for poly[(R)-3-hydroxybutyrate] [P(3HB)] synthesis in recombinant Escherichia coli, by comparing with that of exogenous ethanol. Ethanol supplementation to the culture medium reduced P(3HB) molecular weights by up to 56% due to ethanol-induced CT reaction. NMR analysis of P(3HB) polymers purified from the culture supplemented with (13)C-labeled ethanol showed the formation of a covalent bond between ethanol and P(3HB) chain at the carboxyl end. Cultivation without ethanol supplementation resulted in the reduction of P(3HB) molecular weight with increasing host-produced ethanol depending on culture aeration. On the other hand, production in recombinant BW25113(ΔadhE), an alcohol dehydrogenase deletion strain, resulted in a 77% increase in molecular weight. Analysis of five E. coli strains revealed that the estimated number of CT reactions was correlated with ethanol production. These results demonstrate that host-produced ethanol acts as an equally effective CT agent as exogenous ethanol, and the control of ethanol production is important to regulate the PHA molecular weight.

  13. Photochemical Preparation of a Novel Low Molecular Weight Heparin

    PubMed Central

    Higashi, Kyohei; Hosoyama, Saori; Ohno, Asami; Masuko, Sayaka; Yang, Bo; Sterner, Eric; Wang, Zhenyu; Linhardt, Robert J.; Toida, Toshihiko

    2011-01-01

    Commercial low molecular weight heparins (LMWHs) are prepared by several methods including peroxidative cleavage, nitrous acid cleavage, chemical ß-elimination, and enzymatic β-elimination. The disadvantages of these methods are that strong reaction conditions or harsh chemicals are used and these can result in decomposition or modification of saccharide units within the polysaccharide backbone. These side-reactions reduce product quality and yield. Here we show the partial photolysis of unfractionated heparin can be performed in distillated water using titanium dioxide (TiO2). TiO2 is a catalyst that can be easily removed by centrifugation or filtration after the photochemical reaction takes place, resulting in highly pure products. The anticoagulant activity of photodegraded LMWH (pLMWH) is comparable to the most common commercially available LMWHs (i.e., Enoxaparin and Dalteparin). 1H NMR spectra obtained show that pLMWH maintains the same core structure as unfractionated heparin. This photochemical reaction was investigated using liquid chromatography/mass spectrometry (LC/MS) and unlike other processes commonly used to prepare LMWHs, photochemically preparation affords polysaccharide chains of reduced length having both odd and even of saccharide residues. PMID:22205826

  14. RHEOLOGICAL PROPERTIES & MOLECULAR WEIGHT DISTRIBUTIONS OF FOUR PERFLUORINATED THERMOPLASTIC POLYMERS

    SciTech Connect

    Hoffman, D M; Shields, A L

    2009-02-24

    Dynamic viscosity measurements and molecular weight estimates have been made on four commercial, amorphous fluoropolymers with glass transitions (Tg) above 100 C: Teflon AF 1600, Hyflon AD 60, Cytop A and Cytop M. These polymers are of interest as binders for the insensitive high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) because of their high density and Tg above ambient, but within a suitable processing range of TATB. As part of this effort, the rheological properties and molecular weight distributions of these polymers were evaluated.

  15. Adhesion and friction of PDMS networks: molecular weight effects.

    PubMed

    Galliano, A; Bistac, S; Schultz, J

    2003-09-15

    The objective of this work is to find relations between adherence and friction behaviors of elastomer networks. The chosen approach is based on the parallel study of the initial molecular weight (i.e., the degree of cross-linking) dependence of both adherence and friction. The polymers used are cross-linked polydimethylsiloxane (PDMS) and the substrate is a smooth glass plate. The experimental procedure uses both friction (pin on disk tribometer) and adhesion (tack test) measurements, associated with surface analysis and mechanical and rheological characterizations. Tack results show that high molecular weight PDMS exhibits the greater adherence energy. This can be explained by the role of both chain length and free and pendant chains: more numerous and longer free chains favor the substrate wetting (at a molecular scale) and increases the energy dissipation during separation (extraction and reptation mechanisms). However, friction results indicate a higher friction resistance for low molecular weight PDMS. This result could be quite surprising. An explanation based on interfacial sliding properties of free and pendant chains can be proposed. Elsewhere, for the lower molecular weight polymer, elastic contact present during friction is able to act as a forced wetting, constraining the network and consequently leading to a greater energy dissipation.

  16. Reductions with lithium in low molecular weight amines and ethylenediamine

    PubMed

    Garst; Dolby; Esfandiari; Fedoruk; Chamberlain; Avey

    2000-10-20

    Reductions of several types of compounds with lithium and ethylenediamine using low molecular weight amines as solvent are described. In all cases 1 mol of ethylenediamine or N, N'-dimethylethylenediamine per gram-atom of lithium was used. In some cases it was beneficial to add an alcohol as a proton donor. These reaction conditions were applied to the debenzylation of N-benzylamide and lactams which are refractory to hydrogenolysis with hydrogen and a catalyst. N-Benzylpilolactam 2, synthesized from pilocarpine hydrochloride in refluxing benzylamine, was debenzylated in good yield using 10 gram-atoms of lithium per mole (10 Li/mol) of 2 in n-propylamine. The debenzylation of N-benzyl-N-methyldecanoic acid amide, 4 (6 Li/mol), in t-butylamine/N, N'-dimethylethylenediamine gave N-methyldecanoic acid amide 6 in 70% yield. Alternatively, reduction of 4 (7 Li/mol) in t-butanol/n-propylamine/ethylenediamine gave n-decanal 12 in 36% yield. Using the same conditions, thioanisole, 1-adamantane-p-toluenesulfonamide, and 1-adamantane methyl p-toluenesulfonate were reduced with 3, 7, and 7.2 Li/mol of compound to give thiophenol (74%), adamantamine (91%), and 1-adamantane methanol (75%), respectively. In this solvent system naphthalene and 3-methyl-2-cyclohexene-1-one were reduced to isotetralin (74%) and 3-methyl cyclohexanone (quantitative) with 5 and 2.2 Li/mol of starting compound, respectively. Oximes and O-methyloximes were reduced to their corresponding amines using 5 and 8 Li/mol of compound, respectively. Anisole was also reduced to 1-methoxy-1,4-cyclohexadiene with 2.5 Li/mol of anisole. Undecanenitrile was reduced to undecylamine with 8.6 Li/mol. Additionally, a base-catalyzed formation of imidazolines from a nitrile and ethylenediamine was also explored.

  17. Quantitation and determination of molecular weight distribution of residual water soluble extractable polyamines in DMP 504, a poly-alkylamine bile acid sequestrant, by aqueous high performance size exclusion chromatography.

    PubMed

    Juliano, K; Champion, W L; Schreiber, M A; Blackwell, J A

    1997-11-01

    A high performance size exclusion chromatography (HPSEC) method with refractive index detection for quantitation and molecular weight determination of extractable water soluble polyamines (SPA) in a novel proprietary polymeric pharmaceutical compound (DMP 504) is described. The extracted polyamines are synthetic impurities as well as potential degradation products of the polymer. Data for calibration, precision, solution stability, and limits of detection and quantitation are presented to validate the suitability of this method for its intended purpose. Response linearity for the poly(2-vinylpyridine) standard is demonstrated between 10 and 1000 micrograms ml-1, equivalent to 0.005% and 0.5% (w/w) in DMP 504. Molecular weight distributions of SPA extracted from DMP 504 are presented. No increase in SPA is detected in DMP 504 over 6 months storage at room temperature.

  18. Mean molecular weight and hydrogen abundance of Titan's atmosphere

    NASA Technical Reports Server (NTRS)

    Samuelson, R. E.; Hanel, R. A.; Kunde, V. G.; Maguire, W. C.

    1981-01-01

    The 200-600/cm continuum opacity in the troposphere and lower stratosphere of Titan is inferred from thermal emission spectra from the Voyager 1 IR spectrometer (IRIS). The surface temperature and mean molecular weight are between 94 and 97 K and between 28.3 and 29.2 AMU, respectively. The mole fraction of molecular hydrogen is 0.002 + or - 0.001, which is equivalent to an abundance of approximately 0.2 + or - 0.1 km amagat.

  19. Hydrolytic degradation of electron beam irradiated high molecular weight and non-irradiated moderate molecular weight PLLA.

    PubMed

    Loo, Say Chye Joachim; Tan, Hui Tong; Ooi, Chui Ping; Boey, Yin Chiang Freddy

    2006-05-01

    The purpose of this study is to examine the hydrolytic degradation of electron beam irradiated ring-opening polymerized (ROP) poly(l-lactide) (PLLA-ir) and non-irradiated melt polycondensation polymerized poly(l-lactic acid) (PLLA-pc). It was observed that irradiation increases the hydrolytic degradation rate constant for ROP PLLA. This was due to a more hydrophilic PLLA-ir, as a result of irradiation. The degradation rate constants (k) of PLLA-ir samples were also found to be similar, regardless of the radiation dose, and an empirically formulated equation relating hydrolytic degradation time span to radiation dose was derived. The k value for PLLA-pc was observed to be lower than that for PLLA-ir, though the latter had a higher molecular weight. This was due to the difference in degradation mechanism, in which PLLA-ir undergoes end group scission, through a back- biting mechanism, during hydrolysis and thus a faster hydrolysis rate. Electron beam irradiation, though accelerates the degradation of PLLA, has been shown to be useful in accurately controlling the hydrolytic time span of PLLA. This method of controlling the hydrolytic degradation time was by far an easier task than through melt polycondensation polymerization. This would allow PLLA to be used for drug delivery purposes or as a temporary implant that requires a moderate time span (3-6 months). PMID:16701888

  20. Development of Layered Multiscale Porous Thin Films by Tuning Deposition Time and Molecular Weight of Polyelectrolytes.

    PubMed

    Yu, Jing; Sanyal, Oishi; Izbicki, Andrew P; Lee, Ilsoon

    2015-09-01

    This work focuses on the design of porous polymeric films with nano- and micro-sized pores existing in distinct zones. The porous thin films are fabricated by the post-treatment of layer-by-layer assembled poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) multilayers. In order to improve the processing efficiency, the deposition time is shortened to ≈ 10 s. It is found that fine porous structures can be created even by significantly reducing the processing time. The effect of using polyelectrolytes with widely different molecular weights is also studied. The pore size is increased by using high molecular weight PAH, while high molecular weight PAA minimizes the pore size to nanometer scale. Having gained a precise control over the pore size, layered multiscale porous thin films are further built up with either a microsized porous zone on top of a nanosized porous zone or vice versa.

  1. Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants.

    PubMed

    Simal-Gándara, J; Sarria-Vidal, M; Rijk, R

    2000-09-01

    Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane. PMID:11091796

  2. Reactions of Atmospheric Particulate Stabilized Criegee Intermediates Lead to High-Molecular-Weight Aerosol Components.

    PubMed

    Wang, MingYi; Yao, Lei; Zheng, Jun; Wang, XinKe; Chen, JianMin; Yang, Xin; Worsnop, Douglas R; Donahue, Neil M; Wang, Lin

    2016-06-01

    Aging of organic aerosol particles is one of the most poorly understood topics in atmospheric aerosol research. Here, we used an aerosol flow tube together with an iodide-adduct high-resolution time-of-flight chemical-ionization mass spectrometer equipped with a Filter Inlet for Gases and AEROsols (FIGAERO-HRToF-CIMS) to investigate heterogeneous ozonolysis of oleic acid (OL), developing a comprehensive oxidation mechanism with observed products. In addition to the well-known first-generation C9 products including nonanal, nonanoic acid, azelaic acid, and 9-oxononanoic acid, the iodide-adduct chemical ionization permitted unambiguous determination of a large number of high-molecular-weight particulate products up to 670 Da with minimum amounts of fragmentation. These high-molecular-weight products are characterized by a fairly uniform carbon oxidation state but stepwise addition of a carbon backbone moiety, and hence continuous decrease in the volatility. Our results demonstrate that heterogeneous oxidation of organic aerosols has a significant effect on the physiochemical properties of organic aerosols and that reactions of particulate SCIs from ozonolysis of an unsaturated particulate species represent a previously underappreciated mechanism that lead to formation of high-molecular-weight particulate products that are stable under typical atmospheric conditions.

  3. Recent Developments in Low Molecular Weight Complement Inhibitors

    PubMed Central

    Qu, Hongchang; Ricklin, Daniel; Lambris, John D.

    2009-01-01

    As a key part of the innate immune system, complement plays an important role not only in defending invading pathogens but also in many other biological processes. Inappropriate or excessive activation of complement has been linked to many autoimmune, inflammatory, and neurodegenerative diseases, as well as ischemia-reperfusion injury and cancer. A wide array of low molecular weight complement inhibitors has been developed to target various components of the complement cascade. Their efficacy has been demonstrated in numerous in vitro and in vivo experiments. Though none of these inhibitors has reached the market so far, some of them have entered clinical trials and displayed promising results. This review provides a brief overview of the currently developed low molecular weight complement inhibitors, including short peptides and synthetic small molecules, with an emphasis on those targeting components C1 and C3, and the anaphylatoxin receptors. PMID:19800693

  4. Ultra-High-Molecular-Weight Silphenylene/Siloxane Elastomers

    NASA Technical Reports Server (NTRS)

    Hundley, N. H.; Patterson, W. J.

    1989-01-01

    Elastomers enhance thermal and mechancial properties. Capable of performing in extreme thermal/oxidative environments and having molecular weights above 10 to the sixth power prepared and analyzed in laboratory experiments. Made of methylvinylsilphenylene-siloxane terpolymers, new materials amenable to conventional silicone-processing technology. Similarly formulated commercial methyl-vinyl silicones, vulcanized elastomers exhibit enhance thermal/oxidative stability and equivalent or superior mechanical properties.

  5. Low-molecular-weight heparins: differential characterization/physical characterization.

    PubMed

    Guerrini, Marco; Bisio, Antonella

    2012-01-01

    Low-molecular-weight heparins (LMWHs), derived from unfractionated heparin (UFH) through different depolymerization processes, have advantages with respect to the parent heparin in terms of pharmacokinetics, convenience of administration, and reduced side effects. Each LMWH can be considered as an independent drug with its own activity profile, placing significance on their biophysical characterization, which will also enable a better understanding of their structure-function relationship. Several chemical and physical methods, some involving sample modification, are now available and are reviewed.

  6. Beyond Dispersity: Deterministic Control of Polymer Molecular Weight Distribution.

    PubMed

    Gentekos, Dillon T; Dupuis, Lauren N; Fors, Brett P

    2016-02-17

    The breadth of the molecular weight distributions (MWD) of polymers influences their physical properties; however, no synthetic methods allow precise control of the exact shape and composition of a distribution. We report a modular strategy that enables deterministic control over polymer MWD through temporal regulation of initiation in nitroxide-mediated polymerization reactions. This approach is applicable to any controlled polymerization that uses a discrete initiator, and it allows the use of MWD composition as a parameter to tune material properties.

  7. Production of chemicals from methanol. I. Low molecular weight olefins

    SciTech Connect

    Kaeding, W.W.; Butter, S.A.

    1980-01-01

    Methanol has been converted to water and hydrocarbons, with up to 70% selectivity to C/sub 2/-C/sub 4/ olefins, at 100% conversion, over ZSM-5 class zeolite catalysts modified with phosphorus compounds. Ethylene is proposed as the initial hydrocarbon produced. Evidence for the alkylation of olefins with methanol or methyl ether over these catalysts to produce higher molecular weight olefins is presented. 2 figures, 5 tables.

  8. High molecular weight polysaccharide that binds and inhibits virus

    DOEpatents

    Konowalchuk, Thomas W

    2014-01-14

    This invention provides a high molecular weight polysaccharide capable of binding to and inhibiting virus and related pharmaceutical formulations and methods on inhibiting viral infectivity and/or pathogenicity, as well as immunogenic compositions. The invention further methods of inhibiting the growth of cancer cells and of ameliorating a symptom of aging. Additionally, the invention provides methods of detecting and/or quantifying and/or isolating viruses.

  9. A novel mammalian high-molecular-weight aminopeptidase.

    PubMed

    Erbeznik, H; Hersh, L B

    1997-08-01

    Studies with the human lymphoma U937 cell line revealed the presence of two soluble aminopeptidase activities. Using specific antisera one of these was identified as the puromycin-specific aminopeptidase, while the other appeared to be a novel approximately 200-kDa activity. The kinetic properties of this high-molecular-weight aminopeptidase, referred to as Ap200, were similar to those of the puromycin-sensitive aminopeptidase, but showed quantitative differences. Ap200 is relatively insensitive to inhibition by both puromycin, K(i) = 27 microM, and bestatin, K(i) = 1.6 microM. Among the synthetic beta-naphthylamides, Ap200 is more specific for alanine-beta-naphthylamide compared to the puromycin-sensitive aminopeptidase. Similarly, this enzyme cleaves a more limited number of physiological peptides exhibiting a preference for the enkephalins. Ammonium sulfate, but not sodium chloride at the same ionic strength, was able to dissociate the high-molecular-weight aminopeptidase to a approximately 100-kDa active form. The high-molecular-weight aminopeptidase is found as a low abundant protein in a number of tissues including intestine, kidney, liver, lung, muscle, spleen, and testes, but could not be detected in adrenal, heart, or brain. Thus, it has a tissue distribution which differs from the puromycin-sensitive aminopeptidase.

  10. Evaluating nephrotoxicity of high-molecular-weight organic compounds in drinking water from lignite aquifers

    USGS Publications Warehouse

    Bunnell, J.E.; Tatu, C.A.; Lerch, H.E.; Orem, W.H.; Pavlovic, N.

    2007-01-01

    High-molecular-weight organic compounds such as humic acids and/or fulvic acids that are naturally mobilized from lignite beds into untreated drinking-water supplies were suggested as one possible cause of Balkan endemic nephropathy (BEN) and cancer of the renal pelvis. A lab investigation was undertaken in order to assess the nephrotoxic potential of such organic compounds using an in vitro tissue culture model. Because of the infeasibility of exposing kidney tissue to low concentrations of organics for years in the lab, tangential flow ultrafiltration was employed to hyperconcentrate samples suitable for discerning effects in the short time frames necessitated by tissue culture systems. Effects on HK-2 kidney cells were measured using two different cell proliferation assays (MTT and alamarBlue). Results demonstrated that exposure of kidney tissue to high-molecular-weight organics produced excess cell death or proliferation depending on concentration and duration of exposure. Copyright ?? Taylor & Francis Group, LLC.

  11. Binding of pyrene to aquatic and commercial humic substances: The role of molecular weight and aromaticity

    USGS Publications Warehouse

    Chin, Y.-P.; Aiken, G.R.; Danielsen, K.M.

    1997-01-01

    The binding of pyrene to a number of humic substances isolated from various aquatic sources and a commercial humic acid was measured using the solubility enhancement method. The humic materials used in this study were characterized by various spectroscopic and liquid chromatography methods. A strong correlation was observed between the pyrene binding coefficient, K(doc), and the molecular weights, molar absorptivities at 280 nm, and aromaticity of the aquatic humic substances. Binding of pyrene to the commercial humic acid, however, was significantly stronger and did not obey the relationships observed between K(doc) and the chemical properties of the aquatic humic substrates. These results suggest that the molecular weight and the aromatic content of the humic substrates exert influences on the binding of nonpolar and planar aromatic molecules and that the physicochemical properties of both humic materials and organic solutes are important in controlling the speciation of nonpolar organic contaminants in natural waters.

  12. Body Weight Reducing Effect of Oral Boric Acid Intake

    PubMed Central

    Aysan, Erhan; Sahin, Fikrettin; Telci, Dilek; Yalvac, Mehmet Emir; Emre, Sinem Hocaoglu; Karaca, Cetin; Muslumanoglu, Mahmut

    2011-01-01

    Background: Boric acid is widely used in biology, but its body weight reducing effect is not researched. Methods: Twenty mice were divided into two equal groups. Control group mice drank standard tap water, but study group mice drank 0.28mg/250ml boric acid added tap water over five days. Total body weight changes, major organ histopathology, blood biochemistry, urine and feces analyses were compared. Results: Study group mice lost body weight mean 28.1% but in control group no weight loss and also weight gained mean 0.09% (p<0.001). Total drinking water and urine outputs were not statistically different. Cholesterol, LDL, AST, ALT, LDH, amylase and urobilinogen levels were statistically significantly high in the study group. Other variables were not statistically different. No histopathologic differences were detected in evaluations of all resected major organs. Conclusion: Low dose oral boric acid intake cause serious body weight reduction. Blood and urine analyses support high glucose, lipid and middle protein catabolisms, but the mechanism is unclear. PMID:22135611

  13. Wet-spinnability and crosslinked fibre properties of two collagen polypeptides with varied molecular weight.

    PubMed

    Tronci, Giuseppe; Kanuparti, Ramya Sri; Arafat, M Tarik; Yin, Jie; Wood, David J; Russell, Stephen J

    2015-11-01

    The formation of naturally derived materials with wet stable fibrous architectures is paramount in order to mimic the features of tissues at the molecular and microscopic scale. Here, we investigated the formation of wet-spun fibres based on collagen-derived polypeptides with comparable chemical composition and varied molecular weight. Gelatin and hydrolysed fish collagen (HFC) were selected as widely available linear amino-acidic chains of high and low molecular weight, respectively, and functionalised in the wet-spun fibre state in order to preserve the material geometry in physiological conditions. Wet-spun fibre diameter and morphology were dramatically affected depending on the polypeptide molecular weight, wet-spinning solvent (i.e. 2,2,2-trifluoroethanol and dimethyl sulfoxide) and coagulating medium (i.e. acetone and ethanol), resulting in either bulky or porous internal geometry. Dry-state tensile moduli were significantly enhanced in gelatin and HFC samples following covalent crosslinking with activated 1,3-phenylenediacetic acid (Ph) (E: 726±43-844±85MPa), compared to samples crosslinked via intramolecular carbodiimide-mediated condensation reaction (E: 588±38MPa). Resulting fibres displayed a dry diameter in the range of 238±18-355±28μm and proved to be mechanically stable (E: 230kPa) following equilibration with PBS, whilst a nearly complete degradation was observed after 5-day incubation in physiological conditions.

  14. Potentiometric titration and equivalent weight of humic acid

    USGS Publications Warehouse

    Pommer, A.M.; Breger, I.A.

    1960-01-01

    The "acid nature" of humic acid has been controversial for many years. Some investigators claim that humic acid is a true weak acid, while others feel that its behaviour during potentiometric titration can be accounted for by colloidal adsorption of hydrogen ions. The acid character of humic acid has been reinvestigated using newly-derived relationships for the titration of weak acids with strong base. Re-interpreting the potentiometric titration data published by Thiele and Kettner in 1953, it was found that Merck humic acid behaves as a weak polyelectrolytic acid having an equivalent weight of 150, a pKa of 6.8 to 7.0, and a titration exponent of about 4.8. Interdretation of similar data pertaining to the titration of phenol-formaldehyde and pyrogallol-formaldehyde resins, considered to be analogs for humic acid by Thiele and Kettner, leads to the conclusion that it is not possible to differentiate between adsorption and acid-base reaction for these substances. ?? 1960.

  15. Influence of Molecular Weight on the Mechanical Performance of a Thermoplastic Glassy Polyimide

    NASA Technical Reports Server (NTRS)

    Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.

    1999-01-01

    Mechanical Testing of an advanced thermoplastic polyimide (LaRC-TM-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength were all determined as a function of molecular weight and test temperature. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. A critical molecular weight (Mc) was observed to occur at a weight-average molecular weight (Mw) of approx. 22000 g/mol below which, the notched tensile strength decreases rapidly. This critical molecular weight transition is temperature-independent. Furthermore, inelastic analysis showed that low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. The microstructural images supported these findings.

  16. Morphology Evolution of Molecular Weight Dependent P3HT: PCBM Solar Cells

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Chen, Dian; Briseno, Alejandro; Russell, Thomas

    2011-03-01

    Effective strategies to maximize the performance of bulk heterojunction (BHJ) photovoltaic devices have to be developed and understood to realize their full potential. In BHJ solar cells, the morphology of the active layer is a critical issue to improve device efficiency. In this work, we choose poly(3-hexyl-thiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) system to study the morphology evolution. Different molecular weight P3HTs were synthesized by using Grignard Metathesis (GRIM)~method. In device optimization, polymer with a molecular weight between 20k-30k shows the highest efficiency. It was observed that the as-spun P3HT: PCBM (1:1) blends do not have high order by GISAXS. Within a few seconds of thermal annealing at 150& circ; the crystallinity of P3HT increaased substantially and the polymer chains adopted an edge-on orientation. An-bicontinous morphology was also developed within this short thermal treatment. The in situ GISAXS experiment showed that P3HT of high molecular weight was more easily crystallized from a slowly evaporated chlorobenzene solution and their edge-on orientation is much more obvious than for the lower molecular weight P3HTs. DSC was used to study the thermal properties of P3HTs and P3HT: PCBM blend. The χ of P3HT-PCBM was also calculated by using melting point depression method.

  17. Impact resistance and fractography in ultra high molecular weight polyethylenes.

    PubMed

    Puértolas, J A; Pascual, F J; Martínez-Morlanes, M J

    2014-02-01

    Highly crosslinked ultra high molecular weight polyethylenes (UHMWPE) stabilized by a remelting process or by the addition of an antioxidant are highly wear resistant and chemically stable. However, these polyethylenes currently used in total joint replacements suffer a loss of mechanical properties, especially in terms of fracture toughness. In this study we analyze the impact behavior of different polyethylenes using an instrumented double notch Izod test. The materials studied are three resins: GUR1050, GUR1020 with 0.1wt% of vitamin E, and MG003 with 0.1wt% of vitamin E. These resins were gamma irradiated at 90kGy, and pre and post-irradiation remelting processes were applied to GUR1050 for two different time periods. Microstructural data were determined by means of differential scanning calorimetry and transmission electron microscopy. Fractography carried out on the impact fracture surfaces and images obtained by scanning electron microscopy after etching indicated the existence of a fringe structure formed by consecutive ductile-brittle and brittle-ductile transitions, which is related to the appearance of discontinuities in the load-deflection curves. A correlation has been made of the macroscopic impact strength results and the molecular chain and microstructural characteristics of these aforementioned materials, with a view to designing future resins with improved impact resistance. The use of UHMWPE resins with low molecular weight or the application of a remelting treatment could contribute to obtain a better impact strength behavior.

  18. Electropolymerized molecularly imprinted polypyrrole film for sensing of clofibric acid.

    PubMed

    Schweiger, Bianca; Kim, Jungtae; Kim, Young Jun; Ulbricht, Mathias

    2015-01-01

    Piezoelectric quartz crystals and analogous gold substrates were electrochemically coated with molecularly imprinted polypyrrole films for pulsed amperometric detection (PAD) of clofibric acid, a metabolite of clofibrate. Cyclic voltammetry data obtained during polymerization and deposited weight estimations revealed a decrease of the polymerization rate with increasing clofibric acid concentration. XPS measurements indicated that clofibric acid could be removed after imprinting with an aqueous ethanol solution, which was further optimized by using PAD. Zeta potential and contact angle measurements revealed differences between molecularly imprinted (MIP) and non-imprinted polymer (NIP) layers. Binding experiments with clofibric acid and other substances showed a pronounced selectivity of the MIP for clofibric acid vs. carbamazepine, but the response of MIP and NIP to 2,4-dichlorophenoxyacetic acid was higher than that for clofibric acid. A smooth surface, revealed by AFM measurements, with roughness of 6-8 nm for imprinted and non-imprinted layers, might be a reason for an excessively low density of specific binding sites for clofibric acid. Furthermore, the decreased polymerization rate in the presence of clofibric acid might not result in well-defined polymer structures, which could be the reason for the lower sensitivity. PMID:25730487

  19. Electropolymerized Molecularly Imprinted Polypyrrole Film for Sensing of Clofibric Acid

    PubMed Central

    Schweiger, Bianca; Kim, Jungtae; Kim, Young Jun; Ulbricht, Mathias

    2015-01-01

    Piezoelectric quartz crystals and analogous gold substrates were electrochemically coated with molecularly imprinted polypyrrole films for pulsed amperometric detection (PAD) of clofibric acid, a metabolite of clofibrate. Cyclic voltammetry data obtained during polymerization and deposited weight estimations revealed a decrease of the polymerization rate with increasing clofibric acid concentration. XPS measurements indicated that clofibric acid could be removed after imprinting with an aqueous ethanol solution, which was further optimized by using PAD. Zeta potential and contact angle measurements revealed differences between molecularly imprinted (MIP) and non-imprinted polymer (NIP) layers. Binding experiments with clofibric acid and other substances showed a pronounced selectivity of the MIP for clofibric acid vs. carbamazepine, but the response of MIP and NIP to 2,4-dichlorophenoxyacetic acid was higher than that for clofibric acid. A smooth surface, revealed by AFM measurements, with roughness of 6–8 nm for imprinted and non-imprinted layers, might be a reason for an excessively low density of specific binding sites for clofibric acid. Furthermore, the decreased polymerization rate in the presence of clofibric acid might not result in well-defined polymer structures, which could be the reason for the lower sensitivity. PMID:25730487

  20. [The effect of low molecular weight substances on the human skin. Molecular mechanisms and their consequences].

    PubMed

    Merk, H F; Baron, J M

    2004-12-01

    Interactions between low molecular weight compounds with cells of the skin result in reactions with different proteins which enable the uptake, metabolism and efflux of these compounds. It is unlikely, that small molecular weight compounds can achieve pharmacological concentrations within cells by diffusion alone. The pattern of influx proteins of keratinocytes is different from that of hepatocytes. If the balance between these systems is disturbed, the skin may become unable to function as a protective organ which can result in diseases including cancer or-more frequently-allergic contact dermatitis. Recent investigations of the sensitization to fragrances and p-phenylenediamine are discussed. An improved understanding of the metabolism of low molecular weight compounds can lead to new therapeutic strategies. One example is the introduction of photodynamic therapy with topical applied porphyrin precursors.

  1. Molecular weights of individual proteins correlate with molecular volumes measured by atomic force microscopy.

    PubMed

    Schneider, S W; Lärmer, J; Henderson, R M; Oberleithner, H

    1998-02-01

    Proteins are usually identified by their molecular weights, and atomic force microscopy (AFM) produces images of single molecules in three dimensions. We have used AFM to measure the molecular volumes of a number of proteins and to determine any correlation with their known molecular weights. We used native proteins (the TATA-binding protein Tbp, a fusion protein of glutathione-S-transferase and the renal potassium channel protein ROMK1, the immunoglobulins IgG and IgM, and the vasodilator-stimulated phosphoprotein VASP) and also denatured proteins (the red blood cell proteins actin, Band 3 and spectrin separated by SDS-gel electrophoresis and isolated from nitrocellulose). Proteins studied had molecular weights between 38 and 900 kDa and were imaged attached to a mica substrate. We found that molecular weight increased with an increasing molecular volume (correlation coefficient = 0.994). Thus, the molecular volumes measured with AFM compare well with the calculated volumes of the individual proteins. The degree of resolution achieved (lateral 5 nm, vertical 0.2 nm) depended upon the firm attachment of the proteins to the mica. This was aided by coating the mica with suitable detergent and by imaging using the AFM tapping mode which minimizes any lateral force applied to the protein. We conclude that single (native and denatured) proteins can be imaged by AFM in three dimensions and identified by their specific molecular volumes. This new approach permits detection of the number of monomers of a homomultimeric protein and study of single proteins under physiological conditions at the molecular level.

  2. Conformations of Low-Molecular-Weight Lignin Polymers in Water.

    PubMed

    Petridis, Loukas; Smith, Jeremy C

    2016-02-01

    Low-molecular-weight lignin binds to cellulose during the thermochemical pretreatment of biomass for biofuel production, which prevents the efficient hydrolysis of the cellulose to sugars. The binding properties of lignin are influenced strongly by the conformations it adopts. Here, we use molecular dynamics simulations in aqueous solution to investigate the dependence of the shape of lignin polymers on chain length and temperature. Lignin is found to adopt collapsed conformations in water at 300 and 500 K. However, at 300 K, a discontinuous transition is found in the shape of the polymer as a function of the chain length. Below a critical degree of polymerization, Nc =15, the polymer adopts less spherical conformations than above Nc. The transition disappears at high temperatures (500 K) at which only spherical shapes are adopted. An implication relevant to cellulosic biofuel production is that lignin will self-aggregate even at high pretreatment temperatures.

  3. Conformations of low-molecular-weight lignin polymers in water

    DOE PAGES

    Petridis, Loukas; Smith, Jeremy C.

    2016-01-13

    Low-molecular-weight lignin binds to cellulose during the thermochemical pretreatment of biomass for biofuel production, which prevents the efficient hydrolysis of the cellulose to sugars. The binding properties of lignin are influenced strongly by the conformations it adopts. Here, we use molecular dynamics simulations in aqueous solution to investigate the dependence of the shape of lignin polymers on chain length and temperature. Lignin is found to adopt collapsed conformations in water at 300 and 500 K. However, at 300 K, a discontinuous transition is found in the shape of the polymer as a function of the chain length. Below a criticalmore » degree of polymerization, Nc=15, the polymer adopts less spherical conformations than above Nc. The transition disappears at high temperatures (500 K) at which only spherical shapes are adopted. As a result, an implication relevant to cellulosic biofuel production is that lignin will self-aggregate even at high pretreatment temperatures.« less

  4. Synthesis of high molecular weight PEO using non-metal initiators

    DOEpatents

    Yang, Jin; Sivanandan, Kulandaivelu; Pistorino, Jonathan; Eitouni, Hany Basam

    2015-05-19

    A new synthetic method to prepare high molecular weight poly(ethylene oxide) with a very narrow molecular weight distribution (PDI<1.5) is described. The method involves a metal free initiator system, thus avoiding dangerous, flammable organometallic compounds.

  5. Influence of molecular weight on in vitro immunostimulatory properties of instant coffee.

    PubMed

    Passos, Cláudia P; Cepeda, Márcio R; Ferreira, Sónia S; Nunes, Fernando M; Evtuguin, Dmitry V; Madureira, Pedro; Vilanova, Manuel; Coimbra, Manuel A

    2014-10-15

    Instant coffee was prepared and fractionated into higher (>100kDa), medium (5-10, 10-30, 30-100kDa) and lower (1-5, <1kDa) molecular weight fractions. Sugars and linkage composition characteristics of arabinogalactans and galactomannans were recovered in all fractions. Also, amino acid analysis performed after hydrolysis showed similar compositions in all fractions. On the contrary, free chlorogenic acids and caffeine were only detected in the lowest molecular weight fraction (<1kDa). A direct relationship between the melanoidins browning index and the molecular weight was observed. The fractions obtained were incubated in vitro with murine spleen lymphocytes in order to evaluate their possible immunostimulatory abilities. The surface expression of CD69 (early activation marker) on different lymphocyte sub-populations showed that the fraction with 1-5kDa was able to induce activation of B-lymphocytes. This was the only fraction to induce B-lymphocyte activation, since all the other fractions failed, even when higher concentrations were used.

  6. Relationship between molecular weight, monosaccharide composition and immunobiologic activity of Astragalus polysaccharides.

    PubMed

    Jiang, Yiping; Qi, Xiaohui; Gao, Kai; Liu, Wenjun; Li, Na; Cheng, Ningbo; Ding, Gang; Huang, Wenzhe; Wang, Zhenzhong; Xiao, Wei

    2016-10-01

    Four Astragalus polysaccharides (APS1-APS4) were isolated from the water extract of Radix Astragali and purified through ethanol precipitation with 20 %, 40 %, 60 % and 80 % ethanol, respectively. The total sugar content was measured by sulfuric acid-phenol method. Their molecular weight was determined using high performance gel permeation chromatography (HPGPC) and their monosaccharide composition was analyzed by reversed-phase high performance liquid chromatography (HPLC) after pre-column derivatization. Then the immunobiologic activity of APS was evaluated by the experiment of spleen lymphocytes proliferation in vitro. The data suggested that precipitation by different concentration of ethanol will obtain different molecular weight APS, the higher concentration of ethanol the smaller molecular weight for APS. The molecular weights of four APS were 257.7 kDa, 40.1 kDa, 15.3 kDa and 3.2 kDa. Monosaccharide composition analysis indicated that APS1 consisted of glucose only, and APS2 all consisted of arabinose. APS3 consisted of rhamnose, glucose, galactose and arabinose and APS4 consisted of galactose and arabinose, in a molar ratio of 1:10.76:6.55:12 and 3.02:1. The result of immunobiologic activity assay showed that both APS2 and APS3 can effectively stimulate normal spleen lymphocyte proliferation in vitro. Apart from this, the effect of APS2 also showed dose dependent tendency from 6.25 μg/mL to 800 μg/mL. The result of this research indicated that Astragalus polysaccharides, which consist of arabinose and their molecular weight between 15.2 kDa to 40.1 kDa, neither too high nor too low, had significant immune activity.

  7. Ice Nucleation by High Molecular Weight Organic Compounds

    NASA Astrophysics Data System (ADS)

    Cantrell, W.

    2003-12-01

    Deep convection in the tropics is frequently associated with biomass burning. Recent work has suggested that the size of ice crystals in the anvils of tropical cumulonimbus clouds may be affected by biomass burning, though the mechanism for such an effect is uncertain (Sherwood, 2002). We will present results of an investigation of the role that high molecular weight organic compounds, known to be produced in biomass burning (Elias et al., 1999), may play in tropical cirrus anvils through heterogeneous nucleation of ice. In particular, we examine the mechanisms underlying heterogeneous nucleation of ice by films of long chain alcohols by studying the interaction of the alcohols and water/ice using temperature controlled, Attenuated Total Reflection - Fourier Transform Infrared spectroscopy. The mechanisms are interpreted in the context of recent criticisms of some aspects of classical nucleation theory (Seeley and Seidler, 2001; Oxtoby, 1998). References V. Elias, B. Simoneit, A. Pereira, J. Cabral, and J. Cardoso, Detection of high molecular weight organic tracers in vegetation smoke samples by high-temperature gas chromatography-mass spectrometry. Environ. Sci. Tecnol., 33, 2369-2376, 1999. D. Oxtoby, Nucleation of first-order phase transitions. Acc. Chem. Res., 31, 91-97, 1998. L. Seeley and G. Seidler, Preactivation in the nucleation of ice by Langmuir films of aliphatic alcohols. J. Chem. Phys., 114, 10464-10470, 2001. S. Sherwood, Aerosols and ice particle size in tropical cumulonimbus. J. Climate, 15, 1051-1063, 2002.

  8. Controlling silk fibroin microspheres via molecular weight distribution.

    PubMed

    Zeng, Dong-Mei; Pan, Jue-Jing; Wang, Qun; Liu, Xin-Fang; Wang, Hui; Zhang, Ke-Qin

    2015-05-01

    Silk fibroin (SF) microspheres were produced by salting out SF solution via the addition of potassium phosphate buffer solution (K2HPO4-KH2PO4). The morphology, size and polydispersity of SF microspheres were adjusted by changing the molecular weight (MW) distribution and concentration of SF, as well as the ionic strength and pH of the buffer solution. Changing the conditions under which the SF fiber dissolved in the Lithium Boride (LiBr) solution resulted in altering the MW distribution of SF solution. Under optimal salting-out conditions (ionic strength>0.7 M and pH>7) and using a smaller and narrower SF MW distribution, SF microspheres with smoother shapes and more uniform sizes were produced. Meanwhile, the size and polydispersity of the microspheres increased when the SF concentration was increased from 0.25 mg/mL to 20 mg/mL. The improved SF microspheres, obtained by altering the distribution of molecular weight, have potential in drug and gene delivery applications.

  9. Incorporation of small molecular weight active agents into polymeric components.

    PubMed

    Iconomopoulou, Sofia M; Kallitsis, Joannis K; Voyiatzis, George A

    2008-01-01

    The incorporation of small molecular weight active agents into polymeric matrixes bearing controlled release characteristics represents an interesting strategy with numerous useful applications. Antimicrobials, biocides, fungicides or drugs, encapsulated into erodible or non-erodible polymeric micro-spheres, micro-capsules and micro-shells or/and embedded into continuous polymeric matrixes, are controlled released either by particular degradation routes or/and by specific stimuli. Cross-linking, curing or micro-porosity generating agents acting during polymerization impart additional controlled encapsulation characteristics to the active substances. Release modulating agents, like retardants or carrier materials used as vehicles are often encapsulated into microspheres or dispersed within polymeric compositions for the controlled introduction of an active agent into a liquid-based medium. The aim of this review is to reveal relevant strategies reported in recent patents on the encapsulation or incorporation of low molecular weight active agents into the matrix of polymers bearing controlled release characteristics. The inventions described implicate the formation of both erodible and non erodible polymer microparticles that contain active ingredients. Modification of polymer matrix and inorganic porous carriers represent pertinent major strategies that have been also developed and patented.

