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Sample records for molecular weight tense

  1. 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…

  2. 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).

  3. Past Tense Route Priming

    ERIC Educational Resources Information Center

    Cohen-Shikora, Emily R.; Balota, David A.

    2013-01-01

    The present research examined whether lexical (whole word) or more rule-based (morphological constituent) processes can be locally biased by experimental list context in past tense verb inflection. In Experiment 1, younger and older adults completed a past tense inflection task in which list context was manipulated across blocks containing regular…

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Past Tense Route Priming

    PubMed Central

    Cohen-Shikora, Emily R.; Balota, David A.

    2013-01-01

    The present research examined whether lexical (whole word) or more rule-based (morphological constituent) processes can be locally biased by experimental list context in past tense verb inflection. In Experiment 1, younger and older adults completed a past tense inflection task in which list context was manipulated across blocks containing regular past tense verbs (e.g. REACH-REACHED) or irregular past tense verbs (TEACH-TAUGHT). Critical targets, consisting of half regular and half irregular verbs, were embedded within blocks and participants' inflection response latency and accuracy were assessed. The results yielded a cross-over interaction in response latencies. In the regular context there was a robust regularity effect: regular target verbs were conjugated faster than irregular target verbs. In contrast, in the irregular context, irregular target verbs were conjugated faster than regular target verbs. Experiment 2 used the same targets but in the context of either standard nonwords or nonwords ending in “-ED” to test the possibility of a phonological basis for the effect. The effect of context was eliminated. The results support the notion that distinct processes in past tense verb production can be locally biased by list context and, as shown in Experiment 2, this route priming effect was not due to phonological priming. PMID:23291293

  10. 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).

  11. 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).

  12. Pemphigus Vulgaris with Tense Bullae

    PubMed Central

    Nguyen, Emilie T; Lin, Shinko K; Wu, Jashin J

    2015-01-01

    We report a case of a 51-year-old woman with a history of type II diabetes mellitus and dyslipidemia presenting with pain, swelling, and crusting of the lips. One year after onset of mucosal lesions, she developed an abdominal eruption with several tense vesicles and bullae on an erythematous base. The hematoxylin and eosin stain sample was consistent with a diagnosis of pemphigus vulgaris. The tense bullae of our patient highlight a rare phenotype of pemphigus vulgaris, which fits the mucocutaneous type because of involvement of the oral mucosa, with the exception of the findings of tense bullae. PMID:25663209

  13. Weird past tense forms.

    PubMed

    Xu, F; Pinker, S

    1995-10-01

    It is often assumed that children go through a stage in which they systematically overapply irregular past tense patterns to inappropriate verbs, as in wipe-wope, bring-brang, trick-truck, walk-has walken. Such errors have been interpreted both as reflecting over-use of minor grammatical rules (e.g. 'change i to a'), and as reflecting the operation of a connectionist pattern associator network that superimposes and blends patterns of various degrees of generality. But the actual rate, time course, and nature of these errors have never been documented. We analysed 20,000 past tense and participle usages from nine children in the CHILDES database, looking for overapplications of irregular vowel-change patterns, as in brang, blends, as in branged, productive suffixations of -en, as in walken, gross distortions, as in mail-membled, and double-suffixation, as in walkeded. These errors were collectively quite rare; children made them in about two tenths of one per cent of the opportunities, and with few stable patterns: the errors were not predominantly word-substitutions, did not occur predominantly with irregular stems, showed no consistency across verbs or ages, and showed no clear age trend. Most (though not all) of the errors were based closely on existing irregular verbs; gross distortions never occurred. We suggest that both rule-theories and connectionist theories have tended to overestimate the predominance of such errors. Children master irregular forms quite accurately, presumably because irregular forms are just a special case of the arbitrary sound-meaning pairings that define words, and because children are good at learning words.

  14. 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.

  15. 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.

  16. 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…

  17. 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.

  18. Unexpected molecular weight effect in polymer nanocomposites

    DOE PAGESBeta

    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

  19. The Growth of Tense Productivity

    ERIC Educational Resources Information Center

    Rispoli, Matthew; Hadley, Pamela A.; Holt, Janet K.

    2009-01-01

    Purpose: This study tests empirical predictions of a maturational model for the growth of tense in children younger than 36 months using a type-based productivity measure. Method: Caregiver-child language samples were collected from 20 typically developing children every 3 months from 21 to 33 months of age. Growth in the productivity of tense…

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. An Event Restriction Interval Theory of Tense

    ERIC Educational Resources Information Center

    Beamer, Brandon Robert

    2012-01-01

    This dissertation presents a novel theory of tense and tense-like constructions. It is named after a key theoretical component of the theory, the event restriction interval. In Event Restriction Interval (ERI) Theory, sentences are semantically evaluated relative to an index which contains two key intervals, the evaluation interval and the event…

  10. 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.

  11. 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…

  12. Tense Shifting in Spanish-Speaking English Language Learners

    ERIC Educational Resources Information Center

    Swasey Washington, Patricia; Iglesias, Aquiles

    2015-01-01

    Young monolingual children typically demonstrate frequent tense shifting during narrative development, whereas older children maintain a consistent narration tense. Therefore, inconsistent tense usage in older children could be an indication of overall limited language skills. However, information regarding tense use in bilinguals has been…

  13. 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

  14. 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%.

  15. 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%.

  16. 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.

  17. 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).

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Tense Operators on Spaces of Numerical Events

    NASA Astrophysics Data System (ADS)

    Chajda, Ivan; Länger, Helmut

    2014-10-01

    Spaces of numerical events were introduced for the sake to establish a propositional logic of physical phenomena. Since physical phenomena are variable in time, it is a natural task to develop temporal logic for this description. Hence we adopt the concept of tense operators used in classical propositional logic and in several sorts of non-classical one (e. g. Lukasiewicz many-valued logic, intuitionistic logic etc.). It turns out that the full set of states on a given space of numerical events can serve as a time scale if it is equipped with a suitable relation of time preference. A construction of tense operators is developed and a certain representation is derived. Finally, tense operators on spaces of numerical events whose elements have only the values 0 or 1 are characterized.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. On Learning the Past Tenses of English Verbs.

    ERIC Educational Resources Information Center

    Rumelhart, David E.; McClelland, James L.

    An alternative to the standard "rule based" account of a child's acquisition of the past tense in English is presented in this paper. While the rule based assumption suggests that children typically pass through a three-phase acquisition process in which they first learn past tense by rote, then learn the past tense rule and overregularize, and…

  11. Grammar Learning and Teaching: Time, Tense and Verb

    ERIC Educational Resources Information Center

    Zhuang, Xin

    2010-01-01

    The learning of English tenses and verbs is obviously the major and challenging part of second language learning and acquisition for Chinese students. The paper analyzes the features of simple present tense, simple past tense and verbs in them from the aspect of Sidney Greenbaum and Randolph Quirk's student grammar book as an instructive example.…

  12. 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

  13. 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.

  14. 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

  15. How Verb Tense Affects the Construal of Action: The Simple Past Tense Leads People into an Abstract Mindset

    ERIC Educational Resources Information Center

    Carrera, Pilar; Muñoz, Dolores; Caballero, Amparo; Fernández, Itziar; Aguilar, Pilar; Albarracín, Dolores

    2014-01-01

    Two experiments examined the influence of verb tense on how abstractly people construe action representations. Experiment 1 revealed that written descriptions of several daily events using the simple past tense (vs. simple present tense) resulted in actions and the action's target being seen as less likely and less familiar, respectively. In…

  16. Investigating ESL Students' Academic Performance in Tenses

    ERIC Educational Resources Information Center

    Javed, Muhammad; Ahmad, Atezaz

    2013-01-01

    The present study intends to assess the ESL students' performance in tenses at secondary school level. Grade 10 students were the target population of the study. A sample of 396 students (255 male and 141 female) was selected through convenience sampling technique from the District of Bahawalnagar, Pakistan. A test focusing on five different types…

  17. Morphosyntactic Learning and the Development of Tense

    ERIC Educational Resources Information Center

    Legate, Julie Anne; Yang, Charles

    2007-01-01

    In this article, we propose that the Root Infinitive (RI) phenomenon in child language is best viewed and explained as the interaction between morphological learning and syntactic development. We make the following specific suggestions: The optionality in RI reflects the presence of a grammar such as Chinese which does not manifest tense marking.…

  18. 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.

  19. 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.

  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 PAGESBeta

    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. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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...

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. The Turkish Aorist and Progressive: Present Tense, Future Tense, or What?

    ERIC Educational Resources Information Center

    Kanik, Mehmet

    2015-01-01

    This paper investigates the uses of the aorist and the progressive tenses in spoken Turkish and the extent to which they are used interchangeably. Demo version of Spoken Turkish Corpus was analyzed using EXMARaLDA software. The tokens were divided into the categories of uses. Results indicate that there were a total of 206 tokens of the aorist and…

  16. 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

  17. 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).

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. Children's Judgments of Regular and Irregular Novel Past-Tense Forms: New Data on the English Past-Tense Debate

    ERIC Educational Resources Information Center

    Ambridge, Ben

    2010-01-01

    Is language governed by formal rules or by analogy to stored exemplars? The acquisition of the English past tense has long played a central role in this debate. In the present study, children rated the acceptability of a regular and an irregular past-tense form of each of 40 novel verbs (e.g., "fleeped", "flept") using a 5-point scale. The novel…

  19. 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.

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. [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)

  5. 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

  6. 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.

  7. 10 CFR 1703.102 - Definitions; words denoting number, gender and tense.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Definitions; words denoting number, gender and tense. 1703... § 1703.102 Definitions; words denoting number, gender and tense. Agency record is a record in the... singular; the present tense includes the future tense; and words of one gender include the other gender....

  8. 10 CFR 1703.102 - Definitions; words denoting number, gender and tense.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Definitions; words denoting number, gender and tense. 1703... § 1703.102 Definitions; words denoting number, gender and tense. Agency record is a record in the... singular; the present tense includes the future tense; and words of one gender include the other gender....

  9. 10 CFR 1703.102 - Definitions; words denoting number, gender and tense.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 4 2011-01-01 2011-01-01 false Definitions; words denoting number, gender and tense. 1703... § 1703.102 Definitions; words denoting number, gender and tense. Agency record is a record in the... singular; the present tense includes the future tense; and words of one gender include the other gender....

  10. 10 CFR 1703.102 - Definitions; words denoting number, gender and tense.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 4 2014-01-01 2014-01-01 false Definitions; words denoting number, gender and tense. 1703... § 1703.102 Definitions; words denoting number, gender and tense. Agency record is a record in the... singular; the present tense includes the future tense; and words of one gender include the other gender....

  11. 10 CFR 1703.102 - Definitions; words denoting number, gender and tense.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 4 2013-01-01 2013-01-01 false Definitions; words denoting number, gender and tense. 1703... § 1703.102 Definitions; words denoting number, gender and tense. Agency record is a record in the... singular; the present tense includes the future tense; and words of one gender include the other gender....

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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…

  17. 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.

  18. 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)

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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.

  13. Selecting tense, aspect, and connecting words in language generation

    SciTech Connect

    Gaasterland, T.; Dorr, B.

    1995-12-31

    Generating language that reflects the temporal organization of represented knowledge requires a language generation model that integrates contemporary theories of tense and aspect, temporal representations, and methods to plan text. This paper presents a model that produces complex sentences that reflect temporal relations present in underlying temporal concepts. The main result of this work is the successful application of constrained linguistic theories of tense and aspect to a generator which produces meaningful event combinations and selects appropriate connecting words that relate them.

  14. 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.

  15. [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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Present tense commentary: a qualitative research technique.

    PubMed

    Mitchell, T

    1999-02-01

    This paper describes Present Tense Commentary (PTC) as a technique to gather rich data which satisfies the requirements of a hermeneutic phenomenological approach to research. Using PTC, the informant is encouraged to relieve significant events by conveying them to the researcher as if they are happening now. This process demands greater cognitive ability, greater exposure to the event and more thorough grammatical correctness than in a standard interview situation. The reward, however, is insight for the informant and the researcher into the meaning and understanding, otherwise concealed within the experience. PTC was used as the third phase of data collection in a study involving eight student nurses undertaking the Diploma in Higher Education, Nursing Studies Course (Project 2000). The intention of the study is to illuminate the student's development and their socialization into nursing and to portray the total learning milieu for the students as they describe it. The technique has enabled the students to record experiences in clinical practice, reflect upon them and identify their own development during the course. PTC contrasts with traditional interview methods because it empowers the informant and addresses their agenda and not the researcher's. This paper gives a brief rationale for selecting PTC and describes the process of preparing informants and conducting the technique. The paper focuses upon issues related to philosophical and ethical considerations and recommends that the technique is recognized as a valuable phenomenological tool. PMID:10335198

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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).

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. [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.

  4. 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

  5. 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.

  6. 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...

  7. 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...

  8. 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...

  9. 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…

  10. 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.

  11. 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

  12. 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.

  13. 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).

  14. 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.

  15. 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

  16. 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.

  17. [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.

  18. 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.

  19. Taking times out: Tense logic as a theory of time

    NASA Astrophysics Data System (ADS)

    Pashby, Thomas

    2015-05-01

    Ulrich Meyer's book The Nature of Time uses tense logic to argue for a 'modal' view of time, which replaces substantial times (as in Newton's Absolute Time) with 'ersatz times' constructed using conceptually basic tense operators. He also argues against Bertrand Russell's relationist theory, in which times are classes of events, and against the idea that relativity compels the integration of time and space (called by Meyer the Inseparability Argument). I find fault with each of these negative arguments, as well as with Meyer's purported reconstruction of empty spacetime from tense operators and substantial spatial points. I suggest that Meyer's positive project is best conceived as an elimination of time in the mode of Julian Barbour's The End of Time.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Role of Aspect in Understanding Tense: An Investigation with Adolescents with SLI

    ERIC Educational Resources Information Center

    Stuart, Nichola J.; van der Lely, Heather

    2015-01-01

    Background: Morphosyntax has been well researched in specific language impairment (SLI) and there is general agreement that children with SLI have particular difficulties with tense-marking. Less well researched is the role that aspect plays in the difficulties found in tense-marking, especially as tense and aspect are often confounded in English.…

  8. Production of Verb Tense in Agrammatic Aphasia: A Meta-Analysis and Further Data

    PubMed Central

    Faroqi-Shah, Yasmeen; Friedman, Laura

    2015-01-01

    In a majority of languages, the time of an event is expressed by marking tense on the verb. There is substantial evidence that the production of verb tense in sentences is more severely impaired than other functional categories in persons with agrammatic aphasia. The underlying source of this verb tense impairment is less clear, particularly in terms of the relative contribution of conceptual-semantic and processing demands. This study aimed to provide a more precise characterization of verb tense impairment by examining if there is dissociation within tenses (due to conceptual-semantic differences) and an effect of experimental task (mediated by processing limitations). Two sources of data were used: a meta-analysis of published research (which yielded 143 datasets) and new data from 16 persons with agrammatic aphasia. Tensed verbs were significantly more impaired than neutral (nonfinite) verbs, but there were no consistent differences between past, present, and future tenses. Overall, tense accuracy was mediated by task, such that picture description task was the most challenging, relative to sentence completion, sentence production priming, and grammaticality judgment. An interaction between task and tense revealed a past tense disadvantage for a sentence production priming task. These findings indicate that verb tense impairment is exacerbated by processing demands of the elicitation task and the conceptual-semantic differences between tenses are too subtle to show differential performance in agrammatism. PMID:26457004

  9. Proficiency with Tense and Aspect Concordance: Children with SLI and their Typically Developing Peers

    ERIC Educational Resources Information Center

    Owen, Amanda J.

    2011-01-01

    Children with SLI have difficulty with tense and agreement morphology. This study examined the proficiency of these children and their typically developing peers with the coordination of tense and aspect markers in two-clause sentences. Scenarios designed to elicit past tense were presented to five- to eight-year-old children with SLI (n = 14) and…

  10. 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...

  11. 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.

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. 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.

  3. Tense Use and Move Analysis in Journal Article Abstracts

    ERIC Educational Resources Information Center

    Wang, Shih-ping; Tu, Pin-ning

    2014-01-01

    There has long been a growing interest in journal article (JA) abstract writing, and this pervading interest has boosted the exigency for further research. This current study therefore aims to investigate both the various applications of verb tense and the rhetorical structure within JA abstracts. A corpus of 1,000 JAs was collected from four…

  4. Tense Usage Analysis in Verb Distribution in Brazilian Portuguese.

    ERIC Educational Resources Information Center

    Hoge, Henry W., Comp.

    This section of a four-part research project investigating the syntax of Brazilian Portuguese presents data concerning tense usage in verb distribution. The data are derived from the analysis of selected literary samples from representative and contemporary writers. The selection of authors and tabulation of data are also described. Materials…

  5. Tense and Aspect in Childhood Language Impairment: Contributions from Hungarian

    ERIC Educational Resources Information Center

    Leonard, Laurence B.; Lukacs, Agnes; Kas, Bence

    2012-01-01

    Previous studies of children with language impairment (LI) reveal an insensitivity to aspect that may constitute part of the children's deficit. In this study, we examine aspect as well as tense in Hungarian-speaking children with LI. Twenty-one children with LI, 21 TD children matched for age, and 21 TD children matched for receptive vocabulary…

  6. A Neuroconstructivist Model of Past Tense Development and Processing

    ERIC Educational Resources Information Center

    Westermann, Gert; Ruh, Nicolas

    2012-01-01

    We present a neural network model of learning and processing the English past tense that is based on the notion that experience-dependent cortical development is a core aspect of cognitive development. During learning the model adds and removes units and connections to develop a task-specific final architecture. The model provides an integrated…

  7. Tense-Aspect Processing in Second Language Learners

    ERIC Educational Resources Information Center

    Chan, Ho Leung

    2012-01-01

    This dissertation provides a language processing perspective on the study of second language acquisition (SLA) of tense and aspect. Of special interest are the universal vis-a-vis language-specific dimensions of temporal and aspectual semantics involved. According to the Aspect Hypothesis (AH, e.g. Andersen & Shirai, 1994), the initial…

  8. On the L1 Attrition of the Spanish Present Tense

    ERIC Educational Resources Information Center

    Cuza, Alejandro

    2010-01-01

    This study examines the potential native language (L1) attrition of the ongoing value of the Spanish present tense among long-term Spanish immigrants. Based on the assumption of second-language (L2) transfer and proposals on the permeability of interface-conditioned structures, it is hypothesized that long-term Spanish immigrants will show…

  9. Tense and Agreement Impairment in Ibero-Romance

    ERIC Educational Resources Information Center

    Gavarro, Anna; Martinez-Ferreiro, Silvia

    2007-01-01

    We examine the inflectional productions of seven Catalan, seven Galician, and seven Spanish speaking agrammatic subjects in an elicitation and a sentence repetition task and consider them in the light of the Tree Pruning Hypothesis (TPH). The results show relatively spared subject person/number agreement with the verb and impaired tense marking…

  10. Sequence and System in the Acquisition of Tense and Agreement

    ERIC Educational Resources Information Center

    Rispoli, Matthew; Hadley, Pamela A.; Holt, Janet K.

    2012-01-01

    Purpose: The relatedness of tense morphemes in the language of children younger than 3 years of age is a matter of controversy. Generativist accounts predict that the morphemes will be related, whereas usage-based accounts predict the absence of relationships. This study focused on the increasing productivity of the 5 morphemes in the tense…

  11. 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.

  12. 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.

  13. 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.

  14. A Corpus-Based Study on the Use of Past Tense Auxiliary "Be" in Argumentative Essays of Malaysian ESL Learners

    ERIC Educational Resources Information Center

    Manokaran, Janaki; Ramalingam, Chithra; Adriana, Karen

    2013-01-01

    This research is a corpus-based study of secondary and college ESL Malaysian learner's written work by identifying and classifying the types of errors in the Past Tense Auxiliary "Be". This research studied the past tense auxiliary "be", types of past tense auxiliary "be" errors and frequency of past tense auxiliary…

  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. 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

  6. 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.

  7. 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.

  8. 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…

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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 ...

  14. 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 ...

  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, 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...

  16. 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…

  17. 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.

  18. 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 of this study were to (1) determine the concentrations of LMWC in lentils grown in different environments and (2) identify any genetic and environmental effects on tho...

  19. A low-molecular-weight inhibitor of the neutral proteinase from rat intestinal smooth muscle.

    PubMed Central

    Carney, I T; Curtis, C G; Kay, J K; Birket, N

    1980-01-01

    1. Rat intestinal smooth muscle was shown to contain endogenous inhibitory activity towards the neutral trypsin-like muscle proteinase described previously [Beynon & Kay (1978) Biochem. J. 173, 291--298]. 2. Comtamination of the muscle tissue by mucosal, blood and pancreatic inhibitors was shown to be unlikely. 3. The inhibitory activity was resolved into high- and low-molecular-weight components. 4. The low-molecular-weight component was purified to homogeneity. It has a molecular weight of approx. 9000 and was stable over the pH range 3--11. 5. It inhibited the muscle proteinase competitively (Ki congruent to t microM), but had no effect on any of the other proteinases tested. 6. Leupeptin also inhibited the muscle proteinase competitively (Ki congruent to 0.3 microM), whereas the low-molecular weight proteins gastrin, glucagon and insulin B-chain had very little effect. 7. A role for a weakly binding inhibitor in modulating the influence of the neutral proteinase on intracellular protein degradation is considered. Images Fig. 4. PMID:7396824

  20. The effect of muscular pre-tensing on the sprint start.

    PubMed

    Gutiérrez-Dávilla, Marcos; Dapena, Jesús; Campos, José

    2006-08-01

    Pre-tensed and conventional starts that exert, respectively, large and small forces against the starting blocks in the "set" position (0.186 vs. 0.113 N per newton of body weight) were analyzed. The starts were videotaped, and the horizontal forces exerted on feet and hands were obtained from separate force plates. In the pre-tensed start, the legs received larger forward impulses early in the acceleration (0.18 vs. 0.15 N x s per kilogram of mass in the first 0.05 s), but the hands received larger backward impulses (-0.08 vs. -0.04 N x s x kg(-1)). At the end of the acceleration phase, there was no significant difference in horizontal velocity between the two types of start and only trivial differences in the center of mass positions. The results did not show a clear performance change when the feet were pressed hard against the blocks while waiting for the gun.

  1. 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

  2. Antifungal effects of chitosan with different molecular weights on in vitro development of Rhizopus stolonifer (Ehrenb.:Fr.) Vuill.

    PubMed

    Hernández-Lauzardo, A N; Bautista-Baños, S; Velázquez-Del Valle, M G; Méndez-Montealvo, M G; Sánchez-Rivera, M M; Bello-Pérez, L A

    2008-09-01

    Determination of the molecular weight of three types of chitosan was carried out by HPSEC-RI. The effect of low, medium and high molecular weight chitosan was evaluated on development of three isolates of Rhizopus stolonifer. Image analysis and electronic microscopy observations were done in spores of this fungus. Germination of R. stolonifer in potato dextrose broth with chitosan was also evaluated. Results pointed out that the low molecular weight chitosan was more effective for inhibition of mycelial growth while the high molecular weight chitosan affected spore shape, sporulation and germination. Studies of scanning and transmission electron microscopy revealed numerous and deeper ridge ornamentations of the chitosan-treated spore.

  3. Exposure characterizations of polymer type electron beam resists with various molecular weights for next-generation photomask

    NASA Astrophysics Data System (ADS)

    Takayama, Tomohiro; Asada, Hironori; Kishimura, Yukiko; Hoshino, Ryoichi; Kawata, Atsushi

    2015-10-01

    Higher resolution is eagerly requested to the electron beam resist for the next generation photomask production as well as higher sensitivity. The performance of a polymer resist is mainly characterized by its chemical structure and molecular weight. Positive tone polymer resists with various molecular weights ranging from 60 k to 500 k are synthesized and the molecular weight dependence on exposure characteristics is examined by fabricating line-and-space patterns. The molecular weight dependence of sensitivity for amyl acetate developer is small in the molecular weight range in this study. In a low molecular weight resist, the cross-section profile of the resist pattern becomes rounder and then the disconnections are observed in the 20-nm line-and-space pattern. Although the pattern width change by changing the exposure dose for each resist is quite similar, the exposure dose margin of pattern formation becomes wider with the higher molecular weight. The line width roughness is smaller in a high molecular weight resist than in a low molecular weight resist. The shift amount of the pattern width from the design value for various line-and-space patterns and the dry etching resistance to CF4 plasma are also presented.

  4. 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.

  5. Intermolecular complexation of low-molecular-weight succinoglycans directs solubility enhancement of pindolol.

    PubMed

    Kim, Kyoungtea; Cho, Eunae; Choi, Jae Min; Kim, Hwanhee; Jang, Ahri; Choi, Youngjin; Lee, Im Soon; Yu, Jae-Hyuk; Jung, Seunho

    2014-06-15

    The low-molecular-weight succinoglycans isolated from Sinorhizobium meliloti are repeating octasaccharide units consisting of monomers, dimers, and trimers. Pindolol is a beta-blocker used to treat cardiovascular disorders. We investigated the formation of complexes between pindolol and low-molecular-weight succinoglycan monomers (SGs). Even though SGs have a linear structure, the solubility of pindolol in the presence of SGs was increased up to 7-fold compared with methyl-β-cyclodextrin reported as the best solubilizer of pindolol. Complexation of SGs with pindolol was confirmed by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. Formation constants of complexes were determined from phase solubility diagrams. Conformation of complex was suggested based on a molecular docking study. The present study indicated that formation of pindolol/SGs complexes not only resulted in increased pindolol solubility but also could be useful for improving its clinical application as it did not affect cell viability.

  6. Molecular Weight Changes and Crosslinking Kinetics in Glassy and Elastomeric Thin Films

    NASA Astrophysics Data System (ADS)

    Carbone, Nicholas; Ene, Mada; Lancaster, Jeffrey; Koberstein, Jeffrey

    2010-03-01

    The quantitative and qualitative kinetics of molecular bridging through hydrogen extraction from the tertiary carbon in Polymer backbones are explored through HPLC with MALLS in 300nm films of Polystyrene, Poly(n-butyl acrylate), and other polymers above and below the glass transition temperature. Changes in molecular weight distribution and the appearance of peaks at double and triple the original molecular weight allow the study of the initial stages of network formation. The relative merits of multiple bridging molecules are explored, as well as their effects on kinetics and distribution. When our compounds are mixed into a polymer and exposed to UV radiation, they abstract hydrogen atoms from any chains in proximity, thereby initiating a cascade of free radical reactions that include several mechanisms that can lead to covalent polymer crosslinking.

  7. Effects of High Molecular Weight Species on Shear-Induced Orientation and Crystallization of Isotactic Polypropylene

    SciTech Connect

    Somani,R.; Yang, L.; Hsiao, B.

    2006-01-01

    In situ rheo-SAXS (small-angle X-ray scattering) and rheo-WAXD (wide-angle X-ray diffraction) techniques were used to investigate the role of high molecular weight species on the evolution of oriented microstructure in isotactic polypropylene (iPP) melt under shear flow. The two iPP samples, designated as PP-A and PP-B, respectively, had the same number-average (M{sub n}) but different weight-average (M{sub w}) and Z-average (M{sub z}) molecular weights. Molecular weight distribution (MWD) of PP-A and PP-B was such that for MW<10{sup 5} the MWD curves overlapped; whereas in the high MW tail region, the amount of high molecular weight species was higher in PP-B than PP-A. Both samples were subjected to an identical shear condition (rate=60 s{sup -1}, duration=5 s, T=155 degC). In situ 2D SAXS and WAXD images allowed the tracking of shear-induced oriented structures in the melt. It was found that the shish structures evolved much earlier, and the degree of crystal orientation and oriented crystal fractions were higher in PP-B than PP-A. Moreover, PP-B exhibited faster crystallization kinetics than PP-A. These results, along with the predictions of double reptation models of chain motion and experimental studies of chain conformation dynamics in dilute solutions under flow, suggest the following: When a polymer melt that consists of entangled chains of different lengths is deformed, the chain segments aligned with the flow eigenvector can undergo the abrupt coil-stretch-like transition, while other segments would remain in the coiled state. Since, flow-induced orientation decays much more slowly for long chains than for short chains, oriented high molecular weight species play a prominent role in formation of the stretched sections, where shish originates. Our experimental results are strong evidence of the hypothesis that even a small increase in the concentration of high molecular weight species causes a significant increase in the formation, stability and

  8. In situ analysis of melt-drawing behavior of ultrahigh molecular weight polyethylene films with different molecular weights: roles of entanglements on oriented crystallization.

