Ultrafiltration for the Determination of Cu Complexed with Dissolved Organic Matters of Different Molecular Weight from a Eutrophic River, China.

PubMed

Li, Anding; Zhang, Yan; Zhou, Beihai; Xin, Kailing; Gu, Yingnan; Xu, Weijie; Tian, Jie

2018-05-21

The molecular weight of dissolved organic matter (DOM) is one of the essential factors controlling the properties of metal complexes. A continuous ultrafiltration experiment was designed to study the properties of Cu complexes with different molecular weights in a river before and after eutrophication. The results showed that the concentration of DOM increased from 26.47 to 38.20 mg/L during the eutrophication process, however, DOM was still dominated by the small molecular weight fraction before and after eutrophication. The amount of Cu-DOM complexes increased with the increasing of molecular weight, however, the amounts of DOM-Cu complexes before eutrophication were higher than those after eutrophication. This is because DOM contained more -COOH and -OH before eutrophication and these functional groups are the active sites complexed with Cu.

[Crosslinking sodium hyaluronate gel with different ratio of molecular weight for subcutaneous injection: animal experimental study and clinical trials subcutaneous injection].

PubMed

Ran, Weizhi; Wang, Xiaoli; Hu, Yuefei; Gao, Songying; Yang, Yahong; Sun, Jian; Sun, Shuming; Liu, Zhongmei; Wang, Jiangling

2015-05-01

To investigate the biocompatibility and degradation rate of crosslinking sodium hyaluronate gel with different ratio of molecular weight, so as to choose the effective, safe and totally degraded hyaluronate gel for aesthetic injection. (1) Compound colloid was formed by cross-linking the divinyl sulphone and sodium hyaluronate with different molecular weight (4 x 10(5), 8 x 10(5), 10 x 10(5), 12 x 10(5)). (2) Healthy level KM mice was randomly divided into two groups to receive hyaluronic acid gel or liquid injection. Each group was subdivided into three subgroup to receive hyaluronic acid with different molecular weight. The biocompatibility and degradation rate, of hyaluronate were observed at 7, 90, 180 days after injection. At the same time, different molecular weight of sodium hyaluronate gel is sealed or exposed respectively under the low temperature preservation to observe its natural degradation rate. (3) The most stable colloid was selected as aesthetic injector for volunteers to observe the aesthetic effect. The sodium hyaluronate gel with molecular of 4 x 10(5) was completely degraded 90 days later. The sodium hyaluronate gel with molecular of 8 x 10(5) was completely degraded 180 days later. The sodium hyaluronate gel with molecular of 10 x 10(5) was degraded to 90.0% after 180 days. The sodium hyaluronate liquid can be degraded completely within 7 days. The colloid could be kept for at least 12 months when sealed under low temperature, but was totally degraded when exposed for I d. Sodium hyaluronate gel with molecular 10 x 10(5) was confirmed to be kept for at least 6 months in animal experiment and clinical trials. Under the same condition of material ratio, the higher the molecular weight is, the lower the degradation rate is. But the liquidity of gel is not good for injection when molecular weight is too large. It suggests that Sodium hyaluronate gel with molecular 10 x 10(5) maybe the best choice in cosmetic injections.

Molecular weight dependency of polyrotaxane-cross-linked polymer gel extensibility.

PubMed

Ohmori, Kana; Abu Bin, Imran; Seki, Takahiro; Liu, Chang; Mayumi, Koichi; Ito, Kohzo; Takeoka, Yukikazu

2016-12-11

This work investigates the influence of the molecular weight of polyrotaxane (PR) cross-linkers on the extensibility of polymer gels. The polymer gels, which were prepared using PR cross-linkers of three different molecular weights but the same number of cross-linking points per unit volume of gel, have almost the same Young's modulus. By contrast, the extensibility and rupture strength of the polymer gels are substantially increased with increasing molecular weight of the PR cross-linker.

Characterization and analysis of the molecular weight of lignin for biorefining studies

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

Tolbert, Allison; Akinosho, Hannah; Khunsupat, Ratayakorn

2014-06-04

The molecular weight of lignin is a fundamental property that infl uences the recalcitrance of biomass and the valorization of lignin. The determination of the molecular weight of lignin in native biomass is dependent on the bioresources used and the isolation and purifi cation procedures employed. The three most commonly employed isolation methods are milled wood lignin (MWL), cellulolytic enzyme lignin (CEL), and enzymatic mild acidolysis lignin (EMAL). Common characterization techniques for determining the molecular weight of lignin will be addressed, with an emphasis on gel permeation chromatography (GPC). This review also examines the mechanisms behind several biological, physical, andmore » chemical pre-treatments and their impact on the molecular weight of lignin. The number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (D) all vary in magnitude depending on the biomass source, pre-treatment conditions, and isolation method. Additionally, there is a growing body of literature that supports changes in the molecular weight of lignin in response to genetic modifi cations in the lignin biosynthetic pathways. This review summarizes different procedures for obtaining the molecular weight of lignin that have been used in recent years and highlight future opportunities for applications of lignin.« less

Biological and structural analyses of bovine heparin fractions of intermediate and high molecular weight.

PubMed

Nogueira, Alexsandro V; Drehmer, Daiana L; Iacomini, Marcello; Sassaki, Guilherme L; Cipriani, Thales R

2017-02-10

Low molecular weight heparin, which is generally obtained by chemical and enzymatic depolymerization of unfractionated heparin, has high bioavailability and can be subcutaneously injected. The aim of the present investigation was to fractionate bovine heparin using a physical method (ultrafiltration through a 10kDa cut-off membrane), avoiding structural modifications that can be caused by chemical or enzymatic treatments. Two fractions with different molecular weights were obtained: the first had an intermediate molecular weight (B-IMWH; Mn=9587Da) and the other had a high molecular weight (B-HMWH; 22,396Da). B-IMWH and B-HMWH have anticoagulant activity of 103 and 154IU/mg respectively, which could be inhibited by protamine. Both fractions inhibited α-thrombin and factor Xa in vitro and showed antithrombotic effect in vivo. Moreover, ex vivo aPTT assay demonstrated that B-IMWH is absorbed by subcutaneous route. The results showed that ultrafiltration can be used to obtain two bovine heparin fractions, which differ on their molecular weights, structural components, anticoagulant potency, and administration routes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Origin of change in molecular-weight dependence for polymer surface tension.

PubMed

Thompson, R B; Macdonald, J R; Chen, P

2008-09-01

Self-consistent-field theory is used to reproduce the behavior of polymer surface tension with molecular-weight for both lower and higher molecular-weight polymers. The change in behavior of the surface tension between these two regimes is shown to be due to the almost total exclusion of polymer from the nonpolymer bulk phase. The predicted two regime surface tension behavior with molecular-weight and the exclusion explanation are shown to be valid for a range of different polymer compressibilities.

Perchlorate-induced combustion of organic matter with variable molecular weights: Implications for Mars missions

NASA Astrophysics Data System (ADS)

Sephton, Mark A.; Lewis, James M. T.; Watson, Jonathan S.; Montgomery, Wren; Garnier, Carole

2014-11-01

Instruments on the Viking landers and Curiosity rover analyzed samples of Mars and detected carbon dioxide and organic compounds of uncertain origin. Mineral-assisted reactions are leading to uncertainty, particularly those involving perchlorate minerals which thermally decompose to produce chlorine and oxygen which can then react with organic matter to generate organochlorine compounds and carbon dioxide. Although generally considered a problem for interpretation, the release profiles of generated gases can indicate the type of organic matter present. We have performed a set of experiments with perchlorate and organic matter of variable molecular weights. Results indicate that organic susceptibility to thermal degradation and mineral-assisted reactions is related to molecular weight. Low molecular weight organic matter reacts at lower temperatures than its high molecular weight counterparts. The natural occurrence and association of organic matter with differing molecular weights helps to discriminate between contamination (usually low molecular weight organic matter only) and indigenous carbon (commonly low and high molecular weight organic matter together). Our results can be used to provide insights into data returning from Mars.

Polymeric micelles based on poly(methacrylic acid) block-containing copolymers with different membrane destabilizing properties for cellular drug delivery.

PubMed

Mebarek, Naila; Aubert-Pouëssel, Anne; Gérardin, Corine; Vicente, Rita; Devoisselle, Jean-Marie; Bégu, Sylvie

2013-10-01

Poly(methacrylic acid)-b-poly(ethylene oxide) are double hydrophilic block copolymers, which are able to form micelles by complexation with a counter-polycation, such as poly-l-lysine. A study was carried out on the ability of the copolymers to interact with model membranes as a function of their molecular weights and as a function of pH. Different behaviors were observed: high molecular weight copolymers respect the membrane integrity, whereas low molecular weight copolymers with a well-chosen asymmetry degree can induce a membrane alteration. Hence by choosing the appropriate molecular weight, micelles with distinct membrane interaction behaviors can be obtained leading to different intracellular traffics with or without endosomal escape, making them interesting tools for cell engineering. Especially micelles constituted of low molecular weight copolymers could exhibit the endosomal escape property, which opens vast therapeutic applications. Moreover micelles possess a homogeneous nanometric size and show variable properties of disassembly at acidic pH, of stability in physiological conditions, and finally of cyto-tolerance. Copyright © 2013 Elsevier B.V. All rights reserved.

Effects of different enzymatic hydrolysis methods on the bioactivity of peptidoglycan in Litopenaeus vannamei

NASA Astrophysics Data System (ADS)

Song, Xiaoling; Zhang, Yue; Wei, Song; Huang, Jie

2013-03-01

The effects of different hydrolysis methods on peptidoglycan (PG) were assessed in terms of their impact on the innate immunity and disease resistance of Pacific white shrimp, Litop enaeus vannamei. PG derived from Bifidobacterium thermophilum was prepared in the laboratory and processed with lysozyme and protease under varying conditions to produce several different PG preparations. A standard shrimp feed was mixed with 0.05% PG preparations to produce a number of experimental diets for shrimp. The composition, concentration, and molecular weight ranges of the soluble PG were analyzed. Serum phenoloxidase and acid phosphatase activity in the shrimp were determined on Days 6—31 of the experiment. The protective activity of the PG preparations was evaluated by exposing shrimp to white spot syndrome virus (WSSV). Data on the composition of the PG preparations indicated that preparations hydrolyzed with lysozyme for 72 h had more low-molecular-weight PG than those treated for 24 h, and hydrolysis by protease enhanced efficiency of hydrolysis compared to lysozyme. SDS-PAGE showed changes in the molecular weight of the soluble PG produced by the different hydrolysis methods. Measurements of serum phenoloxidase and acid phosphatase activity levels in the shrimp indicated that the PG preparations processed with enzymes were superior to the preparation which had not undergone hydrolysis in enhancing the activity of the two serum enzymes. In addition, the preparation containing more low-molecular-weight PG enhanced the resistance of the shrimp to WSSV, whereas no increased resistance was observed for preparations containing less low-molecular-weight PG. These findings suggest that the immunity-enhancing activity of PG is related to its molecular weight and that increasing the quantity of low-molecular-weight PG can fortify the effect of immunity enhancement.

Effect of alkali lignins with different molecular weights from alkali pretreated rice straw hydrolyzate on enzymatic hydrolysis.

PubMed

Li, Yun; Qi, Benkun; Luo, Jianquan; Wan, Yinhua

2016-01-01

This study investigated the effect of alkali lignins with different molecular weights on enzymatic hydrolysis of lignocellulose. Different alkali lignins fractions, which were obtained from cascade ultrafiltration, were added into the dilute acid pretreated (DAP) and alkali pretreated (AP) rice straws respectively during enzymatic hydrolysis. The results showed that the addition of alkali lignins enhanced the hydrolysis and the enhancement for hydrolysis increased with increasing molecular weights of alkali lignins, with maximum enhancement being 28.69% for DAP and 20.05% for AP, respectively. The enhancement was partly attributed to the improved cellulase activity, and filter paper activity increased by 18.03% when adding lignin with highest molecular weight. It was found that the enhancement of enzymatic hydrolysis was correlated with the adsorption affinity of cellulase on alkali lignins, and the difference in surface charge and hydrophobicity of alkali lignins were responsible for the difference in affinity between cellulase and lignins. Copyright © 2015 Elsevier Ltd. All rights reserved.

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.

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

In vivo anti-radiation activities of the Ulva pertusa polysaccharides and polysaccharide-iron(III) complex.

PubMed

Shi, Jinming; Cheng, Cuilin; Zhao, Haitian; Jing, Jing; Gong, Ning; Lu, Weihong

2013-09-01

Polysaccharides with different molecular weights were extracted from Ulva pertusa and fractionated by ultrafiltration. Iron(III) complex of the low molecular-weight U. pertusa polysaccharides were synthesized. Atomic absorption spectrum showed that the iron content of iron(III)-polysaccharide complex was 27.4%. The comparison between U. pertusa polysaccharides and their iron(III) complex showed that iron chelating altered the structural characteristics of the polysaccharides. The bioactivity analysis showed that polysaccharide with low molecular weight was more effective than polysaccharide with high molecular weight in protecting mice from radiation induced damages on bone marrow cells and immune system. Results also proved that the anti-radiation and anti-oxidative activity of iron(III) complex of low molecular-weight polysaccharides were not less than that of low molecular-weight polysaccharides. Copyright © 2013 Elsevier B.V. All rights reserved.

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

PubMed

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

2016-10-01

Poly(γ-glutamic acid) mainly produced by Bacillus spp. is an industrially important compound due to several useful features. Among them, molecular weight is an important characteristic affecting on the physical properties such as viscosities and negative charge densities. However, it is difficult to control the molecular size of PGA since it decreases during fermentation. Previous study reported that PGA produced in the media containing different carbon sources such as glucose and glycerol showed differences in molecular weight. Therefore in this study, the effect of carbon source on the PGA molecular weight was examined; with the aim of developing a strategy to maintain the high molecular weight of PGA during fermentation. Our result showed that the weight average molecular weight (Mw) of PGA of Bacillus licheniformis ATCC 9945 cultivated in the media containing PTS-sugars were higher than the medium containing glycerol (non-PTS). The result of metabolome analysis indicated the possibility of CodY (a global regulator protein) activation in the cells cultivated in the media containing PTS-sugars. To mimic this effect, branched-chain amino acids (BCAAs), which are activators of CodY, were added to a medium containing glycerol. As the result, the Mw of PGA in the BCAAs-supplemented media were maintained and high during the early production phase compared to the non BCAAs-supplemented medium. These results indicate that BCAAs can repress the PGA molecular weight reduction during fermentation in B. licheniformis ATCC 9945. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Effect of mahlep on molecular weight distribution of cookie flour gluten proteins

USDA-ARS?s Scientific Manuscript database

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 ...

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

Morphological, spectral and chromatography analysis and forensic comparison of PET fibers.

PubMed

Farah, Shady; Tsach, Tsadok; Bentolila, Alfonso; Domb, Abraham J

2014-06-01

Poly(ethylene terephthalate) (PET) fiber analysis and comparison by spectral and polymer molecular weight determination was investigated. Plain fibers of PET, a common textile fiber and plastic material was chosen for this study. The fibers were analyzed for morphological (SEM and AFM), spectral (IR and NMR), thermal (DSC) and molecular weight (MS and GPC) differences. Molecular analysis of PET fibers by Gel Permeation Chromatography (GPC) allowed the comparison of fibers that could not be otherwise distinguished with high confidence. Plain PET fibers were dissolved in hexafluoroisopropanol (HFIP) and analyzed by GPC using hexafluoroisopropanol:chloroform 2:98 v/v as eluent. 14 PET fiber samples, collected from various commercial producers, were analyzed for polymer molecular weight by GPC. Distinct differences in the molecular weight of the different fiber samples were found which may have potential use in forensic fiber comparison. PET fibers with average molecular weights between about 20,000 and 70,000 g mol(-1) were determined using fiber concentrations in HFIP as low as 1 μg mL(-1). This GPC analytical method can be applied for exclusively distinguish between PET fibers using 1 μg of fiber. This method can be extended to forensic comparison of other synthetic fibers such as polyamides and acrylics. Copyright © 2014 Elsevier B.V. All rights reserved.

Differentiation of parenteral anticoagulants in the prevention and treatment of venous thromboembolism.

PubMed

Fareed, Jawed; Adiguzel, Cafer; Thethi, Indermohan

2011-03-28

The prevention of venous thromboembolism has been identified as a leading priority in hospital safety. Recommended parenteral anticoagulant agents with different indications for the prevention and treatment of venous thromboembolism include unfractionated heparin, low-molecular-weight heparins and fondaparinux. Prescribing decisions in venous thromboembolism management may seem complex due to the large range of clinical indications and patient types, and the range of anticoagulants available. MEDLINE and EMBASE databases were searched to identify relevant original articles. Low-molecular-weight heparins have nearly replaced unfractionated heparin as the gold standard antithrombotic agent. Low-molecular-weight heparins currently available in the US are enoxaparin, dalteparin, and tinzaparin. Each low-molecular-weight heparin is a distinct pharmacological entity with different licensed indications and available clinical evidence. Enoxaparin is the only low-molecular-weight heparin that is licensed for both venous thromboembolism prophylaxis and treatment. Enoxaparin also has the largest body of clinical evidence supporting its use across the spectrum of venous thromboembolism management and has been used as the reference standard comparator anticoagulant in trials of new anticoagulants. As well as novel oral anticoagulant agents, biosimilar and/or generic low-molecular-weight heparins are now commercially available. Despite similar anticoagulant properties, studies report differences between the branded and biosimilar and/or generic agents and further clinical studies are required to support the use of biosimilar low-molecular-weight heparins. The newer parenteral anticoagulant, fondaparinux, is now also licensed for venous thromboembolism prophylaxis in surgical patients and the treatment of acute deep-vein thrombosis; clinical experience with this anticoagulant is expanding. Parenteral anticoagulants should be prescribed in accordance with recommended dose regimens for each clinical indication, based on the available clinical evidence for each agent to assure optimal safety and efficacy.

Physical characterization of polyethylene glycols by thermal analytical technique and the effect of humidity and molecular weight.

PubMed

Majumdar, R; Alexander, K S; Riga, A T

2010-05-01

Polyethylene glycols (PEGs) are well known as excipients in tablet dosage formulations. PEGs are generally known to be inert and have very few interactions with other components in the solid dosage forms. However, the physical nature of PEGs and how they affect the disintegration of tablets is not very well understood for the different molecular weights of PEGs. The knowledge of the effect of molecular weight of PEGs on their physical properties and the effect of humidity on the physical properties of PEGs are important parameters for the choice of a PEG to be acceptable as an excipient in pharmaceutical formulations. This study was done to determine the precision of the DSC physical properties for a wide range of PEGs with varying molecular weights from 194 to 23000 daltons. Nine different molecular weights of PEGs were examined in a DSC controlled Heat-Cool-Heat-Cool-Heat (HCHCH) cycle and the observed reproducible values of melting temperature, heat of fusion, crystallization temperature and the heat of crystallization were compared with values obtained from the literature and the observed percent crystallinity was again cross-checked by X-ray Diffraction (XRD) studies. The comparison values indicated acceptable precision. This study was also done to check the effect of humidity on the DSC physical properties for the entire range of PEGs. The results indicated that humidity probably has a higher effect on the physical properties of the low molecular weight PEGs as compared to the high molecular weight PEGs.

Establishment of replacement batches for heparin low-molecular-mass for calibration CRS, and the International Standard Low Molecular Weight Heparin for Calibration.

PubMed

Mulloy, B; Heath, A; Behr-Gross, M-E

2007-12-01

An international collaborative study involving fourteen laboratories has taken place, organised by the European Directorate for the Quality of Medicines & HealthCare (EDQM) with National Institute for Biological Standards & Control (NIBSC) (in its capacity as a World Health Organisation (WHO) Laboratory for Biological Standardisation) to provide supporting data for the establishment of replacement batches of Heparin Low-Molecular-Mass (LMM) for Calibration Chemical Reference Substance (CRS), and of the International Reference Reagent (IRR) Low Molecular Weight Heparin for Molecular Weight Calibration. A batch of low-molecular-mass heparin was donated to the organisers and candidate preparations of freeze-dried heparin were produced at NIBSC and EDQM. The establishment study was organised in two phases: a prequalification (phase 1, performed in 3 laboratories in 2005) followed by an international collaborative study (phase 2). In phase 2, started in March 2006, molecular mass parameters were determined for seven different LMM heparin samples using the current CRS batch and two batches of candidate replacement material with a defined number average relative molecular mass (Mn) of 3,700, determined in phase 1. The values calculated using the candidates as standard were systematically different from values calculated using the current batch with its assigned number-average molecular mass (Mna) of 3,700. Using raw data supplied by participants, molecular mass parameters were recalculated using the candidates as standard with values for Mna of 3,800 and 3,900. Values for these parameters agreed more closely with those calculated using the current batch supporting the fact that the candidates, though similar to batch 1 in view of the production processes used, differ slightly in terms of molecular mass distribution. Therefore establishment of the candidates was recommended with an assigned Mna value of 3,800 that is both consistent with phase 1 results and guarantees continuity with the current CRS batch. In phase 2, participants also determined molecular weight parameters for the seven different LMM heparin samples using both the 1st IRR (90/686) and its Broad Standard Table and the candidate World Health Organization (WHO) 2nd International Standard (05/112) (2nd IS) using a Broad Standard Table established in phase 1. Mean molecular weights calculated using 2nd IS were slightly higher than with 1st IRR, and participants in the study indicated that this systematic difference precluded establishment of 2nd IS with the table supplied. A replacement Broad Standard Table has been devised on the basis of the central recalculations of raw data supplied by participants; this table gives improved agreement between values derived using the 1st IRR and the candidate 2nd IS. On the basis of this study a recommendation was made for the establishment of 2nd IS and its proposed Broad Standard Table as a replacement for the 1st International Reference Reagent Low Molecular Weight Heparin for Molecular Weight Calibration. Unlike the 1st IRR however, the candidate material 2nd IS is not suitable for use with the method of Nielsen. The candidate materials were established as heparin low-molecular-mass for calibration batches 2 and 3 by the Ph. Eur. Commission in March 2007 and as 2nd IS low-molecular-weight heparin for molecular weight calibration (05/112) by the Expert Committee on Biological Standardization in November 2007.

Molecular weight kinetics and chain scission models for dextran polymers during ultrasonic degradation.

PubMed

Pu, Yuanyuan; Zou, Qingsong; Hou, Dianzhi; Zhang, Yiping; Chen, Shan

2017-01-20

Ultrasonic degradation of six dextran samples with different initial molecular weights (IMW) has been performed to investigate the degradation behavior and chain scission mechanism of dextrans. The weight-average molecular weight (Mw) and polydispersity index (D value) were monitored by High Performance Gel Permeation Chromatography (HPGPC). Results showed that Mw and D value decreased with increasing ultrasonic time, resulting in a more homologous dextran solution with lower molecular weight. A significant degradation occurred in dextrans with higher IMW, particularly at the initial stage of the ultrasonic treatment. The Malhotra model was found to well describe the molecular weight kinetics for all dextran samples. Experimental data was fitted into two chain scission models to study dextran chain scission mechanism and the model performance was compared. Results indicated that the midpoint scission model agreed well with experimental results, with a linear regression factor of R 2 >0.99. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of the molecular weight of a neutral polysaccharide on soy protein gelation.

PubMed

Monteiro, Sónia R; Lopes-da-Silva, José A

2017-12-01

The effects of galactomannans with different molecular weights on the heat-induced gelation characteristics of soybean protein were investigated using dynamic small-strain rheometry, under conditions where the proteins carry a net negative charge (pH7). Microstructure of the resulting gels was investigated by confocal laser scanning microscopy. Phase-separated systems were obtained with different morphologies and degree of phase separation, depending on both biopolymer concentrations and polysaccharide molecular weight. In general, a gelling enhancing effect on soy proteins was verified, despite extensive phase-separation processes observed at the higher polysaccharide molecular weight. This effect was demonstrated by an increase of the gelation rate, a decrease in the temperature at the onset of gelation, and an increase of gel stiffness and elastic character, with the length of polysaccharide chains. Overall, the results obtained established that the judicious selection of the galactomannan molecular weight may be used to modify the structure and gelation properties of soy proteins, originating a diversity of rheological characteristics and microstructures that will impact on the design of novel food formulations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of grain development on formation of resistant starch in rice.

PubMed

Shu, Xiaoli; Sun, Jian; Wu, Dianxing

2014-12-01

Three rice mutants with different contents of resistant starch (RS) were selected to investigate the effects of grain filling process on the formation of resistant starch. During grain development, the content of RS was increased with grain maturation and showed negative correlations with the grain weight and the starch molecular weight (Mn, Mw) and a positive correlation with the distribution of molecular mass (polydispersity, Pd). The morphologies of starch granules in high-RS rice were almost uniform in single starch granules and exhibited different proliferation modes from common rice. The lower activities of ADP-glucose pyrophosphorylase and starch branching enzyme and the higher activity of starch synthase and starch de-branching enzyme observed in high-RS rice might be responsible for the formation of small irregular starch granules with large spaces between them. In addition, the lower molecular weight and the broad distribution of molecular weights lead to differences in the physiochemical properties of starch. Copyright © 2014 Elsevier Ltd. All rights reserved.

Temperature and molecular-weight dependences of acoustic behaviors of polystyrene studied using Brillouin spectroscopy

NASA Astrophysics Data System (ADS)

Oh, Soo Han; Lee, Byoung Wan; Ko, Jae-Hyeon; Lee, Hyeonju; Park, Jaehoon; Ko, Young Ho; Kim, Kwang Joo

2017-04-01

The acoustic properties of three polystyrene polymers with different molecular weights were investigated as a function of temperature by using Brillouin light scattering. The longitudinal sound velocity showed a change in the slope, which depended on the molecular weight, at the glass transition temperature. The absorption coefficient exhibited a maximum above the glass transition temperature, and the maximum temperature became higher as the molecular weight was increased. Comparison with previous acoustic studies on polystyrene indicate that a substantial frequency dispersion caused by strong coupling between the longitudinal acoustic waves and the segmental motions exists in the high-temperature range.

Hypoglycemic Effect of Chinese Yam (Dioscorea opposita rhizoma) Polysaccharide in Different Structure and Molecular Weight.

PubMed

Li, Qian; Li, Wenzhi; Gao, Qunyu; Zou, Yuxiao

2017-10-01

Three new Chinese yam polysaccharides (namely HSY, huaishanyao in Chinese) were isolated using the methods of boiled water extraction and stepwise ethanolic precipitation, combined with the tangential flow ultrafiltration membrane system. Their molecular weights were determined by high performance gel permeation chromatography. Three type yam polysaccharides in different molecular weight were isolated: HSY-I (>50 kDa), HSY-II (10 to 50 kDa), HSY-III (<10 kDa). The monosaccharide and glycosidic bond links composition were analyzed with GC and Smith degradation. The structure characteristics were further discussed combined with infrared spectrophotometry. Dexamethasone-induced insulin resistance glucose/lipid metabolism diabetic mice model was established to evaluate the hypoglycemic effect of different concentration of HSY and different molecular weights polysaccharide HSY-I, HSY-II, and HSY-III. The results indicated that the HSY polysaccharide mixture, HSY-I and HSY-II had hypoglycemic effect. Three polysaccharides from Chinese yam tuber were isolated in this study. Their structures were characterized and hypoglycemic effects were evaluated. The result clearly identified the benefits of this plant as a healthy functional food. © 2017 Institute of Food Technologists®.

Phase Behavior of Binary Blends of High Molecular Weight Diblock Copolymers with a Low Molecular Weight Triblock

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

Mickiewicz, Rafal A.; Ntoukas, Eleftherios; Avgeropoulos, Apostolos

2009-08-26

Binary blends of four different high molecular weight poly(styrene-b-isoprene) (SI) diblock copolymers with a lower molecular weight poly(styrene-b-isoprene-b-styrene) (SIS) triblock copolymer were prepared, and their morphology was characterized by transmission electron microscopy and ultra-small-angle X-ray scattering. All the neat block copolymers have nearly symmetric composition and exhibit the lamellar morphology. The SI diblock copolymers had number-average molecular weights, Mn, in the range 4.4 x 10{sup 5}--1.3 x 10{sup 6} g/mol and volume fractions of poly(styrene), {Phi}{sub PS}, in the range 0.43--0.49, and the SIS triblock had a molecular weight of Mn 6.2 x 10{sup 4} g/mol with {Phi}{sub PS} =more » 0.41. The high molecular weight diblock copolymers are very strongly segregating, with interaction parameter values, {chi}N, in the range 470--1410. A morphological phase diagram in the parameter space of molecular weight ratio (R = M{sub n}{sup diblock}/1/2M{sub n}{sup triblock}) and blend composition was constructed, with R values in the range between 14 and 43, which are higher than previously reported. The phase diagram revealed a large miscibility gap for the blends, with macrophase separation into two distinct types of microphase-separated domains for weight fractions of SI, w{sub SI} < 0.9, implying virtually no solubility of the much higher molecular weight diblocks in the lower molecular weight triblock. For certain blend compositions, above R 30, morphological transitions from the lamellar to cylindrical and bicontinuous structures were also observed.« less

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

USGS Publications Warehouse

Rostad, Colleen E.; Leenheer, Jerry A.

2004-01-01

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

Increase in gap junctional intercellular communication by high molecular weight hyaluronic acid associated with fibroblast growth factor 2 and keratinocyte growth factor production in normal human dermal fibroblasts.

PubMed

Park, Jeong Ung; Tsuchiya, Toshie

2002-07-01

The effects of different molecular weights of hyaluronic acid (HA), a major component of extracellular matrix, on gap junctional intercellular communication (GJIC) in normal human dermal fibroblasts (NHDF cells) were investigated. NHDF cells were cultured for 4 days with different molecular weights of HA and then the extent of GJIC was assessed by the scrape-loading dye transfer method, using Lucifer yellow. The area of dye transfer was greater in the dishes coated with HA than in those to which HA was added. Thus, NHDF cells cultured on surfaces coated with high molecular weight (HMW) HA (MW, 800 kDa) showed greatly enhanced GJIC. Furthermore, another aim of this study was to evaluate the effects of different molecular weights of HA on the production of FGF-2 and KGF, because both are important cytokines produced by NHDF cells. When FGF-2 and KGF cultured levels of cell extracts and media were determined by ELISA, both levels were significantly enhanced when cells were grown on plates coated with HMW HA. This finding indicated that the function of gap junction channels in NHDF cells grown on plates coated with HMW HA may promote the biosynthesis of growth factors such as FGF-2 and KGF.

EPDM polymers with intermolecular asymmetrical molecular weight, crystallinity and diene distribution

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

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 thesemore » 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.« less

Determination of the molecular weight of low-molecular-weight heparins by using high-pressure size exclusion chromatography on line with a triple detector array and conventional methods.

PubMed

Bisio, Antonella; Mantegazza, Alessandra; Vecchietti, Davide; Bensi, Donata; Coppa, Alessia; Torri, Giangiacomo; Bertini, Sabrina

2015-03-19

The evaluation of weight average molecular weight (Mw) and molecular weight distribution represents one of the most controversial aspects concerning the characterization of low molecular weight heparins (LMWHs). As the most commonly used method for the measurement of such parameters is high performance size exclusion chromatography (HP-SEC), the soundness of results mainly depends on the appropriate calibration of the chromatographic columns used. With the aim of meeting the requirement of proper Mw standards for LMWHs, in the present work the determination of molecular weight parameters (Mw and Mn) by HP-SEC combined with a triple detector array (TDA) was performed. The HP-SEC/TDA technique permits the evaluation of polymeric samples by exploiting the combined and simultaneous action of three on-line detectors: light scattering detectors (LALLS/RALLS); refractometer and viscometer. Three commercial LMWH samples, enoxaparin, tinzaparin and dalteparin, a γ-ray depolymerized heparin (γ-Hep) and its chromatographic fractions, and a synthetic pentasaccharide were analysed by HP-SEC/TDA. The same samples were analysed also with a conventional HP-SEC method employing refractive index (RI) and UV detectors and two different chromatographic column set, silica gel and polymeric gel columns. In both chromatographic systems, two different calibration curves were built up by using (i) γ-Hep chromatographic fractions and the corresponding Mw parameters obtained via HP-SEC/TDA; (ii) the whole γ-Hep preparation with broad Mw dispersion and the corresponding cumulative distribution function calculated via HP-SEC/TDA. In addition, also a chromatographic column calibration according to European Pharmacopoeia indication was built up. By comparing all the obtained results, some important differences among Mw and size distribution values of the three LMWHs were found with the five different calibration methods and with HP-SEC/TDA method. In particular, the detection of the lower molecular weight components turned out to be the most critical aspect. Whereas HP-SEC/TDA may underestimate species under 2 KDa when present in low concentration, other methods appeared to emphasize their content.

High Molecular Weight Polymers in the New Chemicals Program

EPA Pesticide Factsheets

There are three categories or types of High Molecular Weight (HMW, 10,000 daltons) polymers typically reviewed by the New Chemicals Program: Soluble, insoluble, and water absorbing. Each of the three types are treated differently.

Effect of molecular weight of chitosan on the shelf life and other quality parameters of three different cultivars of Actinidia kolomikta (kiwifruit).

PubMed

Drevinskas, Tomas; Naujokaitytė, Gintarė; Maruška, Audrius; Kaya, Murat; Sargin, Idris; Daubaras, Remigijus; Česonienė, Laima

2017-10-01

The kiwi fruit, Actinidia kolomikta, has valuable properties such as high antioxidant activity, high vitamin C, polyphenols, chlorophylls and organic acids content, but the species are hardly commercialized due to their short shelf life (less than two days). In this study three different cultivars of A. kolomikta (Anykšta, Sentiabrskaya and VIR2) were coated with low, medium and high molecular weight chitosan bio-polymer with the aim to extend the shelf life. The changes in fruit firmness, mass, phenolic compound content, vitamin C content and subjective criteria (withering level, decoloration level and aesthetic appearance) were monitored. It was observed that high molecular weight chitosan had higher positive effect on the shelf life of Sentiabrskaya and Anykšta cultivars than VIR2. Low molecular weight chitosan was found effective on VIR2. Copyright © 2017 Elsevier Ltd. All rights reserved.

Low-molecular-weight heparins: pharmacologic profile and product differentiation.

PubMed

Fareed, J; Jeske, W; Hoppensteadt, D; Clarizio, R; Walenga, J M

1998-09-10

The interchangeability of low-molecular-weight heparins (LMWHs) has been the subject of discussion since these products were first introduced for the prophylaxis of deep vein thrombosis. Experimental evidence now exists to show that LMWHs differ from each other in a number of characteristics. Products have been differentiated on the basis of molecular weight and biologic properties, but only limited information derived from the clinical setting is available. Potency has been described on the basis of anti-Factor Xa activity, but at equivalent anti-Xa activities, the anti-Factor IIa activity of different products shows marked variations. At the relatively small doses used for the management of postsurgical deep vein thrombosis, the effect of these interproduct differences may be relatively minor, but as LMWHs are developed for therapeutic use at much higher doses, such differences may become clinically important. Variations in safety and efficacy reported in clinical trials of LMWHs may reflect the known differences in their molecular composition and pharmacologic properties.

Determination of the linear coefficient of thermal expansion in polymer films at the nanoscale: influence of the composition of EVA copolymers and the molecular weight of PMMA.

PubMed

González-Benito, J; Castillo, E; Cruz-Caldito, J F

2015-07-28

Nanothermal-expansion of poly(ethylene-co-vinylacetate), EVA, and poly(methyl methacrylate), PMMA, in the form of films was measured to finally obtain linear coefficients of thermal expansion, CTEs. The simple deflection of a cantilever in an atomic force microscope, AFM, was used to monitor thermal expansions at the nanoscale. The influences of: (a) the structure of EVA in terms of its composition (vinylacetate content) and (b) the size of PMMA chains in terms of the molecular weight were studied. To carry out this, several polymer samples were used, EVA copolymers with different weight percents of the vinylacetate comonomer (12, 18, 25 and 40%) and PMMA polymers with different weight average molecular weights (33.9, 64.8, 75.600 and 360.0 kg mol(-1)). The dependencies of the vinyl acetate weight fraction of EVA and the molecular weight of PMMA on their corresponding CTEs were analyzed to finally explain them using new, intuitive and very simple models based on the rule of mixtures. In the case of EVA copolymers a simple equation considering the weighted contributions of each comonomer was enough to estimate the final CTE above the glass transition temperature. On the other hand, when the molecular weight dependence is considered the free volume concept was used as novelty. The expansion of PMMA, at least at the nanoscale, was well and easily described by the sum of the weighted contributions of the occupied and free volumes, respectively.

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

J Cai; B Hsiao; R Gross

Poly({omega}-pentadecalactone) (PPDL), a model polymer in the poly({omega}-hydroxyl fatty acids) family, is a new biopolymer with monomer synthesized by yeast-catalyzed {omega}-hydroxylation of fatty acids. In this study, deformation-induced structural changes in two PPDL samples with different molecular weights were studied by in situ wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. The high molecular weight PPDL (PPDL-high) sample exhibited notable strain hardening, while the low molecular weight PPDL (PPDL-low) sample did not. The behavior can be explained by the entanglement density concept. The evolution of crystallinity (from WAXD) as a function of strain could be divided into fourmore » distinct regions, but their respective mechanisms differ slightly in each sample. During stretching, a mesomorphic phase formed in both samples, bridging between the amorphous and strain-induced crystal phases. The SAXS data verified the effect of molecular weight (or the entanglement density) on the deformation-induced structure of PPDL. The parameters of chain orientation factor (f) calculated from the orthorhombic crystal cell as well as the nonorthorhombic crystal cell proposed by Wilchinsky were used to follow the orientation process during stretching of PPDLs. It was found that the different molecular entanglement network (i.e., PPDL-low versus PPDL-high) led to different crystal orientation behavior, especially in the low strain range.« less

Molecular Factors Governing the Liquid and Glassy States Recrystallization of Celecoxib in Binary Mixtures with Excipients of Different Molecular Weights.

PubMed

Grzybowska, K; Chmiel, K; Knapik-Kowalczuk, J; Grzybowski, A; Jurkiewicz, K; Paluch, M

2017-04-03

Transformation of poorly water-soluble crystalline pharmaceuticals to the amorphous form is one of the most promising strategies to improve their oral bioavailability. Unfortunately, the amorphous drugs are usually thermodynamically unstable and may quickly return to their crystalline form. A very promising way to enhance the physical stability of amorphous drugs is to prepare amorphous compositions of APIs with certain excipients which can be characterized by significantly different molecular weights, such as polymers, acetate saccharides, and other APIs. By using different experimental techniques (broadband dielectric spectroscopy, differential scanning calorimetry, X-ray diffraction) we compare the effect of adding the large molecular weight polymer-polyvinylpyrrolidone (PVP K30)-and the small molecular weight excipient-octaacetylmaltose (acMAL)-on molecular dynamics as well as the tendency to recrystallization of the amorphous celecoxib (CEL) in the amorphous solid dispersions: CEL-PVP and CEL-acMAL. The physical stability investigations of the binary systems were performed in both the supercooled liquid and glassy states. We found that acMAL is a better inhibitor of recrystallization of amorphous CEL than PVP K30 deep in the glassy state (T < T g ). In contrast, PVP K30 is a better crystallization inhibitor of CEL than acMAL in the supercooled liquid state (at T > T g ). We discuss molecular factors governing the recrystallization of amorphous CEL in examined solid dispersions.

Manipulation of Molecular Weight Distribution Shape as a New Strategy to Control Processing Parameters.

PubMed

Nadgorny, Milena; Gentekos, Dillon T; Xiao, Zeyun; Singleton, S Parker; Fors, Brett P; Connal, Luke A

2017-10-01

Molecular weight and dispersity (Ð) influence physical and rheological properties of polymers, which are of significant importance in polymer processing technologies. However, these parameters provide only partial information about the precise composition of polymers, which is reflected by the shape and symmetry of molecular weight distribution (MWD). In this work, the effect of MWD symmetry on thermal and rheological properties of polymers with identical molecular weights and Ð is demonstrated. Remarkably, when the MWD is skewed to higher molecular weight, a higher glass transition temperature (T g ), increased stiffness, increased thermal stability, and higher apparent viscosities are observed. These observed differences are attributed to the chain length composition of the polymers, easily controlled by the synthetic strategy. This work demonstrates a versatile approach to engineer the properties of polymers using controlled synthesis to skew the shape of MWD. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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…

The effects of postexercise consumption of high-molecular-weight versus low-molecular-weight carbohydrate solutions on subsequent high-intensity interval-running capacity.

PubMed

McGlory, Chris; Morton, James P

2010-10-01

The aim of this study was to determine the effects of postexercise ingestion of different-molecular-weight glucose polymer solutions on subsequent high-intensity interval-running capacity. In a repeated-measures design, 6 men ran for 60 min in the morning at 70% VO2max. Immediately post- and at 1 and 2 hr postexercise, participants consumed a 15% low-molecular-weight (LMW) or high-molecular-weight (HMW) carbohydrate solution, at a rate of 1.2 g of carbohydrate/kg body mass, or an equivalent volume of flavored water (WAT). After recovery, participants performed repeated 1-min intervals at 90% VO2max interspersed with 1 min active recovery (walking) until volitional exhaustion. Throughout the 3-hr recovery period, plasma glucose concentrations were higher (p=.002) during the HMW and LMW conditions than with WAT (M 7.0±0.8, 7.5±1.0, and 5.6±0.2 mmol/L, respectively), although there was no difference (p=.723) between HMW and LMW conditions. Exercise capacity was 13 (43±10 min; 95% CI for differences: 8-18; p=.001) and 11 min (41±9 min; 95% CI for differences; 2-18: p=.016) longer with HMW and LMW solutions, respectively, than with WAT (30±9 min). There was no substantial difference (2 min; 95% CI for differences: -5 to 10; p=.709) in exercise capacity between LMW and HMW solutions. Although this magnitude of difference is most likely trivial in nature, the uncertainty allows for a possible small substantial enhancement of physiological significance, and further research is required to clarify the true nature of the effect.

Effects of molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase.

PubMed

Kim, Jihoon; Chang, Ji-Youn; Kim, Yoon-Young; Kim, Moon-Jong; Kho, Hong-Seop

2018-05-01

To investigate the effects of the molecular weight of hyaluronic acid on its viscosity and enzymatic activities of lysozyme and peroxidase in solution and on the hydroxyapatite surface. Hyaluronic acids of four different molecular weights (10 kDa, 100 kDa, 1 MDa, and 2 MDa), hen egg-white lysozyme, bovine lactoperoxidase, and human whole saliva were used. Viscosity values of hyaluronic acids were measured using a cone-and-plate viscometer at six different concentrations (0.1-5.0 mg/mL). Enzymatic activities of lysozyme and peroxidase were examined by hydrolysis of fluorescein-labeled Micrococcus lysodeikticus and oxidation of fluorogenic 2',7'-dichlorofluorescein to fluorescing 2',7'-dichlorofluorescein, respectively. In solution assays, only 2 MDa-hyaluronic acid significantly inhibited lysozyme activities in saliva. In surface assays, hyaluronic acids inhibited lysozyme and peroxidase activities; the inhibitory activities were more apparent with high-molecular-weight ones in saliva than in purified enzymes. The 100 kDa-hyaluronic acid at 5.0 mg/mL, 1 MDa-one at 0.5 mg/mL, and 2 MDa-one at 0.2 mg/mL showed viscosity values similar to those of human whole saliva at a shear rate range required for normal oral functions. The differences among the influences of the three conditions on the enzymatic activities were not statistically significant. High-molecular-weight hyaluronic acids at low concentration and low-molecular-weight ones at high concentration showed viscosity values similar to those of human whole saliva. Inhibitory effects of hyaluronic acids on lysozyme and peroxidase activities were more significant with high-molecular-weight ones on the surface and in saliva compared with in solution and on purified enzymes. Copyright © 2018 Elsevier Ltd. All rights reserved.

Generation of a large volume of clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles for cell culture studies

PubMed Central

Ingham, Eileen; Fisher, John; Tipper, Joanne L

2014-01-01

It has recently been shown that the wear of ultra-high-molecular-weight polyethylene in hip and knee prostheses leads to the generation of nanometre-sized particles, in addition to micron-sized particles. The biological activity of nanometre-sized ultra-high-molecular-weight polyethylene wear particles has not, however, previously been studied due to difficulties in generating sufficient volumes of nanometre-sized ultra-high-molecular-weight polyethylene wear particles suitable for cell culture studies. In this study, wear simulation methods were investigated to generate a large volume of endotoxin-free clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles. Both single-station and six-station multidirectional pin-on-plate wear simulators were used to generate ultra-high-molecular-weight polyethylene wear particles under sterile and non-sterile conditions. Microbial contamination and endotoxin levels in the lubricants were determined. The results indicated that microbial contamination was absent and endotoxin levels were low and within acceptable limits for the pharmaceutical industry, when a six-station pin-on-plate wear simulator was used to generate ultra-high-molecular-weight polyethylene wear particles in a non-sterile environment. Different pore-sized polycarbonate filters were investigated to isolate nanometre-sized ultra-high-molecular-weight polyethylene wear particles from the wear test lubricants. The use of the filter sequence of 10, 1, 0.1, 0.1 and 0.015 µm pore sizes allowed successful isolation of ultra-high-molecular-weight polyethylene wear particles with a size range of < 100 nm, which was suitable for cell culture studies. PMID:24658586

Generation of a large volume of clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles for cell culture studies.

PubMed

Liu, Aiqin; Ingham, Eileen; Fisher, John; Tipper, Joanne L

2014-04-01

It has recently been shown that the wear of ultra-high-molecular-weight polyethylene in hip and knee prostheses leads to the generation of nanometre-sized particles, in addition to micron-sized particles. The biological activity of nanometre-sized ultra-high-molecular-weight polyethylene wear particles has not, however, previously been studied due to difficulties in generating sufficient volumes of nanometre-sized ultra-high-molecular-weight polyethylene wear particles suitable for cell culture studies. In this study, wear simulation methods were investigated to generate a large volume of endotoxin-free clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles. Both single-station and six-station multidirectional pin-on-plate wear simulators were used to generate ultra-high-molecular-weight polyethylene wear particles under sterile and non-sterile conditions. Microbial contamination and endotoxin levels in the lubricants were determined. The results indicated that microbial contamination was absent and endotoxin levels were low and within acceptable limits for the pharmaceutical industry, when a six-station pin-on-plate wear simulator was used to generate ultra-high-molecular-weight polyethylene wear particles in a non-sterile environment. Different pore-sized polycarbonate filters were investigated to isolate nanometre-sized ultra-high-molecular-weight polyethylene wear particles from the wear test lubricants. The use of the filter sequence of 10, 1, 0.1, 0.1 and 0.015 µm pore sizes allowed successful isolation of ultra-high-molecular-weight polyethylene wear particles with a size range of < 100 nm, which was suitable for cell culture studies.