  10. Low molecular weight Abeta induces collapse of endoplasmic reticulum.

    PubMed

    Lai, Cora Sau-Wan; Preisler, Julie; Baum, Larry; Lee, Daniel Hong-Seng; Ng, Ho-Keung; Hugon, Jacques; So, Kwok-Fai; Chang, Raymond Chuen-Chung

    2009-05-01

    The endoplasmic reticulum (ER) is a dynamic multifunction organelle that is responsible for Ca(2+) homeostasis, protein folding, post-translational modification, protein degradation, and transportation of nascent proteins. Disruption of ER architecture might affect the normal physiology of the cell. In yeast, expansion of the ER is observed under unfolded protein response (UPR) and subsequently induces autophagy initiated from the ER. Here, we found that soluble low molecular weight of Abeta disrupted the anchoring between ER and microtubules (MT) and induced collapse of ER. In addition, it decreased the stability of MT. Subsequently, low molecular weight Abeta triggered autophagy and enhanced lysosomal degradation, as shown by electron microscopy and live-cell imaging. Dysfunction of ER can be further proved in postmortem AD brain and transgenic mice bearing APP Swedish mutation by immunohistochemical analysis of calreticulin. Treatment with Taxol, a MT-stabilizing agent, could partially inhibit collapse of the ER and induction of autophagy. The results show that Abeta-induced disruption of MT can affect the architecture of the ER. Collapse/aggregation of the ER may play an important role in Abeta peptide-triggered neurodegenerative processes.

  11. LARC-TPI 1500 series controlled molecular weight polyimide

    NASA Technical Reports Server (NTRS)

    Progar, Donald; St. Clair, Terry; Burks, Harold; Gautreaux, Carol; Yamaguchi, Akihiro

    1990-01-01

    LARC-TPI, a linear high temperature thermoplastic polyimide, was developed several years ago at NASA Langley Research Center. This material has been commercialized by Mitsui Toatsu Chemicals, Inc., Tokyo, Japan, as a varnish and powder. More recently, a melt-extruded film of a controlled molecular weight of this same polymer has been supplied to NASA Langley Research Center for evaluation. This new form, called LARC-TPI 1500 series, has been prepared in three molecular weights - high, medium and low flow polymers. The subject of this investigation deals with the rheological properties of the high and medium flow powders and the adhesive properties of the medium flow melt-extruded film. Rheological studies indicate that the high and medium flow forms of the polymer fall in the flow range of injection moldable materials. Adhesive data generated on the medium flow extruded film shows this form to be well suited for structural adhesive bonding. The data are as good or better than that for LARC-TPI data of previous studies.

  12. Characterization and Immunological Evaluation of Low-Molecular- Weight Alginate Derivatives.

    PubMed

    Xu, Xu; Bi, Decheng; Wan, Min

    2016-01-01

    Alginate is a naturally occurring acidic linear polysaccharide obtained from marine brown seaweed. Low molecular weight structurally diverse derivatives and oligosaccharides derived from alginate have shown various tremendous biological and pharmacological activities. It has been demonstrated that immuno-inflammation is involved in many prevalent human diseases, such as cancer, severe infection and neurodegeneration. Given the activities of marine natural products in the regulation of immune responses, increasing efforts are being made toward the development of lowmolecular- weight natural compounds that aid in the prevention and treatment of immune- and inflammatory-related diseases. In this review, we describe the development of chemical modification and molecular depolymerization methods that modify the physicochemical and biological characteristics of alginate. Additionally, current progress in research on immuno-inflammatory, anti-neurodegenerative and anti-tumor activities of alginate derivatives is highlighted.

  13. 21 CFR 178.3750 - Polyethylene glycol (mean molecular weight 200-9,500).

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... polymer of ethylene oxide and water with a mean molecular weight of 200 to 9,500. (b) It contains no more than 0.2 percent total by weight of ethylene and diethylene glycols if its mean molecular weight is 350 or higher and no more than 0.5 percent total by weight of ethylene and diethylene glycols if its...

  14. Viscoelastic Behavior of Low Molecular Weight Sulfonated Polystyrene Ionomers

    NASA Astrophysics Data System (ADS)

    Zhao, Hongying

    Ionomers are those hydrophobic polymers having small amounts of bonded ionic groups. The introduction of the ionic groups into polymer chain produces large changes in the physical, mechanical and rheological properties of the parent polymer. Characterization of the effect of the ionic interactions on the rheology is complicated by the difficulty in separating effects due to molecular entanglements and the ionic interactions. In this study, low molecular weight (Mw=4000) sulfonated polystyrene (SPS) was used to study the dynamic and steady shear rheology of SPS ionomers. The polymer chain length used was far below the entanglement molecular weight of polystyrene and effects of molecular entanglements will be absent. Any polymer chain entanglements or lengthening behavior on the melt rheology should be due to the ionic interactions. Random SPS ionomers with two sulfonation levels were examined, 2.5 and 4.8 mol%, which corresponded, respectively, to one and two sulfonate groups per chain on average. The metal counterions was varied across the alkali metal series of the periodic table. Morphology of the ionomer was characterized by using small angle x-ray scattering (SAXS) analysis, and dynamic and steady shear measurements were performed to investigate rheological behavior of the ionomers. Glass transition temperatures of the ionomers increased with increasing ion concentration but were insensitive to cation used. The scattering peak in SAXS indicates the existence of the nanophase separated ionic clusters. The strong ionic nanophase persist up to very high temperatures and is not sensitive to the external stress. Time-temperature superposition (TTS) of G' worked reasonably well while TTS of G" failed for most ionomers. Ionic interactions increased the terminal relaxation time of the melts as much as seven orders of magnitude greater than the unentangled PS melt. The zero shear viscosity and first normal stress coefficients scaled with cq/a, where c was the

  15. Mercury Photolytic Transformation Affected by Low-Molecular-Weight Natural Organics in Water

    SciTech Connect

    He, Feng; Zheng, Wang; Gu, Baohua; Liang, Liyuan

    2012-01-01

    Mechanisms by which dissolved organic matter (DOM) mediates the photochemical reduction of Hg(II) in aquatic ecosystems are not fully understood, owing to the heterogeneous nature and complex structural properties of DOM. In this work, naturally occurring aromatic compounds including salicylic, 4-hydrobenzoic, anthranilic, 4-aminobenzoic, and phthalic acid were systematically studied as surrogates for DOM in order to gain an improved mechanistic understanding of these compounds in the photoreduction of Hg(II) in water. We show that the photoreduction rates of Hg(II) are influenced not only by the substituent functional groups such as OH, NH2 and COOH on the benzene ring, but also the positioning of these functional groups on the ring structure. The Hg(II) photoreduction rate decreases in the order anthranilic acid > salicylic acid > phthalic acid according to the presence of the NH2, OH, COOH functional groups on benzoic acid. The substitution position of the functional groups affects reduction rates in the order anthranilic acid > 4-aminobenzoic acid and salicylic acid > 4-hydroxybenzoic acid. Reduction rates correlate strongly with ultraviolet (UV) absorption of these compounds and their concentrations, suggesting that the formation of organic free radicals during photolysis of these compounds is responsible for Hg(II) photoreduction. These results provide insight into the role of low-molecular-weight organic compounds and possibly DOM in Hg photoredox transformation and may thus have important implications for understanding Hg geochemical cycling in the environment.

  16. Low molecular weight PEIs modified by hydrazone-based crosslinker and betaine as improved gene carriers.

    PubMed

    Fang, Gang; Zeng, Fang; Yu, Changmin; Wu, Shuizhu

    2014-10-01

    Low-molecular-weight polyethyleneimine (LMW PEI) exhibits poorer transfection efficiency but lower cytotoxicity compared to high-molecular-weight polyethyleneimine (such as PEI 25kDa). To enhance the gene transfection performance of LMW PEI, we herein demonstrate a new strategy for modifying LMW PEI. A crosslinker containing an acid-labile hydrazone bond (hydrazone-based crosslinker) was synthesized and used to crosslink PEI 1.8kDa and convert it into higher-molecular-weight polycations. And the crosslinked polycations were further modified by incorporating a betaine monomer [N,N-dimethyl(acrylamidopropyl)ammonium propane sulfonate, DMAAPS] onto their surfaces. The molar percentages of the incorporated betaine molecules to amino groups on the polycations were determined as 21.2%, 36.0% and 77.2%, respectively. Molecular weights of the modified polycations were measured using capillary viscometry at pH 7.4 and 5.0, respectively, and the degradation of the polymers in acidic solution was confirmed. The PEIs modified with hydrazone and betaine (PEI-Hdz-DMAAPS) exhibit much lower cytotoxicity than PEI 25K, and they also show no or little hemolytic effect with their hemolysis rates around 5%. PEI-Hdz-DMAAPS21.2%/DNA and PEI-Hdz-DMAAPS36.0%/DNA complexes exhibit high transfection efficiencies, which are comparable to or higher than that of PEI 25K/DNA complex in the absence or presence of 10% serum. With these improved gene delivery properties, the PEI-Hdz-DMAAPS samples have great potential for serving as efficient gene carriers. This strategy may provide some insights for constructing some other biocompatible materials.

  17. Development of solvent-free offset ink using vegetable oil esters and high molecular-weight resin.

    PubMed

    Park, Jung Min; Kim, Young Han; Kim, Sung Bin

    2013-01-01

    In the development of solvent-free offset ink, the roles of resin molecular weight and used solvent on the ink performance were evaluated by examining the relationship between the various properties of resin and solvent and print quality. To find the best performing resin, the soy-oil fatty acid methyl ester (FAME) was applied to the five modified-phenolic resins having different molecular weights. It is found from the experimental results that the ink made of higher molecular weight and better solubility resin gives better printability and print quality. It is because larger molecular weight resin with better solubility gives higher rate of ink transfer. From the ink application of different esters to high molecular weight resin, the best printing performance was yielded from the soy-oil fatty acid butyl ester (FABE). It is due to its high kinematic viscosity resulting in the smallest change of ink transfer weight upon multiple number of printing, which improves the stability of ink quality.

  18. Hypoglycemic effect of polysaccharides with different molecular weight of Pseudostellaria heterophylla

    PubMed Central

    2013-01-01

    Abstracts Background The aims of this study were to evaluate the antidiabetic activity and to detect molecular size of Pseudostellaria heterophylla polysaccharide (PHP). Pseudostellaria heterophylla is a medicine extensively used in traditional Chinese medicine formulas to treat diabetes and its complications. Methods Molecular weight of PHP was determined by gel permeation chromatography combined with phenol-sulphuric acid method and the monosaccharides composition was determined by HPLC with a precolumn derivatization. Four polysaccharides with different molecular weight were compared for hypoglycemic active on two animal models both high does alloxan induced type1 diabetic mellitus (T1DM) and high-fat/lower does streptozotocin induced type2 diabetic mellitus (T2DM). Blood sugar, glucose tolerance, and insulin tolerance were detected. Rat serum IL-1β, IL-2, IL-10, Leptin, TNF-α, Acrp30 and CRP were also analyzed by sandwich-ELISA approaches to preliminary probe the hypoglycemic mechanism of PHP. Results The hypoglycemic effects related to molecular size of polysaccharide were more effective against T2DM than T1DM. PHP comprise four monosaccharides of galacturonic acid, glucose, galactose and arabinos. T2DM rats daily receiving oral dose of polysaccharide(100 ~ 400 mg/kg) with 50 ~ 210 kDa molecular weight (PF40) could not only significantly lower blood sugar but also reduce total triglyceride level in serum. PF40 improves in insulin tolerance inhibited the expression of some biomarkers including inflammatory cytokine TNF-α and elevated anti-inflammatory cytokine IL-10, regulated adiponectin Acrp30 and leptin. Conclusions PF40 prevent the cascade of inflammatory events in the treatment of T2DM to block overweight progresses to obesity. PMID:24131482

  19. Tuning the superstructure of ultrahigh-molecular-weight polyethylene/low-molecular-weight polyethylene blend for artificial joint application.

    PubMed

    Xu, Ling; Chen, Chen; Zhong, Gan-Ji; Lei, Jun; Xu, Jia-Zhuang; Hsiao, Benjamin S; Li, Zhong-Ming

    2012-03-01

    An easy approach was reported to achieve high mechanical properties of ultrahigh-molecular-weight polyethylene (UHMWPE)-based polyethylene (PE) blend for artificial joint application without the sacrifice of the original excellent wear and fatigue behavior of UHMWPE. The PE blend with desirable fluidity was obtained by melt mixing UHMWPE and low molecular weight polyethylene (LMWPE), and then was processed by a modified injection molding technology-oscillatory shear injection molding (OSIM). Morphological observation of the OSIM PE blend showed LMWPE contained well-defined interlocking shish-kebab self-reinforced superstructure. Addition of a small amount of long chain polyethylene (2 wt %) to LMWPE greatly induced formation of rich shish-kebabs. The ultimate tensile strength considerably increased from 27.6 MPa for conventional compression molded UHMWPE up to 78.4 MPa for OSIM PE blend along the flow direction and up to 33.5 MPa in its transverse direction. The impact strength of OSIM PE blend was increased by 46% and 7% for OSIM PE blend in the direction parallel and vertical to the shear flow, respectively. Wear and fatigue resistance were comparable to conventional compression molded UHMWPE. The superb performance of the OSIM PE blend was originated from formation of rich interlocking shish-kebab superstructure while maintaining unique properties of UHMWPE. The present results suggested the OSIM PE blend has high potential for artificial joint application.

  20. Expression of low molecular weight proteins in patients with leukaemia.

    PubMed

    Sheikh, N; Abid, R; Qureshi, A W; Basheer, T

    2012-06-01

    The current study is conducted to observe the differences in the level of low molecular weight proteins in the sera of patients with leukaemia in comparison to healthy subjects (control group). The sera of patients with leukaemia showed 15 peaks in the densitometric curve in comparison to the seven peaks of the controls. The peaks in the experimental samples that coincide with those in the control were of 134.14, 113.15, 76.06, 63.25, 48.07, 22.85 and 16.47 kDa molecular weights, respectively. Most of the new peaks appeared between the proteins of molecular weight 36-29 kDa in the experimental groups. Mean density of the 134.14 kDa protein band showed an increase in the protein in experimental groups I and II only whereas 113.15 and 22.85 kDa protein were increased in all experimental groups of patients with leukaemia. The expression of 76.06 and 63.25 kDa protein fraction was downregulated in the patients with leukaemia. A decline in the level of the protein of 48.07 kDa was observed in patients with leukaemia except in group I. Unlike the other protein fractions, the level of the protein of 16.47 kDa was significantly (p < 0.05) increased with a maximum density in group II. Intergroup experimental) comparison revealed an increasing pattern of 95.44 and 89.21 kDa with maximum level in group III sera. However the protein fractions of 38.07 and 34.94 kDa varied in the serum with maximum density in Group IV Protein fractions of 32.92 and 31.24 kDa were expressed in all age groups of patients with leukaemia with a maximum density in group III whereas the percentage densities of 14.42 and 13.56 kDa protein were quite different. This preliminary study will provide a basis to study the role of different proteins in patients with leukaemia.

  1. Mechanical Properties of LaRC(tm) SI Polymer for a Range of Molecular Weights

    NASA Technical Reports Server (NTRS)

    Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.; Nicholson, Lee M.

    2000-01-01

    Mechanical testing of an advanced polyimide resin (LaRC(tm)-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. Elastic and inelastic properties were characterized as a function of molecular weight and test temperature. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. The combined analysis of calculated yield stress and notched tensile strength indicated that low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. The microphotographs of the failure surfaces also supported these findings.

  2. Molecular Weight and Charge Density Asymmetry in Polyelectrolyte Complexation

    NASA Astrophysics Data System (ADS)

    Audus, Debra; Fredrickson, Glenn; Duechs, Dominik

    2009-03-01

    We investigate the phase diagram of oppositely charged polymers in a good solvent using a field-theoretic model. Mean-field solutions fail to predict the experimentally observed macroscopic phase separation into a solvent-rich phase and a dense liquid aggregate of polymers - a ``complex coacervate.'' We therefore study the model within a one-loop approximation, which accounts for Gaussian fluctuations in electrostatic and chemical potentials. Our particular focus is the effect of molecular weight, ionic strength, and charge asymmetry on the phase envelope. A set of dimensionless parameters is identified that dictate the size and shape of the two-phase region. Our results should be helpful in guiding experimental studies of coacervation.

  3. Apparatus and method of determining molecular weight of large molecules

    DOEpatents

    Fuerstenau, S.; Benner, W.H.; Madden, N.M.; Searles, W.

    1998-06-23

    A mass spectrometer determines the mass of multiply charged high molecular weight molecules. This spectrometer utilizes an ion detector which is capable of simultaneously measuring the charge z and transit time of a single ion as it passes through the detector. From this transit time, the velocity of the single ion may then be derived, thus providing the mass-to-charge ratio m/z for a single ion which has been accelerated through a known potential. Given z and m/z, the mass m of the single ion can then be calculated. Electrospray ions with masses in excess of 1 MDa and charge numbers greater than 425 e{sup {minus}} are readily detected. The on-axis single ion detection configuration enables a duty cycle of nearly 100% and extends the practical application of electrospray mass spectrometry to the analysis of very large molecules with relatively inexpensive instrumentation. 14 figs.

  4. Apparatus and method of determining molecular weight of large molecules

    DOEpatents

    Fuerstenau, Stephen; Benner, W. Henry; Madden, Norman; Searles, William

    1998-01-01

    A mass spectrometer determines the mass of multiply charged high molecular weight molecules. This spectrometer utilizes an ion detector which is capable of simultaneously measuring the charge z and transit time of a single ion as it passes through the detector. From this transit time, the velocity of the single ion may then be derived, thus providing the mass-to-charge ratio m/z for a single ion which has been accelerated through a known potential. Given z and m/z, the mass m of the single ion can then be calculated. Electrospray ions with masses in excess of 1 MDa and charge numbers greater than 425 e.sup.- are readily detected. The on-axis single ion detection configuration enables a duty cycle of nearly 100% and extends the practical application of electrospray mass spectrometry to the analysis of very large molecules with relatively inexpensive instrumentation.

  5. Dairy Wastewater Treatment Using Low Molecular Weight Crab Shell Chitosan

    NASA Astrophysics Data System (ADS)

    Geetha Devi, M.; Dumaran, Joefel Jessica; Feroz, S.

    2012-08-01

    The investigation of possible use of low molecular weight crab shell chitosan (MW 20 kDa) in the treatment of dairy waste water was studied. Various experiments have been carried out using batch adsorption technique to study the effects of the process variables, which include contact time, stirring speed, pH and adsorbent dosage. Treated effluent characteristics at optimum condition showed that chitosan can be effectively used as adsorbent in the treatment of dairy wastewater. The optimum conditions for this study were at 150 mg/l of chitosan, pH 5 and 50 min of mixing time with 50 rpm of mixing speed. Chitosan showed the highest performance under these conditions with 79 % COD, 93 % turbidity and 73 % TSS reduction. The result showed that chitosan is an effective coagulant, which can reduce the level of COD, TSS and turbidity in dairy industry wastewater.

  6. The versatile low-molecular-weight thiols: Beyond cell protection.

    PubMed

    Wang, Min; Zhao, Qunfei; Liu, Wen

    2015-12-01

    Low-molecular-weight (LMW) thiols are extensively involved in the maintenance of cellular redox potentials and the protection of cells from a variety of reactive chemical and electrophilic species. However, we recently found that the metabolic coupling of two LMW thiols - mycothiol (MSH) and ergothioneine (EGT) - programs the biosynthesis of the anti-infective agent lincomycin A. Remarkably, such a constructive role of the thiols in the biosynthesis of natural products has so far received relatively little attention. We speculate that the unusual thiol EGT might function as a chiral thiolation carrier (for modification) and a novel activator (for glycosylation) of sugar. Additionally, we examine recent evidence for LMW thiols (MSH and others) as sulfur donors of sulfur-containing natural products. Clearly, the LMW thiols have more diverse activities beyond cell protection, and more attention should be paid to the correlation of their functions with thiol-dependent enzymes.

  7. Does low molecular weight heparin shorten term labor?

    PubMed

    Ekman-Ordeberg, Gunvor; Akerud, Anna; Dubicke, Aurelija; Malmström, Anders; Hellgren, Margareta

    2010-01-01

    Dalteparin, a low molecular weight heparin (LMWH), is given to pregnant women with thrombotic disorders. Clinical observations together with the documented changes of heparan sulfate proteoglycans in normal and protracted labor fostered the idea that LMWH shortens delivery time. Labor time was retrospectively determined among nulliparous pregnant women treated with dalteparin because of previous venous thromboembolism (VTE), thrombophilia or acute VTE during current pregnancy. Their labor time was compared to matched untreated controls. The proportion of instrumental deliveries and neonatal outcome was also compared. The dalteparin-treated group showed a significantly (30%) shorter labor time compared to matched controls. Total instrumental deliveries were the same in the two groups but operative intervention due to protracted labor was significantly less common in dalteparin-treated women. There was no difference in neonatal outcome. Dalteparin most likely shortens parturition time and may decrease the number of operative interventions due to protracted labor.

  8. Massive choroidal hemorrhage associated with low molecular weight heparin therapy.

    PubMed

    Neudorfer, M; Leibovitch, I; Goldstein, M; Loewenstein, A

    2002-04-01

    An 84-year-old woman with unstable angina pectoris was treated with subcutaneous enoxaparine (Clexane) for several days before presenting with severe pain and decreased vision in her left eye. The intraocular pressure was 70 mmHg, and fundus examination showed a pigmented choroidal lesion and associated choroidal and retinal detachment. Ultrasonography was consistent with choroidal hemorrhage, and she was diagnosed as having acute glaucoma secondary to massive subchoroidal hemorrhage. Medical control of the intraocular pressure resulted in a significant clinical improvement. Intraocular hemorrhage and angle-closure glaucoma are rare and previously unreported complications in patients treated with low molecular weight heparin. It is important to be aware of this ocular complication as these drugs are so often used. PMID:11943940

  9. Gels and foams from ultrahigh molecular weight polyethylene

    SciTech Connect

    Hair, L.M.; Letts, S.A.; Tillotson, T.

    1988-07-01

    Ultrahigh molecular weight polyethylene (UHMW PE) foams with densities from 0.04 to 0.2 g/cm{sup 3} have routinely been made in our laboratory. First, an entangled solution of UHMW PE is made. Then, the solution is geled by cooling to crystallize the PE. The gel is later dried to a foam by critical point drying. Viscometry and cloud point measurements were used to determine the gelatin point and the critical gelatin concentrations. Polarized light microscopy and differential scanning calorimetry were used to investigate the effects of cooling rate on the gel, while the effects of cooling rate on the foam were investigated via x-ray diffraction and scanning electron microscopy. We found that rapid cooling of 5 wt % UHMW PE/tetralin solutions to {minus}10{degree}c yielded small, uniform structure at the expense of crystallinity and strength; cooling over three days yielded spherulitic structure with strength. 5 refs., 3 figs.

  10. Gels and foams from ultrahigh-molecular-weight polyethylene

    SciTech Connect

    Hair, L.M.; Letts, S.A. )

    1990-01-01

    Crystallization-gelation of ultrahigh-molecular-weight polyethylene (UHMW PE) was used to make stiff gels that were supercritically dried to make low-density, small-cell-size foams. The effects of solvent and cooling conditions on gelation and morphology were investigated. X-ray diffractometry showed that the size of the crystalline lamellae in the finished foam decreased with increased cooling rate for foams made from UHMW PE in tetralin, but not in dodecane or decalin. This difference may be attributable to the greater expansion of the polyethylene chain in tetralin than in dodecane, as revealed by viscometry. However, the superstructure of the foam, which includes the pore sizes and homogeneity, was found to be affected by solvent as well as by cooling conditions.

  11. Ultra-high molecular weight silphenylene-siloxane polymers

    NASA Technical Reports Server (NTRS)

    Patterson, W. J.; Hundley, N. H.; Ludwick, L. M.

    1984-01-01

    Silphenylene-siloxane copolymers with molecular weights above one million were prepared using a two stage polymerization technique. The technique was successfully scaled up to produce 50 grams of this high polymer in a single run. The reactive monomer approach was also investigated using the following aminosilanes: bis(dimethylamino)dimethylsilane, N,N-bis(pyrrolidinyl)dimethylsilane and N,N-bis(gamma-butyrolactam)dimethylsilane). Thermal analyses were performed in both air and nitrogen. The experimental polymers decomposed at 540 to 562 C, as opposed to 408 to 426 C for commercial silicones. Differential scanning calorimetry showed a glass transition (Tg) at -50 to -55 C for the silphenylene-siloxane copolymer while the commercial silicones had Tg's at -96 to -112 C.

  12. Molecular weight degradation and rheological properties of schizophyllan under ultrasonic treatment.

    PubMed

    Zhong, Kui; Zhang, Qi; Tong, Litao; Liu, Liya; Zhou, Xianrong; Zhou, Sumei

    2015-03-01

    Molecular weight degradation effects of schizophyllan (SPG) under ultrasonic treatments were investigated in this study. The degradation product was treated by alcohol fractional precipitation technology, and the molecular weight and rheological properties of ultrasonic-treated SPG (USPG) fractions were evaluated. Average molecular weight of SPG decreased significantly after ultrasonic treatments, and degradation product had more narrow distribution of molecular weight. The molecular weight degradation kinetics of SPG is adequately described by a second-order reaction. USPG fractions with different molecular weight were obtained by fractional precipitation for final alcohol concentration fractions 0-40%, 40-60% and 60-80%, respectively. USPG fractions had near-Newtonian flow behaviors, and USPG₈₀% exhibited viscous responses over the entire accessible frequency range. Therefore, ultrasonic treatment is a viable modification technology for SPG and other polymer materials with high molecular weight.

  13. Do nucleic acids moonlight as molecular chaperones?

    PubMed

    Docter, Brianne E; Horowitz, Scott; Gray, Michael J; Jakob, Ursula; Bardwell, James C A

    2016-06-01

    Organisms use molecular chaperones to combat the unfolding and aggregation of proteins. While protein chaperones have been widely studied, here we demonstrate that DNA and RNA exhibit potent chaperone activity in vitro Nucleic acids suppress the aggregation of classic chaperone substrates up to 300-fold more effectively than the protein chaperone GroEL. Additionally, RNA cooperates with the DnaK chaperone system to refold purified luciferase. Our findings reveal a possible new role for nucleic acids within the cell: that nucleic acids directly participate in maintaining proteostasis by preventing protein aggregation.

  14. Do nucleic acids moonlight as molecular chaperones?

    PubMed Central

    Docter, Brianne E.; Horowitz, Scott; Gray, Michael J.; Jakob, Ursula; Bardwell, James C.A.

    2016-01-01

    Organisms use molecular chaperones to combat the unfolding and aggregation of proteins. While protein chaperones have been widely studied, here we demonstrate that DNA and RNA exhibit potent chaperone activity in vitro. Nucleic acids suppress the aggregation of classic chaperone substrates up to 300-fold more effectively than the protein chaperone GroEL. Additionally, RNA cooperates with the DnaK chaperone system to refold purified luciferase. Our findings reveal a possible new role for nucleic acids within the cell: that nucleic acids directly participate in maintaining proteostasis by preventing protein aggregation. PMID:27105849

  15. Wear characteristics of ultrahigh molecular weight polyethylene (UHMWPE)

    NASA Astrophysics Data System (ADS)

    El-Domiaty, A.; El-Fadaly, M.; Nassef, A. Es.

    2002-10-01

    The wear of ultrahigh molecular weight polyethylene (UHMWPE) bearing against 316 stainless steel or cobalt chromium (Co-Cr) alloy was measured using a 12-channel wear tester especially developed for the evaluation of candidate materials for prosthetic joints. The coefficient of friction and wear rate were determined as a function of lubricant, contact stress, and metallic surface roughness in tests lasting 2 3 million cycles, the equivalent of several years use of a prosthesis. Wear was determined by the weight loss of the polyethylene (PE) specimens corrected for the effect of fluid absorption. The friction and wear processes in blood serum differed markedly from those in saline solution or distilled water. Only serum lubrication produced wear surfaces resembling those observed on removed prostheses. The experimental methods provided accurate reproducible measurement of PE wear. The long-term wear rates were proportional to load and sliding distance. Although the PE wear rate increased with increasing surface roughness, wear was not severe except with very coarse metal surfaces. The data obtained in these studies formed a comparison basis for the subsequent evaluation of potentially superior materials for prosthetic joints.

  16. Self-assembly of high molecular weight polypeptide copolymers studied via diffusion limited aggregation.

    PubMed

    Meier, Christoph; Wu, Yuzhou; Pramanik, Goutam; Weil, Tanja

    2014-01-13

    The assembly of high molecular weight polypeptides into complex architectures exhibiting structural complexity ranging from the nano- to the mesoscale is of fundamental importance for various protein-related diseases but also hold great promise for various nano- and biotechnological applications. Here, the aggregation of partially unfolded high molecular weight polypeptides into multiscale fractal structures is investigated by means of diffusion limited aggregation and atomic force microscopy. The zeta potential, the hydrodynamic radius, and the obtained fractal morphologies were correlated with the conformation of the polypeptide backbones as obtained from circular dichroism measurements. The polypeptides are modified with polyethylene oxide side chains to stabilize the polypeptides and to normalize intermolecular interactions. The modification with the hydrophobic thioctic acid alters the folding of the polypeptide backbone, resulting in a change in solution aggregation and fractal morphology. We found that a more compact folding results in dense and highly branched structures, whereas a less compact folded polypeptide chain yields a more directional assembly. Our results provide first evidence for the role of compactness of polypeptide folding on aggregation. Furthermore, the mesoscale-structured biofilms were used to achieve a hierarchical protein assembly, which is demonstrated by deposition of Rhodamine-labeled HSA with the preassembled fractal structures. These results contribute important insights to the fundamental understanding of the aggregation of high molecular weight polypeptides in general and provide opportunities to study nanostructure-related effects on biological systems such as adhesion, proliferation, and the development of, for example, neuronal cells. PMID:24354281

  17. Isolation and characterization of low molecular weight glycosaminoglycans from marine mollusc Amussium pleuronectus (linne) using chromatography.

    PubMed

    Saravanan, R; Shanmugam, A

    2010-03-01

    The glycosaminoglycan (GAG) heparin is a polyanionic sulfated polysaccharide most recognized for its anticoagulant activity. In the present study, the GAGs were extracted from bivalve mollusc Amussium pleuronectus. The crude GAGs were fractionated by ion-exchange (DEAE-cellulose and Amberlite IRA-900 & 120) chromatography. The recovered active fractions (as determined by metachromatic assay) were confirmed by agarose gel electrophoresis and the active fractions were purified in Sephadex G-100 column. Fractionated and purified GAG molecular weight was determined through gradient polyacrylamide gel electrophoresis. The structural characterization of low molecular weight GAG was analyzed by Fourier transform infrared spectroscopy. The activated partial thromboplastin time of purified GAG is 95 IU/mg and has molecular weight 6,500-7,500 Da. The disaccharide compositional analysis on the GAG sample was sulfated like porcine intestinal mucosal heparan sulfate, and it contains equivalent amount of uronic acid and hexosamine. The results of this study suggest that the GAG from A. pleuronectus could be an alternative source of heparin.

  18. Self-assembly of high molecular weight polypeptide copolymers studied via diffusion limited aggregation.

    PubMed

    Meier, Christoph; Wu, Yuzhou; Pramanik, Goutam; Weil, Tanja

    2014-01-13

    The assembly of high molecular weight polypeptides into complex architectures exhibiting structural complexity ranging from the nano- to the mesoscale is of fundamental importance for various protein-related diseases but also hold great promise for various nano- and biotechnological applications. Here, the aggregation of partially unfolded high molecular weight polypeptides into multiscale fractal structures is investigated by means of diffusion limited aggregation and atomic force microscopy. The zeta potential, the hydrodynamic radius, and the obtained fractal morphologies were correlated with the conformation of the polypeptide backbones as obtained from circular dichroism measurements. The polypeptides are modified with polyethylene oxide side chains to stabilize the polypeptides and to normalize intermolecular interactions. The modification with the hydrophobic thioctic acid alters the folding of the polypeptide backbone, resulting in a change in solution aggregation and fractal morphology. We found that a more compact folding results in dense and highly branched structures, whereas a less compact folded polypeptide chain yields a more directional assembly. Our results provide first evidence for the role of compactness of polypeptide folding on aggregation. Furthermore, the mesoscale-structured biofilms were used to achieve a hierarchical protein assembly, which is demonstrated by deposition of Rhodamine-labeled HSA with the preassembled fractal structures. These results contribute important insights to the fundamental understanding of the aggregation of high molecular weight polypeptides in general and provide opportunities to study nanostructure-related effects on biological systems such as adhesion, proliferation, and the development of, for example, neuronal cells.

  19. Low-molecular-weight hydroxyacids in marine atmospheric aerosol: evidence of a marine microbial origin

    NASA Astrophysics Data System (ADS)

    Miyazaki, Y.; Sawano, M.; Kawamura, K.

    2014-04-01

    Lactic acid (LA) and glycolic acid (GA), which are low-molecular-weight hydroxyacids, were identified in the particle and gas phases within the marine atmospheric boundary layer over the western subarctic North Pacific. Major portion of LA (81%) and GA (57%) were present in the particulate phase, which is consistent with the presence of a hydroxyl group in these molecules leading to the low volatility of the compounds. The average concentration of LA in more biologically influenced marine aerosols (average 33 ± 58 ng m-3) was substantially higher than that in less biologically influenced aerosols (average 11 ± 12 ng m-3). Over the oceacnic region of phytoplankton blooms, the concentration of aerosol LA was comparable to that of oxalic acid, which was the most abundant diacid during the study period. A positive correlation was found between the LA concentrations in more biologically influenced aerosols and chlorophyll a in seawater (r2 = 0.56), suggesting an important production of aerosol LA possibly associated with microbial (e.g., lactobacillus) activity in seawater and/or aerosols. Our finding provides a new insight into the poorly quantified microbial sources of marine organic aerosols (OA) because such low-molecular-weight hydroxyacids are key intermediates for OA formation.

  20. Low-molecular-weight hydroxyacids in marine atmospheric aerosol: evidence of a marine microbial origin

    NASA Astrophysics Data System (ADS)

    Miyazaki, Y.; Sawano, M.; Kawamura, K.

    2014-08-01

    Lactic acid (LA) and glycolic acid (GA), which are low-molecular-weight hydroxyacids, were identified in the particle and gas phases within the marine atmospheric boundary layer over the western subarctic North Pacific. A major portion of LA (81%) and GA (57%) was present in the particulate phase, which is consistent with the presence of a hydroxyl group in these molecules leading to the low volatility of the compounds. The average concentration (±SD) of LA in more biologically influenced marine aerosols (33 ± 58 ng m-3) was substantially higher than that in less biologically influenced aerosols (11 ± 12 ng m-3). Over the oceanic region of phytoplankton blooms, the concentration of aerosol LA was comparable to that of oxalic acid, which was the most abundant diacid during the study period. A positive correlation was found between the LA concentrations in more biologically influenced aerosols and chlorophyll a in seawater (r2 = 0.56), suggesting an important production of aerosol LA possibly associated with microbial (e.g., lactobacillus) activity in seawater and/or aerosols. Our finding provides a new insight into the poorly quantified microbial sources of marine organic aerosols (OAs) because such low-molecular-weight hydroxyacids are key intermediates for OA formation.

  1. In situ reinforced polymers using low molecular weight compounds

    NASA Astrophysics Data System (ADS)

    Yordem, Onur Sinan

    2011-12-01

    The primary objective of this research is to generate reinforcing domains in situ during the processing of polymers by using phase separation techniques. Low molecular weight compounds were mixed with polymers where the process viscosity is reduced at process temperatures and mechanical properties are improved once the material system is cooled or reacted. Thermally induced phase separation and thermotropic phase transformation of low molar mass compounds were used in isotactic polypropylene (iPP) and poly(ether ether ketone) (PEEK) resins. Reaction induced phase separation was utilized in thermosets to generate anisotropic reinforcements. A new strategy to increase fracture toughness of materials was introduced. Simultaneously, enhancement in stiffness and reduction in process viscosity were also attained. Materials with improved rheological and mechanical properties were prepared by using thermotropic phase transformations of metal soaps in polymers (calcium stearate/iPP). Morphology and thermal properties were studied using WAXS, DSC and SEM. Mechanical and rheological investigation showed significant reduction in process viscosity and substantial improvement in fracture toughness were attained. Effects of molecular architecture of metal soaps were investigated in PEEK (calcium stearate/PEEK and sodium stearate/PEEK). The selected compounds reduced the process viscosity due to the high temperature co-continuous morphology of metal soaps. Unlike the iPP system that incorporates spherical particles, interaction between PEEK and metal soaps resulted in two discrete and co-continuous phases of PEEK and the metal stearates. DMA and melt rheology exhibited that sodium stearate/PEEK composites are stiffer. Effective moduli of secondary metal stearate phase were calculated using different composite theories, which suggested bicontinuous morphology to the metal soaps in PEEK. Use of low molecular weight crystallizable solvents was investigated in reactive systems

  2. Molecular weight enlargement--a molecular approach to continuous homogeneous catalysis.

    PubMed

    Janssen, Michèle; Müller, Christian; Vogt, Dieter

    2010-09-28

    Molecular weight enlargement (MWE) is an attractive method for homogeneous catalyst recycling. Applications of MWE in combination with either catalyst precipitation or nanofiltration have demonstrated their great potential as a method for process intensification in homogeneous catalysis. Selected, recent advances in MWE in combination with catalyst recovery are discussed, together with their implication for future developments. These examples demonstrate that this strategy is applicable in many different homogeneously catalyzed transformations.

  3. Optimization of parameters for coverage of low molecular weight proteins.

    PubMed

    Müller, Stephan A; Kohajda, Tibor; Findeiss, Sven; Stadler, Peter F; Washietl, Stefan; Kellis, Manolis; von Bergen, Martin; Kalkhof, Stefan

    2010-12-01

    Proteins with molecular weights of <25 kDa are involved in major biological processes such as ribosome formation, stress adaption (e.g., temperature reduction) and cell cycle control. Despite their importance, the coverage of smaller proteins in standard proteome studies is rather sparse. Here we investigated biochemical and mass spectrometric parameters that influence coverage and validity of identification. The underrepresentation of low molecular weight (LMW) proteins may be attributed to the low numbers of proteolytic peptides formed by tryptic digestion as well as their tendency to be lost in protein separation and concentration/desalting procedures. In a systematic investigation of the LMW proteome of Escherichia coli, a total of 455 LMW proteins (27% of the 1672 listed in the SwissProt protein database) were identified, corresponding to a coverage of 62% of the known cytosolic LMW proteins. Of these proteins, 93 had not yet been functionally classified, and five had not previously been confirmed at the protein level. In this study, the influences of protein extraction (either urea or TFA), proteolytic digestion (solely, and the combined usage of trypsin and AspN as endoproteases) and protein separation (gel- or non-gel-based) were investigated. Compared to the standard procedure based solely on the use of urea lysis buffer, in-gel separation and tryptic digestion, the complementary use of TFA for extraction or endoprotease AspN for proteolysis permits the identification of an extra 72 (32%) and 51 proteins (23%), respectively. Regarding mass spectrometry analysis with an LTQ Orbitrap mass spectrometer, collision-induced fragmentation (CID and HCD) and electron transfer dissociation using the linear ion trap (IT) or the Orbitrap as the analyzer were compared. IT-CID was found to yield the best identification rate, whereas IT-ETD provided almost comparable results in terms of LMW proteome coverage. The high overlap between the proteins identified with IT

  4. Kinetics of Formation of Molecular Weight Distribution of Epoxy Composite

    NASA Astrophysics Data System (ADS)

    Komar, Lyudmila A.; Kondyurin, Alexey; Svistkov, Alexander L.