    PubMed

    Kato, Satomi; Tanaka, Hidekazu; Yamanobe, Takeshi; Uehara, Hiroki

    2015-04-16

    Ultrahigh molecular weight polyethylene (UHMW-PE) films having different molecular weights (MWs) were melt-drawn at 150 °C. The stress-strain curve for higher-MW film exhibits higher stress on the characteristic plateau region and a subsequent steeper increase of stress due to strain hardening. Structural changes during such melt-drawing were analyzed using in situ wide-angle X-ray diffraction measurements. Hexagonal crystallization occurs at the beginning of the plateau region, independent of the sample MW. Once this hexagonal reflection intensity is saturated, it remains constant even at the later stage of draw. In contrast, orthorhombic reflection intensities gradually increase with increasing draw strain. Both of these oriented crystallizations into plateau hexagonal and increasing orthorhombic forms are accelerated with increasing MW. Correspondingly, the higher amount of extended chain crystals (ECCs) was confirmed from morphological observation for the resultant melt-drawn films of the higher-MW sample. Deep entanglements can effectively transmit the applied stress; thus, the oriented amorphous melts induce rapid hexagonal crystallization with disentangling shallow entanglements, which subsequently transforms into orthorhombic form. Such hexagonal crystallization plays the role of a thermodynamic pathway for growing such ECCs, where the stable orthorhombic form gradually accumulates with increasing draw strain.

  9. Simultaneous ion removal and quantitation of low-molecular-weight dietary fiber from high-molecular-weight dietary fiber filtrates using liquid chromatography.

    PubMed

    Post, Brett E; Marshak, Michael R; DeVries, Jonathan W

    2010-01-01

    Dietary fiber and its quantitation in foods have been of significant interest in the nutrition community for over 50 years. A number of AOAC Official Methods of Analysis have been adopted for the analysis of dietary fiber and some of its fractions and components commensurate with the evolving discoveries of dietary fiber nutrition research. Quantitation of low-molecular-weight soluble dietary fiber (LMWSDF) has been difficult due to high solubility in a precipitating solvent mixture of four parts alcohol and one part water. AOAC Method 2001.03 effectively quantitates LWMSDF subsequent to gravimetric removal of high-molecular-weight dietary fiber using LC. However, deionization and concentration of the enzymatic digestate, necessary to assure accurate LC quantitation, requires substantial time and manual labor. A modification to the method and resulting method performance is presented that describes a means of simultaneously deionizing the digestate and quantitating the LMWSDF in a single LC injection, eliminating a number of time-consuming manual preparation steps.

  10. In situ analysis of melt-drawing behavior of ultrahigh molecular weight polyethylene films with different molecular weights: roles of entanglements on oriented crystallization.

    PubMed

    Kato, Satomi; Tanaka, Hidekazu; Yamanobe, Takeshi; Uehara, Hiroki

    2015-04-16

    Ultrahigh molecular weight polyethylene (UHMW-PE) films having different molecular weights (MWs) were melt-drawn at 150 °C. The stress-strain curve for higher-MW film exhibits higher stress on the characteristic plateau region and a subsequent steeper increase of stress due to strain hardening. Structural changes during such melt-drawing were analyzed using in situ wide-angle X-ray diffraction measurements. Hexagonal crystallization occurs at the beginning of the plateau region, independent of the sample MW. Once this hexagonal reflection intensity is saturated, it remains constant even at the later stage of draw. In contrast, orthorhombic reflection intensities gradually increase with increasing draw strain. Both of these oriented crystallizations into plateau hexagonal and increasing orthorhombic forms are accelerated with increasing MW. Correspondingly, the higher amount of extended chain crystals (ECCs) was confirmed from morphological observation for the resultant melt-drawn films of the higher-MW sample. Deep entanglements can effectively transmit the applied stress; thus, the oriented amorphous melts induce rapid hexagonal crystallization with disentangling shallow entanglements, which subsequently transforms into orthorhombic form. Such hexagonal crystallization plays the role of a thermodynamic pathway for growing such ECCs, where the stable orthorhombic form gradually accumulates with increasing draw strain. PMID:25785561

  11. Anticoagulant and antithrombotic activities of low-molecular-weight propylene glycol alginate sodium sulfate (PSS).

    PubMed

    Xin, Meng; Ren, Li; Sun, Yang; Li, Hai-hua; Guan, Hua-Shi; He, Xiao-Xi; Li, Chun-Xia

    2016-05-23

    Propylene glycol alginate sodium sulfate (PSS), a sulfated polysaccharide derivative, has been used as a heparinoid drug to prevent and treat hyperlipidemia and ischemic cardio-cerebrovascular diseases in China for nearly 30 years. To extend the applications of PSS, a series of low-molecular-weight PSSs (named FPs) were prepared by oxidative-reductive depolymerization, and the antithrombotic activities were investigated thoroughly in vitro and in vivo. The bioactivity evaluation demonstrated a positive correlation between the molecular weight and the anticoagulant and antithrombotic activities of FPs. FPs could prolong the APTT and clotting time and reduce platelet aggregation significantly. FPs could also effectively inhibit factor IIa in the presence of AT-III and HC-II. FPs decreased the wet weights and lengths of the thrombus and increased occlusion times in vivo. FP-6k, a PSS fragment with a molecular weight of 6 kDa, is an optimal antithrombotic candidate for further study and showed little chance for hemorrhagic action.

  12. Effects of Molecular Weight on poly( -pentadecalactone) Mechanical and Thermal Properties

    SciTech Connect

    Cai, J.; Liu, C; Cai, M; Zhu, J; Zuo, F; Hsiao, B; Gross, R

    2010-01-01

    A series of poly({omega}-pentadecalactone) (PPDL) samples, synthesized by lipase catalysis, were prepared by systematic variation of reaction time and water content. These samples possessed weight-average molecular weights (M{sub w}), determined by multi-angle laser light scattering (MALLS), from 2.5 x 10{sup 4} to 48.1 x 10{sup 4}. Cold-drawing tensile tests at room temperature of PPDL samples with M{sub W} between 4.5 x 10{sup 4} and 8.1 x 10{sup 4} showed a brittle-to-ductile transition. For PPDL with M{sub W} of 8.1 x 10{sup 4}, inter-fibrillar slippage dominates during deformation until fracture. Increasing M{sub W} above 18.9 x 10{sup 4} resulted in enhanced entanglement network strength and strain-hardening. The high M{sub W} samples also exhibited tough properties with elongation at break about 650% and tensile strength about 60.8 MPa, comparable to linear high density polyethylene (HDPE). Relationships among molecular weight, Young's modulus, stress, strain at yield, melting and crystallization enthalpy (by differential scanning calorimetry, DSC) and crystallinity (from wide-angle X-ray diffraction, WAXD) were correlated for PPDL samples. Similarities and differences of linear HDPE and PPDL molecular weight dependence on their mechanical and thermal properties were also compared.

  13. Molecular weight distribution characterization of hydrophobe-modified hydroxyethyl cellulose by size-exclusion chromatography.

    PubMed

    Li, Yongfu; Meunier, David M; Partain, Emmett M

    2014-09-12

    Size-exclusion chromatography (SEC) of hydrophobe-modified hydroxyethyl cellulose (HmHEC) is challenging because polymer chains are not isolated in solution due to association of hydrophobic groups and hydrophobic interaction with column packing materials. An approach to neutralize these hydrophobic interactions was developed by adding β-cyclodextrin (β-CD) to the aqueous eluent. SEC mass recovery, especially for the higher molecular weight chains, increased with increasing concentration of β-CD in the eluent. A β-CD concentration of 0.75wt% in the eluent was determined to be optimal for the HmHEC polymers studied. These conditions enabled precise determinations of apparent molecular weight distributions exhibiting less than 2% relative standard deviation in the measured weight-average molecular weight (MW) for five injections on three studied samples and showed no significant differences in MW determined on two different days. The developed technology was shown to be very robust for characterizing HmHEC having MW from 500kg/mol to 2000kg/mol, and it can be potentially applied to other hydrophobe-modified polymers.

  14. The potential benefits of low-molecular-weight heparins in cancer patients

    PubMed Central

    2010-01-01

    Cancer patients are at increased risk of venous thromboembolism due to a range of factors directly related to their disease and its treatment. Given the high incidence of post-surgical venous thromboembolism in cancer patients and the poor outcomes associated with its development, thromboprophylaxis is warranted. A number of evidence-based guidelines delineate anticoagulation regimens for venous thromboembolism treatment, primary and secondary prophylaxis, and long-term anticoagulation in cancer patients. However, many give equal weight to several different drugs and do not make specific recommendations regarding duration of therapy. In terms of their efficacy and safety profiles, practicality of use, and cost-effectiveness the low-molecular-weight heparins are at least comparable to, and offer several advantages over, other available antithrombotics in cancer patients. In addition, data are emerging that the antithrombotics, and particularly low-molecular-weight heparins, may exert an antitumor effect which could contribute to improved survival in cancer patients when given for long-term prophylaxis. Such findings reinforce the importance of thromboprophylaxis with low-molecular-weight heparin in cancer patients. PMID:20074349

  15. Anticoagulant and antithrombotic activities of low-molecular-weight propylene glycol alginate sodium sulfate (PSS).

    PubMed

    Xin, Meng; Ren, Li; Sun, Yang; Li, Hai-hua; Guan, Hua-Shi; He, Xiao-Xi; Li, Chun-Xia

    2016-05-23

    Propylene glycol alginate sodium sulfate (PSS), a sulfated polysaccharide derivative, has been used as a heparinoid drug to prevent and treat hyperlipidemia and ischemic cardio-cerebrovascular diseases in China for nearly 30 years. To extend the applications of PSS, a series of low-molecular-weight PSSs (named FPs) were prepared by oxidative-reductive depolymerization, and the antithrombotic activities were investigated thoroughly in vitro and in vivo. The bioactivity evaluation demonstrated a positive correlation between the molecular weight and the anticoagulant and antithrombotic activities of FPs. FPs could prolong the APTT and clotting time and reduce platelet aggregation significantly. FPs could also effectively inhibit factor IIa in the presence of AT-III and HC-II. FPs decreased the wet weights and lengths of the thrombus and increased occlusion times in vivo. FP-6k, a PSS fragment with a molecular weight of 6 kDa, is an optimal antithrombotic candidate for further study and showed little chance for hemorrhagic action. PMID:26974373

  16. Cellular Viscosity in Prokaryotes and Thermal Stability of Low Molecular Weight Biomolecules.

    PubMed

    Cuecas, Alba; Cruces, Jorge; Galisteo-López, Juan F; Peng, Xiaojun; Gonzalez, Juan M

    2016-08-23

    Some low molecular weight biomolecules, i.e., NAD(P)H, are unstable at high temperatures. The use of these biomolecules by thermophilic microorganisms has been scarcely analyzed. Herein, NADH stability has been studied at different temperatures and viscosities. NADH decay increased at increasing temperatures. At increasing viscosities, NADH decay rates decreased. Thus, maintaining relatively high cellular viscosity in cells could result in increased stability of low molecular weight biomolecules (i.e., NADH) at high temperatures, unlike what was previously deduced from studies in diluted water solutions. Cellular viscosity was determined using a fluorescent molecular rotor in various prokaryotes covering the range from 10 to 100°C. Some mesophiles showed the capability of changing cellular viscosity depending on growth temperature. Thermophiles and extreme thermophiles presented a relatively high cellular viscosity, suggesting this strategy as a reasonable mechanism to thrive under these high temperatures. Results substantiate the capability of thermophiles and extreme thermophiles (growth range 50-80°C) to stabilize and use generally considered unstable, universal low molecular weight biomolecules. In addition, this study represents a first report, to our knowledge, on cellular viscosity measurements in prokaryotes and it shows the dependency of prokaryotic cellular viscosity on species and growth temperature.

  17. Cellular Viscosity in Prokaryotes and Thermal Stability of Low Molecular Weight Biomolecules.

    PubMed

    Cuecas, Alba; Cruces, Jorge; Galisteo-López, Juan F; Peng, Xiaojun; Gonzalez, Juan M

    2016-08-23

    Some low molecular weight biomolecules, i.e., NAD(P)H, are unstable at high temperatures. The use of these biomolecules by thermophilic microorganisms has been scarcely analyzed. Herein, NADH stability has been studied at different temperatures and viscosities. NADH decay increased at increasing temperatures. At increasing viscosities, NADH decay rates decreased. Thus, maintaining relatively high cellular viscosity in cells could result in increased stability of low molecular weight biomolecules (i.e., NADH) at high temperatures, unlike what was previously deduced from studies in diluted water solutions. Cellular viscosity was determined using a fluorescent molecular rotor in various prokaryotes covering the range from 10 to 100°C. Some mesophiles showed the capability of changing cellular viscosity depending on growth temperature. Thermophiles and extreme thermophiles presented a relatively high cellular viscosity, suggesting this strategy as a reasonable mechanism to thrive under these high temperatures. Results substantiate the capability of thermophiles and extreme thermophiles (growth range 50-80°C) to stabilize and use generally considered unstable, universal low molecular weight biomolecules. In addition, this study represents a first report, to our knowledge, on cellular viscosity measurements in prokaryotes and it shows the dependency of prokaryotic cellular viscosity on species and growth temperature. PMID:27558730

  18. Effect of thermal treatment on potato starch evidenced by EPR, XRD and molecular weight distribution.

    PubMed

    Bidzińska, Ewa; Michalec, Marek; Pawcenis, Dominika

    2015-12-01

    Effect of heating of the potato starch on damages of its structure was investigated by quantitative electron paramagnetic resonance (EPR) spectroscopy, X-ray diffraction and determination of the molecular weight distribution. The measurements were performed in the temperature range commonly used for starch modifications optimizing properties important for industrial applications. Upon thermal treatment, because of breaking of the polymer chains, diminishing of the average molecular weights occurred, which significantly influences generation of radicals, evidenced by EPR. For the relatively mild conditions, with heating parameters not exceeding temperature 230 °C and time of heating equal to 30 min a moderate changes of both the number of thermally generated radicals and the mean molecular weight of the starch were observed. After more drastic thermal treatment (e.g. 2 h at 230 °C), a rapid increase in the radical amount occurred, which was accompanied by significant reduction of the starch molecular size and crystallinity. Experimentally established threshold values of heating parameters should not be exceeded in order to avoid excessive damages of the starch structure accompanied by the formation of the redundant amount of radicals. This requirement is important for industrial applications, because significant destruction of the starch matrix might annihilate the positive influence of the previously performed intentional starch modification.

  19. Molecular-weight distributions of coal and petroleum asphaltenes from laser desorption/ionization experiments

    SciTech Connect

    Ana R. Hortal; Paola Hurtado; Bruno Martinez-Haya; Oliver C. Mullins

    2007-09-15

    Molecular-weight distributions (MWDs) of asphaltenes extracted from coal and petroleum have been measured in laser desorption/ionization (LDI) mass spectrometric experiments. The dried-droplet and solvent-free sample preparation methods are compared. The coal asphaltenes have a relatively narrow MWD (full width 150 amu) with an average molecular weight of 340 amu. The petroleum asphaltenes display a broader MWD (full width 300 amu) and are heavier on average (680 amu). The LDI spectra also provide evidence for the formation of noncovalent clusters of the two types of asphaltenes during the desorption process. Petroleum and coal asphaltenes exhibit aggregation as do large model polycyclic aromatic hydrocarbons (PAHs) with five or more fused rings also included in the study. Smaller PAHs (pyrene) exhibit less aggregation, especially when alkane-chain substituents are incorporated to the molecular structure. This indicates that asphaltenes possess large PAHs and, according to the relatively small molecular weights observed, that there is a preponderance of asphaltene molecules with only a single fused ring system. The coal asphaltenes present a significantly smaller propensity toward aggregation than their crude oil counterparts. This finding, coupled with the fact that (1) alkanes inhibit aggregation in LDI and (2) petroleum asphaltenes possess much more alkane carbon, indicates that coal asphaltenes have smaller PAHs on average than petroleum asphaltenes. This is further corroborated by the stronger ultraviolet absorbance of the coal asphaltenes at wavelengths shorter than 400 nm. 32 refs., 8 figs.

  20. 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.

  1. 21 CFR 177.1440 - 4,4′-Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true 4,4â²-Isopropylidenediphenol-epichlorohydrin resins... § 177.1440 4,4′-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...

  2. Energy-weighted sum rules and the analysis of vibrational structure in molecular spectra

    NASA Astrophysics Data System (ADS)

    Smith, W. L.

    2015-10-01

    The energy-weighted sum SV = Σn (E‧n - E″m)|<ψ″m|ψ‧n>|2 = <ψ″m|ΔV|ψ″m> for the vibrational potential functions V‧, V″ associated with transitions between two electronic states of diatomic molecular species is investigated and specific formulae are given using Morse functions for V‧ and V″. It is found that these formulae are useful approximations which provide a convenient way to analyse the vibrational structure of real spectra to give estimates of molecular parameters such as the change in internuclear distance accompanying a transition.

  3. Low-molecular-weight inhibitors of NF-κB signalling pathways

    NASA Astrophysics Data System (ADS)

    Dolinnaya, N. G.; Kubareva, Elena A.; Kazanova, E. V.; Zigangirova, N. A.; Naroditsky, B. S.; Gintsburg, A. L.; Oretskaya, Tat'yana S.

    2008-11-01

    The nuclear factor κB (NF-κB) is a transcription factor involved in inducible expression of cellular genes playing a key role in cardiovascular pathologies, carcinogenesis, inflammatory and viral diseases. The review describes the stimuli and processes inducing NF-κB activation and the components of a signalling cascade that could constitute targets for NF-κB inhibition. The molecular action and properties of various low-molecular weight inhibitors aiming to prevent NF-κB activity are summarised.

  4. Priming English Past Tense Verbs: Rules or Statistics?

    ERIC Educational Resources Information Center

    Kielar, A.; Joanisse, Marc F.; Hare, M. L.

    2008-01-01

    A key question in language processing concerns the rule-like nature of many aspects of grammar. Much research on this topic has focused on English past tense morphology, which comprises a regular, rule-like pattern (e.g., bake-baked) and a set of irregular forms that defy a rule-based description (e.g., take-took). Previous studies have used past…

  5. [Chromatographic analysis of low molecular weight fraction of cerebrospinal fluid in children with acute neuroinfections].

    PubMed

    Alekseeva, L A; Shatik, S V; Sorokina, M N; Karasev, V V

    2002-05-01

    Low molecular-weight (oligopeptide) fraction of the cerebrospinal fluid was analyzed by high-performance reversed phase liquid chromatography in 30 children with bacterial and viral neuroinfections. The incidence and height of chromathoraphic peaks in bacterial meningitis depended on the disease etiology, stage, and severity. Qualitative and quantitative composition of low molecular-weight fraction of the liquor varied in patients with viral neuroinfections, depending on the severity of the cerebral parenchyma involvement. Differences in chromatographic profiles in complicated and uneventful course of neuroinfections indicate a possible damaging, protective, or regulatory effect of the liquor peptides. These data focus the attention on the role of oligopeptides in the genesis of neuroinfectious process, significance of search for peptide markers, their further isolation, identification, and development of test systems available for clinical application. PMID:12085699

  6. Role of laccase and low molecular weight metabolites from Trametes versicolor in dye decolorization.

    PubMed

    Moldes, Diego; Fernández-Fernández, María; Sanromán, M Ángeles

    2012-01-01

    The studies regarding decolorization of dyes by laccase may not only inform about the possible application of this enzyme for environmental purposes, but also may provide important information about its reaction mechanism and the influence of several factors that could be involved. In this paper, decolorization of crystal violet and phenol red was carried out with different fractions of extracellular liquids from Trametes versicolor cultures, in order to describe the role of laccase in this reaction. Moreover, the possible role of the low molecular weight metabolites (LMWMs) also produced by the fungus was evaluated. The results confirm the existence of a nonenzymatic decolorization factor, since the nonprotein fraction of the extracellular liquids from cultures of T. versicolor has shown decolorization capability. Several experiments were performed in order to identify the main compounds related to this ability, which are probably low molecular weight peroxide compounds. PMID:22566767

  7. Characteristics of Precipitation-formed Polyethylene Glycol Microgels Are Controlled by Molecular Weight of Reactants

    PubMed Central

    Thompson, Susan; Stukel, Jessica; AlNiemi, Abrar; Willits, Rebecca Kuntz

    2013-01-01

    This work describes the formation of poly(ethylene glycol) (PEG) microgels via a photopolymerized precipitation reaction. Precipitation reactions offer several advantages over traditional microsphere fabrication techniques. Contrary to emulsion, suspension, and dispersion techniques, microgels formed by precipitation are of uniform shape and size, i.e. low polydispersity index, without the use of organic solvents or stabilizers. The mild conditions of the precipitation reaction, customizable properties of the microgels, and low viscosity for injections make them applicable for in vivo purposes. Unlike other fabrication techniques, microgel characteristics can be modified by changing the starting polymer molecular weight. Increasing the starting PEG molecular weight increased microgel diameter and swelling ratio. Further modifications are suggested such as encapsulating molecules during microgel crosslinking. Simple adaptations to the PEG microgel building blocks are explored for future applications of microgels as drug delivery vehicles and tissue engineering scaffolds. PMID:24378988

  8. Characteristics of precipitation-formed polyethylene glycol microgels are controlled by molecular weight of reactants.

    PubMed

    Thompson, Susan; Stukel, Jessica; AlNiemi, Abrar; Willits, Rebecca Kuntz

    2013-12-23

    This work describes the formation of poly(ethylene glycol) (PEG) microgels via a photopolymerized precipitation reaction. Precipitation reactions offer several advantages over traditional microsphere fabrication techniques. Contrary to emulsion, suspension, and dispersion techniques, microgels formed by precipitation are of uniform shape and size, i.e. low polydispersity index, without the use of organic solvents or stabilizers. The mild conditions of the precipitation reaction, customizable properties of the microgels, and low viscosity for injections make them applicable for in vivo purposes. Unlike other fabrication techniques, microgel characteristics can be modified by changing the starting polymer molecular weight. Increasing the starting PEG molecular weight increased microgel diameter and swelling ratio. Further modifications are suggested such as encapsulating molecules during microgel crosslinking. Simple adaptations to the PEG microgel building blocks are explored for future applications of microgels as drug delivery vehicles and tissue engineering scaffolds.

  9. Cytotoxicity of chitosans with different acetylation degrees and molecular weights on bladder carcinoma cells.

    PubMed

    Younes, Islem; Frachet, Véronique; Rinaudo, Marguerite; Jellouli, Kemel; Nasri, Moncef

    2016-03-01

    The purpose of this research was to evaluate the cytotoxicity of chitosans with different degrees of acetylation (DA) and molecular weights (MW), as well as the effect of their positive ionic charges controlled by pH on bladder carcinoma cells (RT112 and RT112cp) using the tetrazolium salt colorimetric (MTT) assay. Our data showed that all chitosan samples were cytotoxic on RT112 and RT112cp cells with a higher cytotoxicity obtained at lower pH. Further, it was found that the toxicity increased with increasing DA. However, no significant difference in cytotoxicity between chitosans with different molecular weights was observed. Annexin V-FITC staining test was then used to study and quantify the induction of apoptosis. Data shows that chitosans induce apoptosis of RT112 and RT112cp cells with the same dependence with DA.

  10. HPMA-oligolysine copolymers for gene delivery: optimization of peptide length and polymer molecular weight.

    PubMed

    Johnson, Russell N; Chu, David S H; Shi, Julie; Schellinger, Joan G; Carlson, Peter M; Pun, Suzie H

    2011-10-30

    Polycations are one of the most frequently used classes of materials for non-viral gene transfer in vivo. Several studies have demonstrated a sensitive relationship between polymer structure and delivery activity. In this work, we used reverse addition-fragmentation chain transfer (RAFT) polymerization to build a panel of N-(2-hydroxypropyl)methacrylamide (HPMA)-oligolysine copolymers with varying peptide length and polymer molecular weight. The panel was screened for optimal DNA-binding, colloidal stability in salt, high transfection efficiency, and low cytotoxicity. Increasing polyplex stability in PBS correlated with increasing polymer molecular weight and decreasing peptide length. Copolymers containing K(5) and K(10) oligocations transfected cultured cells with significantly higher efficiencies than copolymers of K(15). Four HPMA-oligolysine copolymers were identified that met the desired criteria. Polyplexes formed with these copolymers demonstrated both salt stability and transfection efficiencies on-par with poly(ethylenimine) PEI in cultured cells.

  11. Participation of Low Molecular Weight Electron Carriers in Oxidative Protein Folding

    PubMed Central

    Margittai, Éva; Csala, Miklós; Mandl, József; Bánhegyi, Gábor

    2009-01-01

    Oxidative protein folding is mediated by a proteinaceous electron relay system, in which the concerted action of protein disulfide isomerase and Ero1 delivers the electrons from thiol groups to the final acceptor. Oxygen appears to be the final oxidant in aerobic living organisms, although the existence of alternative electron acceptors, e.g. fumarate or nitrate, cannot be excluded. Whilst the protein components of the system are well-known, less attention has been turned to the role of low molecular weight electron carriers in the process. The function of ascorbate, tocopherol and vitamin K has been raised recently. In vitro and in vivo evidence suggests that these redox-active compounds can contribute to the functioning of oxidative folding. This review focuses on the participation of small molecular weight redox compounds in oxidative protein folding. PMID:19399252

  12. Effect of radiation on the structure of ultrahigh molecular weight polyethylene

    NASA Astrophysics Data System (ADS)

    Kamel, Ihab; Finegold, Leonard

    Radiation sterilization of ultrahigh molecular weight polyethylene (UHMW-PE) was recently found to cause changes in crystallinity, contradicting earlier observations on linear polyethylene of lower molecular weight. In this study, UHMW-PE (Hercules 1900) was gamma-irradiated up to 21 Mrad. Changes in melting and crystallization temperatures, enthalpies of melting and of crystallization, determined by differential scanning calorimetry, are reported. In particular, the temperature at the onset of crystallization provided a clearer view of the radiation damage to the polymer chains. A mechanism based on chain scission is proposed to explain the observed increase in crystallinity in agreement with recent findings. The crystallization temperature may be useful as an indicator of radiation and/or other damage to the UHMW-PE.

  13. Determination of molecular weight distributions of large water soluble macromolecules using dynamic light scattering

    SciTech Connect

    Mettille, M.J.; Hester, R.D.

    1988-05-01

    Characterization of polymer molecular weight is an extremely important aspect of polymer research, and a vast number of analytical techniques has been used to determine molecular weights. One method is dynamic light scattering (DLS). DLS is also referred to as photon correlation spectroscopy (PCS), quasi-elastic light scattering (QLS), and may other appellations. The phenomenon that gives rise to the DLS technique was first observed in the early 1930's. In the mid 1950's, measurement techniques similar to modern dynamic light scattering were developed. Two major technical developments have greatly enhanced the use of DLS. The first was the development of the laser. This provided a light source with very high intensity at a single frequency. Also, major advances in digital electronics have allowed better data acquisition and faster data analysis than were previously available.

  14. [Chromatographic analysis of low molecular weight fraction of cerebrospinal fluid in children with acute neuroinfections].

    PubMed

    Alekseeva, L A; Shatik, S V; Sorokina, M N; Karasev, V V

    2002-05-01

    Low molecular-weight (oligopeptide) fraction of the cerebrospinal fluid was analyzed by high-performance reversed phase liquid chromatography in 30 children with bacterial and viral neuroinfections. The incidence and height of chromathoraphic peaks in bacterial meningitis depended on the disease etiology, stage, and severity. Qualitative and quantitative composition of low molecular-weight fraction of the liquor varied in patients with viral neuroinfections, depending on the severity of the cerebral parenchyma involvement. Differences in chromatographic profiles in complicated and uneventful course of neuroinfections indicate a possible damaging, protective, or regulatory effect of the liquor peptides. These data focus the attention on the role of oligopeptides in the genesis of neuroinfectious process, significance of search for peptide markers, their further isolation, identification, and development of test systems available for clinical application.