Adsorption of Poly(methyl methacrylate) on Concave Al2O3 Surfaces in Nanoporous Membranes

PubMed Central

Nunnery, Grady; Hershkovits, Eli; Tannenbaum, Allen; Tannenbaum, Rina

2009-01-01

The objective of this study was to determine the influence of polymer molecular weight and surface curvature on the adsorption of polymers onto concave surfaces. Poly(methyl methacrylate) (PMMA) of various molecular weights was adsorbed onto porous aluminum oxide membranes having various pore sizes, ranging from 32 to 220 nm. The surface coverage, expressed as repeat units per unit surface area, was observed to vary linearly with molecular weight for molecular weights below ~120 000 g/mol. The coverage was independent of molecular weight above this critical molar mass, as was previously reported for the adsorption of PMMA on convex surfaces. Furthermore, the coverage varied linearly with pore size. A theoretical model was developed to describe curvature-dependent adsorption by considering the density gradient that exists between the surface and the edge of the adsorption layer. According to this model, the density gradient of the adsorbed polymer segments scales inversely with particle size, while the total coverage scales linearly with particle size, in good agreement with experiment. These results show that the details of the adsorption of polymers onto concave surfaces with cylindrical geometries can be used to calculate molecular weight (below a critical molecular weight) if pore size is known. Conversely, pore size can also be determined with similar adsorption experiments. Most significantly, for polymers above a critical molecular weight, the precise molecular weight need not be known in order to determine pore size. Moreover, the adsorption developed and validated in this work can be used to predict coverage also onto surfaces with different geometries. PMID:19415910

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.

A single center retrospective cohort study comparing low-molecular-weight heparins to direct oral anticoagulants for the treatment of venous thromboembolism in patients with cancer - A real world experience.

PubMed

Phelps, Megan K; Wiczer, Tracy E; Erdeljac, H Paige; Van Deusen, Kelsey R; Porter, Kyle; Philips, Gary; Wang, Tzu-Fei

2018-01-01

Introduction Low-molecular-weight heparins are the standard treatment for cancer-associated thrombosis. Recently, direct oral anticoagulants are a new option for thrombosis treatment; however, data supporting the use of direct oral anticoagulants for cancer-associated thrombosis are limited. Objectives The primary objective of this study was to determine the rate of recurrent cancer-associated thrombosis and major bleeding within 6 months of starting either low-molecular-weight heparin or direct oral anticoagulant for treatment of cancer-associated thrombosis. Secondary objectives were to determine the rates of clinically relevant-non-major bleeding and all-cause mortality. Patients/methods This is a retrospective cohort study including adults with cancer-associated thrombosis treated with low-molecular-weight heparin or direct oral anticoagulant between 2010 and 2016 at the Ohio State University. Medical records were reviewed for 6 months after initiation of anticoagulation or until the occurrence of recurrent cancer-associated thrombosis, major bleeding, cessation of anticoagulation of interest, or death, whichever occurred first. Results Four hundred and eighty patients were included (290 low-molecular-weight heparin and 190 direct oral anticoagulant). Patients treated with direct oral anticoagulant were found to carry "lower risk" features including cancer with lower VTE risk and lower rate of metastatic disease. After adjustment for baseline differences, there was no significant difference in the rate of recurrent cancer-associated thrombosis (7.2% low-molecular-weight heparin vs 6.3% direct oral anticoagulant, p = 0.71) or major bleeding (7.6% low-molecular-weight heparin vs 2.6% direct oral anticoagulant, p = 0.08). Conclusions Our study demonstrates that in a select population of cancer patients with VTE, direct oral anticoagulant use can be as effective and safe compared to the standard therapy with low-molecular-weight heparin.

The effect of different extraction techniques on property and bioactivity of polysaccharides from Dioscorea hemsleyi.

PubMed

Zhao, Chengcheng; Li, Xia; Miao, Jing; Jing, Songsong; Li, Xuejiao; Huang, Luqi; Gao, Wenyuan

2017-09-01

The rhizoma of Dioscorea hemsleyi (DH) has been used as a treatment of diabetes in China for hundreds of years. Polysaccharides in DH were extracted by using ultrasonic-assisted extraction (UAE), cold water extraction (CWE), warm water extraction (WWE) and hot water extraction (HWE), separately. Then the different characterizations of four DH polysaccharide (DHP) samples were analyzed by high-performance liquid chromatography (HPLC), high-performance Gel permeation chromatography (HGPC), ultraviolet-visible spectroscopy(UV), fourier transform-infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Their activities in vitro of DHP were compared. Experimental results showed that HWE had the highest yield and large molecular weight. CWE had the highest uronic acid yield and little molecular weight, and its DPPH, AGI and AAI activity were the best. The molecular weight of UAE was small, and its RP and FRAP activity were the best. Four DHP samples had differences in the surface topography, while they all had the typical IR spectra characteristic of polysaccharides. According the correlation analysis, it showed that the more uronic acid and the lower molecular weight was, the higher the antioxidant activity was. The high content of monosaccharide composition of Xyl, Ara, GlcA and GalA, and little molecular weight have good effect on antidiabetic activity. Copyright © 2017 Elsevier B.V. All rights reserved.

Hyaluronic Acid Molecular Weight-Dependent Modulation of Mucin Nanostructure for Potential Mucosal Therapeutic Applications.

PubMed

Hansen, Irene M; Ebbesen, Morten F; Kaspersen, Liselotte; Thomsen, Troels; Bienk, Konrad; Cai, Yunpeng; Malle, Birgitte Mølholm; Howard, Kenneth A

2017-07-03

This study investigates the effects of different molecular weight hyaluronic acids (HAs) on the mucosal nanostructure using a pig stomach mucin hydrogel as a mucosal barrier model. Microparticles (1.0 μm) and nanoparticles (200 nm) were used as probes, and their movement in mucin was studied by a three-dimensional confocal microscopy-based particle tracking technique and by Nanoparticle Tracking Analysis (NTA) after addition of high-molecular weight (900 kDa) and low-molecular weight (33 kDa) HA. This demonstrated a molecular weight-dependent HA modulation of the mucin nanostructure with a 2.5-fold decrease in the mobility of 200 nm nanoparticles. To further investigate these mechanisms and to verify that the natural viscoelastic properties of mucus are not undesirably altered, rheological measurements were performed on mucin hydrogels with or without HA. This suggested the observed particle mobility restriction was not attributed to alterations of the natural mucin cohesive and viscoelastic properties but, instead, indicates that the added high-molecular weight HA primarily modulates the mucin nanostructure and mesh size. This study, hereby, demonstrates how mucus nanostructure can be modulated by the addition of high-molecular weight HA that offers an opportunity to control mucosal pathogenesis and drug delivery.

Improving of Mechanical and Shape-Memory Properties in Hyperbranched Epoxy Shape-Memory Polymers

NASA Astrophysics Data System (ADS)

Santiago, David; Fabregat-Sanjuan, Albert; Ferrando, Francesc; De la Flor, Silvia

2016-09-01

A series of shape-memory epoxy polymers were synthesized using an aliphatic amine and two different commercial hyperbranched poly(ethyleneimine)s with different molecular weights as crosslinking agents. Thermal, mechanical, and shape-memory properties in materials modified with different hyperbranched polymers were analyzed and compared in order to establish the effect of the structure and the molecular weight of the hyperbranched polymers used. The presence of hyperbranched polymers led to more heterogeneous networks, and the crosslinking densities of which increase as the hyperbranched polymer content increases. The transition temperatures can be tailored from 56 to 117 °C depending on the molecular weight and content of the hyperbranched polymer. The mechanical properties showed excellent values in all formulations at room temperature and, specially, at T_{{g}}^{{E^' with stress at break as high as 15 MPa and strain at break as high as 60 %. The shape-memory performances revealed recovery ratios around 95 %, fixity ratios around 97 %, and shape-recovery velocities as high as 22 %/min. The results obtained in this study reveal that hyperbranched polymers with different molecular weights can be used to enhance the thermal and mechanical properties of epoxy-based SMPs while keeping excellent shape-memory properties.

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

USGS Publications Warehouse

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

2004-01-01

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

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. Copyright © 2014 Elsevier B.V. All rights reserved.

Molecular structure of the pyruvate dehydrogenase complex from Escherichia coli K-12.

PubMed

Vogel, O; Hoehn, B; Henning, U

1972-06-01

The pyruvate dehydrogenase core complex from E. coli K-12, defined as the multienzyme complex that can be obtained with a unique polypeptide chain composition, has a molecular weight of 3.75 x 10(6). All results obtained agree with the following numerology. The core complex consists of 48 polypeptide chains. There are 16 chains (molecular weight = 100,000) of the pyruvate dehydrogenase component, 16 chains (molecular weight = 80,000) of the dihydrolipoamide dehydrogenase component, and 16 chains (molecular weight = 56,000) of the dihydrolipoamide dehydrogenase component. Usually, but not always, pyruvate dehydrogenase complex is produced in vivo containing at least 2-3 mol more of dimers of the pyruvate dehydrogenase component than the stoichiometric ratio with respect to the core complex. This "excess" component is bound differently than are the eight dimers in the core complex.

The Cuban scorpion Rhopalurus junceus (Scorpiones, Buthidae): component variations in venom samples collected in different geographical areas

PubMed Central

2013-01-01

Backgound The venom of the Cuban scorpion Rhopalurus junceus is poorly study from the point of view of their components at molecular level and the functions associated. The purpose of this article was to conduct a proteomic analysis of venom components from scorpions collected in different geographical areas of the country. Results Venom from the blue scorpion, as it is called, was collected separately from specimens of five distinct Cuban towns (Moa, La Poa, Limonar, El Chote and Farallones) of the Nipe-Sagua-Baracoa mountain massif and fractionated by high performance liquid chromatography (HPLC); the molecular masses of each fraction were ascertained by mass spectrometry analysis. At least 153 different molecular mass components were identified among the five samples analyzed. Molecular masses varied from 466 to 19755 Da. Scorpion HPLC profiles differed among these different geographical locations and the predominant molecular masses of their components. The most evident differences are in the relative concentration of the venom components. The most abundant components presented molecular weights around 4 kDa, known to be K+-channel specific peptides, and 7 kDa, known to be Na+-channel specific peptides, but with small molecular weight differences. Approximately 30 peptides found in venom samples from the different geographical areas are identical, supporting the idea that they all probably belong to the same species, with some interpopulational variations. Differences were also found in the presence of phospholipase, found in venoms from the Poa area (molecular weights on the order of 14 to 19 kDa). The only ubiquitous enzyme identified in the venoms from all five localities studied (hyaluronidase) presented the same 45 kD molecular mass, identified by gel electrophoresis analysis. Conclusions The venom of these scorpions from different geographical areas seem to be similar, and are rich in peptides that have of the same molecular masses of the peptides purified from other scorpions that affect ion-channel functions. PMID:23849540

High and low molecular weight hyaluronic acid differentially influence macrophage activation

PubMed Central

Rayahin, Jamie E.; Buhrman, Jason S.; Zhang, Yu; Koh, Timothy J.; Gemeinhart, Richard A.

2015-01-01

Macrophages exhibit phenotypic diversity permitting wide-ranging roles in maintaining physiologic homeostasis. Hyaluronic acid, a major glycosaminoglycan of the extracellular matrix, has been shown to have differential signaling based on its molecular weight. With this in mind, the main objective of this study was to elucidate the role of hyaluronic acid molecular weight on macrophage activation and reprogramming. Changes in macrophage activation were assessed by activation state selective marker measurement, specifically quantitative real time polymerase chain reaction, and cytokine enzyme-linked immunoassays, after macrophage treatment with differing molecular weights of hyaluronic acid under four conditions: the resting state, concurrent with classical activation, and following inflammation involving either classically or alternatively activated macrophages. Regardless of initial polarization state, low molecular weight hyaluronic acid induced a classically activated-like state, confirmed by up-regulation of pro-inflammatory genes, including nos2, tnf, il12b, and cd80, and enhanced secretion of nitric oxide and TNF-α. High molecular weight hyaluronic acid promoted an alternatively activated-like state, confirmed by up regulation of pro-resolving gene transcription, including arg1, il10, and mrc1, and enhanced arginase activity. Overall, our observations suggest that macrophages undergo phenotypic changes dependent on molecular weight of hyaluronan that correspond to either (1) pro-inflammatory response for low molecular weight HA or (2) pro-resolving response for high molecular weight HA. These observations bring significant further understanding of the influence of extracellular matrix polymers, hyaluronic acid in particular, on regulating the inflammatory response of macrophages. This knowledge can be used to guide the design of HA-containing biomaterials to better utilize the natural response to HAs. PMID:26280020

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 eight amino acids or combinations of amino acids) is more uniform in the HMW of the four samples compared to lower-molecular-weight fractions. The greater "compositional stability" of the HMW indicates that it contains a residuum of macromolecules that have not been affected by the diagenetically driven changes observed in lower-molecular-weight fractions.

Pectinase hydrolysis of Dendrobium huoshanense polysaccharide and its effect on protein nonenzymatic glycation.

PubMed

Zha, Xue-Qiang; Li, Xiao-Long; Zhang, Hai-Lin; Cui, Shao-Hua; Liu, Jian; Wang, Jun-Hui; Pan, Li-Hua; Luo, Jian-Ping

2013-10-01

The aim of this study was to investigate the inhibitory effects of molecular weight alteration of Dendrobium huoshanense polysaccharide on protein nonenzymatic glycation. For this purpose, one homogeneous active polysaccharide DHPD1 with molecular weight 3.2 kDa was extracted from D. huoshanense. GC analysis showed that DHPD1 was mainly composed of glucose, arabinose, galactose in a molar ratio of 0.023:1.023:0.021 with a trace of mannose and xylose. In order to get DHPD1-derived fragments with different molecular weight, response surface methodology was employed to optimize the enzymatic degradation conditions. The maximum reducing sugar production (0.399 mg/mL) was obtained under an optimal condition including pectinase dosage 126 U/mL, reaction pH 4.46 and reaction temperature 48 °C. By applying this condition, three DHPD1-derived fragments with different molecular weights were obtained through changing the hydrolysis time. Infrared spectroscopy analysis indicated that the backbone structure of DHPD1 was not destroyed by pectinase hydrolysis. Monosaccharide composition analysis showed that pectinase preferred to liberate glucose from DHPD1. The inhibitory action of DHPD1 on protein nonenzymatic glycation reduced with the decrease of molecular weight. Copyright © 2013 Elsevier B.V. All rights reserved.

The polysaccharide and low molecular weight components of Opuntia ficus indica cladodes: Structure and skin repairing properties.

PubMed

Di Lorenzo, Flaviana; Silipo, Alba; Molinaro, Antonio; Parrilli, Michelangelo; Schiraldi, Chiara; D'Agostino, Antonella; Izzo, Elisabetta; Rizza, Luisa; Bonina, Andrea; Bonina, Francesco; Lanzetta, Rosa

2017-02-10

The Opuntia ficus-indica multiple properties are reflected in the increasing interest of chemists in the identification of its natural components having pharmaceutical and/or cosmetical applications. Here we report the structural elucidation of Opuntia ficus-indica mucilage that highlighted the presence of components differing for their chemical nature and the molecular weight distribution. The high molecular weight components were identified as a linear galactan polymer and a highly branched xyloarabinan. The low molecular weight components were identified as lactic acid, D-mannitol, piscidic, eucomic and 2-hydroxy-4-(4'-hydroxyphenyl)-butanoic acids. A wound healing assay was performed in order to test the cicatrizing properties of the various components, highlighting the ability of these latter to fasten dermal regeneration using a simplified in vitro cellular model based on a scratched keratinocytes monolayer. The results showed that the whole Opuntia mucilage and the low molecular weight components are active in the wound repair. Copyright © 2016 Elsevier Ltd. All rights reserved.

High-molecular-weight polymers for protein crystallization: poly-γ-glutamic acid-based precipitants

PubMed Central

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

2008-01-01

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-γ-­glutamic acid (PGA) polymers with different molecular-weight ranges is reported here: PGA-LM (low molecular weight) of ∼400 kDa and PGA-HM (high molecular weight) of >1000 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. PMID:18703844

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.

Intra-articular viscosupplementation of hyaluronic acids in an experimental osteoarthritis model.

PubMed

Oliveira, Marcello Zaia; Albano, Mauro Batista; Stirma, Guilherme Augusto; Namba, Mario Massatomo; Vidigal, Leandro; Cunha, Luiz Antonio Munhoz da

2018-01-01

To analyze, from the immunohistochemical perspective, the effects of hyaluronic acid of different molecular weights in an experimental model of osteoarthritis in rabbits. Forty-four male California rabbits were randomly assigned to three different groups (PR, S, and P) and submitted to the resection of the anterior cruciate ligament of the right knee. Three weeks after the surgical procedure, three intra-articular weekly injections were carried out with low-molecular-weight native hyaluronic acid (Hyalgan ® ) to PR group, high molecular weight branched chain hyaluronic acid (Synvisc ® ) to group S, and saline solution 0.9% to group P. All animals were sacrificed 12 weeks after the surgical procedure, and the tibial plateaus of the infiltrated knees were then dissected. Histological sections of cartilage from the tibial plateau support areas were stained with immunohistochemical markers in order to investigate the amount of metalloproteases (MMPs 3 and 13) and their inhibitors (TIMPs 1 and 3). The staining intensity was quantified on a Zeiss Imager.Z2 Metasystems microscope and analyzed by Metafer4 Msearch software. The chondroprotective effect of the hyaluronic acids used in the study was demonstrated when compared to the control group. However, the comparison between them presented no significant statistical difference regarding chondroprotection. The injection of saline solution demonstrated signs of OA development, while adding native hyaluronic acid of low molecular weight (Hyalgan ® ) and hyaluronic acid of high molecular weight (Synvisc ® ) protected the articular cartilage in this model of OA.

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

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. Copyright © 2016 Elsevier B.V. All rights reserved.

Molecular Structure of the Pyruvate Dehydrogenase Complex from Escherichia coli K-12

PubMed Central

Vogel, Otto; Hoehn, Barbara; Henning, Ulf

1972-01-01

The pyruvate dehydrogenase core complex from E. coli K-12, defined as the multienzyme complex that can be obtained with a unique polypeptide chain composition, has a molecular weight of 3.75 × 106. All results obtained agree with the following numerology. The core complex consists of 48 polypeptide chains. There are 16 chains (molecular weight = 100,000) of the pyruvate dehydrogenase component, 16 chains (molecular weight = 80,000) of the dihydrolipoamide dehydrogenase component, and 16 chains (molecular weight = 56,000) of the dihydrolipoamide dehydrogenase component. Usually, but not always, pyruvate dehydrogenase complex is produced in vivo containing at least 2-3 mol more of dimers of the pyruvate dehydrogenase component than the stoichiometric ratio with respect to the core complex. This “excess” component is bound differently than are the eight dimers in the core complex. Images PMID:4556465

A global survey of low-molecular weight carbohydrates in lentils

USDA-ARS?s Scientific Manuscript database

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...

Correlation of the physicochemical properties of natural organic matter samples from different sources to their effects on gold nanoparticle aggregation in monovalent electrolyte.

PubMed

Louie, Stacey M; Spielman-Sun, Eleanor R; Small, Mitchell J; Tilton, Robert D; Lowry, Gregory V

2015-02-17

Engineered nanoparticles (NPs) released into natural environments will interact with natural organic matter (NOM) or humic substances, which will change their fate and transport behavior. Quantitative predictions of the effects of NOM are difficult because of its heterogeneity and variability. Here, the effects of six types of NOM and molecular weight fractions of each on the aggregation of citrate-stabilized gold NPs are investigated. Correlations of NP aggregation rates with electrophoretic mobility and the molecular weight distribution and chemical attributes of NOM (including UV absorptivity or aromaticity, functional group content, and fluorescence) are assessed. In general, the >100 kg/mol components provide better stability than lower molecular weight components for each type of NOM, and they contribute to the stabilizing effect of the unfractionated NOM even in small proportions. In many cases, unfractionated NOM provided better stability than its separated components, indicating a synergistic effect between the high and low molecular weight fractions for NP stabilization. Weight-averaged molecular weight was the best single explanatory variable for NP aggregation rates across all NOM types and molecular weight fractions. NP aggregation showed poorer correlation with UV absorptivity, but the exponential slope of the UV-vis absorbance spectrum was a better surrogate for molecular weight. Functional group data (including reduced sulfur and total nitrogen content) were explored as possible secondary parameters to explain the strong stabilizing effect of a low molecular weight Pony Lake fulvic acid sample to the gold NPs. These results can inform future correlations and measurement requirements to predict NP attachment in the presence of NOM.

Middle molecules and small-molecular-weight proteins in ESRD: properties and strategies for their removal.

PubMed

Clark, William R; Winchester, James F

2003-10-01

Molecular weight has traditionally been the parameter most commonly used to classify uremic toxins, with a value of approximately 500 Da frequently used as a demarcation point below which the molecular weights of small nitrogenous waste products fall. This toxin group, the most extensively studied from a clinical perspective, is characterized by a high degree of water solubility and the absence of protein binding. However, uremia is mediated by the retention of a plethora of other compounds having characteristics that differ significantly from those of the previously mentioned group. As opposed to the relative homogeneity of the nitrogenous metabolite class, other uremic toxins collectively are a very heterogeneous group, not only with respect to molecular weight but also other characteristics, such as protein binding and hydrophobicity. A recently proposed classification scheme by the European Uraemic Toxin Work Group subdivides the remainder of molecules into 2 categories: protein-bound solutes and middle molecules. For the latter group, the Work Group proposes a molecular weight range (500-60,000 Da) that incorporates many toxins identified since the original middle molecule hypothesis, for which the upper molecular weight limit was approximately 2,000 Da. In fact, low-molecular-weight peptides and proteins (LMWPs) comprise nearly the entire middle molecule category in the new scheme. The purpose of this article is to provide an overview of the middle molecule class of uremic toxins, with the focus on LMWPs. A brief review of LMWP metabolism under conditions of normal (and in a few cases, abnormal) renal function will be presented. The physical characteristics of several LMWPs will also be presented, including molecular weight, conformation, and charge. Specific LMWPs to be covered will include beta 2-microglobulin, complement proteins (C3a and Factor D), leptin, and proinflammatory cytokines. The article will also include a discussion of the treatment-related factors influencing dialytic removal of middle molecules. Once these factors, which include membrane characteristics, protein-membrane interactions, and solute removal mechanisms, are discussed, an overview of the different therapeutic strategies used to enhance clearance of these compounds is provided.

Linear rheology and structure of molecular bottlebrushes with short side chains

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

López-Barrón, Carlos R., E-mail: carlos.r.lopez-barron@exxonmobil.com; Brant, Patrick; Crowther, Donna J.

We investigate the microstructure and linear viscoelasticity of model molecular bottlebrushes (BBs) using rheological and small-angle X-ray and neutron scattering measurements. Our polymers have short atactic polypropylene (aPP) side chains of molecular weight ranging from 119 g/mol to 259 g/mol and narrow molecular weight distribution (M{sub w}/M{sub n} 1.02–1.05). The side chain molecular weights are a small fraction of the entanglement molecular weight of the corresponding linear polymer (M{sub e,aPP}= 7.05 kg/mol), and as such, they are unentangled. The morphology of the aPP BBs is characterized as semiflexible thick chains with small side chain interdigitation. Their dynamic master curves, obtained by time-temperature superposition,more » reveal two sequential relaxation processes corresponding to the segmental relaxation and the relaxation of the BB backbone. Due to the short length of the side chains, their fast relaxation could not be distinguished from the glassy relaxation. The fractional free volume is an increasing function of the side chain length (N{sub SC}). Therefore, the glassy behavior of these polymers as well as their molecular friction and dynamic properties are influenced by their N{sub SC} values. The apparent flow activation energies are a decreasing function of N{sub SC}, and their values explain the differences in zero-shear viscosity measured at different temperatures.« less

Synthesis and Thermal Degradation Studies of Melamine Formaldehyde Resins

PubMed Central

Ullah, Sami; Bustam, M. A.; Nadeem, M.; Tan, W. L.; Shariff, A. M.

2014-01-01

Melamine formaldehyde (MF) resins have been synthesized at different reaction temperature and pH values. Different molar ratios of melamine and formaldehyde were used to synthesize the corresponding resins. The prepared resin samples were characterized by using molecular weight determination viscometry and thermogravimetric analysis (TGA). The maximum percentage of solid content (69.7%) was obtained at pH 8.5 and 75°C temperature. The molecular weight of MF resin was increased with an increase of melamine monomer concentration. The highest residual weight 14.125 wt.% was obtained with sample 10. PMID:25436237

Yield, Esterification Degree and Molecular Weight Evaluation of Pectins Isolated from Orange and Grapefruit Peels under Different Conditions

PubMed Central

Sayah, Mohamed Yassine; Chabir, Rachida; Benyahia, Hamid; Rodi Kandri, Youssef; Ouazzani Chahdi, Fouad; Touzani, Hanan; Errachidi, Faouzi

2016-01-01

Orange (Citrus sinensis) and grapefruit (Citrus paradise) peels were used as a source of pectin, which was extracted under different conditions. The peels are used under two states: fresh and residual (after essential oil extraction). Organic acid (citric acid) and mineral acid (sulfuric acid) were used in the pectin extraction. The aim of this study is the evaluation the effect of extraction conditions on pectin yield, degree of esterification “DE” and on molecular weight “Mw”. Results showed that the pectin yield was higher using the residual peels. Moreover, both peels allow the obtainment of a high methoxyl pectin with DE >50%. The molecular weight was calculated using Mark-Houwink-Sakurada equation which describes its relationship with intrinsic viscosity. This later was determined using four equations; Huggins equation, kramer, Schulz-Blaschke and Martin equation. The molecular weight varied from 1.538 x1005 to 2.47x1005 g/mol for grapefruit pectin and from 1.639 x1005 to 2.471 x1005 g/mol for orange pectin. PMID:27644093

Vitamin K antagonists or low-molecular-weight heparin for the long term treatment of symptomatic venous thromboembolism.

PubMed

van der Heijden, J F; Hutten, B A; Büller, H R; Prins, M H

2002-01-01

People with venous thromboembolism are generally treated for five days with intravenous unfractionated heparin or subcutaneous low-molecular-weight heparin followed by three months of vitamin K antagonists treatment. Treatment with vitamin K antagonists requires regular laboratory measurements and some patients have contraindications for treatment. To evaluate the efficacy and safety of long-term treatment of venous thromboembolism with low-molecular-weight heparins compared to vitamin K antagonists. Searches of MEDLINE, EMBASE and ISI Web of Science, the Specialised Trials Register of the Cochrane Peripheral Vascular Disease Group and the Cochrane Controlled Trials Register were made and relevant journals were hand-searched. Additional trials were sought through communication with colleagues and pharmaceutical companies. Two reviewers evaluated studies independently for methodological quality. Two reviewers extracted data independently. Primary analysis concerned all trial participants during the period of randomized treatment. Separate analyses were performed for category I and category II studies; i.e. studies using similar treatments initially in both study arms, and those that did not; and the different periods of follow-up. All seven studies fulfilling our criteria combined, a statistically non-significant reduction in the risk of recurrent venous thromboembolism favoring low-molecular-weight heparin treatment (OR 0.70; 95% CI [0.42, 1.16]) was found. Analysis of pooled data for category I studies showed a non-significant reduction in the risk of recurrent venous thromboembolism favoring low-molecular-weight heparin treatment (OR 0.75; 95% CI [0.40, 1.39]). Omitting a potentially-confounded study, a statistically non-significant reduction in the risk of recurrent venous thromboembolism favoring vitamin K antagonist treatment remained (OR 1.95; 95% CI [0.74, 5.19]). All studies combined, the difference in bleeding significantly favored treatment with low-molecular-weight heparin (OR 0.38; 95% CI [0.15, 0.94]), however, considering only category I studies a non-significant trend favoring low-molecular-weight heparin remained (OR 0.80; 95% CI [0.21, 3.00]). No difference was observed in mortality (OR 1.13; 95% CI [0.47, 2.69]). Low-molecular-weight heparins are possibly as effective as vitamin K antagonists in preventing symptomatic venous thromboembolism after an episode of symptomatic deep venous thrombosis, but are much more expensive. Treatment with low-molecular-weight heparin is significantly safer than treatment with vitamin K antagonists and is possibly a safe alternative in some patients; especially those in geographically inaccessible places, reluctant to visit the thrombosis service regularly, or with contraindications to vitamin K antagonists. However, treatment with vitamin K antagonists remains the treatment of choice for the majority of patients.

Effect of molecular weight of polystyrensulfonic acid sodium salt polymers on the precipitation kinetics of sodium bicarbonate

NASA Astrophysics Data System (ADS)

Martínez-Cruz, Nancy; Carrillo-Romo, Felipe; Jaramillo-Vigueras, David

2004-10-01

This paper analyzes the effect of polystyrensulfonic acid sodium salt (NaPSS), obtained by kinetic precipitation from solutions of polymers of molecular weight 245 000 and 38 000 g mol-1 in sodium bicarbonate (NaHCO3) itself precipitated from synthetic brine. Crystal size, shape and the additive adsorbed are reported. X shaped and hexagonal prisms crystals with different aspect ratios were obtained. The results show that with increasing polymer concentration the crystal size decreases, from 0.27 to 0.48 mm. Additionally, the higher molecular weight polymer shows both higher adsorption capacity and higher crystal habit modification. Crystal shape patterns were similar for both polymers; however, the higher molecular weight material induced changes at lower concentration. It was observed that the precipitation rate reached a minimum with increasing additive concentration.

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.

Effects of molecular weight of natural organic matter on cadmium mobility in soil environments and its carbon isotope characteristics.

PubMed

Mahara, Y; Kubota, T; Wakayama, R; Nakano-Ohta, T; Nakamura, T

2007-11-15

We investigated the role of natural organic matter in cadmium mobility in soil environments. We collected the dissolved organic matter from two different types of natural waters: pond surface water, which is oxic, and deep anoxic groundwater. The collected organic matter was fractionated into four groups with molecular weights (unit: Da (Daltons)) of <1 x 10(3), 1-10 x 10(3), 10-100 x 10(3), and >100 x 10(3). The organic matter source was land plants, based on the carbon isotope ratios (delta(13)C/(12)C). The organic matter in surface water originated from presently growing land plants, based on (14)C dating, but the organic matter in deep groundwater originated from land plants that grew approximately 4000 years ago. However, some carbon was supplied by the high-molecular-weight fraction of humic substances in soil or sediments. Cadmium interacted in a system of siliceous sand, fractionated organic matter, and water. The lowest molecular weight fraction of organic matter (<1 x 10(3)) bound more cadmium than did the higher molecular weight fractions. Organic matter in deep groundwater was more strongly bound to cadmium than was organic matter in surface water. The binding behaviours of organic matter with cadmium depended on concentration, age, molecular weight, and degradation conditions of the organic matter in natural waters. Consequently, the dissolved, low-molecular-weight fraction in organic matter strongly influences cadmium migration and mobility in the environment.

Effect of polyethylene glycols on the trans-ungual delivery of terbinafine.

PubMed

Nair, Anroop B; Chakraborty, Bireswar; Murthy, S Narasimha

2010-12-01

Topical nail drug delivery could be improved by identifying potent chemical penetration enhancers. The purpose of this study was to assess the effect of polyethylene glycols (PEGs) on the trans-ungual delivery of terbinafine. In vitro permeation studies were carried out by passive and iontophoresis (0.5 mA/cm2) processes for a period of 1 h using gel formulations containing different molecular weight PEGs (30%w/w). The release of drug from the loaded nail plates and the possible mechanisms for the enhanced delivery was studied. Passive delivery using formulation with low molecular weight PEGs (200 and 400 MW) indicated moderate enhancement in the permeation and drug load in the nail plate, compared to the control formulation. However, the effect of low molecular weight PEGs was predominant during iontophoresis process with greater amount of terbinafine being permeated (≈35 µg/cm2) and loaded into the nail plate (≈2.7 µg/mg). However, little or no effect on drug delivery was observed with high molecular weight PEGs (1000- 3350 MW) in passive and iontophoresis processes. Release of drug from the nail plates loaded by iontophoresis using low molecular weight PEG (400 MW) exhibited sustain effect which continued over a period of 72 days. The enhancement in drug permeation by low molecular weight PEGs is likely due to their ability to lead to greater water uptake and swelling of nail. This study concluded that the low molecular weight PEGs are indeed a promising trans-ungual permeation enhancer.

Comparative investigation of low-molecular-weight fulvic acids of different origin by SEC-Q-TOF-ms: new insights into structure and formation.

PubMed

Reemtsma, Thorsten; These, Anja

2005-05-15

Size exclusion chromatography (SEC) coupled to electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS) was used to analyze the elemental composition and structure of low-molecular-weight fulvic acid molecules. It is shown that the set of hundreds of individual molecules form a homogeneous and structurally unique class of compounds that can be clearly differentiated from any other class of biogenic matter investigated to date. The molecular composition of low-molecular-weight fulvic acids in isolates of very different origin (surface water, groundwater, peat) is virtually indistinguishable. Significant and characteristic differences are, however, recognized when qualitative information and quantitative information provided by ESI-Q-TOF-MS are linked to each other. The relative frequency of the various molecules in each mixture can differ significantly, with the peat showing higher intensity of the aromatic and less carboxylated molecules of this set, whereas the aquatic fulvic acids show a strong contribution of the molecules with less aromaticity and a higher carboxylate content. The identity of fulvic acid molecules in isolates of different origin implies that no specific source material is required forfulvic acid formation but that they may be formed from different sources by different oxidative processes.

Counterion adsorption theory of dilute polyelectrolyte solutions: Apparent molecular weight, second virial coefficient, and intermolecular structure factor

PubMed Central

Muthukumar, M.

2012-01-01

Polyelectrolyte chains are well known to be strongly correlated even in extremely dilute solutions in the absence of additional strong electrolytes. Such correlations result in severe difficulties in interpreting light scattering measurements in the determination of the molecular weight, radius of gyration, and the second virial coefficient of charged macromolecules at lower ionic strengths from added strong electrolytes. By accounting for charge-regularization of the polyelectrolyte by the counterions, we present a theory of the apparent molecular weight, second virial coefficient, and the intermolecular structure factor in dilute polyelectrolyte solutions in terms of concentrations of the polymer and the added strong electrolyte. The counterion adsorption of the polyelectrolyte chains to differing levels at different concentrations of the strong electrolyte can lead to even an order of magnitude discrepancy in the molecular weight inferred from light scattering measurements. Based on counterion-mediated charge regularization, the second virial coefficient of the polyelectrolyte and the interchain structure factor are derived self-consistently. The effect of the interchain correlations, dominating at lower salt concentrations, on the inference of the radius of gyration and on molecular weight is derived. Conditions for the onset of nonmonotonic scattering wave vector dependence of scattered intensity upon lowering the electrolyte concentration and interpretation of the apparent radius of gyration are derived in terms of the counterion adsorption mechanism. PMID:22830728

Effects of polymer molecular weight on relative oral bioavailability of curcumin.

PubMed

Tsai, Yin-Meng; Chang-Liao, Wan-Ling; Chien, Chao-Feng; Lin, Lie-Chwen; Tsai, Tung-Hu

2012-01-01

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. 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. 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 (C(max)) 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. 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 enhance the bioavailability of water-insoluble pharmaceutical compounds and functional foods.

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 enhance the bioavailability of water-insoluble pharmaceutical compounds and functional foods. PMID:22745556

Flagellated bacterial motility in polymer solutions

PubMed Central

Martinez, Vincent A.; Schwarz-Linek, Jana; Reufer, Mathias; Wilson, Laurence G.; Morozov, Alexander N.; Poon, Wilson C. K.

2014-01-01

It is widely believed that the swimming speed, v, of many flagellated bacteria is a nonmonotonic function of the concentration, c, of high-molecular-weight linear polymers in aqueous solution, showing peaked v(c) curves. Pores in the polymer solution were suggested as the explanation. Quantifying this picture led to a theory that predicted peaked v(c) curves. Using high-throughput methods for characterizing motility, we measured v and the angular frequency of cell body rotation, Ω, of motile Escherichia coli as a function of polymer concentration in polyvinylpyrrolidone (PVP) and Ficoll solutions of different molecular weights. We find that nonmonotonic v(c) curves are typically due to low-molecular-weight impurities. After purification by dialysis, the measured v(c) and Ω(c) relations for all but the highest-molecular-weight PVP can be described in detail by Newtonian hydrodynamics. There is clear evidence for non-Newtonian effects in the highest-molecular-weight PVP solution. Calculations suggest that this is due to the fast-rotating flagella seeing a lower viscosity than the cell body, so that flagella can be seen as nano-rheometers for probing the non-Newtonian behavior of high polymer solutions on a molecular scale. PMID:25468981

An evaluation of the effects of PEO/PEG molecular weights on extruded alumina rods

NASA Astrophysics Data System (ADS)

Bolger, Nancy Beth

1998-12-01

Alumina rods were piston extruded from bodies containing polyethylene glycols (PEGs) and polyethylene oxides (PEOs) with molecular weights ranging from 1,300 to 3,800,000 g/mol. A blend of aluminas possessing different particle size distributions was evaluated with regard to its extrusion pressure by varying the amount of PEG/PEO addition. Behavior exhibited by the alumina blend was dependent upon the additive that was used. The higher molecular weight binders with average molecular weight of 200,000 g/mol and 3,350,000 g/mol displayed the most severe behaviors of near dilatant and dilatant respectively. Physical properties of the green and fired states, as well as the binder burnout, were investigated with the changing additions. Correlation between the green and fired strengths and the changing molecular weights were examined. The additive present influenced the surface properties of the rods, which affected the green strengths. The highest average molecular weight polyethylene glycols showed higher green strengths, while the lowest green strengths were observed for the high molecular weight polyethylene oxides. Fired strengths generally ranged from approximately 12,000 psi to 16,000 psi for additive batches. Alumina pellets containing twelve separate combinations of polyethylene glycol with polyethylene oxide were dry pressed. Physical properties of the green and fired states were examined. Statistical analysis was performed upon the data and seven combinations of polyethylene glycol with polyethylene oxide were deemed significant. These combinations in conjunction with the same alumina blend were then piston extruded. The addition of polyethylene glycol reduced the near dilatant behavior exhibited by the 200,000 g/mol average molecular weight polyethylene oxide. Dilatant behavior was completely eliminated from the 3,350,000 g/mol average molecular weight polyethylene oxide batches. Physical properties of the green and fired states were again investigated with the changing additions. Polyethylene oxide, in combination with polyethylene glycol, did show an increase in green strength versus the polyethylene oxide alone. Strengths were still lower than those displayed by the polyethylene glycols alone. Reductions or degradations in molecular weight of the polymers due to mixing and extrusion processes may account for lower green strength of bodies, especially those containing polyethylene oxides.

Histidinoalanine, a naturally occurring cross-link derived from phosphoserine and histidine residues in mineral-binding phosphoproteins.

PubMed

Marsh, M E

1986-05-06

Native mineral-containing phosphoprotein particles were isolated from the Heterodont bivalve Macrocallista nimbosa. The native particles are discrete structures about 40 nm in diameter which migrate as a single band during electrophoresis in agarose gels. Removal of the mineral component with ethylenediaminetetraacetic acid dissociates the native protein into nonidentical subunits. The lower molecular weight subunits, representing 8% of the total protein, were obtained by differential centrifugation. The native protein is characterized by a high content of aspartic acid, phosphoserine, phosphothreonine, histidine, and the bifunctional cross-linking residue histidinoalanine. The low molecular weight subunits have the same amino acid composition except for a reduction in histidinoalanine and a corresponding increase in phosphoserine and histidine residues, demonstrating that the alanine portion of the cross-link is derived from phosphoserine residues. Ion-exchange chromatography and molecular sieve chromatography show that the low molecular weight subunits have a similar charge density but differ in molecular weight, and the relative mobilities of the subunits on agarose gels indicate that they are polymers of a single phosphoprotein molecule. The minimum molecular weight of the monomer is about 140 000 on the basis of the amino acid composition. The high molecular weight subunits are rich in histidinoalanine and too large to be resolved by either molecular sieve chromatography or gel electrophoresis. On the basis of the ultrastructural, electrophoretic, chromatographic, and compositional evidence, native phosphoprotein particles are composed of subunits ionically cross-linked via divalent cations. These subunits are variable molecular weight aggregates of a single phosphoprotein molecule covalently cross-linked via histidinoalanine residues. Evidence for a nonenzymatic cross-linking mechanism is discussed.

Degradation behavior of, and tissue response to photo-crosslinked poly(trimethylene carbonate) networks.

PubMed

Rongen, Jan J; van Bochove, Bas; Hannink, Gerjon; Grijpma, Dirk W; Buma, Pieter

2016-11-01

Photo-crosslinked networks prepared from three-armed methacrylate functionalized PTMC oligomers (PTMC-tMA macromers) are attractive materials for developing an anatomically correct meniscus scaffold. In this study, we evaluated cell specific biocompatibility, in vitro and in vivo degradation behavior of, and tissue response to, such PTMC networks. By evaluating PTMC networks prepared from PTMC-tMA macromers of different molecular weights, we were able to assess the effect of macromer molecular weight on the degradation rate of the PTMC network obtained after photo-crosslinking. Three photo-crosslinked networks with different crosslinking densities were prepared using PTMC-tMA macromers with molecular weights 13.3, 17.8, and 26.7 kg/mol. Good cell biocompatibility was demonstrated in a proliferation assay with synovium derived cells. PTMC networks degraded slowly, but statistically significant, both in vitro as well as subcutaneously in rats. Networks prepared from macromers with higher molecular weights demonstrated increased degradation rates compared to networks prepared from initial macromers of lowest molecular weight. The degradation process took place via surface erosion. The PTMC networks showed good tissue tolerance during subcutaneous implantation, to which the tissue response was characterized by the presence of fibrous tissue and encapsulation of the implants. Concluding, we developed cell and tissue biocompatible, photo-crosslinked PTMC networks using PTMC-tMA macromers with relatively high molecular weights. These photo-crosslinked PTMC networks slowly degrade by a surface erosion process. Increasing the crosslinking density of these networks decreases the rate of surface degradation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2823-2832, 2016. © 2016 Wiley Periodicals, Inc.

A tunable pH-sensing system based on Ag nanoclusters capped by hyperbranched polyethyleneimine with different molecular weights.

PubMed

Qu, Fei; Zou, Xuan; Kong, Rongmei; You, Jinmao

2016-01-01

In this assay, a tunable pH sensing system was developed based on Ag nanoclusters (Ag NCs) capped by hyperbranched polyethyleneimine (PEI) with different molecular weights (abbreviated as Ag NC-PEIs). For instance, when the molecular weight of PEI was 600 or 1800, the fluorescence intensities of Ag NCs exhibited a linear fashion over the pH range 4.10-7.96; when the molecular weight of PEI was 25,000, the pH linear range was from 4.78 to 7.96; when the molecular weight of PEI was 70,000, the pH linear range was 6.09-8.95. According to the molecular weight of PEI 600/1800, 25,000, and 70,000, the color change point was pH 4.10-4.78, 5.33-6.09, and 6.09-6.80, respectively. Therefore, Ag NC-PEI 600 and 1800 were proper to acid conditions; Ag NC-PEI 25,000 was sensitive to weak acid media; while Ag NC-PEI 70,000 was adapted to neutral solution. The tunable and selective color change points brought an excellent feature of Ag NC-PEIs as visual pH indicators, which was flexible and applicable to a variety of environments. Besides, the ratios of absorbance at 415 nm and 268 nm of Ag NCs also showed linear relationships with pH variations. Therefore, there were three ways of this system for sensing pH values, including fluorescence assay, ultraviolet-visible measurement, and visual detection, suggesting that this tunable pH-sensing platform was more feasible, reliable, and accurate. Copyright © 2015 Elsevier B.V. All rights reserved.

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.

The silver nanowires synthesized using different molecule weight of polyvinyl pyrrolidone for controlling diameter and length by one-pot polyol method

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

Junaidi, E-mail: junaidi.1982@fmipa.unila.ac.id; Departement of Physics, Lampung University, Bandar Lampung; Triyana, K., E-mail: triyana@ugm.ac.id

In this paper, we report our investigation on the effect of the molecular weight and molar ratio of polyvinyl pyrrolidone (PVP) and silver nitrate (AgNO{sub 3}) for controlling diameter and length of the silver nanowires synthesized with a high-aspect-ratio. The silver nanowires synthesized by one-pot polyol method at a constant temperature oil bath of 130°C. Different molecule weights of PVP, i.e. 55 K, 360 K, and 1300 K were used combined with different molar ratios of [PVP:Ag]. The UV–vis spectrophotometry and Field-emission scanning electron microscopy (FE-SEM) were employed to characterize the silver nanowires. The results show that the molecular weightmore » and molar ratio of [PVP:Ag] are very important for controlling growth and properties of the silver nanowires. The diameter and length of silver nanowires are obtained 80 to 140 nm and 30 to 70 µm, respectively. The higher molecular weight of PVP, the greater diameter and length of silver nanowires.« less

Nanomorphology of P3HT:PCBM-based absorber layers of organic solar cells after different processing conditions analyzed by low-energy scanning transmission electron microscopy.

PubMed

Pfaff, Marina; Klein, Michael F G; Müller, Erich; Müller, Philipp; Colsmann, Alexander; Lemmer, Uli; Gerthsen, Dagmar

2012-12-01

In this study the nanomorphology of P3HT:PC61BM absorber layers of organic solar cells was studied as a function of the processing parameters and for P3HT with different molecular weight. For this purpose we apply scanning transmission electron microscopy (STEM) at low electron energies in a scanning electron microscope. This method exhibits sensitive material contrast in the high-angle annular dark-field (HAADF) mode, which is well suited to distinguish materials with similar densities and mean atomic numbers. The images taken with low-energy HAADF STEM are compared with conventional transmission electron microscopy and atomic force microscopy images to illustrate the capabilities of the different techniques. For the interpretation of the low-energy HAADF STEM images, a semiempirical equation is used to calculate the image intensities. The experiments show that the nanomorphology of the P3HT:PC61BM blends depends strongly on the molecular weight of the P3HT. Low-molecular-weight P3HT forms rod-like domains during annealing. In contrast, only small globular features are visible in samples containing high-molecular-weight P3HT, which do not change significantly after annealing at 150°C up to 30 min.

Hofmeister effect on thermo-responsive poly(propylene oxide): Role of polymer molecular weight and concentration.

PubMed

Moghaddam, Saeed Zajforoushan; Thormann, Esben

2016-03-01

Although a vast amount of research has been dedicated to investigate the Hofmeister effect on the stability of polymer solutions, a clear understanding of the role of polymer properties in this phenomenon is still missing. Here, the Hofmeister effect of NaCl (destabilizing) and NaSCN (stabilizing) salts on aqueous solutions of poly(propylene oxide) (PPO) is studied. Four different molecular weights of PPO were investigated, to determine how the variation in the polymer coil size affects the Hofmeister effect. The investigation was further conducted for different PPO concentrations, in order to understand the effect of inter-chain interactions on the response to addition of salt. The temperature-driven phase separation of the solutions was monitored by differential scanning calorimetry, which provides the precise value of the phase separation temperature, as well as the enthalpy change accompanied with the transition. It was observed that increasing the molecular weight weakens the effect of the both salts, which is interpreted in terms of a scaling law between the molecular weight and the accessible surface area of the polymers. Increasing the PPO concentration further diminished the NaCl effect, but amplified the NaSCN effect. This difference is attributed to an electrostatic stabilization mechanism in the case of NaSCN. Copyright © 2015 Elsevier Inc. All rights reserved.