    Curing of epoxy matrix prepreg in free space environment is a complex problem. A simulation of the chemical reaction, evaporation and radiation effects in the matrix is a way to understand and predict the curing process. We have developed a mathematical apparatus of the epoxy resin kinetics in term of molecular weight distribution (MWD), which includes the polymerization mechanism of bifunctional epoxy and sixfunctional triethylenetetraamine (TETA) molecules. The mathematical model for a number of molecules with the mass m at time t is based on the following equation $ beta(t,m)=m_{am} / m sum(6}_{i=0) alpha(am) _i (t,m)+ m_{ep} / m sum(2}_{i=0) alpha(ep) _i (t,m), where m_{am} and m_{ep} are the masses of one amine block and one epoxy block, respectively; alpha^{am}_i (t,m) is the MWD near the TETA blocks with the chemical bonds i at time t for the mass values m>0; alpha_i^{ep}(t,m) is the MWD parameters of the epoxy blocks with chemical bonds i at time t for the mass values m>0. For the distribution densities alpha^{am}_i (t,m) and alpha_i^{ep}(t,m), we propose the differential system of equations, which has been solved by applying boundary conditions which are based on the results of chromatography and infrared spectroscopy measurements of the epoxy matrix having different concentration of the hardener. For the initial MWD we accept a Gaussian distribution with parameters alpha^{am}_0 (t,m_1) =146 amu, alpha_0^{ep}(t,m_1) =340 amu and alpha_1^{ep}(t,m_1) =624 amu. Dispersion of the molecular weight for the initial distribution equals to 25 amu. A portion of TETA molecules in the fraction was 25%, and the portion of epoxy molecules with i=0 and i=1 was 67.5% and 7.5%$, respectively. Solutions were obtained at mass step equals to 5 amu and at time step equals to 0.25 min over the interval from 0 to 500 min. The model gives a full kinetic of MWD during the curing reaction. The study is supported by the RFBR (grants N 12-08-00970-a and N 14-08-96011-r-ural-a).

  5. Biomolecular computation with molecular beacons for quantitative analysis of target nucleic acids.

    PubMed

    Lim, Hee-Woong; Lee, Seung Hwan; Yang, Kyung-Ae; Yoo, Suk-In; Park, Tai Hyun; Zhang, Byoung-Tak

    2013-01-01

    Molecular beacons are efficient and useful tools for quantitative detection of specific target nucleic acids. Thanks to their simple protocol, molecular beacons have great potential as substrates for biomolecular computing. Here we present a molecular beacon-based biomolecular computing method for quantitative detection and analysis of target nucleic acids. Whereas the conventional quantitative assays using fluorescent dyes have been designed for single target detection or multiplexed detection, the proposed method enables us not only to detect multiple targets but also to compute their quantitative information by weighted-sum of the targets. The detection and computation are performed on a molecular level simultaneously, and the outputs are detected as fluorescence signals. Experimental results show the feasibility and effectiveness of our weighted detection and linear combination method using molecular beacons. Our method can serve as a primitive operation of molecular pattern analysis, and we demonstrate successful binary classifications of molecular patterns made of synthetic oligonucleotide DNA molecules.

  6. Low Molecular Weight Norbornadiene Derivatives for Molecular Solar-Thermal Energy Storage.

    PubMed

    Quant, Maria; Lennartson, Anders; Dreos, Ambra; Kuisma, Mikael; Erhart, Paul; Börjesson, Karl; Moth-Poulsen, Kasper

    2016-09-01

    Molecular solar-thermal energy storage systems are based on molecular switches that reversibly convert solar energy into chemical energy. Herein, we report the synthesis, characterization, and computational evaluation of a series of low molecular weight (193-260 g mol(-1) ) norbornadiene-quadricyclane systems. The molecules feature cyano acceptor and ethynyl-substituted aromatic donor groups, leading to a good match with solar irradiation, quantitative photo-thermal conversion between the norbornadiene and quadricyclane, as well as high energy storage densities (396-629 kJ kg(-1) ). The spectroscopic properties and energy storage capability have been further evaluated through density functional theory calculations, which indicate that the ethynyl moiety plays a critical role in obtaining the high oscillator strengths seen for these molecules. PMID:27492997

  7. Low Molecular Weight Norbornadiene Derivatives for Molecular Solar-Thermal Energy Storage.

    PubMed

    Quant, Maria; Lennartson, Anders; Dreos, Ambra; Kuisma, Mikael; Erhart, Paul; Börjesson, Karl; Moth-Poulsen, Kasper

    2016-09-01

    Molecular solar-thermal energy storage systems are based on molecular switches that reversibly convert solar energy into chemical energy. Herein, we report the synthesis, characterization, and computational evaluation of a series of low molecular weight (193-260 g mol(-1) ) norbornadiene-quadricyclane systems. The molecules feature cyano acceptor and ethynyl-substituted aromatic donor groups, leading to a good match with solar irradiation, quantitative photo-thermal conversion between the norbornadiene and quadricyclane, as well as high energy storage densities (396-629 kJ kg(-1) ). The spectroscopic properties and energy storage capability have been further evaluated through density functional theory calculations, which indicate that the ethynyl moiety plays a critical role in obtaining the high oscillator strengths seen for these molecules.

  8. Application of 1H DOSY for Facile Measurement of Polymer Molecular Weights

    PubMed Central

    Li, Weibin; Chung, Hoyong; Daeffler, Christopher; Johnson, Jeremiah A.; Grubbs, Robert H.

    2012-01-01

    To address the practical issues of polymer molecular weight determination, the first accurate polymer weight-average molecular weight determination method in diverse living/controlled polymerization via DOSY (diffusion-ordered NMR spectroscopy) is reported. Based on the linear correlation between the logarithm of diffusion coefficient (log D) and the molecular weights (log Mw), external calibration curves were created to give predictions of molecular weights of narrowly-dispersed polymers. This method was successfully applied to atom transfer radical polymerization (ATRP), reversible addition–fragmentation chain transfer (RAFT), and ring-opening metathesis polymerization (ROMP), with weight-average molecular weights given by this method closely correlated to those obtained from GPC measurement. PMID:23335819

  9. Composition and molecular weight distribution of carob germ protein fractions.

    PubMed

    Smith, Brennan M; Bean, Scott R; Schober, Tilman J; Tilley, Michael; Herald, Thomas J; Aramouni, Fadi

    2010-07-14

    Biochemical properties of carob germ proteins were analyzed using a combination of selective extraction, reversed-phase high-performance liquid chromatography (RP-HPLC), size exclusion chromatography (SEC) coupled with multiangle laser light scattering (SEC-MALS), and electrophoretic analysis. Using a modified Osborne extraction procedure, carob germ flour proteins were found to contain approximately 32% albumin and globulin and approximately 68% glutelin with no prolamins detected. The albumin and globulin fraction was found to contain low amounts of disulfide-bonded polymers with relatively low M(w) ranging up to 5 x 10(6) Da. The glutelin fraction, however, was found to contain large amounts of high molecular weight disulfide-bonded polymers with M(w) up to 8 x 10(7) Da. When extracted under nonreducing conditions and divided into soluble and insoluble proteins as typically done for wheat gluten, carob germ proteins were found to be almost entirely ( approximately 95%) in the soluble fraction with only ( approximately 5%) in the insoluble fraction. As in wheat, SEC-MALS analysis showed that the insoluble proteins had a greater M(w) than the soluble proteins and ranged up to 8 x 10(7) Da. The lower M(w) distribution of the polymeric proteins of carob germ flour may account for differences in functionality between wheat and carob germ flour.

  10. A low molecular weight proteinase inhibitor produced by T lymphocytes.

    PubMed Central

    Ganea, D; Teodorescu, M; Dray, S

    1986-01-01

    A low molecular weight (MW) proteinase inhibitor, between 6500 and 21,500 MW, appeared in the supernatant of rabbit spleen cells cultured at high density for 24 hr. The inhibitor inhibited the enzymatic activity of trypsin for both a high MW natural substrate, fibrinogen, and for a low MW artificial substrate, Chromozym TRY. The low MW proteinase inhibitor is protein in nature and is different, in terms of specificity for enzymes, MW and sensitivity to different physical or chemical treatments, from aprotinin, a low MW proteinase inhibitor (6500 MW) of bovine origin, and from the soybean trypsin inhibitor, a relatively high MW proteinase inhibitor (21,500 MW). The inhibitor was found in the supernatant of purified T cells but not B cells, and its production was increased in the presence of an optimal concentration of Con A. The possibility that this proteinase inhibitor has a role in the regulation of trypsin-like proteinases involved to the immune response remains to be investigated. Images Figure 4 PMID:2417942

  11. Mean Molecular Weight Gradients in Proto-Jupiter

    NASA Astrophysics Data System (ADS)

    Helled, R.; Bodenheimer, P.; Rosenberg, E. D.; Podolak, M.; Lozovsky, M.

    2015-12-01

    The distribution of heavy elements in Jupiter cannot be directly measured, and must be inferred from structure models. Typically, structure models assume that Jupiter is fully convective with the heavy elements being uniformly distributed. However, in the case of layered-convection there is a gradient in the distribution of heavy elements which affects the temperature profile of the planet, and as a result also its derived composition. We simulate the formation of Jupiter and investigate whether mean molecular weight gradients that can lead to layered-convection are created. We show that planetesimal accretion naturally leads to compositional gradients in the region above the core. It is shown that after about 10^5 years the core of Jupiter is hot and is surrounded by layers that consist mostly heavy-elements but also some hydrogen and helium. As a result, Jupiter's core mass is expected to be 2-5 M_Earth with no sharp transition between the core and the envelope. These findings are important for the interpretation of Juno data and for linking giant planet internal structure with origins.

  12. High molecular weight kininogen binds to unstimulated platelets.

    PubMed Central

    Gustafson, E J; Schutsky, D; Knight, L C; Schmaier, A H

    1986-01-01

    Studies were performed to determine if the unstimulated platelet membrane has a site for high molecular weight kininogen (HMWK) binding. 125I-HMWK bound to unstimulated platelets. Zn++ was required for 125I-HMWK binding to unstimulated platelets and binding was maximal at 50 microM Zn++. Neither Mg++ nor Ca++ substituted for Zn++ in supporting 125I-HMWK binding to unstimulated platelets, and neither ion potentiated binding in the presence of 50 microM zinc. 125I-HMWK competed with equal affinity with HMWK for binding, and excess HMWK inhibited 125I-HMWK-platelet binding. Only HMWK, not prekallikrein, Factor XII, Factor XI, Factor V, fibrinogen, or fibronectin inhibited 125I-HMWK-platelet binding. 125I-HMWK binding to unstimulated platelets was 89% reversible within 10 min with a 50-fold molar excess of HMWK. Unstimulated platelets contained a single set of saturable, high affinity binding sites for 125I-HMWK with an apparent dissociation constant of 0.99 nM +/- 0.35 and 3,313 molecules/platelet +/- 843. These studies indicate that the unstimulated external platelet membrane has a binding site for HMWK that could serve as a surface to modulate contact phase activation. Images PMID:3722381

  13. Photoelectrical characterization of a new low molecular weight compound

    NASA Astrophysics Data System (ADS)

    Siderov, V.; Dobrikov, G. H.; Zhivkov, I.; Dobrikov, G. M.; Georgiev, Y.; Yordanov, R.; Honova, J.; Weiter, M.

    2014-12-01

    Photoelectrical characterization of a newly synthesized low molecular weight compound was carried out. 1,8-naphtalimide (chemical formula C32H34N4O5S) was originally synthesized and analyzed by NMR spectroscopy. Thin films were deposited in vacuum on commercially pre-patterned ITO covered glass substrates and the samples were prepared in clean room environment. The films deposited were characterized by SEM. Photoelectrical characteristics of the samples prepared were estimated by dark current-voltage measurement, spectral dependence of the photoconductivity and measurement under exposure with light, produced by solar simulator. Finally electroluminescence measurements were performed. It was found that the samples exhibit diode behaviour. The low values characterizing photovoltaic parameters obtained could be connected with the relative higher series resistance (Rseries). The predominant influence of Rseries is assumed as the relative high photoluminescence, measured from solution should be related to a relatively strong charge carrier photogeneration. This result is supported by electroluminescent measurement. Another reason for the low values of the photovoltaic parameters measured could be the non-optimized film thickness leading to a non-optimal light absorption and increased charge carrier recombination. The assumption for the predominant influence of Rseries is supported by the electroluminescent measurements.

  14. Method for determination of polyethylene glycol molecular weight.

    PubMed

    Pihlasalo, Sari; Hänninen, Pekka; Härmä, Harri

    2015-04-01

    A method utilizing competitive adsorption between polyethylene glycols (PEGs) and labeled protein to nanoparticles was developed for the determination of PEG molecular weight (MW) in a microtiter plate format. Two mix-and-measure systems, time-resolved luminescence resonance energy transfer (TR-LRET) with donor europium(III) polystyrene nanoparticles and acceptor-labeled protein and quenching with quencher gold nanoparticles and fluorescently labeled protein were compared for their performance. MW is estimated from the PEG MW dependent changes in the competitive adsorption properties, which are presented as the luminescence signal vs PEG mass concentration. The curves obtained with the TR-LRET system overlapped for PEGs larger than 400 g/mol providing no information on MW. Distinctly different curves were obtained with the quenching system enabling the assessment of PEG MW within a broad dynamic range. The data was processed with and without prior knowledge of the PEG concentration to measure PEGs over a MW range from 62 to 35,000 g/mol. The demonstration of the measurement independent of the PEG concentration suggests that the estimation of MW is possible with quenching nanoparticle system for neutrally charged and relatively hydrophilic polymeric molecules widening the applicability of the simple and cost-effective nanoparticle-based methods.

  15. Reactions of allylic radicals that impact molecular weight growth kinetics.

    PubMed

    Wang, Kun; Villano, Stephanie M; Dean, Anthony M

    2015-03-01

    The reactions of allylic radicals have the potential to play a critical role in molecular weight growth (MWG) kinetics during hydrocarbon oxidation and/or pyrolysis. Due to their stability (when compared to alkyl radicals), they can accumulate to relatively high concentrations. Thus, even though the rate coefficients for their various reactions are small, the rates of these reactions may be significant. In this work, we use electronic structure calculations to examine the recombination, addition, and abstraction reactions of allylic radicals. For the recombination reaction of allyl radicals, we assign a high pressure rate rule that is based on experimental data. Once formed, the recombination product can potentially undergo an H-atom abstraction reaction followed by unimolecular cyclization and β-scission reactions. Depending upon the conditions (e.g., higher pressures) these pathways can lead to the formation of stable MWG species. The addition of allylic radicals to olefins can also lead to MWG species formation. Once again, cyclization of the adduct followed by β-scission is an important energy accessible route. Since the recombination and addition reactions produce chemically-activated adducts, we have explored the pressure- and temperature-dependence of the overall rate constants as well as that for the multiple product channels. We describe a strategy for estimating these pressure-dependencies for systems where detailed electronic structure information is not available. We also derive generic rate rules for hydrogen abstraction reactions from olefins and diolefins by methyl and allyl radicals.

  16. Fatigue crack propagation behavior of ultrahigh molecular weight polyethylene.

    PubMed

    Connelly, G M; Rimnac, C M; Wright, T M; Hertzberg, R W; Manson, J A

    1984-01-01

    The relative fatigue crack propagation resistance of plain and carbon fiber-reinforced ultrahigh molecular weight polyethylene (UHMWPE) was determined from cyclic loading tests performed on compact tension specimens machined from the tibial components of total knee prostheses. Both materials were characterized by dynamic mechanical spectroscopy, X-ray diffraction, and differential scanning calorimetry. The cyclic tests used loading in laboratory air at 5 Hz using a sinusoidal wave form. Dynamic mechanical spectroscopy showed that the reinforced UHMWPE had a higher elastic storage modulus than the plain UHMWPE, whereas X-ray diffraction and differential scanning calorimetry showed that the percent crystallinity and degree of order in the crystalline regions were similar for the two materials. Fatigue crack propagation in both materials proved to be very sensitive to small changes in the applied cyclic stress intensity range. A 10% increase in stress intensity resulted in approximately an order of magnitude increase in fatigue crack growth rate. The fatigue crack propagation resistance of the reinforced UHMWPE was found to be significantly worse than that of the plain UHMWPE. This result was attributed to poor bonding between the carbon fibers and the UHMWPE matrix and the ductile nature of the matrix itself.

  17. Preparation and hemostatic property of low molecular weight silk fibroin.

    PubMed

    Lei, Caihong; Zhu, Hailin; Li, Jingjing; Feng, Xinxing; Chen, Jianyong

    2016-01-01

    Effective hemorrhage control becomes increasingly significant in today's military and civilian trauma, while the topical hemostats currently available in market still have various disadvantages. In this study, three low molecular weight silk fibroins (LMSF) were prepared through hydrolysis of silk fibroin in a ternary solvent system of CaCl2/H2O/EtOH solution at different hydrolysis temperatures. Fourier transform infrared spectroscopy analysis showed that the content of β sheet structure in the LMSF decreased with the increase in hydrolysis temperature. The results of thromboelastographic and activated partial thromboplastin time methods showed that the LMSF hydrolyzed at 50 °C can significantly strengthen the coagulation in blood and activate the intrinsic pathway of coagulation cascade. In the murine hepatic injury model, the LMSF hydrolyzed at 50 °C can promote the blood clotting and decrease the blood loss and bleeding time. Based on these results, it can be suggested that the developed LMSF has the excellent hemostatic effect and may be a promising material in clinical hemostatic application. PMID:26732018

  18. Delamination toughness of ultra high molecular weight polyethylene (UHMWPE) composites

    NASA Astrophysics Data System (ADS)

    Porras, A.; Tellez, J.; Casas-Rodriguez, J. P.

    2012-08-01

    Ultra high molecular weight polyethylene (UHMWPE) fibre reinforced composites are an important group of material for armours solutions, where their unique combination of properties could be utilized. A commonly observed failure mode in this kind of unidirectional laminated composites under impact ballistic is delamination between the composite layers. In the present study, an investigation on the delamination toughness behaviour exhibited by UHMWPE composites laminated was made. The interlaminar Mode II critical strain energy release rates of (UHMWPE) fibre reinforced composites were characterized using the End Notch Flexural (ENF) test. Critical strain energy release rate was obtained from the load - deflection test data using the beam theory expression. It was found that the energy release rate of the composite exhibited a very low value of around 60J/m2 using a moulding pressure of approximately 1200 psi. In order to analyse the delamination resistance of composite, the effects of changing the manufacture process variables and the use of a thermoplastic adhesive film in the composites were investigated. The composite laminates were produced by hot compressing moulding using a film-stacking procedure. It was found that the damage resistance of the UHMWPE composite was influenced by the manufacture method, which affects the Mode II interlaminar fracture toughness and the ballistic response of composites.

  19. Antiaging activity of low molecular weight peptide from Paphia undulate

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Cai, Bingna; Chen, Hua; Pan, Jianyu; Chen, Deke; Sun, Huili

    2013-05-01

    Low molecular weight peptide (LMWP) was prepared from clam Paphia undulate and its antiaging effect on D-galactose-induced acute aging in rats, aged Kunming mice, ultraviolet-exposed rats, and thermally injured rats was investigated. P. undulate flesh was homogenized and digested using papain under optimal conditions, then subjected to Sephadex G-25 chromatography to isolate the LMWP. Administration of LMWP significantly reversed D-galactose-induced oxidative stress by increasing the activities of glutathione peroxidase (GPx) and catalase (CAT), and by decreasing the level of malondialdehyde (MDA). This process was accompanied by increased collagen synthesis. The LMWP prevented photoaging and promoted dermis recovery and remission of elastic fiber hyperplasia. Furthermore, treatment with the LMWP helped to regenerate elastic fibers and the collagen network, increased superoxide dismutase (SOD) in the serum and significantly decreased MDA. Thermal scald-induced inflammation and edema were also relieved by the LWMP, while wound healing in skin was promoted. These results suggest that the LMWP from P. undulate could serve as a new antiaging substance in cosmetics.

  20. Molecular Weight-Dependent Immunostimulative Activity of Low Molecular Weight Chitosan via Regulating NF-κB and AP-1 Signaling Pathways in RAW264.7 Macrophages

    PubMed Central

    Zheng, Bin; Wen, Zheng-Shun; Huang, Yun-Juan; Xia, Mei-Sheng; Xiang, Xing-Wei; Qu, You-Le

    2016-01-01

    Chitosan and its derivatives such as low molecular weight chitosans (LMWCs) have been found to possess many important biological properties, such as antioxidant and antitumor effects. In our previous study, LMWCs were found to elicit a strong immunomodulatory response in macrophages dependent on molecular weight. Herein we further investigated the molecular weight-dependent immunostimulative activity of LMWCs and elucidated its mechanism of action on RAW264.7 macrophages. LMWCs (3 kDa and 50 kDa of molecular weight) could significantly enhance the mRNA expression levels of COX-2, IL-10 and MCP-1 in a molecular weight and concentration-dependent manner. The results suggested that LMWCs elicited a significant immunomodulatory response, which was dependent on the dose and the molecular weight. Regarding the possible molecular mechanism of action, LMWCs promoted the expression of the genes of key molecules in NF-κB and AP-1 pathways, including IKKβ, TRAF6 and JNK1, and induced the phosphorylation of protein IKBα in RAW264.7 macrophage. Moreover, LMWCs increased nuclear translocation of p65 and activation of activator protein-1 (AP-1, C-Jun and C-Fos) in a molecular weight-dependent manner. Taken together, our findings suggested that LMWCs exert immunostimulative activity via activation of NF-κB and AP-1 pathways in RAW264.7 macrophages in a molecular weight-dependent manner and that 3 kDa LMWC shows great potential as a novel agent for the treatment of immune suppression diseases and in future vaccines. PMID:27657093

  1. The association of low-molecular-weight hydrophobic compounds with native casein micelles in bovine milk.

    PubMed

    Cheema, M; Mohan, M S; Campagna, S R; Jurat-Fuentes, J L; Harte, F M

    2015-08-01

    The agreed biological function of the casein micelles in milk is to carry minerals (calcium, magnesium, and phosphorus) from mother to young along with amino acids for growth and development. Recently, native and modified casein micelles were used as encapsulating and delivery agents for various hydrophobic low-molecular-weight probes. The ability of modified casein micelles to bind certain probes may derive from the binding affinity of native casein micelles. Hence, a study with milk from single cows was conducted to further elucidate the association of hydrophobic molecules into native casein micelles and further understand their biological function. Hydrophobic and hydrophilic extraction followed by ultraperformance liquid chromatography-high resolution mass spectrometry analysis were performed over protein fractions obtained from size exclusion fractionation of raw skim milk. Hydrophobic compounds, including phosphatidylcholine, lyso-phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin, showed strong association exclusively to casein micelles as compared with whey proteins, whereas hydrophilic compounds did not display any preference for their association among milk proteins. Further analysis using liquid chromatography-tandem mass spectrometry detected 42 compounds associated solely with the casein-micelles fraction. Mass fragments in tandem mass spectrometry identified 4 of these compounds as phosphatidylcholine with fatty acid composition of 16:0/18:1, 14:0/16:0, 16:0/16:0, and 18:1/18:0. These results support that transporting low-molecular-weight hydrophobic molecules is also a biological function of the casein micelles in milk.

  2. Polymerization degrees, molecular weights and protein-binding affinities of condensed tannin fractions from a Leucaena leucocephala hybrid.

    PubMed

    Saminathan, Mookiah; Tan, Hui Yin; Sieo, Chin Chin; Abdullah, Norhani; Wong, Clemente Michael Vui Ling; Abdulmalek, Emilia; Ho, Yin Wan

    2014-01-01

    Condensed tannins (CTs) form insoluble complexes with proteins and are able to protect them from degradation, which could lead to rumen bypass proteins. Depending on their degrees of polymerization (DP) and molecular weights, CT fractions vary in their capability to bind proteins. In this study, purified condensed tannins (CTs) from a Leucaena leucocephala hybrid were fractionated into five different molecular weight fractions. The structures of the CT fractions were investigated using 13C-NMR. The DP of the CT fractions were determined using a modified vanillin assay and their molecular weights were determined using Q-TOF LC-MS. The protein-binding affinities of the respective CT fractions were determined using a protein precipitation assay. The DP of the five CT fractions (fractions F1-F5) measured by the vanillin assay in acetic acid ranged from 4.86 to 1.56. The 13C-NMR results showed that the CT fractions possessed monomer unit structural heterogeneity. The number-average molecular weights (Mn) of the different fractions were 1265.8, 1028.6, 652.2, 562.2, and 469.6 for fractions F1, F2, F3, F4, and F5, respectively. The b values representing the CT quantities needed to bind half of the maximum precipitable bovine serum albumin increased with decreasing molecular weight--from fraction F1 to fraction F5 with values of 0.216, 0.295, 0.359, 0.425, and 0.460, respectively. This indicated that higher molecular weight fractions of CTs from L. leucocephala have higher protein-binding affinities than those with lower molecular weights. PMID:24927368

  3. Degradation mechanisms of bioresorbable polyesters. Part 2. Effects of initial molecular weight and residual monomer.

    PubMed

    Gleadall, Andrew; Pan, Jingzhe; Kruft, Marc-Anton; Kellomäki, Minna

    2014-05-01

    This paper presents an understanding of how initial molecular weight and initial monomer fraction affect the degradation of bioresorbable polymers in terms of the underlying hydrolysis mechanisms. A mathematical model was used to analyse the effects of initial molecular weight for various hydrolysis mechanisms including noncatalytic random scission, autocatalytic random scission, noncatalytic end scission or autocatalytic end scission. Different behaviours were identified to relate initial molecular weight to the molecular weight half-life and to the time until the onset of mass loss. The behaviours were validated by fitting the model to experimental data for molecular weight reduction and mass loss of samples with different initial molecular weights. Several publications that consider initial molecular weight were reviewed. The effect of residual monomer on degradation was also analysed, and shown to accelerate the reduction of molecular weight and mass loss. An inverse square root law relationship was found between molecular weight half-life and initial monomer fraction for autocatalytic hydrolysis. The relationship was tested by fitting the model to experimental data with various residual monomer contents.

  4. Chromatographic molecular weight measurements for heparin, its fragments and fractions, and other glycosaminoglycans.

    PubMed

    Mulloy, Barbara; Hogwood, John

    2015-01-01

    Glycosaminoglycan samples are usually polydisperse, consisting of molecules with differing length and differing sequence. Methods for measuring the molecular weight of heparin have been developed to assure the quality and consistency of heparin products for medicinal use, and these methods can be applied in other laboratory contexts. In the method described here, high-performance gel permeation chromatography is calibrated using appropriate heparin molecular weight markers or a single broad standard calibrant, and used to characterize the molecular weight distribution of polydisperse samples or the peak molecular weight of monodisperse, or approximately monodisperse, heparin fractions. The same technology can be adapted for use with other glycosaminoglycans.

  5. Effects of polymer molecular weight on relative oral bioavailability of curcumin

    PubMed Central

    Tsai, Yin-Meng; Chang-Liao, Wan-Ling; Chien, Chao-Feng; Lin, Lie-Chwen; Tsai, Tung-Hu

    2012-01-01

    Background Polylactic-co-glycolic acid (PLGA) nanoparticles have been used to increase the relative oral bioavailability of hydrophobic compounds and polyphenols in recent years, but the effects of the molecular weight of PLGA on bioavailability are still unknown. This study investigated the influence of polymer molecular weight on the relative oral bioavailability of curcumin, and explored the possible mechanism accounting for the outcome. Methods Curcumin encapsulated in low (5000–15,000) and high (40,000–75,000) molecular weight PLGA (LMw-NPC and HMw-NPC, respectively) were prepared using an emulsification-solvent evaporation method. Curcumin alone and in the nanoformulations was administered orally to freely mobile rats, and blood samples were collected to evaluate the bioavailability of curcumin, LMw-NPC, and HMw-NPC. An ex vivo experimental gut absorption model was used to investigate the effects of different molecular weights of PLGA formulation on absorption of curcumin. High-performance liquid chromatography with diode array detection was used for quantification of curcumin in biosamples. Results There were no significant differences in particle properties between LMw-NPC and HMw-NPC, but the relative bioavailability of HMw-NPC was 1.67-fold and 40-fold higher than that of LMw-NPC and conventional curcumin, respectively. In addition, the mean peak concentration (Cmax) of conventional curcumin, LMw-NPC, and HMw-NPC was 0.028, 0.042, and 0.057 μg/mL, respectively. The gut absorption study further revealed that the HMw-PLGA formulation markedly increased the absorption rate of curcumin in the duodenum and resulted in excellent bioavailability compared with conventional curcumin and LMw-NPC. Conclusion Our findings demonstrate that different molecular weights of PLGA have varying bioavailability, contributing to changes in the absorption rate at the duodenum. The results of this study provide the rationale for design of a nanomedicine delivery system to

  6. Molecular resolution and fragmentation of fulvic acid by electrospray ionization/multistage tandem mass spectrometry

    USGS Publications Warehouse

    Leenheer, J.A.; Rostad, C.E.; Gates, Paul M.; Furlong, E.T.; Ferrer, I.

    2001-01-01

    Molecular weight distributions of fulvic acid from the Suwannee River, Georgia, were investigated by electrospray ionization/quadrupole mass spectrometry (ESI/QMS), and fragmentation pathways of specific fulvic acid masses were investigated by electrospray ionization/ion trap multistage tandem mass spectrometry (ESI/MST/MS). ESI/QMS studies of the free acid form of low molecular weight poly(carboxylic acid) standards in 75% methanol/25% water mobile phase found that negative ion detection gave the optimum generation of parent ions that can be used for molecular weight determinations. However, experiments with poly(acrylic acid) mixtures and specific high molecular weight standards found multiply charged negative ions that gave a low bias to molecular mass distributions. The number of negative charges on a molecule is dependent on the distance between charges. ESI/MST/MS of model compounds found characteristic water loss from alcohol dehydration and anhydride formation, as well as CO2 loss from decarboxylation, and CO loss from ester structures. Application of these fragmentation pathways to specific masses of fulvic acid isolated and fragmented by ESI/MST/MS is indicative of specific structures that can serve as a basis for future structural confirmation after these hypothesized structures are synthesized.

  7. Molecular imprinted polymer-coated optical fiber sensor for the identification of low molecular weight molecules.

    PubMed

    Lépinay, Sandrine; Ianoul, Anatoli; Albert, Jacques

    2014-10-01

    A biomimetic optical probe for detecting low molecular weight molecules (maltol, 3-hydroxy-2-methyl-4H-pyran-4-one, molecular weight of 126.11 g/mol), was designed, fabricated, and characterized. The sensor couples a molecular imprinted polymer (MIP) and the Bragg grating refractometry technology into an optical fiber. The probe is fabricated first by inscribing tilted grating planes in the core of the fiber, and then by photopolymerization to immobilize a maltol imprinted MIP on the fiber cladding surface over the Bragg grating. The sensor response to the presence of maltol in different media is obtained by spectral interrogation of the fiber transmission signal. The results showed that the limit of detection of the sensor reached 1 ng/mL in pure water with a sensitivity of 6.3 × 10(8)pm/M. The selectivity of the sensor against other compounds and its reusability were also studied experimentally. Finally, the unambiguous detection of concentrations as little as 10nM of maltol in complex media (real food samples) by the MIP-coated tilted fiber Bragg grating sensor was demonstrated.

  8. Respiratory clearance of aerosolized radioactive solutes of varying molecular weight

    SciTech Connect

    Huchon, G.J.; Montgomery, A.B.; Lipavsky, A.; Hoeffel, J.M.; Murray, J.F.

    1987-05-01

    To determine the influence of varying molecular weight (mol wt) on respiratory clearance of aerosolized solutes, we studied eight radiopharmaceuticals, each administered to four dogs: sodium /sup 99m/Tc pertechnetate (TcO4), /sup 99m/Tc glucoheptonate ((/sup 99m/Tc)GH), 51Cr-ethylenedinitrotetraacetate ((51Cr)EDTA), /sup 99m/Tc diethylenetriaminepentaacetate ((99mTc) DTPA), /sup 111/In diethylenetriaminepentaacetate ((/sup 111/In)DTPA), /sup 67/Ga desferoxaminemesylate ((/sup 67/Ga)DFOM), /sup 99m/Tc dextran ((/sup 99m/Tc)DX) and /sup 111/In transferrin ((/sup 111/In)TF). After aerosolization (0.8 m MMD, 2.4 GSD), clearance was determined for 30 min and then corrected by intravenous injection for nonairspace radioactivity. In-TF clearance (0.11 +/- 0.10%/min) was lower than TcO4 (6.32 +/- 0.62%/min), (/sup 99m/Tc)GH (1.50 +/- 0.37%/min), (/sup 51/Cr)EDTA (2.38 +/- 1.02%/min), (/sup 99m/Tc)DTPA (3.51 +/- 0.40%/min), (/sup 111/In)DTPA (2.35 +/- 0.42%/min), (/sup 67/Ga) DFOM (1.99 +/- 0.49%/min) and (/sup 99m/Tc)DX (1.81 +/- 0.75%/min) clearances (p less than 0.001). TcO4 clearance was higher than others (p less than 0.001). Technetium binding to DX was unsatisfactory; aerosolization caused unbinding from DTPA. We conclude that respiratory clearance of large mol wt solutes within 30 min is negligible and, that clearance of molecules between 347-5099 daltons differs greatly, suggesting that binding and/or intrapulmonary retention affect transfer.

  9. [Practical use of low molecular weight heparins in angiology].

    PubMed

    Plettner, J L

    1991-01-01

    The recent development of low molecular weight heparins (LMWH), obtained by the depolymerization of standard non-fractioned heparin (NFH), considerably simplifies the course of anticoagulant treatments. They now allow effectively and safely dealing with the risks of thrombosis, both in hospital and at the patient's home. Their effectiveness for both the prevention and the treatment of thromboembolic accidents has been proved by many clinical trials. In comparison to standard heparin, the LMWHs still have a high anti-Xa activity, but their anti-IIa action is much reduced, thus preserving their antithrombotic power while reducing the hemorrhagic risks. Owing to their better bioavailability and longer half-life, they allow using in priority the subcutaneous route, reducing the frequency of the injections and simplifying surveillance, without impairing the effectiveness of the treatment. The prevention of thrombosis with LMWHs requires one daily subcutaneous dose. The control of the anti-Xa activity is not necessary for the doses used. Prior to initiating a curative treatment, it is essential to confirm the existence of thrombosis. When the diagnosis is definitive, the three LMWHs currently known are used after reconversion, at a dosage of 100 IU/kg/12 hrs. The anti-Xa activity, in samples taken 3 to 4 hours after the injection, must be maintained between 0.5 and 1 IU anti-Xa/ml. It is prudent to control the platelet level at D5 and D10, although thrombocytopenia is exceptional. The changeover treatment with antivitamins K (AVK), which is essential to prevent the recurrence of venous thrombosis, is initiated very early (2nd or 3rd day).(ABSTRACT TRUNCATED AT 250 WORDS)

  10. High Molecular Weight Petrogenic and Pyrogenic Hydrocarbons in Aquatic Environments

    NASA Astrophysics Data System (ADS)

    Abrajano, T. A., Jr.; Yan, B.; O'Malley, V.

    2003-12-01

    Geochemistry is ultimately the study of sources, movement, and fate of chemicals in the geosphere at various spatial and temporal scales. Environmental organic geochemistry focuses such studies on organic compounds of toxicological and ecological concern (e.g., Schwarzenbach et al., 1993, 1998; Eganhouse, 1997). This field emphasizes not only those compounds with potential toxicological properties, but also the geological systems accessible to the biological receptors of those hazards. Hence, the examples presented in this chapter focus on hydrocarbons with known health and ecological concern in accessible shallow, primarily aquatic, environments.Modern society depends on oil for energy and a variety of other daily needs, with present mineral oil consumption throughout the 1990s exceeding 3×109 t yr-1 (NRC, 2002). In the USA, e.g., ˜40% of energy consumed and 97% of transportation fuels are derived from oil. In the process of extraction, refinement, transport, use, and waste production, a small but environmentally significant fraction of raw oil materials, processed products, and waste are released inadvertently or purposefully into the environment. Because their presence and concentration in the shallow environments are often the result of human activities, these organic materials are generally referred to as "environmental contaminants." Although such reference connotes some form of toxicological or ecological hazard, specific health or ecological effects of many organic "environmental contaminants" remain to be demonstrated. Some are, in fact, likely innocuous at the levels that they are found in many systems, and simply adds to the milieu of biogenic organic compounds that naturally cycle through the shallow environment. Indeed, virtually all compounds in crude oil and processed petroleum products have been introduced naturally to the shallow environments as oil and gas seepage for millions of years ( NRC, 2002). Even high molecular weight (HMW) polyaromatic

  11. Yield, Esterification Degree and Molecular Weight Evaluation of Pectins Isolated from Orange and Grapefruit Peels under Different Conditions

    PubMed Central

    Sayah, Mohamed Yassine; Chabir, Rachida; Benyahia, Hamid; Rodi Kandri, Youssef; Ouazzani Chahdi, Fouad; Touzani, Hanan; Errachidi, Faouzi

    2016-01-01

    Orange (Citrus sinensis) and grapefruit (Citrus paradise) peels were used as a source of pectin, which was extracted under different conditions. The peels are used under two states: fresh and residual (after essential oil extraction). Organic acid (citric acid) and mineral acid (sulfuric acid) were used in the pectin extraction. The aim of this study is the evaluation the effect of extraction conditions on pectin yield, degree of esterification “DE” and on molecular weight “Mw”. Results showed that the pectin yield was higher using the residual peels. Moreover, both peels allow the obtainment of a high methoxyl pectin with DE >50%. The molecular weight was calculated using Mark-Houwink-Sakurada equation which describes its relationship with intrinsic viscosity. This later was determined using four equations; Huggins equation, kramer, Schulz-Blaschke and Martin equation. The molecular weight varied from 1.538 x1005 to 2.47x1005 g/mol for grapefruit pectin and from 1.639 x1005 to 2.471 x1005 g/mol for orange pectin. PMID:27644093

  12. Yield, Esterification Degree and Molecular Weight Evaluation of Pectins Isolated from Orange and Grapefruit Peels under Different Conditions.

    PubMed

    Sayah, Mohamed Yassine; Chabir, Rachida; Benyahia, Hamid; Rodi Kandri, Youssef; Ouazzani Chahdi, Fouad; Touzani, Hanan; Errachidi, Faouzi

    2016-01-01

    Orange (Citrus sinensis) and grapefruit (Citrus paradise) peels were used as a source of pectin, which was extracted under different conditions. The peels are used under two states: fresh and residual (after essential oil extraction). Organic acid (citric acid) and mineral acid (sulfuric acid) were used in the pectin extraction. The aim of this study is the evaluation the effect of extraction conditions on pectin yield, degree of esterification "DE" and on molecular weight "Mw". Results showed that the pectin yield was higher using the residual peels. Moreover, both peels allow the obtainment of a high methoxyl pectin with DE >50%. The molecular weight was calculated using Mark-Houwink-Sakurada equation which describes its relationship with intrinsic viscosity. This later was determined using four equations; Huggins equation, kramer, Schulz-Blaschke and Martin equation. The molecular weight varied from 1.538 x1005 to 2.47x1005 g/mol for grapefruit pectin and from 1.639 x1005 to 2.471 x1005 g/mol for orange pectin. PMID:27644093

  13. Influence of polycation molecular weight on poly(2-dimethylaminoethyl methacrylate)-mediated DNA delivery in vitro.

    PubMed

    Layman, John M; Ramirez, Sean M; Green, Matthew D; Long, Timothy E

    2009-05-11

    Establishing clear structure-property-transfection relationships is a critical step in the development of clinically relevant polymers for nonviral gene therapy. In this study, we determined the influence of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) molecular weight on cytotoxicity, DNA binding, and in vitro plasmid DNA delivery efficiency in human brain microvascular endothelial cells (HBMEC). Conventional free radical polymerization was used to synthesize PDMAEMA with weight-average molecular weights ranging from 43,000 to 915,000 g/mol. MTT and LDH assays revealed that lower molecular weight PDMAEMA (M(w) = 43,000 g/mol) was slightly less toxic than higher molecular weights (M(w) > 112,000 g/mol) and that the primary mode of toxicity was cellular membrane destabilization. An electrophoretic gel shift assay revealed that all PDMAEMA molecular weights completely bound with plasmid DNA. However, heparin competitive binding experiments revealed that higher molecular weight PDMAEMA (M(w) = 915,000 g/mol) had a greater binding affinity toward plasmid DNA than lower molecular weight PDMAEMA (M(w) = 43,000 g/mol). The molecular weight of PDMAEMA was found to have a dramatic influence on transfection efficiency, and luciferase reporter gene expression increased as a function of increasing molecular weight. However, cellular uptake of polyplexes was determined to be insensitive to PDMAEMA molecular weight. In addition, our data did not correlate polyplex size with transfection efficiency. Collectively, our data suggested that the intracellular fate of the polyplexes, which involves endosomal release and DNase resistance, is more important to overall transfection efficiency than barriers to entry, such as polyplex size.

  14. Effects of protein molecular weight on the intrinsic material properties and release kinetics of wet spun polymeric microfiber delivery systems.