  15. Friction and wear of polyethylene oxide polymer having a range of molecular weights

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1978-01-01

    Sliding friction and wear experiments were conducted at light loads (25 to 250 g) with various molecular weights of the polyethylene oxide polymer sliding on itself and iron. Results of the experimental investigation indicate that: (1) the coefficient of friction for the polymer decreases with increasing molecular weight; (2) friction coefficient is higher for the polymer sliding on itself than it is for the polymer sliding on iron; (3) at sufficiently high loads localized surface melting occurs and the friction coefficient is the same for the polymer sliding on itself and iron; (4) fracture cracks develop in the sliding wear track at higher but not lower sliding velocities, reflecting a strain rate sensitivity to crack initiation, and (5) the friction coefficient for the polymer sliding on iron increases with the formation of a polymer film on the iron surface.

  16. 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.

  17. Role of laccase and low molecular weight metabolites from Trametes versicolor in dye decolorization.

    PubMed

    Moldes, Diego; Fernández-Fernández, María; Sanromán, M Ángeles

    2012-01-01

    The studies regarding decolorization of dyes by laccase may not only inform about the possible application of this enzyme for environmental purposes, but also may provide important information about its reaction mechanism and the influence of several factors that could be involved. In this paper, decolorization of crystal violet and phenol red was carried out with different fractions of extracellular liquids from Trametes versicolor cultures, in order to describe the role of laccase in this reaction. Moreover, the possible role of the low molecular weight metabolites (LMWMs) also produced by the fungus was evaluated. The results confirm the existence of a nonenzymatic decolorization factor, since the nonprotein fraction of the extracellular liquids from cultures of T. versicolor has shown decolorization capability. Several experiments were performed in order to identify the main compounds related to this ability, which are probably low molecular weight peroxide compounds.

  18. 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.

  19. Simulated dynamic response of a multi-stage compressor with variable molecular weight flow medium

    NASA Technical Reports Server (NTRS)

    Babcock, Dale A.

    1995-01-01

    A mathematical model of a multi-stage compressor with variable molecular weight flow medium is derived. The modeled system consists of a five stage, six cylinder, double acting, piston type compressor. Each stage is followed by a water cooled heat exchanger which serves to transfer the heat of compression from the gas. A high molecular weight gas (CFC-12) mixed with air in varying proportions is introduced to the suction of the compressor. Condensation of the heavy gas may occur in the upper stage heat exchangers. The state equations for the system are integrated using the Advanced Continuous Simulation Language (ACSL) for determining the system's dynamic and steady state characteristics under varying operating conditions.

  20. 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

  1. [Benign salivary gland-type tumors of the bronchus: expression of high molecular weight cytokeratins].

    PubMed

    Méjean-Lebreton, Frédérique; Barnoud, Raphaëlle; de la Roche, Eric; Devouassoux-Shisheboran, Mojgan

    2006-02-01

    Primary lung tumors showing features of salivary gland-type neoplasms are extremely rare, and their immunohistochemical profile has been seldom studied. We report two cases of bronchial pleomorphic and mucous gland adenomas and study the expression of markers such as TTF-1 and high molecular weight keratins in these tumors. Both tumors were endobronchial. The pleomorphic adenoma also had a well-circumscribed parenchymal component, with a biphasic morphology composed of epithelial and myoepithelial cells in a background of myxoid and hyaline stroma. The mucous gland adenoma displayed papillary and dilated glandular structures. In both cases, epithelial cells showed strong and diffuse cytoplasmic staining with high molecular weight cytokeratins (cytokeratin 5/6 and keratin 903), and lacked TTF-1 expression. This immunoprofile provides useful clues for the histogenesis of pulmonary benign salivary gland-type adenomas and helps in distinguishing them from primary adenocarcinomas in small biopsy specimens.

  2. 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.

  3. Molecular weight of polydisperse icodextrin effects its oncotic contribution to water transport.

    PubMed

    Nishimura, Kohei; Kamiya, Yohei; Miyamoto, Keiichi; Nomura, Shinsuke; Horiuchi, Takashi

    2008-01-01

    Icodextrin, a mixture of polysaccharides of alpha-(1 --> 4) polyglucopyranose having 10% branched chains, is clinically available as a D-glucose substitute for peritoneal dialysis (PD). Due to the high intraperitoneal retention time of this glucose polymer (GP), water transport from the vessels to the peritoneal cavity is prolonged even in PD patients with high peritoneal permeability. The purpose of this study was to elucidate why 7.5% icodextrin solution has such a broad distribution of molecular weights. A gel permeation chromatography study indicated that the average molecular weight was about 18.0 kDa in terms of number average (Mn) and 31.3 kDa in terms of weight average (Mw), respectively, resulting in a polydispersity index (Mn/Mw) of 1.74. Five fractions of GP having Mn values of 41.3, 19.3, 8.3, 3.8, and 2.1 kDa, respectively, produced 0.24, 0.49, 0.50, 0.08, and 0.03 mOsmol/kg H2O of colloid osmotic pressure. Water transport through a membrane having a molecular cutoff of 15 kDa was simulated using the mass transfer coefficient and reflection coefficient for each fraction. Fractions with Mn values of 19.3 and 8.3 kDa contributed to water transport dominantly (approximately 76%), while only 18%, 5%, and 3% of total water removal was contributed by fractions with Mn values of 41.3, 3.8 and 2.1 kDa, respectively. As a result of enzymatic degradation for 10 h by 2, 10, or 20 U/l alpha-amylase, a decrease in the high molecular weight zone (40-60 kDa) and a rise in the low molecular weight zone (1-2 kDa) were seen with few change in the distribution profile between 4 and 30 kDa. These results suggested that fractions in the molecular range between 8.3 and 19.3 kDa, where the distribution profile was less influenced by enzymatic degradation, preferably contributed to water transport.

  4. Molecular weight characterization of high molecular weight dextran with multiangle light scattering in on-line and off-line mode.

    PubMed

    Wang, Jinfeng; Wang, Jing

    2015-07-01

    This work reports the molecular weight (MW) analysis of high MW dextran using multiangle light scattering (MALS) in both chromatography and automated batch measurement mode. The results show that the chromatographic columns alter the high MW native dextran and cause underestimation of the MW as a consequence. Alternatively, a batch MALS measurement (without columns) provides more accurate MW values. The batch MALS measurement was automated with the incorporation of an automatic sample dilution and injection device. This automation reduces the sample preparation time and minimizes concentration errors introduced by manual sample dilution. To the best of our knowledge, this is the first study using an automated batch MALS in the analysis of high MW dextran.

  5. A novel series of glucagon receptor antagonists with reduced molecular weight and lipophilicity.

    PubMed

    Filipski, Kevin J; Bian, Jianwei; Ebner, David C; Lee, Esther C Y; Li, Jian-Cheng; Sammons, Matthew F; Wright, Stephen W; Stevens, Benjamin D; Didiuk, Mary T; Tu, Meihua; Perreault, Christian; Brown, Janice; Atkinson, Karen; Tan, Beijing; Salatto, Christopher T; Litchfield, John; Pfefferkorn, Jeffrey A; Guzman-Perez, Angel

    2012-01-01

    A novel series of glucagon receptor antagonists has been discovered. These pyrazole ethers and aminopyrazoles have lower molecular weight and increased polarity such that the molecules fall into better drug-like property space. This work has culminated in compounds 44 and 50 that were shown to have good pharmacokinetic attributes in dog, in contrast to rats, in which clearance was high; and compound 49, which demonstrated a dose-dependent reduction in glucose excursion in a rat glucagon challenge experiment.

  6. Effect of cryogrinding on the molecular weight of samples of polyisobutylene

    SciTech Connect

    Waters, P.F.; Hadermann, A.F.; Trippe, J.C.

    1983-01-01

    Three different molecular weight samples of isobutylene are ground and dissolved in isooctane. Also, unground samples are dissolved for comparison. The viscosity and height-at-break in ductless siphon are measured. Small quantities of macromolecules dissolved in fuels impede the aerosolization of the fuels (the purpose of antimisting additives). Mathematical formulas for the intrinsic viscosity and height-at-break are derived from the data.

  7. 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.

  8. Low molecular weight Neutral Boron Dipyrromethene (Bodipy) dyads for fluorescence-based neural imaging

    NASA Astrophysics Data System (ADS)

    Bai, Dan; Benniston, Andrew C.; Clift, Sophie; Baisch, Ulrich; Steyn, Jannetta; Everitt, Nicola; Andras, Peter

    2014-05-01

    The neutral low molecular weight julolidine-based borondipyrromethene (Bodipy) dyads JULBD and MJULBD were used for fast voltage-sensitive dye imaging of neurons in the crab stomatogastric ganglion. The fluorescence modulation of the dyads mirrors alterations in the membrane potential of the imaged neurons. The toxicity of the dyes towards the neurons is related to their structure in that methyl groups at the 3,5 positions results in reduced toxic effects.

  9. New External Calibration Curves (ECCs) for the Estimation of Molecular Weights in Various Common NMR Solvents.

    PubMed

    Bachmann, Sebastian; Neufeld, Roman; Dzemski, Martin; Stalke, Dietmar

    2016-06-13

    New external calibration curves (ECCs) for the estimation of aggregation states of small molecules in solution by DOSY NMR spectroscopy for a range of different common NMR solvents ([D6 ]DMSO, C6 D12 , C6 D6 , CDCl3 , and CD2 Cl2 ) are introduced and applied. ECCs are of avail to estimate molecular weights (MWs) from diffusion coefficients of previously unknown aggregates. This enables a straightforward and elaborate examination of (de)aggregation phenomena in solution.

  10. Characterization of Rhizobial Isolates of Phaseolus vulgaris by Staircase Electrophoresis of Low-Molecular-Weight RNA

    PubMed Central

    Velázquez, Encarna; Martínez-Romero, Esperanza; Rodríguez-Navarro, Dulce Nombre; Trujillo, Martha E.; Daza, Antonio; Mateos, Pedro F.; Martínez-Molina, Eustoquio; van Berkum, Peter

    2001-01-01

    Low-molecular-weight (LMW) RNA molecules were analyzed to characterize rhizobial isolates that nodulate the common bean growing in Spain. Since LMW RNA profiles, determined by staircase electrophoresis, varied across the rhizobial species nodulating beans, we demonstrated that bean isolates recovered from Spanish soils presumptively could be characterized as Rhizobium etli, Rhizobium gallicum, Rhizobium giardinii, Rhizobium leguminosarum bv. viciae and bv. trifolii, and Sinorhizobium fredii. PMID:11157280

  11. pH response and molecular recognition in a low molecular weight peptide hydrogel.

    PubMed

    Lange, Stefanie C; Unsleber, Jan; Drücker, Patrick; Galla, Hans-Joachim; Waller, Mark P; Ravoo, Bart Jan

    2015-01-14

    In this article we report the preparation and characterization of a peptide-based hydrogel, which possesses characteristic rheological properties, is pH responsive and can be functionalized at its thiol function. The tripeptide N-(fluorenyl-9-methoxycarbonyl)-L-Cys(acetamidomethyl)-L-His-L-Cys-OH 1 forms stable supramolecular aggregates in water leading to hydrogels above 1.5 wt%. Rheological analysis of the hydrogel revealed visco-elastic and shear thinning properties of samples containing 1.5 wt% of peptide 1. The hydrogel reversibly responds to pH changes. Below and above pH 6, electrostatic repulsion of the peptide results in a weakening of the three-dimensional gel network. Based on atomic force microscopy, small angle X-ray scattering and molecular dynamics simulations, it is proposed that the peptide assembles into nanostructures that tend to entangle at higher concentrations in water. The development of functional materials based on the peptide assemblies was possible via thiol-ene-click chemistry of the free thiol function at the C-terminal cysteine unit. As a proof of concept, the functionalization with adamantyl units to give 1-Ad was shown by molecular recognition of β-cyclodextrin vesicles. These vesicles were used as supramolecular cross-linkers of the assemblies of peptide 1 mixed with peptide 1-Ad leading to gel networks at a reduced peptide concentration.

  12. A preliminary comparison of verb tense production in Spanish speakers with expressive restrictions.

    PubMed

    Centeno, José G; Anderson, Raquel T

    2011-10-01

    Spoken verb tense use in three groups of Spanish speakers with expressive limitations, namely, children with specific language impairment, bilingual children with first language (L1) (Spanish) attrition and adults with agrammatism, was compared in order to examine the possible impact of conversational tense frequency on expressive production. Based on the notion that frequent language forms in typical discourse are preferred in contexts of expressive restrictions, we predicted that tenses with high spoken occurrence will be favoured by individuals in our expressively limited groups. The incidence of tense use by the participants was assessed in oral narratives and/or a sentence repetition task. Consistent with our prediction, the most frequent verb tenses in conversational Spanish--the present, followed by the preterite--were preferred by the participants thus supporting the proposal that a socio-cognitive factor linking discursive frequency to verb retrieval may be operating in tense preference in situations of expressive stress. PMID:21728828

  13. Bilingual children's acquisition of the past tense: a usage-based approach.

    PubMed

    Paradis, Johanne; Nicoladis, Elena; Crago, Martha; Genesee, Fred

    2011-06-01

    Bilingual and monolingual children's (mean age=4;10) elicited production of the past tense in both English and French was examined in order to test predictions from Usage-Based theory regarding the sensitivity of children's acquisition rates to input factors such as variation in exposure time and the type/token frequency of morphosyntactic structures. Both bilingual and monolingual children were less accurate with irregular than regular past tense forms in both languages. Bilingual children, as a group, were less accurate than monolinguals with the English regular and irregular past tense, and with the French irregular past tense, but not with the French regular past tense. However, bilingual children were as accurate as monolinguals with the past tense in their language of greater exposure, except for English irregular verbs. It is argued that these results support the view that children's acquisition rates are sensitive to input factors, but with some qualifications.

  14. A preliminary comparison of verb tense production in Spanish speakers with expressive restrictions.

    PubMed

    Centeno, José G; Anderson, Raquel T

    2011-10-01

    Spoken verb tense use in three groups of Spanish speakers with expressive limitations, namely, children with specific language impairment, bilingual children with first language (L1) (Spanish) attrition and adults with agrammatism, was compared in order to examine the possible impact of conversational tense frequency on expressive production. Based on the notion that frequent language forms in typical discourse are preferred in contexts of expressive restrictions, we predicted that tenses with high spoken occurrence will be favoured by individuals in our expressively limited groups. The incidence of tense use by the participants was assessed in oral narratives and/or a sentence repetition task. Consistent with our prediction, the most frequent verb tenses in conversational Spanish--the present, followed by the preterite--were preferred by the participants thus supporting the proposal that a socio-cognitive factor linking discursive frequency to verb retrieval may be operating in tense preference in situations of expressive stress.

  15. Production of specific-molecular-weight hyaluronan by metabolically engineered Bacillus subtilis 168.

    PubMed

    Jin, Peng; Kang, Zhen; Yuan, Panhong; Du, Guocheng; Chen, Jian

    2016-05-01

    Low-molecular-weight hyaluronan (LMW-HA) has attracted much attention because of its many potential applications. Here, we efficiently produced specific LMW-HAs from sucrose in Bacillus subtilis. By coexpressing the identified committed genes (tuaD, gtaB, glmU, glmM, and glmS) and downregulating the glycolytic pathway, HA production was significantly increased from 1.01gL(-1) to 3.16gL(-1), with a molecular weight range of 1.40×10(6)-1.83×10(6)Da. When leech hyaluronidase was actively expressed after N-terminal engineering (1.62×10(6)UmL(-1)), the production of HA was substantially increased from 5.96gL(-1) to 19.38gL(-1). The level of hyaluronidase was rationally regulated with a ribosome-binding site engineering strategy, allowing the production of LMW-HAs with a molecular weight range of 2.20×10(3)-1.42×10(6)Da. Our results confirm that this strategy for the controllable expression of hyaluronidase, together with the optimization of the HA synthetic pathway, effectively produces specific LMW-HAs, and could also be used to produce other LMW polysaccharides. PMID:26851304

  16. Detonation-Synthesis Nanodiamonds in Compositions of Ultrahigh-Molecular-Weight Polyethylene

    NASA Astrophysics Data System (ADS)

    Dubkova, V. I.; Korzhenevskii, A. P.; Krut‧ko, N. P.; Komarevich, V. G.; Kul‧bistkaya, L. V.

    2016-07-01

    A study has been made of the influence of an ultradisperse carbonaceous product, i.e., detonation-synthesis nanodiamonds, on the structure and properties of nanocomposites based on ultrahigh-molecular-weight polyethylene using electron microscopy and acoustic, electrophysical, thermomechanical, and x-ray phase analysis methods It has been shown that a diamond blend is a structurally active filler of ultrahigh-molecular-weight polyethylene, which changes the crystalline and supermolecular structure of the polymer during its melt crystallization under the conditions of uniaxial plastic deformation. The developed polymer nanocomposites based on ultrahigh-molecular-weight polyethylene, which contain 0.5-0.25 wt.% of the diamond blend, possess higher than average indices of hardness, modulus of elasticity, and electrical conductivity manifested to a larger extent in the frequency range 1-10 kHz, a low friction factor (0.15-0.18), and high resistance to wear under dry-friction conditions (the wear rate is 10-4-10-5 mg/m).

  17. Stable, concentrated solutions of high molecular weight polyaniline and articles therefrom

    DOEpatents

    Mattes, Benjamin R.; Wang, Hsing-Lin

    2000-01-01

    Stable, concentrated solutions of high molecular weight polyaniline. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15-30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (>15% (w/w)) of high molecular weight ((M.sub.w)>120,000, and (M.sub.n)>30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefor. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

  18. Stable, concentrated solutions of high molecular weight polyaniline and articles therefrom

    DOEpatents

    Mattes, Benjamin R.; Wang, Hsing-Lin

    1999-11-09

    Stable, concentrated solutions of high molecular weight polyaniline. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15-30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (between 15% and 30% (w/w)) of high molecular weight ((M.sub.w)>120,000, and (M.sub.n)>30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefor. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

  19. Methanol-induced chain termination in poly(3-hydroxybutyrate) biopolymers: molecular weight control.

    PubMed

    Ashby, Richard D; Solaiman, Daniel K Y; Strahan, Gary D; Levine, Alex C; Nomura, Christopher T

    2015-03-01

    A systematic study was performed to demonstrate the impact of methanol (MeOH) on poly(3-hydroxybutyrate) (PHB) synthesis and molecular weight (MW). Glycerine was used as the primary carbon source with varying concentrations of MeOH. Methanol retarded but did not completely inhibit growth and PHB production in Pseudomonas oleovorans. Proton NMR analysis revealed that the PHB polymers were end-capped with methoxy chemical groups causing MW reductions. The MW decreases were contingent upon the initial MeOH media concentration and the duration of the fermentations. The largest impact occurred at an initial MeOH concentration of 0.10% (w/v) where the number average molecular weights (Mn) decreased by 39%, 55%, and 72% in the 48, 72 and 96 h cultures, respectively. Diffusion ordered NMR spectroscopy revealed a diffusivity (D) increase in the smaller molecular weight polymers with the PHB synthesized in the presence of 0.85% MeOH (72 h post-inoculation) having a D value of 0.66×10(-10) m2/s. Diffusivity increases indicate a reduction in hydrodynamic radii (Rhz) consistent with shorter chain-lengths. Crude glycerine from the biodiesel production process has been used as an inexpensive fermentation feedstock for polyhydroxyalkanoate (PHA) synthesis but its composition is facility-dependent. This information will be vital to tailor PHA properties to specific applications. PMID:25542165

  20. The Effect of Molecular Weight on the Composite Properties of Cured Phenylethynyl Terminated Imide Oligomers

    NASA Technical Reports Server (NTRS)

    Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.

    1997-01-01

    As part of a program to develop high temperature/high performance structural resins for aeronautical applications, imide oligomers containing terminal phenylethynyl groups with calculated number average molecular weights of 1250, 2500 and 5000 g/mol were prepared, characterized, and evaluated as adhesives and composite matrix resins. The goal of this work was to develop resin systems that are processable using conventional processing equipment into void free composites that exhibit high mechanical properties with long term high temperature durability, and are not affected by exposure to common aircraft fluids. The imide oligomers containing terminal phenylethynyl groups were fabricated into titanium adhesive specimens and IM-7 carbon fiber laminates under 0.1 - 1.4 MPa for 1 hr at 350-371 C. The lower molecular weight oligomers exhibited higher cured Tg, better processability, and better retention of mechanical properties at elevated temperature without significantly sacrificing toughness or damage tolerance than the higher molecular weight oligomer. The neat resin, adhesive and composite properties of the cured polymers will be presented.

  1. 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.

  2. Phase Behavior of Weakly Ordered Diblock Copolymers in the High Molecular Weight Limit

    NASA Astrophysics Data System (ADS)

    Patel, Amish; Balsara, Nitash

    2004-03-01

    Poly(tert-butylstyrene-block-polydiene) (TBS-D) diblock copolymers with molecular weights ranging from 10 kg/mol to 500 kg/mol have been synthesized. The dienes studied thus far are 1-4 polyisoprene and 1-2 polybutadiene. The Flory-Huggins interaction parameters (kii) between TBS and D chains are negative at room temperature. Thus, the mean field theory of polymer blends predicts that TBS-D diblock copolymers must be disordered, regardless of their molecular weight. With increasing temperature, kii increases, and we thus expect the formation of ordered phases. The nature of these transitions can be also predicted by mean-field theory. We are conducting small-angle X-ray scattering and optical birefringence experiments on the TBS-D block copolymers to test the applicability of the mean-field theory. This enables a test of the mean-field theory of block copolymers over an unprecedented range of molecular weights. The results of these tests will be presented at the meeting.

  3. Graphene Nanocomposites with High Molecular Weight Poly(ε-caprolactone) Grafts: Controlled Synthesis and Accelerated Crystallization

    DOE PAGESBeta

    Mondal, Titash; Ashkar, Rana; Butler, Paul; Bhowmick, Anil K.; Krishnamoorti, Ramanan

    2016-02-08

    Grafting of high molecular weight polymers to graphitic nanoplatelets is a critical step toward the development of high performance graphene nanocomposites. However, designing such a grafting route has remained a major impediment. Herein, we report a "grafting to" synthetic pathway by which high molecular weight polymer, poly(e-caprolactone) (PCL), is tethered, at high grafting density, to highly anisotropic graphitic nanoplatelets. The efficacy of this tethering route and the resultant structural arrangements within the composite are confirmed by neutron and X-ray scattering measurements in the melt and solution phase. In the semicrystalline state, Xray analysis indicates that chain tethering onto the graphiticmore » nanoplatelets results in conformational changes of the polymer chains, which enhance the nucleation process and aid formation of PCL crystallites. This is corroborated by the superior thermal properties of the composite, manifested in accelerated crystallization kinetics and a significant increase in the thermal degradation temperature. Lastly, in principle, this synthesis route can be extended to a variety of high molecular weight polymers, which can open new avenues to solution-based processing of graphitic nanomaterials and the fabrication of complex 3D patterned graphitic nanocomposites.« less

  4. 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

  5. The effect of the molecular weight of additive on the properties of antimisting fuels

    SciTech Connect

    Hadermann, A.F.; Trippe, J.C.; Waters, P.F.

    1983-09-01

    Antimisting aircraft fuels, when ignited, do not produce the roaring fireball which often accompanies aircraft crashes. This result is attributable to the suppression of the aerosolization of the fuel by added macromolecules which alter the structure of the droplets of fuel emanating from rent fuel tanks after the crash. The first studies of the antimisting effect of macromolecules on aviation fuel were carried out in Great Britain in 1968. In that early work it was established that there was a qualitative relationship between the suppression of the atomization of the fuel and the molecular weight of the additive above a certain critical concentration; the latter being inverse to the molecular weight of the additive. Subsequent investigations have demonstrated a dependence of the antimisting effectiveness of polyisobutylene in diesel fuel on the viscosity average molecular weight to a power exceeding 2, and in jet-A fuel to the 2..cap alpha.. + 1 power, where ..cap alpha.. is the exponent in the Mark-Houwink equation. In their study Chao et al, were able to demonstrate a strong correlation between the extent of antimisting effectiveness and flammability reduction with the maximum ductless siphon height supported by the solution. They introduced the ductless siphon to the study of antimisting fuels as a measure of the elongational viscosity impaired by the macromolecules to the fuel.

  6. Production of specific-molecular-weight hyaluronan by metabolically engineered Bacillus subtilis 168.

    PubMed

    Jin, Peng; Kang, Zhen; Yuan, Panhong; Du, Guocheng; Chen, Jian

    2016-05-01

    Low-molecular-weight hyaluronan (LMW-HA) has attracted much attention because of its many potential applications. Here, we efficiently produced specific LMW-HAs from sucrose in Bacillus subtilis. By coexpressing the identified committed genes (tuaD, gtaB, glmU, glmM, and glmS) and downregulating the glycolytic pathway, HA production was significantly increased from 1.01gL(-1) to 3.16gL(-1), with a molecular weight range of 1.40×10(6)-1.83×10(6)Da. When leech hyaluronidase was actively expressed after N-terminal engineering (1.62×10(6)UmL(-1)), the production of HA was substantially increased from 5.96gL(-1) to 19.38gL(-1). The level of hyaluronidase was rationally regulated with a ribosome-binding site engineering strategy, allowing the production of LMW-HAs with a molecular weight range of 2.20×10(3)-1.42×10(6)Da. Our results confirm that this strategy for the controllable expression of hyaluronidase, together with the optimization of the HA synthetic pathway, effectively produces specific LMW-HAs, and could also be used to produce other LMW polysaccharides.

  7. Synthesis of High-Molecular-Weight Polyhydroxyalkanoates by Marine Photosynthetic Purple Bacteria.

    PubMed

    Higuchi-Takeuchi, Mieko; Morisaki, Kumiko; Toyooka, Kiminori; Numata, Keiji

    2016-01-01

    Polyhydroxyalkanoate (PHA) is a biopolyester/bioplastic that is produced by a variety of microorganisms to store carbon and increase reducing redox potential. Photosynthetic bacteria convert carbon dioxide into organic compounds using light energy and are known to accumulate PHA. We analyzed PHAs synthesized by 3 purple sulfur bacteria and 9 purple non-sulfur bacteria strains. These 12 purple bacteria were cultured in nitrogen-limited medium containing acetate and/or sodium bicarbonate as carbon sources. PHA production in the purple sulfur bacteria was induced by nitrogen-limited conditions. Purple non-sulfur bacteria accumulated PHA even under normal growth conditions, and PHA production in 3 strains was enhanced by nitrogen-limited conditions. Gel permeation chromatography analysis revealed that 5 photosynthetic purple bacteria synthesized high-molecular-weight PHAs, which are useful for industrial applications. Quantitative reverse transcription polymerase chain reaction analysis revealed that mRNA levels of phaC and PhaZ genes were low under nitrogen-limited conditions, resulting in production of high-molecular-weight PHAs. We conclude that all 12 tested strains are able to synthesize PHA to some degree, and we identify 5 photosynthetic purple bacteria that accumulate high-molecular-weight PHA molecules. Furthermore, the photosynthetic purple bacteria synthesized PHA when they were cultured in seawater supplemented with acetate. The photosynthetic purple bacteria strains characterized in this study should be useful as host microorganisms for large-scale PHA production utilizing abundant marine resources and carbon dioxide.

  8. Synthesis of High-Molecular-Weight Polyhydroxyalkanoates by Marine Photosynthetic Purple Bacteria

    PubMed Central

    Higuchi-Takeuchi, Mieko; Morisaki, Kumiko; Toyooka, Kiminori; Numata, Keiji

    2016-01-01

    Polyhydroxyalkanoate (PHA) is a biopolyester/bioplastic that is produced by a variety of microorganisms to store carbon and increase reducing redox potential. Photosynthetic bacteria convert carbon dioxide into organic compounds using light energy and are known to accumulate PHA. We analyzed PHAs synthesized by 3 purple sulfur bacteria and 9 purple non-sulfur bacteria strains. These 12 purple bacteria were cultured in nitrogen-limited medium containing acetate and/or sodium bicarbonate as carbon sources. PHA production in the purple sulfur bacteria was induced by nitrogen-limited conditions. Purple non-sulfur bacteria accumulated PHA even under normal growth conditions, and PHA production in 3 strains was enhanced by nitrogen-limited conditions. Gel permeation chromatography analysis revealed that 5 photosynthetic purple bacteria synthesized high-molecular-weight PHAs, which are useful for industrial applications. Quantitative reverse transcription polymerase chain reaction analysis revealed that mRNA levels of phaC and PhaZ genes were low under nitrogen-limited conditions, resulting in production of high-molecular-weight PHAs. We conclude that all 12 tested strains are able to synthesize PHA to some degree, and we identify 5 photosynthetic purple bacteria that accumulate high-molecular-weight PHA molecules. Furthermore, the photosynthetic purple bacteria synthesized PHA when they were cultured in seawater supplemented with acetate. The photosynthetic purple bacteria strains characterized in this study should be useful as host microorganisms for large-scale PHA production utilizing abundant marine resources and carbon dioxide. PMID:27513570

  9. Molecular weight-dependent genetic information transfer with disulfide-linked polyethylenimine-based nonviral vectors.