Gas-film coefficients for streams

USGS Publications Warehouse

Rathbun, R.E.; Tai, D.Y.

1983-01-01

Equations for predicting the gas-film coefficient for the volatilization of organic solutes from streams are developed. The film coefficient is a function of windspeed and water temperature. The dependence of the coefficient on windspeed is determined from published information on the evaporation of water from a canal. The dependence of the coefficient on temperature is determined from laboratory studies on the evaporation of water. Procedures for adjusting the coefficients for different organic solutes are based on the molecular diffusion coefficient and the molecular weight. The molecular weight procedure is easiest to use because of the availability of molecular weights. However, the theoretical basis of the procedure is questionable. The diffusion coefficient procedure is supported by considerable data. Questions, however, remain regarding the exact dependence of the film coefficint on the diffusion coefficient. It is suggested that the diffusion coefficient procedure with a 0.68-power dependence be used when precise estimate of the gas-film coefficient are needed and that the molecular weight procedure be used when only approximate estimates are needed.

Fossil fuel combined cycle power generation method

DOEpatents

Labinov, Solomon D [Knoxville, TN; Armstrong, Timothy R [Clinton, TN; Judkins, Roddie R [Knoxville, TN

2008-10-21

A method for converting fuel energy to electricity includes the steps of converting a higher molecular weight gas into at least one mixed gas stream of lower average molecular weight including at least a first lower molecular weight gas and a second gas, the first and second gases being different gases, wherein the first lower molecular weight gas comprises H.sub.2 and the second gas comprises CO. The mixed gas is supplied to at least one turbine to produce electricity. The mixed gas stream is divided after the turbine into a first gas stream mainly comprising H.sub.2 and a second gas stream mainly comprising CO. The first and second gas streams are then electrochemically oxidized in separate fuel cells to produce electricity. A nuclear reactor can be used to supply at least a portion of the heat the required for the chemical conversion process.

Mammalian histidine decarboxylase; changes in molecular properties induced by oxidation and reduction.

PubMed

Hammar, L; Hjertén, S

1980-04-01

Histidine decarboxylase from a murine mastocytoma has been submitted to different separation methods. In these experiments the activity peaks were often very broad. This heterogeneity of the enzyme is traced back to the formation of aggregates, differing in apparent molecular weight by a multiple of about 55,000, as a result of oxidation. Under non-oxidative conditions the histidine decarboxylase activity is confined to one peak in both molecular sieve chromatography, hydrophic interaction chromatography, chromatography on hydroxy apatite, pore gradient electrophoresis and electrofocusing. The molecular weight of the enzyme is estimated to be 110,000 by pore gradient electrophoresis (alkylated enzyme). The isoelectric point is pH 4.9--5.0, determined by electrofocusing under reducing conditions.

THE INFLUENCE OF NONUNIFORM CLOUD COVER ON TRANSIT TRANSMISSION SPECTRA

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

Line, Michael R.; Parmentier, Vivien, E-mail: mrline@ucsc.edu

2016-03-20

We model the impact of nonuniform cloud cover on transit transmission spectra. Patchy clouds exist in nearly every solar system atmosphere, brown dwarfs, and transiting exoplanets. Our major findings suggest that fractional cloud coverage can exactly mimic high mean molecular weight atmospheres and vice versa over certain wavelength regions, in particular, over the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) bandpass (1.1–1.7 μm). We also find that patchy cloud coverage exhibits a signature that is different from uniform global clouds. Furthermore, we explain analytically why the “patchy cloud-high mean molecular weight” degeneracy exists. We also explore the degeneracy ofmore » nonuniform cloud coverage in atmospheric retrievals on both synthetic and real planets. We find from retrievals on a synthetic solar composition hot Jupiter with patchy clouds and a cloud-free high mean molecular weight warm Neptune that both cloud-free high mean molecular weight atmospheres and partially cloudy atmospheres can explain the data equally well. Another key finding is that the HST WFC3 transit transmission spectra of two well-observed objects, the hot Jupiter HD 189733b and the warm Neptune HAT-P-11b, can be explained well by solar composition atmospheres with patchy clouds without the need to invoke high mean molecular weight or global clouds. The degeneracy between high molecular weight and solar composition partially cloudy atmospheres can be broken by observing the molecular Rayleigh scattering differences between the two. Furthermore, the signature of partially cloudy limbs also appears as a ∼100 ppm residual in the ingress and egress of the transit light curves, provided that the transit timing is known to seconds.« less

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.

Separation of both fibrous and globular proteins on the basis of molecular weight using high-performance size exclusion chromatography.

PubMed

Barden, J A

1983-11-01

A high-performance size exclusion liquid chromatographic system has been used to separate proteins with different shapes solely on the basis of their molecular weights. After the effects of ionic and hydrophobic interactions with the stationary phase have been overcome, protein elution is normally governed by their effective size in solution. Conditions are described under which proteins, with isoelectric points within the normal operating pH range of the columns, are eluted independent of their Stokes' radii. Even fibrous proteins with axial ratios of 50 elute according to their known molecular weights over the range 2000-2,000,000.

A distance-controlled nanoparticle array using PEGylated ferritin

NASA Astrophysics Data System (ADS)

He, Chao; Uenuma, Mutsunori; Okamoto, Naofumi; Kamitake, Hiroki; Ishikawa, Yasuaki; Yamashita, Ichiro; Uraoka, Yukiharu

2014-12-01

A distance-controlled nanoparticle (NP) array was investigated using a simple spin coating process. It was found that the separation distance of NPs was controlled at the nanoscale by using polyethylene glycols (PEGs). Ferritin was used to synthesize NPs and carry them to a substrate by using the different molecular weight of PEGs. In order to control the distance of the NPs, PEGs with molecular weights of 2k, 5k, 10k and 20k were modified on ferritin with 10 mM ion strength and 0.01 mg ml-1 ferritin concentration. The separated distances of NPs increased along with increase in PEG molecular weight.

Fucoidan cytotoxicity against human breast cancer T47D cell line increases with higher level of sulfate ester group

NASA Astrophysics Data System (ADS)

Saepudin, Endang; Alfita Qosthalani, Fildzah; Sinurat, Ellya

2018-01-01

The anticancer activity of different sulfate ester group content in different molecular weight was examined. The anticancer activity was achieved in vitro on human breast cancer T47D cell line. Fucoidan with lower molecular weight (5.79 kDa) tends to have lower sulfate ester group content (8.69%) and resulted in higher IC50 value (184.22 μg/mL). While fucoidan with higher molecular weight (785.12 kDa) tends to have higher sulfate level (18.63%) and achieved lower IC50 value (75.69 μg/mL). The result showed that in order to maintain fucoidan cytotoxic activity against human breast cancer T47D cell line, the sulfate content should be remain high. Keywords: fucoidan, sulfate ester group, human breast cancer

Novel "omics" approach for study of low-abundance, low-molecular-weight components of a complex biological tissue: regional differences between chorionic and basal plates of the human placenta.

PubMed

Kedia, Komal; Nichols, Caitlin A; Thulin, Craig D; Graves, Steven W

2015-11-01

Tissue proteomics has relied heavily on two-dimensional gel electrophoresis, for protein separation and quantification, then single protein isolation, trypsin digestion, and mass spectrometric protein identification. Such methods are predominantly used for study of high-abundance, full-length proteins. Tissue peptidomics has recently been developed but is still used to study the most highly abundant species, often resulting in observation and identification of dozens of peptides only. Tissue lipidomics is likewise new, and reported studies are limited. We have developed an "omics" approach that enables over 7,000 low-molecular-weight, low-abundance species to be surveyed and have applied this to human placental tissue. Because the placenta is believed to be involved in complications of pregnancy, its proteomic evaluation is of substantial interest. In previous research on the placental proteome, abundant, high-molecular-weight proteins have been studied. Application of large-scale, global proteomics or peptidomics to the placenta have been limited, and would be challenging owing to the anatomic complexity and broad concentration range of proteins in this tissue. In our approach, involving protein depletion, capillary liquid chromatography, and tandem mass spectrometry, we attempted to identify molecular differences between two regions of the same placenta with only slightly different cellular composition. Our analysis revealed 16 species with statistically significant differences between the two regions. Tandem mass spectrometry enabled successful sequencing, or otherwise enabled chemical characterization, of twelve of these. The successful discovery and identification of regional differences between the expression of low-abundance, low-molecular weight biomolecules reveals the potential of our approach.

Top-down and bottom-up analysis of commercial enoxaparins.

PubMed

Liu, Xinyue; St Ange, Kalib; Lin, Lei; Zhang, Fuming; Chi, Lianli; Linhardt, Robert J

2017-01-13

A strategy for the comprehensive analysis of low molecular weight (LMW) heparins is described that relies on using an integrated top-down and bottom-up approach. Liquid chromatography-mass spectrometry, an essential component of this approach, is rapid, robust, and amenable to automated processing and interpretation. Nuclear magnetic resonance spectroscopy provides complementary top-down information on the chirality of the uronic acid residues comprising a low molecular weight heparin. Using our integrated approach four different low molecular weight heparins prepared from porcine heparin through chemical β-eliminative cleavage were comprehensively analyzed. Lovenox™ and Clexane™, the innovator versions of enoxaparin marketed in the US and Europe, respectively, and two generic enoxaparins, from Sandoz and Teva, were analyzed. The results which were supported by analysis of variation (ANOVA), while showing remarkable similarities between different versions of the product and good lot-to-lot consistency of each product, also detects subtle differences that may result from differences in their manufacturing processes or differences in the source (or parent) porcine heparin from which each product is prepared. Copyright © 2016 Elsevier B.V. All rights reserved.

An agarose gel electrophoretic method for analysis of hyaluronan molecular weight distribution.

PubMed

Lee, H G; Cowman, M K

1994-06-01

An electrophoretic method is described for determining the molecular weight distribution of hyaluronan (HA). The method involves separation of HA by electrophoresis on a 0.5% agarose gel, followed by detection of HA using the cationic dye Stains-All (3,3'-dimethyl-9-methyl-4,5,4'5'-dibenzothiacarbocyanine). The recommended sample load is 7 micrograms. Calibration of the method with HA standards of known molecular weight has established a linear relationship between electrophoretic mobility and the logarithm of the weight-average molecular weight over the range of approximately 0.2-6 x 10(6). The separated HA pattern may also be visualized after electrotransfer of HA from the agarose gel to a nylon membrane. The membrane may be stained with the dye alcian blue. Alternatively, specific detection of HA from impure samples can be achieved by probing the nylon membrane with biotin-labeled HA-binding protein and subsequent interaction with a streptavidin-linked gold reagent and silver staining for amplification. The electrophoretic method was used to analyze HA in two different liquid connective tissues. Normal human knee joint synovial fluid showed a narrow HA molecular weight distribution, with a peak at 6-7 x 10(6). Owl monkey vitreous HA also showed a narrow molecular weight distribution, with a peak at 5-6 x 10(6). These results agree well with available published data and indicate the applicability of the method to the analysis of impure HA samples which may be available in limited amounts.

Increasing the wear resistance of ultra-high molecular weight polyethylene by adding solid lubricating fillers

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

Panin, S. V., E-mail: svp@ispms.tsc.ru; Kornienko, L. A.; Poltaranin, M. A.

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.

Temperature dependence of viscoelasticity of crystalline cellulose with different molecular weights added to silicone elastomer

NASA Astrophysics Data System (ADS)

Sugino, Naoto; Nakajima, Shinya; Kameda, Takao; Takei, Satoshi; Hanabata, Makoto

2017-08-01

Silicone elastomers ( polydimethylsiloxane _ PDMS) are widely used in the field of imprint lithography and microcontactprinting (μCP). When performing microcontactprinting, the mechanical properties of the PCMS as a base material have a great influence on the performance of the device. Cellulose nanofibers having features of high strength, high elasticity and low coefficient of linear expansion have attracted attention in recent years due to their characteristics. Therefore, three types of crystalline cellulose having different molecular weights were added to PDMS to prepare a composite material, and dynamic viscoelasticity was measured using a rheometer. The PDMS with the highest molecular weight crystalline cellulose added exhibited smaller storage modulus than PDMS with other molecular weight added in all temperature ranges. Furthermore, when comparing PDMS to which crystalline cellulose was added and PDMS which is not added, the storage modulus of PDMS to which cellulose was added in the low temperature region was higher than that of PDMS to which it was not added, but it was reversed in the high temperature region It was a result. When used in a low temperature range (less than 150 ° C.), it can be said that cellulose can function as a reinforcing material for PDMS.

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.

Sequence control of phase separation and dewetting in PS/PVME blend thin films by changing molecular weight of PS.

PubMed

Xia, Tian; Qin, Yaping; Huang, Yajiang; Huang, Ting; Xu, Jianhui; Li, Youbing

2016-11-28

The morphology evolution mechanism of polystyrene (PS)/poly (vinyl methyl ether) (PVME) blend thin films with different PS molecular weights (M w ) was studied. It was found that the morphology evolution was closely related to the molecular weight asymmetry between PS and PVME. In the film where M w (PS) ≈ M w (PVME), dewetting happened at the interface between the bottom layer and substrate after SD phase separation. While in the film where M w (PS) > M w (PVME), dewetting happened at the interface between the middle PS/PVME blend layer and bottom PVME layer near the substrate prior to phase separation. The different sequences of phase separation and dewetting and different interface for dewetting occurrence were studied by regarding the competitive effects of viscoelasticity contrast between polymer components and preferential wetting between PVME and the substrate. The viscoelastic nature of the PS component played a crucial role in the sequence of phase separation and dewetting.

Oligomeric cationic polymethacrylates: a comparison of methods for determining molecular weight.

PubMed

Locock, Katherine E S; Meagher, Laurence; Haeussler, Matthias

2014-02-18

This study compares three common laboratory methods, size-exclusion chromatography (SEC), (1)H nuclear magnetic resonance (NMR), and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), to determine the molecular weight of oligomeric cationic copolymers. The potential bias for each method was examined across a series of polymers that varied in molecular weight and cationic character (both choice of cation (amine versus guanidine) and relative proportion present). SEC was found to be the least accurate, overestimating Mn by an average of 140%, owing to the lack of appropriate cationic standards available, and the complexity involved in estimating the hydrodynamic volume of copolymers. MALDI-TOF approximated Mn well for the highly monodisperse (Đ < 1.1), low molecular weight (degree of polymerization (DP) <50) species but appeared unsuitable for the largest polymers in the series due to the mass bias associated with the technique. (1)H NMR was found to most accurately estimate Mn in this study, differing to theoretical values by only 5.2%. (1)H NMR end-group analysis is therefore an inexpensive and facile, primary quantitative method to estimate the molecular weight of oliogomeric cationic polymethacrylates if suitably distinct end-groups signals are present in the spectrum.

Synthesis and Characterization of Gelatin-Based Crosslinkers for the Fabrication of Superabsorbent Hydrogels

PubMed Central

Amonpattaratkit, Penphitcha; Khunmanee, Sureerat; Kim, Dong Hyun; Park, Hansoo

2017-01-01

In this work, crosslinkers were prepared by conjugating high- and low-molecular-weight gelatin with different mole ratios of itaconic acid (IA) with double bonds. Then, the gelatin-itaconic acid (gelatin-IA) crosslinkers were compared with the gelatin-methacrylate (gelatin-MA) crosslinkers. The molecular weights and structures of gelatin-MA and gelatin-IA were confirmed using gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR). Additionally, the swelling ratio and biodegradation properties of the hydrogels using IA as starting monomers and gelatin-IA and gelatin-MA as crosslinkers were investigated. Both hydrogels prepared with high and low molecular weights of gelatin-IA showed higher swelling ratios than those prepared with the gelatin-MA. The results also showed that absorbent hydrogels with different biodegradabilities and swelling ratios could be prepared by changing the ratio of the gelatin-based crosslinkers. PMID:28773186

Characterization and antioxidant activities of polysaccharides from thirteen boletus mushrooms.

PubMed

Zhang, Lan; Hu, Yu; Duan, Xiaoyu; Tang, Tingting; Shen, Yingbin; Hu, Bin; Liu, Aiping; Chen, Hong; Li, Cheng; Liu, Yuntao

2018-07-01

Water-soluble polysaccharides were extracted from the caps and stipes of thirteen boletus mushrooms representing five different species collected in Southwest China. Investigations of their structures and antioxidant activities allowed an evaluation of structure-function relationships. The polysaccharides were composed mainly of the monosaccharides arabinose, xylose, mannose, glucose and galactose. Most samples displayed a broad molecular weight range, with significant differences observed between the molecular weight ranges of the polysaccharides from the caps and the stipes. FT-IR spectral analysis of the polysaccharides revealed that most of polysaccharides from boletus mushrooms (except Boletus edulis) contained a pyranose ring. The antioxidant activities of the polysaccharides in stipes showed a significant correlation with their monosaccharide composition, and were also related to their molecular weight and anomeric configuration. Suillellus luridus collected in Pingwu, Mianyang, Sichuan, China had remarkably superior antioxidant activity and might be developed as a natural antioxidant. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of critical molecular weight of PEO in epoxy/EPO blends as characterized by advanced DSC and solid-state NMR

NASA Astrophysics Data System (ADS)

Wang, Xiaoliang; Lu, Shoudong; Sun, Pingchuan; Xue, Gi

2013-03-01

The differential scanning calorimetry (DSC) and solid state NMR have been used to systematically study the length scale of the miscibility and local dynamics of the epoxy resin/poly(ethylene oxide) (ER/PEO) blends with different PEO molecular weight. By DSC, we found that the diffusion behavior of PEO with different Mw is an important factor in controlling these behaviors upon curing. We further employed two-dimensional 13C-{1H}PISEMA NMR experiment to elucidate the possible weak interaction and detailed local dynamics in ER/PEO blends. The CH2O group of PEO forms hydrogen bond with hydroxyl proton of cured-ER ether group, and its local dynamics frozen by such interaction. Our finding indicates that molecular weight (Mw) of PEO is a crucial factor in controlling the miscibility, chain dynamics and hydrogen bonding interaction in these blends.

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.

Roles of different IRES-dependent FGF2 isoforms in the acquisition of the major aggressive features of human metastatic melanoma.

PubMed

Andreucci, Elena; Bianchini, Francesca; Biagioni, Alessio; Del Rosso, Mario; Papucci, Laura; Schiavone, Nicola; Magnelli, Lucia

2017-01-01

Fibroblast growth factor 2 (FGF2) is involved in many physiological and pathological processes. Fgf2 deregulation contributes to the acquisition of malignant features of melanoma and other cancers. FGF2 is an alternative translation product expressed as five isoforms, a low-molecular-weight (18 KDa) and four high-molecular-weight (22, 22.5, 24, 34 KDa) isoforms, with different subcellular distributions. An internal ribosomal entry site (IRES) in its mRNA controls the translation of all the isoforms with the exception for the cap-dependent 34 KDa. The 18-KDa isoform has been extensively studied, while very few is known about the roles of high molecular weight isoforms. FGF2 is known to promote melanoma development and progression. To disclose the differential contribution of FGF2 isoforms in melanoma, we forced the expression of IRES-dependent low-molecular-weight (LMW, 18 KDa) and high-molecular-weight (HMW, 22, 22.5, 24 KDa) isoforms in a human metastatic melanoma cell line. This comparative study highlights that, while LMW isoform confers stem-like features to melanoma cells and promotes angiogenesis, HMW isoforms induce higher migratory ability and contribute to tumor perfusion by promoting vasculogenic mimicry (VM) when endothelial cell-driven angiogenesis is lacking. To conclude, FGF2 isoforms mainly behave in specific, antithetical manners, but can cooperate in different steps of tumor progression, providing melanoma cells with major malignant features. FGF2 is an alternative translation product expressed as different isoforms termed LMW and HMW. FGF2 is involved in melanoma development and progression. HMW FGF2 isoforms enhance in vitro motility of melanoma cells. LMW FGF2 confers stem-like features and increases in vivo metastasization. LMW FGF2 promotes angiogenesis while HMW FGF2 induces vasculogenic mimicry.

Effect of dark, hard, and vitreous kernel content on protein molecular weight distribution and on milling and breadmaking quality characteristics for hard spring wheat samples from diverse growing regions

USDA-ARS?s Scientific Manuscript database

Kernel vitreousness is an important grading characteristic for segregation of sub-classes of hard red spring (HRS) wheat in the U.S. This research investigated the protein molecular weight distribution (MWD), and flour and baking quality characteristics of different HRS wheat market sub-classes. T...

Viscoelastic properties of dendrimers in the melt from nonequlibrium molecular dynamics

NASA Astrophysics Data System (ADS)

Bosko, Jaroslaw T.; Todd, B. D.; Sadus, Richard J.

2004-12-01

The viscoelastic properties of dendrimers of generation 1-4 are studied using nonequilibrium molecular dynamics. Flow properties of dendrimer melts under shear are compared to systems composed of linear chain polymers of the same molecular weight, and the influence of molecular architecture is discussed. Rheological material properties, such as the shear viscosity and normal stress coefficients, are calculated and compared for both systems. We also calculate and compare the microscopic properties of both linear chain and dendrimer molecules, such as their molecular alignment, order parameters and rotational velocities. We find that the highly symmetric shape of dendrimers and their highly constrained geometry allows for substantial differences in their material properties compared to traditional linear polymers of equivalent molecular weight.

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

Removal of Anabaena spiroides by potassium permanganate pre-oxidation: effect on photosynthetic capacity and molecular weight distribution.

PubMed

Qiao, Junlian; Zhang, Xiaodong; Lv, Liping

2017-11-01

Bench scale tests were conducted to investigate the effect of potassium permanganate pre-oxidation on the photosynthetic activity and molecular weight distribution of Anabaena spiroides. Different concentrations of potassium permanganate were added into the suspension of Anabaena spiroides, one of the dominant algae in water bloom, and after pre-oxidation of permanganate for 1 h, the results show that the removal rate significantly increases by 33.99~36.35% compared to direct coagulation. Then, the algal characteristics, including photosynthetic ability, the changes in extracellular organic matter three-dimensional fluorescence, and the distribution of molecular weight were conducted and the results show that along with increasing concentration of potassium permanganate, the photosynthetic ability of algae decreases, more extracellular organic matter is secreted, and large molecular weight matter (humic-like and fulvic-like substances) are generated. Therefore, this study demonstrates that potassium permanganate could be used in addressing the algae-rich water.

Low molecular weight components in an aquatic humic substance as characterized by membrane dialysis and orbitrap mass spectrometry.

PubMed

Remucal, Christina K; Cory, Rose M; Sander, Michael; McNeill, Kristopher

2012-09-04

Suwannee River fulvic acid (SRFA) was dialyzed through a 100-500 molecular weight cutoff dialysis membrane, and the dialysate and retentate were analyzed by UV-visible absorption and high-resolution Orbitrap mass spectrometry (MS). A significant fraction (36% based on dissolved organic carbon) of SRFA passed through the dialysis membrane. The fraction of SRFA in the dialysate had a different UV-visible absorption spectrum and was enriched in low molecular weight molecules with a more aliphatic composition relative to the initial SRFA solution. Comparison of the SRFA spectra collected by Orbitrap MS and Fourier transform ion cyclotron resonance MS (FT-ICR MS) demonstrated that the mass accuracy of the Orbitrap MS is sufficient for determination of unique molecular formulas of compounds with masses <600 Da in a complex mixture, such as SRFA. The most intense masses detected by Orbitrap MS were found in the 100-200 Da mass range. Many of these low molecular masses corresponded to molecular formulas of previously identified compounds in organic matter, lignin, and plants, and the use of the standard addition method provided an upper concentration estimate of selected target compounds in SRFA. Collectively, these results provide evidence that SRFA contains low molecular weight components that are present individually or in loosely bound assemblies.

Decolorization/Deodorization of Zein via Activated Carbons and Molecular Sieves

USDA-ARS?s Scientific Manuscript database

A series of commercial activated carbons generated from different media and selective microporous zeolites with different pore sizes were used in a batch system to sequester the low molecular weight odor and color contaminants in commercial zein products. Because the adsorbents can also adsorb prot...

Effects of Temperature on Polymer/Carbon Chemical Sensors

NASA Technical Reports Server (NTRS)

Manfireda, Allison; Lara, Liana; Homer, Margie; Yen, Shiao-Pin; Kisor, Adam; Ryan, Margaret; Zhou, Hanying; Shevade, Abhijit; James, Lim; Manatt, Kenneth

2009-01-01

Experiments were conducted on the effects of temperature, polymer molecular weight, and carbon loading on the electrical resistances of polymer/carbon-black composite films. The experiment were performed in a continuing effort to develop such films as part of the JPL Electronic Nose (ENose), that would be used to detect, identify, and quantify parts-per-million (ppm) concentration levels of airborne chemicals in the space shuttle/space station environments. The polymers used in this study were three formulations of poly(ethylene oxide) [PEO] that had molecular weights of 20 kilodaltons, 600 kilodaltons, and 1 megadalton, respectively. The results of one set of experiments showed a correlation between the polymer molecular weight and the percolation threshold. In a second set of experiments, differences among the temperature dependences of resistance were observed for different carbon loadings; these differences could be explained by a change in the conduction mechanism. In a third set of experiments, the responses of six different polymer/carbon composite sensors to three analytes (water vapor, methanol, methane) were measured as a function of temperature (28 to 36 C). For a given concentration of each analyte, the response of each sensor decreased with increasing temperature, in a manner different from those of the other sensors.

Influence of molecular size and osmolarity of sugars and dextrans on the synthesis of outer membrane proteins O-8 and O-9 of Escherichia coli K-12.

PubMed Central

Kawaji, H; Mizuno, T; Mizushima, S

1979-01-01

Supplementation of the growth medium with high concentrations of sugars or low-molecular-weight dextrans results in a drastic change in the ratio of outer membrane proteins O-8 and O-9, due to induction of O-8 synthesis and suppression of O-9 synthesis. Sugars and dextrans of molecular weights greater than 600 to 700 switched the synthesis of O-9 to that of O-8 more effectively than those of lower molecular weight, although the effect was almost the same within each of the two groups irrespective of the differences in molecular weight within the group. Proteins O-8 or O-9, or both, are responsible for the formation of pores that allow the passive diffusion of hydrophilic molecules whose molecular weights are smaller than about 600 (T. Nakae, Biochem. Biophys. Res. Commun. 71:877-884, 1976). The results indicate that substances that cannot pass through the outer membrane switch the synthesis of O-9 to that of O-8 more effectively than those that can penetrate this membrane with the aid of O-8, O-9, or both. It is suggested that the osmotic pressure exerted on the outer membrane plays an important role in the regulation of synthesis of the two proteins. PMID:391802

Isolation and characterization of EMS-induced Dy10 and Ax1 high molecular weight glutenin subunit deficient mutant lines of elite hexaploid wheat (Triticum aestivum L.) cv. Summit

USDA-ARS?s Scientific Manuscript database

The mixing properties of the dough are critical in the production of bread and other food products derived from wheat. The high molecular weight glutenin subunits (HMW-GS) are major determinants of wheat dough processing qualities. The different alleles of the HMW-GS genes in hexaploid wheat vary ...

Rapid screening of low-molecular-weight phenols from persimmon (Diospyros kaki) pulp using liquid chromatography/UV-visible/electrospray mass spectrometry analysis.

PubMed

Sentandreu, Enrique; Cerdán-Calero, Manuela; Halket, John M; Navarro, José L

2015-06-01

Persimmon fruits have been widely used in traditional medicine owing to their phenolic composition. This research aims to perform a rapid, detailed and affordable study of the profile of low-molecular-weight phenols from persimmon pulp. Two different HPLC-DAD/ESI-MS(n) analyses were performed using a routine three-dimensional ion trap mass spectrometer to analyze the ethanolic extract of persimmon pulp: (1) an untargeted data-dependent analysis to identify the majority of small phenols that included full MS and MS(2) scan events; (2) a targeted data-dependent analysis to identify polymerized phenols (dimers and formic acid adducts) through a source-induced dissociation analysis that included full MS and MS(2) scan events. Thirty-two low-molecular-weight phenols were detected, comprising gallic acid and its glycoside and acyl derivatives, glycosides of p-coumaric, vanillic and cinnamic acids and different flavone di-C-hexosides, most of them reported for the first time in persimmon. The use of a straightforward and affordable methodology of analysis led to obtain an up-to-date profiling of low-molecular-weight phenols in persimmon. The results can help future actions aimed to expand the understanding of the phenolic metabolome of persimmon cultivars. © 2014 Society of Chemical Industry.

Quantification of the inert chemical oxygen demand of raw wastewater and evaluation of soluble microbial product production in demo-scale upflow anaerobic sludge blanket reactors under different operational conditions.

PubMed

Aquino, Sergio F; Gloria, Roberto M; Silva, Silvana Q; Chernicharo, Carlos A L

2009-06-01

This paper investigates the production of soluble microbial products (SMPs) in demonstration-scale upflow anaerobic sludge blanket reactors operated under different conditions and fed with raw wastewater. The results showed that 9.2 +/- 1.3% of the influent soluble chemical oxygen demand (COD) could be considered inert to anaerobic treatment and that the amount of COD produced by biomass varied from 30 to 70 mg x L(-1), accounting for 45 to 63% of the soluble effluent COD. The accumulation of SMP appeared to be dependent on the hydraulic retention time (HRT) applied to the reactors, with a larger accumulation of SMP observed at the lowest HRT (5 hours); this may have been due to stress conditions caused by high upflow velocity (1.1 m x h(-1)). In terms of residual COD characterization, ultrafiltration results showed that higher amounts of high molecular weight compounds were found when HRT was the lowest (5 hours), and that the molecular weight distribution depended on the operational condition of the reactors. Biodegradability tests showed that the low and high molecular weight SMPs were only partially degraded anaerobically (10 to 60%) and that the high molecular weight SMPs were difficult to degrade aerobically.

Proteomic analysis of albumin and globulin fractions of pea (Pisum sativum L.) seeds.

PubMed

Dziuba, Jerzy; Szerszunowicz, Iwona; Nałęcz, Dorota; Dziuba, Marta

2014-01-01

Proteomic analysis is emerging as a highly useful tool in food research, including studies of food allergies. Two-dimensional gel electrophoresis involving isoelectric focusing and sodium dodecyl sulfate polyacrylamide gel electrophoresis is the most effective method of separating hundreds or even thousands of proteins. In this study, albumin and globulin tractions of pea seeds cv. Ramrod were subjected to proteomic analysis. Selected potentially alergenic proteins were identified based on their molecular weights and isoelectric points. Pea seeds (Pisum sativum L.) cv. Ramrod harvested over a period of two years (Plant Breeding Station in Piaski-Szelejewo) were used in the experiment. The isolated albumins, globulins and legumin and vicilin fractions of globulins were separated by two-dimensional gel electrophoresis. Proteomic images were analysed in the ImageMaster 2D Platinum program with the use of algorithms from the Melanie application. The relative content, isoelectric points and molecular weights were computed for all identified proteins. Electrophoregrams were analysed by matching spot positions from three independent replications. The proteomes of albumins, globulins and legumin and vicilin fractions of globulins produced up to several hundred spots (proteins). Spots most characteristic of a given fraction were identified by computer analysis and spot matching. The albumin proteome accumulated spots of relatively high intensity over a broad range of pi values of ~4.2-8.1 in 3 molecular weight (MW) ranges: I - high molecular-weight albumins with MW of ~50-110 kDa, II - average molecular-weight albumins with MW of ~20-35 kDa, and III - low molecular-weight albumins with MW of ~13-17 kDa. 2D gel electrophoregrams revealed the presence of 81 characteristic spots, including 24 characteristic of legumin and 14 - of vicilin. Two-dimensional gel electrophoresis proved to be a useful tool for identifying pea proteins. Patterns of spots with similar isoelectric points and different molecular weights or spots with different isoelectric points and similar molecular weights play an important role in proteome analysis. The regions characteristic of albumin, globulin and legumin and vicilin fractions of globulin with typical MW and pi values were identified as the results of performed 2D electrophoretic separations of pea proteins. 2D gel electrophoresis of albumins and the vicilin fraction of globulins revealed the presence of 4 and 2 spots, respectively, representing potentially allergenic proteins. They probably corresponded to vicilin fragments synthesized during post-translational modification of the analysed protein.

Chemical characteristics of dissolved organic matter (DOM) in relation to heavy metal concentrations in soil water from boreal peatlands after clear-cut harvesting

NASA Astrophysics Data System (ADS)

Kiikkilä, O.; Nieminen, T.; Starr, M.; Ukonmaanaho, L.

2012-04-01

Boreal peatlands form an important terrestrial carbon reserve and are a major source of dissolved organic matter (DOM) to surface waters, particularly when disturbed through forestry practices such as draining or timber harvesting. Heavy metals show a strong affinity to organic matter and so, along with DOM, heavy metals can be mobilized and transported from the soil to surface waters and sediments where they may become toxic to aquatic organisms and pass up the food chain. The complexation of heavy metals with DOM can be expected to be related and determined by the chemical characteristics of DOM and oxidation/reducing conditions in the peat. We extracted interstitial water from peat samples and determined the concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and Al, Cu, Zn and Fe in various fractions of DOM isolated by adsorption properties (XAD-8 fractionation) and molecular-weight (ultrafiltration). The peat samples were taken from 0-30 and 30-50 cm depth in drained peatland catchments two years after whole-tree or stem-only clear-cut harvesting (Scots pine or Norway spruce) had been carried out. The samples from the upper layer had been subject to alternating saturation/aeration conditions while the deeper layer had been continuously under the water table. The fractionation of DOC and DON according to both adsorption properties and molecular-weight fractions clearly differed between the upper and lower peat layers. While the hydrophobic acid fraction contained proportionally more DOC and DON than the hydrophilic acid fraction in the upper peat layer the results were vice versa in the lower peat layer. High-molecular-weight compounds (> 100 kDa) were proportionally more abundant in the upper and low-molecular-weight compounds (< 1 kDa) in the lower peat layer. These differences are assumed to reflect differences in the aerobic/ anaerobic conditions and degree of decomposition between the two layers. The concentrations of Zn, Al, Fe and DON correlated positively with DOC concentrations whereas the concentration Cu did not correlate with DOC concentrations. Heavy metal concentrations in different molecular-weight fractions indicated that Al, Cu, Zn and Fe were mostly associated with high-molecular-weight compounds and only a small fraction existed as free metal ions in solution. There were no clear differences in the chemical characteristics of DOC or DON or heavy metal concentrations between the two harvesting treatments.

Product Differences in Intra-articular Hyaluronic Acids for Osteoarthritis of the Knee.

PubMed

Altman, Roy D; Bedi, Asheesh; Karlsson, Jon; Sancheti, Parag; Schemitsch, Emil

2016-08-01

Knee osteoarthritis (OA) is a common and often disabling joint disorder among adults that may result in impaired activity and daily function. A variety of treatment options are currently available and prescribed for knee OA depending on the severity of the disorder and physician preference. Intra-articular hyaluronic acid (IA-HA) injection is a treatment for knee OA that reportedly provides numerous biochemical and biological benefits, including shock absorption, chondroprotection, and anti-inflammatory effects within the knee. Clarity is needed as to whether the available IA-HA products should be considered for therapy as a group or whether there are significant differences in the products that need to be considered in treatment of OA of the knee. To determine whether there are differences in efficacy and safety with respect to intrinsic properties of available IA-HA injections for knee OA. Meta-analysis. A comprehensive literature search of the Medline, EMBASE, and PubMed databases was conducted for all existing randomized trials of IA-HA. The primary outcome measure analyzed was the mean pain score at the reported follow-up nearest to 26 weeks after injection. Pooled efficacy and safety results were recorded for subgroupings of HA product characteristics. A total of 68 studies were included for analysis. Products with an average molecular weight ≥3000 kDa provided favorable efficacy results when compared with products of an average molecular weight <3000 kDa. Products with a molecular weight ≥3000 kDa demonstrated significantly fewer discontinuations due to treatment-related adverse events than did ≤1500 kDa counterparts, while trial discontinuation rates were similar between biological fermentation-derived HA products and avian-derived HA. The results did not demonstrate a significant difference in the occurrence of effusion across molecular weight subgroups. Additionally, biological fermentation-derived HA had a significantly smaller incidence of effusion than did avian-derived HA. Biological fermentation-derived HA demonstrated fewer acute flare-ups at the injection site than did avian-derived HA products, while high-molecular-weight products demonstrated the highest rate of injection site flare-up. Despite similarities, IA-HA products should not be treated as a group, as there are differences in IA-HA products that influence both efficacy and safety. In the available literature, IA-HA products with a molecular weight ≥3000 kDa and those derived from biological fermentation relate to superior efficacy and safety-factors that may influence selection an IA-HA product for OA of the knee. © 2015 The Author(s).

Polysaccharides and their depolymerized fragments from Costaria costata: Molecular weight and sulfation-dependent anticoagulant and FGF/FGFR signal activating activities.

PubMed

Hou, Ningning; Zhang, Meng; Xu, Yingjie; Sun, Zhongmin; Wang, Jing; Zhang, Lijuan; Zhang, Quanbin

2017-12-01

Crude polysaccharides from Costaria costata were extracted by hot water and further fractionated by anion exchange chromatography into three polysaccharide fractions. Three low molecular weight fragments were then prepared by degradation of the polysaccharides with hydrogen peroxide and ascorbic acid. The structural features of the polysaccharides and their low molecular weight fragments were elucidated for the first time based on the HGPC, FT-IR, NMR, MS, monosaccharide composition, and other chemical analyses. Their anticoagulant and FGF-1, -2, -7, -8, -9, -10/FGFR1c signaling activation activities in BaF3 cells were also examined. Our studies showed that the polysaccharides were sulfated at different positions of galactose and fucose residues. The APTT-, PT- and TT-based anticoagulant assay results indicated that a high molecular weight and a higher degree of sulfation were essential for their anticoagulant activities. In contrast, not only the polysaccharides but also the depolymerized fragments showed significant FGF/FGFR signal activating activities in a FGF-, molecular weight-, and sulfation-dependent manner. The results presented in current study demonstrated the potential use of the polysaccharides and their fragments as anticoagulants and FGF signal regulators. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of gel-filter method for high enrichment of low-molecular weight proteins from serum.

PubMed

Chen, Lingsheng; Zhai, Linhui; Li, Yanchang; Li, Ning; Zhang, Chengpu; Ping, Lingyan; Chang, Lei; Wu, Junzhu; Li, Xiangping; Shi, Deshun; Xu, Ping

2015-01-01

The human serum proteome has been extensively screened for biomarkers. However, the large dynamic range of protein concentrations in serum and the presence of highly abundant and large molecular weight proteins, make identification and detection changes in the amount of low-molecular weight proteins (LMW, molecular weight ≤ 30kDa) difficult. Here, we developed a gel-filter method including four layers of different concentration of tricine SDS-PAGE-based gels to block high-molecular weight proteins and enrich LMW proteins. By utilizing this method, we identified 1,576 proteins (n = 2) from 10 μL serum. Among them, 559 (n = 2) proteins belonged to LMW proteins. Furthermore, this gel-filter method could identify 67.4% and 39.8% more LMW proteins than that in representative methods of glycine SDS-PAGE and optimized-DS, respectively. By utilizing SILAC-AQUA approach with labeled recombinant protein as internal standard, the recovery rate for GST spiked in serum during the treatment of gel-filter, optimized-DS, and ProteoMiner was 33.1 ± 0.01%, 18.7 ± 0.01% and 9.6 ± 0.03%, respectively. These results demonstrate that the gel-filter method offers a rapid, highly reproducible and efficient approach for screening biomarkers from serum through proteomic analyses.

Chitosan-Copper (II) complex as antibacterial agent: synthesis, characterization and coordinating bond- activity correlation study

NASA Astrophysics Data System (ADS)

Mekahlia, S.; Bouzid, B.

2009-11-01

The antimicrobial activity of chitosan is unstable and sensitive to many factors such as molecular weight. Recent investigations showed that low molecular weight chitosan exhibited strong bactericidal activities compared to chitosan with high molecular weight. Since chitosan degradation can be caused by the coordinating bond, we attempt to synthesize and characterize the chitosan-Cu (II) complex, and thereafter study the coordinating bond effect on its antibacterial activity against Salmonella enteritidis. Seven chitosan-copper complexes with different copper contents were prepared and characterized by FT-IR, UV-vis, XRD and atomic absorption spectrophotometry (AAS). Results indicated that for chitosan-Cu (II) complexes with molar ratio close to 1:1, the inhibition rate reached 100%.

Bacterial attack on phenolic ethers. Purification and characterization of the components of the meta O-dealkylase of Pseudomonas fluorescens Tp.

PubMed

Pietrowski, R A; Cartwright, N J

1977-01-01

The meta O-dealkylase of Pseudomonas fluorescens Tp has been resolved into two protein components, neither of which is a cytochrome. The substrate binding terminal oxidase has been purified and shown to be a non-haem iron protein of approximate molecular weight 118,000, consisting of two seemingly identical subunits, each of molecular weight 55,000. Binding of substrate by the terminal oxidase has been established by difference spectroscopy. The amino acid composition of the protein has also been determined. The NADH-dependent reductase of the system has been partly purified and appears to have a molecular weight of 80,000. The similarity between this and other bacterial O-dealkylases is discussed.

Influence of polymeric carrier on the disposition and retention of 20(R)-ginsenoside-rg3-loaded swellable microparticles in the lung.

PubMed

Wang, Xiuhua; Zhang, Xiao; Fan, Linlin; He, Huan; Zhang, Xiaofei; Zhang, Yuyang; Mao, Shirui

2018-02-01

The objective of this study was to investigate the influence of differently charged biocompatible polymers, including chitosan (CS), hyaluronic acid (HA), and hydroxypropyl cellulose (HPC), on the disposition and retention of 20(R)-ginsenoside-rg3 (Rg3)-loaded swellable microparticles in the lung. A high-pressure homogenization method combined with spray drying was used to prepare Rg3-loaded microparticles. In vitro aerodynamic performance of different microparticles was characterized by the Next Generation Impactor (NGI). Retention of the swellable microparticles in the rat lung was investigated using bronchoalveolar lavage fluid method. Influence of drug loading, polymer molecular weight, and polymer charge on the properties of the swellable microparticles was investigated. It was found that drug loading had no significant influence on experimental mass median aerodynamic diameter (MMAD e ) and fine particle fraction (FPF). Increasing polymer molecular weight caused no remarkable change in MMAD e value, but the FPF value decreased with the increase of polymer molecular weight. At the same molecular weight level, polymer structure and charge had no statistical influence on the in vitro aerodynamic properties of the microparticles and lung disposition, but it influenced the swelling and bioadhesion behavior and therefore lung retention profile. Desirable phagocytosis escapement and inhibition of A549 cell proliferation were achieved for the developed swellable microparticles. In conclusion, the lung retention of swellable microparticles can be adjusted by selecting polymeric carriers with different structure and charge.

PALS Free Volume Measurements of Fractionated Hydrido- Silsesquioxane Resin.

NASA Astrophysics Data System (ADS)

Madani, Mahmoud M.; Granata, Richard D.; Pernisz, Udo C.

1997-03-01

Hydrido-Silsesquioxane (HSQ) is a resinous polymer with monomer unit formula (HSiO_3/2)_n. For n=8...16, it forms cages which in turn cross-link to yield a resin with a broad molecular weight distribution. It is soluble and forms thin films that may be converted to low-density silica with excellent dielectric properties. These, and the HSQ solubility, depend on molecular structure and size distribution of the cages. Samples of different molecular weight fractions were prepared from HSQ by SCF and the free volume of several cuts was measured by PALS in a conventional fast-fast system. POSITRONFIT and CONTIN programs were used to analyze the spectra. Three separate lifetime regions were identified with free volume regimes that correlate strongly with the molecular weight. The lowest is identified with the monomer cage unit, the larger values with intramolecular separation.

Detection of Diverse and High Molecular Weight Nesprin-1 and Nesprin-2 Isoforms Using Western Blotting.

PubMed

Carthew, James; Karakesisoglou, Iakowos

2016-01-01

Heavily utilized in cell and molecular biology, western blotting is considered a crucial technique for the detection and quantification of proteins within complex mixtures. In particular, the detection of members of the nesprin (nuclear envelope spectrin repeat protein) family has proven difficult to analyze due to their substantial isoform diversity, molecular weight variation, and the sheer size of both nesprin-1 and nesprin-2 giant protein variants (>800 kDa). Nesprin isoforms contain distinct domain signatures, perform differential cytoskeletal associations, occupy different subcellular compartments, and vary in their tissue expression profiles. This structural and functional variance highlights the need to distinguish between the full range of proteins within the nesprin protein family, allowing for greater understanding of their specific roles in cell biology and disease. Herein, we describe a western blotting protocol modified for the detection of low to high molecular weight (50-1000 kDa) nesprin proteins.

Effect of Fish Collagen Hydrolysates on Type I Collagen mRNA Levels of Human Dermal Fibroblast Culture

PubMed Central

Sanchez, Ana; Blanco, Maria; Correa, Begoña

2018-01-01

Fish discards and subproducts may represent an important source of raw material, not only for the food industry, but for other different kind of industries, such as the nutraceutical and cosmetic industries. Collagen, which is mainly obtained from animal skins, is an important structural protein in the animal kingdom having many different applications. It is well known that fish skins constitute a significant subproduct in the fishery industry, especially in the case of some species, where fish skins may represent up to 20% of the total body weight of fish. Peptides from collagen hydrolysates have been described to be useful for preventing skin aging and osteoarthritis, however, the mechanism for these biological activities is not well known. Fibroblasts are the main cell types involved in the collagen synthesis, and in the present work, human dermal fibroblasts have been exposed to the treatment of collagen peptides of two different molecular weight ranges. Results show that higher molecular weight collagen peptides produce higher synthesis of collagen type I mRNA and, therefore, it may suggest that prior molecular weight selection may be an important step to maximize the effect of collagen hydrolysates on collagen type I synthesis by dermal fibroblasts. PMID:29701725

Degradation of porous poly(D,L-lactic-co-glycolic acid) films based on water diffusion.