    PubMed

    Lavin, Danya M; Zhang, Linda; Furtado, Stacia; Hopkins, Richard A; Mathiowitz, Edith

    2013-01-01

    Wet spun microfibers have great potential for the design of multifunctional controlled release scaffolds. Understanding aspects of drug delivery and mechanical strength, specific to protein molecular weight, may aid in the optimization and development of wet spun fiber platforms. This study investigated the intrinsic material properties and release kinetics of poly(l-lactic acid) (PLLA) and poly(lactic-co-glycolic acid) (PLGA) wet spun microfibers encapsulating proteins with varying molecular weights. A cryogenic emulsion technique developed in our laboratory was used to encapsulate insulin (5.8 kDa), lysozyme (14.3 kDa) and bovine serum albumin (BSA, 66.0 kDa) within wet spun microfibers (~100 μm). Protein loading was found to significantly influence mechanical strength and drug release kinetics of PLGA and PLLA microfibers in a molecular-weight-dependent manner. BSA encapsulation resulted in the most significant decrease in strength and ductility for both PLGA and PLLA microfibers. Interestingly, BSA-loaded PLGA microfibers had a twofold increase (8±2 MPa to 16±1 MPa) in tensile strength and a fourfold increase (3±1% to 12±6%) in elongation until failure in comparison to PLLA microfibers. PLGA and PLLA microfibers exhibited prolonged protein release up to 63 days in vitro. Further analysis with the Korsmeyer-Peppas kinetic model determined that the mechanism of protein release was dependent on Fickian diffusion. These results emphasize the critical role protein molecular weight has on the properties of wet spun filaments, highlighting the importance of designing small molecular analogues to replace growth factors with large molecular weights.

  15. Development of implants for sustained release of 5-fluorouracil using low molecular weight biodegradable polymers.

    PubMed

    Hanafy, A Fh; El-Egaky, A M; Mortada, S A; Molokhia, A M

    2009-12-01

    Anticancer drugs have poor efficacy especially against solid tumors that hinder drug penetration into the tumor. Thus, the dose has to be increased, but toxicity is a limiting factor. Local administration of a polymeric biodegradable poly-L-lactic acid (PLA) and poly(L-lactic acid-co-glycolic acid) copolymer (PLGA) implant containing an anticancer drug may be an acceptable method of concentrating the drug near the tumor site. This work sought to synthesize low molecular weight PLA and PLGA by polycondensation to yield polymers with good physical properties to make them suitable for use in implantable therapy. The synthesized polymers were characterized by determining their molecular weight, melting point, and percentage crystallinity using DSC. Fourier transformationinfra red spectrum (FT-IR), nuclear magnetic resonance (NMR) and specific optical rotation measurement were also used to characterize the synthesized polymers. Morphological characteristics were assessed using scanning electron microscopy (SEM). Implants were manufactured using compression (C) and injection molding (IM) and were loaded with 12 mg 5-fluorouracil (5-FU) per 120 mg implant. In vitro release patterns of all implants were assessed in phosphate buffered saline pH 7.4 (PBS 7.4) at 37°C. Factors affecting the release of 5-FU from implants were the polymer species, manufacturing technique, drug particle size, drug concentration, implant dimensions, and coating of the implant. Implants prepared with PLGA had significantly faster release of 5-FU than those prepared with PLA. Those manufactured using compression had significantly faster drug release than those prepared by injection molding. A PLA implant that contained 12 mg 5-FU/120 mg with a diameter of 0.3 cm and that was loaded with a drug particle size smaller than 150 μm and prepared by injection molding and then subsequently coated with PLA had the longest release period of 45 days.

  16. 21 CFR 178.3750 - Polyethylene glycol (mean molecular weight 200-9,500).

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Polyethylene glycol (mean molecular weight 200-9..., PRODUCTION AIDS, AND SANITIZERS Certain Adjuvants and Production Aids § 178.3750 Polyethylene glycol (mean molecular weight 200-9,500). Polyethylene glycol identified in this section may be safely used as...

  17. 21 CFR 172.820 - Polyethylene glycol (mean molecular weight 200-9,500).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Polyethylene glycol (mean molecular weight 200-9... ADDITION TO FOOD FOR HUMAN CONSUMPTION Multipurpose Additives § 172.820 Polyethylene glycol (mean molecular weight 200-9,500). Polyethylene glycol identified in this section may be safely used in food...

  18. 21 CFR 178.3750 - Polyethylene glycol (mean molecular weight 200-9,500).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Polyethylene glycol (mean molecular weight 200-9..., PRODUCTION AIDS, AND SANITIZERS Certain Adjuvants and Production Aids § 178.3750 Polyethylene glycol (mean molecular weight 200-9,500). Polyethylene glycol identified in this section may be safely used as...

  19. 21 CFR 172.820 - Polyethylene glycol (mean molecular weight 200-9,500).

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Polyethylene glycol (mean molecular weight 200-9... ADDITION TO FOOD FOR HUMAN CONSUMPTION Multipurpose Additives § 172.820 Polyethylene glycol (mean molecular weight 200-9,500). Polyethylene glycol identified in this section may be safely used in food...

  20. A Simple, Inexpensive Molecular Weight Measurement for Water-Soluble Polymers Using Microemulsions.

    ERIC Educational Resources Information Center

    Mathias, Lon J.; Moore, D. Roger

    1985-01-01

    Describes an experiment involving use of a microemulsion and its characteristic thermal phase change to determine molecular weights of polyoxyethylene samples. The experiment provides students with background information on polymers and organized media and with experience in evaluating polymer molecular weight by using a unique property of a…

  1. Formation of high molecular weight products from benzene during boundary lubrication

    NASA Technical Reports Server (NTRS)

    Morales, W.

    1985-01-01

    High molecular weight products were detected on the wear track of an iron disk at the end of a sliding friction and wear test using benzene as a lubricant. Size exclusion chromagography in conjunction with UV analysis gave evidence that the high molecular weight products are polyphenyl ether type substances. Organic electrochemistry was used to elucidate the possible surface reaction mechanisms.

  2. Molecular Weight Determination by an Improved Temperature-Monitored Vapor-Density Method.

    ERIC Educational Resources Information Center

    Grider, Douglas J.; And Others

    1988-01-01

    Recommends determining molecular weights of liquids by use of a thermocouple. Utilizing a mathematical gas equation, the molecular weight can be determined from the measurement of the vapor temperature upon complete evaporation. Lists benefits as reduced time and cost, and improved safety factors. (ML)

  3. Fluorophore-assisted carbohydrate electrophoresis for the determination of molecular mass of heparins and low-molecular-weight (LMW) heparins.

    PubMed

    Buzzega, Dania; Maccari, Francesca; Volpi, Nicola

    2008-11-01

    We report the use of fluorophore-assisted carbohydrate electrophoresis (FACE) to determine the molecular mass (M) values of heparins (Heps) and low-molecular-weight (LMW)-Hep derivatives. Hep are labeled with 8-aminonaphthalene-1,3,6-trisulfonic acid and FACE is able to resolve each fraction as a discrete band depending on their M. After densitometric acquisition, the migration distance of each Hep standard is acquired and the third-grade polynomial calibration standard curve is determined by plotting the logarithms of the M values as a function of migration ratio. Purified Hep samples having different properties, pharmaceutical Heps and various LMW-Heps were analyzed by both FACE and conventional high-performance size-exclusion liquid chromatography (HPSEC) methods. The molecular weight value on the top of the chromatographic peak (Mp), the number-average Mn, weight-average Mw and polydispersity (Mw/Mn) were examined by both techniques and found to be similar. This approach offers certain advantages over the HPSEC method. The derivatization process with 8-aminonaphthalene-1,3,6-trisulfonic acid is complete after 4 h so that many samples may be analyzed in a day also considering that multiple samples can be run simultaneously and in parallel and that a single FACE analysis requires approx. 15 min. Furthermore, FACE is a very sensitive method as it requires approx. 5-10 microg of Heps, about 10-100-fold lower than samples and standards used in HPSEC evaluation. Finally, the utilization of mini-gels allows the use of very low amounts of reagents with neither expensive equipment nor any complicated procedures having to be applied. This study demonstrates that FACE analysis is a sensitive method for the determination of the M values of Heps and LMW-Heps with possible utilization in virtually any kind of research and development such as quality control laboratories due to its rapid, parallel analysis of multiple samples by means of common and simple largely used

  4. Low molecular weight proteinuria in Chinese herbs nephropathy.

    PubMed

    Kabanda, A; Jadoul, M; Lauwerys, R; Bernard, A; van Ypersele de Strihou, C

    1995-11-01

    Urinary excretion of five low molecular weight proteins (LMWP) [beta 2-microglobulin (beta 2m), cystatin C (cyst C), Clara cell protein (CC16), retinol-binding protein (RBP) and alpha 1-microglobulin (alpha 1m)], albumin and N-acetyl-beta-D-glucosaminidase (NAG) were quantified in 16 patients who followed a weight reduction program which included Chinese herbs, which have been incriminated in the genesis of Chinese herbs nephropathy (CHN). An additional group of four patients transplanted for CHN were investigated. Urinary data were obtained for comparison purpose in five groups of proteinuric patients: two groups with normal serum creatinine (SCr) and glomerular albuminura [12 patients with diabetes mellitus and microalbuminuria (DN), 10 patients with primary nephrotic syndrome (NS)]; two groups with normal SCr and toxic nephropathy [6 patients with analgesic (AN), 9 patients with cadmium nephropathy (CdN)]; and one group of seven patients with glomerular diseases and increased SCr (GN). Patients were classified according to serum level S beta 2m to take into account the possibility of overflow proteinuria at S beta 2m > or = 5 mg/liter. Three patients (CHN0) with a S beta 2m < 5 mg/liter, had a normal urinary protein pattern including NAG and a normal S beta 2m. Eight patients (CHN1) with a S beta 2m < 5 mg/liter had various abnormalities of their urinary protein pattern. In four of them (CHN1a) only beta 2m, RBP and CC16 were increased while total proteinuria and SCr were normal. In the other four (CHN1b and c) albumin, cyst C, alpha 1m and NAG were also elevated, while total proteinuria and SCr were moderately raised. Five patients (CHN2) with a S beta 2m > or = 5 mg/liter had a markedly increased excretion of all LMWP, albumin and NAG (CHN1 vs. CHN2, P < 0.05) as well as a further increase in total proteinuria and SCr. The urinary LMWP/albumin concentration ratio was strikingly higher in CHN patients than in patients with glomerular albuminuria (CHN1 vs. DN

  5. Molecular chaperone properties of the high molecular weight aggregate from aged lens

    NASA Technical Reports Server (NTRS)

    Takemoto, L.; Boyle, D.; Spooner, B. S. (Principal Investigator)

    1994-01-01

    The high molecular weight aggregate (HMWA) fraction was isolated from the water soluble proteins of aged bovine lenses. Its composition and ability to inhibit heat-induced denaturation and aggregation were compared with the lower molecular weight, oligomeric fraction of alpha isolated from the same lens. Although the major components of both fractions were the alpha-A and alpha-B chains, the HMWA fraction possessed a decreased ability to protect other proteins against heat-induced denaturation and aggregation. Immunoelectron microscopy of both fractions demonstrated that alpha particles from the HMWA fraction contained increased amounts of beta and gamma crystallins, bound to a central region of the supramolecular complex. Together, these results demonstrate that alpha crystallins found in the HMWA fraction possess a decreased ability to protect against heat-induced denaturation and aggregation, and suggest that at least part of this decrease could be due to the increased presence of beta and gamma crystallins complexed to the putative chaperone receptor site of the alpha particles.

  6. Bacterial degradation of high molecular-weight polynuclear aromatic hydrocarbons

    SciTech Connect

    Ye, D.; Siddiqi, A.; Kumar, S.; Sikka, H.C.

    1995-12-31

    The ability of Pseudomonas paucimobilis, strain EPA 505 (a soil bacterium capable of utilizing fluoranthene as the sole source of carbon and energy for growth) to metabolize a variety of high molecular-weight polynuclear aromatic hydrocarbons (PAHs) was investigated. After 16 hours of incubation with 10 ppm of a PAH, a resting cell suspension (1 mg wet cells/ml) of P. paucimobilis grown on fluoranthene degraded 80.0, 72.9, 31.5, 33.3, 12.5, and 7.8% of pyrene, benz[a]anthracene (B[a]A), chrysene, benzo[a]pyrene (B[a]P), benzo[b]fluoranthene (B[b]F), and dibenz[a,h]anthracene (DB[a,h]A), respectively. No degradation of dibenz[a,1]pyrene was detected under these conditions. Studies with [7-{sup 14}C]B[a]P and [5,6,11,12-{sup 14}C]chrysene showed that after 48 hours of incubation, the cells degraded nearly 28 and 42% of {sup 14}C-B[a]P and {sup 14}C-chrysene to {sup 14} C0{sub 2}, respectively, suggesting that the bacterium is able to metabolize B[a]P and chrysene via ring cleavage. No evolution of {sup 14}CO{sub 2} was detected from cultures incubated with [4,5,9,10{sup 14}C]pyrene or [1,2,3,4,4a,4bU-{sup 14}C]dibenz[a,1]pyrene. The degradation of B[a]P with P. paucimobilis significantly reduced the mutagenic activity associated with the hydrocarbon. The addition of 5 ppm of B[a]A, chrysene, fluoranthene, or DB[a,h]A to the incubation medium containing 5 ppm B[a]P had no effect on the degradation of B[a]P by P. paucimobilis. The data suggest that P. paucimobilis, strain EPA 505 may be useful for remediation of PAH-contaminated sites.

  7. Bioremediation of Mixtures of High Molecular Weight Polycyclic Aromatic Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Xu, H.; Wu, J.; Shi, X.; Sun, Y.

    2014-12-01

    Although bioremediation has been considered as one of the most promising means to remove polycyclic aromatic hydrocarbons (PAHs) from polluted environments, the efficacy of PAHs bioremediation still remains challenged, especially for high molecular weight PAHs (HMW PAHs) and their mixtures. This study was focused on (a) isolation and characterization of pure strain and mixed microbial communities able to degrade HMW PAHs and (b) further evaluation of the ability of the isolated microbes to degrade HMW PAHs mixtures in the absence and presence of indigenous flora. Fluoranthene, benzo[b]fluoranthene and pyrene were selected as the representative HMW PAHs in this study. A pure bacterial strain, identified as Herbaspirillum chlorophenolicum FA1, was isolated from activated sludge. A mixed bacterial community designated as consortium-4 was isolated from petroleum contaminated soils, containing Pseudomonas sp. FbP1、Enterobacter sp. FbP2、Hydrogenophaga sp. FbP3 and Luteolibacter pohnpeiensis. FbP4. To our knowledge, this is the first study to demonstrate that bacterial strains of Herbaspirillum chlorophenolicum FA1 and Luteolibacter pohnpeiensis. FbP4 can also degrade fluoranthene, benzo[b]fluoranthene and pyrene. Experiment results showed that both strain FA1 and consortium-4 could degrade fluoranthene, benzo[b]fluoranthene and pyrene within a wide range of temperature, pH and initial PAHs concentration. Degradation of HMW PAHs mixtures (binary and ternary) demonstrated the interactive effects that can alter the rate and extent of biodegradation within a mixture. The presence of indigenous flora was found to either increase or decrease the degradation of HMW PAHs, suggesting possible synergistic or competition effects. Biodegradation kinetics of HMW PAHs for sole substrates, binary and ternary systems was evaluated, with the purpose to better characterize and compare the biodegradation process of individual HMW PAH and mixtures of HMW PAHs. Results of this study

  8. Multitarget molecular hybrids of cinnamic acids.

    PubMed

    Peperidou, Aikaterini; Kapoukranidou, Dorothea; Kontogiorgis, Christos; Hadjipavlou-Litina, Dimitra

    2014-12-02

    In an attempt to synthesize potential new multitarget agents, 11 novel hybrids incorporating cinnamic acids and paracetamol, 4-/7-hydroxycoumarin, benzocaine, p-aminophenol and m-aminophenol were synthesized. Three hybrids-2e, 2a, 2g-and 3b were found to be multifunctional agents. The hybrid 2e derived from the phenoxyphenyl cinnamic acid and m-acetamidophenol showed the highest lipoxygenase (LOX) inhibition and analgesic activity (IC50 = 0.34 μΜ and 98.1%, whereas the hybrid 3b of bromobenzyloxycinnamic acid and hymechromone exhibited simultaneously good LOX inhibitory activity (IC50 = 50 μΜ) and the highest anti-proteolytic activity (IC50= 5 μΜ). The hybrid 2a of phenyloxyphenyl acid with paracetamol showed a high analgesic activity (91%) and appears to be a promising agent for treating peripheral nerve injuries. Hybrid 2g which has an ester and an amide bond presents an interesting combination of anti-LOX and anti-proteolytic activity. The esters were found very potent and especially those derived from paracetamol and m-acetamidophenol. The amides follow. Based on 2D-structure-activity relationships it was observed that both steric and electronic parameters play major roles in the activity of these compounds. Molecular docking studies point to the fact that allosteric interactions might govern the LOX-inhibitor binding.

  9. Antiedematogenic and antioxidant properties of high molecular weight protein sub-fraction of Calotropis procera latex in rat

    PubMed Central

    Chaudhary, Priyanka; de Araújo Viana, Carolina; Ramos, Marcio V.; Kumar, Vijay L.

    2015-01-01

    Objectives: The aim was to evaluate the effect of high molecular weight protein fraction of Calotropis procera latex on edema formation and oxidative stress in carrageenan-induced paw inflammation. Methods: A sub-plantar injection of carrageenan was given to induce edema in the hind paw of the rat. The inhibitory effect of high molecular weight protein fraction of C. procera latex was evaluated following intravenous administration (5 and 25 mg/kg body weight) and was compared with that of diclofenac given orally (5 mg/kg). The levels of reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARS) and myeloperoxidase (MPO) were measured in the inflamed paw tissue at the end of the study. Results: The high molecular weight protein fraction obtained from the latex of C. procera produced a dose-dependent inhibition of edema formation that was accompanied by normalization of levels of oxidative stress markers (GSH and TBARS) and MPO, a marker for neutrophils in the paw tissue. Conclusions: The high molecular weight protein fraction of C. procera latex ameliorates acute inflammation in the paw through its antioxidant effect. PMID:25767367

  10. Isolation of low-molecular-weight heparin/heparan sulfate from marine sources.

    PubMed

    Saravanan, Ramachandran

    2014-01-01

    The glycosaminoglycan (heparin and heparan sulfate) are polyanionic sulfated polysaccharides mostly recognized for its anticoagulant activity. In many countries, low-molecular-weight heparins have replaced the unfractionated heparin, owing to its high bioavailability, half-life, and less adverse effect. The low-molecular-weight heparins differ in mode of preparation (chemical or enzymatic synthesis and chromatography fractionations) and as a consequence in molecular weight distribution, chemical structure, and pharmacological activities. Bovine and porcine body parts are at present used for manufacturing of commercial heparins, and the appearance of mad cow disease and Creutzfeldt-Jakob disease in humans has limited the use of bovine heparin. Consequently, marine organisms come across the new resource for the production of low-molecular-weight heparin and heparan sulfate. The importance of this chapter suggests that the low-molecular-weight heparin and heparan sulfate from marine species could be alternative sources for commercial heparin. PMID:25081076

  11. Antioxidative low molecular weight compounds in marinated herring (Clupea harengus) salt brine.

    PubMed

    Gringer, Nina; Safafar, Hamed; du Mesnildot, Axelle; Nielsen, Henrik H; Rogowska-Wrzesinska, Adelina; Undeland, Ingrid; Baron, Caroline P

    2016-03-01

    This study aimed at unravelling the antioxidative capacity of low molecular weight compounds (LMWC) (peptides, amino acids and phenolic acids) present in salt brines from the marinated herring production. Brines were fractionated into <10kDa fractions using dialysis and further into 94 fractions using size exclusion chromatography. All samples were analysed for protein, total phenolic content (TPC) and antioxidant activities. Protein-enriched samples were pooled (P1, P2 and P3) and analysed for phenolic acids, total amino acids and peptide/protein sequence using advanced mass spectrometry. All salt brines contain LMWC holding ABTS-radical scavenging activity, reducing power and iron chelating activity. Generally, a strong correlation between TPC and ABTS-radical scavenging was found. In contrast, reducing power and iron chelating activity seemed to be caused by peptides. Protein/peptide sequencing revealed 1kDa peptides with the presence of HDF-motif which could be responsible for some of the antioxidant capacity observed in marinated herring salt brine. PMID:26471668

  12. Antioxidative low molecular weight compounds in marinated herring (Clupea harengus) salt brine.

    PubMed

    Gringer, Nina; Safafar, Hamed; du Mesnildot, Axelle; Nielsen, Henrik H; Rogowska-Wrzesinska, Adelina; Undeland, Ingrid; Baron, Caroline P

    2016-03-01

    This study aimed at unravelling the antioxidative capacity of low molecular weight compounds (LMWC) (peptides, amino acids and phenolic acids) present in salt brines from the marinated herring production. Brines were fractionated into <10kDa fractions using dialysis and further into 94 fractions using size exclusion chromatography. All samples were analysed for protein, total phenolic content (TPC) and antioxidant activities. Protein-enriched samples were pooled (P1, P2 and P3) and analysed for phenolic acids, total amino acids and peptide/protein sequence using advanced mass spectrometry. All salt brines contain LMWC holding ABTS-radical scavenging activity, reducing power and iron chelating activity. Generally, a strong correlation between TPC and ABTS-radical scavenging was found. In contrast, reducing power and iron chelating activity seemed to be caused by peptides. Protein/peptide sequencing revealed 1kDa peptides with the presence of HDF-motif which could be responsible for some of the antioxidant capacity observed in marinated herring salt brine.

  13. Effect of molecular weight reduction by gamma irradiation on chitosan film properties.

    PubMed

    García, Mario A; Pérez, Liliam; de la Paz, Nilia; González, Juan; Rapado, Manuel; Casariego, Alicia

    2015-10-01

    The present work aimed the influence of molecular weight (MW) reduction by irradiation with (60)Co and polymer concentration on some physical properties of chitosan films. Irradiation of chitosan with a MW of 275.221 kDa and 74.74% of deacetylation degree was performed using a (60)Co source to provide doses of 5, 10, 20 and 50 kGy to obtain chitosans with molecular weights of 247.847, 221.563, 126.469 and 77.063 kDa, respectively. Films were prepared via the solution casting method. Film-forming solutions (FFS) of chitosan irradiated or not, were prepared at 1.5 and 2% (w/v) in a solution of lactic acid at 1% (v/v) and 0.1% (v/v) of Tween 80. The FFS were poured into glass plates of 400 cm(2) and dried at 60 °C during 10h without airflow. The decrease of MW and increase of chitosan concentration increased the tensil strength and water vapor permeability while decreased the elongation at break of the films. The chitosan MW did not significantly influence (p>0.05) the water solubility of films within a same polymer concentration. There was a decrease in the films' brightness with the increase of concentration and a decrease of the MW of irradiated chitosan, while the b* values of films increased and there was an increasing tendency of their apparent opacity.

  14. Comprehensive Analysis of Low-Molecular-Weight Human Plasma Proteome Using Top-Down Mass Spectrometry.

    PubMed

    Cheon, Dong Huey; Nam, Eun Ji; Park, Kyu Hyung; Woo, Se Joon; Lee, Hye Jin; Kim, Hee Cheol; Yang, Eun Gyeong; Lee, Cheolju; Lee, Ji Eun

    2016-01-01

    While human plasma serves as a great source for disease diagnosis, low-molecular-weight (LMW) proteome (<30 kDa) has been shown to contain a rich source of diagnostic biomarkers. Here we employ top-down mass spectrometry to analyze the LMW proteoforms present in four types of human plasma samples pooled from three healthy controls (HCs) without immunoaffinity depletion and with depletion of the top two, six, and seven high-abundance proteins. The LMW proteoforms were first fractionated based on molecular weight using gel-eluted liquid fraction entrapment electrophoresis (GELFrEE). Then, the GELFrEE fractions containing up to 30 kDa were subjected to nanocapillary-LC-MS/MS, and the high-resolution MS and MS/MS data were processed using ProSightPC 3.0. As a result, a total of 442 LMW proteins and cleaved products, including those with post-translational modifications and single amino acid variations, were identified. From additional comparative analysis of plasma samples without immunoaffinity depletion between HCs and colorectal cancer (CRC) patients via top-down approach, tens of LMW proteoforms, including platelet factor 4, were found to show >1.5-fold changes between the plasma samples of HCs and CRC patients, and six of the LMW proteins were verified by Western blot analysis.

  15. Capillary Electrophoresis-Mass Spectrometry for the Analysis of Heparin Oligosaccharides and Low Molecular Weight Heparin.

    PubMed

    Sun, Xiaojun; Lin, Lei; Liu, Xinyue; Zhang, Fuming; Chi, Lianli; Xia, Qiangwei; Linhardt, Robert J

    2016-02-01

    Heparins, highly sulfated, linear polysaccharides also known as glycosaminoglycans, are among the most challenging biopolymers to analyze. Hyphenated techniques in conjunction with mass spectrometry (MS) offer rapid analysis of complex glycosaminoglycan mixtures, providing detailed structural and quantitative data. Previous analytical approaches have often relied on liquid chromatography (LC)-MS, and some have limitations including long separation times, low resolution of oligosaccharide mixtures, incompatibility of eluents, and often require oligosaccharide derivatization. This study examines the analysis of glycosaminoglycan oligosaccharides using a novel electrokinetic pump-based capillary electrophoresis (CE)-MS interface. CE separation and electrospray were optimized using a volatile ammonium bicarbonate electrolyte and a methanol-formic acid sheath fluid. The online analyses of highly sulfated heparin oligosaccharides, ranging from disaccharides to low molecular weight heparins, were performed within a 10 min time frame, offering an opportunity for higher-throughput analysis. Disaccharide compositional analysis as well as top-down analysis of low molecular weight heparin was demonstrated. Using normal polarity CE separation and positive-ion electrospray ionization MS, excellent run-to-run reproducibility (relative standard deviation of 3.6-5.1% for peak area and 0.2-0.4% for peak migration time) and sensitivity (limit of quantification of 2.0-5.9 ng/mL and limit of detection of 0.6-1.8 ng/mL) could be achieved.

  16. An asparagines residue at the N-terminus affects the maturation process of low molecular weight glutenin subunits of wheat endosperm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wheat (Triticum spp.) glutenin polymers are of two main types, high- (HMW-GS) and low- (LMW-GS) molecular weight subunits. The most common are the latter, based on the first amino acid of the mature sequence, are known as LMW-m and LMW-s types. They differ as a result of three extra amino acids (MET...

  17. Optical properties of polycarbonate/styrene-co-acrylonitrile blends: effects of molecular weight of the matrix.

    PubMed

    Yi, Ping; Xiong, Ying; Guo, Shaoyun

    2015-12-01

    In this paper, the effects of the molecular weight of a polycarbonate (PC) matrix on the phase morphology and optical properties of a PC/styrene-co-acrylonitrile (SAN) blend were investigated. A scanning electron microscope is used to analyze the phase morphology of the blends, and Mie scattering theory is used to analyze the changing laws of the optical properties of PC/SAN blends with the increasing of PC molecular weight. Results show that the average particle diameter is not strongly changed with different PC molecular weight because the values of the viscosity ratios are very close to each other. But it is obvious that the number of large particles gradually reduced while small particles (especially d<2  μm) significantly increased with the increasing of PC molecular weight. And the increase in small particles will result in an increase in backward scattering so the transmittance of PC/SAN blends decreases with the increase of PC molecular weight. However, the balance of the scattering coefficients and the number concentration of particles eventually lead to the haze of the blends being very close, despite having different PC molecular weights. Meanwhile, the photographs of scattering patterns indicate that the PC/SAN blends whose component weight ratios are fixed at 70:30 have excellent antiglare properties, despite the changes in molecular weight of the PC matrix.

  18. Macroscopic birefringence in liquid crystals from novel cyanobacterial polysaccharide with an extremely high molecular weight

    NASA Astrophysics Data System (ADS)

    Okajima-Kaneko, Maiko; Hayasaka-Kaneko, Daisaku; Miyazato, Shinji; Kaneko, Tatsuo

    2007-05-01

    We report an efficient method for extraction of anionic polysaccharides (PS) from cyanobacteria, Aphanothece sacrum; we used a hot alkaline solution (0.01 N NaOH) as an elution solvent in the first step of the extraction and isopropanol as a precipitation solvent in the last step. Thin fibers of PS were obtained at a high yield (50-80 % to the weight of the raw cyanobacterial sample). The spectroscopy and elemental analyses indicated the PS contains fucose, uronic acids (14.2 % by a carbazole-sulfuric acid method), a sugar unit containing amides. The solution of PS with a concentration of 1 wt% showed a very high viscosity (80 000cps) implying a high molecular weight, and a strong macroscopic birefringence with a texture typical of nematic liquid crystals was confirmed by crossed-polarizing microscopy (more than 0.5 wt%). The PS from A. sacrum may form a special structure rigid-rod enough to show LC phase and macroscopic birefringence.

  19. Study on Different Molecular Weights of Chitosan as an Immobilization Matrix for a Glucose Biosensor

    PubMed Central

    Ang, Lee Fung; Por, Lip Yee; Yam, Mun Fei

    2013-01-01

    Two chitosan samples (medium molecular weight (MMCHI) and low molecular weight (LMCHI)) were investigated as an enzyme immobilization matrix for the fabrication of a glucose biosensor. Chitosan membranes prepared from acetic acid were flexible, transparent, smooth and quick-drying. The FTIR spectra showed the existence of intermolecular interactions between chitosan and glucose oxidase (GOD). Higher catalytic activities were observed on for GOD-MMCHI than GOD-LMCHI and for those crosslinked with glutaraldehyde than using the adsorption technique. Enzyme loading greater than 0.6 mg decreased the activity. Under optimum conditions (pH 6.0, 35°C and applied potential of 0.6 V) response times of 85 s and 65 s were observed for medium molecular weight chitosan glucose biosensor (GOD-MMCHI/PT) and low molecular weight chitosan glucose biosensor (GOD-LMCHI/PT), respectively. The apparent Michaelis-Menten constant () was found to be 12.737 mM for GOD-MMCHI/PT and 17.692 mM for GOD-LMCHI/PT. This indicated that GOD-MMCHI/PT had greater affinity for the enzyme. Moreover, GOD-MMCHI/PT showed higher sensitivity (52.3666 nA/mM glucose) when compared with GOD-LMCHI/PT (9.8579 nA/mM glucose) at S/N>3. Better repeatability and reproducibility were achieved with GOD-MMCHI/PT than GOD-LMCHI/PT regarding glucose measurement. GOD-MMCHI/PT was found to give the highest enzymatic activity among the electrodes under investigation. The extent of interference encountered by GOD-MMCHI/PT and GOD-LMCHI/PT was not significantly different. Although the Nafion coated biosensor significantly reduced the signal due to the interferents under study, it also significantly reduced the response to glucose. The performance of the biosensors in the determination of glucose in rat serum was evaluated. Comparatively better accuracy and recovery results were obtained for GOD-MMCHI/PT. Hence, GOD-MMCHI/PT showed a better performance when compared with GOD-LMCHI/PT. In conclusion, chitosan membranes shave

  20. Influence of molecular-weight polydispersity on the glass transition of polymers.

    PubMed

    Li, Shu-Jia; Xie, Shi-Jie; Li, Yan-Chun; Qian, Hu-Jun; Lu, Zhong-Yuan

    2016-01-01

    It is well known that the polymer glass transition temperature T_{g} is dependent on molecular weight, but the role of molecular-weight polydispersity on T_{g} is unclear. Using molecular-dynamics simulations, we clarify that for polymers with the same number-average molecular weight, the molecular-weight distribution profile (either in Schulz-Zimm form or in bimodal form) has very little influence on the glass transition temperature T_{g}, the average segment dynamics (monomer motion, bond orientation relaxation, and torsion transition), and the relaxation-time spectrum, which are related to the local nature of the glass transition. By analyzing monomer motions in different chains, we find that the motion distribution of monomers is altered by molecular-weight polydispersity. Molecular-weight polydispersity dramatically enhances the dynamic heterogeneity of monomer diffusive motions after breaking out of the "cage," but it has a weak influence on the dynamic heterogeneity of the short time scales and the transient spatial correlation between temporarily localized monomers. The stringlike cooperative motion is also not influenced by molecular-weight polydispersity, supporting the idea that stringlike collective motion is not strongly correlated with chain connectivity.

  1. Boswellic acids: biological actions and molecular targets.

    PubMed

    Poeckel, Daniel; Werz, Oliver

    2006-01-01

    Gum resin extracts of Boswellia species have been traditionally applied in folk medicine for centuries to treat various chronic inflammatory diseases, and experimental data from animal models and studies with human subjects confirmed the potential of B. spec extracts for the treatment of not only inflammation but also of cancer. Analysis of the ingredients of these extracts revealed that the pentacyclic triterpenes boswellic acids (BAs) possess biological activities and appear to be responsible for the respective pharmacological actions. Approaches in order to elucidate the molecular mechanisms underlying the biological effects of BAs identified 5-lipoxygenase, human leukocyte elastase, toposiomerase I and II, as well as IkappaB kinases as molecular targets of BAs. Moreover, it was shown that depending on the cell type and the structure of the BAs, the compounds differentially interfere with signal transduction pathways including Ca(2+/-) and MAPK signaling in various blood cells, related to functional cellular processes important for inflammatory reactions and tumor growth. This review summarizes the biological actions of BAs on the cellular and molecular level and attempts to put the data into perspective of the beneficial effects manifested in animal studies and trials with human subjects related to inflammation and cancer.

  2. Detection and some properties of a high molecular weight toxin in the hypobranchial gland of strawberry conch Strombus luhuanus.

    PubMed

    Abiko, Keisuke; Iwayama, Ayane; Shiomi, Kazuo

    2015-10-01

    The extract from the hypobranchial gland of strawberry conch Strombus luhuanus was found to be lethal to mice. There were no marked regional and seasonal variations in toxicity although a considerable individual variation was recognized. The toxin was thermostable and extractable with aqueous solvents but not with organic solvents. Behaviors in dialysis, ultrafiltration and column chromatography on various adsorbents suggested that the toxin is a high molecular weight acidic substance of 400-500 k.

  3. Detection and some properties of a high molecular weight toxin in the hypobranchial gland of strawberry conch Strombus luhuanus.

    PubMed

    Abiko, Keisuke; Iwayama, Ayane; Shiomi, Kazuo

    2015-10-01

    The extract from the hypobranchial gland of strawberry conch Strombus luhuanus was found to be lethal to mice. There were no marked regional and seasonal variations in toxicity although a considerable individual variation was recognized. The toxin was thermostable and extractable with aqueous solvents but not with organic solvents. Behaviors in dialysis, ultrafiltration and column chromatography on various adsorbents suggested that the toxin is a high molecular weight acidic substance of 400-500 k. PMID:26299337

  4. Developer molecular size dependence of pattern formation of polymer type electron beam resists with various molecular weights

    NASA Astrophysics Data System (ADS)

    Takayama, Tomohiro; Asada, Hironori; Kishimura, Yukiko; Ochiai, Shunsuke; Hoshino, Ryoichi; Kawata, Atsushi

    2016-05-01

    The sensitivity and the resolution are affected by not only the nature of the resist such as a chemical structure and a molecular weight but also the developing process such as a developer molecular size. Exposure characteristics of positive-tone polymer resists having various molecular weights (Mw's) ranging from 60 k to 500 k are investigated using different ester solvents as a developer. The line-and-space (L/S) patterns are exposed by the electron beam writing system with an acceleration voltage of 50 kV and the samples are developed by amyl acetate, hexyl acetate and heptyl acetate. The pattern shape becomes better and the surface of the resist also becomes smoother with increasing developer molecular size, though the exposure dose required for the formation of the L/S pattern increases. The dose margin of pattern formation is also wider in all the resists having the different molecular weights. The dissolution in the unexposed portions of the 60k-Mw resist for heptyl acetate is reduced significantly compared with those for amyl acetate and hexyl acetate. The improvement of the pattern shape and the increasing of dose margin are remarkable in the low molecular weight resist. The 3σ of line width roughness tends to be smaller in the higher molecular weight resist and with the larger molecular size developer. Exposure experiment of the 35 nm pitch pattern using the 500k-Mw resist developed at the room temperature is presented.

  5. Low-Molecular-Weight Organo- and Hydrogelators Based on Cyclo(l-Lys-l-Glu).

    PubMed

    Geng, Huimin; Ye, Lin; Zhang, Ai-Ying; Li, Jingbo; Feng, Zeng-Guo

    2016-05-10

    Four cyclo(l-Lys-l-Glu) derivatives (3-6) were synthesized from the coupling reaction of protecting l-lysine with l-glutamic acid followed by the cyclization, deprotection, and protection reactions. They can efficiently gelate a wide variety of organic solvents or water. Interestingly, a spontaneous chemical reaction proceeded in the organogel obtained from 3 in acetone exhibiting not only visual color alteration but also increasing mechanical strength with the progress of time due to the formation of Schiff base. Moreover, 6 bearing a carboxylic acid and Fmoc group displayed a robust hydrogelation capability in PBS solution. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the characteristic gelation morphologies of 3D fibrous network structures in the resulting organo- and hydrogels. FT-IR and fluorescence analyses indicated that the hydrogen bonding and π-π stacking play as major driving forces for the self-assembly of these cyclic dipeptides as low-molecular-weight gelators. X-ray diffraction (XRD) measurements and computer modeling provided information on the molecular packing model in the hydrogelation state of 6. A spontaneous chemical reaction proceeded in the organogel obtained from 3 in acetone exhibiting visual color alteration and increasing mechanical strength. 6 bearing an optimized balance of hydrophilicity to lipophilicity gave rise to a hydrogel in PBS with MGC at 1 mg/mL. PMID:27101967

  6. Increased production of low molecular weight recombinant proteins in Escherichia coli.

    PubMed

    Belagaje, R M; Reams, S G; Ly, S C; Prouty, W F

    1997-09-01

    A general method for obtaining high-level production of low molecular weight proteins in Escherichia coli is described. This method is based on the use of a novel Met-Xaa-protein construction which is formed by insertion of a single amino acid residue (preferably Arginine or Lysine) between the N-terminal methionine and the protein of interest. The utility of this method is illustrated by examples for achieving high-level production of human insulin-like growth factor-1, human proinsulin, and their analogs. Furthermore, highly produced insulin-like growth factor-1 derivatives and human proinsulin analogs are converted to their natural sequences by removal of dipeptides with cathepsin C.

  7. Surface modification of ultra high molecular weight polyethylene fibers via the sequential photoinduced graft polymerization

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Zhang, Wei; Wang, Xinwei; Mai, Yongyi; Zhang, Yumei

    2011-06-01

    In this study, a sequential photoinduced graft polymerization process was proposed to improve the poor interfacial bonding property of ultra high molecular weight polyethylene (UHMWPE) fibers. The polymerization was initiated by dormant semipinacol (SP) groups and carried out in a thin liquid layer. Methacrylic acid (MAA) and acryl amide (AM) were grafted stepwise onto the surface of UHMWPE fibers. Attenuated total reflectance infrared spectroscopy (ATR-IR) and thermo gravimetric analysis (TGA) confirmed the grafting. The analysis result of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) indicated the structure of grafted chains. Scanning electron microscopy (SEM) images and atomic force microscopy (AFM) images revealed the apparent morphology changing, and the grafted layers were observed. Interfacial shear stress (IFSS) test of the modified fibers showed an extensively improved interfacial bonding property. The active groups grafted onto the fibers would supply enough anchor points for the chemical bonding with various resins or further reactions.

  8. Low-molecular-weight thiols in plants: functional and analytical implications.

    PubMed

    Pivato, Micaela; Fabrega-Prats, Marta; Masi, Antonio

    2014-10-15

    Low-molecular-weight (LMW) thiols are a class of highly reactive compounds massively involved in the maintenance of cellular redox homeostasis. They are implicated in plant responses to almost all stress factors, as well as in the regulation of cellular metabolism. The most studied LMW thiols are glutathione and its biosynthetically related compounds (cysteine, γ-glutamylcysteine, cysteinylglycine, and phytochelatins). Other LMW thiols are described in the literature, such as thiocysteine, cysteamine, homocysteine, lipoic acid, and many species-specific volatile thiols. Here, we review the known LMW thiols in plants, briefly describing their physico-chemical properties, their relevance in post-translational protein modification, and recently-developed thiol detection methods. Current research points to a huge thiol biodiversity in plants and many species-specific and organ-specific thiols remain to be identified. Recent advances in technology should help researchers in this very challenging task, helping us to decipher the roles of thiols in plant metabolism. PMID:25057770

  9. Oxidation of ultrahigh molecular weight polyethylene characterized by Fourier Transform Infrared Spectrometry.

    PubMed

    Goldman, M; Lee, M; Gronsky, R; Pruitt, L

    1997-10-01

    The effects of processing conditions, sterilization treatment, aging time, and poststerilization aging environment on the oxidation behavior of ultrahigh molecular weight polyethylene (UHMWPE) are examined. Oxidation is monitored by observing changes in the carbonyl peak appearing in Fourier Transform Infrared Spectrometry (FTIR) and is found to be relatively insensitive to processing conditions but strongly influenced by sterilization treatments and aging parameters. Oxygen uptake by UHMWPE increases as a result of gamma or electron beam irradiation and continues to rise during subsequent aging at a rate influenced by the aging environment. A hydrogen peroxide ambient causes more severe oxidation than either air or hyaluronic acid. Control (unsterilized) samples and those sterilized in ethylene oxide are resistant to oxidation under all conditions except hydrogen peroxide aging.