    PubMed

    Parhiz, Hamideh; Hashemi, Maryam; Hatefi, Arash; Shier, Wayne Thomas; Farzad, Sara Amel; Ramezani, Mohammad

    2013-07-01

    One strategy for improving gene vector properties of polyethylenimine is to facilitate individual transfection mechanism steps. This study investigates (i) improving transfection efficiency by attaching peptide nuclear localization signals (nuclear localization signals: SV40 large T antigen nuclear localization signal or C-terminus of histone H1) to polyethylenimine (10 kDa) and (ii) using disulfide linkages, which are expected to be stable during polyplex formation, but cleaved inside cells giving improved gene release. Nuclear localization signal-containing polyplexes exhibited low cytotoxicity, whereas transfection efficiency with high molecular weight plasmid DNA increased up to 3.6 times that of underivatized polyethylenimine in Neuro2A cells at higher molar ratio of polyethylenimine-nitrogen to DNA-phosphate (N/P) ratios. However, with luciferase-specific low molecular weight small interfering RNA in Neuro2A/EGFPLuc cells, nuclear localization signal-containing polyplexes with disulfide linkages caused substantial cytotoxicity at N/P ratios >15 and no consistent significant reduction in luciferase expression. Possible explanations for molecular weight-dependent differences in genetic information transfer by polyplexes containing disulfide-linked nuclear localization signals are discussed.

  10. High Sulfation and a High Molecular Weight Are Important for Anti-hepcidin Activity of Heparin.

    PubMed

    Asperti, Michela; Naggi, Annamaria; Esposito, Emiliano; Ruzzenenti, Paola; Di Somma, Margherita; Gryzik, Magdalena; Arosio, Paolo; Poli, Maura

    2015-01-01

    Heparins are efficient inhibitors of hepcidin expression even in vivo, where they induce an increase of systemic iron availability. Heparins seem to act by interfering with BMP6 signaling pathways that control the expression of liver hepcidin, causing the suppression of SMAD1/5/8 phosphorylation. The anti-hepcidin activity persists also when the heparin anticoagulant property is abolished or reduced by chemical reactions of oxidation/reduction (glycol-split, Gs-Heparins) or by high sulfation (SS-Heparins), but the structural characteristics needed to optimize this inhibitory activity have not been studied in detail. To this aim we analyzed three different heparins (Mucosal Heparin, the Glycol split RO-82, the partially desulfated glycol-split RO-68 and the oversulfated SSLMWH) and separated them in fractions of molecular weight in the range 4-16 kD. Since the distribution of the negative charges in heparins contributes to the activity, we produced 2-O- and 6-O-desulfated heparins. These derivatives were analyzed for the capacity to inhibit hepcidin expression in hepatic HepG2 cells and in mice. The two approaches produced consistent results and showed that the anti-hepcidin activity strongly decreases with molecular weight below 7 kD, with high N-acetylation and after 2-O and 6-O desulfation. The high sulfation and high molecular weight properties for efficient anti-hepcidin activity suggest that heparin is involved in multiple binding sites. PMID:26955355

  11. Determination of dextrose equivalent value and number average molecular weight of maltodextrin by osmometry.

    PubMed

    Rong, Y; Sillick, M; Gregson, C M

    2009-01-01

    Dextrose equivalent (DE) value is the most common parameter used to characterize the molecular weight of maltodextrins. Its theoretical value is inversely proportional to number average molecular weight (M(n)), providing a theoretical basis for correlations with physical properties important to food manufacturing, such as: hygroscopicity, the glass transition temperature, and colligative properties. The use of freezing point osmometry to measure DE and M(n) was assessed. Measurements were made on a homologous series of malto-oligomers as well as a variety of commercially available maltodextrin products with DE values ranging from 5 to 18. Results on malto-oligomer samples confirmed that freezing point osmometry provided a linear response with number average molecular weight. However, noncarbohydrate species in some commercial maltodextrin products were found to be in high enough concentration to interfere appreciably with DE measurement. Energy dispersive spectroscopy showed that sodium and chloride were the major ions present in most commercial samples. Osmolality was successfully corrected using conductivity measurements to estimate ion concentrations. The conductivity correction factor appeared to be dependent on the concentration of maltodextrin. Equations were developed to calculate corrected values of DE and M(n) based on measurements of osmolality, conductivity, and maltodextrin concentration. This study builds upon previously reported results through the identification of the major interfering ions and provides an osmolality correction factor that successfully accounts for the influence of maltodextrin concentration on the conductivity measurement. The resulting technique was found to be rapid, robust, and required no reagents.

  12. 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.

  13. Molecular weight distribution of phosphorus fraction of aquatic dissolved organic matter.

    PubMed

    Ged, Evan C; Boyer, Treavor H

    2013-05-01

    This study characterized dissolved organic phosphorus (DOP) that is discharged from the Everglades Agricultural Area as part of the larger pool of aquatic dissolved organic matter (DOM). Whole water samples collected at the Everglades stormwater treat area 1 West (STA-1 W) were fractionated using a batch ultrafiltration method to separate organic compounds based on apparent molecular weight (AMW). Each AMW fraction of DOM was characterized for phosphorus, carbon, nitrogen, UV absorbance, and fluorescence. The DOP content of the Everglades water matrix was characteristically variable constituting 4-56% of total phosphorus (TP) and demonstrated no correlation with dissolved organic carbon (DOC). Measured values for DOP exceeded 14μgL(-1) in four out of five sampling dates making phosphorus load reductions problematic for the stormwater treatment areas (STAs), which target inorganic phosphorus and have a goal of 10μgL(-1) as TP. The molecular weight distributions revealed 40% of DOP is high molecular weight, aromatic-rich DOM. The results of this research are expected to be of interest to environmental chemists, environmental engineers, and water resources managers because DOP presents a major obstacle to achieving TP levels <10μgL(-1).

  14. Synthesis of High-Molecular-Weight Polyhydroxyalkanoates by Marine Photosynthetic Purple Bacteria.

    PubMed

    Higuchi-Takeuchi, Mieko; Morisaki, Kumiko; Toyooka, Kiminori; Numata, Keiji

    2016-01-01

    Polyhydroxyalkanoate (PHA) is a biopolyester/bioplastic that is produced by a variety of microorganisms to store carbon and increase reducing redox potential. Photosynthetic bacteria convert carbon dioxide into organic compounds using light energy and are known to accumulate PHA. We analyzed PHAs synthesized by 3 purple sulfur bacteria and 9 purple non-sulfur bacteria strains. These 12 purple bacteria were cultured in nitrogen-limited medium containing acetate and/or sodium bicarbonate as carbon sources. PHA production in the purple sulfur bacteria was induced by nitrogen-limited conditions. Purple non-sulfur bacteria accumulated PHA even under normal growth conditions, and PHA production in 3 strains was enhanced by nitrogen-limited conditions. Gel permeation chromatography analysis revealed that 5 photosynthetic purple bacteria synthesized high-molecular-weight PHAs, which are useful for industrial applications. Quantitative reverse transcription polymerase chain reaction analysis revealed that mRNA levels of phaC and PhaZ genes were low under nitrogen-limited conditions, resulting in production of high-molecular-weight PHAs. We conclude that all 12 tested strains are able to synthesize PHA to some degree, and we identify 5 photosynthetic purple bacteria that accumulate high-molecular-weight PHA molecules. Furthermore, the photosynthetic purple bacteria synthesized PHA when they were cultured in seawater supplemented with acetate. The photosynthetic purple bacteria strains characterized in this study should be useful as host microorganisms for large-scale PHA production utilizing abundant marine resources and carbon dioxide. PMID:27513570

  15. Post-translational modification and stability of low molecular weight cyclin E.

    PubMed

    Mull, B B; Cox, J; Bui, T; Keyomarsi, K

    2009-09-01

    Our laboratory has previously described the presence of five tumor-specific low molecular weight isoforms of cyclin E in both tumor cell lines and breast cancer patient biopsies. We have also shown that one of these low forms arises from an alternate start site, whereas the other four appear as two sets of doublets following cleavage through an elastase-like enzyme. However, the origin of both sets of doublets was unknown. Here, we demonstrate that the larger isoform of each doublet is the result of phosphorylation at a key degradation site. Through site-directed mutagenesis of different phosphorylation sites within the cyclin E protein, we discovered that phosphorylation of threonine 395 is responsible for generating the larger isoform of each doublet. Because phosphorylation of threonine 395 has been linked to the proteasome-mediated degradation of full length cyclin E, we examined the stability of T395A phospho-mutants in both non-tumorigenic mammary epithelial cells and tumor cells. The results revealed that the low molecular weight isoforms appear to be stable in both a tumor cell line and a non-tumor forming cell line regardless of the presence of this critical phosphorylation site. The stability of low molecular weight cyclin E may have implications for both tumorigenesis and treatment of tumors expressing them.

  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.

  17. Synthesis, characterization and in situ intestinal absorption of different molecular weight scutellarin-PEG conjugates.

    PubMed

    Zhou, Qingsong; Jiang, Xuehua; Li, Kejia; Fan, Xingxing

    2006-08-01

    Highly water soluble esters of scutellarin with different molecular weight polyethylene glycol (PEG) were synthesized. The physicochemical properties, the stabilities under different conditions and the in situ intestinal absorption of the conjugates in rats were investigated. By PEG modification, greatly increased water solubility and a desirable partition coefficient were obtained. These compounds act as prodrugs i.e. breakdown occurrs in a predictable fashion: in vitro, the t1/2 of them in PBS buffer at pH 7.4 was above 12 h (37 degrees C), while in plasma a more rapid breakdown was observed (t1/2 1.5-3 h). PEGylation could enhance the absorption of scutellarin in rat intestine, and scutellarin, its PEG conjugates are absorbed through intestine mainly via passive transport. When the molecular weight of PEG increased from 200 to 1000 Da, the absorption of the conjugates decreased accordingly. The range of PEG molecular weight used for the PEGylation of scutellarin was about 400-1000 Da based on considerations of the yield, the stability and the absorption.

  18. Systematic Analysis of Polymer Molecular Weight Influence on the Organic Photovoltaic Performance.

    PubMed

    Katsouras, Athanasios; Gasparini, Nicola; Koulogiannis, Chrysanthos; Spanos, Michael; Ameri, Tayebeh; Brabec, Christoph J; Chochos, Christos L; Avgeropoulos, Apostolos

    2015-10-01

    The molecular weight of an electron donor-conjugated polymer is as essential as other well-known parameters in the chemical structure of the polymer, such as length and the nature of any side groups (alkyl chains) positioned on the polymeric backbone, as well as their placement, relative strength, the ratio of the donor and acceptor moieties in the backbone of donor-acceptor (D-A)-conjugated polymers, and the arrangement of their energy levels for organic photovoltaic performance. Finding the "optimal" molecular weight for a specific conjugated polymer is an important aspect for the development of novel photovoltaic polymers. Therefore, it is evident that the chemistry of functional conjugated polymers faces major challenges and materials have to adopt a broad range of specifications in order to be established for high photovoltaic performance. In this review, the approaches followed for enhancing the molecular weight of electron-donor polymers are presented in detail, as well as how this influences the optoelectronic properties, charge transport properties, structural conformation, morphology, and the photovoltaic performance of the active layer.

  19. Effect of molecular weight on the physical properties of poly(ethylene brassylate) homopolymers.

    PubMed

    Fernández, Jorge; Amestoy, Hegoi; Sardon, Haritz; Aguirre, Miren; Varga, Aitor Larrañaga; Sarasua, Jose-Ramon

    2016-12-01

    Poly(ethylene brassylate) (PEB) is a biodegradable polyester that nowadays is of particular interest owing to its poly(ε-caprolactone)-like properties (with a Tg at -30°C and a Tm at 70°C) and the low-cost of its monomer. However, it is not simple to achieve high molar masses with conventional catalysts. In this work, high molar mass PEBs, characterized by SEC-MALS, were successfully synthesized using triphenyl bismuth (Ph3Bi) as catalyst. Then, with the aim of evaluating the impact of the molecular weight on the physical properties, several PEBs ranging from 27 to 247kgmol(-1) were prepared. It was demonstrated that above a Mw of 90Kgmol(-1), PEB behaved in a constant manner. PEBs with lower molecular weight (<46Kgmol(-1)) showed lower values of Tg (~(-35°C)) and presented a melting peak that was split into three or four different peaks while their crystallites started to melt earlier (at ~30°C). In addition, these PEBs were more sensitive to thermal degradation (two additional stages of degradation were observed) and, what is more important, were found to be prone to brittle fracture. As the Mw rose, the PEB samples became more ductile and those PEBs with a molecular weight above 90Kgmol(-1) possessed deformation at break values higher than 800%, secant modulus in the 296-324 range and ultimate tensile strength of >20MPa.

  20. 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.

  1. Effect of molecular weight on the physical properties of poly(ethylene brassylate) homopolymers.

    PubMed

    Fernández, Jorge; Amestoy, Hegoi; Sardon, Haritz; Aguirre, Miren; Varga, Aitor Larrañaga; Sarasua, Jose-Ramon

    2016-12-01

    Poly(ethylene brassylate) (PEB) is a biodegradable polyester that nowadays is of particular interest owing to its poly(ε-caprolactone)-like properties (with a Tg at -30°C and a Tm at 70°C) and the low-cost of its monomer. However, it is not simple to achieve high molar masses with conventional catalysts. In this work, high molar mass PEBs, characterized by SEC-MALS, were successfully synthesized using triphenyl bismuth (Ph3Bi) as catalyst. Then, with the aim of evaluating the impact of the molecular weight on the physical properties, several PEBs ranging from 27 to 247kgmol(-1) were prepared. It was demonstrated that above a Mw of 90Kgmol(-1), PEB behaved in a constant manner. PEBs with lower molecular weight (<46Kgmol(-1)) showed lower values of Tg (~(-35°C)) and presented a melting peak that was split into three or four different peaks while their crystallites started to melt earlier (at ~30°C). In addition, these PEBs were more sensitive to thermal degradation (two additional stages of degradation were observed) and, what is more important, were found to be prone to brittle fracture. As the Mw rose, the PEB samples became more ductile and those PEBs with a molecular weight above 90Kgmol(-1) possessed deformation at break values higher than 800%, secant modulus in the 296-324 range and ultimate tensile strength of >20MPa. PMID:27517665

  2. Stable, concentrated solutions of high molecular weight polyaniline and articles therefrom

    SciTech Connect

    Mattes, B.R.; Wang, H.L.

    1999-11-09

    Stable, concentrated solutions of high molecular weight polyaniline are disclosed. In order to process high quality fibers and other articles possessing good mechanical properties, it is known that solution concentrations of the chosen polymer should be in the range from 15--30% (w/w). Moreover, it is desirable to use the highest molecular weight consistent with the solubility properties of the polymer. However, such solutions are inherently unstable, forming gels before processing can be achieved. The present invention describes the addition gel inhibitors (GIs) to the polymer solution, thereby permitting high concentrations (between 15% and 30% (w/w)) of high molecular weight ((M(w)){gt}120,000, and (M(n)){gt}30,000) emeraldine base (EB) polyaniline to be dissolved. Secondary amines have been used for this purpose in concentrations which are small compared to those which might otherwise be used in a cosolvent role therefore. The resulting solutions are useful for generating excellent fibers, films, coatings and other objects, since the solutions are stable for significant time periods, and the GIs are present in too small concentrations to cause polymer deterioration. It is demonstrated that the GIs found to be useful do not act as cosolvents, and that gelation times of the solutions are directly proportional to the concentration of GI. In particular, there is a preferred concentration of GI, which if exceeded causes structural and electrical conductivity degradation of resulting articles. Heating of the solutions significantly improves solubility.

  3. Properties and Microstructural Characteristic of Kaolin Geopolymer Ceramics with Addition of Ultra High Molecular Weight Polyethylene

    NASA Astrophysics Data System (ADS)

    Ahmad, Romisuhani; Bakri Abdullah, Mohd Mustafa Al; Hussin, Kamarudin; Sandu, Andrei Victor; Binhussain, Mohammed; Ain Jaya, Nur

    2016-06-01

    In this paper, the mechanical properties and microstructure of kaolin geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene were studied. Inorganic polymers based on alumina and silica polysialate units were synthesized at room temperature from kaolin and sodium silicate in a highly alkaline medium, followed by curing and drying at 80 °C. Alkaline activator was formed by mixing the 12 M NaOH solution with sodium silicate at a ratio of 0.24. Addition of Ultra High Molecular Weight Polyethylene to the kaolin geopolymer are fabricated with Ultra High Molecular Weight Polyethylene content of 2, 4, 6 and 8 (wt. %) by using powder metallurgy method. The samples were heated at 1200 °C and the strength and morphological were tested. It was found that the flexural strength for the kaolin geopolymer ceramics with addition of UHMWPE were improved and generally increased with the increasing of UHMWPE loading. The result revealed that the optimum flexural strength was obtained at UHMWPE loading of 4 wt. % (92.1 MPa) and the flexural strength started to decrease. Microstructural analysis showed the samples appeared to have more number of pores and connected of pores increased with the increasing of UHMWPE content.

  4. Melt rheology and molecular weight degradation of amylopectin during multiple pass extrusion of starch

    SciTech Connect

    Willett, J.L.; Millard, M.M.; Jasberg, B.K.

    1996-12-31

    The degradation of starch during extrusion and the role of specific mechanical energy (SME) in this process have been widely studied for single pass extrusion, Multiple extrusion histories are not uncommon in the plastics industry, but little if any has been reported on their effects on starch. Native waxy maize starch (app. 98% amylopectin) was initially converted to a thermoplastic by twin screw extrusion. This extrudate was equilibrated to either 18% or 23% moisture content, and subsequently re-extruded in a single screw extruder (3:1 compression screw) at 110{degrees}C or 130{degrees}C. Melt viscosity data were calculated using the output-pressure data from the second pass. The melts exhibited shear thinning behavior; the power law index increased with temperature, and slightly with moisture content. Molecular weights of selected second-pass extrudates, as well as the native starch and the first-pass extrudate, were measured by light scattering in dimethyl sulfoxide/water. The initial extrusion pass reduced the molecular weight from 300 million to 50 million. Molecular weight reductions in the second pass increased with increasing SME. A first order expression was shown to fit the MW-SME data with a correlation coefficient of 0.91. Implications of the degradation on extrusion processing of starch and the use of single screw extruders for rheological characterization will be discussed.

  5. 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

  6. A Study on How to Teach Tense to Chinese Korean Language Learners

    ERIC Educational Resources Information Center

    Lee, Sun-Min

    2011-01-01

    Presently it is hard to find a thesis which have presented the teaching plan on how to teach the tense to Chinese learners on the spot of learning and even the textbooks in classes cover the subject of tense only in the medium or high level. The author considers that the learners' mistakes on the subject of tense are apt to be fossilized, if they…

  7. Mass spectrometric techniques for characterizing low-molecular-weight resins used as paint varnishes.

    PubMed

    Bonaduce, I; Colombini, M P; Degano, I; Di Girolamo, F; La Nasa, J; Modugno, F; Orsini, S

    2013-01-01

    The molecular structure of three low-molecular-weight resins used as paint varnishes has been characterized by use of an approach based on three different mass spectrometric techniques. We investigated the ketone resin MS2A, the aldehyde resin Laropal A81, and the hydrocarbon resin Regalrez 1094, now commonly used in restoration. To date, the molecular structures of these resins have not been completely elucidated. To improve current knowledge of the chemical composition of these materials, information obtained by gas chromatography-mass spectrometry (GC/MS), pyrolysis-gas chromatography-mass spectrometry (Py/GC/MS), and electrospray ionization mass spectrometry (ESI-Q-ToF) was combined. Analysis, in solution, of the whole polymeric fraction of the resins by flow-injection ESI-Q-ToF, and of the non-polymeric fraction by GC-MS, enabled us to identify previously unreported features of the polymer structures. In addition, the Py-GC/MS profiles that we obtained will help to enhance the databases currently available in the literature. The proposed approach can be extended to other low-molecular-weight resins used as varnishes in conservation.

  8. High-molecular weight protein toxins of marine invertebrates and their elaborate modes of action.

    PubMed

    Butzke, Daniel; Luch, Andreas

    2010-01-01

    High-molecular weight protein toxins significantly contribute to envenomations by certain marine invertebrates, e.g., jellyfish and fire corals. Toxic proteins frequently evolved from enzymes meant to be employed primarily for digestive purposes. The cellular intermediates produced by such enzymatic activity, e.g., reactive oxygen species or lysophospholipids, rapidly and effectively mediate cell death by disrupting cellular integrity. Membrane integrity may also be disrupted by pore-forming toxins that do not exert inherent enzymatic activity. When targeted to specific pharmacologically relevant sites in tissues or cells of the natural enemy or prey, toxic enzymes or pore-forming toxins even may provoke fast and severe systemic reactions. Since toxin-encoding genes constitute "hot spots" of molecular evolution, continuous variation and acquirement of new pharmacological properties are guaranteed. This also makes individual properties and specificities of complex proteinaceous venoms highly diverse and inconstant. In the present chapter we portray high-molecular weight constituents of venoms present in box jellyfish, sea anemones, sea hares, fire corals and the crown-of-thorns starfish. The focus lies on the latest achievements in the attempt to elucidate their molecular modes of action. PMID:20358685

  9. The high and low molecular weight forms of hyaluronan have distinct effects on CD44 clustering.

    PubMed

    Yang, Cuixia; Cao, Manlin; Liu, Hua; He, Yiqing; Xu, Jing; Du, Yan; Liu, Yiwen; Wang, Wenjuan; Cui, Lian; Hu, Jiajie; Gao, Feng

    2012-12-14

    CD44 is a major cell surface receptor for the glycosaminoglycan hyaluronan (HA). Native high molecular weight hyaluronan (nHA) and oligosaccharides of hyaluronan (oHA) provoke distinct biological effects upon binding to CD44. Despite the importance of such interactions, however, the feature of binding with CD44 at the cell surface and the molecular basis for functional distinction between different sizes of HA is still unclear. In this study we investigated the effects of high and low molecular weight hyaluronan on CD44 clustering. For the first time, we provided direct evidence for a strong relationship between HA size and CD44 clustering in vivo. In CD44-transfected COS-7 cells, we showed that exogenous nHA stimulated CD44 clustering, which was disrupted by oHA. Moreover, naturally expressed CD44 was distributed into clusters due to abundantly expressed nHA in HK-2 cells (human renal proximal tubule cells) and BT549 cells (human breast cancer cell line) without exogenous stimulation. Our results suggest that native HA binding to CD44 selectively induces CD44 clustering, which could be inhibited by oHA. Finally, we demonstrated that HA regulates cell adhesion in a manner specifically dependent on its size. oHA promoted cell adhesion while nHA showed no effects. Our results might elucidate a molecular- and/or cellular-based mechanism for the diverse biological activities of nHA and oHA.

  10. 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

  11. Rule-based learning of regular past tense in children with specific language impairment.

    PubMed

    Smith-Lock, Karen M

    2015-01-01

    The treatment of children with specific language impairment was used as a means to investigate whether a single- or dual-mechanism theory best conceptualizes the acquisition of English past tense. The dual-mechanism theory proposes that regular English past-tense forms are produced via a rule-based process whereas past-tense forms of irregular verbs are stored in the lexicon. Single-mechanism theories propose that both regular and irregular past-tense verbs are stored in the lexicon. Five 5-year-olds with specific language impairment received treatment for regular past tense. The children were tested on regular past-tense production and third-person singular "s" twice before treatment and once after treatment, at eight-week intervals. Treatment consisted of one-hour play-based sessions, once weekly, for eight weeks. Crucially, treatment focused on different lexical items from those in the test. Each child demonstrated significant improvement on the untreated past-tense test items after treatment, but no improvement on the untreated third-person singular "s". Generalization to untreated past-tense verbs could not be attributed to a frequency effect or to phonological similarity of trained and tested items. It is argued that the results are consistent with a dual-mechanism theory of past-tense inflection.

  12. Enzymatic degradation of monolayer for poly(lactide) revealed by real-time atomic force microscopy: effects of stereochemical structure, molecular weight, and molecular branches on hydrolysis rates.

    PubMed

    Numata, Keiji; Finne-Wistrand, Anna; Albertsson, Ann-Christine; Doi, Yoshiharu; Abe, Hideki

    2008-08-01

    The influences of the stereochemical structure, the molecular weight, and the number of molecular branches for poly(lactide) (PLA) on enzymatic hydrolysis rates of PLA monolayers were studied by atomic force microscopy (AFM) and the Langmuir-Blodgett (LB) technique. Monolayers of six kinds of PLA with different molecular weights, stereochemical structure, and numbers of molecular branches were prepared by LB techniques and then characterized by AFM in air. The PLA molecules covered homogeneously with a silicon substrate and did not form lamellar crystals in the monolayer. We determined the initial hydrolysis rate of PLA monolayers in presence of proteinase K by volumetric analysis from the continuous AFM height images. The presence of D-lactyl unit reduced the hydrolysis rate of the monolayer. The hydrolysis rate for the linear PLLA samples increased with a decrease in the molecular weight. In contrast, the rates of erosion for branched PLLA monolayers were independent of the molecular weight of samples. The erosion rate of branched PLLA monolayers was found to be dependent on the average molecular weight of PLLA segment in branched molecules, not on the overall molecular weight of samples. From these results, furthermore, the hydrolysis mode of PLAs by proteinase K is discussed.

  13. Immunolocalization and molecular properties of a high molecular weight microtubule-bundling protein (syncolin) from chicken erythrocytes

    PubMed Central

    1991-01-01

    A protein of apparent molecular weight 280,000 (syncolin), which is immunoreactive with antibodies to hog brain microtubule-associated protein (MAP) 2, was purified from chicken erythrocytes. Immunofluorescence microscopy of bone marrow cells revealed the presence of syncolin in cells at all stages of erythrocyte differentiation. In early erythroblasts syncolin was diffusely distributed throughout the cytoplasm. At later stages it was found along microtubules of the marginal band, as confirmed by immunoelectron microscopy. The association of syncolin with the marginal band was dependent on the integrity of microtubules, as demonstrated by temperature-dependent de- and repolymerization or marginal band microtubules. Syncolin cosedimented in a saturable manner with microtubules assembled in vitro, and it was displaced from the polymer by salt. Brain as well as erythrocyte microtubules, reconstituted with taxol from MAP-free tubulin and purified syncolin, were aggregated into dense bundles containing up to 15 microtubules, as determined by electron microscopy. On the ultrastructural level, syncolin molecules were visualized as globular or ringlike structures, in contrast to the thin, threadlike appearance of filamentous MAPs, such as brain MAP 2. According to ultrastructural measurements and gel permeation chromatography, syncolin's molecular weight was approximately 1 x 10(6). It is suggested that syncolin's specific function is the cross- linking of microtubules in the marginal band and, by implication, the stabilization of this structure typical for nucleated (chicken) erythrocytes. PMID:1993737

  14. Dextran: Influence of Molecular Weight in Antioxidant Properties and Immunomodulatory Potential

    PubMed Central

    Soeiro, Vinicius C.; Melo, Karoline R. T.; Alves, Monique G. C. F.; Medeiros, Mayara J. C.; Grilo, Maria L. P. M.; Almeida-Lima, Jailma; Pontes, Daniel L.; Costa, Leandro S.; Rocha, Hugo A. O.