PubMed

Huang, Ying-Ying; Qi, Min; Liu, Hong-Ze; Zhao, Hong; Yang, Da-Zhi

2007-03-15

Poly(D,L-lactic-co-glycolic acid) has been extensively used as a controlled release carrier for drug delivery due to its good biocompatibility, biodegradability, and mechanical strength. Effects of dense and porous film's degradation behavior have been systematically investigated up to 17 weeks in Hank's Simulated Body Fluid at 37 degrees C. The degradation of the films was studied by measuring changes in weight, molecular weight and its distribution, morphology, composition etc.. A special thing was that the differences in water diffusion in dense and porous structure films caused the different degradation behavior. According to the characteristic changes of various properties of films, the degradation process is suggested to be roughly divided into four stages, tentatively named as water absorption stage, dramatic loss of molecular weight or micro-pores formed stage, loss of weight or enlarged-pores formed stage, pores diminished or pores collapse stage.

MALDI-TOF mass spectrometry analysis of small molecular weight compounds (under 10 KDa) as biomarkers of rat hearts undergoing arecoline challenge.

PubMed

Chen, Tung-Sheng; Chang, Mu-Hsin; Kuo, Wei-Wen; Lin, Yueh-Min; Yeh, Yu-Lan; Day, Cecilia Hsuan; Lin, Chien-Chung; Tsai, Fuu-Jen; Tsai, Chang-Hai; Huang, Chih-Yang

2013-04-01

Statistical and clinical reports indicate that betel nut chewing is strongly associated with progression of oral cancer because some ingredients in betel nuts are potential cancer promoters, especially arecoline. Early diagnosis for cancer biomarkers is the best strategy for prevention of cancer progression. Several methods are suggested for investigating cancer biomarkers. Among these methods, gel-based proteomics approach is the most powerful and recommended tool for investigating biomarkers due to its high-throughput. However, this proteomics approach is not suitable for screening biomarkers with molecular weight under 10 KDa because of the characteristics of gel electrophoresis. This study investigated biomarkers with molecular weight under 10 KDa in rats with arecoline challenge. The centrifuging vials with membrane (10 KDa molecular weight cut-off) played a crucial role in this study. After centrifuging, the filtrate (containing compounds with molecular weight under 10 KDa) was collected and spotted on a sample plate for MALDI-TOF mass spectrometry analysis. Compared to control, three extra peaks (m/z values were 1553.1611, 1668.2097 and 1740.1832, respectively) were found in sera and two extra peaks were found in heart tissue samples (408.9719 and 524.9961, respectively). These small compounds should play important roles and may be potential biomarker candidates in rats with arecoline. This study successfully reports a mass-based method for investigating biomarker candidates with small molecular weight in different types of sample (including serum and tissue). In addition, this reported method is more time-efficient (1 working day) than gel-based proteomics approach (5~7 working days).

Cholesterol-lowering effect of kori-tofu protein and its high-molecular-weight fraction content.

PubMed

Ishiguro, Takahiro; Tatsunokuchi, Seiji; Mitsui, Nobuo; Kayahara, Hisataka; Murasawa, Hisashi; Konishi, Yotaro; Nagaoka, Satoshi

2011-01-01

The serum total cholesterol concentration was significantly lower in the kori-tofu feeding group than in the soy protein isolate (SPI) group, except on the 28th day of the experiment. The high-molecular-weight fraction (HMF) content of the kori-tofu protein was significantly higher than that of SPI. This difference in the HMF content may have influenced the cholesterol-lowering effect of the protein.

Experimental insights into the importance of aquatic bacterial community composition to the degradation of dissolved organic matter

PubMed Central

Logue, Jürg B; Stedmon, Colin A; Kellerman, Anne M; Nielsen, Nikoline J; Andersson, Anders F; Laudon, Hjalmar; Lindström, Eva S; Kritzberg, Emma S

2016-01-01

Bacteria play a central role in the cycling of carbon, yet our understanding of the relationship between the taxonomic composition and the degradation of dissolved organic matter (DOM) is still poor. In this experimental study, we were able to demonstrate a direct link between community composition and ecosystem functioning in that differently structured aquatic bacterial communities differed in their degradation of terrestrially derived DOM. Although the same amount of carbon was processed, both the temporal pattern of degradation and the compounds degraded differed among communities. We, moreover, uncovered that low-molecular-weight carbon was available to all communities for utilisation, whereas the ability to degrade carbon of greater molecular weight was a trait less widely distributed. Finally, whereas the degradation of either low- or high-molecular-weight carbon was not restricted to a single phylogenetic clade, our results illustrate that bacterial taxa of similar phylogenetic classification differed substantially in their association with the degradation of DOM compounds. Applying techniques that capture the diversity and complexity of both bacterial communities and DOM, our study provides new insight into how the structure of bacterial communities may affect processes of biogeochemical significance. PMID:26296065

Complex Forms of Soil Organic Phosphorus-A Major Component of Soil Phosphorus.

PubMed

McLaren, Timothy I; Smernik, Ronald J; McLaughlin, Mike J; McBeath, Therese M; Kirby, Jason K; Simpson, Richard J; Guppy, Christopher N; Doolette, Ashlea L; Richardson, Alan E

2015-11-17

Phosphorus (P) is an essential element for life, an innate constituent of soil organic matter, and a major anthropogenic input to terrestrial ecosystems. The supply of P to living organisms is strongly dependent on the dynamics of soil organic P. However, fluxes of P through soil organic matter remain unclear because only a minority (typically <30%) of soil organic P has been identified as recognizable biomolecules of low molecular weight (e.g., inositol hexakisphosphates). Here, we use (31)P nuclear magnetic resonance spectroscopy to determine the speciation of organic P in soil extracts fractionated into two molecular weight ranges. Speciation of organic P in the high molecular weight fraction (>10 kDa) was markedly different to that of the low molecular weight fraction (<10 kDa). The former was dominated by a broad peak, which is consistent with P bound by phosphomonoester linkages of supra-/macro-molecular structures, whereas the latter contained all of the sharp peaks that were present in unfractionated extracts, along with some broad signal. Overall, phosphomonoesters in supra-/macro-molecular structures were found to account for the majority (61% to 73%) of soil organic P across the five diverse soils. These soil phosphomonoesters will need to be integrated within current models of the inorganic-organic P cycle of soil-plant terrestrial ecosystems.

Molecular features determining different partitioning patterns of papain and bromelain in aqueous two-phase systems.

PubMed

Rocha, Maria Victoria; Nerli, Bibiana Beatriz

2013-10-01

The partitioning patterns of papain (PAP) and bromelain (BR), two well-known cysteine-proteases, in polyethyleneglycol/sodium citrate aqueous two-phase systems (ATPSs) were determined. Polyethyleneglycols of different molecular weight (600, 1000, 2000, 4600 and 8000) were assayed. Thermodynamic characterization of partitioning process, spectroscopy measurements and computational calculations of protein surface properties were also carried out in order to explain their differential partitioning behavior. PAP was observed to be displaced to the salt-enriched phase in all the assayed systems with partition coefficients (KpPAP) values between 0.2 and 0.9, while BR exhibited a high affinity for the polymer phase in systems formed by PEGs of low molecular weight (600 and 1000) with partition coefficients (KpBR) values close to 3. KpBR values resulted higher than KpPAP in all the cases. This difference could be assigned neither to the charge nor to the size of the partitioned biomolecules since PAP and BR possess similar molecular weight (23,000) and isoelectric point (9.60). The presence of highly exposed tryptophans and positively charged residues (Lys, Arg and His) in BR molecule would be responsible for a charge transfer interaction between PEG and the protein and, therefore, the uneven distribution of BR in these systems. Copyright © 2013 Elsevier B.V. All rights reserved.

Ultrasonic degradation of butadiene, styrene and their copolymers.

PubMed

Sathiskumar, P S; Madras, Giridhar

2012-05-01

Ultrasonic degradation of commercially important polymers, styrene-butadiene (SBR) rubber, acrylonitrile-butadiene (NBR) rubber, styrene-acrylonitrile (SAN), polybutadiene rubber and polystyrene were investigated. The molecular weight distributions were measured using gel permeation chromatography (GPC). A model based on continuous distribution kinetics approach was used to study the time evolution of molecular weight distribution for these polymers during degradation. The effect of solvent properties and ultrasound intensity on the degradation of SBR rubber was investigated using different pure solvents and mixed solvents of varying volatility and different ultrasonic intensities. Copyright © 2011 Elsevier B.V. All rights reserved.

Czochralski growth of NaNO3-LiNO3 solid solution single crystals using axial vibrational control technique

NASA Astrophysics Data System (ADS)

Avetissov, Igor; Sadovskiy, Andrei; Belov, Stanislav; Kong Khan, Chan; Mozhevitina, Elena; Sukhanova, Ekaterina; Zharikov, Eugeniy

2014-09-01

T-x diagram of LiNO3-NaNO3 quasi-binary system has been improved using an original technique based on Raman measurements of condense phase. (LiNO3)x(NaNO3)1-x solid solution single crystal has been grown at different regimes of axial vibrational control (AVC) technique. Significant difference in segregation coefficient behavior between AVC-CZ and conventional CZ grown crystals has appeared: with AVC intensity increase the segregation coefficient (SC) raises for light molecular weight elements, SC reduces for medium molecular weight elements, and SC remains practically unchangeable for heavy molecular weight elements. Effect of vibrational intensity on vibron and optical characteristics, microhardness of AVC-CZ (LiNO3)x(NaNO3)1-x solid solution single crystals has been studied. For the AVC-CZ crystals has been observed increases in microhardness as well as in optical transmission up to 10 rel% compare to conventional CZ grown crystals.

Transformation of molecular weight distributions of dissolved organic carbon and UV-absorbing compounds at full-scale wastewater-treatment plants.

PubMed

Esparza-Soto, Mario; Fox, Peter; Westerhoff, Paul

2006-03-01

The molecular-weight distribution (MWD) of wastewater dissolved-organic carbon (DOC) was determined in samples from seven full-scale wastewater-treatment plants (WWTPs) that use different biological treatments (air activated sludge [air-AS], pure-oxygen AS [O2-AS], and trickling filters). The research objective was to determine how different biological treatments influenced the MWD of wastewater DOC. Primary sedimentation effluent DOC from most of the WWTPs exhibited a skewed distribution toward the low-molecular-weight fraction (MWF) (40 to 50%, < 0.5 K Daltons [KDa]). The Air-AS effluent DOC exhibited a centrally clustered distribution, with the majority of DOC in the intermediate MWF (0.5 to 3 KDa). The O2-AS effluent DOC exhibited a skewed distribution toward the high MWF (> 3 KDa). The removal of DOC by air- and O2-AS bacteria followed trends predicted by a macromolecule degradation model. Trickling-filter effluent DOC exhibited a skewed distribution toward the high MWF (50% DOC, > 3 KDa).

Surface temperatures and glassy state investigations in tribology

NASA Technical Reports Server (NTRS)

Bair, S.; Winer, W. O.

1980-01-01

Measurements were made of the limiting shear stress for two naphthenic oils of differing molecular weight and three blends of the lower molecular weight oil and polymers of differing molecular weight. All reached the same limiting shear stress for the same temperature and pressure; although the polymer solutions reduced the limiting shear stress by about fifteen percent. A falling body viscometer was constructed to operate to 230 C and to 0.6 GPa and another was constructed to extend the pressure range to 1.1 GPa. A concentrated contact simulator was developed which allows recording of the traction force while the slide-roll ratio is continuously varied and the rolling speed is maintained essentially constant. Measurement of lubricant minimum film thickness of elliptical EHD contacts of various aspect ratios were made by optical interferometry. The experimental data were thirty percent greater than that predicted by the Hamrock and Dowson model. Preliminary development of the application of a scanning infrared radiation system to a tribological system was completed.

Cytotoxicity associated with electrospun polyvinyl alcohol.

PubMed

Pathan, Saif G; Fitzgerald, Lisa M; Ali, Syed M; Damrauer, Scott M; Bide, Martin J; Nelson, David W; Ferran, Christiane; Phaneuf, Tina M; Phaneuf, Matthew D

2015-11-01

Polyvinyl alcohol (PVA) is a synthetic, water-soluble polymer, with applications in industries ranging from textiles to biomedical devices. Research on electrospinning of PVA has been targeted toward optimizing or finding novel applications in the biomedical field. However, the effects of electrospinning on PVA biocompatibility have not been thoroughly evaluated. In this study, the cytotoxicity of electrospun PVA (nPVA) which was not crosslinked after electrospinning was assessed. PVA polymers of several molecular weights were dissolved in distilled water and electrospun using the same parameters. Electrospun PVA materials with varying molecular weights were then dissolved in tissue culture medium and directly compared against solutions of nonelectrospun PVA polymer in human coronary artery smooth muscle cells and human coronary artery endothelial cells cultures. All nPVA solutions were cytotoxic at a threshold molar concentration that correlated with the molecular weight of the starting PVA polymer. In contrast, none of the nonelectrospun PVA solutions caused any cytotoxicity, regardless of their concentration in the cell culture. Evaluation of the nPVA material by differential scanning calorimetry confirmed that polymer degradation had occurred after electrospinning. To elucidate the identity of the nPVA component that caused cytotoxicity, nPVA materials were dissolved, fractionated using size exclusion columns, and the different fractions were added to HCASMC and human coronary artery endothelial cells cultures. These studies indicated that the cytotoxic component of the different nPVA solutions were present in the low-molecular-weight fraction. Additionally, the amount of PVA present in the 3-10 kg/mol fraction was approximately sixfold greater than that in the nonelectrospun samples. In conclusion, electrospinning of PVA resulted in small-molecular-weight fractions that were cytotoxic to cells. This result demonstrates that biocompatibility of electrospun biodegradable polymers should not be assumed on the basis of success of their nonelectrospun predecessors. © 2015 Wiley Periodicals, Inc.

Structural properties of pyruvate carboxylases from chicken liver and other sources

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

Barden, R.E.; Taylor, B.L.; Isohashi, F.

1975-11-01

Varieties of pyruvate carboxylase (pyruvate: CO/sub 2/ ligase (ADP-forming), EC 6.4.1.1) obtained from the livers of several species of vertebrates, including humans, all show the same basic structure. They are composed of large polypeptide chains of molecular weights ranging from 1.2 to 1.3 x 10/sup 5/ for the different varieties of the enzyme. The native form of the enzyme appears to be a tetramer with a molecular weight of about 5 x 10/sup 5/. In the case of pyruvate carboxylase from chicken liver each polypeptide chain contains a biotin moiety, thus supporting the thesis that the tetramer contains four identicalmore » polypeptide chains. Pyruvate carboxylase from yeast appears to be basically similar to those from the vertebrate species and has a tetrameric structure. Each protomer contains a single polypeptide chain with a molecular weight of 1.25 x 10/sup 5/. In contrast, pyruvate carboxylase from two bacterial species, Pseudomonas citronellolis and Azotobacter vinelandii, appears to be a dimer with a molecular weight (2.5 x 10/sup 5/) about half that of the animal and yeast species. As a further difference, each of the protomers of the bacterial enzymes contain two polypeptides of 6.5 and 5.4 x 10/sup 5/ molecular weight in the case of the Pseudomonas enzyme. The larger of the two polypeptides contains the biotin moiety. The functional units of the bacterial enzyme thus appear to contain two polypeptides while that of the liver and yeast enzymes is made up of a single chain. Neither of these arrangements corresponds with those of other biotin enzymes whose structure has been extensively studied (acetyl-CoA carboxylases from liver or Escherichia coli, and transcarboxylase from Propionibacterium). (auth)« less

Modification of linear prepolymers to tailor heterogeneous network formation through photo-initiated Polymerization-Induced Phase Separation

PubMed Central

Szczepanski, Caroline R.; Stansbury, Jeffrey W.

2015-01-01

Polymerization-induced phase separation (PIPS) was studied in ambient photopolymerizations of triethylene glycol dimethacrylate (TEGDMA) modified by poly(methyl methacrylate) (PMMA). The molecular weight of PMMA and the rate of network formation (through incident UV-irradiation) were varied to influence both the promotion of phase separation through increases in overall free energy, as well as the extent to which phase development occurs during polymerization through diffusion prior to network gelation. The overall free energy of the polymerizing system increases with PMMA molecular weight, such that PIPS is promoted thermodynamically at low loading levels (5 wt%) of a higher molecular weight PMMA (120 kDa), while a higher loading level (20 wt%) is needed to induce PIPS with lower PMMA molecular weight (11 kDa), and phase separation was not promoted at any loading level tested of the lowest molecular weight PMMA (1 kDa). Due to these differences in overall free energy, systems modified by PMMA (11 kDa) underwent phase separation via Nucleation and Growth, and systems modified by PMMA (120 kDa), followed the Spinodal Decomposition mechanism. Despite differences in phase structure, all materials form a continuous phase rich in TEGDMA homopolymer. At high irradiation intensity (Io=20mW/cm2), the rate of network formation prohibited significant phase separation, even when thermodynamically preferred. A staged curing approach, which utilizes low intensity irradiation (Io=300µW/cm2) for the first ~50% of reaction to allow phase separation via diffusion, followed by a high intensity flood-cure to achieve a high degree of conversion, was employed to form phase-separated networks with reduced polymerization stress yet equivalent final conversion and modulus. PMID:26190865

Ultrahigh molecular weight aromatic siloxane polymers

NASA Technical Reports Server (NTRS)

Ludwick, L. M.

1982-01-01

The condensation of a diol with a silane in toluene yields a silphenylene-siloxane polymer. The reaction of stiochiometric amounts of the diol and silane produced products with molecular weights in the range 2.0 - 6.0 x 10 to the 5th power. The molecular weight of the product was greatly increased by a multistep technique. The methodology for synthesis of high molecular weight polymers using a two step procedure was refined. Polymers with weight average molecular weights in excess of 1.0 x 10 to the 6th power produced by this method. Two more reactive silanes, bis(pyrrolidinyl)dimethylsilane and bis(gamma butyrolactam)dimethylsilane, are compared with the dimethyleminodimethylsilane in ability to advance the molecular weight of the prepolymer. The polymers produced are characterized by intrinsic viscosity in tetrahydrofuran. Weight and number average molecular weights and polydispersity are determined by gel permeation chromatography.

Effect of molecular weight of polyethylene glycol on the rheological properties of fumed silica-polyethylene glycol shear thickening fluid

NASA Astrophysics Data System (ADS)

Singh, Mansi; Verma, Sanjeev K.; Biswas, Ipsita; Mehta, Rajeev

2018-05-01

The steady-shear viscosity and dynamic visco-elastic behavior of suspensions of 20 wt% fumed silica-polyethylene glycol (PEG200) shear thickening fluid (STF) with different concentrations of various molecular weight PEG (4600, 6000 and 10000) has been studied. The results demonstrate that with an increase in the molecular weight of dispersing medium, the shear thickening parameters are significantly enhanced. In steady-state rheology, addition of PEG6000 as an additive results in high shear thickening at both low and high temperatures whereas in dynamic state, PEG4600 gives high values of all dynamic parameters. Additionally, long polymer can interconnect several particles, acting as cross-links which explain the mechanism of the enhancement in viscosity. Interestingly, compositions having PEG10000 as additive exhibits shear thinning rheology. Long polymer chains increases hydrodynamic forces thus aggregation of particles increases. Also, the results demonstrate the effect of high molecular weight PEGs on the elasticity and stability of the STF, which is important with regard to high impact resisting applications.

Insights in groundwater organic matter from Liquid Chromatography-Organic Carbon Detection

NASA Astrophysics Data System (ADS)

Rutlidge, H.; Oudone, P.; McDonough, L.; Andersen, M. S.; Baker, A.; Meredith, K.; O'Carroll, D. M.

2017-12-01

Understanding the processes that control the concentration and characteristics of organic matter in groundwater has important implications for the terrestrial global carbon budget. Liquid Chromatography - Organic Carbon Detection (LC-OCD) is a size-exclusion based chromatography technique that separates the organic carbon into molecular weight size fractions of biopolymers, humic substances, building blocks (degradation products of humic substances), low molecular weight acids and low molecular weight neutrals. Groundwater and surface water samples were collected from a range of locations in Australia representing different surface soil, land cover, recharge type and hydrological properties. At one site hyporheic zone samples were also collected from beneath a stream. The results showed a general decrease in the aromaticity and molecular weight indices going from surface water, hyporheic downwelling and groundwater samples. The aquifer substrate also affected the organic composition. For example, groundwater samples collected from a zone of fractured rock showed a relative decrease in the proportion of humic substances, suggestive of sorption or degradation of humic substances. This work demonstrates the potential for using LC-OCD in elucidating the processes that control the concentration and characteristics of organic matter in groundwater.

The Influence of Sintering Method on Kaolin-Based Geopolymer Ceramics with Addition of Ultra High Molecular Weight Polyethylene as Binder

NASA Astrophysics Data System (ADS)

Romisuhani, A.; AlBakri, M. M.; Kamarudin, H.; Andrei, S. V.

2017-11-01

The influence of sintering method on kaolin-based geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene as binder were studied. Geopolymer were formed at room temperature from kaolin and sodium silicate in a highly alkaline medium, followed by curing and drying at 80 °C. 12 M of sodium hydroxide solution were mixed with sodium silicate at a ratio of 0.24 to form alkaline activator. Powder metallurgy technique were used in order to produce kaolin geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene. The samples were heated at temperature of 1200 °C with two different sintering method which are conventional method and two-step sintering method. The strength and density were tested.

Pervaporative dehydration characteristics of an ethanol/water azeotrope through various chitosan membranes.

PubMed

Uragami, Tadashi; Saito, Tomoyuki; Miyata, Takashi

2015-04-20

The permeation and separation characteristics of an ethanol/water azeotrope through chitosan membranes of different molecular weights and degrees of deacetylation during pervaporation were investigated. The normalized permeation rate decreased with increasing molecular weight up to 90 kDa, but at over 90 kDa, the rate increased. On the other hand, the water/ethanol selectivity increased with increasing molecular weight up to 90 kDa but decreased at over 90 kDa. With increasing degree of deacetylation, the water/ethanol permselectivity increased significantly, but the normalized permeation rate decreased. The characteristics of chitosan membranes are discussed based on their chemical and physical structures such as the contact angle, density, degree of swelling, and glass transition temperature. Copyright © 2014 Elsevier Ltd. All rights reserved.

Divalent cation interactions with oligogalacturonides.

PubMed

Cescutti, P; Rizzo, R

2001-07-01

The conformational properties of high and low molecular weight galacturonides were investigated in relation to the ability of oligomers with degree of polymerization >10 to act as elicitors of plant defense mechanisms. Oligomers from polygalacturonate were obtained by means of enzymatic hydrolysis. Two fractions exhibiting high and low average degrees of polymerization were isolated by solvent fractionation and characterized by means of electrospray mass spectrometry. The conformational behaviors of the two fractions were investigated in the presence of different divalent cations using circular dichroism. Calcium, copper, and zinc ions were able to induce a conformational transition in both fractions. When in the presence of the high molecular weight fraction, copper and zinc ions were much more effective than calcium ions, whereas the efficiency was much reduced with low molecular weight oligomers.

Glass transition behavior of polystyrene/silica nanocomposites.

NASA Astrophysics Data System (ADS)

Xie, Yuping; Sen, Sudeepto; Kumar, Sanat; Bansal, Amitabh

2006-03-01

The change in thermomechanical properties of nano-filled polymers is of considerable scientific and technological interest. The interaction between the nanofillers and the matrix polymer controls the nanocomposite properties. We will present the results from recent and ongoing DSC experiments on polystyrene/silica nanocomposites. Polystyrene of different molecular weights (and from different sources) and silica nanoparticles 10-15 nm in diameter (both as received from Nissan and surface modified by grafted or physisorbed polystyrene) are being used to process the nanocomposites. We are studying trends in the glass transition behavior by changing the matrix molecular weights and the silica weight fractions. Recent data indicate that the glass transition temperature can both decrease and increase depending on the polymer-nanofiller combination as well as the thermal treatment of the nanocomposites prior to the DSC runs.

Molecular weight (hydrodynamic volume) dictates the systemic pharmacokinetics and tumour disposition of PolyPEG star polymers.

PubMed

Khor, Song Yang; Hu, Jinming; McLeod, Victoria M; Quinn, John F; Williamson, Mark; Porter, Christopher J H; Whittaker, Michael R; Kaminskas, Lisa M; Davis, Thomas P

2015-11-01

Herein we report for the first time the biological fate of poly[(oligoethylene glycol) acrylate] (POEGA) star polymers synthesised via a versatile arm-first reversible addition-fragmentation chain transfer (RAFT) polymerisation approach. The biopharmaceutical behaviour of three different molecular weight (49, 64 and 94kDa) POEGA stars was evaluated in rats and nude mice bearing human MDA MB-231 tumours after intravenous administration. The 94kDa star polymer exhibited a longer plasma exposure time than the 49kDa or 64kDa star polymer; an observation attributable to differences in the rates of both polymer biodegradation and urinary excretion. Tumour biodistribution also correlated with molecular weight and was greatest for the longest circulating 94kDa star. Different patterns of liver and spleen biodistribution were observed between mice and rats for the different sized polymers. The polymers were also well-tolerated in vivo and in vitro at therapeutic concentrations. Advances in nanotechnology has enabled scientists to produce nanoparticle as drug carriers in cancer therapeutics. In this article, the authors studied the biological fate of poly[(oligoethylene glycol) acrylate] (POEGA) star polymers of different size, after intravenous injections. This would allow the subsequent comparison to other drug delivery systems for better drug delivery. Copyright © 2015 Elsevier Inc. All rights reserved.

Conversion of calibration curves for accurate estimation of molecular weight averages and distributions of polyether polyols by conventional size exclusion chromatography.

PubMed

Xu, Xiuqing; Yang, Xiuhan; Martin, Steven J; Mes, Edwin; Chen, Junlan; Meunier, David M

2018-08-17

Accurate measurement of molecular weight averages (M¯ n, M¯ w, M¯ z ) and molecular weight distributions (MWD) of polyether polyols by conventional SEC (size exclusion chromatography) is not as straightforward as it would appear. Conventional calibration with polystyrene (PS) standards can only provide PS apparent molecular weights which do not provide accurate estimates of polyol molecular weights. Using polyethylene oxide/polyethylene glycol (PEO/PEG) for molecular weight calibration could improve the accuracy, but the retention behavior of PEO/PEG is not stable in THF-based (tetrahydrofuran) SEC systems. In this work, two approaches for calibration curve conversion with narrow PS and polyol molecular weight standards were developed. Equations to convert PS-apparent molecular weight to polyol-apparent molecular weight were developed using both a rigorous mathematical analysis and graphical plot regression method. The conversion equations obtained by the two approaches were in good agreement. Factors influencing the conversion equation were investigated. It was concluded that the separation conditions such as column batch and operating temperature did not have significant impact on the conversion coefficients and a universal conversion equation could be obtained. With this conversion equation, more accurate estimates of molecular weight averages and MWDs for polyether polyols can be achieved from conventional PS-THF SEC calibration. Moreover, no additional experimentation is required to convert historical PS equivalent data to reasonably accurate molecular weight results. Copyright © 2018. Published by Elsevier B.V.

Molecular weight of Escherichia coli β-galactosidase in concentrated solutions of guanidine hydrochloride

PubMed Central

Erickson, Robert P.

1970-01-01

The molecular weight of Escherichia coli β-galactosidase was determined in 6m- and 8m-guanidine hydrochloride by meniscus-depletion sedimentation equilibrium, sedimentation velocity and viscosity. Sedimentation equilibrium revealed heterogeneity with the smallest component having a molecular weight of about 50000. At lower speeds, the apparent weight-average molecular weight is about 80000. By use of a calculation based on an empirical correlation for proteins that are random coils in 6m-guanidine hydrochloride, sedimentation velocity gave a molecular weight of 91000, and the intrinsic viscosity indicated a viscosity-average molecular weight of 84000. Heating in 6m-guanidine hydrochloride lowered the viscosity of β-galactosidase in a variable manner. PMID:4924171

Carcinoma-specific Ulex europaeus agglutinin-I binding glycoproteins of human colorectal carcinoma and its relation to carcinoembryonic antigen.

PubMed

Matsushita, Y; Yonezawa, S; Nakamura, T; Shimizu, S; Ozawa, M; Muramatsu, T; Sato, E

1985-08-01

Glycoproteins binding to Ulex europaeus agglutinin-I (UEA-I) lectin, which recognizes the terminal alpha-L-fucose residue, were analyzed in 18 cases of human colorectal carcinoma by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by the Western blotting method. In the distal large bowel (descending and sigmoid colon and rectum), high-molecular-weight glycoproteins binding to UEA-I existed in carcinoma tissue but not in normal mucosa. In the proximal large bowel (ascending and transverse colon), high-molecular-weight glycoproteins binding to UEA-I were found both in normal mucosa and in carcinoma tissue, whereas those from the carcinoma tissue had an apparently lower molecular weight as compared to the weight of those from the normal mucosa. Thus there is a biochemical difference in UEA-I binding glycoproteins between the normal mucosa and the carcinoma tissue, although in our previous histochemical study no difference was observed in UEA-I binding glycoproteins of the proximal large bowel between the carcinoma tissue and the normal mucosa. Furthermore, carcinoembryonic antigen from the carcinoma tissue was found to have the same electrophoretical mobility as the UEA-I binding glycoproteins.

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.

Study on the technology of dual-tube layered injection in ASP flooding

NASA Astrophysics Data System (ADS)

Yang, Ye; Zhang, Yongping; Xu, Dekui; Cai, Meng; Yang, Zhigang; Wang, Hailong; Song, Xingliang

2017-10-01

For the single-tube layered injection technology cannot solve the problem of interlayer pressure difference is greater than 2MPa injection wells, through the development of dual-tube packer, dual-tube injection allocator, downhole plug, the ground pressure regulator and molecular weight regulator. Dual-tube layered injection technology is formed. According to the data of ASP flooding injection wells in the field, the whole well is divided into high permeability and low permeability oil reservoir. Two separate injection channels can be formed by using dual-tube packer and dual-tube injection allocator. Through the use of the ground pressure regulator, the problem of the high permeability layer and low permeability layer of the injection pressure difference is solved. Through the use of the ground molecular weight regulator, the problem that the same molecular weight ASP solution is not suitable for high and low permeability is solved. By replacing the downhole plug, the grouping transformation of some oil layer can be achieved. The experiment and field application of 3 wells results show that: the flow control range is 20m3/d-70m3/d; the max. Throttling differential pressure is 3.5MPa; the viscosity loss rate of solution is less than 5%; and the molecular weight adjusting range is 20%-50%. The utilization degree of oil layer is obviously increased through the use of the dual-tube layered injection technology.

Distribution of molecular weight in glyceride polymerizates or aggregates of them after contact with lunar grains

NASA Technical Reports Server (NTRS)

Asunmaa, S. K.; Haack, R.

1977-01-01

An attempt is made to report on experiments in which a molecular-weight increase was determined in thin layers of triglyceride-containing glycerides after thin-layer contact for two years with lunar topsoil grains at 25 C without any thermal activation. It is noted that solidification was observed on both dielectric grains and metal-rich areas and that changes in viscosity and molecular weights were first detected by solidification of surface layers. Gel permeation chromatography is described which detected a general shift of the Gaussian distribution of the molecular-weight data toward generally higher molecular weights as well as an increase in mean molecular weight. Reaction mechanisms are considered, and results of spectrographic analysis are cited which support the interpretations of the molecular-weight data.

Bacterial alginate production: an overview of its biosynthesis and potential industrial production.

PubMed

Urtuvia, Viviana; Maturana, Nataly; Acevedo, Fernando; Peña, Carlos; Díaz-Barrera, Alvaro

2017-10-07

Alginate is a linear polysaccharide that can be used for different applications in the food and pharmaceutical industries. These polysaccharides have a chemical structure composed of subunits of (1-4)-β-D-mannuronic acid (M) and its C-5 epimer α-L-guluronic acid (G). The monomer composition and molecular weight of alginates are known to have effects on their properties. Currently, these polysaccharides are commercially extracted from seaweed but can also be produced by Azotobacter vinelandii and Pseudomonas spp. as an extracellular polymer. One strategy to produce alginates with different molecular weights and with reproducible physicochemical characteristics is through the manipulation of the culture conditions during fermentation. This mini-review provides a comparative analysis of the metabolic pathways and molecular mechanisms involved in alginate polymerization from A. vinelandii and Pseudomonas spp. Different fermentation strategies used to produce alginates at a bioreactor laboratory scale are described.

Molecular weight dependent charge carrier mobility in poly(3,3' '-dioctyl-2,2':5',2' '-terthiophene).

PubMed

Verilhac, Jean-Marie; Pokrop, Rafal; LeBlevennec, Gilles; Kulszewicz-Bajer, Irena; Buga, Katarzyna; Zagorska, Malgorzata; Sadki, Said; Pron, Adam

2006-07-13

Poly(3,3' '-dioctyl-2,2':5',2' '-terthiophene), a polymer recently used for the fabrication of organic field effect transistors, has been fractionated into five fractions distinctly differing in their molecular weights (Mn), with the goal of determining the influence of the degree of polymerization (DPn) on its principal physicochemical parameters. It has been demonstrated that within the Mn range studied (from 1.5 kDa to 10.5 kDa by SEC), corresponding to DPn from 10 to 38, the polymer band gap steadily decreases with growing molecular weight, which is clearly manifested by an increasing bathochromic shift of the band originating from the pi-pi* transition. The same trend is observed for the HOMO level, determined from the onset of the p-doping in cyclic voltammetry, which shifts from -5.10 eV to -4.90 eV for the lowest and the highest molecular weight fractions, respectively. The most pronounced influence of DPn has been found for the charge carriers' mobility-one of the most important parameters of field effect transistors (FETs) fabricated from this polymer. A fourfold increase in DPn results in an increase of the carriers' mobility by more than 3 orders of magnitude. Comparison of these results with those obtained for fractionated regioregular poly(3-hexylthiophene) shows a strikingly similar behavior of both polymers with respect to the molecular weight.

Porcine sclera as a model of human sclera for in vitro transport experiments: histology, SEM, and comparative permeability

PubMed Central

Ferrari, G.; Quarta, M.; Macaluso, C.; Govoni, P.; Dallatana, D.; Santi, P.

2009-01-01

Purpose To evaluate porcine sclera as a model of human sclera for in vitro studies of transscleral drug delivery of both low and high molecular weight compounds. Methods Human and porcine scleras were characterized for thickness and water content. The tissue surface was examined by scanning electron microscopy (SEM), and the histology was studied with hematoxylin-eosin staining. Comparative permeation experiments were performed using three model molecules, acetaminophen as the model compound for small molecules; a linear dextran with a molecular weight of 120 kDa as the model compound for high molecular weight drugs; and insulin, which was chosen as the model protein. Permeation parameters such as flux, lag time, and permeability coefficient were determined and compared. Results Human and porcine scleras have a similar histology and collagen bundle organization. The water content is approx 70% for both tissues while a statistically significant difference was found for the thickness, porcine sclera being approximately twofold thicker than human sclera. Differences in thickness produced differences in the permeability coefficient. In fact, human sclera was found to be two to threefold more permeable toward the three molecules studied than porcine sclera. Conclusions The results obtained in the present paper prove that porcine sclera can be considered a good model for human sclera for in vitro permeation experiments of both low and high molecular weight compounds. In fact, if the different tissue thickness is taken into account, comparable permeability was demonstrated. This suggests a possible use of this model in the evaluation of the transscleral permeation of new biotech compounds, which currently represent the most innovative and efficient therapeutic options for the treatment of ocular diseases. PMID:19190734

Porcine sclera as a model of human sclera for in vitro transport experiments: histology, SEM, and comparative permeability.

PubMed

Nicoli, S; Ferrari, G; Quarta, M; Macaluso, C; Govoni, P; Dallatana, D; Santi, P

2009-01-01

To evaluate porcine sclera as a model of human sclera for in vitro studies of transscleral drug delivery of both low and high molecular weight compounds. Human and porcine scleras were characterized for thickness and water content. The tissue surface was examined by scanning electron microscopy (SEM), and the histology was studied with hematoxylin-eosin staining. Comparative permeation experiments were performed using three model molecules, acetaminophen as the model compound for small molecules; a linear dextran with a molecular weight of 120 kDa as the model compound for high molecular weight drugs; and insulin, which was chosen as the model protein. Permeation parameters such as flux, lag time, and permeability coefficient were determined and compared. Human and porcine scleras have a similar histology and collagen bundle organization. The water content is approx 70% for both tissues while a statistically significant difference was found for the thickness, porcine sclera being approximately twofold thicker than human sclera. Differences in thickness produced differences in the permeability coefficient. In fact, human sclera was found to be two to threefold more permeable toward the three molecules studied than porcine sclera. The results obtained in the present paper prove that porcine sclera can be considered a good model for human sclera for in vitro permeation experiments of both low and high molecular weight compounds. In fact, if the different tissue thickness is taken into account, comparable permeability was demonstrated. This suggests a possible use of this model in the evaluation of the transscleral permeation of new biotech compounds, which currently represent the most innovative and efficient therapeutic options for the treatment of ocular diseases.

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

Poly(glycidyl ether)-Based Monolayers on Gold Surfaces: Control of Grafting Density and Chain Conformation by Grafting Procedure, Surface Anchor, and Molecular Weight.

PubMed

Heinen, Silke; Weinhart, Marie

2017-03-07

For a meaningful correlation of surface coatings with their respective biological response reproducible coating procedures, well-defined surface coatings, and thorough surface characterization with respect to layer thickness and grafting density are indispensable. The same applies to polymeric monolayer coatings which are intended to be used for, e.g., fundamental studies on the volume phase transition of surface end-tethered thermoresponsive polymer chains. Planar gold surfaces are frequently used as model substrates, since they allow a variety of straightforward surface characterization methods. Herein we present reproducible grafting-to procedures performed with thermoresponsive poly(glycidyl ether) copolymers composed of glycidyl methyl ether (GME) and ethyl glycidyl ether (EGE). The copolymers feature different molecular weights (2 kDa, 9 kDa, 24 kDa) and are equipped with varying sulfur-containing anchor groups in order to achieve adjustable grafting densities on gold surfaces and hence control the tethered polymers' chain conformation. We determined "wet" and "dry" thicknesses of these coatings by QCM-D and ellipsometry measurements and deduced anchor distances and degrees of chain overlap of the polymer chains assembled on gold. Grafting under cloud point conditions allowed for higher degrees of chain overlap compared to grafting from a good solvent like ethanol, independent of the used sulfur-containing anchor group for polymers with low (2 kDa) and medium (9 kDa) molecular weights. By contrast, the achieved grafting densities and thus chain overlaps of surface-tethered polymers with high (24 kDa) molecular weights were identical for both grafting methods. Monolayers prepared from an ethanolic solution of poly(glycidyl ether)s equipped with sterically demanding disulfide-containing anchors revealed the lowest degrees of chain overlap. The ratio of the radius of gyration to the anchor distance (2 R g /l) of the latter coating was found to be lower than 1.4, indicating that the assembly was rather in the mushroom-like than in the brush regime. Polymer chains with thiol-containing anchors of different alkyl chain lengths (C 11 SH vs C 4 SH) formed assemblies with comparable degrees of chain overlap with 2 R g /l values above 1.4 and are thus in the brush regime. Molecular weights influenced the achievable degree of chain overlap on the surface. Coatings prepared with the medium molecular weight polymer (9 kDa) resulted in the highest chain packing density. Control of grafting density and thus chain overlap in different regimes (brush vs mushroom) on planar gold substrates are attainable for monolayer coatings with poly(GME-ran-EGE) by adjusting the polymer's molecular weight and anchor group as well as the conditions for the grafting-to procedure.

Molecular weight of different angiotensin II polymers directly determines: density of endothelial membrane AT1 receptors and coronary vasoconstriction.

PubMed

Torres-Tirado, David; Ramiro-Diaz, Juan; Knabb, Maureen T; Rubio, Rafael

2013-01-01

We have shown that angiotensin II (Ang II) does not diffuse across the vessel wall, remaining intravascularly confined and acting solely on the coronary endothelial luminal membrane (CELM) receptors. A sustained intracoronary infusion of Ang II causes transient coronary vasoconstriction (desensitization) due to membrane internalization of CELM Ang II type 1 receptors (CELM-AT1R). In contrast, sustained intracoronary infusion of a non-diffusible polymer of Ang II (Ang II-Pol, 15,000 kDa) causes a sustained vasoconstriction by preventing CELM-AT1R internalization. In addition, a sustained intracoronary infusion of Ang II leads to a depressed response following a secondary Ang II administration (tachyphylaxis) that is reversed by Ang II-Pol. These findings led us to hypothesize that the rate of desensitization, tachyphylaxis, and AT1R internalization were dependent on Ang II-Pol molecular weight. To test this hypothesis, we synthesized Ang II-Pols of the following molecular weights (in kDa): 1.3, 2.7, 11, 47, 527, 3270 and 15,000. Vasoconstriction was measured following intracoronary infusion of Ang II-Pols in Langendorff-perfused guinea pig hearts at constant flow. The CELM protein fraction was extracted using the silica pellicle technique at different time points in order to determine the rate of AT1R internalization following each Ang II-Pol infusion. CELM-AT1R density was quantified by Western blot. We found that the rate of desensitization and the tachyphylaxis effect varied inversely with the molecular weight of the Ang II-Pols. Inversely proportional to the molecular weight of Ang II-Pol the CELM-AT1R density decreases over time. These results indicate that the mechanism responsible for the decreased rate of desensitization and tachyphylaxis by higher molecular weight Ang II polymers is due to reduction in the rate of CELM-AT1R internalization. These Ang II polymers would be valuable tools for studying the relationship between AT1R internalization and physiological effects. Copyright © 2013 Elsevier Inc. All rights reserved.

Evaluation of Isolated Fractions of Aloe vera Gel Materials on Indinavir Pharmacokinetics: In vitro and in vivo Studies.

PubMed

Wallis, Lonette; Malan, Maides; Gouws, Chrisna; Steyn, Dewald; Ellis, Suria; Abay, Efrem; Wiesner, Lubbe; Otto, Daniel P; Hamman, Josias

2016-01-01

Aloe vera is a plant with a long history of traditional medicinal use and is consumed in different products, sometimes in conjunction with prescribed medicines. A. vera gel has shown the ability to modulate drug absorption in vitro. The aim of this study was to fractionate the precipitated polysaccharide component of A. vera gel based on molecular weight and to compare their interactions with indinavir pharmacokinetics. Crude polysaccharides were precipitated from a solution of A. vera gel and was fractionated by means of centrifugal filtration through membranes with different molecular weight cut-off values (i.e. 300 KDa, 100 KDa and 30 KDa). Marker molecules were quantified in the aloe leaf materials by means of nuclear magnetic resonance spectroscopy and the average molecular weight was determined by means of gel filtration chromatography linked to multi-angle-laser-light scattering and refractive index detection. The effect of the aloe leaf materials on the transepithelial electrical resistance (TEER) of Caco-2 cell monolayers as well as indinavir metabolism in LS180 cells was measured. The bioavailability of indinavir in the presence and absence of the aloe leaf materials was determined in Sprague-Dawley rats. All the aloe leaf materials investigated in this study reduced the TEER of Caco-2 cell monolayers, inhibited indinavir metabolism in LS 180 cells to different extents and changed the bioavailability parameters of indinavir in rats compared to that of indinavir alone. These indinavir pharmacokinetic modulation effects were not dependent on the presence of aloverose and also not on the average molecular weight of the isolated fractions.

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…

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…

Characteristics of molecular weight distribution of dissolved organic matter in bromide-containing water and disinfection by-product formation properties during treatment processes.

PubMed

Zhang, Ying; Zhang, Ning; Zhao, Peng; Niu, Zhiguang

2018-03-01

The characteristics of dissolved organic matter (DOM) and bromide ion concentration have a significant influence on the formation of disinfection by-products (DBPs). In order to identify the main DBP precursors, DOM was divided into five fractions based on molecular weight (MW), trihalomethane formation potential and haloacetic acid formation potential were determined for fractions, and the change in contents of different fractions and total DBPs during treatment processes (pre-chlorination, coagulation, sand filtration, disinfection) were studied. Moreover, the relationship between bromide concentration and DBP generation characteristics in processes was also analyzed. The results showed that the main DBP precursors were the fraction with MW <1kDa and fraction with MW 3-10kDa, and the DBP's generation ability of lower molecular weight DOM (<10kDa) was higher than that of higher molecular weight DOM. During different processes, pre-chlorination and disinfection had limited effect on removing organics but could alter the MW distribution, and coagulation and filtration could effectively remove organics with higher MW. For DBPs, trihalomethanes (THMs) were mainly generated in pre-chlorination and disinfection, while haloacetic acids (HAAs) were mostly generated during pre-chlorination; coagulation and sand filtration had little effect on THMs but resulted in a slight removal of HAAs. In addition, the results of ANOVA tests suggested that molecular sizes and treatment processes have significant influence on DBP formation. With increasing bromide concentration, the brominated DBPs significantly increased, but the bromine incorporation factor in the processes was basically consistent at each concentration. Copyright © 2017. Published by Elsevier B.V.

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.

Comparison of selected analytical techniques for protein sizing, quantitation and molecular weight determination.

PubMed

Goetz, H; Kuschel, M; Wulff, T; Sauber, C; Miller, C; Fisher, S; Woodward, C

2004-09-30

Protein analysis techniques are developing fast due to the growing number of proteins obtained by recombinant DNA techniques. In the present paper we compare selected techniques, which are used for protein sizing, quantitation and molecular weight determination: sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), lab-on-a-chip or microfluidics technology (LoaC), size exclusion chromatography (SEC) and mass spectrometry (MS). We compare advantages and limitations of each technique in respect to different application areas, analysis time, protein sizing and quantitation performance.

Oxidation of the N-terminal methionine of lens alpha-A crystallin

NASA Technical Reports Server (NTRS)

Takemoto, L.; Horwitz, J.; Emmons, T.; Spooner, B. S. (Principal Investigator)

1992-01-01

Antiserum against the N-terminal peptide of bovine alpha-A crystallin has been used to monitor purification of two different seropositive peptides (i.e. T1a and T1b) from a tryptic digest of bovine lens proteins. Both these peptides have similar amino acid compositions, but peptide T1b has a molecular weight 16 atomic mass units larger than T1a, suggesting posttranslational modification. Analysis of ionization fragments of the T1b peptide by mass spectrometry demonstrates that this difference in molecular weight is due to the in vivo oxidation of the N-terminal met residue of the alpha-A crystallin molecule.

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.

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.

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. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Catalytic ethanolysis of Kraft lignin into high-value small-molecular chemicals over a nanostructured α-molybdenum carbide catalyst.

PubMed

Ma, Rui; Hao, Wenyue; Ma, Xiaolei; Tian, Ye; Li, Yongdan

2014-07-07

We report the complete ethanolysis of Kraft lignin over an α-MoC1-x /AC catalyst in pure ethanol at 280 °C to give high-value chemicals of low molecular weight with a maximum overall yield of the 25 most abundant liquid products (LP25) of 1.64 g per gram of lignin. The LP25 products consisted of C6 -C10 esters, alcohols, arenes, phenols, and benzyl alcohols with an overall heating value of 36.5 MJ kg(-1) . C6 alcohols and C8 esters predominated and accounted for 82 wt % of the LP25 products. No oligomers or char were formed in the process. With our catalyst, ethanol is the only effective solvent for the reaction. Supercritical ethanol on its own degrades Kraft lignin into a mixture of small molecules and molecular fragments of intermediate size with molecular weights in the range 700-1400, differing in steps of 58 units, which is the weight of the branched-chain linkage C3 H6 O in lignin. Hydrogen was found to have a negative effect on the formation of the low-molecular-weight products. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Swelling and erosion properties of hydroxypropylmethylcellulose (Hypromellose) matrices--influence of agitation rate and dissolution medium composition.