  10. Low-molecular-weight thiols in plants: functional and analytical implications.

    PubMed

    Pivato, Micaela; Fabrega-Prats, Marta; Masi, Antonio

    2014-10-15

    Low-molecular-weight (LMW) thiols are a class of highly reactive compounds massively involved in the maintenance of cellular redox homeostasis. They are implicated in plant responses to almost all stress factors, as well as in the regulation of cellular metabolism. The most studied LMW thiols are glutathione and its biosynthetically related compounds (cysteine, γ-glutamylcysteine, cysteinylglycine, and phytochelatins). Other LMW thiols are described in the literature, such as thiocysteine, cysteamine, homocysteine, lipoic acid, and many species-specific volatile thiols. Here, we review the known LMW thiols in plants, briefly describing their physico-chemical properties, their relevance in post-translational protein modification, and recently-developed thiol detection methods. Current research points to a huge thiol biodiversity in plants and many species-specific and organ-specific thiols remain to be identified. Recent advances in technology should help researchers in this very challenging task, helping us to decipher the roles of thiols in plant metabolism.

  11. Effect of soil sieving on respiration induced by low-molecular-weight substrates

    NASA Astrophysics Data System (ADS)

    Datta, Rahul; Vranová, Valerie; Pavelka, Marian; Rejšek, Klement; Formánek, Pavel

    2014-03-01

    The mesh size of sieves has a significant impact upon soil disturbance, affecting pore structure, fungal hyphae, proportion of fungi to bacteria, and organic matter fractions. The effects are dependent upon soil type and plant coverage. Sieving through a 2 mm mesh increases mineralization of exogenously supplied carbohydrates and phenolics compared to a 5 mm mesh and the effect is significant (p<0.05), especially in organic horizons, due to increased microbial metabolism and alteration of other soil properties. Finer mesh size particularly increases arabinose, mannose, galactose, ferulic and pthalic acid metabolism, whereas maltose mineralization is less affected. Sieving through a 5 mm mesh size is suggested for all type of experiments where enhanced mineralization of low-molecular-weight organic compounds needs to be minimalized.

  12. Formation mechanism of monodisperse, low molecular weight chitosan nanoparticles by ionic gelation technique.

    PubMed

    Fan, Wen; Yan, Wei; Xu, Zushun; Ni, Hong

    2012-02-01

    Chitosan nanoparticles have been extensively studied for drug and gene delivery. In this paper, monodisperse, low molecular weight (LMW) chitosan nanoparticles were prepared by a novel method based on ionic gelation using sodium tripolyphosphate (TPP) as cross-linking agent. The objective of this study was to solve the problem of preparation of chitosan/TPP nanoparticles with high degree of monodispersity and stability, and investigate the effect of various parameters on the formation of LMW chitosan/TPP nanoparticles. It was found that the particle size distribution of the nanoparticles could be significantly narrowed by a combination of decreasing the concentration of acetic acid and reducing the ambient temperature during cross-linking process. The optimized nanoparticles exhibited a mean hydrodynamic diameter of 138 nm with a polydispersity index (PDI) of 0.026 and a zeta potential of +35 mV, the nanoparticles had good storage stability at room temperature up to at least 20 days.

  13. Immunostimulative Activity of Low Molecular Weight Chitosans in RAW264.7 Macrophages

    PubMed Central

    Wu, Ning; Wen, Zheng-Shun; Xiang, Xing-Wei; Huang, Yan-Na; Gao, Yang; Qu, You-Le

    2015-01-01

    Chitosan and its derivatives such as low molecular weight chitosans (LMWCs) have been reported to exert many biological activities, such as antioxidant and antitumor effects. However, complex and molecular weight dependent effects of chitosan remain controversial and the mechanisms that mediate these complex effects are still poorly defined. This study was carried out to investigate the immunostimulative effect of different molecular weight chitosan in RAW264.7 macrophages. Our data suggested that two LMWCs (molecular weight of 3 kDa and 50 kDa) both possessed immunostimulative activity, which was dependent on dose and, at the higher doses, also on the molecular weight. LMWCs could significantly enhance the the pinocytic activity, and induce the production of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), interferon-γ (IFN-γ), nitric oxide (NO) and inducible nitric oxide synthase (iNOS) in a molecular weight and concentration-dependent manner. LMWCs were further showed to promote the expression of the genes including iNOS, TNF-α. Taken together, our findings suggested that LMWCs elicited significantly immunomodulatory response through up-regulating mRNA expression of proinflammatory cytokines and activated RAW264.7 macrophage in a molecular weight- and concentration-dependent manner. PMID:26437419

  14. How does the preparation of rye porridge affect molecular weight distribution of extractable dietary fibers?

    PubMed

    Rakha, Allah; Aman, Per; Andersson, Roger

    2011-01-01

    Extractable dietary fiber (DF) plays an important role in nutrition. This study on porridge making with whole grain rye investigated the effect of rest time of flour slurries at room temperature before cooking and amount of flour and salt in the recipe on the content of DF components and molecular weight distribution of extractable fructan, mixed linkage (1→3)(1→4)-β-d-glucan (β-glucan) and arabinoxylan (AX) in the porridge. The content of total DF was increased (from about 20% to 23% of dry matter) during porridge making due to formation of insoluble resistant starch. A small but significant increase in the extractability of β-glucan (P = 0.016) and AX (P = 0.002) due to rest time was also noted. The molecular weight of extractable fructan and AX remained stable during porridge making. However, incubation of the rye flour slurries at increased temperature resulted in a significant decrease in extractable AX molecular weight. The molecular weight of extractable β-glucan decreased greatly during a rest time before cooking, most likely by the action of endogenous enzymes. The amount of salt and flour used in the recipe had small but significant effects on the molecular weight of β-glucan. These results show that whole grain rye porridge made without a rest time before cooking contains extractable DF components maintaining high molecular weights. High molecular weight is most likely of nutritional importance.

  15. How Does the Preparation of Rye Porridge Affect Molecular Weight Distribution of Extractable Dietary Fibers?

    PubMed Central

    Rakha, Allah; Åman, Per; Andersson, Roger

    2011-01-01

    Extractable dietary fiber (DF) plays an important role in nutrition. This study on porridge making with whole grain rye investigated the effect of rest time of flour slurries at room temperature before cooking and amount of flour and salt in the recipe on the content of DF components and molecular weight distribution of extractable fructan, mixed linkage (1→3)(1→4)-β-d-glucan (β-glucan) and arabinoxylan (AX) in the porridge. The content of total DF was increased (from about 20% to 23% of dry matter) during porridge making due to formation of insoluble resistant starch. A small but significant increase in the extractability of β-glucan (P = 0.016) and AX (P = 0.002) due to rest time was also noted. The molecular weight of extractable fructan and AX remained stable during porridge making. However, incubation of the rye flour slurries at increased temperature resulted in a significant decrease in extractable AX molecular weight. The molecular weight of extractable β-glucan decreased greatly during a rest time before cooking, most likely by the action of endogenous enzymes. The amount of salt and flour used in the recipe had small but significant effects on the molecular weight of β-glucan. These results show that whole grain rye porridge made without a rest time before cooking contains extractable DF components maintaining high molecular weights. High molecular weight is most likely of nutritional importance. PMID:21686191

  16. Immunostimulative Activity of Low Molecular Weight Chitosans in RAW264.7 Macrophages.

    PubMed

    Wu, Ning; Wen, Zheng-Shun; Xiang, Xing-Wei; Huang, Yan-Na; Gao, Yang; Qu, You-Le

    2015-09-30

    Chitosan and its derivatives such as low molecular weight chitosans (LMWCs) have been reported to exert many biological activities, such as antioxidant and antitumor effects. However, complex and molecular weight dependent effects of chitosan remain controversial and the mechanisms that mediate these complex effects are still poorly defined. This study was carried out to investigate the immunostimulative effect of different molecular weight chitosan in RAW264.7 macrophages. Our data suggested that two LMWCs (molecular weight of 3 kDa and 50 kDa) both possessed immunostimulative activity, which was dependent on dose and, at the higher doses, also on the molecular weight. LMWCs could significantly enhance the the pinocytic activity, and induce the production of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), interferon-γ (IFN-γ), nitric oxide (NO) and inducible nitric oxide synthase (iNOS) in a molecular weight and concentration-dependent manner. LMWCs were further showed to promote the expression of the genes including iNOS, TNF-α. Taken together, our findings suggested that LMWCs elicited significantly immunomodulatory response through up-regulating mRNA expression of proinflammatory cytokines and activated RAW264.7 macrophage in a molecular weight- and concentration-dependent manner.

  17. Novel Ion-Exchange Coagulants Remove More Low Molecular Weight Organics than Traditional Coagulants.

    PubMed

    Zhao, Huazhang; Wang, Lei; Hanigan, David; Westerhoff, Paul; Ni, Jinren

    2016-04-01

    Low molecular weight (MW) charged organic matter is poorly removed by conventional coagulants but contributes to disinfection byproduct formation during chlorination of drinking waters. We hypothesized that CIEX, a new Al-based hybrid coagulant with ion-exchange functional groups, would be new mechanistic approach to remove low MW organic matter during coagulation and would perform better than polyaluminum chloride (PACl) or metal-salt based coagulants. We measured coagulation performance using dissolved organic carbon (DOC) in a high hardness surface water. CIEX achieved excellent turbidity removal and removed 20% to 46% more DOC than FeCl3, Al2(SO4)3, or PACl, depending on dose. The improved DOC removal was attributable to better removal of low MW organic matter (<2 kDa). We further studied removal mechanisms in a model water containing a low MW organic acid (salicylic acid (SA)). CIEX achieved high removal of organic acids (>90% of SA) independent of pH, whereas removal by metal salts was lower (<15%) and was strongly pH dependent. CIEX ion-exchange capability is facilitated by its covalently bound quaternary ammonium group, which conventional coagulants lack. Plus, unlike other cationic polymers that react with chloramines to form N-nitrosodimethylamine (NDMA), CIEX has a low molar yield (9.3 × 10(-7) mol NDMA per mol CIEX-N).

  18. Purification of a high-molecular-weight somatoliberin (growth-hormone-releasing factor) from pig hypothalami.

    PubMed Central

    Sykes, J E; Lowry, P J

    1983-01-01

    Preliminary observations [Sykes & Lowry (1980) J. Endocrinol. 85, 42P-43P] had suggested that the major hypothalamic somatoliberin (growth-hormone-releasing factor) was a larger peptide than the other characterized hypothalamic factors, with an elution position on Sephadex G-50 between those of neurophysin and corticotropin. The present paper reports the isolation and preliminary characterization of pig hypothalamic somatoliberin. Acid extracts of pig stalk median eminence were purified by gel filtration and preparative and analytical high-pressure liquid chromatography to yield a preparation that was specific in the release of somatotropin (growth hormone) in vitro, giving a steep dose--response curve at doses in the range 0.20-3.0 ng. Amino acid analysis revealed a non-cysteine-containing peptide with a high number of glutamate (or glutamine) and aspartate (or asparagine) residues. The peptide had about 56-57 amino acid residues and an apparent molecular weight of 6400, in keeping with its elution position on a column of Sephadex G-50. PMID:6409074

  19. Molecular dynamics simulation study of methanesulfonic acid.

    PubMed

    Canales, Manel; Alemán, Carlos

    2014-03-27

    A molecular dynamics simulation study of methanesulfonic acid has been carried out using a reliable force field in a large range of temperatures. Several thermodynamic, structural, and dynamical properties have been calculated and compared with the available experimental data. The density, the shear viscosity, the heat of vaporization, and the melting temperature results, calculated from this force field, are in a good agreement with the experimental data. Analysis of the influence of the hydrogen bonds in structural and dynamical properties has also been performed. The continuous and interrupted methodologies to compute hydrogen bonding lifetimes have been applied. The interrupted hydrogen bond lifetimes values are consistent with the diffusion and viscosity coefficients. The activation energies of the self-diffusion, the reorientational motions, and the hydrogen bonding lifetimes are coincident.

  20. Investigation of Changes in the Microscopic Structure of Anionic Poly(N-isopropylacrylamide-co-Acrylic acid) Microgels in the Presence of Cationic Organic Dyes toward Precisely Controlled Uptake/Release of Low-Molecular-Weight Chemical Compound.

    PubMed

    Kureha, Takuma; Shibamoto, Takahisa; Matsui, Shusuke; Sato, Takaaki; Suzuki, Daisuke

    2016-05-10

    Changes in a microscopic structure of an anionic poly(N-isopropylacrylamide-co-acrylic acid) microgel were investigated using small- and wide-angle X-ray scattering (SWAXS). The scattering profiles of the microgels were analyzed in a wide scattering vector (q) range of 0.07 ≤ q/nm(-1) ≤ 20. In particular, the microscopic structure of the microgel in the presence of a cationic dye rhodamine 6G (R6G) was characterized in terms of its correlation length (ξ), which represents the length scale of the spatial correlation of the network density fluctuations, and characteristic distance (d*), which originated from the local packing of isopropyl groups of two neighboring chains. In the presence of cationic R6G, ξ exhibited a divergent-like behavior, which was not seen in the absence of R6G, and d* was decreased with decreasing the volume of the microgel upon increasing temperature. At the same time, the amount of R6G adsorbed per unit mass of the microgel increased upon heating. These results suggested that a coil-to-globule transition of the poly(N-isopropylacrylamide) chains in the present anionic microgel occurred because of efficiently screened, thus, short ranged electrostatic repulsion between the charged groups, and hydrophobic interaction between the isopropyl groups in the presence of cationic R6G. The combination of hydrophobic and electrostatic interaction between the cationic dye and the microgel affected the separation and volume transition behavior of the microgel. PMID:27101468

  1. Mechanism for oxidation of high-molecular-weight substrates by a fungal versatile peroxidase, MnP2.

    PubMed

    Tsukihara, Takahisa; Honda, Yoichi; Sakai, Ryota; Watanabe, Takahito; Watanabe, Takashi

    2008-05-01

    Unlike general peroxidases, Pleurotus ostreatus MnP2 was reported to have a unique property of direct oxidization of high-molecular-weight compounds, such as Poly R-478 and RNase A. To elucidate the mechanism for oxidation of polymeric substrates by MnP2, a series of mutant enzymes were produced by using a homologous gene expression system, and their reactivities were characterized. A mutant enzyme with an Ala substituting for an exposing Trp (W170A) drastically lost oxidation activity for veratryl alcohol (VA), Poly R-478, and RNase A, whereas the kinetic properties for Mn(2+) and H(2)O(2) were substantially unchanged. These results demonstrated that, in addition to VA, the high-molecular-weight substrates are directly oxidized by MnP2 at W170. Moreover, in the mutants Q266F and V166/168L, amino acid substitution(s) around W170 resulted in a decreased activity only for the high-molecular-weight substrates. These results, along with the three-dimensional modeling of the mutants, suggested that the mutations caused a steric hindrance to access of the polymeric substrates to W170. Another mutant, R263N, contained a newly generated N glycosylation site and showed a higher molecular mass in sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Interestingly, the R263N mutant exhibited an increased reactivity with VA and high-molecular-weight substrates. The existence of an additional carbohydrate modification and the catalytic properties in this mutant are discussed. This is the first study of a direct mechanism for oxidation of high-molecular-weight substrates by a fungal peroxidase using a homologous gene expression system.

  2. High molecular weight first generation PMR polyimides for 343 C applications

    NASA Technical Reports Server (NTRS)

    Malarik, Diane C.; Vannucci, Raymond D.

    1991-01-01

    The effect of molecular weight on 343 C thermo-oxidative stability (TOS), mechanical properties, and processability, of the first generation PMR polyimides was studied. Graphite fiber reinforced PMR-15, PMR-30, PMR-50, and PMR-75 composites (corresponding to formulated molecular weights of 1500, 3000, 5000, and 7500, respectively) were fabricated using a simulated autoclave process. The data reveals that while alternate autoclave cure schedules are required for the high molecular weight resins, low void laminates can be fabricated which have significantly improved TOS over PMR-15, with only a small sacrifice in mechanical properties.

  3. [Depolymerization of high-molecular-weight chitosan by the enzyme preparation Celloviridine G20x].

    PubMed

    Il'ina, A V; Tkacheva, Iu V; Varlamov, V P

    2002-01-01

    A low-molecular-weight water-soluble chitosan was obtained from high-molecular-weight crab chitosan using the enzyme preparation Celloviridine G20x. Optimum conditions for the enzymatic hydrolysis were designed. The reaction should be performed for 4 h in a sodium-acetate buffer (pH 5.2) at 55 degrees C and the enzyme to substrate ratio of 1:400. Fractional extraction of chitosan hydrolysate by aqueous ethanol (ethanol: distilled water) yielded fractions with molecular weights in the range 3.2-26.4 kDa.

  4. Effect of sterilization irradiation on friction and wear of ultrahigh-molecular-weight polyethylene

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Hady, W. F.; Crugnola, A.

    1979-01-01

    The effect of sterilization gamma irradiation on the friction and wear properties of ultrahigh molecular weight polyethylene (UHMWPE) sliding against 316L stainless steel in dry air at 23 C was determined. A pin-on-disk apparatus was used. Experimental conditions included a 1-kilogram load, a 0.061- to 0.27-meter-per-second sliding velocity, and a 32000- to 578000-meter sliding distance. Although sterilization doses of 2.5 and 5.0 megarads greatly altered the average molecular weight and the molecular weight distribution, the friction and wear properties of the polymer were not significantly changed.

  5. Solid State Structures of Alkali Metal Ion Complexes Formed by Low-Molecular-Weight Ligands of Biological Relevance.

    PubMed

    Aoki, Katsuyuki; Murayama, Kazutaka; Hu, Ning-Hai

    2016-01-01

    This chapter provides structural data, mainly metal binding sites/modes, observed in crystal structures of alkali metal ion complexes containing low-molecular-weight ligands of biological relevance, mostly obtained from the Cambridge Structural Database (the CSD version 5.35 updated to February 2014). These ligands include (i) amino acids and small peptides, (ii) nucleic acid constituents (excluding quadruplexes and other oligonucleotides), (iii) simple carbohydrates, and (iv) naturally occurring antibiotic ionophores. For some representative complexes of these ligands, some details on the environment of the metal coordination and structural characteristics are described. PMID:26860299

  6. On the use of hydroxyl radical kinetics to assess the number-average molecular weight of dissolved organic matter.

    PubMed

    Appiani, Elena; Page, Sarah E; McNeill, Kristopher

    2014-10-21

    Dissolved organic matter (DOM) is involved in numerous environmental processes, and its molecular size is important in many of these processes, such as DOM bioavailability, DOM sorptive capacity, and the formation of disinfection byproducts during water treatment. The size and size distribution of the molecules composing DOM remains an open question. In this contribution, an indirect method to assess the average size of DOM is described, which is based on the reaction of hydroxyl radical (HO(•)) quenching by DOM. HO(•) is often assumed to be relatively unselective, reacting with nearly all organic molecules with similar rate constants. Literature values for HO(•) reaction with organic molecules were surveyed to assess the unselectivity of DOM and to determine a representative quenching rate constant (k(rep) = 5.6 × 10(9) M(-1) s(-1)). This value was used to assess the average molecular weight of various humic and fulvic acid isolates as model DOM, using literature HO(•) quenching constants, kC,DOM. The results obtained by this method were compared with previous estimates of average molecular weight. The average molecular weight (Mn) values obtained with this approach are lower than the Mn measured by other techniques such as size exclusion chromatography (SEC), vapor pressure osmometry (VPO), and flow field fractionation (FFF). This suggests that DOM is an especially good quencher for HO(•), reacting at rates close to the diffusion-control limit. It was further observed that humic acids generally react faster than fulvic acids. The high reactivity of humic acids toward HO(•) is in line with the antioxidant properties of DOM. The benefit of this method is that it provides a firm upper bound on the average molecular weight of DOM, based on the kinetic limits of the HO(•) reaction. The results indicate low average molecular weight values, which is most consistent with the recent understanding of DOM. A possible DOM size distribution is discussed to

  7. EVALUATION OF DICLOFENAC SODIUM SUSTAINED RELEASE MATRIX PELLETS: IMPACT OF POLYETHYLENE GLYCOLS MOLECULAR WEIGHT.

    PubMed

    Ibrahim, Mohamed A; Shazly, Gamal A

    2015-01-01

    Sustained release matrix pellets loaded with 5% w/w diclofenac sodium (DS) were prepared using extrusion/spheronization technique. Different polyethylene glycols (PEGs) of different molecular weight, namely PEG 2000, PEG 4000 and PEG 6000 were mixed with avicel PH 101® in different weight ratios to manufacture the pellet formulations and water was used as a binder. Mix torque rheomter was used to characterize the pellets' wet mass. Also, the prepared pellets were characterized for their particle sizes, DS content, shape and morphology as well as the in vitro drug release. The results showed that increasing PEG weight ratio resulted in a reduction of wet mass torque as well as binder ratio, especially at PEG high weight ratios (30% and 50%) and the extent of lowering wet mass peak torque was inversely proportional to PEG molecular weight. The manufactured pellets exhibited size range of 993 to 1085 µm with small span values. The drug release from pellets was governed by the molecular weight of PEG used, since increasing PEG molecular weight resulted in slowing the drug release rate from pellets, but increasing its level resulted in enhancing release rate. This was attributed to increasing pellet wet mass peak torque by increasing PEG molecular weight and lowering it by increasing PEG level. The prepared pellets showed non-Fickian or anomalous drug release or the coupled diffusion/polymer relaxation.

  8. Evaluation of diclofenac sodium sustained release matrix pellets: impact of polyethylene glycols molecular weight.

    PubMed

    Ibrahim, A; Shazly, A

    2014-01-01

    Sustained release matrix pellets loaded with 5% w/w diclofenac sodium (DS) were prepared using extrusion/spheronization technique. Different polyethylene glycols (PEGs) of different molecular weight, namely PEG 2000, PEG 4000 and PEG 6000, were mixed with avicel PH 101 in different weight ratios to manufacture the pellet formulations and water was used as a binder. Mix torque rheometer was used to characterize the pellets' wet mass. Also, the prepared pellets were characterized for their particle sizes, DS content, shape and morphology as well as the in vitro drug release. The results showed increasing PEG weight ratio resulted in a reduction of wet mass torque as well as binder ratio, especially at PEG high weight ratios (30% and 50%) and the extent of lowering wet mass peak torque was inversely proportional to PEG molecular weight. The manufactured pellets exhibited size range of 993 μm to 1085 μm with small span values. The drug release from pellets was governed by the molecular weight of PEG used, since increasing PEG molecular weight resulted in slowing the drug release rate from pellets, but increasing its level resulted in enhancing release rate. This was attributed to increasing pellet wet mass peak torque by increasing PEG molecular weight and lowering it by increasing PEG level. The prepared pellets showed non-Fickian or anomalous drug release or the coupled diffusion/polymer relaxation.

  9. Swelling and polymer erosion for poly(ethylene oxide) tablets of different molecular weights polydispersities.

    PubMed

    Körner, Anna; Larsson, Anette; Andersson, Asa; Piculell, Lennart

    2010-03-01

    The aim of the study was to determine and compare the degree of swelling and the swelling kinetics of poly(ethylene oxide) (PEO) hydrophilic matrix tablets without any additives for matrixes with different molecular weight polydispersities. A wide range of "mixed" polydisperse PEO tablets were obtained by mixing two PEO batches with average molecular weights of 10(5) and 2 x 10(6), respectively. These were compared with "single-batch" tablets with narrower mono-modal molecular weight distributions. A texture analyzer (TA) was used to determine, during the entire dissolution process, the thickness of the "gel" layer, the height of the dry tablet core and the total height of the tablet. The release of polymer from the tablet was also measured using a chromatographic method. Both the swelling histories and the polymer release rates varied strongly with molecular weight and agitation rate, whereas the rate of dissolution of the solid core varied much less with molecular weight. For single-batch and mixed tablets, tuned to give the same release rate, the swelling process was found to be very similar, regardless of the molecular polydispersity (between 1.2 and 8.8). These results support a previously proposed dissolution model with the key assumption of a constant critical viscosity, independent of time or polymer molecular weight, at the surface of the gel layer of a dissolving tablet. PMID:19718760

  10. Effects of D-003, a mixture of high-molecular-weight sugar cane wax acids, on lipid peroxidation markers in older individuals: A randomized, double-blind, placebo-controlled study

    PubMed Central

    Pérez, Yohani; Menéndez, Roberto; Ferrer, José I.; Lopez, Ernesto; Castaño, Gladys; Fernández, Julio; Ferreiro, Rosa M.; Fernández, Lilia; Mendoza, Sarahí; González, Rosa; Mesa, Melbis

    2008-01-01

    Background: Aging is associated with increased lipid peroxidation (LP). D-003, a mixture of long-chain aliphatic primary acids purified from sugar cane wax, has been found to inhibit LP in experimental models and in healthy subjects. Objectives: The aim of this study was to assess the effects of D-003 on LP markers and the lipid profile of older individuals. Methods: This randomized, double-blind, placebo-controlled study was conducted at the Plaza Veterans' House, Havana City, Cuba. Male and female patients aged ≥60 years with total cholesterol values of <6.1 mmol/L were eligible for inclusion in the study. After a 3-week lead-in and baseline assessment period, patients were randomized to receive PO D-003 5 mg/d, D-003 10 mg/d, or placebo for 8 weeks. The effect on copper-induced LP of low-density lipoprotein (LDL) particles was the primary variable, and the effects on plasma total antioxidant status (TAS), plasma malondialdehyde (MDA) concentration, plasma antioxidant enzyme (superoxide dismutase and glutathione peroxidase) activities, and the lipid profile were secondary variables. A clinical examination was performed at each visit (baseline, weeks 4 and 8). A clinical examination, LP, and blood tests (lipid profile, hematologic, and blood biochemistry safety indicators) were performed at baseline and after 8 weeks of treatment. Compliance and adverse events (AEs) were assessed at weeks 4 and 8. A 2-tailed P < 0.05 was considered statistically significant for comparisons of both continuous and categoric variables. Results: Fifty-four patients aged ≥60 years were assessed for inclusion in the study, and 51 patients (40 women, 11 men; mean [SD] age, 67 [6] years) were included in the study. The lag phase of conjugated diene formation increased significantly and in a dose-dependent manner in the group treated with D-003 5 mg (24.7%; P < 0.01) and in the group treated with D-003 10 mg (29.3%; P < 0.01) compared with placebo. The maximal rate of conjugated diene

  11. Circulating high molecular weight IgG fibronectin complexes in myeloproliferative disorders.

    PubMed Central

    Baglin, T P; Price, S M; Boughton, B J

    1990-01-01

    The plasma of patients with myeloproliferative diseases was examined by polyethylene glycol (PEG) precipitation, analytical ultracentrifugation, and immunoaffinity chromatography for the presence of high molecular weight complexes of IgG and fibronectin. Abnormal circulating high molecular weight material was identified by ultracentrifugation in all patients. This was precipitated by PEG and was shown by exclusion chromatography to contain IgG in a high molecular weight form. Examination of plasma by immunoaffinity chromatography supported previous evidence for complex formation between IgG and fibronectin. These findings are further evidence that abnormal high molecular weight IgG complexes are a prominent feature of myeloproliferative disorders and implicate IgG fibronectin complex formation. PMID:2318985

  12. In vivo models of occupational asthma due to low molecular weight chemicals

    PubMed Central

    Hayes, J P; Taylor, A J Newman

    1995-01-01

    The aim was to review the development of in vivo models of asthma due to low molecular weight chemicals, in particular, those aspects that may be important to the understanding of occupational asthma in humans. PMID:7663640

  13. The chemical functionalized platinum nanodendrites: The effect of chemical molecular weight on electrocatalytic property

    NASA Astrophysics Data System (ADS)

    Xu, Guang-Rui; Han, Shu-He; Liu, Zong-Huai; Chen, Yu

    2016-02-01

    The surface chemical functionalization of noble metal nanocrystals is a promising strategy for improving the catalytic/electrocatalytic activity and selectivity of noble metal nanocrystals. In this work, we successfully synthesize the polyallylamine (PAA) with different molecular weight functionalized Pt nanodendrites (Pt-NDs) using a facile hydrothermal reduction method. The morphology and surface composition are investigated by transmission electron microscopy, element map, and thermogravimetric analysis. Furthermore, we detailedly investigate the effect of the molecular weight of PAA on the electrochemical property of the functionalized Pt-NDs. Electrochemical measurements show only low molecular weight PAA functionalized Pt-NDs allow electrolytes to access freely the Pt sites. Meanwhile, the low molecular weight PAA functionalized Pt-NDs show the excellent selectivity and activity for the oxygen reduction reaction in the presence of methanol.

  14. EPDM polymers with intermolecular asymmetrical molecular weight, crystallinity and diene distribution

    SciTech Connect

    Datta, S.; Cheremishinoff, N.P.; Kresge, E.N.

    1993-12-31

    Rapid extrusion of EPDM elastomers require low viscosity and thus low molecular weights for the polymer. Efficient vulcanization of these elastomers requires network perfection and thus high molecular weights for the polymer. The benefits of these apparently mutually exclusive goals is important in uses of EPDM elastomers which require extrusion of profiles which are later cured. This paper shows that by introducing simultaneously asymmetry in the distribution of molecular weights, crystallinity and vulcanizable sites these apparently contradictory goals can be resolved. While these polymers cannot be made from a single Ziegler polymerization catalyst, the authors show the synthesis of these model EPDM polymers by blending polymers with very different molecular weights, ethylene and ENB contents. These blends can be rapidly extruded without melt fracture and can be cured to vulcanizates which have excellent tensile properties.

  15. Fluorescence spectroscopy and molecular weight distribution of extracellular polymers from full-scale activated sludge biomass.

    PubMed

    Esparza-Soto, M; Westerhoff, P K

    2001-01-01

    Two fractions of extracellular polymer substances (EPSs), soluble and readily extractable (RE), were characterised in terms of their molecular weight distributions (MWD) and 3-D excitation-emission-matrix (EEM) fluorescence spectroscopy signatures. The EPS fractions were different: the soluble EPSs were composed mainly of high molecular weight compounds, while the RE EPSs were composed of small molecular weight compounds. Contrary to previous thought, EPS may not be considered only as macromolecular because most organic matter present in both fractions had low molecular weight. Three different fluorophore peaks were identified in the EEM fluorescence spectra. Two peaks were attributed to protein-like fluorophores, and the third to a humic-like fluorophore. Fluorescence signatures were different from other previously published signatures for marine and riverine environments. EEM spectroscopy proved to be a suitable method that may be used to characterise and trace organic matter of bacterial origin in wastewater treatment operations.

  16. Antioxidant activity of low molecular weight alginate produced by thermal treatment.

    PubMed

    Kelishomi, Zahra Habibi; Goliaei, Bahram; Mahdavi, Hossein; Nikoofar, Alireza; Rahimi, Mahmood; Moosavi-Movahedi, Ali Akbar; Mamashli, Fatemeh; Bigdeli, Bahareh

    2016-04-01

    By definition, antioxidants are molecules that inhibit the oxidation of other molecules. Therefore, such compounds have very important clinical roles. In this study alginate polymer was depolymerized by heat treatment. The resulting low molecular weight alginates were investigated by UV-visible spectroscopy, Viscometry, Dynamic light scattering and FT-IR spectroscopy techniques. Antioxidant properties of these heat products were studied by ABTS and superoxide radical scavenging assays. Results showed that heating caused breaks in the polymer chain and so generation of low molecular weight alginates. Antioxidant measurements confirmed antioxidant activity of alginate increased upon a decrease in molecular weight. Therefore, low molecular weight alginate produced by heating could be considered as a stronger antioxidant than alginate polymer. These products could be useful for industrial and biomedical applications.

  17. Bacillus subtilis 168 levansucrase (SacB) activity affects average levan molecular weight.

    PubMed

    Porras-Domínguez, Jaime R; Ávila-Fernández, Ángela; Miranda-Molina, Afonso; Rodríguez-Alegría, María Elena; Munguía, Agustín López

    2015-11-01

    Levan is a fructan polymer that offers a variety of applications in the chemical, health, cosmetic and food industries. Most of the levan applications depend on levan molecular weight, which in turn depends on the source of the synthesizing enzyme and/or on reaction conditions. Here we demonstrate that in the particular case of levansucrase from Bacillus subtilis 168, enzyme concentration is also a factor defining the molecular weight levan distribution. While a bimodal distribution has been reported at the usual enzyme concentrations (1 U/ml equivalent to 0.1 μM levansucrase) we found that a low molecular weight normal distribution is solely obtained al high enzyme concentrations (>5 U/ml equivalent to 0.5 μM levansucrase) while a high normal molecular weight distribution is synthesized at low enzyme doses (0.1 U/ml equivalent to 0.01 μM of levansucrase).

  18. Presence of polyphosphate of low molecular weight in zygomycetes.

    PubMed Central

    Dietrich, S M

    1976-01-01

    Polyphosphate of average chain length corresponding to 10 phosphate units was detected in the mycelial extract of zygomycetes. Gel electrophoresis techniques commonly used for the separation and characterization of acidic mucopolysaccharides were successfully used for the detection, purification, and characterization of the polyphosphate. Images PMID:986390

  19. Mild cracking of high-molecular-weight hydrocarbons

    SciTech Connect

    Biouri, B.; Hamdan, F.; Herault, D.

    1985-01-01

    Controlled cracking in the liquid phase of n-hexadecane, 6-methyleicosane, 1-phenyldodecane, and C21-C27 paraffins was studied in a stainless steel microreactor between 350 and 440 C for residence times varyin from 0.5 to 4 h at nitrogen or hydrogen pressures of 20 bar. Cracking occurred according to a molecular mechanism, but its kinetic data such as the order of reaction and the activation energy were similar to those of radical type cracking. The rate of formation of cracked gases was extremely small and the experimental and simulated compositions of the cracked liquids, based on a molecular type scission, agreed very well. This type of cracking is very interesting for visbreaking of heavy oils.

  20. Synthesis and polymerization of bicyclic ketals: a practical route to high-molecular weight polyketals.

    PubMed

    Whiting, Bryan T; Coates, Geoffrey W

    2013-07-31

    Polyketals are an important class of materials for drug delivery to sensitive tissues as they degrade in vivo to nonacidic species. We report the synthesis of high-molecular weight cyclic polyketals by the cationic ring-opening polymerization of bicyclic ketal monomers, which were prepared by the metal-catalyzed rearrangement of epoxy ketones. Three different cyclic polyketals with high molecular weights were synthesized using this protocol.

  1. Comparative gene transfer efficiency of low molecular weight polylysine DNA-condensing peptides.

    PubMed

    McKenzie, D L; Collard, W T; Rice, K G

    1999-10-01

    In a previous report (M.S. Wadhwa et al. (1997) Bioconjugate Chem. 8, 81-88), we synthesized a panel of polylysine-containing peptides and determined that a minimal repeating lysine chain of 18 residues followed by a tryptophan and an alkylated cysteine residue (AlkCWK18) resulted in the formation of optimal size (78 nm diameter) plasmid DNA condensates that mediated efficient in vitro gene transfer. Shorter polylysine chains produced larger DNA condensates and mediated much lower gene expression while longer lysine chains were equivalent to AlkCWK18. Surprisingly, AlkCWK18 (molecular weight 2672) was a much better gene transfer agent than commercially available low molecular weight polylysine (molecular weight 1000-4000), despite its similar molecular weight. Possible explanations were that the cysteine or tryptophan residue in AlkCWK18 contributed to the DNA binding and the formation of small condensates or that the homogeneity of AlkCWK18 relative to low molecular weight polylysine facilitated optimal condensation. To test these hypotheses, the present study prepared AlkCYK18 and K20 and used these to form DNA condensates and conduct in vitro gene transfer. The results established that DNA condensates prepared with either AlkCYK18 or K20 possessed identical particle size and mediated in vitro gene transfer efficiencies that were indistinguishable from AlkCWK18 DNA condensates, eliminating the possibility of contributions from cysteine or tryptophan. However, a detailed chromatographic and electrospray mass spectrometry analysis of low molecular weight polylysine revealed it to possess a much lower than anticipated average chain length of dp 6. Thus, the short chain length of low molecular weight polylysine explains its inability to form small DNA condensates and mediate efficient gene transfer relative to AlkCWK18 DNA condensates. These experiments further emphasize the need to develop homogenous low molecular weight carrier molecules for nonviral gene delivery.

  2. Production of soluble, high molecular weight phosphorus and its subsequent uptake by stream detritus

    SciTech Connect

    Mulholland, P.J.; Minear, R.A.; Elwood, J.W.

    1987-02-08

    Several studies have demonstrated the importance of nonorthophosphate compounds, including some of relatively high molecular weight, in phosphorus cycling in aquatic ecosystems. This paper reports results from a laboratory study indicating that some of the soluble phosphorus released by microbes associated with coarse and fine detritus in streams is of relatively high molecular weight (>5000 daltons) and that this phosphorus is subsequently utilized, but at rates considerably lower than for orthophosphate.

  3. Intrinsic viscoelasticity in thin high-molecular-weight polymer films.

    PubMed

    Sheng, Xiaoyuan; Wintzenrieth, Frédéric; Thomas, Katherine R; Steiner, Ullrich

    2014-06-01

    The rheology of 44-75-nm-thick polystyrene films were probed by destabilization in an electric field. The non-cross-linked films showed the hallmark of viscoelasiticy; they exhibited elastic behavior at high shear rates and viscous rheology at low shear rates for stationary applied fields. These results are interpreted in terms of surface adhesion of chain segments in contact with the substrate surface, which substantially reduces reptative molecular motion of nearly all chains within the film.

  4. Control of molecular weight of polystyrene using the reverse iodine transfer polymerization (RITP)-emulsion technique.

    PubMed

    Oh, Hyeong Geun; Shin, Hongcheol; Jung, Hyejun; Lee, Byung Hyung; Choe, Soonja

    2011-01-15

    The RITP-emulsion polymerization of styrene in the presence of molecular iodine has been successfully performed using potassium persulfate (KPS) as an initiator and 1-hexadecanesulfonate as an emulsifier under argon atmosphere at 80°C for 7 hrs in the absence of light. The effects of the iodine concentration, molar ratio between KPS and iodine, and solid contents on the molecular weight of polystyrene (PS) were studied. As the iodine concentration increased from 0.05 to 0.504 mmol under the fixed [KPS]/[I(2)] ratio at 4.5, the weight-average molecular weight of PS substantially decreased from 126,120 to 35,690 g/mol, the conversion increased from 85.0% to 95.2%, and the weight-average particle diameter decreased from 159 to 103 nm. In addition, as the ratio of [KPS]/[I(2)] increased from 0.5 to 6.0 at the fixed [I(2)] of 0.504 mmol, the weight-average molecular weight of PS decreased from 72,170 to 30,640 g/mol with high conversion between 81.7% and 96.5%. Moreover, when the styrene solid content increased from 10 to 40 wt.% at the fixed [KPS]/[I(2)] ratio of 4.5, the weight-average molecular weight of PS varied between 33,500 and 37,200 g/mol, the conversion varied between 94.9% and 89.7% and the weight-average diameter varied from 122 to 205 nm. Thus, the control of molecular weight of PS less than 100,000g/mol with high conversion (95%) and particle stability of up to 40 wt.% solid content were easily achieved through the usage of iodine with suitable ratio of [KPS]/[I(2)] in the RITP-emulsion polymerization technique, which is of great industrial importance.

  5. Enzymatic modification of pectin to increase its calcium sensitivity while preserving its molecular weight.

    PubMed

    Hotchkiss, Arland T; Savary, Brett J; Cameron, Randall G; Chau, Hoa K; Brouillette, Janine; Luzio, Gary A; Fishman, Marshall L

    2002-05-01

    A commercial high-methoxy citrus pectin was treated with a purified salt-independent pectin methylesterase (PME) isozyme isolated from Valencia orange peel to prepare a series of deesterified pectins. A series of alkali-deesterified pectins was also prepared at pH 10 under conditions permitting beta-elimination. Analysis of these pectins using high-performance size exclusion chromatography (HPSEC) with on-line multiangle laser light-scattering, differential viscometer, and refractive index (RI) detectors revealed no reduction in weight-average molecular weight (M(w); 150000) in the PME-treated pectin series, whereas a 16% reduction in intrinsic viscosity (IV) occurred below a degree of esterification (DE) of 47%. In contrast, alkali deesterification rapidly reduced both M(w) and IV to less than half of that observed for untreated pectin. PME treatment of a non-calcium-sensitive citrus pectin introduced calcium sensitivity with only a 6% reduction in the DE. Triad blocks of unesterified galacturonic acid were observed in (1)H nuclear magnetic resonance spectra of this calcium-sensitive pectin (CSP). These results demonstrate that the orange salt-independent PME isozyme utilizes a blockwise mode of action. This is the first report of the preparation of a CSP by PME treatment without significant loss of the pectin's M(w) due to depolymerization.