    2016-01-01

    Dextrans (α-d-glucans) extracted from Leuconostoc mesenteroides, with molecular weights (MW) of 10 (D10), 40 (D40) and 147 (D147) kDa, were evaluated as antioxidant, anticoagulant and immunomodulatory drugs for the first time. None presented anticoagulant activity. As for the antioxidant and immunomodulatory tests, a specific test showed an increase in the dextran activity that was proportional to the increase in molecular weight. In a different assay, however, activity decreased or showed no correlation to the MW. As an example, the reducing power assay showed that D147 was twice as potent as other dextrans. On the other hand, all three samples showed similar activity (50%) when it came to scavenging the OH radical, whereas only the D10 sample showed sharp activity (50%) when it came to scavenging the superoxide ion. D40 was the single dextran that presented with immunomodulatory features since it stimulated the proliferation (~50%) of murine macrophages (RAW 264.7) and decreased the release of nitric oxide (~40%) by the cells, both in the absence and presence of lipopolysaccharides (LPS). In addition, D40 showed a greater scavenging activity (50%) for the hydrogen peroxide, which caused it to also be the more potent dextran when it came to inhibiting lipid peroxidation (70%). These points toward dextrans with a 40 kDa weight as being ideal for antioxidant and immunomodulatory use. However, future studies with the D40 and other similarly 40 kDa dextrans are underway to confirm this hypothesis. PMID:27548151

  15. Dextran: Influence of Molecular Weight in Antioxidant Properties and Immunomodulatory Potential.

    PubMed

    Soeiro, Vinicius C; Melo, Karoline R T; Alves, Monique G C F; Medeiros, Mayara J C; Grilo, Maria L P M; Almeida-Lima, Jailma; Pontes, Daniel L; Costa, Leandro S; Rocha, Hugo A O

    2016-01-01

    Dextrans (α-d-glucans) extracted from Leuconostoc mesenteroides, with molecular weights (MW) of 10 (D10), 40 (D40) and 147 (D147) kDa, were evaluated as antioxidant, anticoagulant and immunomodulatory drugs for the first time. None presented anticoagulant activity. As for the antioxidant and immunomodulatory tests, a specific test showed an increase in the dextran activity that was proportional to the increase in molecular weight. In a different assay, however, activity decreased or showed no correlation to the MW. As an example, the reducing power assay showed that D147 was twice as potent as other dextrans. On the other hand, all three samples showed similar activity (50%) when it came to scavenging the OH radical, whereas only the D10 sample showed sharp activity (50%) when it came to scavenging the superoxide ion. D40 was the single dextran that presented with immunomodulatory features since it stimulated the proliferation (~50%) of murine macrophages (RAW 264.7) and decreased the release of nitric oxide (~40%) by the cells, both in the absence and presence of lipopolysaccharides (LPS). In addition, D40 showed a greater scavenging activity (50%) for the hydrogen peroxide, which caused it to also be the more potent dextran when it came to inhibiting lipid peroxidation (70%). These points toward dextrans with a 40 kDa weight as being ideal for antioxidant and immunomodulatory use. However, future studies with the D40 and other similarly 40 kDa dextrans are underway to confirm this hypothesis. PMID:27548151

  16. Effect of gamma irradiation on the friction and wear of ultrahigh molecular weight polyethylene

    NASA Technical Reports Server (NTRS)

    Jones, W. R.; Hady, W. F.; Crugnola, A.

    1981-01-01

    The effect of sterilization gamma irradiation on the friction and wear properties of ultrahigh molecular weight polyethylene (UHMWPE) sliding against stainless steel 316L in dry air at 23 C is investigated, the results to be used in the development of artificial joints which are to surgically replace diseased human joints. A pin-on-disk sliding friction apparatus is used, a constant sliding speed in the range 0.061-0.27 m/s is maintained, a normal load of 1 kgf is applied with dead weight, and the irradiation dose levels are: 0, 2.5, and 5.0 Mrad. Wear and friction data and conditions for each of the ten tests are summarized, and include: (1) wear volume as a function of the sliding distance for the irradiation levels, (2) incremental wear rate, and (3) coefficient of friction as a function of the sliding distance. It is shown that (1) the friction and wear properties of UHMWPE are not significantly changed by the irradiation doses of 2.5 and 5.0 Mrad, (2) the irradiation increases the amount of insoluble gel as well as the amount of low molecular weight material, and (3) after run-in the wear rate is either steady or gradually decreases as a function of the sliding distance.

  17. Anticancer activity of chemically prepared shrimp low molecular weight chitin evaluation with the human monocyte leukaemia cell line, THP-1.

    PubMed

    Salah, R; Michaud, P; Mati, F; Harrat, Z; Lounici, H; Abdi, N; Drouiche, N; Mameri, N

    2013-01-01

    In the present study, anticancer activities of chitin, chitosan and low molecular weight chitin were evaluated using a human tumour cell line, THP-1. A molecular weight-activity relationship and an electrostatic interaction-activity relationship were determined. The cytotoxic effects of chitin and derivatives were also evaluated using a normal human foetal lung fibroblastic cell line, MRC-5 and the specific cytotoxicity of chitin and derivatives to tumour cell lines was demonstrated. The high antitumour effect of low molecular weight of chitin was established.

  18. Sensor Based on Aptamer Folding to Detect Low-Molecular Weight Analytes.

    PubMed

    Osypova, Alina; Thakar, Dhruv; Dejeu, Jérôme; Bonnet, Hugues; Van der Heyden, Angéline; Dubacheva, Galina V; Richter, Ralf P; Defrancq, Eric; Spinelli, Nicolas; Coche-Guérente, Liliane; Labbé, Pierre

    2015-08-01

    Aptamers have emerged as promising biorecognition elements in the development of biosensors. The present work focuses on the application of quartz crystal microbalance with dissipation monitoring (QCM-D) for the enantioselective detection of a low molecular weight target molecule (less than 200 Da) by aptamer-based sensors. While QCM-D is a powerful technique for label-free, real-time characterization and quantification of molecular interactions at interfaces, the detection of small molecules interacting with immobilized receptors still remains a challenge. In the present study, we take advantage of the aptamer conformational changes upon the target binding that induces displacement of water acoustically coupled to the sensing layer. As a consequence, this phenomenon leads to a significant enhancement of the detection signal. The methodology is exemplified with the enantioselective recognition of a low molecular weight model compound, L-tyrosinamide (L-Tym). QCM-D monitoring of L-Tym interaction with the aptamer monolayer leads to an appreciable signal that can be further exploited for analytical purposes or thermodynamics studies. Furthermore, in situ combination of QCM-D with spectroscopic ellipsometry unambiguously demonstrates that the conformational change induces a nanometric decrease of the aptamer monolayer thickness. Since QCM-D is sensitive to the whole mass of the sensing layer including water that is acoustically coupled, a decrease in thickness of the highly hydrated aptamer layer induces a sizable release of water that can be easily detected by QCM-D. PMID:26122480

  19. Determination of the low molecular weight fraction of food-grade carrageenans.

    PubMed

    Spichtig, Véronique; Austin, Sean

    2008-01-01

    Recently there has been some debate regarding the presence and associated health risk of low molecular weight carrageenan in foodstuffs. Unfortunately measurement of the low molecular weight tail (LMT) of food-grade carrageenans (defined here as the carrageenan having relative molecular mass (Mr) below 50,000) is not trivial, largely due to its low abundance. So far methods employing light scattering have been unsuccessful in producing reproducible results, probably due to the poor detector response at low masses. In this work a method based on high performance size exclusion chromatography coupled to a refractive index detector (HPSEC-RI) has been used for the measurement of the LMT in food-grade carrageenan ingredients and in a carrageenan-containing finished product (a jelly). Over the course of half a year, 19 measurements were made on a reference carrageenan; the results demonstrated that the method had excellent reproducibility. Applied to a number of different carrageenan ingredients, it was found that, in general, the LMT represents less than 8% of the total carrageenan in ingredients, and under the correct conditions increases little during food processing. The data also indicated that pH appears to be a critical factor during food processing and pH levels below 4.0 should be avoided.

  20. Green Synthesis of Silver Nanoparticles: Effect of Dextran Molecular Weight Used as Stabilizing-Reducing Agent.

    PubMed

    Carré-Rangel, Luceldi; Alonso-Nuñez, Gabriel; Espinoza-Gómez, Heriberto; Flores-López, Lucía Z

    2015-12-01

    This paper describes an easy green chemistry method for the synthesis of silver nanoparticles (AgNPs). The AgNPs were obtained through the use of an aqueous silver nitrate solution (AgNO3), with dextrans aqueous solutions of different molecular weights acting as stabilizing and reducing agent, employing the chemical reduction method. We made a comparative study to determine which molecular weight dextran was the best stabilizing and reducing agent, and it was found that the molecular size of the stabilizing agent is inversely proportional to the size of the nanoparticle synthesized. The formation of the AgNPs was demonstrated by UV-Vis spectroscopy, atomic force microscopy (AFM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). SEM-EDS analysis shows the formation of particles with dendritic structure. TEM shows nanoparticles which are spherical in shape and 1-10 nm in size; also, the clear lattice fringes show highly crystalline AgNPs (FCC). PMID:26682423

  1. Sensor Based on Aptamer Folding to Detect Low-Molecular Weight Analytes.

    PubMed

    Osypova, Alina; Thakar, Dhruv; Dejeu, Jérôme; Bonnet, Hugues; Van der Heyden, Angéline; Dubacheva, Galina V; Richter, Ralf P; Defrancq, Eric; Spinelli, Nicolas; Coche-Guérente, Liliane; Labbé, Pierre

    2015-08-01

    Aptamers have emerged as promising biorecognition elements in the development of biosensors. The present work focuses on the application of quartz crystal microbalance with dissipation monitoring (QCM-D) for the enantioselective detection of a low molecular weight target molecule (less than 200 Da) by aptamer-based sensors. While QCM-D is a powerful technique for label-free, real-time characterization and quantification of molecular interactions at interfaces, the detection of small molecules interacting with immobilized receptors still remains a challenge. In the present study, we take advantage of the aptamer conformational changes upon the target binding that induces displacement of water acoustically coupled to the sensing layer. As a consequence, this phenomenon leads to a significant enhancement of the detection signal. The methodology is exemplified with the enantioselective recognition of a low molecular weight model compound, L-tyrosinamide (L-Tym). QCM-D monitoring of L-Tym interaction with the aptamer monolayer leads to an appreciable signal that can be further exploited for analytical purposes or thermodynamics studies. Furthermore, in situ combination of QCM-D with spectroscopic ellipsometry unambiguously demonstrates that the conformational change induces a nanometric decrease of the aptamer monolayer thickness. Since QCM-D is sensitive to the whole mass of the sensing layer including water that is acoustically coupled, a decrease in thickness of the highly hydrated aptamer layer induces a sizable release of water that can be easily detected by QCM-D.

  2. Metastable region of phase diagram: optimum parameter range for processing ultrahigh molecular weight polyethylene blends.

    PubMed

    Gai, Jing-Gang; Zuo, Yuan

    2012-06-01

    Numerous studies suggest that two-phase morphology and thick interface are separately beneficial to the viscosity reduction and mechanical property maintainence of the matrix when normal molecular weight polymer (NMWP) is used for modification of ultrahigh molecular weight polyethylene (UHMWPE). Nevertheless, it is very difficult to obtain a UHMWPE/NMWP blend which may demonstrate both two-phase morphology and thick interface. In this work, dissipative particle dynamics simulations and Flory-Huggins theory are applied in predicting the optimum NMWP and the corresponding conditions, wherein the melt flowability of UHMWPE can be improved while its mechanical properties can also be retained. As is indicated by dissipative particle dynamics simulations and phase diagram calculated from Flory-Huggins theory, too small Flory-Huggins interaction parameter (χ) and molecular chain length of NMWP (N(NMWP)) may lead to the formation of a homogeneous phase, whereas very large interfacial tension and thin interfaces might also appear when parameters N(NMWP) and χ are too large. When these parameters are located in the metastable region of the phase diagram, however, two-phase morphology occurs and interfaces of the blends are extremely thick. Therefore, metastable state is found to be advisable for both the viscosity reduction and mechanical property improvement of the UHMWPE/NMWP blends.

  3. Molecular Size and Weight of Asphaltene and Asphaltene Solubility Fractions from Coals, Crude Oils and Bitumen

    SciTech Connect

    Badre,S.; Goncalves, C.; Norinaga, K.; Gustavson, G.; Mullins, O.

    2005-01-01

    The molecular weight of asphaltenes has been a controversy for several decades. In recent years, several techniques have converged on the size of the fused ring system; indicating that chromophores in virgin crude oil asphaltenes typically have 4-10 fused rings. Consequently, the molecular weight debate is equivalent to determining whether asphaltenes are monomeric (one fused-ring system per molecule) or whether they are polymeric. Time-resolved fluorescence depolarization (FD) is employed here to interrogate the absolute size of asphaltene molecules and to determine the relation of the size of the fused ring system to that of the corresponding molecule. Coal, petroleum and bitumen asphaltenes are compared. Molecular size of coal asphaltenes obtained here by FD-determined rotational diffusion match closely with Taylor-dispersion-derived translational diffusion measurements with UV absorption. Coal asphaltenes are smaller than petroleum asphaltenes. N-methyl pyrrolidinone (NMP) soluble and insoluble fractions are examined. NMP soluble and insoluble fractions of asphaltenes are monomeric. It is suggested that the 'giant' asphaltene molecules reported from SEC studies using NMP as the eluting solvent may actually be the expected flocs of asphaltene which are not soluble in NMP. Data is presented that intramolecular electronic relaxation in asphaltenes does not perturb FD results.

  4. Human brain tumor-associated urinary high molecular weight transforming growth factor: a high molecular weight form of epidermal growth factor.

    PubMed

    Stromberg, K; Hudgins, W R; Dorman, L S; Henderson, L E; Sowder, R C; Sherrell, B J; Mount, C D; Orth, D N

    1987-02-15

    Urinary protein obtained from a patient with a highly malignant brain tumor (astrocytoma, grade IV) was adsorbed to trimethylsilyl controlled-pore glass beads and selectively eluted with acetonitrile to yield a high molecular weight (HMW) human transforming growth factor (hTGF). This HMW hTGF promoted clonogenic cell growth in soft agar and competed for membrane receptors with mouse epidermal growth factor. After surgical resection of the tumor, no HMW hTGF was found in urine. HMW hTGF generated a human EGF (hEGF) radioimmunoassay competitive binding curve similar to that of hEGF and parallel to that of a highly purified HMW form of hEGF previously reported to be present in trace concentrations in normal human urine. Both hEGF and HMW hEGF were clonogenic in soft agar, and their clonogenic activity as well as that of HMW hTGF was inhibited by anti-hEGF serum. Both HMW hTGF and HMW hEGF had 20 to 25% of the radioreceptor binding activity of hEGF. HMW hTGF purified from the pooled urine of several patients with malignant astrocytomas and HMW hEGF purified from normal control urine comigrated at Mr 33,000. Thus, HMW hTGF was indistinguishable from HMW hEGF in terms of apparent molecular size, epidermal growth factor receptor binding activity, epidermal growth factor immunoreactivity, and clonogenic activity. Urinary HMW hEGF/hTGF may be of tumor cell origin or may represent a response of normal host tissues to the tumor or its products.

  5. Correlation between human maternal-fetal placental transfer and molecular weight of PCB and dioxin congeners/isomers.

    PubMed

    Mori, Chisato; Nakamura, Noriko; Todaka, Emiko; Fujisaki, Takeyoshi; Matsuno, Yoshiharu; Nakaoka, Hiroko; Hanazato, Masamichi

    2014-11-01

    Establishing methods for the assessment of fetal exposure to chemicals is important for the prevention or prediction of the child's future disease risk. In the present study, we aimed to determine the influence of molecular weight on the likelihood of chemical transfer from mother to fetus via the placenta. The correlation between molecular weight and placental transfer rates of congeners/isomers of polychlorinated biphenyls (PCBs) and dioxins was examined. Twenty-nine sample sets of maternal blood, umbilical cord, and umbilical cord blood were used to measure PCB concentration, and 41 sample sets were used to analyze dioxins. Placental transfer rates were calculated using the concentrations of PCBs, dioxins, and their congeners/isomers within these sample sets. Transfer rate correlated negatively with molecular weight for PCB congeners, normalized using wet and lipid weights. The transfer rates of PCB or dioxin congeners differed from those of total PCBs or dioxins. The transfer rate for dioxin congeners did not always correlate significantly with molecular weight, perhaps because of the small sample size or other factors. Further improvement of the analytical methods for dioxin congeners is required. The findings of the present study suggested that PCBs, dioxins, or their congeners with lower molecular weights are more likely to be transferred from mother to fetus via the placenta. Consideration of chemical molecular weight and transfer rate could therefore contribute to the assessment of fetal exposure.

  6. The Role of High Molecular Weight Chains in Flow-Induced Crystallization Precursor Structures

    SciTech Connect

    Yang,L.; Somani, R.; Scis, I.; Hsiao, B.; Kolb, R.; Lohse, D.

    2006-01-01

    Flow-induced crystallization in a bimodal polyethylene blend was investigated by means of in situ shear-WAXD (wide-angle x-ray diffraction) and shear-SAXS (small-angle x-ray scattering) techniques. The blend contained a low molecular weight (M{sub w} = 50 000 g mol{sup -1} and polydispersity = 2) polyethylene copolymer matrix (MB-50k) with 2 mol% of hexene, and a nearly monodisperse high molecular weight (M{sub w} = 161 000 g mol{sup -1} and polydispersity = 1.1) hydrogenated polybutadiene component (MD-161k), which has the microstructure of an ethylene-butene copolymer with 4 mol% butene. At the experimental temperatures of 112 and 115 C, MB-50k exhibited faster crystallization kinetics and higher crystallinity due to higher chain mobility and higher ethylene content than those of the MB-50k/MD-161k blend. However, both WAXD and SAXS results indicated that the high molecular weight component (MD-161k) is responsible for the formation of more highly oriented crystals, which we relate to a shear-induced precursor scaffold. Values of the lamellar long period in all experimental runs were found to slightly decrease in the beginning of crystallization and then reached a plateau value. Vonk's method for single lamella scattering was employed to estimate the lamellar thickness in the MB-50k/MD-161k blend at high temperature (115 C), where the lamellar thickness was also found to decrease in the beginning and remained about constant afterward. Twisted lamellar structures were observed in all formed kebabs.

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

    DOE PAGESBeta

    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

  8. The role of high molecular weight chains in flow-induced crystallization precursor structures

    NASA Astrophysics Data System (ADS)

    Yang, Ling; Somani, Rajesh H.; Sics, Igors; Hsiao, Benjamin S.; Kolb, Rainer; Lohse, David

    2006-09-01

    Flow-induced crystallization in a bimodal polyethylene blend was investigated by means of in situ shear-WAXD (wide-angle x-ray diffraction) and shear-SAXS (small-angle x-ray scattering) techniques. The blend contained a low molecular weight (Mw = 50 000 g mol-1 and polydispersity = 2) polyethylene copolymer matrix (MB-50k) with 2 mol% of hexene, and a nearly monodisperse high molecular weight (Mw = 161 000 g mol-1 and polydispersity = 1.1) hydrogenated polybutadiene component (MD-161k), which has the microstructure of an ethylene-butene copolymer with 4 mol% butene. At the experimental temperatures of 112 and 115 °C, MB-50k exhibited faster crystallization kinetics and higher crystallinity due to higher chain mobility and higher ethylene content than those of the MB-50k/MD-161k blend. However, both WAXD and SAXS results indicated that the high molecular weight component (MD-161k) is responsible for the formation of more highly oriented crystals, which we relate to a shear-induced precursor scaffold. Values of the lamellar long period in all experimental runs were found to slightly decrease in the beginning of crystallization and then reached a plateau value. Vonk's method for single lamella scattering was employed to estimate the lamellar thickness in the MB-50k/MD-161k blend at high temperature (115 °C), where the lamellar thickness was also found to decrease in the beginning and remained about constant afterward. Twisted lamellar structures were observed in all formed kebabs.

  9. Isolation of a very high molecular weight polylactosamine from an ovarian cyst mucin of blood group

    SciTech Connect

    Wu, A.S.S.; Bush, C.A.

    1986-05-01

    Treatment of a blood group A active ovarian cyst mucin glycoprotein with alkaline borohydride under conditions expected to cleave-O-glycosidically linked carbohydrate chains releases a polysaccharide of average molecular weight 25,000 daltons. It contains no peptide or mannose at the 1% level and carbohydrate analysis gives fuc:galNAc:gal:glcNAc in the ratio of 1:1:2.5:2.5. The /sup 13/C and /sup 1/H NMR spectra show that the polysaccharide has non-reducing terminal side chains of the structure galNAc(..cap alpha..-1 ..-->.. 3)(fuc(..cap alpha..-1 ..-->.. 2)) gal(..beta..-1 ..-->.. 3) glcNAc (i.e. a type 1 chain). Periodate oxidation removes all the fucose and galNAc from the non-reducing terminal but leaves intact the backbone composed of ..beta..-linked gal and glcNAc as would be expected for a polylactosamine. They conclude that this is a high molecular weight polylactosamine which is related to the asparagine linked polylactosamine chains of cell surface glycoproteins which have been implicated in cell differentiation. However, the blood group A polysaccharide from the ovarian cyst mucin is unique in several respects. It has a much larger molecular weight than even the erythroglycan of the red cell membrane protein, band 3, and is linked to the protein by an -O-glycosidic bond rather than the -N-asparagine linkage of the previously known polylactosamines which have a trimannosyl core. Its blood group A side chains are on a type one core rather than type 2 which is found on other polylactosamines.

  10. 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.

  11. [Evaluation of molecular weights of hyaluronate preparations by multi-angle laser light scattering].

    PubMed

    Yomota, Chikako

    2003-01-01

    Hyaluronate (HA), a glycosaminoglycan polysaccharide, has been used for osteoarthritis, periartritis of the shoulder and rheumatoid arthritis by intraarticular administration, and in ophthalmic surgery such as anterior segment surgery, and eye lotion. In this study, the molecular weight (Mw) of HA preparations were estimated by size-exclusion chromatography (SEC) system consisted of a refractometer (RI) and a multi-angle laser light scattering (MALS). From the results, it has been clarified that a successful characterization of HA samples with Mw up to 2 - 3 x 10(6) g/mol was possible by multidetector system.

  12. Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand-metal interactions.

    PubMed

    Mark, Stefan; Wadepohl, Hubert; Enders, Markus

    2016-01-01

    A series of Cr(III) complexes based on quinoline-cyclopentadienyl ligands with additional hemilabile side arms were prepared and used as single-site catalyst precursors for ethylene polymerization. The additional donor functions interact with the metal centers only after activation with the co-catalyst. Evidence for this comes from DFT-calculations and from the differing behavior of the complexes in ethylene polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers. PMID:27559387

  13. 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

  14. Reliable low-molecular-weight heparin reversal in a child undergoing emergency surgery: a case report.

    PubMed

    Botros, Mena M; Mahmoud, Mohamed A; Costandi, Andrew J

    2016-09-01

    Low-molecular-weight heparin neutralization using protamine alone can be unreliable, especially in cases of immediate reversal for emergency surgery. Here, we describe a unique case of a 17-month-old girl with a history of glioneuronal tumor and corresponding hydrocephalus status post debulking and ventriculoperitoneal shunt placement, who was placed on enoxaparin after the development of a sagittal sinus thrombosis. Patient presented for emergency craniectomy and evacuation of subdural bleed after a fall while on therapeutic dose of enoxaparin. Protamine and fresh frozen plasma were used in the patient's perioperative course providing a reliable reversal of enoxaparin. PMID:27555185

  15. An investigation of the preparation of high molecular weight perfluorocarbon polyethers

    NASA Technical Reports Server (NTRS)

    Watts, R. O.; Tarrant, P.

    1972-01-01

    High molecular weight perfluorocarbon polyether gums were obtained by photolysis of perfluorodienes and discyl fluorides containing a perfluorocarbon polyether backbond. The materials obtained are represented by chemical formulas. A method was developed whereby reactive acyl fluoride and trifluorovinyl end groups are converted into inert structures. In order to investigate the possible preparation of difunctional molecules which may be useful in polymer synthesis, the reactions of hexafluoropropene oxide (HFPO) with Grignard and organolithium reagents have been studied. Reactions of various nucleophilic reagents with HFPO were also investigated.

  16. Development of C3-Symmetric Tris-Urea Low-Molecular-Weight Gelators.

    PubMed

    Yamanaka, Masamichi

    2016-04-01

    This article describes recent developments in C3 -symmetric tris-urea low-molecular-weight gelators and their applications. The C3 -symmetric tris-ureas are excellent frameworks to form supramolecular polymers through noncovalent interactions. In organic solvents, hydrophobic tris-ureas form supramolecular gels. Amphiphilic tris-ureas form supramolecular gels in aqueous media. Functional supramolecular gels were prepared by introducing appropriate functional groups into the outer sphere of tris-ureas. Supramolecular hydrogels obtained from amphiphilic tris-ureas were used in the electrophoresis of proteins. These electrophoreses results showed several unique characteristics compared to typical electrophoreses results obtained using polyacrylamide matrices. PMID:26915980

  17. The skin: target organ in immunotoxicology of small-molecular-weight compounds.

    PubMed

    Merk, H F; Sachs, B; Baron, J

    2001-01-01

    Immunotoxicology studies two different effects of xenobiotics: immunosuppression and dysregulation of immune responses leading to hypersensitivity or autoimmunity. The skin is a major target organ of immunotoxicity which is provoked by small-molecular-weight compounds. Methods may be helpful for immunotoxicological investigations and screenings for adverse effects of xenobiotics which are used for diagnosis or studies on the pathophysiology of skin disorders such as allergic contact dermatitis, cutaneous drug-allergic reactions or autoimmune diseases of the skin. Examples include well-designed patch tests, assays involving antigen-presenting cells such as dendritic cells, but also T lymphocytes, basophiles or keratinocytes.

  18. High molecular weight glycosaminoglycans in AA type amyloid fibril extracts from human liver.

    PubMed Central

    Magnus, J H; Kolset, S O; Husby, G

    1991-01-01

    Glycosaminoglycans have previously been identified in extracts of AA type hepatic amyloid fibril from a patient with amyloidosis associated with juvenile rheumatoid arthritis. The macromolecular properties of these polysaccharides are described here in more detail. By gel filtration and ion exchange chromatography glycosaminoglycans in the form of high molecular weight free chains were shown to coisolate with water extracted amyloid fibrils. About 60% of these were characterised as galactosamines (chondroitin sulphate/dermatan sulphate), whereas the remaining 40% consisted of N-sulphated glucosamines (heparin/heparan sulphate). The amyloid associated glycosaminoglycans were not part of intact proteoglycans in the fibril extracts. PMID:1888198

  19. [Venous thrombo-embolic disease in cancer. Low molecular weight heparin indications].

    PubMed

    Nou, M; Laroche, J-P

    2016-05-01

    Cancer and venous thrombo-embolic disease (VTE) are closely related. Indeed, cancer can reveal VTE and VTE can be the first sign of cancer. Low molecular weight heparin (LWMH) is now the first line treatment in cancer patients. Compliance with marketing authorizations and guidelines are crucial for patient-centered decision-making. This work deals with the prescription of LWMH in patients who develop VTE during cancer in order to better recognize what should or should not be done. The patient's wishes must be taken into consideration when making the final therapeutic decision. The other treatments are discussed: vitamin K antagonists and direct oral anticoagulants (DOACs) may be useful. PMID:27146099

  20. Fluorocarbon Modified Low-Molecular-Weight Polyethylenimine for siRNA Delivery.

    PubMed

    Johnson, Mark E; Shon, Judy; Guan, Brian M; Patterson, Joseph P; Oldenhuis, Nathan J; Eldredge, Alexander C; Gianneschi, Nathan C; Guan, Zhibin

    2016-08-17

    We report the synthesis and study of fluorocarbon (FC) modified polyethylenimine (PEI) for the purpose of siRNA delivery. Low-molecular-weight PEI (Mn = 600) was functionalized with fluorocarbon epoxides of varying length. All FC-modified samples with greater than 2.0 equiv of FC epoxide per PEI induced potent gene silencing in vitro. Compared to hydrocarbon (HC) analogues, the FC vectors showed greater general silencing efficacy, higher cell uptake, and reduced association with serum components. Collectively, the data suggest that modification of polyamines with FCs is a promising approach for the discovery of novel vectors for siRNA delivery.

  1. Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand–metal interactions

    PubMed Central

    Mark, Stefan; Wadepohl, Hubert

    2016-01-01

    Summary A series of Cr(III) complexes based on quinoline-cyclopentadienyl ligands with additional hemilabile side arms were prepared and used as single-site catalyst precursors for ethylene polymerization. The additional donor functions interact with the metal centers only after activation with the co-catalyst. Evidence for this comes from DFT-calculations and from the differing behavior of the complexes in ethylene polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers. PMID:27559387

  2. [Effect of dextran of 250.000 molecular weight on experimental cholesterin-sclerosis in rabbits].