PubMed

Kavanagh, Nicole; Corrigan, Owen I

2004-07-26

The effect of dissolution medium variables, such as medium composition, ionic strength and agitation rate, on the swelling and erosion of Hypromellose (hydroxypropylmethylcellulose, HPMC) matrices of different molecular weights was examined. Swelling and erosion of HPMC polymers was determined by measuring the wet and subsequent dry weights of matrices. It was possible to describe the rate of dissolution medium uptake in terms of a square root relationship and the erosion of the polymer in terms of the cube root law. The extent of swelling increased with increasing molecular weight, and decreased with increasing agitation rate. The erosion rate was seen to increase with decrease in polymer molecular weight, with a decrease in ionic strength and with increasing agitation rate. The sensitivity of polymer erosion to the degree of agitation may influence the ability of these polymers to give reproducible, agitation-independent release, compared to more rigid non-eroding matrix materials, in the complex hydrodynamic environment of the gastrointestinal tract.

Peptidylation for the determination of low-molecular-weight compounds by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

PubMed

Tang, Feng; Cen, Si-Ying; He, Huan; Liu, Yi; Yuan, Bi-Feng; Feng, Yu-Qi

2016-05-23

Determination of low-molecular-weight compounds by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has been a great challenge in the analytical research field. Here we developed a universal peptide-based derivatization (peptidylation) strategy for the sensitive analysis of low-molecular-weight compounds by MALDI-TOF-MS. Upon peptidylation, the molecular weights of target analytes increase, thus avoiding serious matrix ion interference in the low-molecular-weight region in MALDI-TOF-MS. Since peptides typically exhibit good signal response during MALDI-TOF-MS analysis, peptidylation endows high detection sensitivities of low-molecular-weight analytes. As a proof-of-concept, we analyzed low-molecular-weight compounds of aldehydes and thiols by the developed peptidylation strategy. Our results showed that aldehydes and thiols can be readily determined upon peptidylation, thus realizing the sensitive and efficient determination of low-molecular-weight compounds by MALDI-TOF-MS. Moreover, target analytes also can be unambiguously detected in biological samples using the peptidylation strategy. The established peptidylation strategy is a universal strategy and can be extended to the sensitive analysis of various low-molecular-weight compounds by MALDI-TOF-MS, which may be potentially used in areas such as metabolomics.

Isolation of a thermophilic bacterium capable of low-molecular-weight polyethylene degradation.

PubMed

Jeon, Hyun Jeong; Kim, Mal Nam

2013-02-01

A thermophilic bacterium capable of low-molecular-weight polyethylene (LMWPE) degradation was isolated from a compost sample, and was identified as Chelatococcus sp. E1, through sequencing of the 16S rRNA gene. LMWPE was prepared by thermal degradation of commercial PE in a strict nitrogen atmosphere. LMWPE with a weight-average-molecular-weight (Mw) in the range of 1,700-23,700 was noticeably mineralized into CO(2) by the bacterium. The biodegradability of LMWPE decreased as the Mw increased. The low molecular weight fraction of LMWPE decreased significantly as a result of the degradation process, and thereby both the number-average-molecular-weight and Mw increased after biodegradation. The polydispersity of LMWPE was either narrowed or widened, depending on the initial Mw of LMWPE, due to the preferential elimination of the low molecular weight fraction, in comparison to the high molecular weight portion. LMWPE free from an extremely low molecular weight fraction was also mineralized by the strain at a remarkable rate, and FTIR peaks assignable to C-O stretching appeared as a result of microbial action. The FTIR peaks corresponding to alkenes also became more intense, indicating that dehydrogenations occurred concomitantly with microbial induced oxidation.

Molecular weight dependence of LB morphology of poly(n-hexyl isocyanate) (PHIC).

PubMed

Morioka, Takako; Shibata, Osamu; Kawaguchi, Masami

2010-12-07

The morphologies of Langmuir-Blodgett (LB) films of two fractionated poly(n-hexyl isocyanate) (PHIC) and those of their binary mixtures were observed by AFM, together with those of an unfractionated PHIC. The low molecular weight PHIC formed random packing of bundles consisting of rigid rods, while the high molecular weight PHIC formed random packing of bundles consisting of hairy rods. Bundle interpenetration was observed only for the latter in the semidilute regime. In the bilayer region, the area occupied by the PHIC bundles in the upper layer was obviously smaller for the high molecular weight PHIC than for the low molecular weight PHIC, suggesting that the bundles of high molecular weight PHIC more easily interpenetrate than those of low molecular weight PHIC. For the blended films composed of both low and high molecular weight PHICs, the characteristic morphologies of the respective PHIC samples were no longer present. Moreover, the morphologies of the blended films appeared to resemble each other at any molar fraction owing to the ideal miscibility of the low molecular weight and high molecular weight PHICs. The morphologies of the blended films were also similar to that of the unfractionated PHIC film in the dilute regime. In the semidilute regime, the blended films became rounded owing to an increase in bundles interpenetration between PHICs as compared to that in the dilute regime, whereas the morphology of unfractionated PHIC films remained unchanged as compared to that in the dilute regime.

Microbial production of polyhydroxybutyrate with tailor-made properties: an integrated modelling approach and experimental validation.

PubMed

Penloglou, Giannis; Chatzidoukas, Christos; Kiparissides, Costas

2012-01-01

The microbial production of polyhydroxybutyrate (PHB) is a complex process in which the final quantity and quality of the PHB depend on a large number of process operating variables. Consequently, the design and optimal dynamic operation of a microbial process for the efficient production of PHB with tailor-made molecular properties is an extremely interesting problem. The present study investigates how key process operating variables (i.e., nutritional and aeration conditions) affect the biomass production rate and the PHB accumulation in the cells and its associated molecular weight distribution. A combined metabolic/polymerization/macroscopic modelling approach, relating the process performance and product quality with the process variables, was developed and validated using an extensive series of experiments and measurements. The model predicts the dynamic evolution of the biomass growth, the polymer accumulation, the consumption of carbon and nitrogen sources and the average molecular weights of the PHB in a bioreactor, under batch and fed-batch operating conditions. The proposed integrated model was used for the model-based optimization of the production of PHB with tailor-made molecular properties in Azohydromonas lata bacteria. The process optimization led to a high intracellular PHB accumulation (up to 95% g of PHB per g of DCW) and the production of different grades (i.e., different molecular weight distributions) of PHB. Copyright © 2011 Elsevier Inc. All rights reserved.

[Correlations between apparent diffusion coefficient in diffusion?weighted magnetic resonance imaging and molecular subtypes of invasive breast cancer masses].

PubMed

Shang, Liu-Tong; Yang, Jia-Fei; Lu, Jing; Wang, Ting-Ting; Zhou, Ying; Xing, Xin-Bo; Wang, Xin-Kun; Yang, Shu-Hui; Hu, Ming-Yan

2017-10-20

To study the correlation of apparent diffusion coefficient (ADC) measured by diffusion-weighted magnetic resonance imaging (MRI) with the molecular subtypes and biological prognostic factors of invasive breast cancer masses. Breast MRI data (including dynamic enhanced and diffusion-weighted imaging) were collected from 64 patients with pathologically confirmed invasive breast cancer masses (a total of 69 lesions). The mean ADC values of the lesions were calculated and their correlations were analyzed with the 5 molecular subtypes of invasive breast cancer and the biological prognostic factors including estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor 2 (HER2), and Ki-67 index. The ADC values did not differ significantly among the 5 molecular subtypes of invasive breast cancer masses (P>0.05) or among lesions with different ER, PR, or HER2 status (P>0.05). The mean ADC values were significantly higher in Ki-67-positive lesions than in the negative lesions (P=0.023 and negatively correlated with the expressions of Ki-67 (r=-0.249). ADC value can not be used to identify the molecular subtypes of invasive breast cancer masses or to evaluate the biological prognosis of the lesions, but its correlation with Ki-67 expression may help in prognostic evaluation and guiding clinical therapy of the tumors.

Natural attenuation and biosurfactant-stimulated bioremediation of estuarine sediments contaminated with diesel oil.

PubMed

Bayer, Débora M; Chagas-Spinelli, Alessandra C O; Gavazza, Sávia; Florencio, Lourdinha; Kato, Mario T

2013-09-01

We evaluated the bioremediation, by natural attenuation (NA) and by natural attenuation stimulated (SNA) using a rhamnolipid biosurfactant, of estuarine sediments contaminated with diesel oil. Sediment samples (30 cm) were put into 35 cm glass columns, and the concentrations of the 16 polycyclic aromatic hydrocarbons (PAHs) prioritized by the US Environmental Protection Agency were monitored for 111 days. Naphthalene percolated through the columns more than the other PAHs, and, in general, the concentrations of the lower molecular weight PAHs, consisting of two and three aromatic rings, changed during the first 45 days of treatment, whereas the concentrations of the higher molecular weight PAHs, consisting of four, five, and six rings, were more stable. The higher molecular weight PAHs became more available after 45 days, in the deeper parts of the columns (20-30 cm). Evidence of degradation was observed only for some compounds, such as pyrene, with a total removal efficiency of 82 and 78 % in the NA and SNA treatments, respectively, but without significant difference. In the case of total PAH removal, the efficiencies were significantly different of 82 and 67 %, respectively.

Low molecular weight fraction secreted by SKOV3 cells expands peripheral CD4+CD25+ regulatory T cells and enhances their suppressive capacity.

PubMed

Li, Xiao; Wan, Xiaoyun; Mao, Yuyan; Lu, Weiguo; Xie, Xing

2010-09-01

The increase of CD4+CD25+ regulatory T cells in patients with ovarian carcinoma has been verified. Here we investigated the effects of supernatant derived from ovarian carcinoma cell SKOV3 on peripheral regulatory T cells. Supernatant from SKOV3 was collected and fractionated into three different molecular weight fractions (MWFs). The proliferation of the CD4+CD25+ regulatory T cells cultured in complete RPMI 1640 medium with the different stimulators was detected. The phenotype (GITR and CTLA-4) of natural and expanded CD4+CD25+ T cells was detected by flow cytometry. Foxp3 mRNA expression of low MWF-expanded CD4+CD25+ T cells was detected by RT-PCR. Those expanded CD4+CD25+ regulatory T cells showed enhanced capacity to suppress CD4+CD25- T proliferation and increased expression of GITR and CTLA-4. In brief, low molecular weight fraction of supernatant secreted by SKOV3 could expand peripheral CD4+CD25+ regulatory T cells and enhance their suppressive function.

Changes of the Components of Fresh Seaweed, Undaria pinnatifida, by Different Strage Conditions

NASA Astrophysics Data System (ADS)

Onodera, Munenaka; Yoshie-Stark, Yumiko; Suzuki, Takesh

This study was performed to keep the quality and to prolong the shelf life of fresh Undaria pinnatifida, by different storage conditions. Changes of the contents of chlorophyll a (Chl a) and its derivatives, β-carotene, pH, molecular weight of alginate and molecular weight distribution were determined during the storage of U. pinnatifida. The conditions of cold storage at -3 to 7°C with air or O2, storage in seawater, and storage in slurry ice made of seawater were tested. Chl a and β-carotene contents, and the pH of U. pinnatifida were decreased following the increment of storage days. Significant decrease of Chl a content and molecular weight of U. pinnatifida was detected under cold storage especially at 7°C. The storage by icing in slurry ice and by super chilling at -3°C inhibited the degradation of Chl a and β-carotene of U. pinnatifida. The content of pheophorbide a or pH were recognized as useful factors to evaluate the quality and freshness of U. pinnatifida.

Customized Peptide Biomaterial Synthesis via an Environment-Reliant Auto-Programmer Stigmergic Approach

PubMed Central

Choonara, Yahya E.; du Toit, Lisa C.; Bijukumar, Divya; Chejara, Dharmesh R.

2018-01-01

Stigmergy, a form of self-organization, was employed here to engineer a self-organizing peptide capable of forming a nano- or micro-structure and that can potentially be used in various drug delivery and biomedical applications. These self-assembling peptides exhibit several desirable qualities for drug delivery, tissue engineering, cosmetics, antibiotics, food science, and biomedical surface engineering. In this study, peptide biomaterial synthesis was carried out using an environment-reliant auto-programmer stigmergic approach. A model protein, α-gliadin (31, 36, and 38 kD), was forced to attain a primary structure with free –SH groups and broken down enzymatically into smaller fragments using chymotrypsin. This breakdown was carried out at different environment conditions (37 and 50 °C), and the fragments were allowed to self-organize at these temperatures. The new peptides so formed diverged according to the environmental conditions. Interestingly, two peptides (with molecular weights of 13.8 and 11.8 kD) were isolated when the reaction temperature was maintained at 50 °C, while four peptides with molecular weights of 54, 51, 13.8, and 12.8 kD were obtained when the reaction was conducted at 37 °C. Thus, at a higher temperature (50 °C), the peptides formed, compared to the original protein, had lower molecular weights, whereas, at a lower temperature (37 °C), two peptides had higher molecular weights and two had lower molecular weights. PMID:29659507

The risk for cross-reactions after a cutaneous delayed-type hypersensitivity reaction to heparin preparations is independent of their molecular weight: a systematic review.

PubMed

Weberschock, Tobias; Meister, Anna Christina; Bohrt, Kevin; Schmitt, Jochen; Boehncke, Wolf-Henning; Ludwig, Ralf J

2011-10-01

Heparins are a widely used class of drugs known to cause delayed-type hypersensitivity (DTH) reactions. Recent publications indicate that the incidence of these may be higher than previously thought. To date, patient-related but no drug-related risk factors for the development of DTH reactions to heparins have been identified, although molecular weight is discussed as a potentially relevant parameter. To address this, a systematic review was conducted on the frequency of cross-reactions after DTH reactions to heparin preparations. We electronically searched MEDLINE and EMBASE, hand-searched selected journals and references, and contacted experts for unpublished data. Sixty-six publications and unpublished data of 14 patients resulted in 198 patients with 1084 tests for cross-reactivity. The primary causative agents were mostly unfractionated heparin (50%) and low molecular weight heparins (49.5%). Cross-reactions were more likely after an initial DTH reaction to unfractionated heparin than after an initial DTH reaction to low molecular weight heparin. Our findings also indicate that molecular weight does not correlate with the risk for cross-reactivity, which is in line with recent observations, indicating that different heparins have to be individually considered. The available data demonstrated the lowest overall risk for cross-reactions for pentosan polysulfate (36.4%) and fondaparinux (10.4%). In the clinical context, fondaparinux is recommended as the current best alternative when a DTH reaction occurs. © 2011 John Wiley & Sons A/S.

Effect of Sulfation and Molecular Weight on Anticoagulant Activity of Dextran.

PubMed

Drozd, N N; Logvinova, Yu S; Torlopov, M A; Udoratina, E V

2017-02-01

Sulfation (to 2.8) of dextrans with molecular weight of 150 and 20 kDa was followed by the appearance of anticoagulant activity that increased with decreasing their molecular weight and did not depend on antithrombin, plasma inhibitor of serine proteases of the blood coagulation system. Antithrombin activity of dextran sulfate with a molecular weight of 20 kDa reached 12.6-15.3 U/mg. Dextran sulfates with molecular weights of 20 and 150 kDa did not potentiate ADP-induced human platelet aggregation.

Determination of the absolute molecular weight averages and molecular weight distributions of alginates used as ice cream stabilizers by using multiangle laser light scattering measurements.

PubMed

Turquois, T; Gloria, H

2000-11-01

High-performance size exclusion chromatography with multiangle laser light scattering detection (HPSEC-MALLS) was used for characterizing complete molecular weight distributions for a range of commercial alginates used as ice cream stabilizers. For the samples investigated, molecular weight averages were found to vary between 115 000 and 321 700 g/mol and polydispersity indexes varied from 1. 53 to 3.25. These samples displayed a high content of low molecular weights. Thus, the weight percentage of material below 100 000 g/mol ranged between 6.9 and 54.4%.

Contamination of agricultural lands by polycyclic aromatic hydrocarbons (Tver region, Russia)

NASA Astrophysics Data System (ADS)

Zhidkin, Andrey; Koshovskii, Timur; Gennadiev, Alexander

2016-04-01

It is important to study sources and concentrations of polycyclic aromatic hydrocarbons (PAHs) in the agriculture soils within areas without intensive contaminations. Our studied object was soil and snow cover in the taiga zone (Tver region, Russia). A total of 52 surface (0-30 cm) and 31 subsurface (30-50 cm) soil samples, and 13 snow samples were collected in 35 soil pits, located in forest, crop and layland soils. Studied concentrations of the following 11 individual compounds: two-ring compounds (diphenyl and naphthalene homologues); three-ring compounds (fluorene, phenanthrene, anthracene); four-ring compounds (chrysene, pyrene, tetraphene); five-ring compounds (perylene, benzo[a]pyrene); and six-ring compounds (benzo[ghi]perylene). Analyses made by specrtofluorometry method at the temperature of liquid nitrogen. The total concentrations of all PAHs in soil samples ranged from 9 to 770 ng*g-1 with a median of 96 ng*g-1. The sum of high molecular weight PAHs was significantly lower than the sum of low molecular weight PAHs in the studied soils. The phenanthrene concentration was highest and ranged from 1.2 to 720 ng*g-1 (medium 72 ng*g-1). Compared PAHs reserves in snow cover (μg*m-2) with the reserves in topsoil layer (μg*m-2 in the upper 30 cm). Low molecular weight PAHs (fluorene, phenanthrene, diphenyl, naphthalene) reserves in snow was less than 20% from the reserves in the soil surface layer. High molecular weight PAHs (benzo[a]pyrene, chrysene, perylene, pyrene and tetraphene) reserves in snow was about 50-70% from the reserves in soil surface layer. High molecular weight PAHs (benzo[ghi]perylene and anthracene) reserves in snow was more than in topsoil. PAHs vertical distribution in soil profiles was statistically examined. The total concentration of all PAHs decreased with depth in all studied forest soils. In the arable soils was no significant trend in domination of PAHs total concentrations in the plowing and subsoil layers. The ratio of topsoil to subsoil concentrations of PAHs is different for differ congeners. Contents of phenanthrene and fluorene predominantly increase with the depth. Content of high molecular weight PAHs (benzo[a]pyrene, anthracene, tetraphene, perylene and pyrene) predominantly decreased with the depth. Other PAHs congeners have indistinct profile distributions in studied pits. Based on studied results PAHs divided to associations with different concentrations, sources and vertical distribution in soils: a) phenanthrene and fluorine; b) naphthalene, diphenyl; c) pyrene, benzo(a)pyrene, tetraphene, perylene, chrysene; d) anthracene and benzo(ghi)perylene. Research is funded by Russian Science Foundation (Project 14-27-00083).

Gel filtration applied to the study of lipases and other esterases

PubMed Central

Downey, W. K.; Andrews, P.

1965-01-01

1. Sephadex G-100 and G-200 gel-filtration columns were calibrated for molecular-weight estimation with proteins of known molecular weights, and used to study the composition of several lipase or esterase preparations. 2. Enzymes from cow's milk, rat adipose tissue and pig pancreas were detected in the column effluents by their ability to liberate free acid from emulsified tributyrin at pH 8·5. 3. Four tributyrinases were detected in preparations from individual cow's milks. Molecular weights 62000, 75000 and 112000 were estimated for three of them, but although the fourth may be of unusually low molecular weight an estimate was not possible. 4. Extracts of rat adipose tissue apparently contained six tributyrinases (molecular weights 39000, 47000, 55000, 68000, 75000 and 200000) but the relative amounts of these enzymes varied widely from rat to rat. 5. Tributyrinase activity in juice expressed from pig pancreatic tissue was due mainly to one enzyme (molecular weight 42000). On the other hand, activity in extracts of acetone-dried pancreas was confined to material of molecular weight > 106, which may be an aggregated form of the lower-molecular-weight enzyme. 6. Activity in fractionated wheat-germ extracts was assayed with emulsified triacetin substrate, and was evidently due to one enzyme (molecular weight 51000). 7. Some problems arising in the application of gel filtration to the study of lipase–esterase systems were indicated. PMID:14340054

A comparison study between different molecular weight polysaccharides derived from Lentinus edodes and their antioxidant activities in vivo.

PubMed

You, Ruxu; Wang, Kaiping; Liu, Jinyu; Liu, Maochang; Luo, Li; Zhang, Yu

2011-12-01

Polysaccharide purified Lentinus edodes (Berk.) Sing (Tricholomataceae) has been reported to attenuate oxidative stress in vitro. This study investigated whether polysaccharides from L. edodes with different molecular weight have protective effects against oxidative stress induced by D-galactose (D-gal) in vivo, and determined the specific relationship between molecular weight and antioxidant activity. In the present study, we successfully obtained three purified polysaccharides, coded as LT1, LT2, and LT3, and their molecular weights were 25.5, 306.2, and 605.4 kDa, respectively. The D-gal-treated mice received three polysaccharides once daily for 60 days. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), the content of malondialdehyde (MDA), and erythrocyte membrane fluidity were measured to evaluate the changes of the antioxidant ability. It was demonstrated that the administration of LT1, LT2, and LT3 could improve the antioxidant status to different levels. Furthermore, LT2 exhibited the highest antioxidant ability among these samples in vivo. Indeed, LT2 significantly decreased the content of MDA in liver (15.91 ± 0.31 versus 23.79 ± 1.18 nmol/mg protein for the model group, p < 0.05), enhanced the fluidity of erythrocyte membrane (2.458 ± 0.023 versus 2.167 ± 0.024 for the model group, p < 0.05), and increased the activities of SOD (147.19 ± 4.90 versus 82.26 ± 5.55 units/mg protein for the model group, p < 0.05) and GSH-Px (310.91 ± 6.24 versus 243.64 ± 6.77 units/mg protein for the model group, p < 0.05) in liver. The LT2 had a potential to be used as a novel natural antioxidant.

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

PubMed

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

2016-01-01

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. 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. 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). 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.

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.

Molecular cloning of the perilipin gene and its association with carcass and fat traits in Chinese ducks.

PubMed

Zhang, H L; Fan, H J; Liu, X L; Wu, Y; Hou, S S

2013-05-13

The perilipin (PLIN) gene is a candidate gene of carcass and fat traits in ducks. In order to study the molecular character of the PLIN gene and its function in different breeds of Chinese ducks, samples were obtained from the Chinese Academy of Agricultural Sciences Research Center for Birds, including 95 Peking ducks of the Z2 series, 91 Peking ducks of the Z4 series, 82 hybrid systems (Z2 x Z4), and 93 Cherry Valley ducks. We used RT-PCR and 3'-RACE to clone the duck PLIN gene, detect SNPs and analyze their associations with carcass and fat traits. A 2212-bp sequence was cloned with the complete coding region and a 3'-untranslated region. We found a nucleotide mutation (C → T) in exon 2 of the PLIN gene. There were no significant correlations between the 3 genotypes (CC, CT, TT) in breast muscle weight (BMW), leg muscle weight (LMW), subcutaneous fat weight (SFW), and intramuscular fat (IMF) in the Cherry Valley duck. The CC and CT genotypes had significant differences in carcass weight (CW), carcass net weight (CNW), and percentage of abdominal fat weight (AFW); there were significant differences in AFW and percentage of SFW. In Z4, there were no significant correlations between the 3 genotypes (TT, CC, and CT) in CW, BMW, LMW, SFW, AFW, the percentage of SFW and AFW, and IMF. CNW was significantly different between TT, CC, and CT genotypes. In Z2 x Z4, there were no significant correlations between the 3 genotypes in CW, BMW, LMW, SFW, AFW, the percentage of SFW and AFW, and IMF, while the CC and CT genotypes had significant differences in CNW. In Z2, there were no significant differences between the 3 genotypes in all traits. We deduced that the PLIN gene is a potential major gene. It is linked to a major gene affecting meat quality traits. This SNP has potential as a molecular marker for marker-assisted selection.

Extraction of pectins and hemicelluloses from cell walls of suspension culture cells of cotton by endopolygalacturonase treatment

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

An, Jinhua; Maness, N.O.; Mort, A.J.

1989-04-01

Walls of cotton suspension cultures were treated with a highly purified endopolygalacturonase coded for by a gene from Erwinia carotovora expressed in E. coli. About 80 percent of the walls galacturonic acid was solubilized and could be fractionated by ion exchange chromatography into three classes: (1) tri- and tetra-galacturonides from digestion of homogalacturonans, (2) high molecular weight fragments rich in galacturonic acid, rhamnose and other neutral sugars indicative of rhamnogalacturonan I, and (3) a well defined low molecular weight polymer resembling rhamnogalacturonan II. Treatment of the insoluble wall residue with alkali allowed extraction of the remainder of the wall galacturonicmore » acid as high molecular weight polymers resembling rhamnogalacturonan I but in association with what is probably xyloglucan. The purified polymers will be compared to those obtained by others from different species, especially those of sycamore.« less

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.

HA metabolism in skin homeostasis and inflammatory disease.

PubMed

Kavasi, Rafaela-Maria; Berdiaki, Aikaterini; Spyridaki, Ioanna; Corsini, Emanuela; Tsatsakis, Aristidis; Tzanakakis, George; Nikitovic, Dragana

2017-03-01

Hyaluronan (HA), an unsulfated glycosaminoglycan, is an important component of the complex extracellular matrix network which surrounds and supports cells in tissues. HA is detected in all vertebrate tissues, but the bulk of HA is produced and deposited in the skin. In this review we focus on the role of HA in skin-associated inflammatory disease and wound healing. Properties of HA are directly dependent on its molecular weight. Thus, high molecular weight HA (HMWHA) is deposited in normal tissues during homeostasis and promotes their stability whereas low molecular weight HA fragments (LMWHA), on the other hand, may arise from enzymatic or chemical activities. The degradation of HMWHA to LMWHA fragments, often leads to the generation of biologically active oligosaccharides with different properties and postulated functions in wound scar formation and inflammation. More detailed studies of HA involvement in skin-associated inflammatory disease may result in novel treatment modalities. Copyright © 2017 Elsevier Ltd. All rights reserved.

Improvement of antioxidant and moisture-preserving activities of Sargassum horneri polysaccharide enzymatic hydrolyzates.

PubMed

Shao, Ping; Chen, Xiaoxiao; Sun, Peilong

2015-03-01

In the previous study, we have found that polysaccharides isolated from Sargassum horneri exhibited bioactivities. The aim of this study was to investigate the antioxidant and moisture-preserving activities of molecular weight alteration of Sargassum horneri polysaccharide in vitro. For this purpose, the homogeneous active polysaccharide SHP was isolated from Sargassum horneri, and response surface methodology was employed to optimize the enzymatic degradation conditions to get SHP-derived fragments with different molecular weight. Results proved that the polysaccharide is capable of scavenging both ABTS and DPPH radicals in vitro. The study revealed that the polysaccharides had strong moisture-absorption and -retention capacities as compared to propanediol and glycerin. Furthermore, these data demonstrated that molecular weight had a certain effect on antioxidant activities and strong moisture-retention capacities of the polysaccharide from Sargassum horneri. Copyright © 2014 Elsevier B.V. All rights reserved.

Surface properties of poly(acrylonitrile) (PAN) precipitation polymerized in supercritical CO2 and the influence of the molecular weight.

PubMed

Shen, Qing; Gu, Qing-Feng; Hu, Jian-Feng; Teng, Xin-Rong; Zhu, Yun-Feng

2003-11-15

In this paper, the surface properties, e.g., the total surface free energy and the related Lifshitz-van der Waals and Lewis acid-base components, of polyacrylonitrile (PAN) precipitation polymerized in supercritical CO(2) have been characterized. Moreover, the influence of molecular weight varying has been also investigated. Results show that the surface properties of PAN resulting from supercritical CO(2) are different from those obtained by the conventional method. Of these data, one important finding is that the supercritical CO(2) PAN seems to decrease the surface free energy with the increased molecular weight. Based on previous recorded NMR spectra of this PAN and especially compared to commercial PAN, such phenomena are discussed and ascribed to an increase of the H-bonds and a reduction of the isotacticity in the supercritical CO(2) condition for PAN.

The composition of peptidochitodextrins from sarcophagid puparial cases

PubMed Central

Lipke, H.; Geoghegan, T.

1971-01-01

1. N-Bromosuccinimide cleaved proteins and pigments from fly puparia, increasing the chitin:protein ratio from 0.5 to 1.5. The product afforded subfractions (ratio 5:1) of molecular weights of 1200 and 1600 devoid of aromatic residues and N-terminal β-alanine, direct aryl links between polysaccharide chains being discounted. 2. The chitin–protein complex decreased in molecular weight when treated with Pronase, which suggested polypeptide bridges within the native chitin micelle. The limit dextrins generated by chitinase were mixtures of unsubstituted dextrins and peptidylated oligosaccharides, with the former predominating. 3. Peptidochitodextrins of similar molecular weight but markedly different solubility were prepared, which were indistinguishable with respect to amino acid, glucosamine, acetyl, X-ray or infrared characteristics. It is suggested that physical interactions contribute to the stability of the integument in addition to the covalent bonds that form during sclerotization. PMID:5145884

Role of Laccase and Low Molecular Weight Metabolites from Trametes versicolor in Dye Decolorization

PubMed Central

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

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.

Solubility of crystalline organic compounds in high and low molecular weight amorphous matrices above and below the glass transition by zero enthalpy extrapolation.

PubMed

Amharar, Youness; Curtin, Vincent; Gallagher, Kieran H; Healy, Anne Marie

2014-09-10

Pharmaceutical applications which require knowledge of the solubility of a crystalline compound in an amorphous matrix are abundant in the literature. Several methods that allow the determination of such data have been reported, but so far have only been applicable to amorphous polymers above the glass transition of the resulting composites. The current work presents, for the first time, a reliable method for the determination of the solubility of crystalline pharmaceutical compounds in high and low molecular weight amorphous matrices at the glass transition and at room temperature (i.e. below the glass transition temperature), respectively. The solubilities of mannitol and indomethacin in polyvinyl pyrrolidone (PVP) K15 and PVP K25, respectively were measured at different temperatures. Mixtures of undissolved crystalline solute and saturated amorphous phase were obtained by annealing at a given temperature. The solubility at this temperature was then obtained by measuring the melting enthalpy of the crystalline phase, plotting it as a function of composition and extrapolating to zero enthalpy. This new method yielded results in accordance with the predictions reported in the literature. The method was also adapted for the measurement of the solubility of crystalline low molecular weight excipients in amorphous active pharmaceutical ingredients (APIs). The solubility of mannitol, glutaric acid and adipic acid in both indomethacin and sulfadimidine was experimentally determined and successfully compared with the difference between their respective calculated Hildebrand solubility parameters. As expected from the calculations, the dicarboxylic acids exhibited a high solubility in both amorphous indomethacin and sulfadimidine, whereas mannitol was almost insoluble in the same amorphous phases at room temperature. This work constitutes the first report of the methodology for determining an experimentally measured solubility for a low molecular weight crystalline solute in a low molecular weight amorphous matrix. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of polyacrylamide on soil physical and hydraulic properties

NASA Astrophysics Data System (ADS)

Albalasmeh, Ammar; Gharaibeh, Mamoun; Hamdan, Enas

2017-04-01

The effect of polyacrylamide (PAM), as a soil conditioner, on selected soil physical and hydraulic properties (infiltration rate (f(t)), hydraulic conductivity (HC), soil moisture content, aggregate stability (AS), and soil aggregation) was studied. Two types of anionic PAM were used: Low molecular weight (LPAM) (1×105 g/mol) with medium charge density (33-43) and high molecular weight (HPAM) (1-6×106 g/mol) with medium charge density (33-43). Sandy loam soil was packed into plastic columns; PAM solutions at different concentrations (100, 250, 500, and 1000 mg L-1) were used every two weeks in four wetting and drying cycles. The highest infiltration rate value was 0.16 mm s-1 at 1000 mg/L low molecular weight PAM while the highest value of infiltration rate in high PAM molecular weight was 0.11 mm s-1 compared to the control (0.01 mm s-1). Soil HC was about 3.00 cm h-1 for LPAM at 1000 mg L-1 PAM, while the highest value for HPAM was about 2 cm h-1 for the same concentration, compared to the control. The amount of water that can be held by soil increased with the addition of PAM compared to the control. Differences in water content were more pronounced in LPAM compared to HPAM. The addition of LPAM increased aggregate stability proportional to PAM concentration. Moreover, 1000 mg L-1 produced the highest aggregate stability (19{%}) compared to HPAM and control (7{%} and 5{%}), respectively. As PAM concentration increased, the geometric mean diameter (GMD) increased for both PAM molecular weights compared to control (0.4 mm). At 1000 mg L-1 the GMD values were 0.88 mm and 0.79 mm for LPAM and HPAM, respectively. The addition of PAM improved soil physical and hydraulic properties, with an advantage to LPAM owing that to its ability to penetrate soil aggregates and therefore stabilizing them.

High resolution mass spectrometry method and system for analysis of whole proteins and other large molecules

DOEpatents

Reilly, Peter T. A. [Knoxville, TN; Harris, William A [Naperville, IL

2010-03-02

A matrix assisted laser desorption/ionization (MALDI) method and related system for analyzing high molecular weight analytes includes the steps of providing at least one matrix-containing particle inside an ion trap, wherein at least one high molecular weight analyte molecule is provided within the matrix-containing particle, and MALDI on the high molecular weight particle while within the ion trap. A laser power used for ionization is sufficient to completely vaporize the particle and form at least one high molecular weight analyte ion, but is low enough to avoid fragmenting the high molecular weight analyte ion. The high molecular weight analyte ion is extracted out from the ion trap, and is then analyzed using a detector. The detector is preferably a pyrolyzing and ionizing detector.

Process for crosslinking and extending conjugated diene-containing polymers

NASA Technical Reports Server (NTRS)

Bell, Vernon L. (Inventor); Havens, Stephen J. (Inventor)

1977-01-01

A process using a Diels-Alder reaction which increases the molecular weight and/or crosslinks polymers by reacting the polymers with bisunsaturated dienophiles is developed. The polymer comprises at least 75% by weight based on the reaction product, has a molecular weight of at least 5000 and a plurality of conjugated 1,3-diene systems incorporated into the molecular structure. A dienophile reaction with the conjugated 1,3-diene of the polymer is at least 1% by weight based on the reaction product. Examples of the polymer include polyesters, polyamides, polyethers, polysulfones and copolymers. The bisunsaturated dienophiles may include bis-maleimides, bis maleic and bis tumaric esters and amides. This method for expanding the molecular weight chains of the polymers, preferable thermoplastics, is advantageous for processing or fabricating thermoplastics. A low molecular weight thermoplastic is converted to a high molecular weight plastic having improved strength and toughness for use in the completed end use article.

Molecular forms of C-type natriuretic peptide in cerebrospinal fluid and plasma reflect differential processing in brain and pituitary tissues.

PubMed

Wilson, Michele O; Barrell, Graham K; Prickett, Timothy C R; Espiner, Eric A

2018-01-01

C-type natriuretic peptide (CNP) is a paracrine growth factor widely expressed within tissues of the central nervous system. Consistent with this is the high concentration of CNP in cerebrospinal fluid (CSF), exceeding levels in the systemic circulation. CNP abundance is high in hypothalamus and especially enriched in pituitary tissue where - in contrast to hypothalamus - processing to CNP-22 is minimal. Recently we have shown that dexamethasone acutely raises CNP peptides throughout the brain as well as in CSF and plasma. Postulating that molecular forms of CNP would differ in central tissues compared to forms in pituitary and plasma, we have characterized the molecular forms of CNP in tissues (hypothalamus, anterior and posterior pituitary gland) and associated fluids (CSF and plasma) using size-exclusion high performance liquid chromatography (SE-HPLC) and radioimmunoassay in control (saline-treated) and dexamethasone-treated adult sheep. Three immunoreactive-CNP components were identified which were consistent with proCNP (1-103), CNP-53 and CNP-22, but the presence and proportions of these different fragments differed among tissues. Peaks consistent with CNP-53 were the dominant form in all tissues and fluids. Peaks consistent with proCNP, conspicuous in hypothalamic extracts, were negligible in CSF whereas proportions of low molecular weight immunoreactivity (IR) consistent with CNP-22 were similar in hypothalamus, posterior pituitary gland and CSF. In contrast, in both plasma and the anterior pituitary gland, proportions of higher molecular weight IR, consistent with CNP-53 and proCNP, predominated, and low molecular weight IR consistent with CNP-22 was very low. After dexamethasone, proCNP like material - but not other forms - was increased in all samples except CSF, consistent with increased synthesis and secretion. In conclusion, immunoreactive forms of CNP in central tissues differ from those identified in anterior pituitary tissue and plasma - suggesting that the anterior pituitary gland may contribute to systemic levels of CNP in some physiological settings. Copyright © 2017 Elsevier Inc. All rights reserved.

Elucidation of differences in N-glycosylation between different molecular weight forms of recombinant CLEC-2 by LC MALDI tandem MS.

PubMed

Zhou, Lei; Qian, Yifan; Zhang, Xingwang; Ruan, Yuanyuan; Ren, Shifang; Gu, Jianxin

2015-01-30

C-type lectin-like receptor 2 (CLEC-2) is a newly identified receptor expressed on the platelet surface. It has been reported that CLEC-2 exists as a higher molecular weight (HMW) and a lower molecular weight (LMW) form, which share the same protein core but differ in glycans. The two forms appear to have different ligand-binding abilities, indicating that the differential glycosylation of CLEC-2 possibly produces functionally distinct glycoforms. This study aimed to explore an easy method to directly elucidate the N-glycosylation difference by employing a glycoproteomics approach. The off-line coupling of nano-LC with a MALDI-QIT-TOF mass spectrometer was demonstrated to be capable of sensitive and direct elucidation of the glycosylation difference between HMW and LMW CLEC-2, simultaneously providing information about their oligosaccharide structures and the glycosylation sites. The results reveal that a specific glycosylation site, Asn 134, is differently glycosylated in the two forms, with complex types of bi-antennary, tri-antennary and tetra-antennary, N-linked, fucosylated glycans identified at this site in the HMW form but not in the LMW form. The observed difference in glycosylation might provide new insights into the underlying mechanisms of biological functions of CLEC-2. Because of its simplicity and sensitivity, the method explored in this work suggests that it holds promise as a method of elucidating differences in direct N-glycosylation of target glycoprotein, even in small amount of samples. Copyright © 2014 Elsevier Ltd. All rights reserved.

Viscoelastic properties of cationic starch adsorbed on quartz studied by QCM-D.

PubMed

Tammelin, Tekla; Merta, Juha; Johansson, Leena-Sisko; Stenius, Per

2004-12-07

The adsorption and viscoelastic properties of layers of a cationic polyelectrolyte (cationic starch, CS, with 2-hydroxy-3-trimethylammoniumchloride as the substituent) adsorbed from aqueous solutions (pH 7.5, added NaCl 0, 1, 100, and 500 mM) on silica were studied with a quartz crystal microbalance with dissipation (QCM-D). Three different starches were investigated (weight-average molecular weights M(w) approximately 8.7 x 10(5) and 4.5 x 10(5) with degree of substitution DS = 0.75 and M(w) approximately 8.8 x 10(5) with DS = 0.2). At low ionic strength, the adsorbed layers are thin and rigid and the amount adsorbed can be calculated using the Sauerbrey equation. When the ionic strength is increased, significant changes take place in the amount of adsorbed CS and the viscoelasticity of the adsorbed layer. These changes were analyzed assuming that the layer can be described as a Voigt element on a rigid surface in contact with purely viscous solvent. It was found that CS with low charge density forms a thicker and more mobile layer with higher viscosity and elasticity than CS with high charge density. The polymers adsorbed on the silica even when the ionic strength was so high that electrostatic interactions were effectively screened. At this high ionic strength, it was possible to study the effect of molecular weight and molecular weight distribution of the CS on the properties of the adsorbed film. Increasing the molecular weight of CS resulted in a larger hydrodynamic thickness. CS with a narrow molecular weight distribution formed a more compact and rigid layer than broadly distributed CS, presumably due to the better packing of the molecules.

Probing the effect of polymer molecular weight on penetration into the wood cell wall using polyethylenimine (PEI) as a model compound.

PubMed

Dorvel, Brian; Boopalachandran, Praveenkumar; Chen, Ida; Bowling, Andrew; Williams, Kerry; King, Steve

2018-05-01

Decking is one of the largest applications for the treated wood market. The most challenging property to obtain for treated wood is dimensional stability, which can be achieved, in part, by cell wall bulking, cell wall polymer crosslinking and removal of hygroscopic components in the cell wall. A commonly accepted key requirement is for the actives to infuse through the cell wall, which has a microporosity of ∼5-13 nm. Equally as challenging is being able to measure and quantify the cell wall penetration. Branched polyethylenimine (PEI) was studied as a model polymer for penetration due to its water solubility, polarity, variable molecular weight ranges, and ability to form a chelation complex with preservative metals to treat lumbers. Two different molecular weight polyethylenimines (PEI), one with a weight average molecular weight (Mw) equal to 800 Da and the other 750 000 Da, were investigated for penetration by microscopy and spectroscopy techniques. Analytical methods were developed to both create smooth interfaces and for relative quantitation and visualisation of PEI penetration into the wood. The results showed both PEI with Mw of 800 Da and PEI with Mw of 750 000 Da coated the lumens in high density. However, only the PEI with Mw of 800 appeared to penetrate the cell walls in sufficient levels. Literature has shown the hydrodynamic radii of PEI 750 000 is near 29 nm, whereas a smaller PEI at 25 K showed 4.5 nm. Most importantly the results, based on methods developed, show how molecular weight and tertiary structure of the polymer can affect its penetration, with the microporosity of the wood being the main barrier. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Production of high molecular weight polylactic acid

DOEpatents

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.

Composition and functionality of bone affected by dietary glycated compounds.

PubMed

Delgado-Andrade, Cristina; Roncero-Ramos, Irene; Carballo, José; Rufián-Henares, Joséángel; Seiquer, Isabel; Navarro, María Pilar

2013-04-25

Our aim was to investigate the effects of Maillard reaction products (MRPs) from bread crust (BC) on bone composition and its mechanical properties, determining whether any such effects are related to the molecular weight of different MRPs. For 88 days after weaning rats were fed a control diet or diets containing BC, or its soluble low molecular weight (LMW), soluble high molecular weight (HMW) or insoluble fractions. Animals' food consumption and body weights were monitored. After sacrifice, the femur, pelvic bone and tibia were removed for composition, physical and biomechanical properties analysis. It was found that body and femur weights, density, volume and organic matrix decreased, whereas pentosidine increased after consumption of experimental diets, especially in the HMW and insoluble groups (104.7 and 102.9 mmol mol(-1) collagen) vs. the control group (41.7 mmol mol(-1) collagen). Bone stiffness fell by 50% in the LMW, HMW and insoluble groups and failure load and energy to failure tended to decrease in the same animals after MRPs intake. Consumption of diets containing assayed MRPs during growth leads to lower bone size and introduces some changes in its mechanical behavior which appear to be related to an increase in the pentosidine level of bone.

Differentiating low-molecular-weight heparins based on chemical, biological, and pharmacologic properties: implications for the development of generic versions of low-molecular-weight heparins.

PubMed

Jeske, Walter P; Walenga, Jeanine M; Hoppensteadt, Debra A; Vandenberg, Curtis; Brubaker, Aleah; Adiguzel, Cafer; Bakhos, Mamdouh; Fareed, Jawed

2008-02-01

Low-molecular-weight heparins (LMWHs) are polypharmacologic drugs used to treat thrombotic and cardiovascular disorders. These drugs are manufactured using different chemical and enzymatic methods, resulting in products with distinct chemical and pharmacologic profiles. Generic LMWHs have been introduced in Asia and South America, and several generic suppliers are seeking regulatory approval in the United States and the European Union. For simple small-molecule drugs, generic drugs have the same chemical structure, potency, and bioavailability as the innovator drug. Applying this definition to complex biological products such as the LMWHs has proved difficult. One major issue is defining appropriate criteria to demonstrate bioequivalence; pharmacopoeial specifications alone appear to be inadequate. Whereas available generic versions of LMWHs exhibit similar molecular and pharmacopoeial profiles, marked differences in their biological and pharmacologic behavior have been noted. Preliminary studies have demonstrated differences in terms of anti-Xa activity and tissue factor pathway inhibitor release after subcutaneous administration, as well as antiplatelet and profibrinolytic effects. The current data emphasize the need to consider multiple functional parameters when defining bioequivalence of biologic drugs with complex structures and activities and also underscore the importance of further pharmacologic studies involving animal models and human clinical trials. The U.S. Food and Drug Administration and the European Medicine Evaluation Agency are currently developing guidelines for the acceptance of biosimilar agents including LMWHs. Until such guidelines are complete, generic interchange may not be feasible.

Raw materials for wood-polymer composites.

Treesearch

Craig Clemons

2008-01-01

To understand wood-plastic composites (WPCs) adequately, we must first understand the two main constituents. Though both are polymer based, they are very different in origin, structure, and performance. Polymers are high molecular weight materials whose performance is largely determined by its molecular architecture. In WPCs, a polymer matrix forms the continuous phase...

Molecular Weight of Deoxyribonucleic Acid Synthesized During Initiation of Chromosome Replication in Escherichia coli

PubMed Central

Kuempel, Peter L.

1972-01-01

Alkaline sucrose gradients were used to study the molecular weight of deoxyribonucleic acid (DNA) synthesized during the initiation of chromosome replication in Escherichia coli 15 TAU-bar. The experiments were conducted to determine whether newly synthesized, replication origin DNA is attached to higher-molecular-weight parental DNA. Little of the DNA synthesized after readdition of required amino acids to cells previously deprived of the amino acids was present in DNA with a molecular weight comparable to that of the parental DNA. The newly synthesized, low-molecular-weight DNA rapidly appeared in higher-molecular-weight material, but there was an upper limit to the size of this intermediate-molecular-weight DNA. This limit was not observed when exponentially growing cells converted newly synthesized DNA to higher-molecular-weight material. The size of the intermediate-molecular-weight DNA was related to the age of the replication forks, and the size increased as the replication forks moved further from the replication origin. The results indicate that the newly synthesized replication origin DNA is not attached to parental DNA, but it is rapidly attached to the growing strands that extend from the replication fork to the replication origin, or to the other replication fork if replication is bidirectional. Experiments are reported which demonstrate that the DNA investigated was from the vicinity of the replication origin and was not plasmid DNA or DNA from random positions on the chromosome. PMID:4562387

Preparation of poly(ethylene glycol) hydrogels with different network structures for the application of enzyme immobilization.