  6. Discharge Characteristics of Low Molecular Weight Solid Polymer Electrolyte

    NASA Astrophysics Data System (ADS)

    Kumar, P. Naveen; Sasikala, U.; Sekhar, P. Chandra; Achari, V. B. S.; Rao, V. V. R. N.; Sharma, A. K.

    2011-07-01

    Solid polymer electrolytes based on polyethylene glycol (PEG) complexed with sodium chloride (NaCl) at different weight percent ratios were prepared using solution cast technique. Measurement of DC conductivity in the temperature range 303-373 K shows that the conductivity increases with increase in concentration of salt and with increase in temperature. Transference number measurent has been employed to investigate the charge transport in the polymer electrolyte system. This data has shown that the charge transport in the polymer electrolyte system is predominantly due to ions. Using this polymer electrolyte, solid state electrochemical cells have been fabricated. Various cell parameters associated with these cells were evaluated and reported.

  7. Effect of matrix molecular weight on the coarsening mechanism of polymer-grafted gold nanocrystals.

    PubMed

    Jia, Xiaolong; Listak, Jessica; Witherspoon, Velencia; Kalu, E Eric; Yang, Xiaoping; Bockstaller, Michael R

    2010-07-20

    A systematic evaluation of the effect of polymer matrix molecular weight on the coarsening kinetics of uniformly dispersed polystyrene-grafted gold nanoparticles is presented. Particle coarsening is found to proceed via three stages (i.e., atomic-diffusion-based Ostwald ripening (OR), particle-migration-based collision-coalescence, and the subsequent reshaping of particle assemblies). The relative significance of each stage and hence the evolution of particle size and shape have been found to depend sensitively upon time, temperature, and the molecular weight of the host polymer. At temperatures close to the matrix glass-transition temperature, Ostwald ripening has been observed to be dominant on all experimental timescales. With increasing annealing temperature, collision coalescence becomes the dominant mode of coarsening, leading to rapid particle growth. The onset of the latter process is found to be increasingly delayed with increasing molecular weight of the polymer host. Particle coalescence is observed to proceed via two fundamental modes (i.e., diffusion-limited aggregation and growth resulting in the formation of fractal particle clusters and the subsequent recrystallization into more spherical monolithic aggregate structures). Interestingly, particle coarsening in high-molecular-weight matrix polymers is found to proceed significantly faster than predicted on the basis of the bulk polymer viscosity; this acceleration is interpreted to be a consequence of the network characteristics of high-molecular-weight polymers by analogy to the phenomenon of nanoviscosity that has been reported in the context of nanoparticle diffusion within high-molecular-weight polymers. PMID:20575544

  8. Western blotting of high and low molecular weight proteins using heat.

    PubMed

    Kurien, Biji T; Scofield, R Hal

    2015-01-01

    A method for the electrophoretic transfer of high and low molecular weight proteins to nitrocellulose membranes following sodium dodecyl sulfate (SDS) polyacrylamide gel is described here. The transfer was performed with heated (70-75 °C) normal transfer buffer from which methanol had been omitted. Complete transfer of high and low molecular weight antigens (molecular weight protein standards, a purified protein, and proteins from a human tissue extract) could be carried out in 10 min for a 7 % (0.75 mm) SDS polyacrylamide gel. For 10 and 12.5 % gels (0.75 mm) the corresponding time was 15 min. A complete transfer could be carried out in 20 min for 7, 10, and 12.5 % gels (1.5 mm gels). The permeability of the gel is increased by heat, such that the proteins trapped in the polyacrylamide gel matrix can be easily transferred to the membrane. The heat mediated transfer method was compared with a conventional transfer protocol, under similar conditions. The conventional method transferred minimal low molecular weight proteins while retaining most of the high molecular weight proteins in the gel. In summary, this procedure is particularly useful for the transfer of high molecular weight proteins, very rapid, and avoids the use of methanol.

  9. Ultrarapid electrophoretic transfer of high and low molecular weight proteins using heat.

    PubMed

    Kurien, Biji T; Scofield, R Hal

    2009-01-01

    An ultrarapid method for the electrophoretic transfer of high and low molecular weight proteins to nitrocellulose membranes following sodium dodecyl sulfate (SDS) polyacrylamide gel is described here. The transfer was performed with heated (70-75 degrees C) normal transfer buffer from which methanol had been omitted. Complete transfer of high and low molecular weight antigens (molecular weight protein standards, a purified protein, and proteins from a human tissue extract) could be carried out in 10 min for a 7% (0.75 mm) SDS polyacrylamide gel. For 10 and 12.5% gels (0.75 mm) the corresponding time was 15 min. A complete transfer could be carried out in 20 min for 7, 10, and 12.5% gels (1.5 mm gels). The permeability of the gel is increased by heat, such that the proteins trapped in the polyacrylamide gel matrix can be easily transferred to the membrane. The heat mediated transfer method was compared with a conventional transfer protocol, under similar conditions. The conventional method transferred minimal low molecular weight proteins while retaining most of the high molecular weight proteins in the gel. In summary, this procedure is particularly useful for the transfer of high molecular weight proteins, very rapid, and avoids the use of methanol.

  10. [Molecular weight analysis of physiological proteinuria in newborn infants (author's transl)].

    PubMed

    Thanner, F; Wartha, R; Gekle, D

    1979-03-15

    The physiological protien and glycoprotein excretions in the urine samples of a larger group of newborn infants were separated according to the molecular weights by SDS polyacrylamide gel electrophoresis and compared with the protein excretions of older children. We found higher proportions of albumin, of high molecular weight (MW = molecular weight greater than or equal to 150 000 dt) and of lower molecular weight (MW less than albumin 6800 dt) proteins in the first 24-h urine samples after birth. One week after birth the low molecular weight proteins predominated because there was a substantial decrease in the excretion of albumin and of high molecular weight proteins (MW greater than or equal to 150 000 dt). We compared the patterns of protein excretion of the newborn infants with those of children aged from 2 1/2 to 15 years. These urines samples showed a typical pattern of protein excretion not correlated to the age. These findings express a transitory immaturity of the glomerular filter and of the tubular protein reabsorbing system of the newborn kidney. Apparently, the tubular protein handling normalizes later than the glomerular filtration of proteins.

  11. Molecular weight dependent vertical composition profiles of PCDTBT:PC71BM blends for organic photovoltaics

    PubMed Central

    Kingsley, James W.; Marchisio, Pier Paolo; Yi, Hunan; Iraqi, Ahmed; Kinane, Christy J.; Langridge, Sean; Thompson, Richard L.; Cadby, Ashley J.; Pearson, Andrew J.; Lidzey, David G.; Jones, Richard A. L.; Parnell, Andrew J.

    2014-01-01

    We have used Soxhlet solvent purification to fractionate a broad molecular weight distribution of the polycarbazole polymer PCDTBT into three lower polydispersity molecular weight fractions. Organic photovoltaic devices were made using a blend of the fullerene acceptor PC71BM with the molecular weight fractions. An average power conversion efficiency of 5.89% (peak efficiency of 6.15%) was measured for PCDTBT blend devices with a number average molecular weight of Mn = 25.5 kDa. There was significant variation between the molecular weight fractions with low (Mn = 15.0 kDa) and high (Mn = 34.9 kDa) fractions producing devices with average efficiencies of 5.02% and 3.70% respectively. Neutron reflectivity measurements on these polymer:PC71BM blend layers showed that larger molecular weights leads to an increase in the polymer enrichment layer thickness at the anode interface, this improves efficiency up to a limiting point where the polymer solubility causes a reduction of the PCDTBT concentration in the active layer. PMID:24924096

  12. Occurrence of a multimeric high-molecular-weight glyceraldehyde-3-phosphate dehydrogenase in human serum.

    PubMed

    Kunjithapatham, Rani; Geschwind, Jean-Francois; Devine, Lauren; Boronina, Tatiana N; O'Meally, Robert N; Cole, Robert N; Torbenson, Michael S; Ganapathy-Kanniappan, Shanmugasundaram

    2015-04-01

    Cellular glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a phylogenetically conserved, ubiquitous enzyme that plays an indispensable role in energy metabolism. Although a wealth of information is available on cellular GAPDH, there is a clear paucity of data on its extracellular counterpart (i.e., the secreted or extracellular GAPDH). Here, we show that the extracellular GAPDH in human serum is a multimeric, high-molecular-weight, yet glycolytically active enzyme. The high-molecular-weight multimers of serum GAPDH were identified by immunodetection on one- and two-dimensional gel electrophoresis using multiple antibodies specific for various epitopes of GAPDH. Partial purification of serum GAPDH by DEAE Affigel affinity/ion exchange chromatography further established the multimeric composition of serum GAPDH. In vitro data demonstrated that human cell lines secrete a multimeric, high-molecular-weight enzyme similar to that of serum GAPDH. Furthermore, LC-MS/MS analysis of extracellular GAPDH from human cell lines confirmed the presence of unique peptides of GAPDH in the high-molecular-weight subunits. Furthermore, data from pulse-chase experiments established the presence of high-molecular-weight subunits in the secreted, extracellular GAPDH. Taken together, our findings demonstrate the presence of a high-molecular-weight, enzymatically active secretory GAPDH in human serum that may have a hitherto unknown function in humans.

  13. High Molecular Weight Dimer Esters in α-Pinene Secondary Organic Aerosol

    NASA Astrophysics Data System (ADS)

    Kristensen, Kasper; Cui, Tianqu; Zhang, Haofei; Gold, Avram; Glasius, Marianne; Surratt, Jason D.

    2014-05-01

    Monoterpenes, such as α-pinene, constitute an important group of biogenic volatile organic compounds (BVOC). Once emitted into the atmosphere α-pinene is removed by oxidization by the hydroxyl radical (OH), reactions with ozone (O3), and with nitrate radicals (NO3) resulting in the formation of first-generation oxidation products, such as semi-volatile carboxylic acids. In addition, higher molecular weight dimer esters originating from the oxidation of α-pinene have been observed in both laboratory-generated and ambient secondary organic aerosols (SOA). While recent studies suggest that the dimers are formed through esterification between carboxylic acids in the particle phase, the formation mechanism of the dimer esters is still ambiguous. In this work, we present the results of a series of smog chamber experiments to assess the formation of dimer esters formed from the oxidation of α-pinene. Experiments were conducted in the University of North Carolina (UNC) dual outdoor smog chamber facility to investigate the effect of oxidant species (OH versus O3), relative humidity (RH), and seed aerosol acidity in order to obtain a better understanding of the conditions leading to the formation of the dimer esters and how these parameters may affect the formation and chemical composition of SOA. The chemical composition of α-pinene SOA was investigated by ultra-performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS), and a total of eight carboxylic acids and four dimer esters were identified, constituting between 8 and 12 % of the total α-pinene SOA mass.

  14. 21 CFR 177.1440 - 4,4′-Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... resins minimum molecular weight 10,000. 177.1440 Section 177.1440 Food and Drugs FOOD AND DRUG...′-Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000. 4,4′-Isopropylidenediphenol-epichlo-rohydrin resins having a minimum molecular weight of 10,000 may be safely used as articles or components...

  15. 21 CFR 177.1440 - 4,4′-Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... resins minimum molecular weight 10,000. 177.1440 Section 177.1440 Food and Drugs FOOD AND DRUG... Contact Surfaces § 177.1440 4,4′-Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000. 4,4′-Isopropylidenediphenol-epichlo-rohydrin resins having a minimum molecular weight of...

  16. 21 CFR 177.1440 - 4,4′-Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... resins minimum molecular weight 10,000. 177.1440 Section 177.1440 Food and Drugs FOOD AND DRUG... Contact Surfaces § 177.1440 4,4′-Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000. 4,4′-Isopropylidenediphenol-epichlo-rohydrin resins having a minimum molecular weight of...

  17. Comparison of the evolution of low molecular weight phenolic compounds in typical Sherry wines: Fino, Amontillado, and Oloroso.

    PubMed

    García Moreno, M Valme; Barroso, Carmelo García

    2002-12-18

    Changes in the content of low molecular weight phenolic compounds (hydroxybenzoic and hydroxycinnamic acids, aldehydes, and their esterified derivatives, tyrosol and 5-(hydroxymethyl)-2-furaldehyde) during the aging of three different classes of Sherry wine, Fino, Oloroso, and Amontillado, have been studied. The samples studied were taken from each of the scales of the particular aging system applied to the three classes of wine. Clear differences were observed in the behavior of the low molecular weight phenolic in the three classes of wine. The wines subjected to oxidative aging presented a higher phenolic content overall, with the exception of the esterified derivatives of phenolic compounds that are mainly found in the samples that have not undergone any process of oxidation. MANOVA results confirmed that there are significant differences between all of the samples of the three types of wines. Using LDA, a classification of 100% of the samples has been made. PMID:12475270

  18. Function of Succinoglycan Polysaccharide in Sinorhizobium meliloti Host Plant Invasion Depends on Succinylation, Not Molecular Weight

    PubMed Central

    Mendis, Hajeewaka C.; Madzima, Thelma F.; Queiroux, Clothilde

    2016-01-01

    ABSTRACT The acidic polysaccharide succinoglycan produced by the rhizobial symbiont Sinorhizobium meliloti 1021 is required for this bacterium to invade the host plant Medicago truncatula and establish a nitrogen-fixing symbiosis. S. meliloti mutants that cannot make succinoglycan cannot initiate invasion structures called infection threads in plant root hairs. S. meliloti exoH mutants that cannot succinylate succinoglycan are also unable to form infection threads, despite the fact that they make large quantities of succinoglycan. Succinoglycan produced by exoH mutants is refractory to cleavage by the glycanases encoded by exoK and exsH, and thus succinoglycan produced by exoH mutants is made only in the high-molecular-weight (HMW) form. One interpretation of the symbiotic defect of exoH mutants is that the low-molecular-weight (LMW) form of succinoglycan is required for infection thread formation. However, our data demonstrate that production of the HMW form of succinoglycan by S. meliloti 1021 is sufficient for invasion of the host M. truncatula and that the LMW form is not required. Here, we show that S. meliloti strains deficient in the exoK- and exsH-encoded glycanases invade M. truncatula and form a productive symbiosis, although they do this with somewhat less efficiency than the wild type. We have also characterized the polysaccharides produced by these double glycanase mutants and determined that they consist of only HMW succinoglycan and no detectable LMW succinoglycan. This demonstrates that LMW succinoglycan is not required for host invasion. These results suggest succinoglycan function is not dependent upon the presence of a small, readily diffusible form. PMID:27329751

  19. Regulation of high molecular weight bovine brain neutral protease by phospholipids in vitro.

    PubMed

    Chauhan, V; Sheikh, A M; Chauhan, A; Spivack, W D; Fenko, M D; Malik, M N

    2005-04-01

    The activity of the heat stable, glycosylated high molecular weight bovine brain neutral protease (HMW protease) is differentially regulated by phospholipids. While phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidic acid (PA) had only marginal stimulatory effect (40-75%) on the activity of HMW protease, lysophoshatidylcholine (lysoPC) and lysophosphatidic acid (lysoPA) activated the enzyme by more than two-fold. Both lysoPC and lysoPA exhibited concentration-dependent saturation kinetics for the activation of HMW protease. Surprisingly, phosphoinositides (phosphatidylinositol, PI; phosphatidylinositol 4-phosphate, PIP; and phosphatidylinositol 4,5-bisphosphate, PIP2) modulated the activity of protease differently: activation of the enzyme was higher with PIP (90%) as compared to PI (21%), whereas PIP2 inhibited the enzyme (16%). The inhibition of the protease by PIP2 was concentration-dependent. During receptor-coupled cell activation, phospholipase A2 (PLA2) converts PC and PA to lysoPC and lysoPA, respectively; PI is converted to PIP2 by successive enzymatic phosphorylation by PI 4-kinase and PIP 5-kinase; and phospholipase C (PLC) degrades PIP2 to diacylglycerol and inositol 1,4,5-trisphosphate. Therefore, the data suggest that HMW protease may be coupled to cell signal transduction where PLA2, PI 4-kinase, PIP 5-kinase and PLC are involved. PMID:16010981

  20. Relationship between Extracellular Low-Molecular-Weight Thiols and Mercury Species in Natural Lake Periphytic Biofilms.

    PubMed

    Leclerc, Maxime; Planas, Dolors; Amyot, Marc

    2015-07-01

    The uptake of mercury by microorganisms is a key step in the production of methylmercury, a biomagnifiable toxin. Mercury complexation by low-molecular-weight (LMW) thiols can affect its bioavailability and thus the production of methylmercury. Freshwater biofilms were sampled in the summer using artificial Teflon substrates submerged for over a year to allow natural community colonization in the littoral zone of a Boreal Shield lake. Inside biofilms, concentrations of different extracellular thiol species (thioglycolic acid, l-cysteine-l-glycine, cysteine, and glutathione) were up to 3 orders of magnitude greater than in the surrounding water column, potentially more readily controlling mercury speciation than in the water column. All biofilm thiols except thioglycolic acid were highly correlated to chlorophyll a, likely indicating an algal origin. Extracellular total mercury represented 3 ± 1% of all biofilm mercury and was preferentially found in the capsular fraction. Levels of LMW thiols of presumed algal origins were highly correlated with total mercury in the mobile colloidal fraction of biofilms. We propose that periphytic phototrophic microorganisms such as algae likely affect the bioavailability of mercury through the exudation of LMW thiols, and thus they may play a key role in the production of methylmercury in biofilms. PMID:26011687

  1. Partial characterization of a low molecular weight human collagen that undergoes alternative splicing

    SciTech Connect

    Pihlajaniemi, T.; Myllylea, R.; Kurkinen, M.; Prockop, D.J.

    1987-02-01

    A cDNA library prepared from RNA isolated from a cultured human tumor cell line, HT-1080, was screened with a mouse cDNA clone coding for part of the -Gly-Xaa-Yaa-domain of the ..cap alpha..2(IV) collagen chain. Four overlapping cDNA clones were characterized that coded for a low molecular weight human collagen. The cDNA clones did not, however, code for the short-chain collagens, types IX and X. The amino acid sequences derived from the clones resembled type IV collagen in that there were short interruptions in the repeating -Gly-Xaa-Yaa-sequence. The noncollagenous, carboxyl-terminal domain was, however, much shorter and contained only 18 amino acid residues. Interestingly, one of the cDNA clones contained an additional 36 nucleotides not found in an overlapping clone. The 36 nucleotides encoded four -Gly-Xaa-Yaa-repeats without changing the reading frame. Nuclease S1 mapping using a /sup 32/P-labelled probe demonstrated that the different between the clones was due to existence of two different mRNAs. A synthetic 24-residue peptide corresponding to the last two -Gly-Xaa-Yaa-triplets and the entire carboxyl-terminal domain was used to generate polyclonal antibodies. Electrophoretic transfer blot analysis of HT-1080 cells and normal human skin fibroblasts identified two polypeptides, M/sub r/ 67,000 and M/sub r/ 62,000, that were sensitive to bacterial collagenase.

  2. Relationship between Extracellular Low-Molecular-Weight Thiols and Mercury Species in Natural Lake Periphytic Biofilms.

    PubMed

    Leclerc, Maxime; Planas, Dolors; Amyot, Marc

    2015-07-01

    The uptake of mercury by microorganisms is a key step in the production of methylmercury, a biomagnifiable toxin. Mercury complexation by low-molecular-weight (LMW) thiols can affect its bioavailability and thus the production of methylmercury. Freshwater biofilms were sampled in the summer using artificial Teflon substrates submerged for over a year to allow natural community colonization in the littoral zone of a Boreal Shield lake. Inside biofilms, concentrations of different extracellular thiol species (thioglycolic acid, l-cysteine-l-glycine, cysteine, and glutathione) were up to 3 orders of magnitude greater than in the surrounding water column, potentially more readily controlling mercury speciation than in the water column. All biofilm thiols except thioglycolic acid were highly correlated to chlorophyll a, likely indicating an algal origin. Extracellular total mercury represented 3 ± 1% of all biofilm mercury and was preferentially found in the capsular fraction. Levels of LMW thiols of presumed algal origins were highly correlated with total mercury in the mobile colloidal fraction of biofilms. We propose that periphytic phototrophic microorganisms such as algae likely affect the bioavailability of mercury through the exudation of LMW thiols, and thus they may play a key role in the production of methylmercury in biofilms.

  3. Use of Kinematic Viscosity Data for the Evaluation of the Molecular Weight of Petroleum Oils

    ERIC Educational Resources Information Center

    Maroto, J. A.; Quesada-Perez, M.; Ortiz-Hernandez, A. J.

    2010-01-01

    A new laboratory procedure for the evaluation of the mean molecular weight (mean relative molecular mass) of petroleum oils with high accuracy is described. The density and dynamic viscosity of three commercial petroleum oils are measured at different temperatures. These experimental data are used to calculate the kinematic viscosity as a function…

  4. Purification and characteristics of a low-molecular-weight peptide possessing oxidative capacity for phenol from Phanerochaete chrysosporium.

    PubMed

    Hu, Ming; Zhang, Weican; Lu, Xuemei; Gao, Peiji

    2006-06-01

    A new low-molecular-weight peptide with phenol oxidase activity, named Pc factor, was isolated and purified from liquid culture of a white-rot basidiomycete Phanerochaete chrysosporium. Its molecular weight was about 600 Da estimated by gel-filtration. Three amino acids Glu, Gly and Val were detected in hydrolysate. Absorption peaks corresponding to amino acids and peptide were observed by UV and IR spectra analysis. And the signal of Ca of amino acid was also detected by 13C-NMR method. Pc factor had high thermostability and remained active in weakly alkalescent pH range. It could chelate Fe3+ and reduce it to Fe2+, but no hydroxyl radical HO* could be detected during the reaction process. It could oxidize phenolic lignin-model compounds such as 2,6-dimethoxyphenol (2,6-DMP), 2,2'-azinobis (3-ethylbenzathiazoline-6-sulfinic acid) (ABTS) and syringaldazine in the absence of Mn2+ and H2O2. These characteristics differed greatly from those of manganese peroxidases. The oxidative catalysis of Pc factor can be enhanced by certain metal ions such as Cu2+ and Mn2+ etc., and O2 molecule was necessary for this reaction. In summary, Pc factor may function as an electron carrier in this novel oxidation-reduction system. PMID:16856493

  5. Rheological and microstructural investigation of oat β-glucan isolates varying in molecular weight.

    PubMed

    Agbenorhevi, Jacob K; Kontogiorgos, Vassilis; Kirby, Andrew R; Morris, Victor J; Tosh, Susan M

    2011-10-01

    The rheological properties and microstructure of aqueous oat β-glucan solutions varying in molecular weight were investigated. The structural features and molecular weights (MW) were characterized by (13)C NMR spectroscopy and high performance size-exclusion chromatography (HPSEC), respectively. The microstructure of the β-glucans dispersions was also examined by atomic force microscopy (AFM). The samples with β-glucan content between 78 and 86% on a dry weight basis had MW, intrinsic viscosity ([η]) and critical concentration (c*) in the range of 142-2800×10(3)g/mol, 1.7-7.2dl/g and 0.25-1.10g/dl, respectively. The flow and viscoelastic behaviour was highly dependent on MW and on the concentration of the β-glucans dispersions. Pseudoplastic behaviour was exhibited at high concentrations and Newtonian behaviour was evident at low concentrations. At the same concentration, the viscosity was higher for higher MW samples. The Cox-Merz rule was applicable for the lower molecular weight samples at higher concentrations whereas the high molecular weight sample deviated at concentrations greater than 1.0%, w/v. The mechanical spectra with variation of both MW and concentration were typical of entangled biopolymer solutions. AFM images revealed the formation of clusters or aggregates linked via individual polymer chains scattered heterogeneously throughout the system. The aggregate size increased with the molecular weight of the samples investigated and has been linked to the rheological behaviour of the samples.

  6. From oligomers to molecular giants of soybean oil in supercritical carbon dioxide medium: 1. Preparation of polymers with lower molecular weight from soybean oil.

    PubMed

    Liu, Zengshe; Sharma, Brajendra K; Erhan, Sevim Z

    2007-01-01

    Polymers with a low molecular weight derived from soybean oil have been prepared in a supercritical carbon dioxide medium by cationic polymerization. Boron trifluoride diethyl etherate was used as an initiator. Influences of polymerization temperature, amount of initiator, and carbon dioxide pressure on the molecular weight were investigated. It is shown that the higher polymerization temperature favors polymers with relatively higher molecular weights. Larger amounts of initiator also provide polymers with higher molecular weights. Higher pressure favors polymers with relatively higher molecular weights. The applications of these soy-based materials will be in the lubrication and hydraulic fluid areas. PMID:17206812

  7. Effect of high-speed jet on flow behavior, retrogradation, and molecular weight of rice starch.

    PubMed

    Fu, Zhen; Luo, Shun-Jing; BeMiller, James N; Liu, Wei; Liu, Cheng-Mei

    2015-11-20

    Effects of high-speed jet (HSJ) treatment on flow behavior, retrogradation, and degradation of the molecular structure of indica rice starch were investigated. Decreasing with the number of HSJ treatment passes were the turbidity of pastes (degree of retrogradation), the enthalpy of melting of retrograded rice starch, weight-average molecular weights and weight-average root-mean square radii of gyration of the starch polysaccharides, and the amylopectin peak areas of SEC profiles. The areas of lower-molecular-weight polymers increased. The chain-length distribution was not significantly changed. Pastes of all starch samples exhibited pseudoplastic, shear-thinning behavior. HSJ treatment increased the flow behavior index and decreased the consistency coefficient and viscosity. The data suggested that degradation of amylopectin was mainly involved and that breakdown preferentially occurred in chains between clusters.

  8. Molecular weight changes induced in an anionic polydimethylsiloxane by gamma irradiation in vacuum

    NASA Astrophysics Data System (ADS)

    Satti, Angel J.; Andreucetti, Noemí A.; Ciolino, Andrés E.; Vitale, Cristian; Sarmoria, Claudia; Vallés, Enrique M.

    2010-11-01

    An anionic almost monodisperse linear polydimethylsiloxane (PDMS) was subjected to gamma irradiation under vacuum at room temperature. The molecular weight changes induced by the radiation process have been investigated using size exclusion chromatography (SEC) with refraction index (RI) and multi angle laser light scattering (MALLS) detectors, to obtain the number and weight average molecular weights of the irradiated samples. The analysis of the data indicates that crosslinking reactions predominated over scission reactions. The results obtained by an SEC-RI have confirmed the presence of small, but measurable amounts of scission. A previously developed mathematical model of the irradiation process that accounts for simultaneous scission and crosslinking and allows for both H- and Y-crosslinks, fitted well the measured molecular weight data. This prediction is in accordance with the experimental data obtained by 29Si-Nuclear Magnetic Resonance spectroscopy (NMR) and previously reported data for commercial linear PDMS ( Satti et al., 2008).

  9. Slip of polydisperse polymers: Molecular weight distribution above and below the plane of slip

    NASA Astrophysics Data System (ADS)

    Sabzevari, Seyed Mostafa; Strandman, Satu; Wood-Adams, Paula Marie

    2015-04-01

    When strong slip occurs during the drag flow of highly entangled polybutadienes (PBD) in a sliding plate rheometer equipped with stainless steel parallel plates, a thin film of polymer debris remains on the substrate after the slip. This debris is assumed to be formed by the disentanglement process that occurs in strong slip at a distance of about one molecular size from the plate. In order to evaluate the composition of the debris we collected it with tetrahydrofuran and subjected it to gel permeation chromatography. It was found that the molecular weight distribution (MWD) of the debris is significantly different from that of the bulk. Moreover, in mixtures prepared from long and short PBDs with distinctly different molecular weight distributions, the MWD of the debris was found to be richer in low molecular weight components and leaner in the high molecular weight components compared to the bulk. This information is important since it reveals the compositional difference between the bulk and interfacial layer above and below the plane of slip. The difference in MWD is likely a consequence of the strong slip in which some of long chains are pulled away from the surface-adsorbed chains by the flow leaving a debris lean in the high molecular weight component.

  10. Profiling of the Molecular Weight and Structural Isomer Abundance of Macroalgae-Derived Phlorotannins

    PubMed Central

    Heffernan, Natalie; Brunton, Nigel P.; FitzGerald, Richard J.; Smyth, Thomas J.

    2015-01-01

    Phlorotannins are a group of complex polymers of phloroglucinol (1,3,5-trihydroxybenzene) unique to macroalgae. These phenolic compounds are integral structural components of the cell wall in brown algae, but also play many secondary ecological roles such as protection from UV radiation and defense against grazing. This study employed Ultra Performance Liquid Chromatography (UPLC) with tandem mass spectrometry to investigate isomeric complexity and observed differences in phlorotannins derived from macroalgae harvested off the Irish coast (Fucus serratus, Fucus vesiculosus, Himanthalia elongata and Cystoseira nodicaulis). Antioxidant activity and total phenolic content assays were used as an index for producing phlorotannin fractions, enriched using molecular weight cut-off dialysis with subsequent flash chromatography to profile phlorotannin isomers in these macroalgae. These fractions were profiled using UPLC-MS with multiple reaction monitoring (MRM) and the level of isomerization for specific molecular weight phlorotannins between 3 and 16 monomers were determined. The majority of the low molecular weight (LMW) phlorotannins were found to have a molecular weight range equivalent to 4–12 monomers of phloroglucinol. The level of isomerization within the individual macroalgal species differed, resulting in substantially different numbers of phlorotannin isomers for particular molecular weights. F. vesiculosus had the highest number of isomers of 61 at one specific molecular mass, corresponding to 12 phloroglucinol units (PGUs). These results highlight the complex nature of these extracts and emphasize the challenges involved in structural elucidation of these compounds. PMID:25603345

  11. Profiling of the molecular weight and structural isomer abundance of macroalgae-derived phlorotannins.

    PubMed

    Heffernan, Natalie; Brunton, Nigel P; FitzGerald, Richard J; Smyth, Thomas J

    2015-01-16

    Phlorotannins are a group of complex polymers of phloroglucinol (1,3,5-trihydroxybenzene) unique to macroalgae. These phenolic compounds are integral structural components of the cell wall in brown algae, but also play many secondary ecological roles such as protection from UV radiation and defense against grazing. This study employed Ultra Performance Liquid Chromatography (UPLC) with tandem mass spectrometry to investigate isomeric complexity and observed differences in phlorotannins derived from macroalgae harvested off the Irish coast (Fucus serratus, Fucus vesiculosus, Himanthalia elongata and Cystoseira nodicaulis). Antioxidant activity and total phenolic content assays were used as an index for producing phlorotannin fractions, enriched using molecular weight cut-off dialysis with subsequent flash chromatography to profile phlorotannin isomers in these macroalgae. These fractions were profiled using UPLC-MS with multiple reaction monitoring (MRM) and the level of isomerization for specific molecular weight phlorotannins between 3 and 16 monomers were determined. The majority of the low molecular weight (LMW) phlorotannins were found to have a molecular weight range equivalent to 4-12 monomers of phloroglucinol. The level of isomerization within the individual macroalgal species differed, resulting in substantially different numbers of phlorotannin isomers for particular molecular weights. F. vesiculosus had the highest number of isomers of 61 at one specific molecular mass, corresponding to 12 phloroglucinol units (PGUs). These results highlight the complex nature of these extracts and emphasize the challenges involved in structural elucidation of these compounds.

  12. The effect of molecular weight on the adsorption/desorption characteristics of polymeric scale inhibitors on silica sand and in sandstone cores

    SciTech Connect

    Graham, G.M.; Sorbie, K.S.

    1994-12-31

    A number of polymeric scale inhibitors are currently used for downhole application in oilfield ``squeeze`` treatments. These materials must perform the dual role of inhibiting scale formation at low concentration levels whilst giving acceptably long return curves at the wellbore. Both of these design aspects of polymeric scale inhibitors relate to their adsorption characteristics (either on the growing scale crystal or onto the rock substrate) which, in turn, are functions of the molecular weight of the species. In this paper, the authors examine the effects of inhibitor molecular weight on its adsorption characteristics onto highly quartzitic substrates and they discuss the importance of this factor in governing the dynamics of the inhibitor return curve. The effects of molecular weight on the inhibition efficiency, during both early nucleation and later crystal growth, are also examined. The adsorption/desorption characteristics of three polymeric scale inhibitors, each having a range of molecular weights, are studied in this work: viz. polyacrylate (PAA) and phosphinopolycarboxylate (PPCA) scale inhibitors of weight average molecular weight, M{sub w} < 10,000 g/mol, and polyvinyl sulphonic acid (PVS) inhibitors of M{sub w} < 20,000 g/mol. Using these polymers, the authors show that the preferential adsorption of the higher molecular weight components occurs. Results on the scale inhibition efficiency of barium sulphate, obtained for the same range of polymeric inhibitors, are also presented as functions of molecular weight. The factors required to ensure a long return curve are not necessarily the same as those for efficient inhibition under certain solution conditions (e.g. solution pH). This illustrates the importance of reaching a compromise in terms of molecular weight between inhibition efficiency and squeeze lifetime. The significance of these findings for field squeeze treatments using polymeric inhibitors is discussed. 43 refs.

  13. [The molecular-weight characteristics of the bacterial lectins and humus components in soil].

    PubMed

    Votselko, S K; Iutinskaia, G A; Kovalenko, E A; Kucheriavaia, N S

    2000-01-01

    A method has been developed to determine the molecular-weight distribution of biologically active substances: bacterial lectins and soil humus compounds. The method based on the simultaneous centrifugation of samples and molecular weight standards in the density gradient of NaCl solutions or combined gradient of NaCl and CsCl solutions permits analysing biologically active substances: lectins, proteins, polysaccharides, protein-polysaccharide complexes, humus compounds in the interval of molecular weight of 13.7 kappa [symbol: see text] a to 2000 kappa [symbol: see text] a. The use of this method in the soil researches makes it possible to study the dynamics of change of molecular parameters of the soil organic matter depending on agrotechnical methods as well as to determine transformation regularities of microbial polysaccharides.

  14. Adsorption of dissolved organics in lake water by aluminum oxide. Effect of molecular weight

    USGS Publications Warehouse

    Davis, J.A.; Gloor, R.

    1981-01-01

    Dissolved organic compounds in a Swiss lake were fractionated into three molecular size classes by gel exclusion chromatography, and adsorption of each fraction on colloidal alumina was studied as a function of pH. Organic compounds with molecular weight (Mr) greater than 1000 formed strong complexes with the alumina surface, but low molecular weight compounds were weakly adsorbed. Electrophoretic mobility measurements indicated that alumina particles suspended in the original lake water were highly negatively charged because of adsorbed organic matter. Most of the adsorbed organic compounds were in the Mr range 1000 < Mr < 3000. Adsorption of these compounds during the treatment of drinking water by alum coagulation may be responsible for the preferential removal of trihalomethane precursors. Adsorption may also influence the molecular-weight distribution of dissolved organic material in lakes. surface, the present work will focus on the influence of molecular size and pH on the adsorption behavior of dissolved organic material of a Swiss lake. From a geochemical point of view, it is important to know the molecular-weight distribution of adsorbed organic matter so that we may better assess its reactivity with trace elements. The study also serves as a first step in quantifying the role of adsorption in the geochemical cycle of organic carbon in lacustrine environments. For water-treatment practice, we need to determine whether molecular weight fractionation occurs during adsorption by aluminum oxide. Such a fractionation could be significant in the light of recent reports that chloroform and other organochlorine compounds are preferentially produced by particular molecular-weight fractions (25-27). ?? 1981 American Chemical Society.

  15. Characterization of durum wheat high molecular weight glutenin subunits Bx20 and By20 sequences by a molecular and proteomic approach.

    PubMed

    Santagati, Vito Davide; Sestili, Francesco; Lafiandra, Domenico; D'Ovidio, Renato; Rogniaux, Helene; Masci, Stefania

    2016-07-01

    Wheat high molecular weight glutenin subunit variation is important because of its great influence on glutenin polymer structure, that is related to dough technological properties. Among the different subunits, the pair Bx20 and By20 is known to have a negative effect on quality, but the reasons are not clear: Bx20 has two cysteines, which theoretically make this subunit a chain extender of the glutenin polymer, just like the other Bx subunits, showing four cysteines, two of which should be involved in intra-molecular disulfide bonds. By20 has never been characterized so far at molecular level. Here we report the nucleotide sequences of Bx20 and By20 genes isolated from the durum wheat cultivar 'Lira 45' and the validation of the corresponding deduced amino acid sequences by using MALDI-TOF and LC-MS/MS. Four nucleotide differences were identified in the Bx20 gene with respect to the deduced sequence present in NCBI, causing two amino acid substitutions. For the By20 subunit, nucleotide and amino acid sequences revealed a great similarity to By15, both at gene and protein levels, showing five nucleotide changes generating two amino acid differences. No evidence of post-translational modifications has been found. Hypotheses are formulated in regard to relationships with technological quality. Copyright © 2016 John Wiley & Sons, Ltd.

  16. Molecular cloning and amino acid sequence of human 5-lipoxygenase

    SciTech Connect

    Matsumoto, T.; Funk, C.D.; Radmark, O.; Hoeoeg, J.O.; Joernvall, H.; Samuelsson, B.

    1988-01-01

    5-Lipoxygenase (EC 1.13.11.34), a Ca/sup 2 +/- and ATP-requiring enzyme, catalyzes the first two steps in the biosynthesis of the peptidoleukotrienes and the chemotactic factor leukotriene B/sub 4/. A cDNA clone corresponding to 5-lipoxygenase was isolated from a human lung lambda gt11 expression library by immunoscreening with a polyclonal antibody. Additional clones from a human placenta lambda gt11 cDNA library were obtained by plaque hybridization with the /sup 32/P-labeled lung cDNA clone. Sequence data obtained from several overlapping clones indicate that the composite DNAs contain the complete coding region for the enzyme. From the deduced primary structure, 5-lipoxygenase encodes a 673 amino acid protein with a calculated molecular weight of 77,839. Direct analysis of the native protein and its proteolytic fragments confirmed the deduced composition, the amino-terminal amino acid sequence, and the structure of many internal segments. 5-Lipoxygenase has no apparent sequence homology with leukotriene A/sub 4/ hydrolase or Ca/sup 2 +/-binding proteins. RNA blot analysis indicated substantial amounts of an mRNA species of approx. = 2700 nucleotides in leukocytes, lung, and placenta.

  17. An optimal polymerization process for low mean molecular weight HBOC with lower dimer.

    PubMed

    Zhou, Wentao; Li, Shen; Hao, Shasha; Liu, Jiaxin; Wang, Hong; Yang, Chengmin

    2015-06-01

    The new research tried to improve the distribution of molecular weight of Hb-based oxygen carriers (HBOC), a bottleneck of glutaraldehyde (GDA)-polymerization process. The orthogonal experiments were done on the basis of the early study of human placenta Hemoglobin (Hb)-crosslinked-GDA and three factors were selected including the molar ratio of GDA and Hb, Hb concentration, and the rate of the feeding GDA. The optimal match condition of polymerization process prepared for the purpose of lower mean molecular weight, content of super-weight molecule, and the content of dimer. The results showed that the molar ratio of GDA and Hb was the greatest influencing factor on the molecular weight distribution of polymerized-Hb, followed by the Hb concentration, and the last is the rate of feeding GDA. The optimum matching conditions had reached the objective that the mean molecular weight with 155.54 ± 5.79, the content of dimer with 17.23 ± 3.71, and content of super-weight molecule with 0.17 ± 0.09, and the results can be repeated in the 30 times expansion experiments.