    PubMed

    Ferenc, S; Arpád, H; Gábor, L

    1976-07-01

    Effect of dextran of 250000 molecular weight on experimental cholesterin-sclerosis of rabbits was studied. Doses of 120 (mg/week) kg and 1200 (mg/week) kg administered during 12 weeks have resulted a protective effect. When doses of 1200 (mg/week) kg have been administered--in the aortic adventitia intensive cellular reaction, no hitherto described was revealed, which was considered to be a sing of the exhaustion of RES. This publication authors regard as a preliminary one. To clear whether the cellular reaction observed is a dextran-specific or macro-moleculespecific one further investigations are needed.

  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. Computational and experimental investigation of DNA repair protein photolyase interactions with low molecular weight drugs.

    PubMed

    Azizoğlu, Selimcan; Kizilel, Riza; Marušič, Maja; Kavakli, Ibrahim Halil; Erman, Burak; Kizilel, Seda

    2013-07-01

    This paper reports the previously unknown interactions between eight low molecular weight commercially available drugs (130-800 Da) and DNA repair protein photolyase using computational docking simulations and surface plasmon resonance (SPR) experiments. Theoretical dissociation constants, K(d), obtained from molecular docking simulations were compared with the values found from SPR experiments. Among the eight drugs analyzed, computational and experimental values showed similar binding affinities between selected drug and protein pairs. We found no significant differences in binding interactions between pure and commercial forms of the drug lornoxicam and DNA photolyase. Among the eight drugs studied, prednisone, desloratadine, and azelastine exhibited the highest binding affinity (K(d) = 1.65, 2.05, and 8.47 μM, respectively) toward DNA photolyase. Results obtained in this study are promising for use in the prediction of unknown interactions of common drugs with specific proteins such as human clock protein cryptochrome. PMID:23657985

  5. Structure refinement with molecular dynamics and a Boltzmann-weighted ensemble.

    PubMed

    Fennen, J; Torda, A E; van Gunsteren, W F

    1995-09-01

    Time-averaging restraints in molecular dynamics simulations were introduced to account for the averaging implicit in spectroscopic data. Space- or molecule-averaging restraints have been used to overcome the fact that not all molecular conformations can be visited during the finite time of a simulation of a single molecule. In this work we address the issue of using the correct Boltzmann weighting for each member of an ensemble, both in time and in space. It is shown that the molecular- or space-averaging method is simple in theory, but requires a priori knowledge of the behaviour of a system. This is illustrated using a five-atom model system and the small cycle peptide analogue somatostatin. When different molecular conformers that are separated by energy barriers insurmountable on the time scale of a simulation contribute significantly to a measured NOE intensity, the use of space- or molecule-averaged distance restraints yields a more appropriate description of the measured data than conventional single-molecule refinement with or without application of time averaging.

  6. Dragline silk: a fiber assembled with low-molecular-weight cysteine-rich proteins.

    PubMed

    Pham, Thanh; Chuang, Tyler; Lin, Albert; Joo, Hyun; Tsai, Jerry; Crawford, Taylor; Zhao, Liang; Williams, Caroline; Hsia, Yang; Vierra, Craig

    2014-11-10

    Dragline silk has been proposed to contain two main protein constituents, MaSp1 and MaSp2. However, the mechanical properties of synthetic spider silks spun from recombinant MaSp1 and MaSp2 proteins have yet to approach natural fibers, implying the natural spinning dope is missing critical factors. Here we report the discovery of novel molecular constituents within the spinning dope that are extruded into dragline silk. Protein studies of the liquid spinning dope from the major ampullate gland, coupled with the analysis of dragline silk fibers using mass spectrometry, demonstrate the presence of a new family of low-molecular-weight cysteine-rich proteins (CRPs) that colocalize with the MA fibroins. Expression of the CRP family members is linked to dragline silk production, specifically MaSp1 and MaSp2 mRNA synthesis. Biochemical data support that CRP molecules are secreted into the spinning dope and assembled into macromolecular complexes via disulfide bond linkages. Sequence analysis supports that CRP molecules share similarities to members that belong to the cystine slipknot superfamily, suggesting that these factors may have evolved to increase fiber toughness by serving as molecular hubs that dissipate large amounts of energy under stress. Collectively, our findings provide molecular details about the components of dragline silk, providing new insight that will advance materials development of synthetic spider silk for industrial applications. PMID:25259849

  7. Screening for low molecular weight compounds in fish meal solubles by hydrophilic interaction liquid chromatography coupled to mass spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple analytical method using hydrophilic interaction liquid chromatography coupled with mass spectrometry was developed to screen for low molecular weight compounds in enzyme treated and untreated Alaskan pollock (Theragra chalcogramma) stickwater (SW) generated from processing fish meal with po...

  8. Thromboprophylaxis with low-molecular-weight heparin in outpatients with plaster-cast immobilisation of the leg.

    PubMed

    Kock, H J; Schmit-Neuerburg, K P; Hanke, J; Rudofsky, G; Hirche, H

    1995-08-19

    Deep-vein thrombosis is common after plaster-cast immobilisation for traumatic injury. We did a randomised prospective study of the effect of low-molecular-weight heparin on the incidence of deep-vein thrombosis in patients with minor injuries treated with plaster-cast immobilisation of the leg. A control group (n = 163) received no prophylaxis, the prophylaxis group received low-molecular-weight heparin once daily (n = 176). The incidence of deep-vein thrombosis in the prophylaxis group was 0% (one tailed p < 0.006) vs 4.3% in the control group. No severe side-effects of low-molecular-weight heparin were observed. Thromboprophylaxis with low-molecular-weight heparin once daily is effective in reducing the risk of deep-vein thrombosis in outpatients with plaster-cast immobilisation of the leg.

  9. Effects of the Terminal Structure, Purity, and Molecular Weight of an Amorphous Conjugated Polymer on Its Photovoltaic Characteristics.

    PubMed

    Kuwabara, Junpei; Yasuda, Takeshi; Takase, Naoto; Kanbara, Takaki

    2016-01-27

    The photovoltaic characteristics of an amorphous polymer containing EDOT and fluorene units were investigated. In particular, the effects of the terminal structure, residual amount of Pd, and molecular weight were systematically investigated. Direct arylation polycondensation of EDOT followed by an established purification method readily afforded polymers with different terminal structures, Pd contents, and molecular weights. Of these factors, the terminal structure of the polymer was a crucial factor affecting the photovoltaic characteristics. For example, the polymer with a Br terminal had a PCE of 2.9% in bulk-heterojunction organic photovoltaics (BHJ OPVs) with a fullerene derivative, whereas the polymer without a Br terminal had a PCE of 4.6% in the same cell configuration. The decreased Pd residues and high molecular weights of the polymers increased the long-term stability of the devices. Moreover, BHJ OPVs containing the high-molecular-weight polymer could be fabricated with an environmentally friendly nonhalogenated solvent.

  10. Tense Marking and Spontaneous Speech Measures in Spanish Specific Language Impairment: A Discriminant Function Analysis

    ERIC Educational Resources Information Center

    Grinstead, John; Baron, Alisa; Vega-Mendoza, Mariana; De la Mora, Juliana; Cantu-Sanchez, Myriam; Flores, Blanca

    2013-01-01

    Purpose: To test the proposal that the tense deficit that has been demonstrated for children with specific language impairment (SLI) in other languages is also found in child Spanish and that low performance on tense-related measures can distinguish Spanish-speaking children with SLI from those without. Method: The authors evaluated evidence from…

  11. The Effect of Temporal Adverbials on Past Tense Production by Children with Specific Language Impairment

    ERIC Educational Resources Information Center

    Krantz, Laurie R.; Leonard, Laurence B.

    2007-01-01

    Purpose: Children with specific language impairment (SLI) often fail to produce past tense forms in obligatory contexts, although the factors affecting such inconsistency are not well understood. This study examined the influence of accompanying temporal adverbials (e.g., "just, already") on the past tense production of these children. Method:…

  12. Quasiregularity and Its Discontents: The Legacy of the Past Tense Debate

    ERIC Educational Resources Information Center

    Seidenberg, Mark S.; Plaut, David C.

    2014-01-01

    Rumelhart and McClelland's chapter about learning the past tense created a degree of controversy extraordinary even in the adversarial culture of modern science. It also stimulated a vast amount of research that advanced the understanding of the past tense, inflectional morphology in English and other languages, the nature of linguistic…

  13. The Discourse Function of the Greek Future Tense-Form: A Corpus Linguistic Discourse Analysis

    ERIC Educational Resources Information Center

    Long, Craig M.

    2013-01-01

    As the Greek verbal system has become the subject of various dissertations and monographs, the future tense-form has been generally overlooked in the discussion. This dissertation seeks to overcome this lacuna by suggesting that the future tense-form functions as a rhetorical feature that expresses the author's expectation of an alternative state…

  14. Acquisition of Tense Marking in English-Speaking Children with Cochlear Implants: A Longitudinal Study

    PubMed Central

    Guo, Ling-Yu

    2013-01-01

    This study investigated the development of tense markers (e.g., past tense –ed) in children with cochlear implants (CIs) over a 3-year span. Nine children who received CIs before 30 months of age participated in this study at three, four, and five years postimplantation. Nine typical 3-, 4-, and 5-year- olds served as control groups. All children participated in a story-retell task. Percent correct of tense marking in the task was computed. Within the groups, percent correct of tense marking changed significantly in children with CIs and in typical children who had more hearing experience. Across the groups, children with CIs were significantly less accurate in tense marking than typical children at four and five years postimplantation. In addition, the performance of tense marking in children with CIs was correlated with their speech perception skills at earlier time points. Errors of tense marking tended to be omission rather than commission errors in typical children as well as in children with CIs. The findings suggested that despite the perceptual and processing constraints, children who received CIs may learn tense marking albeit with a delayed pattern. PMID:23288713

  15. Production of Tense Morphology by Afrikaans-Speaking Children with and without Specific Language Impairment

    ERIC Educational Resources Information Center

    Southwood, Frenette; van Hout, Roeland

    2010-01-01

    Purpose: To establish whether the predictions of the extended optional infinitive (EOI) hypothesis (Rice, Wexler, & Cleave, 1995) hold for the language of Afrikaans-speaking children with specific language impairment (SLI) and whether tense marking is a possible clinical marker of SLI in Afrikaans. Method: Production of tense morphology was…

  16. Past Tense Production by English Second Language Learners with and without Language Impairment

    ERIC Educational Resources Information Center

    Blom, Elma; Paradis, Johanne

    2013-01-01

    Purpose: This study investigated whether past tense use could differentiate children with language impairment (LI) from their typically developing (TD) peers when English is children's second language (L2) and whether L2 children's past tense profiles followed the predictions of Bybee's (2007) usage-based network model. Method: A group of L2…

  17. Error Analysis of Present Simple Tense in the Interlanguage of Adult Arab English Language Learners

    ERIC Educational Resources Information Center

    Muftah, Muneera; Rafik-Galea, Shameem

    2013-01-01

    The present study analyses errors on present simple tense among adult Arab English language learners. It focuses on the error on 3sg "-s" (the third person singular present tense agreement morpheme "-s"). The learners are undergraduate adult Arabic speakers learning English as a foreign language. The study gathered data from…

  18. Past-Tense Morphology and Phonological Deficits in Children with Dyslexia and Children with Language Impairment

    ERIC Educational Resources Information Center

    Robertson, Erin K.; Joanisse, Marc F.; Desroches, Amy S.; Terry, Alexandra

    2013-01-01

    The authors investigated past-tense morphology problems in children with dyslexia compared to those classically observed in children with oral language impairment (LI). Children were tested on a past-tense elicitation task involving regulars ("look-looked"), irregulars ("take-took"), and nonwords ("murn-murned"). Phonological skills were also…

  19. Acquiring Regular and Irregular Past Tense Morphemes in English and French: Evidence from Bilingual Children

    ERIC Educational Resources Information Center

    Nicoladis, Elena; Paradis, Johanne

    2012-01-01

    The aim of this study was to use crosslinguistic data from French-English bilinguals to test two models of past tense acquisition: (a) single route (all past tense forms rely on morphophonological schemas) and (b) dual route (irregular forms are learned as words, regulars through rules). These models make similar predictions about English…

  20. Past Tense Productivity in Dutch Children with and without SLI: The Role of Morphophonology and Frequency

    ERIC Educational Resources Information Center

    Rispens, Judith E.; De Bree, Elise H.

    2014-01-01

    This study focuses on morphophonology and frequency in past tense production. It was assessed whether Dutch five- and seven-year-old typically developing (TD) children and eight-year-old children with specific language impairment (SLI) produce the correct allomorph in regular, irregular, and novel past tense formation. Type frequency of the…

  1. A Challenge to Current Models of Past Tense Inflection: The Impact of Phonotactics

    ERIC Educational Resources Information Center

    Marshall, Chloe R.; van der Lely, Heather K. J.

    2006-01-01

    Is past tense production better modelled by a Single Mechanism or a Words and Rules model? We present data concerning a phenomenon that has not been considered by either model--regular past tense verbs with contrasting phonotactics. One set of verbs contains clusters at the inflected verb end that also occur in monomorphemic words…

  2. Acquisition of Tense Marking in English-Speaking Children with Cochlear Implants: A Longitudinal Study

    ERIC Educational Resources Information Center

    Guo, Ling-Yu; Spencer, Linda J.; Tomblin, J. Bruce

    2013-01-01

    This study investigated the development of tense markers (e.g., past tense -ed) in children with cochlear implants (CIs) over a 3-year span. Nine children who received CIs before 30 months of age participated in this study at three, four, and five years postimplantation. Nine typical 3-, 4-, and 5-year- olds served as control groups. All children…

  3. Past Tense Marking by African American English-Speaking Children Reared in Poverty

    ERIC Educational Resources Information Center

    Pruitt, Sonja; Oetting, Janna

    2009-01-01

    Purpose: This study examined past tense marking by African American English (AAE)-speaking children from low- and middle-income backgrounds to determine if poverty affects children's marking of past tense in ways that mirror the clinical condition of specific language impairment (SLI). Method: Participants were 15 AAE-speaking 6-year-olds from…

  4. The molecular weight of rhodopsin and the nature of the rhodopsin-digitonin complex.

    PubMed

    HUBBARD, R

    1954-01-20

    The sedimentation behavior of aqueous solutions of digitonin and of cattle rhodopsin in digitonin has been examined in the ultracentrifuge. In confirmation of earlier work, digitonin was found to sediment as a micelle (D-1) with an s(20) of about 6.35 Svedberg units, and containing at least 60 molecules. The rhodopsin solutions sediment as a stoichiometric complex of rhodopsin with digitonin (RD-1) with an s(20) of about 9.77 Svedberg units. The s(20) of the RD-1 micelle is constant between pH 6.3 and 9.6, and in the presence of excess digitonin. RD-1 travels as a single boundary also in the electrophoresis apparatus at pH 8.5, and on filter paper at pH 8.0. The molecular weight of the RD-1 micelle lies between 260,000 and 290,000. Of this, only about 40,000 gm. are due to rhodopsin; the rest is digitonin (180 to 200 moles). Comparison of the relative concentrations of RD-1 and retinene in solutions of rhodopsin-digitonin shows that RD-1 contains only one retinene equivalent. It can therefore contain only one molecule of rhodopsin with a molecular weight of about 40,000. Cattle rhodopsin therefore contains only one chromophore consisting of a single molecule of retinene. It is likely that frog rhodopsin has a similar molecular weight and also contains only one chromophore per molecule. The molar extinction coefficient of rhodopsin is therefore identical with the extinction coefficient per mole of retinene (40,600 cm.(2) per mole) and the E(1 per cent, 1 cm., 500 mmicro) has a value of about 10. Rhodopsin constitutes about 14 per cent of the dry weight, and 3.7 per cent of the wet weight of cattle outer limbs. This corresponds to about 4.2 x 10(6) molecules of rhodopsin per outer limb. The rhodopsin content of frog outer limbs is considerably higher: about 35 per cent of the dry weight, and 10 per cent of the wet weight, corresponding to about 2.1 x 10(9) molecules per outer limb. Thus the frog outer limb contains about five hundred times as much rhodopsin as the

  5. Examination of the change in returning molecular weight obtained during inhibitor squeeze treatments using polyacrylate based inhibitors

    SciTech Connect

    Graham, G.M.; Sorbie, K.S.

    1995-11-01

    Scale inhibitors based on small polyelectrolytes are often employed in oilfield scale prevention treatments. These materials are injected into the near-well formation of producers in a scale inhibitor squeeze treatment. When the well is brought back on production, the objective is for the return concentration level of the inhibitor in the produced brine to be at or above a certain threshold level, C{sub t}. This threshold level is the minimum inhibitor concentration required to prevent the formation of mineral carbonate or sulfate scales in that well. The squeeze lifetime depends strongly on the nature of the interaction between the inhibitor and the formation either through an adsorption or precipitation mechanism. Both adsorption and precipitation processes depend on the molecular weight of the scale inhibitor, as well as on a range of other factors. However, polymeric inhibitor species always display some degree of polydispersity (spread of molecular weight). In this paper, the authors examine the effects of molecular weight on adsorption/desorption phenomena for polyacrylate based inhibitor species. This work shows that, in the inhibitor effluent after a squeeze treatment, the molecular weight of the returning inhibitor may be different from that which was injected. For commercially available polymeric inhibitor species, they demonstrate using core floods that preferential retention of higher molecular weight components occurs and preferential desorption of lower molecular weight components is observed. This leads to a gradation in molecular weight in the return profile, which can lead to increased molecular weight components returning as the inhibitor concentration approaches the threshold level. The significance of this observation to field application of polymeric inhibitor species is discussed.

  6. Effects of Molecular Weight upon Irradiation-Cross-Linked Poly(vinyl alcohol)/Clay Aerogel Properties.

    PubMed

    Chen, Hong-Bing; Zhao, Yan; Shen, Peng; Wang, Jun-Sheng; Huang, Wei; Schiraldi, David A

    2015-09-16

    Facile fabrication of mechanically strong poly(vinyl alcohol) (PVOH)/clay aerogel composites through a combination of increasing polymer molecular weights and gamma irradiation-cross-linking is reported herein. The aerogels produced from high polymer molecular weights exhibit significantly increased compressive moduli, similar to the effect of irradiation-induced cross-linking. The required irradiation dose for fabricating strong PVOH composite aerogels with dense microstructure decreased with increasing polymer molecular weight. Neither thermal stability nor flammability was significantly changed by altering the polymer molecular weight or by modest gamma irradiation, but they were highly dependent upon the polymer/clay ratio in the aerogel. Optimization of the mechanical, thermal, and flammability properties of these composite aerogels could therefore be obtained by using relatively low levels of polymer, with very high polymer molecular weight, or lower molecular weight coupled with moderate gamma irradiation. The facile preparation of strong, low flammability aerogels is an alternative to traditional polymer foams in applications where fire safety is important. PMID:26287451

  7. Heat-mediated, ultra-rapid electrophoretic transfer of high and low molecular weight proteins to nitrocellulose membranes.

    PubMed

    Kurien, Biji T; Scofield, R Hal

    2002-08-01

    Here, we report an ultra-rapid method for the transfer of high and low molecular weight proteins to nitrocellulose membranes following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In this procedure, the electro-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 proteins (a purified protein, molecular weight protein standards and proteins from a human tissue extract) could be carried out in 10 min for a 0.75-mm, 7% SDS-PAGE gel. For 10% and 12.5% gels (0.75 mm), the corresponding time was 15 min. In the case of 1.5-mm gels, a complete transfer could be carried out in 20 min for 7%, 10% and 12.5% 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. When the heat-mediated transfer method was compared with a conventional transfer protocol, under similar conditions, we found that the latter method transferred minimal low molecular weight proteins while retaining most of the high molecular weight proteins in the gel. In summary, this procedure is very rapid, avoids the use of methanol and is particularly useful for the transfer of high molecular weight proteins.

  8. Effects of Molecular Weight upon Irradiation-Cross-Linked Poly(vinyl alcohol)/Clay Aerogel Properties.

    PubMed

    Chen, Hong-Bing; Zhao, Yan; Shen, Peng; Wang, Jun-Sheng; Huang, Wei; Schiraldi, David A

    2015-09-16

    Facile fabrication of mechanically strong poly(vinyl alcohol) (PVOH)/clay aerogel composites through a combination of increasing polymer molecular weights and gamma irradiation-cross-linking is reported herein. The aerogels produced from high polymer molecular weights exhibit significantly increased compressive moduli, similar to the effect of irradiation-induced cross-linking. The required irradiation dose for fabricating strong PVOH composite aerogels with dense microstructure decreased with increasing polymer molecular weight. Neither thermal stability nor flammability was significantly changed by altering the polymer molecular weight or by modest gamma irradiation, but they were highly dependent upon the polymer/clay ratio in the aerogel. Optimization of the mechanical, thermal, and flammability properties of these composite aerogels could therefore be obtained by using relatively low levels of polymer, with very high polymer molecular weight, or lower molecular weight coupled with moderate gamma irradiation. The facile preparation of strong, low flammability aerogels is an alternative to traditional polymer foams in applications where fire safety is important.

  9. Weak oligomerization of low-molecular-weight protein tyrosine phosphatase is conserved from mammals to bacteria.

    PubMed

    Blobel, Jascha; Bernadó, Pau; Xu, Huimin; Jin, Changwen; Pons, Miquel

    2009-08-01

    The well-characterized self-association of a mammalian low-molecular-weight protein tyrosine phosphatase (lmwPTP) produces inactive oligomers that are in equilibrium with active monomers. A role of the inactive oligomers as supramolecular proenzymes has been suggested. The oligomerization equilibrium of YwlE, a lmwPTP from Bacillus subtilis, was studied by NMR. Chemical shift data and NMR relaxation confirm that dimerization takes place through the enzyme's active site, and is fully equivalent to the dimerization previously characterized in a eukaryotic low-molecular-weight phosphatase, with similarly large dissociation constants. The similarity between the oligomerization of prokaryotic and eukaryotic phosphatases extends beyond the dimer and involves higher order oligomers detected by NMR relaxation analysis at high protein concentrations. The conservation across different kingdoms of life suggests a physiological role for lmwPTP oligomerization in spite of the weak association observed in vitro. Structural data suggest that substrate modulation of the oligomerization equilibrium could be a regulatory mechanism leading to the generation of signaling pulses. The presence of a phenylalanine residue in the dimerization site of YwlE, replacing a tyrosine residue conserved in all eukaryotic lmwPTPs, demonstrates that lmwPTP regulation by oligomerization can be independent from tyrosine phosphorylation.

  10. Analysis of low molecular weight metabolites in tea using mass spectrometry-based analytical methods.

    PubMed

    Fraser, Karl; Harrison, Scott J; Lane, Geoff A; Otter, Don E; Hemar, Yacine; Quek, Siew-Young; Rasmussen, Susanne

    2014-01-01

    Tea is the second most consumed beverage in the world after water and there are numerous reported health benefits as a result of consuming tea, such as reducing the risk of cardiovascular disease and many types of cancer. Thus, there is much interest in the chemical composition of teas, for example; defining components responsible for contributing to reported health benefits; defining quality characteristics such as product flavor; and monitoring for pesticide residues to comply with food safety import/export requirements. Covered in this review are some of the latest developments in mass spectrometry-based analytical techniques for measuring and characterizing low molecular weight components of tea, in particular primary and secondary metabolites. The methodology; more specifically the chromatography and detection mechanisms used in both targeted and non-targeted studies, and their main advantages and disadvantages are discussed. Finally, we comment on the latest techniques that are likely to have significant benefit to analysts in the future, not merely in the area of tea research, but in the analytical chemistry of low molecular weight compounds in general. PMID:24499071

  11. Insights into the toxicological properties of a low molecular weight fraction from Zoanthus sociatus (Cnidaria).

    PubMed

    Domínguez-Pérez, Dany; Diaz-Garcia, Carlos Manlio; García-Delgado, Neivys; Sierra-Gómez, Yusvel; Castañeda, Olga; Antunes, Agostinho

    2013-08-13

    The phylum Cnidaria is an ancient group of venomous animals, specialized in the production and delivery of toxins. Many species belonging to the class Anthozoa have been studied and their venoms often contain a group of peptides, less than 10 kDa, that act upon ion channels. These peptides and their targets interact with high affinity producing neurotoxic and cardiotoxic effects, and even death, depending on the dose and the administration pathway. Zoanthiniaria is an order of the Subclass Hexacorallia, class Anthozoa, and unlike sea anemone (order Actiniaria), neither its diversity of toxins nor the in vivo effects of the venoms has been exhaustively explored. In this study we assessed some toxicological tests on mice with a low molecular weight fraction obtained by gel filtration in Sephadex G-50 from Zoanthus sociatus crude extract. The gel filtration chromatogram at 280 nm revealed two major peaks, the highest absorbance corresponding to the low molecular weight fraction. The toxicological effects seem to be mostly autonomic and cardiotoxic, causing death in a dose dependent manner with a LD50 of 792 μg/kg. Moreover, at a dose of 600 μg/kg the active fraction accelerated the KCl-induced lethality in mice.

  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. Different molecular weight forms of opioid receptors revealed by polyclonal antibodies.

    PubMed

    Roy, S; Zhu, Y X; Lee, N M; Loh, H H

    1988-01-15

    Polyclonal antibodies were raised against a purified opioid receptor from bovine brain (Cho, et. al., 1986), and shown to inhibit 3H-diprenorphine binding to this receptor in a dose-dependent fashion. These antibodies were then used to characterize opioid-binding material present in rat brain and in NG108-15 neuroblastoma-glioma hybrid cells. Western blot analysis revealed that the antibodies reacted with a single species of 58,000 molecular weight in rat brain membranes; this closely corresponds in size to the bovine opioid receptor used to raise the antibodies. In contrast, the polyclonal antibodies reacted with a 45,000 molecular weight species in NG108-15 neuroblastoma-glioma hybrid cells; moreover, this band was specifically reduced in NG108-15 cells in which opioid receptors had been down-regulated by incubation with D-ala2-D-leu5-enkephalin for 24 hours. Thus at least two distinct opioid receptor molecules have been identified, which have antigenic similarities.

  14. Comparative wear tests of ultra-high molecular weight polyethylene and cross-linked polyethylene.

    PubMed

    Harsha, A P; Joyce, Tom J

    2013-05-01

    Wear particle-induced osteolysis is a major concern in hip implant failure. Therefore, recent research work has focussed on wear-resistant materials, one of the most important of which is cross-linked polyethylene. In view of this, the objective of this study was to compare the in vitro wear performance of cross-linked polyethylene to traditional ultra-high molecular weight polyethylene. In order to mimic appropriate in vivo conditions, a novel high-capacity wear tester called a circularly translating pin-on-disc was used. The results of this in vitro study demonstrated that the wear rate for cross-linked polyethylene was about 80% lower than that of conventional ultra-high molecular weight polyethylene. This difference closely matches in vivo results reported in the literature for total hip replacements that use the two biopolymers. The in vitro results were also verified against ASTM F732-00 (standard test method for wear testing of polymeric materials for use in total joint prostheses). The 50-station circularly translating pin-on-disc proved to be a reliable device for in vitro wear studies of orthopaedic biopolymers.

  15. Influence of the Molecular Weight and Charge of Antibiotics on Their Release Kinetics From Gelatin Nanospheres.

    PubMed

    Song, Jiankang; Odekerken, Jim C E; Löwik, Dennis W P M; López-Pérez, Paula M; Welting, Tim J M; Yang, Fang; Jansen, John A; Leeuwenburgh, Sander C G

    2015-07-01

    In this study, we investigated the fundamental relationship between the physicochemical characteristics of antibiotics and the kinetics of their release from gelatin nanospheres. We observed that antibiotics of high molecular weight (colistin and vancomycin) were released in a sustained manner from oppositely charged gelatin carriers for more than 14 d, as opposed to antibiotics of low molecular weight (gentamicin and moxifloxacin) which were released in a burst-like manner. The release kinetics of positively charged colistin strongly correlated with the rate of the enzymatic degradation of gelatin. To elucidate the differences among release kinetics of antibiotics, we explored the mechanism of interactions between antibiotics and gelatin nanospheres by monitoring the kinetics of release of antibiotics as a function of pH, ionic strength, and detergent concentrations. These studies revealed that the interactions between antibiotics and gelatin nanospheres were mainly dominated by (i) strong electrostatic forces for colistin; (ii) strong hydrophobic and electrostatic forces for vancomycin; (iii) weak electrostatic and hydrophobic forces for gentamicin; and (iv) weak hydrophobic forces for moxifloxacin. These results confirm that release of antibiotics from gelatin nanospheres strongly depends on the physicochemical characteristics of the antibiotics.

  16. Polyvinylpyrrolidone molecular weight controls silica shell thickness on Au nanoparticles with diglycerylsilane as precursor.