PubMed

Choi, Dongkil; Lee, Woojin; Park, Jinwon; Koh, Wongun

2008-01-01

In this study, poly(ethylene glycol) (PEG)-based hydrogels having different network structures were synthesized by UV-initiated photopolymerization and used for the enzyme immobilization. PEGs with different molecular weight were acrylated by derivatizing both ends with acryloyl chloride and photopolymerization of PEG-diacrylate (PEG-DA) yielded crosslinked hydrogel network within 5 seconds. Attachment of acrylate groups and gelation were confirmed by ATR/FT-IR and FT-Raman spectroscopy. Network structures of hydrogels could be easily controlled by changing the molecular weight (MW) of PEG-DA and characterized by calculating molecular weight between crosslinks and mesh size from the swelling measurement. Synthesis of hydrogels with higher MW of PEG produced less crosslinked hydrogels having higher water content, larger value of Mc and mesh size, which resulted in enhanced mass transfer but loss of mechanical properties. For the enzyme immobilization, glucose oxidase (GOX) was immobilized inside PEG hydrogels by means of physical entrapment and covalent immobilization. Encapsulated GOX were covalently bound to PEG backbone using acryloyl-PEG-N-hydroxysuccinimide and maintained their activity over a week period without leakage. Kinetic study indicated that immobilized enzyme inside hydrogel prepared from higher MW of PEG possessed lower apparent Km (Michaelis-Menten constant) and higher activity.

Extraction of High Molecular Weight DNA from Fungal Rust Spores for Long Read Sequencing.

PubMed

Schwessinger, Benjamin; Rathjen, John P

2017-01-01

Wheat rust fungi are complex organisms with a complete life cycle that involves two different host plants and five different spore types. During the asexual infection cycle on wheat, rusts produce massive amounts of dikaryotic urediniospores. These spores are dikaryotic (two nuclei) with each nucleus containing one haploid genome. This dikaryotic state is likely to contribute to their evolutionary success, making them some of the major wheat pathogens globally. Despite this, most published wheat rust genomes are highly fragmented and contain very little haplotype-specific sequence information. Current long-read sequencing technologies hold great promise to provide more contiguous and haplotype-phased genome assemblies. Long reads are able to span repetitive regions and phase structural differences between the haplomes. This increased genome resolution enables the identification of complex loci and the study of genome evolution beyond simple nucleotide polymorphisms. Long-read technologies require pure high molecular weight DNA as an input for sequencing. Here, we describe a DNA extraction protocol for rust spores that yields pure double-stranded DNA molecules with molecular weight of >50 kilo-base pairs (kbp). The isolated DNA is of sufficient purity for PacBio long-read sequencing, but may require additional purification for other sequencing technologies such as Nanopore and 10× Genomics.

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. Copyright © 2014 Elsevier B.V. All rights reserved.

Physicochemical characteristics and biological activities of polysaccharide fractions from Phellinus baumii cultured with different methods.

PubMed

Li, Tingting; Yang, Yan; Liu, Yanfang; Zhou, Shuai; Yan, Meng Qiu; Wu, Di; Zhang, Jingsong; Tang, Chuanhong

2015-11-01

Nine polysaccharide fractions were obtained from the fruiting bodies, submerged mycelia, and solid state fermented products of Phellinus baumii using different concentrations of ethanol precipitation. The chemical characteristics and in vitro immunological activities of the nine polysaccharide fractions were compared and studied. Results indicated that the fractions precipitated with 50% ethanol had higher yields of polysaccharides and submerged mycelia contributed to high extraction yields of polysaccharides and possessed higher polysaccharide contents. HPSEC-MALLS-RI analysis showed that the molecular weight (Mw) of polysaccharide fractions from these three materials decreased with the increasing of precipitated ethanol concentration. The Mw of fruiting body polysaccharide fractions ranged from 1.98×10(4)Da to 1.89×10(6)Da. Large-molecular-weight polysaccharides (from 2.11×10(6)Da to 2.01×10(7)Da) were found in submerged mycelia. Some lower-molecular-weight polysaccharide components were found in solid fermented products. Different culture methods contributed to significant differences in monosaccharide components and molar ratios. The 50% ethanol precipitated fractions exhibited more complexity on monosaccharide compositions comparing with fractions precipitated with 30% and 70% ethanol. Polysaccharide fractions derived from submerged mycelia exhibited higher macrophages stimulation activities. Submerged culture was found to be a suitable method to prepare active polysaccharides because of its short culture span and reasonable cost. Copyright © 2015 Elsevier B.V. All rights reserved.

'Ogura'-based 'CMS' lines with different nuclear backgrounds of cabbage revealed substantial diversity at morphological and molecular levels.

PubMed

Parkash, Chander; Kumar, Sandeep; Singh, Rajender; Kumar, Ajay; Kumar, Satish; Dey, Shyam Sundar; Bhatia, Reeta; Kumar, Raj

2018-01-01

A comprehensive study on characterization and genetic diversity analysis was carried out in 16 'Ogura'-based 'CMS' lines of cabbage using 14 agro-morphological traits and 29 SSR markers. Agro-morphological characterization depicted considerable variations for different horticultural traits studied. The genotype, ZHA-2, performed better for most of the economically important quantitative traits. Further, gross head weight (0.76), head length (0.60) and head width (0.83) revealed significant positive correlation with net head weight. Dendrogram based on 10 quantitative traits exhibited considerable diversity among different CMS lines and principle component analysis (PCA) indicated that net and gross head weight, and head length and width are the main components of divergence between 16 CMS lines of cabbage. In molecular study, a total of 58 alleles were amplified by 29 SSR primers, averaging to 2.0 alleles in each locus. High mean values of Shannon's Information index (0.62), expected (0.45) and observed (0.32) heterozygosity and polymorphic information content (0.35) depicted substantial polymorphism. Dendrogram based on Jaccard's similarity coefficient constructed two major groups and eight sub-groups, which revealed substantial diversity among different CMS lines. In overall, based on agro-morphological and molecular studies genotype RRMA, ZHA-2 and RCA were found most divergent. Hence, they have immense potential in future breeding programs for the high-yielding hybrid development in cabbage.

Production of high molecular weight polylactic acid

DOEpatents

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.

Spray-dried chitosan as a direct compression tableting excipient.

PubMed

Chinta, Dakshinamurthy Devanga; Graves, Richard A; Pamujula, Sarala; Praetorius, Natalie; Bostanian, Levon A; Mandal, Tarun K

2009-01-01

The objective of this study was to prepare and evaluate a novel spray-dried tableting excipient using a mixture of chitosan and lactose. Three different grades of chitosan (low-, medium-, and high-molecular-weight) were used for this study. Propranolol hydrochloride was used as a model drug. A specific amount of chitosan (1, 1.9, and 2.5 g, respectively) was dissolved in 50 mL of an aqueous solution of citric acid (1%) and later mixed with 50 mL of an aqueous solution containing lactose (20, 19.1, and 18.5 g, respectively) and propanolol (2.2 g). The resultant solution was sprayed through a laboratory spray drier at 1.4 mL/min. The granules were evaluated for bulk density, tap density, Carr index, particle size distribution, surface morphology, thermal properties, and tableting properties. Bulk density of the granules decreased from 0.16 to 0.13 g/mL when the granules were prepared using medium- or high-molecular-weight chitosan compared with the low-molecular-weight chitosan. The relative proportion of chitosan also showed a significant effect on the bulk density. The granules prepared with 1 g of low-molecular-weight chitosan showed the minimum Carr index (11.1%) indicating the best flow properties among all five formulations. All three granules prepared with 1 g chitosan, irrespective of their molecular weight, showed excellent flow properties. Floating tablets prepared by direct compression of these granules with sodium bicarbonate showed 50% drug release between 30 and 35 min. In conclusion, the spray-dried granules prepared with chitosan and lactose showed excellent flow properties and were suitable for tableting.

Enzymatic and acidic degradation of high molecular weight dextran into low molecular weight and its characterizations using novel Diffusion-ordered NMR spectroscopy.

PubMed

Iqbal, Samina; Marchetti, Roberta; Aman, Afsheen; Silipo, Alba; Qader, Shah Ali Ul; Molinaro, Antonio

2017-10-01

Low molecular weight fractions were derived from native high molecular weight dextran produced by Leuconostoc mesenteroides KIBGE-IB26. Structural characterization of native and low molecular weight fractions obtained after acidic and enzymatic hydrolysis was done using FTIR and NMR spectroscopy. The molecular weight was estimated using Diffusion Ordered NMR spectroscopy. Native dextran (892kDa) is composed of α-(1→6) glycosidic linkage along with α-(1→3) branching. Major proportion of 528kDa dextran was obtained after prolong enzymatic hydrolysis however, an effective acidic treatment at pH-1.4 up to 02 and 04h of exposure resulted in the formation of 77kDa and 57kDa, respectively. The increment in pH from 1.4 to 1.8 lowered the hydrolysis efficiency and resulted in the formation of 270kDa dextran fraction. The results suggest that derived low molecular weight water soluble fractions can be utilized as a drug delivery carrier along with multiple application relating pharmaceutical industries. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of molecular weight of chemically sulfated citrus pectin fractions on their antithrombotic and bleeding effects.

PubMed

Cipriani, Thales R; Gracher, Ana Helena P; de Souza, Lauro M; Fonseca, Roberto J C; Belmiro, Celso L R; Gorin, Philip A J; Sassaki, Guilherme L; Iacomini, Marcello

2009-05-01

Evaluated were the anticoagulant and antithrombotic activities, and bleeding effect of two chemically sulfated polysaccharides, obtained from citric pectin, with different average molar masses. Both low-molecular-weight (Pec-LWS, 3,600 g/mol) and high-molecular-weight sulfated pectins (Pec-HWS, 12,000 g/mol) had essentially the same structure, consisting of a (1-->4)-linked alpha-D-GalpA chain with almost all its HO-2 and HO-3 groups substituted by sulfate. Both polysaccharides had anticoagulant activity in vitro, although Pec-HWS was a more potent antithrombotic agent in vivo, giving rise to total inhibition of venous thrombosis at a dose of 3.5 mg/kg body weight. Surprisingly, in contrast with heparin, Pec-HWS and Pec-LWS are able to directly inhibit alpha-thrombin and factor Xa by a mechanism independent of antithrombin (AT) and/or heparin co-factor II (HCII). Moreover, Pec-HWS provided a lower risk of bleeding than heparin at a dose of 100% effectiveness against venous thrombosis, indicating it to be a promising antithrombotic agent.

An improved correlation to predict molecular weight between crosslinks based on equilibrium degree of swelling of hydrogel networks.

PubMed

Jimenez-Vergara, Andrea C; Lewis, John; Hahn, Mariah S; Munoz-Pinto, Dany J

2018-04-01

Accurate characterization of hydrogel diffusional properties is of substantial importance for a range of biotechnological applications. The diffusional capacity of hydrogels has commonly been estimated using the average molecular weight between crosslinks (M c ), which is calculated based on the equilibrium degree of swelling. However, the existing correlation linking M c and equilibrium swelling fails to accurately reflect the diffusional properties of highly crosslinked hydrogel networks. Also, as demonstrated herein, the current model fails to accurately predict the diffusional properties of hydrogels when polymer concentration and molecular weight are varied simultaneously. To address these limitations, we evaluated the diffusional properties of 48 distinct hydrogel formulations using two different photoinitiator systems, employing molecular size exclusion as an alternative methodology to calculate average hydrogel mesh size. The resulting data were then utilized to develop a revised correlation between M c and hydrogel equilibrium swelling that substantially reduces the limitations associated with the current correlation. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1339-1348, 2018. © 2017 Wiley Periodicals, Inc.

Functional Comparison for Lipid Metabolism and Intestinal and Fecal Microflora Enzyme Activities between Low Molecular Weight Chitosan and Chitosan Oligosaccharide in High-Fat-Diet-Fed Rats.

PubMed

Chiu, Chen-Yuan; Feng, Shih-An; Liu, Shing-Hwa; Chiang, Meng-Tsan

2017-07-24

The present study investigated and compared the regulatory effects on the lipid-related metabolism and intestinal disaccharidase/fecal bacterial enzyme activities between low molecular weight chitosan and chitosan oligosaccharide in high-fat-diet-fed rats. Diet supplementation of low molecular weight chitosan showed greater efficiency than chitosan oligosaccharide in suppressing the increased weights in body and in liver and adipose tissues of high-fat-diet-fed rats. Supplementation of low molecular weight chitosan also showed a greater improvement than chitosan oligosaccharide in imbalance of plasma, hepatic, and fecal lipid profiles, and intestinal disaccharidase activities in high-fat-diet-fed rats. Moreover, both low molecular weight chitosan and chitosan oligosaccharide significantly decreased the fecal microflora mucinase and β-glucuronidase activities in high-fat-diet-fed rats. These results suggest that low molecular weight chitosan exerts a greater positive improvement than chitosan oligosaccharide in lipid metabolism and intestinal disaccharidase activity in high-fat-diet-induced obese rats.

Rheology modification with ring polymers

NASA Astrophysics Data System (ADS)

Vlassopoulos, Dimitris

It is now established that experimental unconcatenated ring polymers can be purified effectively by means of fractionation at the critical condition. For molecular weights well above the entanglement threshold, purified rings relax stress via power-law (with an exponent of about -0.4), sharply departing from their linear counterparts. Experimental results are in harmony with modeling predictions and simulations. Here, we present results from recent interdisciplinary efforts and discuss two challenges: (i) the nonlinear shear rheology of purified ring melts is also very different from that of unlinked chains. Whereas the latter exhibit features that can be explained, to a first approach, in the framework in the tube model, the former behave akin to unentangled chains with finite extensibility and exhibit much small deformation at steady state. (ii) blends of rings and linear polymers exhibit unique features in different regimes: The addition of minute amounts of linear chains drastically affects ring dynamics. This relates to ring purity and the ability of unlinked linear chains to thread rings. With the help of simulations, it is possible to rationalize the observed surprisingly slow viscoelastic relaxation, which is attributed to ring-linear and ring-ring penetrations. On the other hand, adding small amounts of rings to linear polymers of different molecular weights influences their linear and nonlinear rheology in an unprecedented way. The blend viscosity exceeds that of the slower component (linear) in this non-interacting mixture, and its dependencies on composition and molecular weight ratio are examined, whereas the role of molecular architecture is also addressed. Consequently, closing the ends of a linear chain can serve as a powerful means for molecular manipulation of its rheology. This presentation reflects collaborative efforts with S. Costanzo, Z-C. Yan, R. Pasquino, M. Kaliva, S. Kamble, Y. Jeong, P. Lutz, J. Allgaier, T. Chang, D. Talikis, V. Mavrantzas and M. Rubinstein.

Surface temperatures and glassy state investigations in tribology, part 4

NASA Technical Reports Server (NTRS)

Bair, S. S.; Winer, W. O.

1981-01-01

Measurements were made of the limiting shear stress for two naphthenic oils of differing molecular weight and three blends of the lower molecular weight oil and polyalkylmethacrylate polymers of differing molecular weight. The two base oils reached the same limiting shear stress for the same temperature and pressure. This was also true for all the polymer solutions although the polymer reduced the limiting shear stress by about 15 percent. It is shown that limiting stress is more a function of material type than viscosity or molecular weight. A new falling body viscometer was constructed to operate to 230 C and 0.6 GPa. Another viscometer was constructed to extend the pressure range to 1.1 GPa. A concentrated contact simulator was developed which allows recording of the traction force while the slide-roll ratio is continuously varied and the rolling speed is maintained essentially constant by a single drive motor. The configuration is that of a crowned roller against a disk. Measurement of lubricant minimum film thickness of elliptical EHD contacts of various aspect ratios were made by optical interferometry. The data collected were used to evaluate the Hamrock and Dowson minimum film thickness model over a range of contract ellipticity ratio where the major axis of the contact ellipse was aligned both parallel and perpendicular to the direction of motion. A statistical analysis of the measured film thickness data showed that on the average the experimental data were 30 percent greater than the film thickness predicted by the model. Preliminary development of the application of a scanning infrared radiation system to a tribo-system was completed.

Coalescence in PLA-PBAT blends under shear flow: Effects of blend preparation and PLA molecular weight

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

Nofar, M.; Heuzey, M. C.; Carreau, P. J., E-mail: pierre.carreau@polymtl.ca

Blends containing 75 wt. % of an amorphous polylactide (PLA) with two different molecular weights and 25 wt. % of a poly[(butylene adipate)-co-terephthalate] (PBAT) were prepared using either a Brabender batch mixer or a twin-screw extruder. These compounds were selected because blending PLA with PBAT can overcome various drawbacks of PLA such as its brittleness and processability limitations. In this study, we investigated the effects of varying the molecular weight of the PLA matrix and of two different mixing processes on the blend morphology and, further, on droplet coalescence during shearing. The rheological properties of these blends were investigated and the interfacialmore » properties were analyzed using the Palierne emulsion model. Droplet coalescence was investigated by applying shear flows of 0.05 and 0.20 s{sup −1} at a fixed strain of 60. Subsequently, small amplitude oscillatory shear tests were conducted to investigate changes in the viscoelastic properties. The morphology of the blends was also examined using scanning electron microscope (SEM) micrographs. It was observed that the PBAT droplets were much smaller when twin-screw extrusion was used for the blend preparation. Shearing at 0.05 s{sup −1} induced significant droplet coalescence in all blends, but coalescence and changes in the viscoelastic properties were much more pronounced for the PLA-PBAT blend based on a lower molecular weight PLA. The viscoelastic responses were also somehow affected by the thermal degradation of the PLA matrix during the experiments.« less

21 CFR 172.820 - Polyethylene glycol (mean molecular weight 200-9,500).

Code of Federal Regulations, 2010 CFR

2010-04-01

... ethylene oxide and water with a mean molecular weight of 200 to 9,500. (2) It contains no more than 0.2 percent total by weight of ethylene and diethylene glycols when tested by the analytical methods... the total ethylene and diethylene glycol content of polyethylene glycols having mean molecular weights...

Polycyclic aromatic hydrocarbons in the leaves of twelve plant species along an urbanization gradient in Shanghai, China.

PubMed

Liang, Jing; Fang, Hailan; Zhang, Taolin; Wang, Xingxiang

2017-04-01

Plants, particularly their leaves, play an important role in filtering both gas-phase and particle-phase polycyclic aromatic hydrocarbons (PAHs). However, many studies have focused on the accumulation and adsorption functions of plant leaves, possibly underestimating the effects that plants have on air quality. Therefore, eight tree species from different locations in Shanghai were selected to assess PAH filtering (via adsorption and capture) using washed and unwashed plant leaves. The differences in the total PAH contents in the washed leaves were constant for the different species across the different sampling sites. The PAH levels decreased in the following order: industrial areas > traffic areas > urban areas > background area. The PAH compositions in the different plant leaves were dominated by fluorene (Fle), phenanthrene (Phe), anthracene (Ant), chrysene (Chr), fluoranthene (Flu), and pyrene (Pyr); notably, Phe accounted for 49.4-76.7% of the total PAHs. By comparing the PAH contents in the washed leaves with the PAH contents in the unwashed leaves, Pittosporum tobira (P. tobira), Ginkgo biloba (G. biloba), and Platanus acerifolia (P. acerifolia) were found to be efficient species for adsorbing PAHs, while Osmanthus fragrans (O. fragrans), Magnolia grandiflora (M. grandiflora), and Prunus cerasifera Ehrh. (P. cerasifera Ehrh.) were efficient species for capturing PAHs. The efficiencies of the plant leaves for the removal of PAHs from air occurred in the order of low molecular weight > medium molecular weight > high molecular weight PAHs.

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

PubMed

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

2009-09-03

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.

Enhanced the performance of graphene oxide/polyimide hybrid membrane for CO2 separation by surface modification of graphene oxide using polyethylene glycol

NASA Astrophysics Data System (ADS)

Wu, Li-guang; Yang, Cai-hong; Wang, Ting; Zhang, Xue-yang

2018-05-01

Polyethylene glycol (PEG) with different molecular weights was first used to modify graphene oxide (GO) samples. Subsequently, polyimide (PI) hybrid membranes containing modified-GO were fabricated via in situ polymerization. The separation performance of these hybrid membranes was evaluated using permeation experiments for CO2 and N2 gases. The morphology characterization showed that PEG with suitable molecular weight could be successfully grafted on the GO surface. PEG modification altered the surface properties of GO and introduced defective structures onto GO surface. This caused strong surface polarity and high free volume of membranes containing PEG-modified GO, thereby improving the separation performance of membranes. The addition of PEG-GO with low molecular weight effectively increased gas diffusion through hybrid membranes. The hybrid membranes containing PEG-GO with large molecular weight had high solubility performance for CO2 gas due to the introduction of numerous polar groups into polymeric membranes. With the loading content of modified GO, the CO2 gas permeability of hybrid membranes initially increased but eventually decreased. The optimal content of modified GO in membranes reached 3.0 wt%. When too much PEG added (exceeding 30 g), some impurities formed on GO surface and some aggregates appeared in the resulting hybrid membrane, which depressed the membrane performance.

From Clothing to Laundry Water: Investigating the Fate of Phthalates, Brominated Flame Retardants, and Organophosphate Esters.

PubMed

Saini, Amandeep; Thaysen, Clara; Jantunen, Liisa; McQueen, Rachel H; Diamond, Miriam L

2016-09-06

The accumulation of phthalate esters, brominated flame retardants (BFRs) and organophosphate esters (OPEs) by clothing from indoor air and transfer via laundering to outdoors were investigated. Over 30 days cotton and polyester fabrics accumulated 3475 and 1950 ng/dm(2) ∑5phthalates, 65 and 78 ng/dm(2) ∑10BFRs, and 1200 and 310 ng/dm(2) ∑8OPEs, respectively. Planar surface area concentrations of OPEs and low molecular weight phthalates were significantly greater in cotton than polyester and similar for BFRs and high molecular weight phthalates. This difference was significantly and inversely correlated with KOW, suggesting greater sorption of polar compounds to polar cotton. Chemical release from cotton and polyester to laundry water was >80% of aliphatic OPEs (log KOW < 4), < 50% of OPEs with an aromatic structure, 50-100% of low molecular weight phthalates (log KOW 4-6), and < detection-35% of higher molecular weight phthalates (log KOW > 8) and BFRs (log KOW > 6). These results support the hypothesis that clothing acts an efficient conveyer of soluble semivolatile organic compounds (SVOCs) from indoors to outdoors through accumulation from air and then release during laundering. Clothes drying could as well contribute to the release of chemicals emitted by electric dryers. The results also have implications for dermal exposure.

Comparative proteomic analysis of male and female venoms from the Cuban scorpion Rhopalurus junceus.

PubMed

Rodríguez-Ravelo, Rodolfo; Batista, Cesar V F; Coronas, Fredy I V; Zamudio, Fernando Z; Hernández-Orihuela, Lorena; Espinosa-López, Georgina; Ruiz-Urquiola, Ariel; Possani, Lourival D

2015-12-01

A complete mass spectrometry analysis of venom components from male and female scorpions of the species Rhophalurus junceus of Cuba is reported. In the order of 200 individual molecular masses were identified in both venoms, from which 63 are identical in male and females genders. It means that a significant difference of venom components exists between individuals of different sexes, but the most abundant components are present in both sexes. The relative abundance of identical components is different among the genders. Three well defined groups of different peptides were separated and identified. The first group corresponds to peptides with molecular masses of 1000-2000 Da; the second to peptides with 3500-4500 Da molecular weight, and the third with 6500-8000 Da molecular weights. A total of 86 peptides rich in disulfide bridges were found in the venoms, 27 with three disulfide bridges and 59 with four disulfide bridges. LC-MS/MS analysis allowed the identification and amino acid sequence determination of 31 novel peptides in male venom. Two new putative K(+)-channel peptides were sequences by Edman degradation. They contain 37 amino acid residues, packed by three disulfide bridges and were assigned the systematic numbers: α-KTx 1.18 and α-KTx 2.15. Copyright © 2015 Elsevier Ltd. All rights reserved.

Weathering trend characterization of medium-molecular weight polycyclic aromatic disulfur heterocycles by Fourier transform ion cyclotron resonance mass spectrometry.

PubMed

Hegazi, Abdelrahman H; Fathalla, Eiman M; Andersson, Jan T

2014-09-01

Different weathering factors act to change petroleum composition once it is spilled into the environment. n-Alkanes, biomarkers, low-molecular weight polyaromatic hydrocarbons and sulfur heterocycles compositional changing in the environment have been extensively studied by different researchers and many parameters have been used for oil source identification and monitoring of weathering and biological degradation processes. In this work, we studied the fate of medium-molecular weight polycyclic aromatic disulfur heterocycles (PAS2Hs), up to ca. 900Da, of artificially weathered Flotta North Sea crude oil by ultra high-resolution Fourier transform ion cyclotron resonance mass spectrometry. It was found that PAS2Hs in studied crude oil having double bond equivalents (DBE) from 5 to 8 with a mass range from ca 316 to 582Da were less influenced even after six months artificial weathering experiment. However, compounds having DBEs 12, 11 and 10 were depleted after two, four and six months weathering, respectively. In addition, DBE 9 series was more susceptible to weathering than those of DBE 7 and 8. Copyright © 2014 Elsevier Ltd. All rights reserved.

Modified pectic polysaccharide from turmeric (Curcuma longa): A potent dietary component against gastric ulcer.

PubMed

Harsha, Mysore R; Chandra Prakash, Serkad V; Dharmesh, Shylaja M

2016-03-15

Native, intact (TrPP) and modified, low-molecular-weight (MTrPP) forms of pectic polysaccharides isolated from turmeric were evaluated for ulcer-preventive potentials in in vitro and in vivo models. Data indicated that MTrPP possessed significantly better ulcer-preventive property than TrPP; inhibiting ulcer scores up to 85%. Results were substantiated by effective muco-protection, H(+),K(+)-ATPase down-regulation, inhibition of H. pylori growth/adherence, higher antioxidant/cytoprotective mechanisms. Structural data indicated TrPP and MTrPP differ in their molecular weights and structural characteristics with different sugar compositions and side chain ratios. MTrPP was rich in galacturonic acid (687mg/g; TrPP-544mg/g) and galactose (52.9%; TrPP-21.7%). Results were substantiated by NMR/FTIR data indicating the presence of homogalacturonan and rhamnogalacturonam-I containing galactans. By virtue of binding to inflammatory marker (galectin-3), galactans may reduce inflammation induced ulcerations. The low molecular weight of MTrPP (155kDa; TrPP-13kDa) may increase its bioavailability than TrPP, thus MTrPP may possess higher antiulcer potential. Copyright © 2015 Elsevier Ltd. All rights reserved.

Di- or polysulphide-bound biomarkers in sulphur-rich geomacromolecules as revealed by selective chemolysis

NASA Astrophysics Data System (ADS)

Kohnen, Math E. l.; Sinninghe Damsté, Jaap S.; Kock-van Dalen, A. c.; Jan, W. De Leeuw

1991-05-01

Three types of sulphur-rich high-molecular-weight material in the alkylsulphide, the polar, and the asphaltene fractions isolated from the bitumen of an immature bituminous shale from the Vena del Gesso basin (Italy) were desulphurised using Raney Ni and were treated with MeLi/MeI, a chemical degradation method which cleaves selectively and quantitatively di- or polysulphide linkages. The products formed were characterised by gas chromatography-mass spectrometry. Raney Ni desulphurisation revealed that these S-rich macromolecules are in substantial part composed of sulphur-linked biomarkers with linear, branched, isoprenoid, steroid, hopanoid, and carotenoid carbon skeletons. MeLi/Mel treatment provided evidence that a major part of the total amount of macromolecularly bound biomarkers are linked via di- or polysulphide moieties to the macromolecular network. Since the di- or polysulphide linkages are attached at specific positions of the bound biomarkers it is proposed that they are formed by intermolecular incorporation reactions of HS x- into low-molecular-weight functionalised biological lipids during early diagenesis. The different properties (solubility and molecular weight) of the sulphur-rich macromolecules in the alkylsulphide, the resin, and the asphaltene fractions can be explained simply by differences in degree of sulphur cross-linking.

Interpretation of screen factor measurements

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

Lim, T.; Uhl, J.T.; Prud'Homme, R.K.

1983-08-01

Screen viscometer measurements give different information about polymer molecular weight and molecular weight distribution than intrinsic viscosity or relative viscosity measurements. This study shows that conventional screen viscometers measure elongation flow properties of solutions, and that for flexible polymers such as polyacrylamides, a sharp transition in conformation from a coiled to a stretched state is observed, which occurs at a Deborah number of 0.5. Conventional screen viscometers operate just above this critical Deborah number. Evidence for this transition in polymer conformation comes from measurements on a modified screen viscometer, from extensive work by Durst and Interhal on the sudden pressuremore » jumps during flow of polyacrylamide solutions through porous media, and from polymer kinetic theory modeling of molecular deformation in flow. ll references.« less

Structural Characterization of the Low-Molecular-Weight Heparin Dalteparin by Combining Different Analytical Strategies.

PubMed

Bisio, Antonella; Urso, Elena; Guerrini, Marco; de Wit, Pauline; Torri, Giangiacomo; Naggi, Annamaria

2017-06-24

A number of low molecular weight heparin (LMWH) products are available for clinical use and although all share a similar mechanism of action, they are classified as distinct drugs because of the different depolymerisation processes of the native heparin resulting in substantial pharmacokinetic and pharmacodynamics differences. While enoxaparin has been extensively investigated, little information is available regarding the LMWH dalteparin. The present study is focused on the detailed structural characterization of Fragmin ® by LC-MS and NMR applied both to the whole drug and to its enzymatic products. For a more in-depth approach, size homogeneous octasaccharide and decasaccharide components together with their fractions endowed with high or no affinity toward antithrombin were also isolated and their structural profiles characterized. The combination of different analytical strategies here described represents a useful tool for the assessment of batch-to-batch structural variability and for comparative evaluation of structural features of biosimilar products.

Non-anticoagulant effects of low molecular weight heparins in inflammatory disorders: A review.

PubMed

Yan, Yishu; Ji, Yang; Su, Nan; Mei, Xiang; Wang, Yi; Du, Shanshan; Zhu, Wenming; Zhang, Chong; Lu, Yuan; Xing, Xin-Hui

2017-03-15

Low molecular weight heparins (LMWHs) are produced by chemical or enzymatic depolymerization of unfractionated heparin (UFH). Besides their well-known anticoagulant effects, LMWHs have also been reported to exhibit numerous anti-inflammatory properties. Previous studies have, however, shown that different production processes result in unique structural characteristics of LMWHs. The structural variations may help explain the different therapeutic spectrums in disease treatment for non-anticoagulant effects. In the present review, we summarize major advances in understanding and exploiting the anti-inflammatory disorder activities of LMWHs, based on mechanistic studies, preclinical experiments and clinical trials. We highlight differences in these activities of commercially available LMWHs produced using different manufacturing processes. We stress the importance of structure-activity relationship (SAR) studies on the non-anticoagulant effects of LMWHs and discuss strategies for exploring new clinical indications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Combustion of High Molecular Weight Hydrocarbon Fuels and JP-8 at Moderate Pressures

DTIC Science & Technology

2016-07-26

SECURITY CLASSIFICATION OF: The objective of this research is to characterize combustion of high molecular weight hydrocarbon fuels and jet- fuels (in...Unlimited UU UU UU UU 26-07-2016 1-May-2012 30-Apr-2016 Final Report: Combustion of High Molecular Weight Hydrocarbon Fuels and JP-8 at Moderate...Report: Combustion of High Molecular Weight Hydrocarbon Fuels and JP-8 at Moderate Pressures (Research Area 1: Mechanical Sciences) Report Title The

Application of the weibull distribution function to the molecular weight distribution of cellulose

Treesearch

A. Broido; Hsiukang Yow

1977-01-01

The molecular weight distribution of a linear homologous polymer is usually obtained empirically for any particular sample. Sample-to-sample comparisons are made in terms of the weight- or number-average molecular weights and graphic displays of the distribution curves. Such treatment generally precludes data interpretations in which a distribution can be described in...

Isoleucine epimerization in the high-molecular-weight fraction of pleistocene Arctica

NASA Astrophysics Data System (ADS)

Kaufman, Darrell S.; Sejrup, Hans-Petter

The extent of amino acid racemization, as traditionally determined in the entire (total acid hydrolysate) pool of amino acids comprising the organic remains of fossils, is a function of the integrated effects of a complex diagenetic reaction network. We investigated the possibility that some of the complications involved in protein diagenesis might be circumvented by isolating one component of the reaction network and studying the extent of racemization in that fraction alone. We used gel-filtration to extract the high-molecular-weight (HMW) fraction of proteinaceous matter from fossil and modem molluscan shells. This fraction contains the largest (ca. > 15,000 MW), most-pristine macromolecules and has been less affected by diagenesis than the more-degraded, lower molecular-weight fractions. Variations in the extent of racemization (isoleucine epimerization; alle/Ile) measured in the HMW fraction of subsamples taken along cross sections of Arctica shells from two interglacial sites, Bø and Fjøsanger, southwestern Norway, are within the range of analytical uncertainty [coefficient of variation (cv) = 5-8%], despite the strong gradient (cv = 20-24%) in alle/Ile of the total amino acid population. Because there is no age difference across a shell, this finding supports the idea that the HMW fraction contains more geochronologically reliable proteinaceous matter than the total amino acid pool. Weighted mean alle/Ile ratios in the HMW fraction of aliquots of powdered sample from the two shells overlap at ± 1σ, despite significantly different alle/Ile ratios in the total amino acid population of some shells from the two sites. The difference in alle/Ile ratios in the total population is attributed to a greater proportion of low-molecular-weight (ca. 300 MW), and hence, extensively epimerized molecules measured in gel-filtered samples from the Fjøsanger shell. Because the rate of epimerization in the HMW fraction is much lower than in the total population, the temporal resolution of the HMW technique is limited, particularly at these high-latitude sites. Therefore, we cannot use the aIle/Ile HMW data to exclude the possibility that the two sites are significantly different ages. Analyses of shells ranging in age from late Pliocene to Holocene indicate that reaction rate in the HMW fraction is about one-fifth the rate in the total amino acid population, although the difference is expected to decrease with increasing aIle/Ile.

Supplementing formula-fed piglets with a low molecular weight fraction of bovine colostrum whey results in an improved intestinal barrier.

PubMed

De Vos, M; Huygelen, V; Van Raemdonck, G; Willemen, S; Fransen, E; Van Ostade, X; Casteleyn, C; Van Cruchten, S; Van Ginneken, C

2014-08-01

To test the hypothesis that a low molecular weight fraction of colostral whey could affect the morphology and barrier function of the small intestine, 30 3-d-old piglets (normal or low birth weight) were suckled (n = 5), artificially fed with milk formula (n = 5), or artificially fed with milk formula with a low molecular weight fraction of colostral whey (n = 5) until 10 d of age. The small intestine was sampled for histology (haematoxylin and eosin stain; anti-KI67 immunohistochemistry) and enzyme activities (aminopeptidase A, aminopeptidase N, dipeptidylpeptidase IV, lactase, maltase, and sucrase). In addition, intestinal permeability was evaluated via a dual sugar absorption test and via the measurement of occludin abundance. Artificially feeding of piglets reduced final BW (P < 0.001), villus height (P < 0.001), lactase (P < 0.001), and dipeptidylpeptidase IV activities (P < 0.07), whereas crypt depth (P < 0.001) was increased. No difference was observed with regard to the permeability measurements when comparing artificially fed with naturally suckling piglets. Supplementing piglets with the colostral whey fraction did not affect BW, enzyme activities, or the outcome of the dual sugar absorption test. On the contrary, the small intestines of supplemented piglets had even shorter villi (P = 0.001) than unsupplemented piglets and contained more occludin (P = 0.002). In conclusion, at 10 d of age, no differences regarding intestinal morphology and permeability measurements were observed between the 2 BW categories. In both weight categories, the colostral whey fraction affected the morphology of the small intestine but did not improve the growth performances or the in vivo permeability. These findings should be acknowledged when developing formulated milk for neonatal animals with the aim of improving the performance of low birth weight piglets.

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.

Determination of the molecular weight of poly(ethylene glycol) in biological samples by reversed-phase LC-MS with in-source fragmentation.

PubMed

Warrack, Bethanne M; Redding, Brian P; Chen, Guodong; Bolgar, Mark S

2013-05-01

PEGylation has been widely used to improve the biopharmaceutical properties of therapeutic proteins and peptides. Previous studies have used multiple analytical techniques to determine the fate of both the therapeutic molecule and unconjugated poly(ethylene glycol) (PEG) after drug administration. A straightforward strategy utilizing liquid chromatography-mass spectrometry (LC-MS) to characterize high-molecular weight PEG in biologic matrices without a need for complex sample preparation is presented. The method is capable of determining whether high-MW PEG is cleaved in vivo to lower-molecular weight PEG species. Reversed-phase chromatographic separation is used to take advantage of the retention principles of polymeric materials whereby elution order correlates with PEG molecular weight. In-source collision-induced dissociation (CID) combined with selected reaction monitoring (SRM) or selected ion monitoring (SIM) mass spectrometry (MS) is then used to monitor characteristic PEG fragment ions in biological samples. MS provides high sensitivity and specificity for PEG and the observed retention times in reversed-phase LC enable estimation of molecular weight. This method was successfully used to characterize PEG molecular weight in mouse serum samples. No change in molecular weight was observed for 48 h after dosing.

Metabolism of AGEs – Bacterial AGEs Are Degraded by Metallo-Proteases

PubMed Central

Cohen-Or, Ifat; Katz, Chen; Ron, Eliora Z.

2013-01-01

Advanced Glycation End Products (AGEs) are the final products of non-enzymatic protein glycation that results in loss of protein structure and function. We have previously shown that in E. coli AGEs are continually formed as high-molecular weight protein complexes. Moreover, we showed that AGEs are removed from the cells by an active, ATP-dependent secretion and that these secreted molecules have low molecular weight. Taken together, these results indicate that E. coli contains a fraction of low molecular weight AGEs, in addition to the high-molecular weight AGEs. Here we show that the low-molecular weight AGEs originate from high-molecular weight AGEs by proteolytic degradation. Results of in-vitro and in vivo experiments indicated that this degradation is carried out not by the major ATP-dependent proteases that are responsible for the main part of bacterial protein quality control but by an alternative metal-dependent proteolysis. This proteolytic reaction is essential for the further secretion of AGEs from the cells. As the biochemical reactions involving AGEs are not yet understood, the implication of a metalloprotease in breakdown of high molecular weight AGEs and their secretion constitutes an important step in the understanding of AGEs metabolism. PMID:24130678

Metabolism of AGEs--bacterial AGEs are degraded by metallo-proteases.

PubMed

Cohen-Or, Ifat; Katz, Chen; Ron, Eliora Z

2013-01-01

Advanced Glycation End Products (AGEs) are the final products of non-enzymatic protein glycation that results in loss of protein structure and function. We have previously shown that in E. coli AGEs are continually formed as high-molecular weight protein complexes. Moreover, we showed that AGEs are removed from the cells by an active, ATP-dependent secretion and that these secreted molecules have low molecular weight. Taken together, these results indicate that E. coli contains a fraction of low molecular weight AGEs, in addition to the high-molecular weight AGEs. Here we show that the low-molecular weight AGEs originate from high-molecular weight AGEs by proteolytic degradation. Results of in-vitro and in vivo experiments indicated that this degradation is carried out not by the major ATP-dependent proteases that are responsible for the main part of bacterial protein quality control but by an alternative metal-dependent proteolysis. This proteolytic reaction is essential for the further secretion of AGEs from the cells. As the biochemical reactions involving AGEs are not yet understood, the implication of a metalloprotease in breakdown of high molecular weight AGEs and their secretion constitutes an important step in the understanding of AGEs metabolism.

Improving the accuracy of hyaluronic acid molecular weight estimation by conventional size exclusion chromatography.

PubMed

Shanmuga Doss, Sreeja; Bhatt, Nirav Pravinbhai; Jayaraman, Guhan

2017-08-15

There is an unreasonably high variation in the literature reports on molecular weight of hyaluronic acid (HA) estimated using conventional size exclusion chromatography (SEC). This variation is most likely due to errors in estimation. Working with commercially available HA molecular weight standards, this work examines the extent of error in molecular weight estimation due to two factors: use of non-HA based calibration and concentration of sample injected into the SEC column. We develop a multivariate regression correlation to correct for concentration effect. Our analysis showed that, SEC calibration based on non-HA standards like polyethylene oxide and pullulan led to approximately 2 and 10 times overestimation, respectively, when compared to HA-based calibration. Further, we found that injected sample concentration has an effect on molecular weight estimation. Even at 1g/l injected sample concentration, HA molecular weight standards of 0.7 and 1.64MDa showed appreciable underestimation of 11-24%. The multivariate correlation developed was found to reduce error in estimations at 1g/l to <4%. The correlation was also successfully applied to accurately estimate the molecular weight of HA produced by a recombinant Lactococcus lactis fermentation. Copyright © 2017 Elsevier B.V. All rights reserved.

How Molecular Structure Affects Mechanical Properties of an Advanced Polymer

NASA Technical Reports Server (NTRS)

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

2000-01-01

density was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength all as a function of molecular weight and test temperature were determined. For the uncrosslinked SI material, 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. For the crosslinked PETI-SI material, it was shown that the effect of crosslinking significantly enhances the mechanical performance of the low molecular weight material; comparable to that exhibited by the high molecular weight material.

Enhancement of mechanical properties of 3D printed hydroxyapatite by combined low and high molecular weight polycaprolactone sequential infiltration.

PubMed

Suwanprateeb, Jintamai; Thammarakcharoen, Faungchat; Hobang, Nattapat

2016-11-01

A new infiltration technique using a combination of low and high molecular weight polycaprolactone (PCL) in sequence was developed as a mean to improve the mechanical properties of three dimensional printed hydroxyapatite (HA). It was observed that using either high (M n ~80,000) or low (M n ~10,000) molecular weight infiltration could only increase the flexural modulus compared to non-infiltrated HA, but did not affect strength, strain at break and energy at break. In contrast, a combination of low and high molecular infiltration in sequence increased the flexural modulus, strength and energy at break compared to those of non-infiltrated HA or infiltrated by high or low molecular weight PCL alone. This overall enhancement was found to be attributed to the densification of low molecular weight PCL and the reinforcement of high molecular PCL concurrently. The combined low and high molecular weight infiltration in sequence also maintained high osteoblast proliferation and differentiation of the composites at the similar level of the HA. Densification was a dominant mechanism for the change in modulus with porosity and density of the infiltrated HA/PCL composites. However, both densification and the reinforcing performance of the infiltration phase were crucial for strength and toughening enhancement of the composites possibly by the defect healing and stress shielding mechanisms. The sequence of using low molecular weight infiltration and followed by high molecular infiltration was seen to provide the greatest flexural properties and highest cells proliferation and differentiation capabilities.

Fluorescence fingerprints and Cu2+-complexing ability of individual molecular size fractions in soil- and waste-borne DOM.

PubMed

Knoth de Zarruk, K; Scholer, G; Dudal, Y

2007-09-01

Land spreading of organic materials introduces large amounts of dissolved organic matter (DOM) into the soil. DOM has the ability to form stable complexes with heavy metals and can facilitate their transport towards the groundwater. The effects on soil processes are difficult to assess, because different DOM components might react differently towards metal ions. The objective of this study was to investigate the fluorescence signature and the Cu2+-binding capacity of individual molecular size fractions of DOM from various sources. DOM extracted from leaf compost, chicken manure, sugar cane vinasse and a fulvic hypercalcaric cambisol was fractionated by the means of dialysis into four molecular size classes: MW<500, 50012000-14000 Da. Vinasse and leaf compost contained around 80% and 70%, respectively, of the total organic carbon in the fractions with low molecular weight (MW<3500 Da); in chicken manure and soil these fractions accounted for 40% and 50% only. Fluorescence was highest in the fraction MW>12000 Da for leaf compost, chicken manure and soil. The opposite result was obtained for vinasse, where the fractions with low molecular weight showed highest fluorescence intensities, distinguishing it from all other samples. Vinasse showed the greatest ability to bind Cu2+ with a resulting complex concentration of 6.31mgl(-1) while in contact with an excess of Cu2+. Leaf compost, soil and chicken manure followed with 2.69, 1.12, and 0.85mgl(-1), respectively. Within vinasse, the fraction MW<500 Da was able to form the most DOM-Cu complexes, indicating the importance of low molecular weight fractions in metal binding.

Rare expression of high-molecular-weight cytokeratin in adenocarcinoma of the prostate gland: a study of 100 cases of metastatic and locally advanced prostate cancer.

PubMed

Yang, X J; Lecksell, K; Gaudin, P; Epstein, J I

1999-02-01

Immunohistochemistry with antibodies for high-molecular-weight cytokeratin labels basal cells and is used as an ancillary study in diagnosing prostate carcinoma, which reportedly lacks expression of high-molecular-weight cytokeratin. A recent report questioned the specificity of this marker, describing immunopositivity for high-molecular-weight cytokeratin in a small series of metastatic prostate cancer. We have also noted rare cases of prostate lesions on biopsy with typical histological features of adenocarcinoma showing immunopositivity for high-molecular-weight cytokeratin, either in tumor cells or in patchy cells with the morphology of basal cells. In some of these cases, it was difficult to distinguish cancer from out-pouching of high-grade prostatic intraepithelial neoplasia. To investigate whether prostate cancer cells express high-molecular-weight cytokeratin, we studied 100 cases of metastatic prostate carcinoma and 10 cases of prostate cancer invading the seminal vesicles from surgical specimens. Metastatic sites included regional lymph nodes (n = 67), bone (n = 19), and miscellaneous (n = 14). Cases with any positivity for high-molecular-weight cytokeratin antibody (34betaE12) were verified as being of prostatic origin with immunohistochemistry for prostate-specific antigen and prostate-specific acid phosphatase. Only four cases were detected positive for high-molecular-weight cytokeratin. In two cases (one metastasis, one seminal vesicle invasion) there was weakly diffuse positivity above background level. Two metastases in lymph nodes showed scattered strong staining of clusters of tumor cells, which represented <0.2% of tumor cells in the metastatic deposits. These positive cells did not have the morphology of basal cells. We conclude that prostate cancer, even high grade, only rarely expresses high-molecular-weight cytokeratin. This marker remains a very useful adjunct in the diagnosis of prostate cancer.

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

Code of Federal Regulations, 2010 CFR

2010-04-01

... conditions: (a) The additive is an addition 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... ethylene and diethylene glycols if its mean molecular weight is below 350, when tested by the analytical...