  18. Kinetics of model high molecular weight organic compounds biodegradation in soil aquifer treatment.

    PubMed

    Fox, Peter; Makam, Roshan

    2011-10-01

    Soil Aquifer Treatment (SAT) is a process where treated wastewater is purified during transport through unsaturated and saturated zones. Easily biodegradable compounds are rapidly removed in the unsaturated zone and the residual organic carbon is comprised of primarily high molecular weight compounds. This research focuses on flow in the saturated zone where flow conditions are predictable and high molecular weight compounds are degraded. Flow through the saturated zone was investigated with 4 reactors packed with 2 different particle sizes and operated at 4 different flow rates. The objective was to evaluate the kinetics of transformation for high molecular weight organics during SAT. Dextran was used as a model compound to eliminate the complexity associated with studying a mixture of high molecular weight organics. The hydrolysis products of dextran are easily degradable sugars. Batch experiments with media taken from the reactors were used to determine the distribution of microbial activity in the reactors. Zero-order kinetics were observed for the removal of dextran in batch experiments which is consistent with hydrolysis of high molecular weight organics where extracellular enzymes limit the substrate utilization rate. Biomass and microbial activity measurements demonstrated that the biomass was independent of position in the reactors. A Monod based substrate/biomass growth kinetic model predicted the performance of dextran removal in the reactors. The rate limiting step appears to be hydrolysis and the overall rate was not affected by surface area even though greater biomass accumulation occurred as the surface area decreased. PMID:21723581

  19. Kinetics of model high molecular weight organic compounds biodegradation in soil aquifer treatment.

    PubMed

    Fox, Peter; Makam, Roshan

    2011-10-01

    Soil Aquifer Treatment (SAT) is a process where treated wastewater is purified during transport through unsaturated and saturated zones. Easily biodegradable compounds are rapidly removed in the unsaturated zone and the residual organic carbon is comprised of primarily high molecular weight compounds. This research focuses on flow in the saturated zone where flow conditions are predictable and high molecular weight compounds are degraded. Flow through the saturated zone was investigated with 4 reactors packed with 2 different particle sizes and operated at 4 different flow rates. The objective was to evaluate the kinetics of transformation for high molecular weight organics during SAT. Dextran was used as a model compound to eliminate the complexity associated with studying a mixture of high molecular weight organics. The hydrolysis products of dextran are easily degradable sugars. Batch experiments with media taken from the reactors were used to determine the distribution of microbial activity in the reactors. Zero-order kinetics were observed for the removal of dextran in batch experiments which is consistent with hydrolysis of high molecular weight organics where extracellular enzymes limit the substrate utilization rate. Biomass and microbial activity measurements demonstrated that the biomass was independent of position in the reactors. A Monod based substrate/biomass growth kinetic model predicted the performance of dextran removal in the reactors. The rate limiting step appears to be hydrolysis and the overall rate was not affected by surface area even though greater biomass accumulation occurred as the surface area decreased.

  20. The effect of molecular weight on the material properties of biosynthesized poly(4-hydroxybutyrate).

    PubMed

    Boesel, Luciano F; Le Meur, Sylvaine; Thöny-Meyer, Linda; Ren, Qun

    2014-11-01

    Poly(4-hydroxybutyrate) (P4HB) is a bacterial polyhydroxyalkanoate with interesting biological and physico-chemical properties for the use in biomedical applications. The synthesis of P4HB through a fermentation process often leads to a polymer with a too high molecular weight, making it difficult to process it further by solvent- or melt-processing. In this work P4HB was degraded to obtain polymers with a molecular weight ranging from 1.5×10(3)g/mol to 1.0×10(6)g/mol by using a method established in our laboratory. We studied the effect of the change in molecular weight on thermal and mechanical properties. The decrease of the molecular weight led to an increase in the degree of crystallinity of the polymer. Regarding the tensile mechanical properties, the molecular weight played a more prominent role than the degree of crystallinity in the evolution of the properties for the different polymer fractions. The method presented herein allows the preparation of polymer fractions with easier processability and still adequate thermal and mechanical properties for biomedical applications.

  1. Anticancer properties of low molecular weight oat beta-glucan – An in vitro study.

    PubMed

    Choromanska, Anna; Kulbacka, Julita; Rembialkowska, Nina; Pilat, Justyna; Oledzki, Remigiusz; Harasym, Joanna; Saczko, Jolanta

    2015-09-01

    Anticancer properties of 1-3, 1-4 oat beta glucan are under intensive investigation now. Antitumor characteristic of fungi and yeast beta-glucans have been widely recognized, but those polysaccharides are mostly insoluble which creates several problems especially in topical formulation. Also high molecular weight oat beta-glucans reveal high viscosity which restricts its application. According to those problems in the current study the antitumor activities of low molecular weight beta-glucan derived from oats were investigated in cancer cells: Me45, A431 and normal HaCaT and murine macrophages P388/D1. The low molecular weight beta-glucan from oat significantly deceased cancer cells viability, while for the normal cells it was non-toxic. It was observed that with the increasing incubation time and the beta-glucan concentration the cancer cells viability significantly deceased. Furthermore for the normal cells the low molecular weight beta-glucan from oat was non-toxic. Immunocytochemical ABC analysis showed that beta-glucan induced strong expression of caspase-12 in both cancer cell lines, while in HaCaT cells ABC reaction was significantly lower and in P388/D1 cell line ABC reaction was negative. Our preliminary studies show strong anti-tumor properties of new low molecular weight beta-glucan from oat and at the same time no toxicity for normal cells.

  2. Pollutant removal from aquaculture wastewater using the biopolymer chitosan at different molecular weights.

    PubMed

    Chung, Ying-Chien; Li, Yi-He; Chen, Chiing-Chang

    2005-01-01

    Removal of organic compounds, inorganic nutrients, and bacteria from aquaculture wastewaters before discharge cannot only minimize deterioration of receiving water quality, but can also make possible the reuse of the original water in the culture of prawn, fish, and shellfish. In this study, the feasibility of using chitosan, a multifunctional environmentally friendly biopolymer, at different molecular weights to simultaneously remove various pollutants from the discharge of an eel culture pond is evaluated. Experimental results indicated chitosan with a high molecular weight was best at removing turbidity, suspended solids, and biological and chemical oxygen demand (BOD and COD). In contrast, chitosan of a low molecular weight excelled at removing NH3 and PO4(3-) from wastewater. Additionally, chitosan with a high molecular weight did well at eliminating suspended solids of various particle sizes relative to chitosan with a low molecular weight. The best performance of chitosan in removing turbidity, suspended solids, BOD, COD, NH3, PO4(3-), and bacteria was 87.7%, 62.6%, 52.3%, 62.8%, 91.8%, 99.1%, and 99.998% removal, respectively. When chitosan with a high molecular weight was added at 12 mg/L, the quality of treated wastewater successfully complied with government discharge standards. Furthermore, the relatively low bacteria amount in the wastewater after treatment with chitosan was confirmed by both the plate count method and molecular analysis technique. These results indicated that the application of chitosan is feasible in an effort to recycle the effluents of a culture pond.

  3. The Role of Molecular Weight and Temperature on the Elastic and Viscoelastic Properties of a Glassy Thermoplastic Polyimide

    NASA Technical Reports Server (NTRS)

    Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.

    2001-01-01

    Mechanical testing of the elastic and viscoelastic response of an advanced thermoplastic polyimide (LaRC-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The notched tensile strength was shown to be a strong function of both molecular weight and temperature, whereas stiffness was only a strong function of temperature. A critical molecular weight was observed to occur at a weight average molecular weight of M, approx. 22,000 g/mol below which, the notched tensile strength decreases rapidly. This critical molecular weight transition is temperature-independent. Low, molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. Furthermore, low molecular weight materials have increased creep compliance and creep compliance rate, and are more sensitive to temperature than the high molecular weight materials. At long timescales (less than 1100 hours) physical aging serves to significantly decrease the creep compliance and creep rate of all the materials tested. Low molecular weight materials are less influenced by the effects of physical aging.

  4. Suppressive Effects of Barley β-Glucans with Different Molecular Weight on 3T3-L1 Adipocyte Differentiation.

    PubMed

    Zhu, Yingying; Yao, Yang; Gao, Yue; Hu, Yibo; Shi, Zhenxing; Ren, Guixing

    2016-03-01

    In this study, 2 β-glucans with different molecular weight were prepared and purified from hull-less barley bran. The aim was to evaluate their effects on the differentiation of 3T3-L1 pre-adipocytes. Results showed that barley β-glucans inhibited the differentiation of 3T3-L1 pre-adipocytes induced by differentiation medium in a dose-dependent manner, the suppressive effect of high-molecular-weight barley β-glucans (552 kDa, BGH) was stronger (P < 0.05) than that of low-molecular-weight barley β-glucan (32 kDa, BGL), evidenced by the significantly decrease (P < 0.05) of Oil-red O staining and intracellular triglyceride content in the mature adipocytes. Besides, gene expression analysis and Western Blot analysis revealed that both BGH and BGL inhibited the mRNA and protein levels of adipogenesis related transcription factors peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT-enhancer-binding protein α (C/EBPα) which are principal regulators of adipogenesis. Furthermore, the mRNA and protein expression levels of PPARγ target genes in adipose tissue including adipocyte fatty acid binding protein (ap2), lipoprotein lipase (LPL), uncoupling protein-2 (UCP-2), and glucose-transporter 4 (Glut4) in 3T3-L1 cells was also markedly downregulated (P < 0.05). These findings were anticipated to help develop barley β-glucans based functional food for the management of obesity.

  5. Application of computer-assisted molecular modeling (CAMM) for immunoassay of low molecular weight food contaminants: A review

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Immunoassay for low molecular weight food contaminants, such as pesticides, veterinary drugs, and mycotoxins is now a well-established technique which meets the demands for a rapid, reliable, and cost-effective analytical method. However, due to limited understanding of the fundamental aspects of i...

  6. Advances in the understanding of low molecular weight silicon formation and implications for control by AMC filters

    NASA Astrophysics Data System (ADS)

    Lobert, Jürgen M.; Cate, Philip W.; Ruede, David J.; Wildgoose, Joseph R.; Miller, Charles M.; Gaudreau, John C.

    2010-03-01

    Trimethylsilanol (TMS) is a low molecular weight / low boiling point silicon-containing, airborne contaminant that has received increased interest over the past few years as an important cause for contamination of optical surfaces in lithography equipment. TMS is not captured well by carbon-based filters, and hexamethyldisiloxane (HMDSO), even though captured well, can be converted to TMS when using acidic filter media commonly used for ammonia removal. TMS and HMDSO co-exist in a chemical equilibrium, which is affected by the acidity and moisture of their environment. This publication shows that HMDSO is converted to TMS by acidic media at concentrations typically found in cleanroom environments. This is contrary to published results that show a re-combination of TMS to HMDSO on acid media. We also demonstrate that, based on its conversion to TMS, HMDSO is not a suitable test compound for hybrid chemical filter performance, as the apparent lifetime/capacity of the filter can be substantially skewed towards larger numbers when conversion to TMS is involved. We show lifetime test results with toluene and HMDSO on acidic and non-acidic filter media. Appropriately designed, asymmetric hybrid chemical filters significantly minimize or eliminate the conversion of HMDSO to TMS, thereby reducing the risk to scanner optical elements. Similarly, such filters can also prevent or reduce acid-sensitive reactions of other AMC when passing through filter systems.

  7. Effect of molecular weight on ion diffusion and transference number in poly(ethylene oxide)

    NASA Astrophysics Data System (ADS)

    Timachova, Ksenia; Balsara, Nitash

    2015-03-01

    Solid polymer electrolytes are of great interest for their potential use in high specific energy, solid-state batteries, however, salt transport properties in polymer electrolytes have not been comprehensively addressed over a wide range of molecular weights. Poly(ethylene oxide) (PEO) has been the most widely studied polymer electrolyte due to its high solvation of lithium salts and low glass transition temperature. This study presents measurements of the transport properties of lithium bis(trifluoromethanesulfone)imide (LiTFSI) in PEO at both the high concentration present in functional electrolytes and in the dilute limit for a large range of PEO molecular weights. Individual diffusion coefficients of the Li + and TFSI- ions were measured using pulsed-field gradient nuclear magnetic resonance and the cation transference number was calculated. The diffusion coefficients, transference number, and conductivity as a function of molecular weight and salt concentration provide a complete set of transport properties for PEO.

  8. Molecular weight of DNA from four entomopoxviruses determined by electron microscopy.

    PubMed Central

    Langridge, W H; Roberts, D W

    1977-01-01

    DNA was isolated from entomopoxviruses infected Amsacta moorei and Euxoa auxiliaris (Lepidoptera), Goeldichironomus holoprasinus (Diptera), and Othnonius batesi (Coleoptera) and compared with vertebrate virus DNA (vaccinia). After incubation in Pronase, sodium lauryl sulfate, and deoxycholate, poxvirus preparations shadowed with platinum and palladium revealed subcore particles 45 to 60 nm in diameter. Continued incubation in Pronase resulted in the gradual release of DNA from the particles. Metal-shadowed DNA molecules were photographed in the electron microscope and measured, and the average molecular weights were calculated. Lepidopteran poxvirus DNA (135 X 10(6)) was approximately equal to vaccinia DNA (131.7 X 10(6)) in molecular weight. The molecular weight of dipteran and coleopteran poxvirus DNA (200 X 10(6) to 251 X 10(6)) was approximately 50% greater than vaccinia DNA. Based on the concentration of DNA and protein per virion, Amsacta entomopoxvirus contained 5.7 to 7.7% DNA. Images PMID:833926

  9. Low Molecular Weight Chitosan–Insulin Polyelectrolyte Complex: Characterization and Stability Studies

    PubMed Central

    Al-Kurdi, Zakieh I.; Chowdhry, Babur Z.; Leharne, Stephen A.; Al Omari, Mahmoud M. H.; Badwan, Adnan A.

    2015-01-01

    The aim of the work reported herein was to investigate the effect of various low molecular weight chitosans (LMWCs) on the stability of insulin using USP HPLC methods. Insulin was found to be stable in a polyelectrolyte complex (PEC) consisting of insulin and LMWC in the presence of a Tris-buffer at pH 6.5. In the presence of LMWC, the stability of insulin increased with decreasing molecular weight of LMWC; 13 kDa LMWC was the most efficient molecular weight for enhancing the physical and chemical stability of insulin. Solubilization of insulin-LMWC polyelectrolyte complex (I-LMWC PEC) in a reverse micelle (RM) system, administered to diabetic rats, results in an oral delivery system for insulin with acceptable bioactivity. PMID:25830681

  10. Preparation of different molecular weight polysaccharides from Porphyridium cruentum and their antioxidant activities.

    PubMed

    Sun, Liqin; Wang, Changhai; Shi, Quanjian; Ma, Cuihua

    2009-07-01

    Hermetical microwave was used to degrade Porphyridium cruentum polysaccharides from 2918 to 256.2, 60.66 and 6.55kDa. The antioxidant properties of different molecular weight polysaccharides were evaluated by determining the scavenging ability of free radicals, inhibitory effects on lipid peroxidation in liver homogenates and hemolysis of mouse erythrocytes. Analysis of physicochemical properties confirmed that microwave degradation might not markedly change the chemical components of the polysaccharides. High-molecular-weight polysaccharides from P. cruentum had no obvious antioxidant activity, but low-molecular-weight fragments after degradation exerted an inhibitory effect on oxidative damage. The 6.55-kDa fragment had stronger antioxidant activity than the 60.66 and 256-kDa fragments.

  11. The development of low-molecular weight hydrogels for applications in cancer therapy

    NASA Astrophysics Data System (ADS)

    Tian, Ran; Chen, Jin; Niu, Runfang

    2014-03-01

    To improve the anti-cancer efficacy and to counteract the side effects of chemotherapy, a variety of drug delivery systems have been invented in past decades, but few of these systems have succeeded in clinical trials due to their respective inherent shortcomings. Recently, low-molecular weight hydrogels of peptides that self-assemble via non-covalent interactions have attracted considerable attention due to their good biocompatibility, low toxicity, inherent biodegradability as well as their convenience of design. Low-molecular weight hydrogels have already shown promise in biomedical applications as diverse as 3D-cell culture, enzyme immobilization, controllable MSC differentiation, wound healing, drug delivery etc. Here we review the recent development in the use of low-molecular weight hydrogels for cancer therapy, which may be helpful in the design of soft materials for drug delivery.

  12. Characteristics and bioactivities of different molecular weight polysaccharides from camellia seed cake.

    PubMed

    Xu, Zhou; Li, Xu; Feng, Shiling; Liu, Jing; Zhou, Lijun; Yuan, Ming; Ding, Chunbang

    2016-10-01

    Four polysaccharides, namely COP-1, COP-2, COP-3 and COP-4, were ultrafiltrated from crud Camellia oleifera seed cake polysaccharides (COP-c), purified, and characterized, including the determination of antioxidant and antiproliferative activities. Their molecular weights were 7.9, 36, 83 and 225kDa, respectively. All COPs showed the similar FT-IR spectrums, but significant differentials in monosaccharide components. COP-2 exhibited the highest radical scavenging abilities. COP-1 has the strongest metal chelating capabilities. Although with higher molecular weight, COP-4 showed the poorest antioxidant abilities. These results suggested appreciate molecular weight COP possessed a better antioxidant activities. Additionally, all COPs had non-significant antiproliferative abilities in HaLa and HepG2 cells.

  13. Manipulating the molecular weight of alginate produced by Azotobacter vinelandii in continuous cultures.

    PubMed

    Díaz-Barrera, Alvaro; Silva, Paulina; Berrios, Julio; Acevedo, Fernando

    2010-12-01

    Alginate production by Azotobacter vinelandii in chemostat cultures was evaluated at different dilution rates (D) and inlet sucrose concentrations of 5 and 20 g l(-1). At the low inlet sucrose concentration, the molecular weight of alginate increased from 800 to 1800 kDa when D increased from 0.05 to 0.10 h(-1), whereas the opposite trend was observed with the high inlet sucrose concentration. This behaviour can be explained by changes in specific sucrose uptake rate. Thus, a decrease in alginate molecular weight was dependent on the specific sucrose uptake rate when this rate was higher than 0.42 g g(-1) h(-1). The manipulation of the D can be used to select the molecular weight of alginate in continuous culture.

  14. Investigation of the molecular weight increase of commercial lignosulfonates by laccase catalysis.

    PubMed

    Areskogh, Dimitri; Li, Jiebing; Gellerstedt, Göran; Henriksson, Gunnar

    2010-04-12

    Lignosulfonates are by-products from the sulfite pulping process. During this process, lignin is liberated from pulp fibers through sulfonation and washed away. As a consequence, the lignosulfonate molecules contain both hydrophobic and hydrophilic moieties. Lignosulfonates are low-value products with limited performance and are used as such as binders, surfactants, and plasticizers in concrete. Lignosulfonates face strong competition from synthetic petroleum-based plasticizers with superior quality. Therefore, increasing the performance of lignosulfonates is desirable not only from a sustainability point of view but also to expand their usage. One important aspect that describes how well lignosulfonates can act as plasticizers is the molecular weight. In this paper, the molecular weight of four commercial lignosulfonates is increased through oxidation by two laccases without utilization of mediators. Different parameters to obtain maximal molecular weight increase were identified and the technical significance of the experiments is discussed.

  15. Encapsulation of bioactive whey peptides in soy lecithin-derived nanoliposomes: Influence of peptide molecular weight.

    PubMed

    Mohan, Aishwarya; McClements, David Julian; Udenigwe, Chibuike C

    2016-12-15

    Encapsulation of peptides can be used to enhance their stability, delivery and bioavailability. This study focused on the effect of the molecular weight range of whey peptides on their encapsulation within soy lecithin-derived nanoliposomes. Peptide molecular weight did not have a major impact on encapsulation efficiency or liposome size. However, it influenced peptide distribution amongst the surface, core, and bilayer regions of the liposomes, as determined by electrical charge (ζ-potential) and FTIR analysis. The liposome ζ-potential depended on peptide molecular weight, suggesting that the peptide charged groups were in different locations relative to the liposome surfaces. FTIR analysis indicated that the least hydrophobic peptide fractions interacted more strongly with choline on the liposome surfaces. The results suggested that the peptides were unequally distributed within the liposomes, even at the same encapsulation efficiency. These findings are important for designing delivery systems for commercial production of encapsulated peptides with improved functional attributes. PMID:27451165

  16. Low-molecular weight metalloproteins in tissues of the narwhal (Monodon monoceros).

    PubMed

    Wagemann, R; Hobden, B

    1986-01-01

    Narwhal (Monodon monoceros) liver and kidney cytosol were fractionated by gel chromatography, anion-exchange chromatography and electrophoresis. Cadmium was associated largely with low molecular weight proteins, while mercury was associated also with high molecular weight proteins, but apparently not because of saturation of the metallothionein mechanism. Eight different electrophoretic bands, four of which were metalloproteins, were found under the "metallothionein" peak. Anion-exchange chromatography yielded five metal peaks while further fractionation on G-50 gave two peaks, one containing almost pure metallothionein (Mt-1) and the other a metalloprotein having twice the molecular weight of metallothionein. Mt-2 was observed, at a much lower concentration than Mt-1, in liver but not kidney. PMID:2874949

  17. Synthetic polycations with controlled charge density and molecular weight as building blocks for biomaterials.

    PubMed

    Kleinberger, Rachelle M; Burke, Nicholas A D; Zhou, Christal; Stöver, Harald D H

    2016-01-01

    A series of polycations prepared by RAFT copolymerization of N-(3-aminopropyl)methacrylamide hydrochloride (APM) and N-(2-hydroxypropyl)methacrylamide, with molecular weights of 15 and 40 kDa, and APM content of 10-75 mol%, were tested as building blocks for electrostatically assembled hydrogels such as those used for cell encapsulation. Complexation and distribution of these copolymers within anionic calcium alginate gels, as well as cytotoxicity, cell attachment, and cell proliferation on surfaces grafted with the copolymers were found to depend on composition and molecular weight. Copolymers with lower cationic charge density and lower molecular weight showed less cytotoxicity and cell adhesion, and were more mobile within alginate gels. These findings aid in designing improved polyelectrolyte complexes for use as biomaterials.

  18. Low molecular weight protein tyrosine phosphatase: Multifaceted functions of an evolutionarily conserved enzyme.

    PubMed

    Caselli, Anna; Paoli, Paolo; Santi, Alice; Mugnaioni, Camilla; Toti, Alessandra; Camici, Guido; Cirri, Paolo

    2016-10-01

    Originally identified as a low molecular weight acid phosphatase, LMW-PTP is actually a protein tyrosine phosphatase that acts on many phosphotyrosine-containing cellular proteins that are primarily involved in signal transduction. Differences in sequence, structure, and substrate recognition as well as in subcellular localization in different organisms enable LMW-PTP to exert many different functions. In fact, during evolution, the LMW-PTP structure adapted to perform different catalytic actions depending on the organism type. In bacteria, this enzyme is involved in the biosynthesis of group 1 and 4 capsules, but it is also a virulence factor in pathogenic strains. In yeast, LMW-PTPs dephosphorylate immunophilin Fpr3, a peptidyl-prolyl-cis-trans isomerase member of the protein chaperone family. In humans, LMW-PTP is encoded by the ACP1 gene, which is composed of three different alleles, each encoding two active enzymes produced by alternative RNA splicing. In animals, LMW-PTP dephosphorylates a number of growth factor receptors and modulates their signalling processes. The involvement of LMW-PTP in cancer progression and in insulin receptor regulation as well as its actions as a virulence factor in a number of pathogenic bacterial strains may promote the search for potent, selective and bioavailable LMW-PTP inhibitors. PMID:27421795

  19. Characterization of high molecular weight disinfection byproducts resulting from chlorination of aquatic humic substances.

    PubMed

    Zhang, Xiangru; Minear, Roger A

    2002-10-01

    Aquatic humic substances react with chlorine to produce numerous disinfection byproducts (DBPs) during chlorination of drinking water. Although low molecular weight (MW) chlorinated DBPs have been intensively studied over the past several decades, relatively little is known about high MW chlorinated DBPs (above 500 Da) that may be associated with adverse health implications. In this work, carrier-free radioactive 36Cl was introduced into a Suwannee River fulvic acid sample to label the chlorine-containing DBPs. By combining the fractionation techniques of ultrafiltration (UF) and size exclusion chromatography (SEC) with the detection of 36Cl, UV, and dissolved organic carbon (DOC), the high MW region in the SEC-36Cl profiles of the chlorinated sample with and without UF was defined. SEC-UV and SEC-DOC profiles were found to be approximately indicative of SEC-36Cl profiles for the high MW region. The MW distribution shows that the high MW chlorinated DBPs were highly dispersed with an average MW around 2000 Da based on calibration with polystyrene sulfonate standards. The Cl/C atomic ratios of the high MW DBPs were roughly constant (0.025), which is much lower than those of the common known chlorinated DBPs.

  20. Surface functionalization of solid state ultra-high molecular weight polyethylene through chemical grafting

    NASA Astrophysics Data System (ADS)

    Sherazi, Tauqir A.; Rehman, Tayyiba; Naqvi, Syed Ali Raza; Shaikh, Ahson Jabbar; Shahzad, Sohail Anjum; Abbas, Ghazanfar; Raza, Rizwan; Waseem, Amir

    2015-12-01

    The surface of ultra-high molecular weight polyethylene (UHMWPE) powder was functionalized with styrene using chemical grafting technique. The grafting process was initiated through radical generation on base polymer matrix in the solid state by sodium thiosulfate, while peroxides formed at radical sites during this process were dissociated by ceric ammonium nitrate. Various factors were optimized and reasonably high level of monomer grafting was achieved, i.e., 15.6%. The effect of different acids as additive and divinyl benzene (DVB) as a cross-linking agent was also studied. Post-grafting sulfonation was conducted to introduce the ionic moieties to the grafted polymer. Ion-exchange capacity (IEC) was measured experimentally and is found to be 1.04 meq g-1, which is in close agreement with the theoretical IEC values. The chemical structure of grafted and functionalized polymer was characterized by attenuated total reflection infrared spectroscopy (ATR-FTIR) and thermal properties were investigated by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Thermal analysis depicts that the presence of radicals on the polymer chain accelerates the thermal decomposition process. The results signify that the chemical grafting is an effective tool for substantial surface modification and subsequent functionalization of polyethylene.

  1. Study on antithrombotic and antiplatelet activities of low molecular weight fucoidan from Laminaria japonica

    NASA Astrophysics Data System (ADS)

    Chen, Anjin; Zhang, Fang; Shi, Jie; Zhao, Xue

    2012-06-01

    The antithrombotic and antiplatelet effects of two fucoidan fractions with low molecular weight and different sulfate content from Laminaria japonica were compared in order to examine the influence of chemical character on their antithrombotic activity and the possible mechanism. Both LMW fucoidan fractions exhibited favorable antithrombotic activity in an Fecl3-induced arterial thrombosis. The antithrombotic activity of LMW fucoidan was related with decrease of TXB2 and whole blood viscosity and hematocrit. LMW fucoidan showed a correlation between anticoagulant, antiaggregant and antithrombotic effects in vivo. For LMW fucoidan, antithrombotic activity required high dose of 5-10 nmol kg-1, concomitantly with increase in anticoagulant activity and inhibition of platelet aggregation. Administration of LMW fucoidan significantly promoted the 6-keto-PGF1α content and decreased the TXB2 content, indicating its inhibition of tissue factor pathway and regulation of metabolism of arachidonic acid. By comparison, highly sulfated fucoidan LF2 with Mw 3900 seemed to be a more suitable choice for antithrombotic drug for its antithrombotic activity accompanied with specific inhibitory activity on platelet aggregation, low anticoagulant activity and low hemorrhagic risk in vivo.

  2. High and low molecular weight tracers for the electron microscopical detection of sialoglycoconjugates.

    PubMed

    Mureşan, V; Simionescu, N

    1987-03-01

    Hydrazide-derivative tracers of different molecular weights have been synthesized for use in the electron microscopical detection of sodium periodate-oxidized sialyl residues of glycoconjugates in various tissues and cells. Haemundecapeptide hydrazide, horseradish peroxidase hydrazide, and Limulus polyphemus haemocyanin hydrazide were obtained by coupling adipic acid dihydrazide to the tracers with the aid of water-soluble carbodiimide. The enzymatic tracers thus prepared retained their peroxidatic activity. On conversion to the hydrazide derivative, the haemocyanin molecule dissociated into its hexameric subunits. In order to test by transmission electron microscopy the ability of the conjugates to bind to the sialoglycoconjugates of endothelial cell surfaces, each tracer was perfused in situ into rat pancreatic vasculature previously oxidized with 1 mM sodium periodate. The three tracers characteristically labelled the various microdomains of the luminal cell coat of the capillary endothelial cell. The electron opacity of the haemocyanin subunits allowed their easy detection when bound to the cell surface or to components of the extracellular matrix. The bound markers were not displaced by a high ionic strength buffer, and did not label desialylated cell surfaces. These results indicate that the three hydrazide-derivative tracers may be useful tools for the electron microscopical detection of cellular and extracellular sialoglycoconjugates. PMID:3597134

  3. Dipeptide-based low-molecular-weight efficient organogelators and their application in water purification.

    PubMed

    Debnath, Sisir; Shome, Anshupriya; Dutta, Sounak; Das, Prasanta Kumar

    2008-01-01

    The development of new low-molecular-weight gelators for organic solvents is motivated by several potential applications of gels as advanced functional materials. In the present study, we developed simple dipeptide-based organogelators with a minimum gelation concentration (MGC) of 6-0.15 %, w/v in aromatic solvents. The organogelators were synthesized using different L-amino acids with nonpolar aliphatic/aromatic residues and by varying alkyl-chain length (C-12 to C-16). The self-aggregation behavior of these thermoreversible organogels was investigated through several spectroscopic and microscopic techniques. A balanced participation of the hydrogen bonding and van der Waals interactions is crucial for efficient organogelation, which can be largely modulated by the structural modification at the hydrogen-bonding unit as well as by varying the alkyl-chain length in both sides of the hydrophilic residue. Interestingly, these organogelators could selectively gelate aromatic solvents from their mixtures with water. Furthermore, the xerogels prepared from the organogels showed a striking property of adsorbing dyes such as crystal violet, rhodamine 6G from water. This dye-adsorption ability of gelators can be utilized in water purification by removing toxic dyes from wastewater.

  4. Biocompatibility of low molecular weight polymers for two-phase partitioning bioreactors.

    PubMed

    Harris, Jesse; Daugulis, Andrew J

    2015-12-01

    Two phase partitioning bioreactors (TPPBs) improve the efficiency of fermentative processes by limiting the exposure of microorganisms to toxic solutes by sequestering them into a non-aqueous phase (NAP). A potential limitation of this technology, when using immiscible organic solvents as the NAP, is the cytoxicity that these materials may exert on the microbes. An improved TPPB configuration is one in which polymeric NAPs are used to replace organic solvents in order to take advantage of their low cost, improved handling qualities, and biocompatibility. A recent study has shown that low molecular weight polymers may confer improved solute uptake relative to high molecular weight polymers (i.e., have higher partition coefficients), but it is unknown whether sufficiently low molecular weight polymers may inhibit cell growth. This study has investigated the biocompatibility of a range of low molecular weight polymers, and compared trends in biocompatibility to the well-established "critical log P" concept. This was achieved by determining the biocompatibility of polypropylene glycol polymers over a molecular weight (MW) range of 425-4,000 to Saccharomyces cerevisiae and Pseudomonas putida, two organisms which have been previously used in TPPB systems. The lower MW polymers were shown to have lower average log P values, and showed more cytotoxicity than polymers of the same structure but with higher molecular weight. Since polymers are generally polydisperse (i.e., polymer samples contain a distribution of MWs), removal of the lower MW fractions via water washing was found to result in improved polymer biocompatibility. These results suggest that the critical log P concept remains useful for describing the toxicity of polymeric substances of different MWs, although it is complicated by the presence of the low MW fractions in the polymers arising from polydispersity.

  5. Increasing the wear resistance of ultra-high molecular weight polyethylene by adding solid lubricating fillers

    SciTech Connect

    Panin, S. V.; Kornienko, L. A.; Poltaranin, M. A.; Ivanova, L. R.; Suan, T. Nguen

    2014-11-14

    In order to compare effectiveness of adding solid lubricating fillers for polymeric composites based on ultra-high molecular weight polyethylene (UHMWPE) with graphite, molybdenum disulfide and polytetrafluoroethylene, their tribotechnical characteristics under dry friction, boundary lubrication and abrasive wearing were investigated. The optimal weight fractions of fillers in terms of improving wear resistance have been determined. The supramolecular structure and topography of wear track surfaces of UHMWPE-based composites with different content of fillers have been studied.

  6. Identification and Characterization of High-Molecular-Weight Glutenin Subunits from Agropyron intermedium

    PubMed Central

    Cao, Shuanghe; Li, Zhixin; Gong, Caiyan; Xu, Hong; Yang, Ran; Hao, Shanting; Wang, Xianping; Wang, Daowen; Zhang, Xiangqi

    2014-01-01

    High-molecular-weight glutenin subunit (HMW-GS) is a primary determinant of processing quality of wheat. Considerable progress has been made in understanding the structure, function and genetic regulation of HMW-GS in wheat and some of its related species, but less is known about their orthologs in Agropyron intermedium, a useful related species for wheat improvement. Here seven HMW-GSs in Ag. intermedium were identified using SDS-PAGE and Western blotting experiments. Subsequently, the seven genes (Glu-1Aix1∼4 and Glu-1Aiy1∼3) encoding the seven HMW-GSs were isolated using PCR technique with degenerate primers, and confirmed by bacterial expression and Western blotting. Sequence analysis indicated that the seven Ag. intermedium HMW-GSs shared high similarity in primary structure to those of wheat, but four of the seven subunits were unusually small compared to the representatives of HMW-GS from wheat and two of them possessed extra cysteine residues. The alignment and clustering analysis of deduced amino acid sequences revealed that 1Aix1 and 1Aiy1 subunits had special molecular structure, belonging to the hybrid type compounding between typical x- and y-type subunit. The xy-type subunit 1Aix1 is composed of the N-terminal of x-type and C-terminal of y-type, whereas yx-type subunit 1Aiy1 comprises the N-terminal of y-type and C-terminal of x-type. This result strongly supported the hypothesis of unequal crossover mechanism that might generate the novel coding sequence for the hybrid type of HMW-GSs. In addition to the aforementioned, the other novel characteristics of the seven subunits were also discussed. Finally, phylogenetic analysis based on HMW-GS genes was carried out and provided new insights into the evolutionary biology of Ag. intermedium. PMID:24503781

  7. Convection enhanced delivery of different molecular weight tracers of gadolinium-tagged polylysine.

    PubMed

    Hardy, Peter A; Keeley, Dan; Schorn, Greg; Forman, Eric; Ai, Yi; Venugopalan, Ramakrishna; Zhang, Zhiming; Bradley, Luke H

    2013-09-30

    Convection enhanced delivery (CED) is a powerful method of circumventing the blood-brain barrier (BBB) to deliver therapeutic compounds directly to the CNS. While inferring the CED distribution of a therapeutic compound by imaging a magnetic resonance (MR)-sensitive tracer has many advantages, however how the compound distribution is affected by the features of the delivery system, its target tissue, and its molecular properties, such as its binding characteristics, charge, and molecular weight (MW) are not fully understood. We used MR imaging of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-tagged polylysine compounds of various MW, in vitro and in vivo, to measure the dependence of compounds MW on CED distribution. For the in vitro studies, the correlation between volume of distribution (Vd) as a function of MW was determined by measuring the T1 of the infused tracers, into 0.6% agarose gels through a multiport catheter. The compounds distributed in the gels inversely proportional to their MW, consistent with convection and unobstructed diffusion through a porous media. For the in vivo studies, Gd-DTPA tagged compounds were infused into the non-human primate putamen, via an implanted multiport catheter connected to a MedStream™ pump, programmed to deliver a predetermined volume with alternating on-off periods to take advantage of the convective and diffusive contributions to Vd. Unlike the gel studies, the higher MW polylysine-tracer infusions did not freely distribute from the multiport catheter in the putamen, suggesting that distribution was impeded by other properties that should also be considered in future tracer design and CED infusion protocols.

  8. Identification and characterization of high-molecular-weight glutenin subunits from Agropyron intermedium.

    PubMed

    Cao, Shuanghe; Li, Zhixin; Gong, Caiyan; Xu, Hong; Yang, Ran; Hao, Shanting; Wang, Xianping; Wang, Daowen; Zhang, Xiangqi

    2014-01-01

    High-molecular-weight glutenin subunit (HMW-GS) is a primary determinant of processing quality of wheat. Considerable progress has been made in understanding the structure, function and genetic regulation of HMW-GS in wheat and some of its related species, but less is known about their orthologs in Agropyron intermedium, a useful related species for wheat improvement. Here seven HMW-GSs in Ag. intermedium were identified using SDS-PAGE and Western blotting experiments. Subsequently, the seven genes (Glu-1Aix1 ∼ 4 and Glu-1Aiy1 ∼ 3) encoding the seven HMW-GSs were isolated using PCR technique with degenerate primers, and confirmed by bacterial expression and Western blotting. Sequence analysis indicated that the seven Ag. intermedium HMW-GSs shared high similarity in primary structure to those of wheat, but four of the seven subunits were unusually small compared to the representatives of HMW-GS from wheat and two of them possessed extra cysteine residues. The alignment and clustering analysis of deduced amino acid sequences revealed that 1Aix1 and 1Aiy1 subunits had special molecular structure, belonging to the hybrid type compounding between typical x- and y-type subunit. The xy-type subunit 1Aix1 is composed of the N-terminal of x-type and C-terminal of y-type, whereas yx-type subunit 1Aiy1 comprises the N-terminal of y-type and C-terminal of x-type. This result strongly supported the hypothesis of unequal crossover mechanism that might generate the novel coding sequence for the hybrid type of HMW-GSs. In addition to the aforementioned, the other novel characteristics of the seven subunits were also discussed. Finally, phylogenetic analysis based on HMW-GS genes was carried out and provided new insights into the evolutionary biology of Ag. intermedium. PMID:24503781

  9. Relationship between chemical structure and the occupational asthma hazard of low molecular weight organic compounds

    PubMed Central

    Jarvis, J; Seed, M; Elton, R; Sawyer, L; Agius, R

    2005-01-01

    Aims: To investigate quantitatively, relationships between chemical structure and reported occupational asthma hazard for low molecular weight (LMW) organic compounds; to develop and validate a model linking asthma hazard with chemical substructure; and to generate mechanistic hypotheses that might explain the relationships. Methods: A learning dataset used 78 LMW chemical asthmagens reported in the literature before 1995, and 301 control compounds with recognised occupational exposures and hazards other than respiratory sensitisation. The chemical structures of the asthmagens and control compounds were characterised by the presence of chemical substructure fragments. Odds ratios were calculated for these fragments to determine which were associated with a likelihood of being reported as an occupational asthmagen. Logistic regression modelling was used to identify the independent contribution of these substructures. A post-1995 set of 21 asthmagens and 77 controls were selected to externally validate the model. Results: Nitrogen or oxygen containing functional groups such as isocyanate, amine, acid anhydride, and carbonyl were associated with an occupational asthma hazard, particularly when the functional group was present twice or more in the same molecule. A logistic regression model using only statistically significant independent variables for occupational asthma hazard correctly assigned 90% of the model development set. The external validation showed a sensitivity of 86% and specificity of 99%. Conclusions: Although a wide variety of chemical structures are associated with occupational asthma, bifunctional reactivity is strongly associated with occupational asthma hazard across a range of chemical substructures. This suggests that chemical cross-linking is an important molecular mechanism leading to the development of occupational asthma. The logistic regression model is freely available on the internet and may offer a useful but inexpensive adjunct to the

  10. The Molecular Genetics of Mycolic Acid Biosynthesis.

    PubMed

    Pawełczyk, Jakub; Kremer, Laurent

    2014-08-01

    Mycolic acids are major and specific long-chain fatty acids that represent essential components of the Mycobacterium tuberculosis cell envelope. They play a crucial role in the cell wall architecture and impermeability, hence the natural resistance of mycobacteria to most antibiotics, and represent key factors in mycobacterial virulence. Biosynthesis of mycolic acid precursors requires two types of fatty acid synthases (FASs), the eukaryotic-like multifunctional enzyme FAS I and the acyl carrier protein (ACP)-dependent FAS II systems, which consists of a series of discrete mono-functional proteins, each catalyzing one reaction in the pathway. Unlike FAS II synthases of other bacteria, the mycobacterial FAS II is incapable of de novo fatty acid synthesis from acetyl-coenzyme A, but instead elongates medium-chain-length fatty acids previously synthesized by FAS I, leading to meromycolic acids. In addition, mycolic acid subspecies with defined biological properties can be distinguished according to the chemical modifications decorating the meromycolate. Nearly all the genetic components involved in both elongation and functionalization of the meromycolic acid have been identified and are generally clustered in distinct transcriptional units. A large body of information has been generated on the enzymology of the mycolic acid biosynthetic pathway and on their genetic and biochemical/structural characterization as targets of several antitubercular drugs. This chapter is a comprehensive overview of mycolic acid structure, function, and biosynthesis. Special emphasis is given to recent work addressing the regulation of mycolic acid biosynthesis, adding new insights to our understanding of how pathogenic mycobacteria adapt their cell wall composition in response to environmental changes.