    PubMed

    Vanderkooy, Alan; Brook, Michael A

    2012-08-01

    Several strategies have been described for the preparation of silica-encapsulated gold nanoparticles (SiO(2)-AuNP), which typically suffer from an initial interface between gold and silica that is difficult to control, and layer thicknesses that are very sensitive to minor changes in silane concentration and incubation time. The silica shell thicknesses are normally equal to or larger than the gold particles themselves, which is disadvantageous when the particles are to be used for biodiagnostic applications. We present a facile and reproducible method to produce very thin silica shells (3-5 nm) on gold nanoparticles: the process is highly tolerant to changes in reaction conditions. The method utilized polyvinylpyrrolidone (PVP) of specific molecular weights to form the interface between gold and silica. The method further requires a nontraditional silica precursor, diglycerylsilane, which efficiently undergoes sol-gel processing at neutrality. Under these conditions, higher molecular weight PVP leads to thicker silica shells: PVP acts as the locus for silica growth into an interpenetrating organic-inorganic hybrid structure.

  17. Planar Microdevices Enhance Transport of Large Molecular Weight Molecules Across Retinal Pigment Epithelial Cells

    PubMed Central

    Wade, Jennifer S.; Desai, Tejal A.

    2014-01-01

    Large molecular weight drug delivery to the posterior eye is challenging due to cellular barriers that hinder drug transport. Understanding how to enhance transport across the retinal barrier is important for the design of new drug delivery systems. A novel mechanism to enhance drug transport is the use of geometric properties, which has not been extensively explored in the retina. Planar SU-8/ Poly(ethyleneglycol)dimethacrylate microdevices were constructed using photolithography to deliver FITC dextran across an in vitro retinal model. The model consists of retinal pigment epithelial (RPE) cells grown to confluence on transwell inserts, which provides an environment to investigate the influence of geometry on paracellular and transcellular delivery of encapsulated large molecules. Planar microdevices enhanced transport of large molecular weight dextrans across different models of RPE in a size dependent fashion. Increased drug permeation across the RPE was observed with the addition of microdevices as compared to a traditional bolus of FITC dextran. This phenomena was initiated by a non-toxic interaction between the microdevices and the retinal tight junction proteins. Suggesting that increased drug transport occurs via a paracellular pathway. These experiments provide evidence to support the future use of planar unidirectional microdevices for delivery of biologics in ocular applications. PMID:24789225

  18. Antiadhesion and antibiofilm activities of high molecular weight coffee components against Streptococcus mutans.

    PubMed

    Stauder, Monica; Papetti, Adele; Mascherpa, Dora; Schito, Anna Maria; Gazzani, Gabriella; Pruzzo, Carla; Daglia, Maria

    2010-11-24

    In previous studies we demonstrated that green and roasted coffee contains low molecular weight (LMW) compounds capable of inhibiting the ability of Streptococcus mutans, the major causative agent of human dental caries, to adhere to hydroxyapatite (HA) beads. This study addressed the ability of the whole high molecular weight coffee fraction (cHMW) and of its melanoidin and non-melanoidin components (GFC1-5), applied at concentrations that occur in coffee beverages, to (i) inhibit S. mutans growth; (ii) affect S. mutans sucrose-dependent adhesion to and detachment from saliva-coated HA beads (sHA); and (iii) inhibit biofilm development on microtiter plates. The results indicated that only cHMW is endowed with antimicrobial activity. The cHMW fraction and each of the five GFC components inhibited S. mutans adhesion, the strongest effect being exerted by cHMW (91%) and GFC1 (88%). S. mutans detachment from sHA was four times greater (∼20%) with cHMW and the GFC1 and GFC4 melanoidins than with controls. Finally, biofilm production by S. mutans was completely abolished by cHMW and was reduced by 20% by the melanoidin components GFC2 and GFC4 and by the non-melanoidin component GFC5 compared with controls. Altogether these findings show that coffee beverage contains both LMW compounds and HMW melanoidin and non-melanoidin components with a strong ability to interfere in vitro with the S. mutans traits relevant for cariogenesis. PMID:21038921

  19. 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.

  20. [Antibacterial effects of water-soluble low-molecular-weight chitosans on different microorganisms].

    PubMed

    Gerasimenko, D V; Avdienko, I D; Bannikova, G E; Zueva, O Iu; Varlamov, V P

    2004-01-01

    Low-molecular-weight chitosans with a viscosity-average molecular weight (Mv) of 5 to 27 kDa and equal degree of deacetylation (DD, 85%) were highly active against Pseudomonas aureofaciens, Enterobacter agglomerans, Bacillus subtilis, and Bifidobacterium bifidum 791, causing death of 80 to 100% of cells. An exception to this tendency was Escherichia coli, for which the rate of cell death, induced by the 5-kDa chitosan, was 38%. The antibacterial effect was manifested as early as 10 min after incubation of 12-kDa chitosan with B. subtilis or E. coli cells. Candida krusei was almost insensitive to the above crab chitosans. However, Candida krusei was highly sensitive to chitosans with Mv 5, 6, 12, 15.7, and 27 kDa: the minimum inhibitory concentration (MIC) varied from 0.06 to 0.005%. Chitosans with M, 5, 12, and 15.7 kDa exerted an antibacterial effect on Staphylococcus aureus. Chitosans with Mv 5, 15.7, and 27 kDa had no effect on Bifidobacterium bifidum ATCC 14893. The antibacterial effect of the 4-kDa chitosan on E. coli and B. bifidum 791 increased with DD in the range 55-85%.

  1. Wheat gluten: high molecular weight glutenin subunits--structure, genetics, and relation to dough elasticity.

    PubMed

    Anjum, Faqir Muhammad; Khan, Moazzam Rafiq; Din, Ahmad; Saeed, Muhammad; Pasha, Imran; Arshad, Muhammad Umair

    2007-04-01

    Gluten proteins, representing the major protein fraction of the starchy endosperm, are predominantly responsible for the unique position of wheat amongst cereals. These form a continuous proteinaceous matrix in the cells of the mature dry grain and form a continuous viscoelastic network during the mixing process of dough development. These viscoelastic properties underline the utilization of wheat to prepare bread and other wheat flour based foodstuffs. One group of gluten proteins is glutenin, which consists of high molecular weight (HMW) and low molecular weight (LMW) subunits. The HMW glutenin subunits (HMW-GS) are particularly important for determining dough elasticity. The common wheat possesses 3 to 5 HMW subunits encoded at the Glu-1 loci on the long arms of group 1 chromosomes (1A, 1B, and 1D). The presence of certain HMW subunits is positively correlated with good bread-making quality. Glutamine-rich repetitive sequences that comprise the central part of the HMW subunits are actually responsible for the elastic properties due to extensive arrays of interchain hydrogen bonds. Genetic engineering can be used to manipulate the amount and composition of the HMW subunits, leading to either increased dough strength or more drastic changes in gluten structure and properties.

  2. 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.

  3. 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.

  4. Molecular-weight-dependent changes in morphology of solution-grown polyethylene single crystals.

    PubMed

    Zhang, Bin; Chen, Jingbo; Baier, Moritz C; Mecking, Stefan; Reiter, Renate; Mülhaupt, Rolf; Reiter, Günter

    2015-01-01

    Polymer single crystals consisting of folded chains are always in a nonequilibrium state, even if they are faceted with a well-defined envelope reflecting the parameters of the crystal unit cell. Heterogeneities like small variations in the degree of chain folding within such crystals are responsible for a rather broad range in melting temperature. Consequently, upon annealing at a given temperature, some parts may be above and some below their respective melting temperatures, inducing a lamellar thickening process, which may vary locally. To emphasize such variations, controlled annealing experiments are performed at comparatively low temperatures and for long times. For single crystals of low-molecular-weight polyethylene, the formation of the well-known "Swiss-cheese"-like morphology with randomly distributed holes of varying sizes within the annealed single crystal is observed. However, for high-molecular-weight polyethylene, a regular pattern appeared upon annealing, characterized by branches of equal width that are oriented perpendicular to the crystal edge. All branches end at the nucleation site. Interestingly, the resulting pattern depends sensitively on both crystallization and annealing conditions. These thermally induced regular patterns within a single crystal are attributed to a stable crystalline framework formed within polyethylene single crystals in the course of growth.

  5. 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.

  6. Structure of DPPC-hyaluronan interfacial layers - effects of molecular weight and ion composition.

    PubMed

    Wieland, D C Florian; Degen, Patrick; Zander, Thomas; Gayer, Sören; Raj, Akanksha; An, Junxue; Dėdinaitė, Andra; Claesson, Per; Willumeit-Römer, Regine

    2016-01-21

    Hyaluronan and phospholipids play an important role in lubrication in articular joints and provide in combination with glycoproteins exceptionally low friction coefficients. We have investigated the structural organization of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) Langmuir layers at the solution-air interface at different length scales with respect to the adsorption of hyaluronan (HA). This allows us to assemble a comprehensive picture of the adsorption and the resulting structures, and how they are affected by the molecular weight of HA and the presence of calcium ions. Brewster angle microscopy and grazing incident diffraction were used to determine the lateral structure at the micro- and macro scale. The data reveals an influence of HA on both the macro and micro structure of the DPPC Langmuir layer, and that the strength of this effect increases with decreasing molecular weight of HA and in presence of calcium ions. Furthermore, from X-ray reflectivity measurements we conclude that HA adsorbs to the hydrophilic part of DPPC, but data also suggest that two types of interfacial structures are formed at the interface. We argue that hydrophobic forces and electrostatic interactions play important rules for the association between DPPC and HA. Surface pressure area isotherms were used to determine the influence of HA on the phase behavior of DPPC while electrophoretic mobility measurements were used to gain insight into the binding of calcium ions to DPPC vesicles and hyaluronan.

  7. Anti-heparanase activity of ultra-low-molecular-weight heparin produced by physicochemical depolymerization.

    PubMed

    Achour, Oussama; Poupard, Nicolas; Bridiau, Nicolas; Bordenave Juchereau, Stephanie; Sannier, Fredéric; Piot, Jean-Marie; Fruitier Arnaudin, Ingrid; Maugard, Thierry

    2016-01-01

    Heparanase is an endo-β-D-glucuronidase that plays an important role in cancer progression, in particular during tumor angiogenesis and metastasis. Inhibiting this enzyme is considered as one of the most promising approaches in cancer therapy. Heparin is a complex glycoaminoglycan known as a strong inhibitor of heparanase. It is primarily used in clinical practice for its anticoagulant activities, which may not be compatible with its use as anti-angiogenic agent. In this study, we described the production of ultra-low-molecular-weight heparins (ULMWH) by a physicochemical method that consists in a hydrogen peroxide-catalyzed radical hydrolysis assisted by ultrasonic waves. We assessed the structural characteristics, anticoagulant and anti-heparanase activities of the obtained heparin derivatives and compared them with three commercial low-molecular-weight heparins (LMWH), glycol-split non-anticoagulant heparins and heparins produced by enzymatic methods. ULMWH generated by the physicochemical method were characterized by high anti-heparanase and moderate anticoagulant activities. These heparin derivatives might be potential candidates for cancer therapy when a compromise is needed between anti-heparanase and anticoagulant activities.

  8. 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.

  9. Structure and activity of a new low-molecular-weight heparin produced by enzymatic ultrafiltration.

    PubMed

    Fu, Li; Zhang, Fuming; Li, Guoyun; Onishi, Akihiro; Bhaskar, Ujjwal; Sun, Peilong; Linhardt, Robert J

    2014-05-01

    The standard process for preparing the low-molecular-weight heparin (LMWH) tinzaparin, through the partial enzymatic depolymerization of heparin, results in a reduced yield because of the formation of a high content of undesired disaccharides and tetrasaccharides. An enzymatic ultrafiltration reactor for LMWH preparation was developed to overcome this problem. The behavior, of the heparin oligosaccharides and polysaccharides using various membranes and conditions, was investigated to optimize this reactor. A novel product, LMWH-II, was produced from the controlled depolymerization of heparin using heparin lyase II in this optimized ultrafiltration reactor. Enzymatic ultrafiltration provides easy control and high yields (>80%) of LMWH-II. The molecular weight properties of LMWH-II were similar to other commercial LMWHs. The structure of LMWH-II closely matched heparin's core structural features. Most of the common process artifacts, present in many commercial LWMHs, were eliminated as demonstrated by 1D and 2D nuclear magnetic resonance spectroscopy. The antithrombin III and platelet factor-4 binding affinity of LMWH-II were comparable to commercial LMWHs, as was its in vitro anticoagulant activity.

  10. Assessment of molecular weight distribution of wheat gluten proteins for chapatti quality.

    PubMed

    Chaudhary, Nisha; Dangi, Priya; Khatkar, Bhupendar Singh

    2016-05-15

    Size exclusion chromatography (SEC) was used to characterize molecular weight distribution pattern of gluten proteins of four Indian commercial wheat varieties in order to elucidate their influence on flour physicochemical, dough rheology and quality characteristics of chapatti. SEC profile of a wheat variety was segregated into five domains: peak I (130-30 kDa; glutenins), peak II (55-20 kDa; gliadins), peak III (28-10 kDa; low molecular weight gliadins), peak IV and V (<10 kDa; albumins and globulins). SEC results indicated that R/E ratio (r=0.745(∗∗) and r=-0.869(∗∗)), gluten index (r=0.959(∗∗) and r=-0.994(∗∗)), dough development time (r=0.830(∗∗) and r=-0.930(∗∗)) and dough stability (r=0.901(∗∗) and r=-0.979(∗∗)) were positively and negatively altered by peak I and II, respectively. Peak I (r=0.879(∗∗) and r=-0.981(∗∗)) and peak II (r=-0.744(∗∗) and r=0.995(∗∗)) substantially influenced the chapatti hardness and overall score, respectively.

  11. 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.

  12. 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.

  13. Variable Production of English Past Tense Morphology: A Case Study of a Thai-Speaking Learner of English

    ERIC Educational Resources Information Center

    Prapobaratanakul, Chariya; Pongpairoj, Nattama

    2016-01-01

    The study investigated variable production of English past tense morphology by an L1 Thai-speaking learner of English. Due to the absence of the past tense inflectional morphology in the Thai language, production of English past tense morphemes poses a persistent problem for L1 Thai-speaking learners of English. Hypotheses have been made in…

  14. Tense and agreement impairment in Ibero-Romance.

    PubMed

    Gavarró, Anna; Martínez-Ferreiro, Silvia

    2007-01-01

    We examine the inflectional productions of seven Catalan, seven Galician, and seven Spanish speaking agrammatic subjects in an elicitation and a sentence repetition task and consider them in the light of the Tree Pruning Hypothesis (TPH). The results show relatively spared subject person/number agreement with the verb and impaired tense marking for all subjects in all the languages. Recent reformulations of syntactic theory [Chomsky (1999) MIT Occasional Papers in Linguistics (vol. 18). MA: The MIT Press; (2000). Step by Step: Essays on Minimalist Syntax in Honor of Howard Lasnik (pp. 89-155). Cambridge, MA: The MIT Press] regarding the locus of agreement force a reconsideration of the TPH for it to make the desired predictions; we adopt Cinque's [(1999) Adverbs and Functional Heads: A Cross-linguistic Perspective. Oxford: Oxford University Press] array of functional mood/tense/aspect projections and we show that subject agreement must occur between the subject DP and a low functional head for selective impairment to result. Feature underspecification, formerly considered, is rendered unnecessary.

  15. The Role of Meaning in Past-Tense Inflection

    PubMed Central

    Bandi-Rao, Shoba; Murphy, Gregory L.

    2009-01-01

    Although English verbs can be either regular (walk-walked) or irregular (sing-sang), “denominal verbs” that are derived from nouns, such as the use of the verb ring derived from the noun a ring, take the regular form even if they are homophonous with an existing irregular verb: The soldiers ringed the city rather than *The soldiers rang the city. Is this regularization due to a semantic difference from the usual verb, or is it due to the application of the default rule, namely VERB + -ed suffix? In Experiment 1, participants rated the semantic similarity of the extended senses of polysemous verbs and denominal verbs to their central senses. Experiment 2 examined the acceptability of the regular and irregular past-tenses of the different verbs. The results showed that all the denominal verbs were rated as more acceptable for the regular inflection than the same verbs used polysemously, even though the two were semantically equally similar to the central meaning. Thus, the derivation of the verb (nominal or verbal) determined the past-tense preference more than semantic variables, consistent with dual-route models of verb inflection. PMID:16839538

  16. Unified wear model for highly crosslinked ultra-high molecular weight polyethylenes (UHMWPE).

    PubMed

    Muratoglu, O K; Bragdon, C R; O'Connor, D O; Jasty, M; Harris, W H; Gul, R; McGarry, F

    1999-08-01

    Crosslinking has been shown to improve the wear resistance of ultra-high molecular weight polyethylene in both in vitro and clinical in vivo studies. The molecular mechanisms and material properties that are responsible for this marked improvement in wear resistance are still not well understood. In fact, following crosslinking a number of mechanical properties of UHMWPE are decreased including toughness, modulus, ultimate tensile strength, yield strength, and hardness. In general, these changes would be expected to constitute a precursor for lower wear resistance, presenting a paradox in that wear resistance increases with crosslinking. In order to understand better and to analyze this paradoxical behaviour of crosslinked UHMWPE, we investigated the wear behavior of (i) radiation-crosslinked GUR 1050 resin, (ii) peroxide-crosslinked GUR 1050 resin and (iii) peroxide-crosslinked Himont 1900 resin using a bi-directional pin-on-disk (POD) machine. Wear behavior was analyzed as a function of crystallinity, ultimate tensile strength (UTS), yield strength (YS), and molecular weight between crosslinks (Mc). The crosslink density increased with increasing radiation dose level and initial peroxide content. The UTS, YS, and crystallinity decreased with increasing crosslink density. While these variations followed the same trend, the absolute changes as a function of crosslink density were different for the three types of crosslinked UHMWPE studied. There was no unified correlation for the wear behavior of the three types of crosslinked UHMWPE with the crystallinity, UTS and YS. However, the POD wear rate showed the identical linear dependence on Mc with all three types of crosslinked UHMWPEs studied. Therefore, we have strong evidence to propose that Mc or crosslink density is a fundamental material property that governs the lubricated adhesive and abrasive wear mechanisms of crosslinked UHMWPEs, overriding the possible effects of other material properties such as UTS, YS

  17. Phylogenetical and ontogenetical studies on the molecular weight heterogeneity of bovine serum transferrin.

    PubMed

    Tsuji, S; Kato, H; Matsuoka, Y; Fukushima, T; Nanjoh, I; Amano, T; Namikawa, T

    1984-12-01

    Antitransferrin (Tf) rabbit serum was highly specific: it reacted with Tfs of ruminants, such as European breeds and Zebu breeds of cattle, Bali cattle, banteng, swamp and river types of water buffalo, anoa, goat, sheep, deer, antelope, camel, and giraffe, but did not react with serum of other non-ruminant species, such as pig, wild boar, hippopotamus, horse, rabbit, rat, chicken, etc. Electrophoresis of Tf and immunoglobulin G (IgG) complexes was carried out using sodium dodecyl sulfate--polyacrylamide gel electrophoresis (SDS-PAGE). Within ruminants, the following species showed two Tf molecules on SDS-PAGE; European and Zebu cattle, Bali cattle, banteng, two types of water buffalo, and two species of anoa. Other ruminants, sheep, goat, deer, antelope, camel, and giraffe, etc., showed only one Tf molecule. The Tf heterogeneity in molecular weight was, thus, restricted to Bos, Bubalus, and Anoa. The molecular weight of Tf of water buffalo was slightly larger than that of cattle on the gel. The peptide pattern from cyanogen bromide cleavage of Tf of the water buffalo differed clearly from that of cattle. Fetal Tf showed only one molecule during development, but a newborn calf has two Tf molecules, (one large and one small) within 18 hr after birth. We suggest, therefore, that the small molecules formed during the last month of gestation. The peptide patterns of adult and fetal Tfs cleaved by cyanogen bromide differed with regard to the two large peptides; fetal Tf, lacking the second-largest peptide, had twice the amount of the largest peptide compared with adult Tf. From these results, we suggest that a change in peptide sequence occurs from the last month of gestation, when the largest peptide is degraded to the second largest. However, a Tf-like protein detected in the liver microsomal fraction has only one molecular size, both in adult and in fetal livers.

  18. Sucrose crystal growth in the presence of dextran of different molecular weights

    NASA Astrophysics Data System (ADS)

    Khaddour, Issam; Ferreira, António; Bento, Luís; Rocha, Fernando

    2012-09-01

    The effects of variable concentrations of different molecular weight fractions of dextran on the interfacial free energies and the kinetic coefficients of the overall linear growth rates of the sucrose crystal were evaluated at 40 and 50 °C. Dextrans-reducing effects on the interfacial free energy increased the overall linear growth rates of sucrose at 40 °C. Further, dextrans-reducing effects of the growth kinetic coefficients resulted in lower growth rates of the sucrose crystals at 50 °C. Impurity effectiveness factor, differential heat of adsorption and Langmuir isotherm constant were determined, for the used dextrans, at 50 °C and relative supersaturation of 0.161. The dextran of molecular fraction of 2000 kilo Daltons (kDa) showed considerably high effectiveness factor in comparison with the dextrans of molecular fractions of 70 and 250 kDa. Role of dextran in retarding the advancement of the growth steps in the vicinity of its incorporation on the face (100) of the sucrose crystal is pointed out using AFM technique.

  19. Low-molecular-weight polyethylenimine enhanced gene transfer by cationic cholesterol-based nanoparticle vector.

    PubMed

    Hattori, Yoshiyuki; Maitani, Yoshie

    2007-09-01

    Both polyethylenimine (PEI) polymers and cationic nanoparticles have been widely used for non-viral DNA transfection. Previously, we reported that cationic nanoparticles composed of cholesteryl-3beta-carboxyamidoethylene-N-hydroxyethylamine and Tween 80 (NP-OH) could deliver plasmid DNA (pDNA) with high transfection efficiency. To increase the transfection activity of NP-OH, we investigated the potential synergism of PEI and NP-OH for the transfection of DNA into human prostate tumor PC-3, human cervices tumor Hela, and human lung adenocarcinoma A549 cells. The transfection efficiency with low-molecular PEI (MW 600) was low, but that with a combination of NP-OH and PEI was higher than with NP-OH alone, being comparable to commercially available lipofectamine 2,000 and lipofectamine LTX, with very low cytotoxicity. Low-molecular weight PEI could not compact pDNA in size, but rather might help to dissociate pDNA from the complex and release pDNA from the endosome to cytoplasm by the proton sponge effect. Therefore, the combination of cationic cholesterol-based nanoparticles and a low-molecular PEI has potential as a non-viral DNA vector for gene delivery.

  20. Micropatterning of small molecular weight organic semiconductor thin films using organic vapor phase deposition

    NASA Astrophysics Data System (ADS)

    Shtein, Max; Peumans, Peter; Benziger, Jay B.; Forrest, Stephen R.

    2003-04-01

    Using both analytical and experimental methods, we show that micron scale patterned growth of small molecular weight organic semiconductor thin films can be achieved by the recently demonstrated process of organic vapor phase deposition (OVPD). In contrast to the conventional process of vacuum thermal evaporation, the background gas pressure during OVPD is typically 0.1-10 Torr, resulting in a molecular mean free path (mfp) of from 100 to 1 μm, respectively. Monte Carlo simulations of film growth through apertures at these gas densities indicate that when the mfp is on the order of the mask-to-substrate separation, deposit edges can become diffuse. The simulations and deposition experiments discussed here indicate that the deposited feature shape is controlled by the mfp, the aperture geometry, and the mask-to-substrate separation. Carefully selected process conditions and mask geometries can result in features as small as 1 μm. Furthermore, based on continuum and stochastic models of molecular transport in confined geometries, we propose the in situ direct patterning growth technique of organic vapor jet printing. The high pattern definition obtained by OVPD makes this process attractive for the growth of a wide range of structures employed in modern organic electronic devices.

  1. Fluid composition impacts standardized testing protocols in ultrahigh molecular weight polyethylene knee wear testing.

    PubMed

    Schwenke, T; Kaddick, C; Schneider, E; Wimmer, M A

    2005-11-01

    Wear of total knee replacements is determined gravimetrically in simulator studies. A mix of bovine serum, distilled water, and additives is intended to replicate the lubrication conditions in vivo. Weight gain due to fluid absorption during testing is corrected using a load soak station. In this study, three sets of ultrahigh molecular weight polyethylene tibial plateau were tested against highly polished titanium condyles. Test 1 was performed in two different institutions on the same simulator according to the standard ISO 14243-1, using two testing lubricants. Test 2 and test 3 repeated both previous test sections. The wear and load soak rates changed significantly with the lubricant. The wear rate decreased from 16.9 to 7.9 mg weight loss per million cycles when switching from fluid A to fluid B. The weight gain of the load soak specimen submersed in fluid A was 6.1 mg after 5 x 10(6) cycles, compared with 31.6 mg for the implant in fluid B after the same time period. Both lubricants were mixed in accordance with ISO 14243 (Implants for surgery - wear of total knee-joint prostheses), suggesting that calf serum should be diluted to 25 +/- 2 per cent with deionized water and a protein mass concentration of not less than 17 g/l. The main differences were the type and amount of additives that chemically stabilize the lubricant throughout the test. The results suggest that wear rates can only be compared if exactly the same testing conditions are applied. An agreement on detailed lubricant specifications is desirable.

  2. 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.

  3. Hydrodynamic force depends not only on the viscosity of solution but also on the molecular weights of viscogens.

    PubMed

    Lv, Chunmei; Zou, Dawei; Qin, Meng; Meng, Wei; Cao, Yi; Wang, Wei

    2013-08-27

    Many cellular processes, such as the diffusion of biomacromolecules, the movement of molecular motors, and the conformational dynamics of proteins, are subjected to hydrodynamic forces because of the high viscosities of cellular environments. However, it is still unknown how hydrodynamic forces are related to the physical properties of different viscogens. Here, using the atomic force microscope-based force spectroscopy technique, we directly measured the hydrodynamic forces acting on a moving cantilever in various viscogen solutions. We found that the hydrodynamic force is not only dependent on the viscosity but also related to the molecular weight of viscogens. Counterintuitively, at the same macroscopic viscosity, the hydrodynamic force rises with the increasing molecular weight of viscogens, although the local microscopic viscosity of the solution decreases. This finding provides insights into the origin of hydrodynamic forces in biomolecule solutions and could inspire many force-spectroscopy-based techniques to measure the molecular weight and conformational changes of biomacromolecules in biological settings directly.

  4. 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.