A study on the quality control of slow burning polyester

NASA Astrophysics Data System (ADS)

Chen, Bin; Wang, Yinglei; Yan, Zhengfeng; Yu, Tao

2018-04-01

In this paper, the influence of the alcohol/acid mole ratio, reaction temperature, warm-up mode, end-capping, vacuity to the quality of slow burning polyester was studied. The hydroxyl value will increase when the alcohol/acid mole ratio increase, but the acid value and molecular weight will decrease. The molecular weight and molecular weight distribution of the polyester consistent with the designed one can be obtained by stepped heating up. Monobasic alcohol end-capping can be used to control the molecular weight effectively and reduce acid value. Stripping process narrow the molecular weight distribution and reduce the hydroxyl value. Decompression is in favor of the decrease of acid value and increase of the reaction speed to get qualified production.

Highly Conductive Ionic-Liquid Gels Prepared with Orthogonal Double Networks of a Low-Molecular-Weight Gelator and Cross-Linked Polymer.

PubMed

Kataoka, Toshikazu; Ishioka, Yumi; Mizuhata, Minoru; Minami, Hideto; Maruyama, Tatsuo

2015-10-21

We prepared a heterogeneous double-network (DN) ionogel containing a low-molecular-weight gelator network and a polymer network that can exhibit high ionic conductivity and high mechanical strength. An imidazolium-based ionic liquid was first gelated by the molecular self-assembly of a low-molecular-weight gelator (benzenetricarboxamide derivative), and methyl methacrylate was polymerized with a cross-linker to form a cross-linked poly(methyl methacrylate) (PMMA) network within the ionogel. Microscopic observation and calorimetric measurement revealed that the fibrous network of the low-molecular-weight gelator was maintained in the DN ionogel. The PMMA network strengthened the ionogel of the low-molecular-weight gelator and allowed us to handle the ionogel using tweezers. The orthogonal DNs produced ionogels with a broad range of storage elastic moduli. DN ionogels with low PMMA concentrations exhibited high ionic conductivity that was comparable to that of a neat ionic liquid. The present study demonstrates that the ionic conductivities of the DN and single-network, low-molecular-weight gelator or polymer ionogels strongly depended on their storage elastic moduli.

Controllable production of low molecular weight heparins by combinations of heparinase I/II/III.

PubMed

Wu, Jingjun; Zhang, Chong; Mei, Xiang; Li, Ye; Xing, Xin-Hui

2014-01-30

Enzymatic depolymerization of heparin by heparinases is promising for production of low molecular weight heparins (LMWHs) as anticoagulants, due to its mild reaction conditions and high selectivity. Here, different heparinase combinations were used to depolymerize heparin. Heparinase I and heparinase II can depolymerize heparin more efficiently than heparinase III, respectively, but heparinase III was the best able to protect the anticoagulant activities of LMWHs. Heparinase III and heparinase I/II combinations were able to efficiently depolymerize heparin to LMWHs with higher anticoagulant activity than the LMWHs produced by the respective heparinase I and heparinase II. HepIII and HepI is the best combination for maintaining high anti-IIa activity (75.7 ± 4.21 IU/mg) at the same Mw value. Furthermore, considering both the changes in molecular weight and anticoagulant activity, the action patterns of heparinase I and heparinase II were found not to follow the exolytic and processive depolymerizing mechanism from the reducing end of heparin. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Ascorbate-glutathione-α-tocopherol Triad in Abiotic Stress Response

PubMed Central

Szarka, András; Tomasskovics, Bálint; Bánhegyi, Gábor

2012-01-01

The life of any living organism can be defined as a hurdle due to different kind of stresses. As with all living organisms, plants are exposed to various abiotic stresses, such as drought, salinity, extreme temperatures and chemical toxicity. These primary stresses are often interconnected, and lead to the overproduction of reactive oxygen species (ROS) in plants, which are highly reactive and toxic and cause damage to proteins, lipids, carbohydrates and DNA, which ultimately results in oxidative stress. Stress-induced ROS accumulation is counteracted by enzymatic antioxidant systems and non-enzymatic low molecular weight metabolites, such as ascorbate, glutathione and α-tocopherol. The above mentioned low molecular weight antioxidants are also capable of chelating metal ions, reducing thus their catalytic activity to form ROS and also scavenge them. Hence, in plant cells, this triad of low molecular weight antioxidants (ascorbate, glutathione and α-tocopherol) form an important part of abiotic stress response. In this work we are presenting a review of abiotic stress responses connected to these antioxidants. PMID:22605990

Synthesis of Well-defined Amphiphilic Block Copolymers by Organotellurium-Mediated Living Radical Polymerization (TERP).

PubMed

Kumar, Santosh; Changez, Mohammad; Murthy, C N; Yamago, Shigeru; Lee, Jae-Suk

2011-10-04

Low-molecular weight amphiphilic diblock copolymers, polystyrene-block-poly (2-vinylpyridine) (PS-b-P2VP), and (P2VP-b-PS) with different block ratios were synthesized for the first time via organotellurium-mediated living radical polymerization (TERP). For both the homo- and block copolymerizations, good agreement between the theoretical, and experimental molecular weights was found with nearly 100% yield in every case. The molecular weight distribution for all the samples ranged between 1.10 and 1.24, which is well below the theoretical lower limit of 1.50 for a conventional free radical polymerization. Furthermore, a very simple approach to producing highly dense arrays of titania nanoparticles (TiO2 ) is presented using a site-selective reaction of titanium tetraisopropoxide within the P2VP domains of micellar film of P2VP-b-PS in toluene through the sol-gel method. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hyaluronic Acid Graft Copolymers with Cleavable Arms as Potential Intravitreal Drug Delivery Vehicles.

PubMed

Borke, Tina; Najberg, Mathie; Ilina, Polina; Bhattacharya, Madhushree; Urtti, Arto; Tenhu, Heikki; Hietala, Sami

2018-01-01

Treatment of retinal diseases currently demands frequent intravitreal injections due to rapid clearance of the therapeutics. The use of high molecular weight polymers can extend the residence time in the vitreous and prolong the injection intervals. This study reports a water soluble graft copolymer as a potential vehicle for sustained intravitreal drug delivery. The copolymer features a high molecular weight hyaluronic acid (HA) backbone and poly(glyceryl glycerol) (PGG) side chains attached via hydrolysable ester linkers. PGG, a polyether with 1,2-diol groups in every repeating unit available for conjugation, serves as a detachable carrier. The influence of synthesis conditions and incubation in physiological media on the molecular weight of HA is studied. The cleavage of the PGG grafts from the HA backbone is quantified and polymer-from-polymer release kinetics are determined. The biocompatibility of the materials is tested in different cell cultures. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rapid preparation of functional polysaccharides from Pyropia yezoensis by microwave-assistant rapid enzyme digest system.

PubMed

Lee, Ji-Hyeok; Kim, Hyung-Ho; Ko, Ju-Young; Jang, Jun-Ho; Kim, Gwang-Hoon; Lee, Jung-Suck; Nah, Jae-Woon; Jeon, You-Jin

2016-11-20

This study describes a simple preparation of functional polysaccharides from Pyropia yezoensis using a microwave-assistant rapid enzyme digest system (MAREDS) with various carbohydrases, and evaluates their antioxidative effects. Polysaccharide hydrolysates were prepared using MAREDS under different hydrolytic conditions of the carbohydrases and microwave powers. Polysaccharides less than 10kDa (Low molecular weight polysaccharides, LMWP, ≤10kDa) were efficiently obtained using an ultrafiltration (molecular weight cut-off of 10kDa). MAREDS increases AMG activation via an increased degree of hydrolysis; the best AMG hydrolysate was prepared using a 10:1 ratio of substrate to enzyme for 2h in MAREDS with 400W. LMWP consisted of galactose (27.3%), glucose (64.5%), and mannose (8.3%) from the AMG hydrolysate had stronger antioxidant effects than the high molecular weight polysaccharides (>10kDa). We rapidly prepared functional LMWPs by using MAREDS with carbohydrases, and suggest that LMWP might be potentially a valuable algal polysaccharide antioxidant. Copyright © 2016 Elsevier Ltd. All rights reserved.

[Comparative characteristics of biosynthesis of polyhydroxybutyrate from methanol by Methylobacteria extorquens G10 and Methyloligella halotolerans C2].

PubMed

Poroshina, M N; Doronina, N V; Ezhov, V A; Trotsenko, Iu A

2014-01-01

The biosynthesis of polyhydroxybutyrate by Methylobacteria extorquens G10 and Methyloligella halotolerans C2 via the serine pathway of C1 metabolism was comparatively studied. Nitrogen limitation stimulated synthesis of the biopolymer in both cultures. It was shown that, despite the similarity of the pathways of methanol metabolism and those of polyhydroxybutyrate biosynthesis, the methylobacteria synthesized polymers of different molecular weights. In the case of M. extorquens G10, an increase in the content of the residual nitrogen in the culture medium was found to result in a reduction of the molecular weight of the polymer from 250 to 85 kDa, whereas M. halotolerans C2 synthesized a polymer of high molecular weight (approximately 3000 kDa) regardless of the residual content of the nitrogen source. It was established that the examined methylobacteria can utilize not only pure methanol but also a crude one, a feature that made it possible to significantly reduce the cost of the resulting polyhydroxybutyrate.

Novel strategies to construct complex synthetic vectors to produce DNA molecular weight standards.

PubMed

Chen, Zhe; Wu, Jianbing; Li, Xiaojuan; Ye, Chunjiang; Wenxing, He

2009-05-01

DNA molecular weight standards (DNA markers, nucleic acid ladders) are commonly used in molecular biology laboratories as references to estimate the size of various DNA samples in electrophoresis process. One method of DNA marker production is digestion of synthetic vectors harboring multiple DNA fragments of known sizes by restriction enzymes. In this article, we described three novel strategies-sequential DNA fragment ligation, screening of ligation products by polymerase chain reaction (PCR) with end primers, and "small fragment accumulation"-for constructing complex synthetic vectors and minimizing the mass differences between DNA fragments produced from restrictive digestion of synthetic vectors. The strategy could be applied to construct various complex synthetic vectors to produce any type of low-range DNA markers, usually available commercially. In addition, the strategy is useful for single-step ligation of multiple DNA fragments for construction of complex synthetic vectors and other applications in molecular biology field.

21 CFR 172.820 - Polyethylene glycol (mean molecular weight 200-9,500).

Code of Federal Regulations, 2011 CFR

2011-04-01

... the total ethylene and diethylene glycol content of polyethylene glycols having mean molecular weights... and diethylene glycol content of polyethylene glycols having mean molecular weights below 450. Analytical Method ethylene glycol and diethylene glycol content of polyethylene glycols The analytical method...

Effects of Hofmeister Anions on the LCST of PNIPAM as a Function of Molecular Weight

PubMed Central

Zhang, Yanjie; Furyk, Steven; Sagle, Laura B.; Cho, Younhee; Bergbreiter, David E.; Cremer, Paul S.

2008-01-01

The effect of a series of sodium salts on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide), PNIPAM, was investigated as a function of molecular weight and polymer concentration with a temperature gradient microfluidic device under a dark-field microscope. In solutions containing sufficient concentrations of kosmotropic anions, the phase transition of PNIPAM was resolved into two separate steps for higher molecular weight samples. The first step of this two step transition was found to be sensitive to the polymer’s molecular weight and solution concentration, while the second step was not. Moreover, the binding of chaotropic anions to the polymer was also influenced by molecular weight. Both sets of results could be explained by the formation of intramolecular and intermolecular hydrogen-bonding between polymer chains. By contrast, the hydrophobic hydration of the isopropyl moieties and polymer backbone was found to be unaffected by either the polymer’s molecular weight or solution concentration. PMID:18820735

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

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.

Simultaneous determination of molecular weights and contents of water-soluble polysaccharides and their fractions from Lycium barbarum collected in China.

PubMed

Wu, Ding-Tao; Lam, Shing-Chung; Cheong, Kit-Leong; Wei, Feng; Lin, Peng-Cheng; Long, Ze-Rong; Lv, Xiao-Jie; Zhao, Jing; Ma, Shuang-Cheng; Li, Shao-Ping

2016-09-10

Molecular weights and contents of water-soluble polysaccharides and their fractions in fifty batches of fruits of Lycium barbarum (wolfberry) collected from different regions of China, including Qinghai, Ningxia, Inner Mongolia, Xinjiang, and Gansu, were simultaneously determined using high performance size exclusion chromatography (HPSEC) coupled with multi angle laser light scattering (MALLS) and refractive index detector (RID) with the refractive index increment (dn/dc). Results showed that HPSEC chromatograms and molecular weight distributions of polysaccharides in L. barbarum collected from different regions of China were similar. Furthermore, the average contents of each polysaccharide fraction (peaks 1, 2, and 3) in crude polysaccharides of L. barbarum collected from Ningxia were similar with those of Inner Mongolia, Xinjiang, and Gansu, respectively. However, significant difference was found between polysaccharides in L. barbarum collected from Ningxia and Qinghai. Moreover, the average amounts of total polysaccharide fractions (peaks 1, 2, and 3) in the raw material of L. barbarum collected from Ningxia were significantly higher than that of Qinghai. These results may contribute to the rational usage of L. barbarum produced in China, and are beneficial for the improvement of their quality control. Results suggested that HPSEC-MALLS-RID with the dn/dc method could be used as a routine method for the quality evaluation of polysaccharides from natural resources and their products. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect and origin of the structure of hyperbranched polysiloxane on the surface and integrated performances of grafted Kevlar fibers

NASA Astrophysics Data System (ADS)

Zhang, Hongrui; Yuan, Li; Liang, Guozheng; Gu, Aijuan

2014-11-01

Four hyperbranched polysiloxanes (HPSis) with different molecular weights and concentration ratios of double bonds to epoxy groups (1:6.5-1:0.7) were synthesized and characterized. Each HPSi was facilely grafted onto surfaces of Kevlar fibers (KFs) to develop novel modified fibers (HPSi-g-KFs). The structures and integrated properties of HPSi-g-KFs as well as the origin behind were systematically investigated. Results show that HPSi-g-KFs have much rougher surface morphologies, and their surface free energies are as high as about 1.7 times that of KFs, showing greatly improved wettability. Besides, HPSi-g-KFs have excellent UV resistance after 168 h UV irradiation, the retentions of tenacity, energy to break, modulus and break extension are as high as 92, 86, 95 and 96%, respectively, while those of KFs are 66-85%. In addition, compared with KFs, HPSi-g-KFs have higher tensile tenacity and energy to break with similar modulus and break extension, much better thermal stability and flame retardancy. The nature of HPSi has different influence on different property of fibers, the HPSi with smaller molecular weight and more epoxy groups is beneficial to prepare HPSi-g-KFs with better wettability, while that with larger molecular weight and more double bonds tends to prepare HPSi-g-KF with better flame retardancy and UV resistance.

Receptors and aging: structural selectivity of the rhamnose-receptor on fibroblasts as shown by Ca(2+)-mobilization and gene-expression profiles.

PubMed

Faury, G; Molinari, J; Rusova, E; Mariko, B; Raveaud, S; Huber, P; Velebny, V; Robert, A M; Robert, L

2011-01-01

Qualitative and quantitative modifications of receptors were shown to play a key role in cell and tissue aging. We recently described the properties of a rhamnose-recognizing receptor on fibroblasts involved in the mediation of age-dependent functions of these cells. Using Ca(2+)-mobilization and DNA-microarrays we could show in the presence of rhamnose-rich oligo- and polysaccharides (RROPs) Ca(2+)-mobilization and changes in gene regulation. Here, we compared the effects of several RROPs, differing in their carbohydrate sequence and molecular weights, in normal human dermal fibroblasts (NHDFs). It appeared that different structural features were required for maximal effects on Ca(2+)-mobilization and gene-expression profiles. Maximal effect on Ca(2+) influx and intracellular free calcium regulation was exhibited by RROP-1, a 50 kDa average molecular weight polysaccharide, and RROP-3, a 5 kDa average molecular weight oligosaccharide with a different carbohydrate sequence. Maximal effect on gene-expression profiles was obtained with RROP-3. These results suggest the possibility of several different transmission pathways from the rhamnose-receptor to intracellular targets, differentially affecting these two intracellular functions, with potential consequences on aging. Although of only relative specificity, this receptor site exhibits a high affinity for rhamnose, absent from vertebrate glycoconjugates. The rhamnose-receptor might well represent an evolutionary conserved conformation of a prokaryote lectin. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

[Meta-analysis on randomized trials comparing the results of low-molecular weight heparins to those of fractioned heparins in the prevention of deep venous thrombosis].

PubMed

Daures, J P; Schved, J F; Momas, I; Gril, J C; Azoulay, P; Gremy, F

1989-01-01

The main reason for using low molecular weight heparin (LMWH) is its capacity to keep the antithrombotic effect of standard non-fractioned heparin (NFH) while reducing its hemorrhagic power. Various studies comparing LMWH to NFH gave contradictory results, so we carried out a meta-analysis of randomized trials comparing these two treatments in prevention of deep-vein thrombosis (DVT) (and in prevention of deep-vein thrombosis or pulmonary embolism). From a selection of ten trials we could not show any significant difference in the DVT rates, as well as for the whole of surgical indications as for the subgroups of abdominal and orthopedic surgery. The weighted global difference between the DVT rates is so low that, in spite of the use of meta-analysis, the power is clearly insufficient. The hemorrhagic risk is not statistically reduced as well for the whole of surgical indications as for the subgroups.

A structured understanding of cellobiohydrolase I binding to poplar lignin fractions after dilute acid pretreatment.

PubMed

Yao, Lan; Yoo, Chang Geun; Meng, Xianzhi; Li, Mi; Pu, Yunqiao; Ragauskas, Arthur J; Yang, Haitao

2018-01-01

Cellulase adsorption to lignin is considered a cost barrier for bioethanol production; however, its detailed association mechanism is still not fully understood. In this study, two natural poplar variants with high and low sugar release performance were selected as the low and high recalcitrant raw materials (named L and H , respectively). Three different lignin fractions were extracted using ethanol, followed by p -dioxane and then cellulase treatment from the dilute acid pretreated poplar solids (fraction 1, 2, and 3, respectively). Each lignin fraction had different physicochemical properties. Ethanol-extracted lignin had the lowest weight average molecular weight, while the molecular weights for the other two lignin fractions were similar. 31 P NMR analysis revealed that lignin fraction with higher molecular weight contained more aliphatic hydroxyl groups and less phenolic hydroxyl groups. Semi-quantitative analysis by 2D HSQC NMR indicated that the lignin fractions isolated from the natural variants had different contents of syringyl (S), guaiacyl (G) and interunit linkages. Lignin extracted by ethanol contained the largest amount of S units, the smallest amounts of G and p -hydroxybenzoate (PB) subunits, while the contents of these lignin subunits in the other two lignin fractions were similar. The lignin fraction obtained after cellulase treatment was primarily comprised of β- O -4 linkages with small amounts of β-5 and β-β linkages. The binding strength of these three lignin fractions obtained by Langmuir equations were in the order of L 1  >  L 3  >  L 2 for the low recalcitrance poplar and H 1  >  H 2  >  H 3 for the high recalcitrance poplar. Overall, adsorption ability of lignin was correlated with the sugar release of poplar. Structural features of lignin were associated with its binding to CBH. For natural poplar variants, lignin fractions with lower molecular weight and polydispersity index (PDI) exhibited more CBH adsorption ability. Lignins with more phenolic hydroxyl groups had higher CBH binding strength. It was also found that lignin fractions with more condensed aromatics adsorbed more CBH likely attributed to stronger hydrophobic interactions.

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)

Study on different molecular weights of chitosan as an immobilization matrix for a glucose biosensor.

PubMed

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 ([Formula: see text]) 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 the potential to be a suitable matrix for the development of glucose biosensors.

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 the potential to be a suitable matrix for the development of glucose biosensors. PMID:23940599

SEDFIT-MSTAR: Molecular weight and molecular weight distribution analysis of polymers by sedimentation equilibrium in the ultracentrifuge

PubMed Central

Schuck, Peter; Gillis, Richard B.; Besong, Tabot M.D.; Almutairi, Fahad; Adams, Gary G.; Rowe, Arthur J.; Harding, Stephen E.

2014-01-01

Sedimentation equilibrium (analytical ultracentrifugation) is one of the most inherently suitable methods for the determination of average molecular weights and molecular weight distributions of polymers, because of its absolute basis (no conformation assumptions) and inherent fractionation ability (without the need for columns or membranes and associated assumptions over inertness). With modern instrumentation it is also possible to run up to 21 samples simultaneously in a single run. Its application has been severely hampered because of difficulties in terms of baseline determination (incorporating estimation of the concentration at the air/solution meniscus) and complexity of the analysis procedures. We describe a new method for baseline determination based on a smart-smoothing principle and built into the highly popular platform SEDFIT for the analysis of the sedimentation behavior of natural and synthetic polymer materials. The SEDFIT-MSTAR procedure – which takes only a few minutes to perform - is tested with four synthetic data sets (including a significantly non-ideal system) a naturally occurring protein (human IgG1) and two naturally occurring carbohydrate polymers (pullulan and λ–carrageenan) in terms of (i) weight average molecular weight for the whole distribution of species in the sample (ii) the variation in “point” average molecular weight with local concentration in the ultracentrifuge cell and (iii) molecular weight distribution. PMID:24244936

An official American Thoracic Society Workshop Report: presentations and discussion of the fifth Jack Pepys Workshop on Asthma in the Workplace. Comparisons between asthma in the workplace and non-work-related asthma.

PubMed

Malo, Jean-Luc; Tarlo, Susan M; Sastre, Joaquin; Martin, James; Jeebhay, Mohamed F; Le Moual, Nicole; Heederik, Dick; Platts-Mills, Thomas; Blanc, Paul D; Vandenplas, Olivier; Moscato, Gianna; de Blay, Frédéric; Cartier, André

2015-07-01

The fifth Jack Pepys Workshop on Asthma in the Workplace focused on the similarities and differences of work-related asthma (WRA) and non-work-related asthma (non-WRA). WRA includes occupational asthma (OA) and work-exacerbated asthma (WEA). There are few biological differences in the mechanisms of sensitization to environmental and occupational allergens. Non-WRA and OA, when due to high-molecular-weight agents, are both IgE mediated; it is uncertain whether OA due to low-molecular-weight agents is also IgE mediated. Risk factors for OA include female sex, a history of upper airway symptoms, and a history of bronchial hyperresponsiveness. Atopy is a risk factor for OA due to high-molecular-weight agents, and exposure to cleaning agents is a risk factor for both OA and non-WRA. WEA is important among workers with preexisting asthma and may overlap with irritant-induced asthma, a type of OA. Induced sputum cytology can confirm airway inflammation, but specific inhalation challenge is the reference standard diagnostic test. Inhalation challenges are relatively safe, with the most severe reactions occurring with low-molecular-weight agents. Indirect health care costs account for about 50% of total asthma costs. Workers with poor asthma control (WRA or non-WRA) are less likely to be employed. Income loss is a major contributor to the indirect costs of WRA. Overall, asthma outcomes probably are worse for adult-onset than for childhood-onset asthma but better for OA than adult-onset non-WRA. Important aspects of management of OA are rapid and proper confirmation of the diagnosis and reduction of exposure to sensitizers or irritants at work and home.

Hyaluronan influence on the onset of chondrogenic differentiation of mesenchymal stem cells.

PubMed

Dvorakova, Jana; Velebny, Vladimir; Kubala, Lukas

2008-10-01

Hyaluronan (HA) is an abundant component of chondrogenic tissue hence it is often used as a fundamental constituent in cartilage tissue substitutes. However, effects of different molecular weight HA on chondrogenic differentiation are not clear. The aim was to evaluate modulation of mesenchymal stem cell (MSC) early chondrogenesis by HA of molecular weights 100, 600 and 1 500 kDa. HA was applied on MSCs cultured in a pellet system for one, two and three weeks. Chondrogenesis was evaluated by determinations of gene expression of transcription factor Sox-9 and extracellular matrix proteins collagen type II and XI, aggrecan, and COMP by Real-Time PCR and completed with histological analysis. Upon chondrogenic induction, the respective pellets revealed active transcription of the chondrogenic genes together with proceeding accumulation of glycosaminoglycan (GAG) rich extracellular matrix. Sox-9 was also expressed in non-chondrogenic MSC controls. HA treated pellets were not significantly influenced on day 7 of culture. However, on day 14, lowered expression in some of the extracellular matrix proteins appeared together with a moderately smaller amount of GAG content in pellet sections. Nevertheless, the analysis on day 21 has demonstrated that HA did not affect the outcome of the differentiation by the end of the culture. Any difference regarding the molecular weight of the HA was not found. It could be speculated that HA induced a time shift in the phase of the dominant matrix protein onset which was in full compensated by the end of the evaluated time period. Thus, data suggest that HA of any tested molecular weight does not significantly modulate chondrogenesis of MSCs in pellet system.

Revealing Sources and Distribution Changes of Dissolved Organic Matter (DOM) in Pore Water of Sediment from the Yangtze Estuary

PubMed Central

Wang, Ying; Zhang, Di; Shen, Zhenyao; Feng, Chenghong; Chen, Jing

2013-01-01

Dissolved organic matter (DOM) in sediment pore waters from Yangtze estuary of China based on abundance, UV absorbance, molecular weight distribution and fluorescence were investigated using a combination of various parameters of DOM as well as 3D fluorescence excitation emission matrix spectra (F-EEMS) with the parallel factor and principal component analysis (PARAFAC-PCA). The results indicated that DOM in pore water of Yangtze estuary was very variable which mainly composed of low aromaticity and molecular weight materials. Three humic-like substances (C1, C2, C4) and one protein-like substance (C3) were identified by PARAFAC model. C1, C2 and C4 exhibited same trends and were very similar. The separation of samples on both axes of the PCA showed the difference in DOM properties. C1, C2 and C4 concurrently showed higher positive factor 1 loadings, while C3 showed highly positive factor 2 loadings. The PCA analysis showed a combination contribution of microbial DOM signal and terrestrial DOM signal in the Yangtze estuary. Higher and more variable DOM abundance, aromaticity and molecular weight of surface sediment pore water DOM can be found in the southern nearshore than the other regions primarily due to the influence of frequent and intensive human activities and tributaries inflow in this area. The DOM abundance, aromaticity, molecular weight and fluorescence intensity in core of different depth were relative constant and increased gradually with depth. DOM in core was mainly composed of humic-like material, which was due to higher release of the sedimentary organic material into the porewater during early diagenesis. PMID:24155904

An Official American Thoracic Society Workshop Report: Presentations and Discussion of the Fifth Jack Pepys Workshop on Asthma in the Workplace. Comparisons between Asthma in the Workplace and Non–Work-related Asthma

PubMed Central

Malo, Jean-Luc; Sastre, Joaquin; Martin, James; Jeebhay, Mohamed F.; Le Moual, Nicole; Heederik, Dick; Platts-Mills, Thomas; Blanc, Paul D.; Vandenplas, Olivier; Moscato, Gianna; de Blay, Frédéric; Cartier, André

2015-01-01

The fifth Jack Pepys Workshop on Asthma in the Workplace focused on the similarities and differences of work-related asthma (WRA) and non–work-related asthma (non-WRA). WRA includes occupational asthma (OA) and work-exacerbated asthma (WEA). There are few biological differences in the mechanisms of sensitization to environmental and occupational allergens. Non-WRA and OA, when due to high-molecular-weight agents, are both IgE mediated; it is uncertain whether OA due to low-molecular-weight agents is also IgE mediated. Risk factors for OA include female sex, a history of upper airway symptoms, and a history of bronchial hyperresponsiveness. Atopy is a risk factor for OA due to high-molecular-weight agents, and exposure to cleaning agents is a risk factor for both OA and non-WRA. WEA is important among workers with preexisting asthma and may overlap with irritant-induced asthma, a type of OA. Induced sputum cytology can confirm airway inflammation, but specific inhalation challenge is the reference standard diagnostic test. Inhalation challenges are relatively safe, with the most severe reactions occurring with low-molecular-weight agents. Indirect health care costs account for about 50% of total asthma costs. Workers with poor asthma control (WRA or non-WRA) are less likely to be employed. Income loss is a major contributor to the indirect costs of WRA. Overall, asthma outcomes probably are worse for adult-onset than for childhood-onset asthma but better for OA than adult-onset non-WRA. Important aspects of management of OA are rapid and proper confirmation of the diagnosis and reduction of exposure to sensitizers or irritants at work and home. PMID:26203621

The production of high efficiency Ziegler-Natta catalyst with dual active sites nature using cyclohexyl chloride as promoter with super activity and produced superior polyethylene with controllable molecular weight distribution.

PubMed

Seifali Abbas-Abadi, Mehrdad

2017-01-01

In the previous studies, the several halocarbons (HC) were tested as promoters for a Ti-based Ziegler-Natta (ZN) catalyst at different polymerization conditions. The Results showed that chloro cyclohexane has the best operation in catalyst activity, polymer particle size growth, hydrogen responsibility and wax reduction too. For the first time in this study, the effect of Al/Ti ratio on the optimum HC/Ti ratio has been considered and the results showed that the optimum HC/Ti ratio depends on the Al/Ti ratio directly. In the optimum HC/Ti ratio, the catalyst activity and hydrogen responsibility ratio of the catalyst increase up to 125 and 55% respectively. The acceptable growth of polymer powder up to 46%, lower flow rate ratio (FRR) up to 19% and decrease of wax amount up to 12%, completed the promotion results. Furthermore, in the next part of this study and as key note, a little dose of halocarbon was used in the catalyst preparation to produce the special catalysts with dual active sites. In the catalyst preparation, the concentration of each active sites depends on the halocarbon amount and it can control the molecular weight distribution of the produced polyethylene; because each active sites have different response to hydrogen. The halocarbon based catalysts showed the remarkable effect on the catalyst activity, the molecular weight and especially molecular weight distribution (MWD). The flow rate ratio and MWD could be increased up to 77 and 88% respectively as the main result of halocarbon addition during the catalyst preparation.

The production of high efficiency Ziegler–Natta catalyst with dual active sites nature using cyclohexyl chloride as promoter with super activity and produced superior polyethylene with controllable molecular weight distribution

PubMed Central

Seifali Abbas-Abadi, Mehrdad

2017-01-01

Abstract In the previous studies, the several halocarbons (HC) were tested as promoters for a Ti-based Ziegler–Natta (ZN) catalyst at different polymerization conditions. The Results showed that chloro cyclohexane has the best operation in catalyst activity, polymer particle size growth, hydrogen responsibility and wax reduction too. For the first time in this study, the effect of Al/Ti ratio on the optimum HC/Ti ratio has been considered and the results showed that the optimum HC/Ti ratio depends on the Al/Ti ratio directly. In the optimum HC/Ti ratio, the catalyst activity and hydrogen responsibility ratio of the catalyst increase up to 125 and 55% respectively. The acceptable growth of polymer powder up to 46%, lower flow rate ratio (FRR) up to 19% and decrease of wax amount up to 12%, completed the promotion results. Furthermore, in the next part of this study and as key note, a little dose of halocarbon was used in the catalyst preparation to produce the special catalysts with dual active sites. In the catalyst preparation, the concentration of each active sites depends on the halocarbon amount and it can control the molecular weight distribution of the produced polyethylene; because each active sites have different response to hydrogen. The halocarbon based catalysts showed the remarkable effect on the catalyst activity, the molecular weight and especially molecular weight distribution (MWD). The flow rate ratio and MWD could be increased up to 77 and 88% respectively as the main result of halocarbon addition during the catalyst preparation. PMID:29491824

Characterization of oxidized tannins: comparison of depolymerization methods, asymmetric flow field-flow fractionation and small-angle X-ray scattering.

PubMed

Vernhet, Aude; Dubascoux, Stéphane; Cabane, Bernard; Fulcrand, Hélène; Dubreucq, Eric; Poncet-Legrand, Céline

2011-09-01

Condensed tannins are a major class of plant polyphenols. They play an important part in the colour and taste of foods and beverages. Due to their chemical reactivity, tannins are not stable once extracted from plants. A number of chemical reactions can take place, leading to structural changes of the native structures to give so-called derived tannins and pigments. This paper compares results obtained on native and oxidized tannins with different techniques: depolymerization followed by high-performance liquid chromatography analysis, small-angle X-ray scattering (SAXS) and asymmetric flow field-flow fractionation (AF4). Upon oxidation, new macromolecules were formed. Thioglycolysis experiments showed no evidence of molecular weight increase, but thioglycolysis yields drastically decreased. When oxidation was performed at high concentration (e.g., 10 g L(-1)), the weight average degree of polymerization determined from SAXS increased, whereas it remained stable when oxidation was done at low concentration (0.1 g L(-1)), indicating that the reaction was intramolecular, yet the conformations were different. Differences in terms of solubility were observed; ethanol being a better solvent than water. We also separated soluble and non-water-soluble species of a much oxidized fraction. Thioglycolysis showed no big differences between the two fractions, whereas SAXS and AF4 showed that insoluble macromolecules have a weight average molecular weight ten times higher than the soluble ones.

The characteristics of pyrophosphate: D-fructose-6-phosphate 1-phosphotransferases from Sansevieria trifasciata leaves and Phaseolus coccineus stems.

PubMed

Kowalczyk, S

1987-01-01

Three different molecular forms of pyrophosphate-dependent phosphofructokinase have been isolated: one from Sansevieria trifasciata leaves and two from Phaseolus coccineus stems. The form isolated from S. trifasciata has the molecular weight of about 115,000. The apparent molecular weights for the two forms from mung bean were approximately 220,000 and 450,000. All three forms have the same pH optima, an absolute requirement for Mg2+ ions both in the forward and reverse reaction, but differ in their sensitivity toward fructose 2,6-bisphosphate. Kinetic properties of the partially purified enzymes have been investigated in the presence and absence of fructose 2,6-bisphosphate. Pyrophosphate-dependent phosphofructokinase from S. trifasciata exhibited hyperbolic kinetics with all substrates tested. The saturation curves of the enzyme (form A) from mung bean for pyrophosphate, fructose 6-phosphate and fructose 1,6-bisphosphate were sigmoidal in the absence of fructose 2,6-bisphosphate. In the presence of fructose 2,6-bisphosphate these kinetics became hyperbolic.

How Molecular Size Impacts RMSD Applications in Molecular Dynamics Simulations.

PubMed

Sargsyan, Karen; Grauffel, Cédric; Lim, Carmay

2017-04-11

The root-mean-square deviation (RMSD) is a similarity measure widely used in analysis of macromolecular structures and dynamics. As increasingly larger macromolecular systems are being studied, dimensionality effects such as the "curse of dimensionality" (a diminishing ability to discriminate pairwise differences between conformations with increasing system size) may exist and significantly impact RMSD-based analyses. For such large bimolecular systems, whether the RMSD or other alternative similarity measures might suffer from this "curse" and lose the ability to discriminate different macromolecular structures had not been explicitly addressed. Here, we show such dimensionality effects for both weighted and nonweighted RMSD schemes. We also provide a mechanism for the emergence of the "curse of dimensionality" for RMSD from the law of large numbers by showing that the conformational distributions from which RMSDs are calculated become increasingly similar as the system size increases. Our findings suggest the use of weighted RMSD schemes for small proteins (less than 200 residues) and nonweighted RMSD for larger proteins when analyzing molecular dynamics trajectories.

Prediction of stream volatilization coefficients

USGS Publications Warehouse

Rathbun, Ronald E.

1990-01-01

Equations are developed for predicting the liquid-film and gas-film reference-substance parameters for quantifying volatilization of organic solutes from streams. Molecular weight and molecular-diffusion coefficients of the solute are used as correlating parameters. Equations for predicting molecular-diffusion coefficients of organic solutes in water and air are developed, with molecular weight and molal volume as parameters. Mean absolute errors of prediction for diffusion coefficients in water are 9.97% for the molecular-weight equation, 6.45% for the molal-volume equation. The mean absolute error for the diffusion coefficient in air is 5.79% for the molal-volume equation. Molecular weight is not a satisfactory correlating parameter for diffusion in air because two equations are necessary to describe the values in the data set. The best predictive equation for the liquid-film reference-substance parameter has a mean absolute error of 5.74%, with molal volume as the correlating parameter. The best equation for the gas-film parameter has a mean absolute error of 7.80%, with molecular weight as the correlating parameter.

Cerebral Apolipoprotein-D Is Hypoglycosylated Compared to Peripheral Tissues and Is Variably Expressed in Mouse and Human Brain Regions.

PubMed

Li, Hongyun; Ruberu, Kalani; Karl, Tim; Garner, Brett

2016-01-01

Recent studies have shown that cerebral apoD levels increase with age and in Alzheimer's disease (AD). In addition, loss of cerebral apoD in the mouse increases sensitivity to lipid peroxidation and accelerates AD pathology. Very little data are available, however, regarding the expression of apoD protein levels in different brain regions. This is important as both brain lipid peroxidation and neurodegeneration occur in a region-specific manner. Here we addressed this using western blotting of seven different regions (olfactory bulb, hippocampus, frontal cortex, striatum, cerebellum, thalamus and brain stem) of the mouse brain. Our data indicate that compared to most brain regions, the hippocampus is deficient in apoD. In comparison to other major organs and tissues (liver, spleen, kidney, adrenal gland, heart and skeletal muscle), brain apoD was approximately 10-fold higher (corrected for total protein levels). Our analysis also revealed that brain apoD was present at a lower apparent molecular weight than tissue and plasma apoD. Utilising peptide N-glycosidase-F and neuraminidase to remove N-glycans and sialic acids, respectively, we found that N-glycan composition (but not sialylation alone) were responsible for this reduction in molecular weight. We extended the studies to an analysis of human brain regions (hippocampus, frontal cortex, temporal cortex and cerebellum) where we found that the hippocampus had the lowest levels of apoD. We also confirmed that human brain apoD was present at a lower molecular weight than in plasma. In conclusion, we demonstrate apoD protein levels are variable across different brain regions, that apoD levels are much higher in the brain compared to other tissues and organs, and that cerebral apoD has a lower molecular weight than peripheral apoD; a phenomenon that is due to the N-glycan content of the protein.

Expression and biochemical characteristics of two different aldosterone receptors in both healthy and dilated cardiomyopathy dog heart tissue.

PubMed

Reynoso Palomar, Alejandro R; Rodriguez Bravo, Moncerrat; Villa Mancera, Abel E; Mucha, Carlos J

2017-03-01

Recently, replicates of the aldosterone receptor expression have been done in healthy heart dog tissues through immunohistochemistry, showing an apparent heterogeneous distribution in the four chambers. Recent studies have also identified immediate effects of aldosterone, suggesting aldosterone also produces non-genomic effects caused by an unidentified receptor. In order to study the molecular and quantitative expression characteristics of aldosterone binding receptors in the canine heart, we conducted studies, using Western Blot, in the heart from both healthy animals and animals with dilated cardiomyopathy. The results show the presence and distribution of two aldosterone receptors; one of 110/120 kDa molecular weight, suggested as cytosolic/nuclear and the other of undetermined location with a 250 kDa molecular weight.

Phenolic compounds in chestnut (Castanea sativa Mill.) heartwood. Effect of toasting at cooperage.

PubMed

Sanz, Miriam; Cadahía, Estrella; Esteruelas, Enrique; Muñoz, Angel Ma; Fernández de Simón, Brígida; Hernández, Teresa; Estrella, Isabel

2010-09-08

The phenolic and tannic composition of heartwood extracts from Castanea sativa Mill., before and after toasting in cooperage, were studied using HPLC-DAD and HPLC-DAD/ESI-MS, and some low molecular weight phenolic compounds and hydrolyzable tannins were found. The low molecular weight phenolic compounds were lignin constituents as the acids gallic, protocatechuic, vanillic, syringic, ferulic, and ellagic, the aldehydes protocatechuic, vanillic, syringic, coniferylic, and sinapic, and the coumarin scopoletin. Their patterns were somewhat different those of oak because oak does not contain compounds such protocatechuic acid and aldehyde and is composed of much lower amounts of gallic acid than chestnut. Vescalagin and castalagin were the main ellagitannins, and acutissimin was tentatively identified for the first time in this wood. Moreover, some gallotannins were tentatively identified, including different isomers of di, tri, tetra, and pentagalloyl glucopyranose, and di and trigalloyl-hexahydroxydiphenoyl glucopyranose, comprising 20 different compounds, as well as some ellagic derivatives such as ellagic acid deoxyhexose, ellagic acid dimer dehydrated, and valoneic acid dilactone. These ellagic derivatives as well as some galloyl and hexahydroxydiphenoyl derivatives were tentatively identified for the first time in this wood. The profile of tannins was therefore different from that of oak wood because oak only contains tannins of the ellagitannins type. Seasoned and toasted chestnut wood showed a very different balance between lignin derivatives and tannins because toasting resulted in the degradation of tannins and the formation of low molecular weight phenolic compounds from lignin degradation. Moreover, the different toasting levels provoked different balances between tannins and lignin constituents because the intensity of lignin and tannin degradation was in relation to the intensity of toasting.

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

2015-04-03

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.

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.

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.

Effects of ionic liquids on the performance of IPMC

NASA Astrophysics Data System (ADS)

Kim, Min Jung; Park, Sang Woo; Won, Joohye; Nah, Changwoon

2017-04-01

One of the issues in operating the IPMC actuators in air condition is the limited lifetime due to the evaporation of aqueous electrolytes like water. Several attempts were already made for solving the problem using an ionic liquid (IL) with higher boiling point. In this study, three different ILs having similar boiling point but different molecular weight were employed in the IPMC actuators. The actuation performance, notably speed and lifetime, were measured and they are compared with that of water-based IPMC actuator. The lower molecular weight IL showed a comparable actuation speed of water due to faster movement of the ion cluster. The lifetime of the water-based IPMC actuator was found to be only 3 hr. However, the IL-based IPMC actuators showed much improved service life.

Spray drying of silica microparticles for sustained release application with a new sol-gel precursor.

PubMed

Wang, Bifeng; Friess, Wolfgang

2017-10-30

A new precursor, tetrakis(2-methoxyethyl) orthosilicate (TMEOS) was used to fabricate microparticles for sustained release application, specifically for biopharmaceuticals, by spray drying. The advantages of TMEOS over the currently applied precursors are its water solubility and hydrolysis at moderate pH without the need of organic solvents or catalyzers. Thus a detrimental effect on biomolecular drug is avoided. By generating spray-dried silica particles encapsulating the high molecular weight model compound FITC-dextran 150 via the nano spray dryer Büchi-90, we demonstrated how formulation parameters affect and enable control of drug release properties. The implemented strategies to regulate release included incorporating different quantities of dextrans with varying molecular weight as well as adjusting the pH of the precursor solution to modify the internal microstructures. The addition of dextran significantly altered the released amount, while the release became faster with increasing dextran molecular weight. A sustained release over 35days could be achieved with addition of 60 kD dextran. The rate of FITC-Dextran 150 release from the dextran 60 containing particles decreased with higher precursor solution pH. In conclusion, the new precursor TMEOS presents a promising alternative sol-gel technology based carrier material for sustained release application of high molecular weight biopharmaceutical drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

Crosslink Density and Molecular Weight Effects on the Viscoelastic Response of a Glassy High-Performance Polyimide

NASA Technical Reports Server (NTRS)

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

2001-01-01

Durability and long-term performance are among the primary concerns for the use of advanced polymer matrix composites (PMCs) in modern aerospace structural applications. For a PMC subJected to long-term exposure at elevated temperatures. the viscoelastic nature of the polymer matrix will contribute to macroscopic changes in composite stiffness, strength and fatigue life. Over time. changes in the polymer due to physical aging will have profound effects on tile viscoelastic compliance of the material, hence affecting its long-term durability. Thus, the ability to predict material performance using intrinsic properties, such as crosslink density and molecular weight, would greatly enhance the efficiency of design and development of PMCs. The objective of this paper is to discuss and present the results of an experimental study that considers the effects of crosslink density, molecular weight and temperature on the viscoelastic behavior including physical aging of an advanced polymer. Five distinct variations in crosslink density were used to evaluate the differences in mechanical performance of an advanced polyimide. The physical aging behavior was isolated by conducting sequenced, short-term isothermal creep compliance tests in tension. These tests were performed over a range of sub-glass transition temperatures. The material constants, material master curves and physical aging-related parameters were evaluated as a function of temperature crosslink density and molecular weight using time-temperature and time-aging time superposition techniques.

High Molecular Weight Isoforms of Growth Hormone In Cells of the Immune System

PubMed Central

Weigent, Douglas A.

2013-01-01

A substantial body of research exists to support the idea that cells of the immune system produce growth hormone (GH). However, the structure and mechanism of action of lymphocyte-derived GH continues to remain largely unknown. Here we present the results of Western analysis of whole cell extracts showing that different molecular weight isoforms of GH of approximately 100 kDa, 65 kDa, and 48 kDa can be detected in primary mouse cells of the immune system and in the mouse EL4 cell line. The identity of the 65 kDa and 48 kDa isoforms of GH were confirmed by mass spectrometry. The various isoforms were detected in both enriched T and B spleen cell populations. The large molecular weight isoform appears to reside primarily in the cytoplasm whereas the lower molecular weight 65 kDa and 48 kDa isoforms were detected primarily in the nucleus. These results also suggest that GH isoforms are induced by oxidative stress. In EL4 cells overexpressing GH, the expression of luciferase controlled by a promoter containing the antioxidant response element is increased almost three-fold above control. The data suggest that the induction of isoforms of the GH molecule in cells of the immune system may be an important mechanism of adaptation and/or protection of lymphoid cells under conditions of oxidative stress. PMID:21741628

Adiponectin isoform patterns in ethnic-specific ADIPOQ mutation carriers: The IRAS Family Study

PubMed Central

Tabb, Keri L.; Gao, Chuan; Hicks, Pamela J.; Hawkins, Gregory A.; Rotter, Jerome I.; da Chen, Yii-Der I; Guo, Xiuqing; Norris, Jill M.; Lorenzo, Carlos; Freedman, Barry I.; Bowden, Donald W.; Palmer, Nicholette D.