  11. Polyunsaturated fatty acids in the low-birth-weight infant.

    PubMed

    Friedman, Z

    1979-10-01

    The essentiality of certain PUFAs is related to their capability to be incorporated into lipids and to act as precursor in the formation of prostaglandins. Via phospholipids the EFA's influence the physico-chemical characteristics of biomembranes. EFAs are metabolized differently from nonessential PUFAs. While the nonessential fatty acids are metabolized rapidly, the organism tends to conserve the stores of EFAs. Inhibitions and competitions among the EFAs of the three series (oleic, linoleic, and alpha-linolenic) have been demonstrated. Apparently, for any given chain length the more unsaturated fatty acid has a greater affinity for the enzyme system responsible for further elongation and desaturation. EFAs are also necessary for the proper utilization of the saturated fatty acids. Vitamin E and pyridoxine seem to be involved in EFA metabolism. Normal growth of infants is dependent upon an adequate supply of EFA. The human fetus, like the adult, is unable to synthesize the EFAs, which must therefore be derived from the maternal circulation and pass through the placenta. In the fetus, increased concentration of the polyenoic fatty acids with advanced gestational age may result from increased activity of the fetomaternal unit by preferential transfer of these FAs. Enzymatic activity in the placenta or the fetus may also be responsible for desaturation and elongation of these EFAs. Several clinical manifestations have been ascribed in the human infant to prolonged EFA deficiency; however, none of these findings was noted in a group of sick newborn infants with very rapid onset of deficiency. Platelet dysfunction, decreased prostaglandin biosynthesis and turnover and altered pulmonary surfactant are among the effects of EFA deficiency on infants. Supplementation of the EFAs by the diet, parenterally or by the inunction of oil rich in linoleic acid, were reported to alleviate the symptoms of EFA deficiency. The minimal estimated requirement of linoleic acid is 1% of

  12. Gallic acid: molecular rival of cancer.

    PubMed

    Verma, Sharad; Singh, Amit; Mishra, Abha

    2013-05-01

    Gallic acid, a predominant polyphenol, has been shown to inhibit carcinogenesis in animal models and in vitro cancerous cell lines. The inhibitory effect of gallic acid on cancer cell growth is mediated via the modulation of genes which encodes for cell cycle, metastasis, angiogenesis and apoptosis. Gallic acid inhibits activation of NF-κB and Akt signaling pathways along with the activity of COX, ribonucleotide reductase and GSH. Moreover, gallic acid activates ATM kinase signaling pathways to prevent the processes of carcinogenesis. The data so far available, both from in vivo and in vitro studies, indicate that this dietary polyphenol could be promising agent in the field of cancer chemoprevention.

  13. The lognormal and gamma distribution models for estimating molecular weight distributions of polymers using PGSE NMR

    NASA Astrophysics Data System (ADS)

    Williamson, Nathan H.; Nydén, Magnus; Röding, Magnus

    2016-06-01

    We present comprehensive derivations for the statistical models and methods for the use of pulsed gradient spin echo (PGSE) NMR to characterize the molecular weight distribution of polymers via the well-known scaling law relating diffusion coefficients and molecular weights. We cover the lognormal and gamma distribution models and linear combinations of these distributions. Although the focus is on methodology, we illustrate the use experimentally with three polystyrene samples, comparing the NMR results to gel permeation chromatography (GPC) measurements, test the accuracy and noise-sensitivity on simulated data, and provide code for implementation.

  14. Low molecular weight thermostable {beta}-D-glucosidase from Acidothermus cellulolyticus

    DOEpatents

    Himmel, M.E.; Tucker, M.P.; Adney, W.S.; Nieves, R.A.

    1995-07-11

    A purified low molecular weight {beta}-D-glucosidase is produced from Acidothermus cellulolyticus ATCC 43068. The enzyme is water soluble, possesses activity against pNP-{beta}-D-glucopyranoside, has a high of degree of stability toward heat, exhibits optimal temperature activity at about 65 C at a pH range of from about 2 to about 7, has an inactivation temperature of about 80 C at a pH range of from about 2 to about 7 and has a molecular weight of about 50.5--54.5 kD as determined by SDS-PAGE. 6 figs.

  15. Formulation/cure technology for ultrahigh molecular weight silphenylene-siloxane polymers

    NASA Technical Reports Server (NTRS)

    Hundley, N. H.; Patterson, W. J.

    1985-01-01

    Molecular weights above one million were achieved for methylvinylsilphenylene-siloxane terpolymers using a two-stage polymerization technique which was successfully scaled up to 200 grams. The resulting polymer was vulcanized by two different formulations and compared to an identically formulated commercial methylvinyl silicone on the basis of ultimate strength, Young's modulus, percent elongation at failure, and tear strength. Relative thermal/oxidative stabilities of the elastomers were assessed by gradient and isothermal thermogravimetric analyses performed in both air and nitrogen. The experimental elastomer exhibited enhanced thermal/oxidative stability and possed equivalent or superior mechanical properties. The effect of variations in prepolymer molecular weight on mechanical properties was also investigated.

  16. Process for producing high quality, high molecular weight microcrystalline wax derived from undewaxed bright stock

    SciTech Connect

    Miller, S.J.

    1986-08-26

    A process is described for preparing high molecular weight microcrystalline wax from a hydrocracked, undewaxed bright stock, comprising: (a) contacting the bright stock with hydrogen in the presence of a catalyst having hydrodenitrification activity under conditions effective to reduce the nitrogen content of the stock to produce a substantially nitrogen-free product; (b) contacting the substantially nitrogen-free product with hydrogen in the presence of a catalyst having hydrogenation activity under mild conditions to produce a wax-containing oil; and (c) solvent dewaxing the wax-containing oil to produce high molecular weight microcrystalline wax.

  17. Dyed-polyvinyl alcohol films: molecular weight and hydrolysis degree influence on optical recording

    NASA Astrophysics Data System (ADS)

    Solano, Cristina; Martinez-Ponce, Geminiano; Castañeda, Carlos

    2006-07-01

    An analysis of different polyvinyl alcohol films dyed with Malachite Green is presented. Absorbance and diffraction efficiency of holographic gratings are compared, taking as a parameter the molecular weight and hydrolysis degree of the polymer. It is observed that, using the same dye concentration, the absorption coefficient of the films increases as the molecular weight increases. The absorbance of these plates can be modified when exposed to UV light. In addition, it is found that for holographic recording there is an optimal dye-polymer system film.

  18. Preparation and Characterization of Low Molecular Weight Heparin by Liquid Phase Plasma Method.

    PubMed

    Lee, Do-Jin; Kim, Hangun; Kim, Byung Hoon; Park, Young-Kwon; Lee, Heon; Park, Sung Hoon; Jung, Sang-Chul

    2015-08-01

    An liquid phase plasma process system was applied to the production of low molecular weight heparin. The molecular weight of produed heparin decreased with increasing liquid phase plasma treatment time. The abscission of the chemical bonds between the constituents of heparin by liquid phase plasma reaction did not alter the characteristics of heparin. Formation of any by-products due to side reaction was not observed. It is suggested that heparin was depolymerized by active oxygen radicals produced during the liquid phase plasma reaction.

  19. Quick and easy molecular weight determination with Macintosh computers and public domain image analysis software.

    PubMed

    Seebacher, T; Bade, E G

    1996-10-01

    The program "molecular weights" allows a fast and easy estimation of molecular weights (M(r)), isoelectric point (pI) values and band intensities directly from scanned, polyacrylamide gels, two-dimensional protein patterns and DNA gel images. The image coordinates of M(r) and pI reference standards enable the program to calculate M(r) and pI values in a real time manner for any cursor position. The program requires NIH-Image for Macintosh computers and includes automatic band detection coupled with a densitometric evaluation.

  20. Low molecular weight thermostable .beta.-D-glucosidase from acidothermus cellulolyticus

    DOEpatents

    Himmel, Michael E.; Tucker, Melvin P.; Adney, William S.; Nieves, Rafael A.

    1995-01-01

    A purified low molecular weight .beta.-D-glucosidase is produced from Acidothermus cellulolyticus ATCC 43068. The enzyme is water soluble, possesses activity against pNP-.beta.-D-glucopyranoside, has a high of degree of stability toward heat, exhibits optimal temperature activity at about 65.degree. C. at a pH range of from about 2 to about 7, has an inactivation temperature of about 80.degree. C. at a pH range of from about 2 to about 7 and has a molecular weight of about 50.5-54.5 kD as determineded by SDS-PAGE.

  1. The Vertex Version of Weighted Wiener Number for Bicyclic Molecular Structures.

    PubMed

    Gao, Wei; Wang, Weifan

    2015-01-01

    Graphs are used to model chemical compounds and drugs. In the graphs, each vertex represents an atom of molecule and edges between the corresponding vertices are used to represent covalent bounds between atoms. We call such a graph, which is derived from a chemical compound, a molecular graph. Evidence shows that the vertex-weighted Wiener number, which is defined over this molecular graph, is strongly correlated to both the melting point and boiling point of the compounds. In this paper, we report the extremal vertex-weighted Wiener number of bicyclic molecular graph in terms of molecular structural analysis and graph transformations. The promising prospects of the application for the chemical and pharmacy engineering are illustrated by theoretical results achieved in this paper. PMID:26640513

  2. The Vertex Version of Weighted Wiener Number for Bicyclic Molecular Structures

    PubMed Central

    Gao, Wei; Wang, Weifan

    2015-01-01

    Graphs are used to model chemical compounds and drugs. In the graphs, each vertex represents an atom of molecule and edges between the corresponding vertices are used to represent covalent bounds between atoms. We call such a graph, which is derived from a chemical compound, a molecular graph. Evidence shows that the vertex-weighted Wiener number, which is defined over this molecular graph, is strongly correlated to both the melting point and boiling point of the compounds. In this paper, we report the extremal vertex-weighted Wiener number of bicyclic molecular graph in terms of molecular structural analysis and graph transformations. The promising prospects of the application for the chemical and pharmacy engineering are illustrated by theoretical results achieved in this paper. PMID:26640513

  3. Synthesis of the low molecular weight heat shock proteins in plants

    SciTech Connect

    Mansfield, M.A.; Key, J.L. )

    1987-08-01

    Heat shock of living tissue induces the synthesis of a unique group of proteins, the heat shock proteins. In plants, the major group of heat shock proteins has a molecular mass of 15 to 25 kilodaltons. Accumulation to these proteins to stainable levels has been reported in only a few species. To examine accumulation of the low molecular weight heat shock proteins in a broader range of species, two-dimensional electrophoresis was used to resolve total protein from the following species: soybean (Glycine max L. Merr., var Wayne), pea (Pisum sativum L., var Early Alaska), sunflower (Helianthus annuus L.), wheat (Triticum asetivum L.), rice (Oryza sativa L., cv IR-36), maize (Zea mays L.), pearl millet (Pennisetum americanum L. Leeke, line 23DB), and Panicum miliaceum L. When identified by both silver staining and incorporation of radiolabel, a diverse array of low molecular weight heat shock proteins was synthesized in each of these species. These proteins accumulated to significant levels after three hours of heat shock but exhibited considerable heterogeneity in isoelectric point, molecular weight, stainability, and radiolabel incorporation. Although most appeared to be synthesized only during heat shock, some were detectable at low levels in control tissue. Compared to the monocots, a higher proportion of low molecular weight heat shock proteins was detectable in control tissues from dicots.

  4. Enzymatic depolymerization of gum tragacanth: bifidogenic potential of low molecular weight oligosaccharides.

    PubMed

    Gavlighi, Hassan Ahmadi; Michalak, Malwina; Meyer, Anne S; Mikkelsen, J Dalgaard

    2013-02-13

    Gum tragacanth derived from the plant "goat's horn" (Astragalus sp.) has a long history of use as a stabilizing, viscosity-enhancing agent in food emulsions. The gum contains pectinaceous arabinogalactans and fucose-substituted xylogalacturonans. In this work, gum tragacanth from Astragalus gossypinus was enzymatically depolymerized using Aspergillus niger pectinases (Pectinex BE Color). The enzymatically degraded products were divided into three molecular weight fractions via membrane separation: HAG1 < 2 kDa; 2 kDa < HAG2 < 10 kDa; HAG3 > 10 kDa. Compositional and linkage analyses showed that these three fractions also varied with respect to composition and structural elements: HAG1 and HAG2 were enriched in arabinose, galactose, and galacturonic acid, but low in fucose and xylose, whereas HAG3 was high in (terminal) xylose, fucose, and 1,4-bonded galacturonic acid, but low in arabinose and galactose content. The growth-stimulating potential of the three enzymatically produced gum tragacanth fractions was evaluated via growth assessment on seven different probiotic strains in single-culture fermentations on Bifidobacterium longum subsp. longum (two strains), B. longum subsp. infantis (three strains), Lactobacillus acidophilus , B. lactis, and on one pathogenic strain of Clostridium perfringens . The fractions HAG1 and HAG2 consistently promoted higher growth of the probiotic strains than HAG3, especially of the three B. longum subsp. infantis strains, and the growth promotion on HAG1 and HAG2 was better than that on galactan (control). HAG3 completely inhibited the growth of the C. perfringens strain. Tragacanth gum is thus a potential source of prebiotic carbohydrates that exert no viscosity effects and which may find use as natural functional food ingredients.

  5. Chemical characterization of high molecular weight dissolved organic matter in fresh and marine waters

    NASA Astrophysics Data System (ADS)

    Repeta, Daniel J.; Quan, Tracy M.; Aluwihare, Lihini I.; Accardi, AmyMarie

    2002-03-01

    The high molecular weight fraction of dissolved organic matter in a suite of lakes, rivers, seawater, and marine sediment interstitial water samples was collected by ultrafiltration and characterized by molecular level and spectroscopic techniques. Proton nuclear magnetic resonance spectra of all samples show a high degree of similarity, with major contributions from carbohydrates, bound acetate, and lipids. Molecular level analyses of neutral sugars show seven monosaccharides, rhamnose, fucose, arabinose, xylose, mannose, glucose, and galactose, to be abundant, and to occur in comparable relative amounts in each sample. Previous studies have emphasized the distinctive composition of dissolved humic substances in fresh and marine waters, and have attributed these differences to sources and transformations of organic matter unique to each environment. In contrast we find a large fraction of freshwater high molecular weight dissolved organic matter (HMWDOM; > 1kD) to be indistinguishable from marine HMWDOM in bulk and molecular-level chemical properties. Aquatic HMWDOM is similar in chemical composition to biologically derived acylated heteropolysaccharides isolated from marine algal cultures, suggesting a biological source for some fraction of persistent HMWDOM. High molecular weight DOC contributes 51 ± 26% of the total DOC, and monosaccharides 18 ± 8% of the total HMWDOC in our freshwater samples. These contributions are on average higher and more variable, but not significantly different than for surface seawater (30% and 16% respectively). Biogeochemical processes that produce, accumulate, and recycle DOM may therefore share important similarities and be broadly comparable across a range of environmental settings.

  6. The Combined Influence of Molecular Weight and Temperature on the Aging and Viscoelastic Response of a Glassy Thermoplastic Polyimide

    NASA Technical Reports Server (NTRS)

    Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.

    2000-01-01

    The effect of molecular weight on the viscoelastic performance of an advanced polymer (LaRC-SI) was investigated through the use of creep compliance tests. Testing consisted of short-term isothermal creep and recovery with the creep segments performed under constant load. The tests were conducted at three temperatures below the glass transition temperature of five materials of different molecular weight. Through the use of time-aging-time superposition procedures, the material constants, material master curves and aging-related parameters were evaluated at each temperature for a given molecular weight. The time-temperature superposition technique helped to describe the effect of temperature on the timescale of the viscoelastic response of each molecular weight. It was shown that the low molecular weight materials have higher creep compliance and creep rate, and are more sensitive to temperature than the high molecular weight materials. Furthermore, a critical molecular weight transition was observed to occur at a weight-average molecular weight of M (bar) (sub w) 25000 g/mol below which, the temperature sensitivity of the time-temperature superposition shift factor increases rapidly. The short-term creep compliance data were used in association with Struik's effective time theory to predict the long-term creep compliance behavior for the different molecular weights. At long timescales, physical aging serves to significantly decrease the creep compliance and creep rate of all the materials tested.

  7. Effect of in vivo and in vitro degradation on molecular and mechanical properties of various low-molecular-weight polylactides.

    PubMed

    Mainil-Varlet, P; Curtis, R; Gogolewski, S

    1997-09-01

    The in vivo and in vitro degradation of low-molecular-weight poly(L-lactide), poly(L/D-lactide), and poly (L/DL-lactide) rods was investigated. The low-molecular-weight fast-degrading materials were used to accelerate the degradation process and make the test conditions more critical. In the in vivo study the rods were implanted in the soft tissue of sheep and explanted at 1, 3, 6, and 12 months. In the in vitro experiments the samples were subjected to aging at 37 degrees C in the phosphate buffer using two different modes. In the so-called pseudodynamic mode the aging buffer was regularly replaced if the pH dropped more than 0.5. In the static mode the buffer was not changed over the whole testing period of 52 weeks. The mechanical, molecular, and crystalline properties of the rods were measured and their appearance in the course of aging was evaluated using scanning electron microscopy. It was found that the changes in the mechanical properties of poly(L-lactide), poly(L/D-lactide), and poly(L/DL-lactide) samples subjected to in vitro degradation tests in both the static and pseudodynamic modes are in good approximation with data obtained from the in vivo study. The pH of the buffer solution had no evident effect on the mechanical properties or the rate of degradation as estimated from the drop in molecular weight of the aged samples. The replacement of the aging buffer to maintain a constant pH at 7.4 does not seem to be critical for the degradation of the polylactides. In vitro degradation tests can be used as a relevant procedure for predicting the in vivo functionality of implants from the polylactides used if the criteria for assessing such a functionality are the changes in mechanical properties and molecular weight.

  8. Accurate Molecular Dimensions from Stearic Acid Monolayers.

    ERIC Educational Resources Information Center

    Lane, Charles A.; And Others

    1984-01-01

    Discusses modifications in the fatty acid monolayer experiment to reduce the inaccurate moleculary data students usually obtain. Copies of the experimental procedure used and a Pascal computer program to work up the data are available from the authors. (JN)

  9. Microbial utilization of low molecular weight organics in soil depends on the substances properties

    NASA Astrophysics Data System (ADS)

    Gunina, Anna

    2016-04-01

    Utilization of low molecular weight organic substances (LMWOS) in soil is regulated by microbial uptake from solution and following incorporation of into specific cell cycles. Various chemical properties of LMWOS, namely oxidation state, number of carbon (C) atoms, number of carboxylic (-COOH) groups, can affect their uptake from soil solution and further microbial utilization. The aim of the study was to trace the initial fate (including the uptake from soil solution and utilization by microorganisms) of three main classes of LMWOS, having contrast properties - sugars, carboxylic and amino acids. Top 10 cm of mineral soil were collected under Silver birch stands within the Bangor DIVERSE experiment, UK. Soil solution was extracted by centrifugation at 4000 rpm during 15 min. Soil was spiked with 14C glucose or fructose; malic, succinic or formic acids; alanine or glycine. No additional non-labeled LMWOS were added. 14C was traced in the dissolved organic matter (DOM), CO2, cytosol and soil organic matter (SOM) during one day. To estimate half-life times (T1 /2)of LMWOS in soil solution and in SOM pools, the single and double first order kinetic equations were fitted to the uptake and mineralization dynamics, respectively. The LMWOS T1 /2in DOM pool varied between 0.6-5 min, with the highest T1 /2for sugars (3.7 min) and the lowest for carboxylic acids (0.6-1.4 min). Thus, initial uptake of LMWOS is not a limiting step of microbial utilization. The T1 /2 of carboxylic and amino acids in DOM were closely related with oxidation state, showing that reduced substances remain in soil solution longer, than oxidized. The initial T1 /2 of LMWOS in SOM ranged between 30-80 min, with the longest T1 /2 for amino acids (50-80 min) and the shortest for carboxylic acids (30-48 min). These T1 /2values were in one-two orders of magnitude higher than LMWOS T1 /2 in soil solution, pointing that LMWOS mineralization occur with a delay after the uptake. Absence of correlations between

  10. Proteogenomic Characterization of Novel x-Type High Molecular Weight Glutenin Subunit 1Ax1.1

    PubMed Central

    Ribeiro, Miguel; Bancel, Emmanuelle; Faye, Annie; Dardevet, Mireille; Ravel, Catherine; Branlard, Gérard; Igrejas, Gilberto

    2013-01-01

    Analysis of Portuguese wheat (Triticum aestivum L.) landrace ‘Barbela’ revealed the existence of a new x-type high molecular weight-glutenin subunit (HMW-GS) encoded at the Glu-A1 locus, which we named 1Ax1.1. Using one-dimensional and two-dimensional electrophoresis and mass spectrometry, we compared subunit 1Ax1.1 with other subunits encoded at the Glu-A1 locus. Subunit 1Ax1.1 has a theoretical molecular weight of 93,648 Da (or 91,508 Da for the mature protein) and an isoelectric point (pI) of about 5.7, making it the largest and most acidic HMW-GS known to be encoded at Glu-A1. Specific primers were designed to amplify and sequence 2601 bp of the Glu-A1 locus from the ‘Barbela 28’ wheat genome. A very high level of identity was found between the sequence encoding 1Ax1.1 and those encoding other alleles of the locus. The major difference found was an insertion of 36 amino acids in the central repetitive domain. PMID:23478438

  11. Molecular Weight, Protein Binding Affinity and Methane Mitigation of Condensed Tannins from Mangosteen-peel (Garcinia mangostana L).

    PubMed

    Paengkoum, P; Phonmun, T; Liang, J B; Huang, X D; Tan, H Y; Jahromi, M F

    2015-10-01

    The objectives of this study were to determine the molecular weight of condensed tannins (CT) extracted from mangosteen (Garcinia mangostana L) peel, its protein binding affinity and effects on fermentation parameters including total gas, methane (CH4) and volatile fatty acids (VFA) production. The average molecular weight (Mw) of the purified CT was 2,081 Da with a protein binding affinity of 0.69 (the amount needed to bind half the maximum bovine serum albumin). In vitro gas production declined by 0.409, 0.121, and 0.311, respectively, while CH4 production decreased by 0.211, 0.353, and 0.549, respectively, with addition of 10, 20, and 30 mg CT/500 mg dry matter (DM) compared to the control (p<0.05). The effects of CT from mangosteen-peel on in vitro DM degradability (IVDMD) and in vitro N degradability was negative and linear (p<0.01). Total VFA, concentrations of acetic, propionic, butyric and isovaleric acids decreased linearly with increasing amount of CT. The aforementioned results show that protein binding affinity of CT from mangosteen-peel is lower than those reported for Leucaena forages, however, the former has stronger negative effect on IVDMD. Therefore, the use of mangosteen-peel as protein source and CH4 mitigating agent in ruminant feed requires further investigations.

  12. Molecular Weight, Protein Binding Affinity and Methane Mitigation of Condensed Tannins from Mangosteen-peel (Garcinia mangostana L)

    PubMed Central

    Paengkoum, P.; Phonmun, T.; Liang, J. B.; Huang, X. D.; Tan, H. Y.; Jahromi, M. F.

    2015-01-01

    The objectives of this study were to determine the molecular weight of condensed tannins (CT) extracted from mangosteen (Garcinia mangostana L) peel, its protein binding affinity and effects on fermentation parameters including total gas, methane (CH4) and volatile fatty acids (VFA) production. The average molecular weight (Mw) of the purified CT was 2,081 Da with a protein binding affinity of 0.69 (the amount needed to bind half the maximum bovine serum albumin). In vitro gas production declined by 0.409, 0.121, and 0.311, respectively, while CH4 production decreased by 0.211, 0.353, and 0.549, respectively, with addition of 10, 20, and 30 mg CT/500 mg dry matter (DM) compared to the control (p<0.05). The effects of CT from mangosteen-peel on in vitro DM degradability (IVDMD) and in vitro N degradability was negative and linear (p<0.01). Total VFA, concentrations of acetic, propionic, butyric and isovaleric acids decreased linearly with increasing amount of CT. The aforementioned results show that protein binding affinity of CT from mangosteen-peel is lower than those reported for Leucaena forages, however, the former has stronger negative effect on IVDMD. Therefore, the use of mangosteen-peel as protein source and CH4 mitigating agent in ruminant feed requires further investigations. PMID:26323400

  13. Detection of high molecular weight organic tracers in vegetation smoke samples by high-temperature gas chromatography-mass spectrometry

    SciTech Connect

    Elias, V.O.; Simoneit, B.R.T. ); Pereira, A.S.; Cardoso, J.N. ); Cabral, J.A. )

    1999-07-15

    High-temperature high-resolution gas chromatography (HTGC) is an established technique for the separation of complex mixtures of high molecular weight (HMW) compounds which do not elute when analyzed on conventional GC columns. The combination of this technique with mass spectrometry is not so common and application to aerosols is novel. The HTGC and HTGC-MS analyses of smoke samples taken by particle filtration from combustion of different species of plants provided the characterization of various classes of HMW compounds reported to occur for the first time in emissions from biomass burning. Among these components are a series of wax esters with up to 58 carbon numbers, aliphatic hydrocarbons, triglycerides, long chain methyl ketones, alkanols and a series of triterpenyl fatty acid esters which have been characterized as novel natural products. Long chain fatty acids with more than 32 carbon numbers are not present in the smoke samples analyzed. The HMW compounds in smoke samples from the burning of plants from Amazonia indicate the input of directly volatilized natural products in the original plants during their combustion. However, the major organic compounds extracted from smoke consist of a series of lower molecular weight polar components, which are not natural products but the result of the thermal breakdown of cellulose and lignin. In contrast, the HMW natural products may be suitable tracers for specific sources of vegetation combustion because they are emitted as particles without thermal alternation in the smoke and can thus be related directly to the original plant material.

  14. Purification and chromium-excretory function of low-molecular-weight, chromium-binding substances from dog liver.

    PubMed

    Wada, O; Wu, G Y; Yamamoto, A; Manabe, S; Ono, T

    1983-10-01

    From liver of dogs injected iv with potassium dichromate (38 mg/kg body wt), a low-molecular-weight chromium-binding substance (LMCr) was purified into two subfractions, LMCr I and LMCr II, which differ in physical and chemical properties. LMCr I was identified to be an anionic, organic chromium compound with a molecular weight of 1500. It contained glutamic acid, glycine, and cysteine as the predominant amino acids and firmly bound chromium in a ratio of one chromium(III) to one molecule of LMCr I. LMCr II was isolated in crystalline form and demonstrated to be a water-soluble, inorganic chromium(III) complex consisting of Na2HPO4 . 7H2O and Na2HPO4 . 2H2O. Although its crystallization reduced the chromium content, it had a maximum chromium-binding capacity as much as one chromium per one phosphorus in water. The mixture of LMCr I and LMCr II as approximated to be the natural composition showed a lower acute toxicity as measured by lethality in mice and had higher rates of urinary excretion and renal clearance in rabbits, accompanied by lower rates of renal tubular reabsorption and retention in kidney and liver than potassium dichromate(VI) and chromium(III) chloride. Pretreatment with chromium-free LMCr II remarkably reduced the mortality rates of mice acutely poisoned with chromium chloride. These results indicate that LMCr plays an important role in the detoxification and excretion of chromium in mammals. PMID:6617615

  15. Effect of mahlep on molecular weight distribution of cookie flour gluten proteins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Size Exclusion-High performance Chromatography (SE-HPLC) has been extensively used in molecular weight distribution analysis of wheat proteins. In this study the protein analysis was conducted on different cookie dough blends with different percentages of some ingredients. The mean chromatography ...

  16. Determination of low molecular weight thiols using monobromobimane fluorescent labeling and high-performance liquid chromatography

    NASA Technical Reports Server (NTRS)

    Fahey, Robert C.; Newton, Gerald L.

    1988-01-01

    Methods are described for the preparation and high-performance liquid chromatography (HPLC) analysis of monobromobimane derivatives of low molecular weight thiols in extracts of biological samples. Typical problems encountered in the development and application of these methods are discussed. Analysis of mung bean extract is used as an example.

  17. Exploratory data analysis of the dependencies between skin permeability, molecular weight and log P.

    PubMed

    Kilian, D; Lemmer, H J R; Gerber, M; du Preez, J L; du Plessis, J

    2016-06-01

    Molecular weight and log P remain the most frequently used physicochemical properties in models that predict skin permeability. However, several reports over the past two decades have suggested that predictions made by these models may not be sufficiently accurate. In this study, exploratory data analysis of the probabilistic dependencies between molecular weight, log P and log Kp was performed on a dataset constructed from the combination of several popular datasets. The results suggest that, in general, molecular weight and log P are poorly correlated to log Kp. However, after employing several exploratory data analysis techniques, regions within the dataset of statistically significant dependence were identified. As an example of the applicability of the information extracted from the exploratory data analyses, a multiple linear regression model was constructed, bounded by the ranges of dependence. This model gave reasonable approximations to log Kp values obtained from skin permeability studies of selected non-steroidal ant-inflammatory drugs (NSAIDs) administered from a buffer solution and a lipid-based drug delivery system. A method of testing whether a given drug falls within the regions of statistical dependence was also presented. Knowing the ranges within which molecular weight and log P are statistically related to log Kp can supplement existing methods of screening, risk analysis or early drug development decision making to add confidence to predictions made regarding skin permeability.

  18. Effects of molecular weight on the diffusion coefficient of aquatic dissolved organic matter and humic substances.

    PubMed

    Balch, J; Guéguen, C

    2015-01-01

    In situ measurements of labile metal species using diffusive gradients in thin films (DGT) passive samplers are based on the diffusion rates of individual species. Although most studies have dealt with chemically isolated humic substances, the diffusion of dissolved organic matter (DOM) across the hydrogel is not well understood. In this study, the diffusion coefficient (D) and molecular weight (MW) of 11 aquatic DOM and 4 humic substances (HS) were determined. Natural, unaltered aquatic DOM was capable of diffusing across the diffusive gel membrane with D values ranging from 2.48×10(-6) to 5.31×10(-6) cm(2) s(-1). Humic substances had diffusion coefficient values ranging from 3.48×10(-6) to 6.05×10(-6) cm(2) s(-1), congruent with previous studies. Molecular weight of aquatic DOM and HS samples (∼500-1750 Da) measured using asymmetrical flow field-flow fractionation (AF4) strongly influenced D, with larger molecular weight DOM having lower D values. No noticeable changes in DOM size properties were observed during the diffusion process, suggesting that DOM remains intact following diffusion across the diffusive gel. The influence of molecular weight on DOM mobility will assist in further understanding and development of the DGT technique and the uptake and mobility of contaminants associated with DOM in aquatic environments.

  19. Improved isolation protocol to detect high molecular weight polysaccharide structures of Campylobacter jejuni.

    PubMed

    Kovács, Judit K; Felső, Péter; Emődy, Levente; Schneider, György; Kocsis, Béla

    2014-12-01

    Simple detection of high molecular weight, LPS-like structures of Campylobacter jejuni is still an unsolved problem. A phenol-free extraction method for the detection of HMW polysaccharide was developed without the need for Western blot. This method provides a reliable technique for large-scale screening and comparative characterization study of different isolates.

  20. TOXICOLOGICAL HIGHLIGHT (REDOX REDUX: A CLOSER LOOK AT CONCEPTAL LOW MOLECULAR WEIGHT THIOLS)

    EPA Science Inventory

    Glutathione (GSH) is present as the most abundant low molecular weight thiol (LMWT) in virtually all mitochondria-bearing eucaryotic cells, often at millimolar concentrations (Meister, 1988). Functions of GSH include roles in DNA and protein synthesis, maintenance of cell membra...

  1. Exploratory data analysis of the dependencies between skin permeability, molecular weight and log P.

    PubMed

    Kilian, D; Lemmer, H J R; Gerber, M; du Preez, J L; du Plessis, J

    2016-06-01

    Molecular weight and log P remain the most frequently used physicochemical properties in models that predict skin permeability. However, several reports over the past two decades have suggested that predictions made by these models may not be sufficiently accurate. In this study, exploratory data analysis of the probabilistic dependencies between molecular weight, log P and log Kp was performed on a dataset constructed from the combination of several popular datasets. The results suggest that, in general, molecular weight and log P are poorly correlated to log Kp. However, after employing several exploratory data analysis techniques, regions within the dataset of statistically significant dependence were identified. As an example of the applicability of the information extracted from the exploratory data analyses, a multiple linear regression model was constructed, bounded by the ranges of dependence. This model gave reasonable approximations to log Kp values obtained from skin permeability studies of selected non-steroidal ant-inflammatory drugs (NSAIDs) administered from a buffer solution and a lipid-based drug delivery system. A method of testing whether a given drug falls within the regions of statistical dependence was also presented. Knowing the ranges within which molecular weight and log P are statistically related to log Kp can supplement existing methods of screening, risk analysis or early drug development decision making to add confidence to predictions made regarding skin permeability. PMID:27455549

  2. Methanol-induced chain termination in poly(3-hydroxybutyrate) biopolymers: molecular weight control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A systematic study was performed to demonstrate the impact of methanol (MeOH) on poly(3-hydroxybutyrate) (PHB) synthesis and molecular weight (MW) control. Glycerine (init. conc. = 1.0%; w/v), was used as the primary carbon source in batch-culture fermentations with varying concentrations (0 to 0.85...

  3. Infiltration and Erosion in Soils Treated with Dry PAM of Two Molecular Weights and Phosphogypsum

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil surface application of dissolved linear polyacrylamide (PAM) of high molecular weight (MW) can mitigate seal formation, runoff and erosion, especially when added with a source of electrolytes (e.g., gypsum). Practical difficulties associated with PAM solution application prohibited commercial u...

  4. Effect of chitosan molecular weight on rheological behavious of chitosan modified nanoclay at highly hydrated state

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Effect of chitosan molecular weight (M(cs)) on the rheological properties of chitosan modified clay (CMCs) at highly hydrated state was investigated. With special emphasis on its effect on the thixotropy of CMCs, the structure recovery at rest after underwent a pre-shearing process was further perfo...

  5. Holographic recording medium employing a photoconductive layer and a low molecular weight microcrystalline polymeric layer

    NASA Technical Reports Server (NTRS)

    Gange, Robert Allen (Inventor)

    1977-01-01

    A holographic recording medium comprising a conductive substrate, a photoconductive layer and an electrically alterable layer of a linear, low molecular weight hydrocarbon polymer has improved fatigue resistance. An acrylic barrier layer can be interposed between the photoconductive and electrically alterable layers.

  6. Sedimentation Coefficient, Frictional Coefficient, and Molecular Weight: A Preparative Ultracentrifuge Experiment for the Advanced Undergraduate Laboratory.

    ERIC Educational Resources Information Center

    Halsall, H. B.; Wermeling, J. R.

    1982-01-01

    Describes an experiment using a high-speed preparative centrifuge and calculator to demonstrate effects of the frictional coefficient of a macromolecule on its rate of transport in a force field and to estimate molecular weight of the macromolecule using an empirical relationship. Background information, procedures, and discussion of results are…

  7. Molecular weight distribution and functional group profiles of TEMPO-oxidized lyocell fibers.

    PubMed

    Milanovic, Jovana; Schiehser, Sonja; Milanovic, Predrag; Potthast, Antje; Kostic, Mirjana

    2013-10-15

    The effects of TEMPO-mediated oxidation, performed with NaClO, a catalytic amount of NaBr, and 2,2',6,6'-tetramethylpiperidine-1-oxy radical (TEMPO), were studied on lyocell fibers by means of GPC using multiple detection and group-selective fluorescence labeling according to the CCOA and FDAM methodology. The applied method determines functional group content as a sum parameter, as well as functional group profiles in relation to the molecular weight of the cellulose fibers. Both the CHO and COOH profiles, as well as molecular weight alterations, were analyzed. A significant decrease in the average molecular weight was obtained during the first hour of TEMPO-mediated oxidation, but prolonged oxidation time resulted in no strong additional chain scission. Significant amounts of COOH groups were introduced in the high molecular weight fractions by the oxidation with higher concentrations of NaClO (2.42-9.67 mmol NaClO/g fiber) after modification times of 1h or longer.

  8. Broadening the polyethylene molecular weight distribution by controlling the hydrogen concentration and catalyst feed rates.

    PubMed

    Ali, Emad M; Ali, Mohammad Al-haj

    2010-01-01

    This paper discusses the control of an industrial gas-phase polyethylene reactor to produce a desired molecular weight distribution (MWD) of the polymer. The controller objective is to regulate online the entire molecular weight distribution by either manipulating the hydrogen content inside the reactor or coordinating the feed rates of two different types of catalysts. In this work, the molecular weight distribution is modeled as a function of the reaction kinetics and hydrogen to monomer ratio. Nonlinear model predictive controller (NLMPC) algorithm is used to maintain the desired molecular weight distribution online. The closed-loop simulations indicated the effectiveness of NLMPC to achieve its goal even in the presence of modeling errors. Moreover, the results showed that, altering the hydrogen concentration solely can produce the required polymer quality provided that an efficient mechanism is available to readily alter the hydrogen composition. Alternatively, the desired MWD can also be guaranteed with proper manipulation of the catalyst feed rates while the other process inputs are kept constant.

  9. Deviation from mean-field behavior in a low molecular weight critical polymer blend

    NASA Astrophysics Data System (ADS)

    Hair, D. W.; Hobbie, E. K.; Nakatani, A. I.; Han, C. C.

    1992-06-01

    A deviation from mean-field behavior is observed in the static susceptibility and correlation length measured with small angle neutron scattering as a function of temperature near the phase boundary of a relatively low molecular weight critical polymer mixture. The possibility of a fluctuation influenced crossover from mean-field to nonmean-field behavior is considered.

  10. Polyacrylamide Molecular Weight and Phosphogypsum Effects on Infiltration and Erosion in Semi-Arid Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seal formation at the surface of semi-arid soils during rainstorms reduces soil infiltration rate (IR) and causes runoff and erosion. Surface application of dry anionic polyacrylamide (PAM) with high molecular weight (MW) has been found to be effective in stabilizing soil aggregates, and decreasing ...

  11. Polyacrylamide molecular weight and phosphogypsum effects on infiltration and erosion in semi-arid soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seal formation at the surface of semi-arid soils during rainstorms reduces soil infiltration rate (IR) and causes runoff and erosion. Surface application of dry anionic polyacrylamide (PAM) with high molecular weight (MW) has been found to be effective in stabilizing soil aggregates, and decreasing ...

  12. A global survey of low-molecular weight carbohydrates in lentils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lentils contain a range of low-molecular weight carbohydrates (LMWC); however, those have not been well characterized. The objectives of this study were to (1) determine the concentrations of LMWC in lentils grown in six locations, and (2) identify any genetic and environmental effects on those LMWC...

  13. Microfluidics Meets Dilute Solution Viscometry: An Undergraduate Laboratory to Determine Polymer Molecular Weight Using a Microviscometer

    ERIC Educational Resources Information Center

    Pety, Stephen J.; Lu, Hang; Thio, Yonathan S.

    2011-01-01

    This paper describes a student laboratory experiment to determine the molecular weight of a polymer sample by measuring the viscosity of dilute polymer solutions in a PDMS microfluidic viscometer. Sample data are given for aqueous solutions of poly(ethylene oxide) (PEO). A demonstration of shear thinning behavior using the microviscometer is…

  14. Mental retardation in mucopolysaccharidoses correlates with high molecular weight urinary heparan sulphate derived glucosamine.

    PubMed

    Coppa, G V; Gabrielli, O; Zampini, L; Maccari, F; Mantovani, V; Galeazzi, T; Santoro, L; Padella, L; Marchesiello, R L; Galeotti, F; Volpi, N

    2015-12-01

    Mucopolysaccharidoses (MPS) are characterized by mental retardation constantly present in the severe forms of Hurler (MPS I), Hunter (MPS II) and Sanfilippo (MPS III) diseases. On the contrary, mental retardation is absent in Morquio (MPS IV) and Maroteaux-Lamy (MPS VI) diseases and absent or only minimal in the attenuated forms of MPS I, II and III. Considering that MPS patients affected by mental disease accumulate heparan sulfate (HS) due to specific enzymatic defects, we hypothesized a possible correlation between urinary HS-derived glucosamine (GlcN) accumulated in tissues and excreted in biological fluids and mental retardation. 83 healthy subjects were found to excrete HS in the form of fragments due to the activity of catabolic enzymes that are absent or impaired in MPS patients. On the contrary, urinary HS in 44 patients was observed to be composed of high molecular weight polymer and fragments of various lengths depending on MPS types. On this basis we correlated mental retardation with GlcN belonging to high and low molecular weight HS. We demonstrate a positive relationship between the accumulation of high molecular weight HS and mental retardation in MPS severe compared to attenuated forms. This is also supported by the consideration that accumulation of other GAGs different from HS, as in MPS IV and MPS VI, and low molecular weight HS fragments do not impact on central nervous system disease.

  15. A global survey of low-molecular weight carbohydrates in lentils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lentils contain a range of low-molecular weight carbohydrates (LMWC); however, they have not been well characterized. The objectives