  5. Hydrodynamic force depends not only on the viscosity of solution but also on the molecular weights of viscogens.

    PubMed

    Lv, Chunmei; Zou, Dawei; Qin, Meng; Meng, Wei; Cao, Yi; Wang, Wei

    2013-08-27

    Many cellular processes, such as the diffusion of biomacromolecules, the movement of molecular motors, and the conformational dynamics of proteins, are subjected to hydrodynamic forces because of the high viscosities of cellular environments. However, it is still unknown how hydrodynamic forces are related to the physical properties of different viscogens. Here, using the atomic force microscope-based force spectroscopy technique, we directly measured the hydrodynamic forces acting on a moving cantilever in various viscogen solutions. We found that the hydrodynamic force is not only dependent on the viscosity but also related to the molecular weight of viscogens. Counterintuitively, at the same macroscopic viscosity, the hydrodynamic force rises with the increasing molecular weight of viscogens, although the local microscopic viscosity of the solution decreases. This finding provides insights into the origin of hydrodynamic forces in biomolecule solutions and could inspire many force-spectroscopy-based techniques to measure the molecular weight and conformational changes of biomacromolecules in biological settings directly. PMID:23944228

  6. 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

  7. Surface engineering on mesoporous silica chips for enriching low molecular weight phosphorylated proteins

    NASA Astrophysics Data System (ADS)

    Hu, Ye; Peng, Yang; Lin, Kevin; Shen, Haifa; Brousseau, Louis C., III; Sakamoto, Jason; Sun, Tong; Ferrari, Mauro

    2011-02-01

    Phosphorylated peptides and proteins play an important role in normal cellular activities, e.g., gene expression, mitosis, differentiation, proliferation, and apoptosis, as well as tumor initiation, progression and metastasis. However, technical hurdles hinder the use of common fractionation methods to capture phosphopeptides from complex biological fluids such as human sera. Herein, we present the development of a dual strategy material that offers enhanced capture of low molecular weight phosphoproteins: mesoporous silica thin films with precisely engineered pore sizes that sterically select for molecular size combined with chemically selective surface modifications (i.e. Ga3+, Ti4+ and Zr4+) that target phosphoroproteins. These materials provide high reproducibility (CV = 18%) and increase the stability of the captured proteins by excluding degrading enzymes, such as trypsin. The chemical and physical properties of the composite mesoporous thin films were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and ellipsometry. Using mass spectroscopy and biostatistics analysis, the enrichment efficiency of different metal ions immobilized on mesoporous silica chips was investigated. The novel technology reported provides a platform capable of efficiently profiling the serum proteome for biomarker discovery, forensic sampling, and routine diagnostic applications.Phosphorylated peptides and proteins play an important role in normal cellular activities, e.g., gene expression, mitosis, differentiation, proliferation, and apoptosis, as well as tumor initiation, progression and metastasis. However, technical hurdles hinder the use of common fractionation methods to capture phosphopeptides from complex biological fluids such as human sera. Herein, we present the development of a dual strategy material that offers enhanced capture of low molecular weight phosphoproteins: mesoporous

  8. Toxicological Evaluation of Low Molecular Weight Fucoidan in Vitro and in Vivo

    PubMed Central

    Hwang, Pai-An; Yan, Ming-De; Lin, Hong-Ting Victor; Li, Kuan-Lun; Lin, Yen-Chang

    2016-01-01

    For a long time, fucoidan has been well known for its pharmacological activities, and recently low molecular weight fucoidan (LMF) has been used in food supplements and pharmaceutical products. In the present study, LMF was extracted from Laminaria japonica by enzyme hydrolysis. The toxicity of LMF in mouse and rat models was determined by many methods, such as total arsenic content, bacterial reverse mutation assay, chromosome aberration assay, and in vivo micronucleus assay. The present findings showed that LMF at 5000 μg/mL exhibited no mutagenicity. It also produced no formatting disruption of red blood cells in vivo. At 2000 mg/kg BW/day there were no toxicological indications. LMF is expected to be used as a safe food supplement. PMID:27347980

  9. 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.

  10. 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.

  11. Skin: Major target organ of allergic reactions to small molecular weight compounds

    SciTech Connect

    Merk, Hans F. Baron, Jens M.; Neis, Mark M.; Obrigkeit, Daniela Hoeller; Karlberg, Ann-Therese

    2007-11-01

    Skin is a major target organ for allergic reactions to small molecular weight compounds. Drug allergic reactions may be life-threatening such as in the case of anaphylactic reactions or bullous drug reactions and occur in about 5% of all hospitalized patients. Allergic contact dermatitis has an enormous influence on the social life of the patient because it is the most frequent reason for occupational skin diseases and the treatment and prevention of this disease cost approximately Euro 3 billion per year in Germany. The different proposed pathophysiological pathways leading to a drug eruption are discussed in this paper. All major enzymes which are involved in the metabolism of xenobiotica were shown to be present in skin. Evidence supporting the role of metabolism in the development of drug allergy and allergic contact dermatitis is demonstrated in the example of sulphonamides and fragrances.

  12. High performance carbon fibers from very high molecular weight polyacrylonitrile precursors

    DOE PAGESBeta

    Morris, E. Ashley; Weisenberger, Matthew C.; Abdallah, Mohamed G.; Vautard, Frederic; Grappe, Hippolyte A.; Ozcan, Soydan; Paulauskas, Felix L.; Eberle, Cliff; Jackson, David C.; Mecham, Sue J.; et al

    2016-02-02

    In this study, carbon fibers are unique reinforcing agents for lightweight composite materials due to their outstanding mechanical properties and low density. Current technologies are capable of producing carbon fibers with 90-95% of the modulus of perfect graphite (~1025 GPa). However, these same carbon fibers possess less than 10% of the theoretical carbon fiber strength, estimated to be about 100 GPa.[1] Indeed, attempts to increase carbon fiber rigidity results in lower breaking strength. To develop advanced carbon fibers with both very high strength and modulus demands a new manufacturing methodology. Here, we report a method of manufacturing high strength, verymore » high modulus carbon fibers from a very high molecular weight (VHMW) polyacrylonitrile (PAN) precursor without the use of nanomaterial additives such as nucleating or structure-templating agents, as have been used by others.[2,3]« less

  13. Liquid alkanes with targeted molecular weights from biomass-derived carbohydrates.

    PubMed

    West, Ryan M; Liu, Zhen Y; Peter, Maximilian; Dumesic, James A

    2008-01-01

    Liquid transportation fuels must burn cleanly and have high energy densities, criteria that are currently fulfilled by petroleum, a non-renewable resource, the combustion of which leads to increasing levels of atmospheric CO(2). An attractive approach for the production of transportation fuels from renewable biomass resources is to convert carbohydrates into alkanes with targeted molecular weights, such as C(8)-C(15) for jet-fuel applications. Targeted n-alkanes can be produced directly from fructose by an integrated process involving first the dehydration of this C(6) sugar to form 5-hydroxymethylfurfural, followed by controlled formation of C-C bonds with acetone to form C(9) and C(15) compounds, and completed by hydrogenation and hydrodeoxygenation reactions to form the corresponding n-alkanes. Analogous reactions are demonstrated starting with 5-methylfurfural or 2-furaldehyde, with the latter leading to C(8) and C(13) n-alkanes. PMID:18702136

  14. 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.

  15. Low molecular weight fucoidan modulates P-selectin and alleviates diabetic nephropathy.

    PubMed

    Xu, Yingjie; Zhang, Quanbin; Luo, Dali; Wang, Jing; Duan, Delin

    2016-10-01

    Diabetic nephropathy (DN) is a serious microvascular complication that can lead to chronic and end-stage renal failure. It is understood that inflammation is associated with the onset and process of DN. Low molecular weight fucoidan (LMWF) isolated from Saccharina japonica has anti-inflammatory properties. Therefore, this study aimed to explore the mechanism of LMWF in DN model induced by streptozotocin. The biochemical indices levels showed LMWF reduced the DN diagnostic indices to protect renal function. The HE stained sections exhibited LMWF protected normal morphological structures and reduced inflammatory cell infiltration in the kidneys of DN rats. Furthermore, the levels of P-selectin and selectin-dependent inflammatory cytokines resulting from LMWF were obviously decreased at both the transcriptional and protein levels. Thus, our results found that LMWF protected the renal function in DN rats and alleviated inflammation through the modulation of P-selectin and inflammatory cytokines. LMWF may have therapeutic potential against DN. PMID:27234491

  16. Synthesis of high molecular weight polyesters via in vacuo dehydrogenation polymerization of diols.

    PubMed

    Hunsicker, David M; Dauphinais, Brian C; Mc Ilrath, Sean P; Robertson, Nicholas J

    2012-02-13

    The Milstein catalyst has proven to be highly effective for the conversion of alcohols to esters, as well as alcohols and amines to amides and polyamides. We have recently found that the catalyst's range can be extended to very efficient in vacuo dehydrogenation polymerization of α,ω-diols to generate polyesters. The gaseous hydrogen byproduct that is produced is easily removed to drive the equilibrium toward product, which leads to the formation of high molecular weight polymer (M(n) up to 145,000 g mol(-1)). This optimized methodology works well to polymerize diols with a spacer of six carbons or more. Diols with fewer carbons are cyclized to lactone; the dividing point is the dehydrogenation of 1,5-pentanediol, which leads to a mixture of polyester and lactone. Reported herein is the synthesis and characterization of five aliphatic polyesters prepared via this novel dehydrogenation polymerization approach. PMID:22173989

  17. Sorption of copper onto low molecular weight chitosan derivative from aqueous solution.

    PubMed

    Boamah, Peter Osei; Huang, Yan; Hua, Mingqing; Onumah, Jacqueline; Sam-Amoah, Livingstone K; Boamah, Paul Osei; Qian, Yaao; Zhang, Qi

    2016-07-01

    In this study, sorption of copper onto low molecular weight chitosan derivative was studied. Experimental parameters such as pH of the solution (A), temperature (B), dose of the sorbent (C), and concentration of solution (D) were considered. The statistical results indicated that the dose of sorbent (C) and Cu (II) concentration (D) influenced removal efficiency at 5% significance level. Also, some interactions such as ABCD, ACD, ABC and AC affected the removal process. The sorbent was characterized with FTIR, SEM and TG/DSC. Freundlich isotherm model was the best isotherm model. The kinetic study results correlated well with the pseudo-second-order model. The thermodynamic studies revealed that the nature of copper sorption was spontaneous and endothermic. Strong affinity of the sorbent for copper (II) was revealed by the Isothermal Titration Calorimetry (ITC) technique. PMID:27039244

  18. [Antibacterial Activity of Alkylated and Acylated Derivatives of Low-Molecular Weight Chitosan].

    PubMed

    Shagdarova, B Ts; Il'ina, A V; Varlamov, V P

    2016-01-01

    A number of alkylated (quaternized) and acylated derivatives of low-molecular weight chitosan were obtained. The structure and composition of the compounds were confirmed by the results of IR and PMR spectroscopy, as well as conductometric titration. The effect of the acyl substituent and the degree of substitution of N-(2-hydroxy-3-trimethylammonium) with the propyl fragment appended to amino groups of the C2 atom of polymer chains on antibacterial activity against typical representatives of gram-positive and gram-negative microorganisms (Staphylococcus epidermidis and Escherichia coli) was studied. The highest activity was in the case of N-[(2-hydroxy-3-trimethylammonium)propyl]chitosan chloride with the maximal substitution (98%). The minimal inhibitory concentration of the derivative was 0.48 µg/mL and 3.90 µg/mL for S. epidermis and E. coli, respectively. PMID:27266254

  19. Kinetics of enzymatic starch liquefaction: simulation of the high molecular weight product distribution

    SciTech Connect

    Rollings, J.E.; Thompson, R.W.

    1984-12-01

    Enzymatic corn starch liquefaction with alpha-amylase was carried out. Molecular weight distributions of the resulting hydrolysates are presented using aqueous size exclusion chromatographic techniques. It is demonstrated that despite the fact that the enzyme employed reacts in a random endoacting manner, the product distributions are nonrandom. The results are explained in part by a multimerization process whereby the polymeric substrate molecules preferentially associate, forming intermolecular aggregates. These aggregates are either a consequence of the manner in which the material is deposited into the native granular structure of starch or due to intrinsic physical chemical properties of the polysaccharide. In the latter case, the results are shown to correspond to known multimerized amylose, although complete characterization of the polysaccharide is currently not available. The results presented are used to develop a simplified kinetic model of starch liquefaction and shown to simulate the product distributions accurately. 44 references.

  20. Toxicological Evaluation of Low Molecular Weight Fucoidan in Vitro and in Vivo.

    PubMed

    Hwang, Pai-An; Yan, Ming-De; Lin, Hong-Ting Victor; Li, Kuan-Lun; Lin, Yen-Chang

    2016-01-01

    For a long time, fucoidan has been well known for its pharmacological activities, and recently low molecular weight fucoidan (LMF) has been used in food supplements and pharmaceutical products. In the present study, LMF was extracted from Laminaria japonica by enzyme hydrolysis. The toxicity of LMF in mouse and rat models was determined by many methods, such as total arsenic content, bacterial reverse mutation assay, chromosome aberration assay, and in vivo micronucleus assay. The present findings showed that LMF at 5000 μg/mL exhibited no mutagenicity. It also produced no formatting disruption of red blood cells in vivo. At 2000 mg/kg BW/day there were no toxicological indications. LMF is expected to be used as a safe food supplement. PMID:27347980

  1. Skin: major target organ of allergic reactions to small molecular weight compounds.

    PubMed

    Merk, Hans F; Baron, Jens M; Neis, Mark M; Obrigkeit, Daniela Höller; Karlberg, Ann-Therese

    2007-11-01

    Skin is a major target organ for allergic reactions to small molecular weight compounds. Drug allergic reactions may be life-threatening such as in the case of anaphylactic reactions or bullous drug reactions and occur in about 5% of all hospitalized patients. Allergic contact dermatitis has an enormous influence on the social life of the patient because it is the most frequent reason for occupational skin diseases and the treatment and prevention of this disease cost approximately euro 3 billion per year in Germany. The different proposed pathophysiological pathways leading to a drug eruption are discussed in this paper. All major enzymes which are involved in the metabolism of xenobiotica were shown to be present in skin. Evidence supporting the role of metabolism in the development of drug allergy and allergic contact dermatitis is demonstrated in the example of sulphonamides and fragrances.

  2. 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

  3. Friction, wear, transfer and wear surface morphology of ultra-high-molecular-weight polyethylene

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1983-01-01

    Tribological studies at 25 C in a 50-percent-relative-humidity air atmosphere were conducted using hemispherically tipped 440 C HT (high temperature) stainless steel pins sliding against ultra-high-molecular-weight polyethylene (UHMWPE) disks. The results indicate that sliding speed, sliding distance, contact stress and specimen geometry can markedly affect friction, UHMWPE wear, UHMWPE transfer and the type of wear mechanisms that occur. Adhesion appears to be the predominant wear mechanism; but after long sliding distances at slow speeds, heavy ridges of transfer result which can induce fatigue-like wear on the UHMWPE disk wear track. In one instance, abrasive wear to the metallic pin was observed. This was caused by a hard particle embedded in the UHMWPE disk wear track.

  4. 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.

  5. Low molecular weight fucoidan modulates P-selectin and alleviates diabetic nephropathy.

    PubMed

    Xu, Yingjie; Zhang, Quanbin; Luo, Dali; Wang, Jing; Duan, Delin

    2016-10-01

    Diabetic nephropathy (DN) is a serious microvascular complication that can lead to chronic and end-stage renal failure. It is understood that inflammation is associated with the onset and process of DN. Low molecular weight fucoidan (LMWF) isolated from Saccharina japonica has anti-inflammatory properties. Therefore, this study aimed to explore the mechanism of LMWF in DN model induced by streptozotocin. The biochemical indices levels showed LMWF reduced the DN diagnostic indices to protect renal function. The HE stained sections exhibited LMWF protected normal morphological structures and reduced inflammatory cell infiltration in the kidneys of DN rats. Furthermore, the levels of P-selectin and selectin-dependent inflammatory cytokines resulting from LMWF were obviously decreased at both the transcriptional and protein levels. Thus, our results found that LMWF protected the renal function in DN rats and alleviated inflammation through the modulation of P-selectin and inflammatory cytokines. LMWF may have therapeutic potential against DN.

  6. Synthesis of a high molecular weight thyroglobulin dimer by two ovine thyroid cell lines: the OVNIS.

    PubMed

    Hovsépian, S; Aouani, A; Fayet, G

    1986-05-01

    The OVNIS 6H and 5H thyroid cells, 2 permanent cell lines isolated 3 years ago from ovine tissue, synthesize a high molecular weight glycosylated protein, immunologically related to ovine thyroglobulin, which is similar to the prothyroid hormone dimer (17-19) S: thyroglobulin. Using sucrose gradient centrifugation and cell labelling with [14C]Leu or [3H]GlNH2, radioactivity was observed in proteins purified from cell layers and from cell culture media. Addition of thyrotropin to or removal from the media resulted respectively in an increase (+773%) or decrease (-1090%) of the total radioactivity detected in the (17-19)S thyroglobulin fraction. Estimation of thyroglobulin by RIA gave similar though less pronounced effects. These experiments prove (1) that thyroglobulin is still expressed in these OVNIS thyroid cell lines even after 3 years of permanent culture, (2) that TSH modulates the level of this protein through a TSH-receptor functional system. PMID:3709961

  7. Tribological behavior of ultra-high molecular weight polyethylene in a hip joint simulator

    NASA Astrophysics Data System (ADS)

    Mohamad Raffi, N.; Kanagarajan, D.; Srinivasan, V.

    2012-12-01

    In this paper effects of various injection molding parameters on tribological properties of ultra-high molecular weight polyethylene (UHMWPE) were investigated. The tribological properties like coefficient of friction and wear rate were obtained from the experimental results of hip simulator which was designed and fabricated in the laboratory. Bovine serum was used as a lubricant in this study. In addition, the hardness of the specimen was also investigated as well. The injection molding parameters that varied for this study are melt temperature, injection velocity and compaction time. The results show that contact loads and melt temperature were mostly influenced the tribological behavior of UHMWPE. A wear mechanism map was developed to study the dominant wear mechanism that influences the wear behavior of UHMWPE. SEM was employed to study the worn out morphologies of UHMWPE. The dominant wear mechanisms that are dominated through our study are ironing, scratching, ploughing, plastic deformation, and fatigue wear.

  8. Evaluation of molecular weight distribution of unreduced wheat gluten proteins associated with noodle quality.

    PubMed

    Chaudhary, Nisha; Dangi, Priya; Khatkar, B S

    2016-06-01

    Unreduced gluten proteins of Indian wheat varieties viz.C306, DBW16, HI977 and HW2004 were separated using size-exclusion chromatography (SEC). Statistical correlation of area % of eluted peaks with properties of flour, dough and noodles was elucidated. Chromatograms of gluten proteins were classified primarily into five peaks in decreasing molecular size range and relative proportion were expressed in terms of area % of individual peaks which depicts the quantitative variation in protein eluted at different retention times. Cooking time and cooked weight of noodles depicted positive correlation with peak I and negative correlation with peak II which predominantly composed of glutenins and gliadins, respectively. Oil uptake and cooking loss were negatively association with peak I and positively with peak II. Noodle hardness, springiness, cohesiveness and chewiness were positively correlated with peak I and negatively to peak II, though adhesiveness was unaffected by SEC eluted peaks statistically. PMID:27478225

  9. Thermal Behaviour of W+C Ion Implanted Ultra High Molecular Weight Polyethylene (UHMWPE)

    SciTech Connect

    Urkac, E. Sokullu; Oztarhan, A.; Tihminlioglu, F.; Ila, D.; Chhay, B.; Muntele, C.; Budak, S.; Oks, E.; Nikolaev, A.

    2009-03-10

    The aim of this work was to examine thermal behavior of the surface modified Ultra High Molecular Weight Poly Ethylene (UHMWPE ) in order to understand the effect of ion implantation on the properties of this polymer which is widely used especially for biomedical applications. UHMWPE samples were Tungsten and Carbon (W+C) hybrid ion implanted by using Metal Vapour Vacuum Arc (MEVVA) ion implantation technique with a fluence of 10 17 ions/cm2 and extraction voltage of 30 kV. Untreated and surface-treated samples were investigated by Rutherford Back Scattering (RBS) Analysis, Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) Spectrometry, Thermo Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). This study has shown that ion implantation represents a powerful tool on modifying thermal properties of UHMWPE surfaces. This combination of properties can make implanted UHMWPE a preferred material for biomedical applications.

  10. A novel hypotonic sports drink containing a high molecular weight polysaccharide.

    PubMed

    Hao, Limin; Chen, Qiang; Lu, Jike; Li, Zhiyu; Guo, Changjiang; Qian, Ping; Yu, Jianyong; Xing, Xinhui

    2014-05-01

    Carbohydrate consumption during exercise can improve performance and delay the onset of fatigue. The purpose of this study was to develop a novel sports drink powder, Jxdrink, containing the high molecular weight polysaccharide Jxsac. Animal experiments including digestion and exhaustive swimming experiments were conducted to observe the physiological effects of this beverage. Human experiments involved the participation of 10 healthy male athletes completing a 180 km road cycling test. The osmolality of Jxdrink was 170-175 mosmol kg(-1), lower than that of human blood. Jxdrink was found to prolong the exhaustive swimming time in test animals. Moreover, Jxdrink had a relatively high glycemic index that maintained blood glucose levels during human cycling experiments. Thus, Jxdrink was found to effectively delay the onset of fatigue in both human and animal experiments. PMID:24599404

  11. The Anti-Factor Xa Range For Low Molecular Weight Heparin Thromboprophylaxis

    PubMed Central

    Ward, Salena M.

    2015-01-01

    Low molecular weight heparins (LMWHs) are now the mainstay option in the prevention and treatment of venous thromboembolism. In some patients receiving therapeutic doses of LMWH, activity can be measured by quantifying the presence of Anti-factor Xa (AFXa) for dose adjustment. However, currently there are no guidelines for LMWH monitoring in patients on thromboprophylactic, doses, despite certain patient populations may be at risk of suboptimal dosing. This review found that while the AFXa ranges for therapeutic levels of LMWHs are relatively well defined in the literature, prophylactic ranges are much less clear, thus making it difficult to interpret current research data. From the studies published to date, we concluded that a reasonable AFXa target range for LMWH deep venous thromboses prophylaxis might be 0.2-0.5 IU/mL. PMID:26733269

  12. Inhibition of protein-protein interactions with low molecular weight compounds

    PubMed Central

    Matthews, Marilyn M.; Weber, David J.; Shapiro, Paul S.; Coop, Andrew; MacKerell, Alexander D.

    2010-01-01

    An overview of issues associated with the design and development of low molecular weight inhibitors of protein-protein interactions is presented. Areas discussed include information on the nature of protein-protein interfaces, methods to characterize those interfaces and methods by which that information is applied towards ligand identification and design. Specific examples of the strategy for the identification of inhibitors of protein-protein interactions involving the proteins p56lck kinase, ERK2 and the calcium-binding protein S100B are presented. Physical characterization of the inhibitors identified in those studies shows them to have drug-like and lead-like properties, indicating their potential to be developed into therapeutic agents. PMID:21927717

  13. Preparation, tribological properties and biocompatibility of fluorinated graphene/ultrahigh molecular weight polyethylene composite materials

    NASA Astrophysics Data System (ADS)

    Xu, L.; Zheng, Y.; Yan, Z.; Zhang, W.; Shi, J.; Zhou, F.; Zhang, X.; Wang, J.; Zhang, J.; Liu, B.

    2016-05-01

    Fluorinated graphene (FG)/ultra-high molecular weight polyethylene (UHMWPE) composites were successfully prepared by ultrasonic dispersion and liquid thermoforming method. The mechanical and tribological properties of pure UHMWPE and FG/UHMWPE composites were investigated using micro-hardness tester and high-speed reciprocating friction tester. The results showed that: adding FG could not only increase the micro-hardness of the composites, but also decrease the wear volume of the composite significantly. The friction coefficients of the composites were also reduced with the increasing of FG content. In addition, the MC3T3-E1 cells adhered and grew well on the surface of the FG/UHMWPE composites as observed by SEM and fluorescence microscope, indicating the addition of FG did not affect the morphology and activity of the cells. The FG/UHMWPE composites exhibited excellent mechanical properties, tribological properties and biocompatibility, which could be used as the potential artificial joint replacement material.

  14. Absorption and effectiveness of orally administered low molecular weight collagen hydrolysate in rats.

    PubMed

    Watanabe-Kamiyama, Mari; Shimizu, Muneshige; Kamiyama, Shin; Taguchi, Yasuki; Sone, Hideyuki; Morimatsu, Fumiki; Shirakawa, Hitoshi; Furukawa, Yuji; Komai, Michio

    2010-01-27

    Collagen, a major extracellular matrix macromolecule, is widely used for biomedical purposes. We investigated the absorption mechanism of low molecular weight collagen hydrolysate (LMW-CH) and its effects on osteoporosis in rats. When administered to Wistar rats with either [(14)C]proline (Pro group) or glycyl-[(14)C]prolyl-hydroxyproline (CTp group), LMW-CH rapidly increased plasma radioactivity. LMW-CH was absorbed into the blood of Wistar rats in the peptide form. Glycyl-prolyl-hydroxyproline tripeptide remained in the plasma and accumulated in the kidney. In both groups, radioactivity was retained at a high level in the skin until 14 days after administration. Additionally, the administration of LMW-CH to ovariectomized stroke-prone spontaneously hypertensive rats increased the organic substance content and decreased the water content of the left femur. Our findings show that LMW-CH exerts a beneficial effect on osteoporosis by increasing the organic substance content of bone.

  15. High-Flow, High-Molecular-Weight, Addition-Curing Polyimides

    NASA Technical Reports Server (NTRS)

    Chuang, Kathy C.; Vannucci, Raymond D.

    1993-01-01

    In developed series of high-flow PMR-type polyimide resins, 2, 2'-bis(trifluoromethyl)-4, 4'-diaminobiphenyl (BTDB) substituted for 1, 4-pheylenediamine in PMR-II formulation. Polyimides designated either as PMR-12F when nadic ester (NE) end caps used, or as V-CAP-12F when p-aminostyrene end caps used. High-molecular-weight, addition-curing polyimides based on BTBD and HFDE highly processable high-temperature matrix resins used to make composite materials with excellent retention of properties during long-term exposure to air at 650 degrees F or higher temperature. Furthermore, 12F addition-curing polyimides useful for electronic applications; fluorinated rigid-rod polyimides known to exhibit low thermal expansion coefficients as well as low absorption of moisture.

  16. Low molecular weight carbohydrates in pine nuts from Pinus pinea L.

    PubMed

    Ruiz-Aceituno, L; Ramos, L; Martinez-Castro, I; Sanz, M L

    2012-05-16

    Low molecular weight carbohydrates in pine nuts from Pinus pinea L. (n = 7) have been studied by gas chromatography-mass spectrometry as their trimethylsilyl oximes. Besides previously reported components, such as glucose, fructose, sucrose, and raffinose, several soluble carbohydrates have been identified for the first time in this product, including saccharides (galactose, maltose, and planteose) and cyclitols (pinitol, galactinol, galactopinitol A1, fagopyritol B1, and other glycosyl-inositols). Most abundant cyclitols were chiro-inositol, fagopyritol B1, and pinitol, with concentrations ranging from 126.7 to 222.1 mg (100 g)(-1), 94.2 to 177.1 mg (100 g)(-1), and 51.2 to 282.8 mg (100 g)(-1), respectively.

  17. Friction, wear, transfer, and wear surface morphology of ultrahigh-molecular-weight polyethylene

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1985-01-01

    Tribological studies at 25 C in a 50-percent-relative-humidity air atmosphere were conducted using hemispherically tipped 440 C HT (high temperature) stainless steel pins sliding against ultra-high-molecular-weight polyethylene (UHMWPE) disks. The results indicate that sliding speed, sliding distance, contact stress and specimen geometry can markedly affect friction, UHMWPE wear, UHMWPE transfer and the type of wear mechanisms that occur. Adhesion appears to be the predominant wear mechanism; but after long sliding distances at slow speeds, heavy ridges of transfer result which can induce fatigue-like wear on the UHMWPE disk wear track. In one instance, abrasive wear to the metallic pin was observed. This was caused by a hard particle embedded in the UHMWPE disk wear track.

  18. Degradation diagnosis of ultrahigh-molecular weight polyethylene with terahertz-time-domain spectroscopy

    SciTech Connect

    Yamamoto, Kohji; Yamaguchi, Mariko; Tani, Masahiko; Hangyo, Masanori; Teramura, Satoshi; Isu, Toshiro; Tomita, Naohide

    2004-11-29

    We investigated ultrahigh-molecular-weight-polyethylene (UHMWPE) samples prepared by various conditions with terahertz-time-domain spectroscopy (THz-TDS). Degradation of the virgin UHMWPE samples by {gamma} irradiation induced a drastic increase of the absorption ranging continuously over the THz region. The increase of the absorption continuum is interpreted to originate in the oxidation of the amorphous region within the sample. Only slight THz spectral changes induced by the {gamma} irradiation were, however, observed for the UHMWPE samples doped with 0.1 and 0.3 wt % vitamin E. This result agrees with the earlier indication that vitamin E has an antidegradation effect on UHMWPE. The present result shows that the THz-TDS can be used for the quality control of UHMWPE by monitoring the absorption continuum in the THz region.

  19. Dispersion of titania nanoparticles in polydimethylsiloxane fluids using grafted low molecular weight polymers.

    SciTech Connect

    Piech, Martin; Bell, Nelson Simmons; Frischknecht, Amalie Lucile

    2008-06-01

    Nanoparticle interactions and their impact on particle dispersion and rheology are well known to be functions of the interfacial structure between the particle and the fluid phase. The dispersion and flow properties of a titania nanopowder were evaluated in polydimethylsiloxane fluid using ''grafted to'' surface modification of the titania with short molecular weight PDMS polymers. The interaction energy between particles was modeled using analytical expressions as well as dynamic functional theory for polymer surface chains. Particle dynamics as a function of volume fraction were characterized using light scattering, acoustic spectroscopy, and shear and oscillatory measurements. Autophobic dewetting is a novel short range interaction in this system that may be impacting the maximum packing fraction of particles in a suspension.

  20. 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.