2017-01-01

Objective Adiponectin is found in human serum in three groups of multimers (high, medium, and low molecular weight). Previously, we reported two ethnic-specific variants in ADIPOQ, G45R (Hispanic Americans) and R55C (African Americans). Although carriers of both variants had mean adiponectin levels ≤20% of those of non-carriers, they were not clinically different from non-carriers. To compare carriers of both variants and non-carriers, relative quantification of adiponectin isoforms to total adiponectin was performed on serum samples. Methods The multimeric patterns of serum adiponectin in G45R carriers (n=23), R55C carriers (n=3), and Hispanic and African American non-carriers (n=84 and 44, respectively) from the IRAS Family Study were explored using native western blotting and densitometry. Results Serum samples from carriers showed an absence of the high molecular weight (HMW) isoform and a marked reduction in the medium molecular weight isoform but an approximate two-fold increase in the amount of the low molecular weight isoform (LMW). Thus, individuals making only LMW adiponectin are metabolically normal. Conclusions The results contrast with the proposed biological importance of the HMW multimer. This suggests that the LMW isoform may functionally compensate for some of the loss/reduction of the higher-order multimers in carriers of the G45R and R55C mutations. PMID:28643464

Radiation-induced controlled polymerization of acrylic acid by RAFT and RAFT-MADIX methods in protic solvents

NASA Astrophysics Data System (ADS)

Sütekin, S. Duygu; Güven, Olgun

2018-01-01

The kinetic investigation of one-pot synthesis of poly(acrylic acid) (PAA) prepared via gamma radiation induced controlled polymerization was reported. PAA homopolymers were prepared by Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization in the presence of trithiocarbonate-based chain transfer agent (CTA) 2-(Dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT) and also by Reversible Addition-Fragmentation/Macromolecular Design by Inter-change of Xanthates (RAFT/MADIX) polymerization in the presence of a xanthate based CTA O-ethyl-S-(1-methoxycarbonyl) ethyl dithiocarbonate (RA1). The polymerizations were performed at room temperature by the virtue of ionizing radiation. Protic solvents were used for the RAFT polymerization of AA considering environmental profits. The linear first-order kinetic plot, close control of molecular weight by the monomer/CTA molar ratio supported that the polymerization proceeds in a living fashion. The linear increase in molecular weight with conversion monitored by Size Exclusion Chromatography (SEC) is another proof of controlling of polymerization. [Monomer]/[RAFT] ratio and conversion was controlled to obtain PAA in the molecular weight range of 6900-35,800 with narrow molecular weight distributions. Reaction kinetics and effect of the amount of RAFT agent were investigated in detail. Between two different types of CTA, trithiocarbonate based DDMAT was found to be more efficient in terms of low dispersity (Đ) and linear first-order kinetic behavior for the radiation induced controlled synthesis of PAA homopolymers.

Tuning Molecular Weights of Bombyx mori (B. mori) Silk Sericin to Modify Its Assembly Structures and Materials Formation

PubMed Central

2015-01-01

Bombyx mori (B. mori) silk sericin is a protein with features desirable as a biomaterial, such as increased hydrophilicity and biodegradation, as well as resistance to oxidation, bacteria, and ultraviolet light. In contrast to other widely studied B. mori silk proteins such as fibroin, sericin is still unexplored as a building block for fabricating biomaterial, and thus a facile technique of processing it into a material is needed. Here, electrospinning technology was used to fabricate it into biomaterials from two forms of B. mori silk sericin with different molecular weights, one is a low (12.0 kDa) molecular sericin (LS) form and another is a high (66.0 kDa) molecular weight sericin (HS) form. Circular dichroism (CD) spectra showed that LS in hexafluoroacetone (HFA) solvent adopted a predominantly random coil conformation, whereas HS tended to form a β-sheet structure along with a large content of random coils. In addition, LS and HS in HFA solvent were found to form cylinder-like smaller nanoparticles and larger irregular aggregates before electrospinning, respectively. As a result, biomaterials based on microparticles and nanofibers were successfully fabricated by electrospinning of LS and HS dissolved in HFA, respectively. The cell viability and differentiation assay indicated that nanofibers and microparticles improved cell adhesion, growth, and differentiation, proving that the scaffolds electrospun from sericin are biocompatible regardless of its molecular weight. The microparticles, not common in electrospinning of silk proteins reported previously, were found to promote the osteogenic differentiation of mesenchymal stem cells in comparison to the nanofibers. This study suggested that molecular weight of sericin mediates its secondary structure and assembly structure, which in turn leads to a control of final morphology of the electrospun materials. The microparticles and nanofibers of sericin can be potentially used as building blocks for fabricating the scaffolds for tissue engineering. PMID:25050697

Tuning molecular weights of Bombyx mori (B. mori) silk sericin to modify its assembly structures and materials formation.

PubMed

Yang, Mingying; Shuai, Yajun; Zhou, Guanshan; Mandal, Namita; Zhu, Liangjun; Mao, Chuanbin

2014-08-27

Bombyx mori (B. mori) silk sericin is a protein with features desirable as a biomaterial, such as increased hydrophilicity and biodegradation, as well as resistance to oxidation, bacteria, and ultraviolet light. In contrast to other widely studied B. mori silk proteins such as fibroin, sericin is still unexplored as a building block for fabricating biomaterial, and thus a facile technique of processing it into a material is needed. Here, electrospinning technology was used to fabricate it into biomaterials from two forms of B. mori silk sericin with different molecular weights, one is a low (12.0 kDa) molecular sericin (LS) form and another is a high (66.0 kDa) molecular weight sericin (HS) form. Circular dichroism (CD) spectra showed that LS in hexafluoroacetone (HFA) solvent adopted a predominantly random coil conformation, whereas HS tended to form a β-sheet structure along with a large content of random coils. In addition, LS and HS in HFA solvent were found to form cylinder-like smaller nanoparticles and larger irregular aggregates before electrospinning, respectively. As a result, biomaterials based on microparticles and nanofibers were successfully fabricated by electrospinning of LS and HS dissolved in HFA, respectively. The cell viability and differentiation assay indicated that nanofibers and microparticles improved cell adhesion, growth, and differentiation, proving that the scaffolds electrospun from sericin are biocompatible regardless of its molecular weight. The microparticles, not common in electrospinning of silk proteins reported previously, were found to promote the osteogenic differentiation of mesenchymal stem cells in comparison to the nanofibers. This study suggested that molecular weight of sericin mediates its secondary structure and assembly structure, which in turn leads to a control of final morphology of the electrospun materials. The microparticles and nanofibers of sericin can be potentially used as building blocks for fabricating the scaffolds for tissue engineering.

Development of a nanofiltration method for bone collagen 14C AMS dating

NASA Astrophysics Data System (ADS)

Boudin, Mathieu; Boeckx, Pascal; Buekenhoudt, Anita; Vandenabeele, Peter; Van Strydonck, Mark

2013-01-01

Radiocarbon dating of bones is usually performed on the collagen fraction. However, this collagen can contain exogenous molecules, including humic substances (HSs) and/or other soil components that may have a different age than the bone. Incomplete removal can result in biased 14C dates. Ultrafiltration of collagen, dissolved as gelatin (molecular weight (MW) ∼100,000 Dalton), has received considerable attention to obtain more reliable dates. Ultrafiltration is an effective method of removal of low-molecular weight contaminants from bone collagen but it does not remove high-molecular weight contaminants, such as cross-linked humic collagen complexes. However, comparative dating studies have raised the question whether this cleaning step itself may introduce contamination with carbon from the filters used. In this study, a nanofiltration method was developed using a ceramic filter to avoid a possible extraneous carbon contamination introduced by the filter. This method should be applicable to various protein materials e.g. collagen, silk, wool, leather and should be able to remove low-molecular and high molecular weight HSs. In this study bone collagen was hot acid hydrolyzed to amino acids and nanofiltrated. A filter with a molecular weight cutoff (MWCO) of 450 Dalton was chosen in order to collect the amino acids in the permeate and the HSs in the retentate. Two pilot studies were set up. Two nanofiltration types were tested in pilot study 1: dead end and cross flow filtration. Humic substance (HS)-solutions with fossil carbon and modern hydrolyzed collagen contaminated with HSs were filtrated and analyzed with spectrofluorescence to determine the HS removal. Cross flow nanofiltration showed the most efficient HS removal. A second pilot study based upon these results was set up wherein only cross flow filtration was performed. 14C measurements of the permeates of hydrolyzed modern collagen contaminated with fossil HSs demonstrate a significant but incomplete removal of HSs (between 63% and 85%).

Multiple forms of ADP-glucose pyrophosphorylase from tomato fruit

NASA Technical Reports Server (NTRS)

Chen, B. Y.; Janes, H. W.

1997-01-01

ADP-glucose pyrophosphorylase (AGP) was purified from tomato (Lycopersicon esculentum Mill.) fruit to apparent homogeneity. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis the enzyme migrated as two close bands with molecular weights of 50,000 and 51,000. Two-dimensional polyacrylamide gel electrophoresis analysis of the purified enzyme, however, revealed at least five major protein spots that could be distinguished by their slight differences in net charge and molecular weight. Whereas all of the spots were recognized by the antiserum raised against tomato fruit AGP holoenzyme, only three of them reacted strongly with antiserum raised against the potato tuber AGP large subunit, and the other two spots (with lower molecular weights) reacted specifically with antisera raised against spinach leaf AGP holoenzyme and the potato tuber AGP small subunit. The results suggest the existence of at least three isoforms of the AGP large subunit and two isoforms of the small subunit in tomato fruit in vivo. The native molecular mass of the enzyme determined by gel filtration was 220 +/- 10 kD, indicating a tetrameric structure for AGP from tomato fruit. The purified enzyme is very sensitive to 3-phosphoglycerate/inorganic phosphate regulation.

Bioremediation of coal contaminated soil under sulfate-reducing condition.

PubMed

Kuwano, Y; Shimizu, Y

2006-01-01

The objective of this study was to investigate the biodegradation of coal-derived hydrocarbons, especially high molecular weight (HMW) components, under anaerobic conditions. For this purpose biodegradation experiments were performed, using specifically designed soil column bioreactors. For the experiment, coal-contaminated soil was prepared, which contains high molecular weight hydrocarbons at high concentration (approx. 55.5 mgC g-drysoil(-1)). The experiment was carried out in two different conditions: sulfate reducing (SR) condition (SO4(2-) = 10 mmol l(-1) in the liquid medium) and control condition (SO4(2-)<0.5 mmol l(-1)). Although no degradation was observed under the control condition, the resin fraction decreased to half (from 6,541 to 3,386 mgC g-soil(-1)) under SR condition, with the concomitant increase of two PAHs (phenanthrene and fluoranthene, 9 and 2.5 times, respectively). From these results, we could conclude that high molecular hydrocarbons were biodegradable and transformed to low molecular weight PAHs under the sulfate-reducing condition. Since these PAHs are known to be biologically degraded under aerobic condition, a serial combination of anaerobic (sulfate reducing) and then aerobic bioremediations could be effective and useful for the soil pollution by petroleum and/or coal derived hydrocarbons.

Effect of Injection Molding Melt Temperatures on PLGA Craniofacial Plate Properties during In Vitro Degradation.

PubMed

de Melo, Liliane Pimenta; Salmoria, Gean Vitor; Fancello, Eduardo Alberto; Roesler, Carlos Rodrigo de Mello

2017-01-01

The purpose of this article is to present mechanical and physicochemical properties during in vitro degradation of PLGA material as craniofacial plates based on different values of injection molded temperatures. Injection molded plates were submitted to in vitro degradation in a thermostat bath at 37 ± 1°C by 16 weeks. The material was removed after 15, 30, 60, and 120 days; then bending stiffness, crystallinity, molecular weights, and viscoelasticity were studied. A significant decrease of molecular weight and mechanical properties over time and a difference in FT-IR after 60 days showed faster degradation of the material in the geometry studied. DSC analysis confirmed that the crystallization occurred, especially in higher melt temperature condition. DMA analysis suggests a greater contribution of the viscous component of higher temperature than lower temperature in thermomechanical behavior. The results suggest that physical-mechanical properties of PLGA plates among degradation differ per injection molding temperatures.

Studies on the oligosaccharide heterogeneity of the isoelectric forms of the lower molecular weight acid phosphatase of frog liver.

PubMed

Kubicz, A; Szalewicz, A; Chrambach, A

1991-01-01

1. The lower molecular weight, heterogeneous acid phosphatase (AcPase) from the frog liver (Rana esculenta) containing AcPase I, II, III and IV was separated into enzymatically active components by isoelectric focusing in an immobilized pH gradient. 2. The blotted enzyme bands were characterized by their different binding patterns obtained with the lectins concanavalin A, wheat germ agglutinin (WGA), Lens culinaris hemagglutinin (LcH) and peanut agglutinin (PNA). 3. In situ neuraminidase treatment reduced the staining intensity of some WGA-bands and increased that of PNA-bands. 4. The finding that AcPases I, II, III and IV differ in their carbohydrate chain composition, together with previous results showing different bioactivities of AcPases III and IV, indicates a correlation between the glycosylation state of enzyme forms and their physiological action.

Molecular and functional characterization of the American cockroach, Periplaneta americana, Rab5: the first exopterygotan low molecular weight ovarian GTPase during oogenesis.

PubMed

Elmogy, Mohamed; Mohamed, Amr A; Tufail, Muhammad; Uno, Tomohide; Takeda, Makio

2017-05-26

The small Rab GTPases are key regulators of membrane vesicle trafficking. Ovaries of Periplaneta americana (Linnaeus) (Blattodea: Blattidae) have small molecular weight GTP/ATP-binding proteins during early and late vitellogenic periods of oogenesis. However, the identification and characterization of the detected proteins have not been yet reported. Herein, we cloned a cDNA encoding Rab5 from the American cockroach, P. americana, ovaries (PamRab5). It comprises 796 bp, encoding a protein of 213 amino acid residues with a predicted molecular weight of 23.5 kDa. PamRab5 exists as a single-copy gene in the P. americana genome, as revealed by Southern blot analysis. An approximate 2.6 kb ovarian mRNA was transcribed especially at high levels in the previtellogenic ovaries, detected by Northern blot analysis. The muscle and head tissues also showed high levels of PamRab5 transcript. PamRab5 protein was localized, via immunofluorescence labeling, to germline-derived cells of the oocytes, very early during oocyte differentiation. Immunoblotting detected a ∼25 kDa signal as a membrane-associated form revealed after application of detergent in the extraction buffer, and 23 kDa as a cytosolic form consistent with the predicted molecular weight from amino acid sequence in different tissues including ovary, muscles and head. The PamRab5 during late vitellogenic periods is required to regulate the endocytotic machinery during oogenesis in this cockroach. This is the first report on Rab5 from a hemimetabolan, and presents an inaugural step in probing the molecular premises of insect oocyte endocytotic trafficking important for oogenesis and embryonic development. © 2017 Institute of Zoology, Chinese Academy of Sciences.

Risk of gastrointestinal bleeding with direct oral anticoagulants: a systematic review and network meta-analysis.

PubMed

Burr, Nick; Lummis, Katie; Sood, Ruchit; Kane, John Samuel; Corp, Aaron; Subramanian, Venkataraman

2017-02-01

Direct oral anticoagulants are increasingly used for a wide range of indications. However, data are conflicting about the risk of major gastrointestinal bleeding with these drugs. We compared the risk of gastrointestinal bleeding with direct oral anticoagulants, warfarin, and low-molecular-weight heparin. For this systematic review and meta-analysis, we searched MEDLINE and Embase from database inception to April 1, 2016, for prospective and retrospective studies that reported the risk of gastrointestinal bleeding with use of a direct oral anticoagulant compared with warfarin or low-molecular-weight heparin for all indications. We also searched the Cochrane Library for systematic reviews and assessment evaluations, the National Health Service (UK) Economic Evaluation Database, and ISI Web of Science for conference abstracts and proceedings (up to April 1, 2016). The primary outcome was the incidence of major gastrointestinal bleeding, with all gastrointestinal bleeding as a secondary outcome. We did a Bayesian network meta-analysis to produce incidence rate ratios (IRRs) with 95% credible intervals (CrIs). We identified 38 eligible articles, of which 31 were included in the primary analysis, including 287 692 patients exposed to 230 090 years of anticoagulant drugs. The risk of major gastrointestinal bleeding with direct oral anticoagulants did not differ from that with warfarin or low-molecular-weight heparin (factor Xa vs warfarin IRR 0·78 [95% CrI 0·47-1·08]; warfarin vs dabigatran 0·88 [0·59-1·36]; factor Xa vs low-molecular-weight heparin 1·02 [0·42-2·70]; and low-molecular-weight heparin vs dabigatran 0·67 [0·20-1·82]). In the secondary analysis, factor Xa inhibitors were associated with a reduced risk of all severities of gastrointestinal bleeding compared with warfarin (0·25 [0.07-0.76]) or dabigatran (0.24 [0.07-0.77]). Our findings show no increase in risk of major gastrointestinal bleeding with direct oral anticoagulants compared with warfarin or low-molecular-weight heparin. These findings support the continued use of direct oral anticoagulants. Leeds Teaching Hospitals Charitable Foundation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fold Prediction of VP24 Protein of Ebola and Marburg Viruses using de novo Fragment Assembly

DTIC Science & Technology

2009-05-15

Watanabe, M., Wiorkiewicz-Kuczera, J., Yin, D., Karplus, M., 1998. All-atom empirical potential for molecular modeling and dynamics studies of...aqueous forms that may be related to its role as a matrix protein. Specifically, the molecular weight of VP24 oligomers was determined using differ...dielectric electrostatic function. Next, the PARAM22 plus generalized Born molecular volume solvation (GBMV2) (Lee et al., 2003) energy (including a 15

Long-term low-molecular-weight heparin and the post-thrombotic syndrome: a systematic review.

PubMed

Hull, Russell D; Liang, Jane; Townshend, Grace

2011-08-01

Post-thrombotic syndrome causes considerable morbidity. The Home-LITE study showed a lower incidence of post-thrombotic syndrome and venous ulcers after 3 months of treating deep vein thrombosis with the low-molecular-weight heparin tinzaparin versus oral anticoagulation. This systematic review examined whether long-term treatment of deep vein thrombosis using low-molecular-weight heparin, rather than oral anticoagulation, reduces development of post-thrombotic syndrome. We identified 9 articles comparing treatment of deep vein thrombosis using long-term low-molecular-weight heparin with any comparator, which reported outcomes relevant to the post-thrombotic syndrome assessed ≥ 3 months post-deep vein thrombosis. Pooled analysis of 2 studies yielded an 87% risk reduction with low-molecular-weight heparin in the incidence of venous ulcers at ≥ 3 months (P = .019). One study showed an overall odds ratio of 0.77 (P = .001) favoring low-molecular-weight heparin for the presence of 8 patient-reported post-thrombotic syndrome signs and symptoms. Pooled analysis of 5 studies showed a risk ratio for low-molecular-weight heparin versus oral anticoagulation of 0.66 (P < .0001) for complete recanalization of thrombosed veins. These results support the lower incidence of post-thrombotic syndrome and venous ulcers observed in Home-LITE. Long-term treatment with low-molecular-weight heparin rather than oral anticoagulation after a deep vein thrombosis may reduce or prevent development of signs and symptoms associated with post-thrombotic syndrome. Post-thrombotic syndrome and associated acute ulcers may develop more rapidly after deep vein thrombosis than previously recognized. Copyright © 2011 Elsevier Inc. All rights reserved.

Mucoadhesion mechanism of chitosan and thiolated chitosan-poly(isobutyl cyanoacrylate) core-shell nanoparticles.

PubMed

Bravo-Osuna, Irene; Vauthier, Christine; Farabollini, Alessandra; Palmieri, Giovanni Filippo; Ponchel, Gilles

2007-04-01

The study is focused on the evaluation of the potential bioadhesive behaviour of chitosan and thiolated chitosan (chitosan-TBA)-coated poly(isobutyl cyanoacrylates) (PIBCA) nanoparticles. Nanoparticles were obtained by radical emulsion polymerisation with chitosan of different molecular weight and with different proportions of chitosan/chitosan-TBA. Mucoadhesion was ex vivo evaluated under static conditions by applying nanoparticle suspensions on rat intestinal mucosal surfaces and evaluating the amount of nanoparticles remaining attached to the mucosa after incubation. The analysis of the results obtained demonstrated that the presence of either chitosan or thiolated chitosan on the PIBCA nanoparticle surface clearly enhanced the mucoadhesion behaviour thanks to non-covalent interactions (ionic interaction and hydrogen bonds) with mucus chains. Both, the molecular weight of chitosan and the proportion of chitosan-TBA in the formulation influenced the nanoparticle hydrodynamic diameter and hence their transport through the mucus layer. Improved interpenetration ability with the mucus chain during the attachment process was suggested for the chitosan of high molecular weight, enhancing the bioadhesiveness of the system. The presence of thiol groups on the nanoparticle surface at high concentration (200 x 10(-6) micromol SH/cm2) increased the mucoadhesion capacity of nanoparticles by forming covalent bonds with the cysteine residues of the mucus glycoproteins.

The effect of self-sorting and co-assembly on the mechanical properties of low molecular weight hydrogels

NASA Astrophysics Data System (ADS)

Colquhoun, Catherine; Draper, Emily R.; Eden, Edward G. B.; Cattoz, Beatrice N.; Morris, Kyle L.; Chen, Lin; McDonald, Tom O.; Terry, Ann E.; Griffiths, Peter C.; Serpell, Louise C.; Adams, Dave J.

2014-10-01

Self-sorting in low molecular weight hydrogels can be achieved using a pH triggered approach. We show here that this method can be used to prepare gels with different types of mechanical properties. Cooperative, disruptive or orthogonal assembled systems can be produced. Gels with interesting behaviour can be also prepared, for example self-sorted gels where delayed switch-on of gelation occurs. By careful choice of gelator, co-assembled structures can also be generated, which leads to synergistic strengthening of the mechanical properties.Self-sorting in low molecular weight hydrogels can be achieved using a pH triggered approach. We show here that this method can be used to prepare gels with different types of mechanical properties. Cooperative, disruptive or orthogonal assembled systems can be produced. Gels with interesting behaviour can be also prepared, for example self-sorted gels where delayed switch-on of gelation occurs. By careful choice of gelator, co-assembled structures can also be generated, which leads to synergistic strengthening of the mechanical properties. Electronic supplementary information (ESI) available: Full experimental and synthetic details for the dipeptides, full experimental descriptions, further NMR, single crystal diffraction data, fXRD data and SANS data. See DOI: 10.1039/c4nr04039b

Comparison of microdialysis sampling perfusion fluid components on the foreign body reaction in rat subcutaneous tissue.

PubMed

Keeler, Geoffrey D; Durdik, Jeannine M; Stenken, Julie A

2014-06-16

Microdialysis sampling is a commonly used technique for collecting solutes from the extracellular space of tissues in laboratory animals and humans. Large molecular weight solutes can be collected using high molecular weight cutoff (MWCO) membranes (100kDa or greater). High MWCO membranes require addition of high molecular weight dextrans or albumin to the perfusion fluid to prevent fluid loss via ultrafiltration. While these perfusion fluid additives are commonly used during microdialysis sampling, the tissue response to the loss of these compounds across the membrane is poorly understood. Tissue reactions to implanted microdialysis sampling probes containing different microdialysis perfusion fluids were compared over a 7-day time period in rats. The base perfusion fluid was Ringer's solution supplemented with either bovine serum albumin (BSA), rat serum albumin (RSA), Dextran-70, or Dextran-500. A significant inflammatory response to Dextran-70 was observed. No differences in the tissue response between BSA and RSA were observed. Among these agents, the BSA, RSA, and Dextran-500 produced a significantly reduced inflammatory response compared to the Dextran-70. This work demonstrates that use of Dextran-70 in microdialysis sampling perfusion fluids should be eliminated and replaced with Dextran-500 or other alternatives. Copyright © 2013 Elsevier B.V. All rights reserved.

Comparative Evaluation of U.S. Brand and Generic Intravenous Sodium Ferric Gluconate Complex in Sucrose Injection: Physicochemical Characterization

PubMed Central

Sun, Dajun; Rouse, Rodney; Patel, Vikram; Wu, Yong; Zheng, Jiwen; Karmakar, Alokita; Patri, Anil K.; Keire, David; Ma, Jia; Jiang, Wenlei

2018-01-01

The objective of this study was to evaluate physicochemical equivalence between brand (i.e., Ferrlecit) and generic sodium ferric gluconate (SFG) in sucrose injection by conducting a series of comparative in vitro characterizations using advanced analytical techniques. The elemental iron and carbon content, thermal properties, viscosity, particle size, zeta potential, sedimentation coefficient, and molecular weight were determined. There was no noticeable difference between brand and generic SFG in sucrose injection for the above physical parameters evaluated, except for the sedimentation coefficient determined by sedimentation velocity analytical ultracentrifugation (SV-AUC) and molecular weight by asymmetric field flow fractionation-multi-angle light scattering (AFFF-MALS). In addition, brand and generic SFG complex products showed comparable molecular weight distributions when determined by gel permeation chromatography (GPC). The observed minor differences between brand and generic SFG, such as sedimentation coefficient, do not impact their biological activities in separate studies of in vitro cellular uptake and rat biodistribution. Coupled with the ongoing clinical study comparing the labile iron level in healthy volunteers, the FDA-funded post-market studies intended to illustrate comprehensive surveillance efforts ensuring safety and efficacy profiles of generic SFG complex in sucrose injection, and also to shed new light on the approval standards on generic parenteral iron colloidal products. PMID:29303999

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. © 2013 Published by Elsevier Ltd.

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…

Enrichment of low-molecular-weight proteins from biofluids for biomarker discovery.

PubMed

Chertov, Oleg; Simpson, John T; Biragyn, Arya; Conrads, Thomas P; Veenstra, Timothy D; Fisher, Robert J

2005-01-01

The dramatic progress in mass spectrometry-based methods of protein identification has triggered a new quest for disease-associated biomarkers. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and its variant surface-enhanced laser desorption/ionization mass spectrometry, provide effective means to explore the less studied information slice of the human serum proteome -- low-molecular-weight proteins and peptides. These low-molecular-weight proteins and peptides are promising for the detection of important biomarkers. Due to the significant experimental problems imposed by high-abundance and high-molecular-weight proteins, it is important to effectively remove these species prior to mass spectrometry analysis of the low-molecular-weight serum and plasma proteomes. In this review, the advantages afforded by recently introduced methods for prefractionation of serum, as they pertain to the detection and identification of biomarkers, will be discussed.

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.

Gene expression profiling in the Cynomolgus macaque Macaca fascicularis shows variation within the normal birth range

PubMed Central

2011-01-01

Background Although an adverse early-life environment has been linked to an increased risk of developing the metabolic syndrome, the molecular mechanisms underlying altered disease susceptibility as well as their relevance to humans are largely unknown. Importantly, emerging evidence suggests that these effects operate within the normal range of birth weights and involve mechanisms of developmental palsticity rather than pathology. Method To explore this further, we utilised a non-human primate model Macaca fascicularis (Cynomolgus macaque) which shares with humans the same progressive history of the metabolic syndrome. Using microarray we compared tissues from neonates in the average birth weight (50-75th centile) to those of lower birth weight (5-25th centile) and studied the effect of different growth trajectories within the normal range on gene expression levels in the umbilical cord, neonatal liver and skeletal muscle. Results We identified 1973 genes which were differentially expressed in the three tissue types between average and low birth weight animals (P < 0.05). Gene ontology analysis identified that these genes were involved in metabolic processes including cellular lipid metabolism, cellular biosynthesis, cellular macromolecule synthesis, cellular nitrogen metabolism, cellular carbohydrate metabolism, cellular catabolism, nucleotide and nucleic acid metabolism, regulation of molecular functions, biological adhesion and development. Conclusion These differences in gene expression levels between animals in the upper and lower percentiles of the normal birth weight range may point towards early life metabolic adaptations that in later life result in differences in disease risk. PMID:21999700

Fossil fuel combined cycle power system

DOEpatents

Labinov, Solomon Davidovich; Armstrong, Timothy Robert; Judkins, Roddie Reagan

2006-10-10

A system for converting fuel energy to electricity includes a reformer for converting a higher molecular weight gas into at least one lower molecular weight gas, at least one turbine to produce electricity from expansion of at least one of the lower molecular weight gases, and at least one fuel cell. The system can further include at least one separation device for substantially dividing the lower molecular weight gases into at least two gas streams prior to the electrochemical oxidization step. A nuclear reactor can be used to supply at least a portion of the heat the required for the chemical conversion process.

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.

Low molecular weight species in humic and fulvic fractions

USGS Publications Warehouse

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

Structure of rigid polymers confined to nanoparticles: Molecular dynamics simulations insight

DOE PAGES

Maskey, Sabina; Lane, J. Matthew D.; Perahia, Dvora; ...

2016-02-04

Nanoparticles (NPs) grafted with organic layers form hybrids able to retain their unique properties through integration into the mesoscopic scale. The organic layer structure and response often determine the functionality of the hybrids on the mesoscopic length scale. Using molecular dynamics (MD) simulations, we probe the conformation of luminescent rigid polymers, dialkyl poly(p-phenylene ethynylene)s (PPE), end-grafted onto a silica nanoparticle in different solvents as the molecular weights and polymer coverages are varied. We find that, in contrast to NP-grafted flexible polymers, the chains are fully extended independent of the solvent. In toluene and decane, which are good solvents, the graftedmore » PPEs chains assume a similar conformation to that observed in dilute solutions. In water, which is a poor solvent for the PPEs, the polymer chains form one large cluster but remain extended. The radial distribution of the chains around the core of the nanoparticle is homogeneous in good solvents, whereas in poor solvents clusters are formed independent of molecular weights and coverages. As a result, the clustering is distinctively different from the response of grafted flexible and semiflexible polymers.« less

Correlation of transarterial transport of various dextrans with their physicochemical properties.

PubMed

Elmalak, O; Lovich, M A; Edelman, E

2000-11-01

Local vascular drug delivery provides elevated concentrations of drug in the target tissue while minimizing systemic side effects. To better characterize local pharmacokinetics we examined the arterial transport of locally applied dextran and dextran derivatives in vivo. Using a two-compartment pharmacokinetic model to correct the measured transmural flux of these compounds for systemic redistribution and elimination as delivered from a photopolymerizable hydrogel surrounding rat carotid arteries, we found that the diffusivities and the transendothelial permeabilities were strongly dependent on molecular weight and charge. For neutral dextrans, the effective diffusive resistance in the media increased with molecular weight approximately 4.1-fold between the molecular weights of 10 and 282 kDa. Similarly, endothelial resistance increased 28-fold over the same molecular weight range. The effective medial diffusive resistance was unaffected by cationic charge as such molecules moved identically to neutral compounds, but increased approximately 40% when dextrans were negatively charged. Transendothelial resistance was 20-fold lower for the cationic dextrans, and 11-fold higher for the anionic dextrans, when both were compared to neutral counterparts. These results suggest that, while low molecular weight drugs will rapidly traverse the arterial wall with the endothelium posing a minimal barrier, the reverse is true for high molecular weight agents. With these data, the deposition and distribution of locally released vasotherapeutic compounds might be predicted based upon chemical properties, such as molecular weight and charge.

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.

Molecular weight dependence of carrier mobility and recombination rate in neat P3HT films

DOE PAGES

Dixon, Alex G.; Visvanathan, Rayshan; Clark, Noel A.; ...

2017-11-02

The microstructure dependence of carrier mobility and recombination rates of neat films of poly 3-hexylthyophene (P3HT) were determined for a range of materials of weight-average molecular weights, Mw, ranging from 14 to 331 kDa. This variation has previously been shown to modify the polymer microstructure, with low molecular weights forming a one-phase, paraffinic-like structure comprised of chain-extended crystallites, and higher molecular weights forming a semicrystalline structure with crystalline domains being embedded in an amorphous matrix. Using Charge Extraction by Linearly Increasing Voltage (CELIV), we show here that the carrier mobility in P3HT devices peaks for materials of Mw = 48more » kDa, and that the recombination rate decreases monotonically with increasing molecular weight. This trend is likely due to the development of a semicrystalline, two-phase structure with increasing Mw, which allows for the spatial separation of holes and electrons into the amorphous and crystalline regions, respectively. This separation leads to decreased recombination.« less

Molecular weight dependence of carrier mobility and recombination rate in neat P3HT films

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

Dixon, Alex G.; Visvanathan, Rayshan; Clark, Noel A.

The microstructure dependence of carrier mobility and recombination rates of neat films of poly 3-hexylthyophene (P3HT) were determined for a range of materials of weight-average molecular weights, Mw, ranging from 14 to 331 kDa. This variation has previously been shown to modify the polymer microstructure, with low molecular weights forming a one-phase, paraffinic-like structure comprised of chain-extended crystallites, and higher molecular weights forming a semicrystalline structure with crystalline domains being embedded in an amorphous matrix. Using Charge Extraction by Linearly Increasing Voltage (CELIV), we show here that the carrier mobility in P3HT devices peaks for materials of Mw = 48more » kDa, and that the recombination rate decreases monotonically with increasing molecular weight. This trend is likely due to the development of a semicrystalline, two-phase structure with increasing Mw, which allows for the spatial separation of holes and electrons into the amorphous and crystalline regions, respectively. This separation leads to decreased recombination.« less

Contrasting effects of photochemical and microbial degradation on Cu(II) binding with fluorescent DOM from different origins.

PubMed

Xu, Huacheng; Guan, Dong-Xing; Zou, Li; Lin, Hui; Guo, Laodong

2018-08-01

Effects of photochemical and microbial degradation on variations in composition and molecular-size of dissolved organic matter (DOM) from different sources (algal and soil) and the subsequent influence on Cu(II) binding were investigated using UV-Vis, fluorescence excitation-emission matrices coupled with parallel factor analysis, flow field-flow fractionation (FlFFF), and metal titration. The degradation processes resulted in an initial rapid decline in the bulk dissolved organic carbon and chromophoric and fluorescent DOM components, followed by a small or little decrease. Specifically, photochemical reaction decreased the aromaticity, humification and apparent molecular weights of all DOM samples, whereas a reverse trend was observed during microbial degradation. The FlFFF fractograms revealed that coagulation of both protein- and humic-like DOM induced an increase in molecular weights for algal-DOM, while the molecular weight enhancement for allochthonous soil samples was mainly attributed to the self-assembly of humic-like components. The Cu(II) binding capacity of algal-derived humic-like and fulvic-like DOM consistently increased during photo- and bio-degradation, while the soil-derived DOM exhibited a slight decline in Cu(II) binding capacity during photo-degradation but a substantial increase during microbial degradation, indicating source- and degradation-dependent metal binding heterogeneities. Pearson correlation analysis demonstrated that the Cu(II) binding potential was mostly related with aromaticity and molecular size for allochthonous soil-derived DOM, but was regulated by both DOM properties and specific degradation processes for autochthonous algal-derived DOM. This study highlighted the coupling role of inherent DOM properties and external environmental processes in regulating metal binding, and provided new insights into metal-DOM interactions and the behavior and fate of DOM-bound metals in aquatic environments. Copyright © 2018 Elsevier Ltd. All rights reserved.

Characterization of durum wheat high molecular weight glutenin subunits Bx20 and By20 sequences by a molecular and proteomic approach.

PubMed

Santagati, Vito Davide; Sestili, Francesco; Lafiandra, Domenico; D'Ovidio, Renato; Rogniaux, Helene; Masci, Stefania

2016-07-01

Wheat high molecular weight glutenin subunit variation is important because of its great influence on glutenin polymer structure, that is related to dough technological properties. Among the different subunits, the pair Bx20 and By20 is known to have a negative effect on quality, but the reasons are not clear: Bx20 has two cysteines, which theoretically make this subunit a chain extender of the glutenin polymer, just like the other Bx subunits, showing four cysteines, two of which should be involved in intra-molecular disulfide bonds. By20 has never been characterized so far at molecular level. Here we report the nucleotide sequences of Bx20 and By20 genes isolated from the durum wheat cultivar 'Lira 45' and the validation of the corresponding deduced amino acid sequences by using MALDI-TOF and LC-MS/MS. Four nucleotide differences were identified in the Bx20 gene with respect to the deduced sequence present in NCBI, causing two amino acid substitutions. For the By20 subunit, nucleotide and amino acid sequences revealed a great similarity to By15, both at gene and protein levels, showing five nucleotide changes generating two amino acid differences. No evidence of post-translational modifications has been found. Hypotheses are formulated in regard to relationships with technological quality. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Low molecular weight salts combined with fluorinated solvents for electrolytes

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

Tikhonov, Konstantin; Yip, Ka Ki; Lin, Tzu-Yuan

2015-11-10

Provided are electrochemical cells and electrolytes used to build such cells. An electrolyte includes at least one salt having a molecular weight less than about 250. Such salts allow forming electrolytes with higher salt concentrations and ensure high conductivity and ion transport in these electrolytes. The low molecular weight salt may have a concentration of at least about 0.5M and may be combined with one or more other salts, such as linear and cyclic imide salts and/or methide salts. The concentration of these additional salts may be less than that of the low molecular weight salt, in some embodiments, twicemore » less. The additional salts may have a molecular weight greater than about 250. The electrolyte may also include one or more fluorinated solvents and may be capable of maintaining single phase solutions at between about -30.degree. C. to about 80.degree. C.« less

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).

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).

Production and structural analysis of the polysaccharide secreted by Trametes (Coriolus) versicolor ATCC 200801.

PubMed

Rau, Udo; Kuenz, Anja; Wray, Victor; Nimtz, Manfred; Wrenger, Julika; Cicek, Hasan

2009-01-01

Trametes versicolor ATCC 200801 secretes 4.1 g L(-1) of exopolysaccharide (EPS) when synthetic minimal medium and low-shear bioreactor cultivation technique are used. Structural and compositional analyses by thin layer chromatography, gas chromatography-mass spectrometry, electrospray ionization tandem mass spectrometry, and nuclear magnetic resonance spectroscopy yielded predominantly glucose and small amounts of galactose, mannose, arabinose, and xylose. The main EPS is composed of beta-1,3/beta-1,6-linked D-glucose molecules which is identical with Schizophyllan but does not possess a triple helical arrangement as secondary structure. Two molar mass fractions were detected by size exclusion chromatography yielding weight-average molecular weights of 4,100 and 2.6 kDa. Protein content varies between 2-3.6% (w/w). The exopolysaccharide is different in the nature of the glycosidic linkage, composition of monosaccharides, protein content, and weight-average molecular weight compared to the well-known polysaccharopeptide (PSP) and polysaccharopeptide Krestin (PSK).

Screening the low molecular weight fraction of human serum using ATR-IR spectroscopy.

PubMed

Bonnier, Franck; Brachet, Guillaume; Duong, Romain; Sojinrin, Tobiloba; Respaud, Renaud; Aubrey, Nicolas; Baker, Matthew J; Byrne, Hugh J; Chourpa, Igor

2016-10-01

Vibrational spectroscopic techniques can detect small variations in molecular content, linked with disease, showing promise for screening and early diagnosis. Biological fluids, particularly blood serum, are potentially valuable for diagnosis purposes. The so-called Low Molecular Weight Fraction (LMWF) contains the associated peptidome and metabolome and has been identified as potentially the most relevant molecular population for disease-associated biomarker research. Although vibrational spectroscopy can deliver a specific chemical fingerprint of the samples, the High Molecular Weight Fraction (HMWF), composed of the most abundant serum proteins, strongly dominates the response and ultimately makes the detection of minor spectral variations a challenging task. Spectroscopic detection of potential serum biomarkers present at relatively low concentrations can be improved using pre-analytical depletion of the HMWF. In the present study, human serum fractionation by centrifugal filtration was used prior to analysis by Attenuated Total Reflection infrared spectroscopy. Using a model sample based on glycine spiked serum, it is demonstrated that the screening of the LMWF can be applied to quantify blinded concentrations up to 50 times lower. Moreover, the approach is easily transferable to different bodily fluids which would support the development of more efficient and suitable clinical protocols exploring vibrational spectroscopy based ex-vivo diagnostic tools. Revealing serum LMWF for spectral serological diagnostic applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Ambient Temperature on Hydrophobic Recovery Behavior of Silicone Rubber Composites

NASA Astrophysics Data System (ADS)

Peng, Xiangyang; Li, Zijian; Zheng, Feng; Zhang, Ni; Huang, Zhen; Fang, Pengfei

A series of silicone rubber samples with different cyclosiloxanes contents have been successfully prepared, and their hydrophobic recovery behaviors and mechanism were investigated in detail. The gas chromatography-mass spectroscopy technique after Soxhlet extraction was utilized to examine the low molecular weight siloxanes in the sample, SEM was used to observe the surface morphology of the silicone rubber influenced by plasma treatment, and contact angle measurement was applied to probe the hydrophobic recovery of the sample surface after plasma treatment at different storage temperatures. The storage time-dependent contact angle of water can be well fitted by the diffusion model calculated from Fick’s second law. The results imply that the hydrophobic recovery of silicone rubber is related to the diffusion of low molecular weight siloxanes, while larger content or higher temperature can induce faster hydrophobic recovery.

Protective effect of dextrans on glucose oxidase denaturation and inactivation.

PubMed

Altikatoglu, Melda; Basaran-Elalmis, Yeliz

2012-08-01

In the present study, the stabilizing effect of dextrans as additives on the denaturation and inactivation of glucose oxidase (GOD) was investigated. Three different molecular weighted dextrans (M(w) 17.5, 75, 188 kD) were used with different concentrations. Dramatically increased enzyme activities were measured after one hour of incubation of enzyme with additives between 25-40°C in water bath. Highest activity value was measured with 75 kDa molecular weighted dextran (in concentration 30% w/v) at pH 5. Dextran as an additive supplied a long shelf-life to the enzyme at 4°C. In the presence of the 75 kDa dextran, the enzyme was more stable and its activity was increased 2.7-fold at 30°C. In addition, dextran protected GOD against inactivation by a n-heptane/aqueous buffer-stirred system.

Structure and properties of polyethylene films used in heavy lift balloons

NASA Technical Reports Server (NTRS)

Khoury, F.; Crissman, J. M.; Fanconi, B. M.; Wagner, H. L.; Botz, L. H.

1985-01-01

The following features of five polyethylene films used by NASA in the construction of heavy lift balloons have been examined: molecular weight, molecular weight distribution, branching, melting behavior, density, surface texture, birefringence, orientation of crystalline regions, unlaxial deformation in the machine and transverse directions, and the effect of sample geometry and strain rate on deformation behavior. The goal of this exploratory study was to determine whether there are significant differences in any of the above mentioned features, or combination of features between the films. The acquisition of such information is a first step towards determining whether there are any specific correlations between film characteristics and the incidence of catastrophic failure of balloons during ascent through the troposphere. This exploratory study has resulted in the identification of similarities and differences between various features of the films.

Evaporative purification to produce highly monodisperse polymers: Application to polystyrene for n =3 -13 and quantification of Tg from oligomer to polymer

NASA Astrophysics Data System (ADS)

Zhu, S.; Chai, Y.; Forrest, J. A.

2017-07-01

We demonstrate the use of selective thermal evaporation to separate and purify small molecular weight polymers into highly monodisperse polymers over an extended range of polymerization index. By exploiting the calculated dependence of polymer vapor pressure on polymerization index N and temperature T , we can isolate individual components (N -mers) of an initially polydisperse mixture. To demonstrate this ability, we consider polystyrene samples of Mw=600 g/mol and Mw=890 g/mol with narrow molecular weight distributions, as well as a Mw=1200 g/mol sample with a broader distribution. In each case we are able to separate the sample into milligram quantities of many different components. Using this technique, we have been able to isolate N -mers from 3 to 13. We use differential scanning calorimetry to measure the Tg values of these components, and find that the components have the same Tg values independent of the Mw or polydispersity of the sample they originate from. We find that even initially narrow molecular weight distributions have many different components whose Tg values can differ by more than 50 K. Calculations suggest the isolated components have Mw/Mn values less than 1.001 and through a second iteration of the process could become as low as 1.000 003. The measured Tg values for the N -mers as well as large N polymers are well described by a simple relation derived from the Fox equation for the Tg of mixtures.

Preparation of Low Molecular Weight Chondroitin Sulfates, Screening of a High Anti-Complement Capacity of Low Molecular Weight Chondroitin Sulfate and Its Biological Activity Studies in Attenuating Osteoarthritis.

PubMed

Li, Lian; Li, Yan; Feng, Danyang; Xu, Linghua; Yin, Fengxin; Zang, Hengchang; Liu, Chunhui; Wang, Fengshan

2016-10-11

Chondroitin sulfate (CS) plays important roles in the complement system. However, the CS structure is complicated due to different sources and the number and positions of sulfate groups. The objective of this study was to prepare different low molecular weight chondroitin sulfates (LMWCSs) and to investigate the biological activity in anti-complement capacity. A series of LMWCSs was prepared from different sources and characterized by ultraviolet-visible (UV) spectroscopy, high-performance liquid chromatography (HPLC), size exclusion chromatography-multiangle laser light scattering (SEC-MALLS) and nuclear magnetic resonance (NMR) spectroscopy. Hemolytic, anti-complement 3 deposition capacity and cell viability assays were carried out to investigate the biological activities in vitro. The results showed that LMWCS prepared from shark cartilage with the oxidative degradation method (LMWCS-S-O) had the best anti-complement capacity. LMWCS-S-O could inhibit the alternative pathway of the complement system and protect chondrocytes from cell death. The attenuating effect of LMWCS-S-O on Osteoarthritis (OA) was investigated by destabilization of the medial meniscus (DMM) model in vivo. Functional wind-up, histological and C5b-9 analyses were used to evaluate the treatment effect on the OA model. In vivo results showed that LMWCS-S-O could attenuate OA. LMWCS-S-O with a high content of ΔDi-2,6diS and ΔDi-6S could be used for attenuating OA through regulating the complement system.

Formation of porous HPCL/LPCL/HA scaffolds with supercritical CO2 gas foaming method.

PubMed

Moghadam, M Zahedi; Hassanajili, Sh; Esmaeilzadeh, F; Ayatollahi, M; Ahmadi, M

2017-05-01

Scaffold is a 3D porous structure that is made of different materials, such as synthetic and natural polymers. It plays the role of a synthetic extracellular matrix and permits adhesion, proliferation and differentiation of the cells. Porosity and pore size are the important factors for any 3D scaffold used in bone tissue engineering. In this study, porous scaffolds were prepared by adding hydroxyapatite (HA) nanoparticles as filler to the polymeric matrix of polycaprolactone (PCL) blends with two different molecular weight by using supercritical CO 2 (ScCO 2 ) foaming method. The effect of different parameters such as CO 2 pressure, ratios of the polymers and amount of the filler on the scaffold properties was investigated. The results showed that porosity increased with increment of pressure and decreased with increasing the ratio of the high molecular weight PCL to the low molecular weight PCL in the scaffolds and also HA content. Optimum condition for obtaining adequate porous scaffold of HPCL/LPCL/HA occurred at 140bar and 45°C. The physical and mechanical properties of the prepared scaffolds were characterized using DSC, XRD, FTIR, SEM, contact angle and compression test. By analyzing the results of these tests, optimum sample for cell culture was selected. The biocompatibility of the selected HPCL/LPCL/HA scaffold (HPCL/LPCL 60/40 containing 2.5% HA) was assessed in vitro by using human mesenchymal stem cells (hMSCs). Copyright © 2016 Elsevier Ltd. All rights reserved.

Formulation and Evaluation of Tramadol hydrochloride Rectal Suppositories.

PubMed

Saleem, M A; Taher, M; Sanaullah, S; Najmuddin, M; Ali, Javed; Humaira, S; Roshan, S

2008-09-01

Rectal suppositories of tramadol hydrochloride were prepared using different bases and polymers like PEG, cocoa butter, agar and the effect of different additives on in vitro release of tramadol hydrochloride was studied. The agar-based suppositories were non-disintegrating/non-dissolving, whereas PEGs were disintegrating/dissolving and cocoa butter were melting suppositories. All the prepared suppositories were evaluated for various physical parameters like weight variation, drug content and hardness. The PEG and cocoa butter suppositories were evaluated for macromelting range, disintegration and liquefaction time. In vitro release study was performed by USP type I apparatus. The prepared suppositories were within the permissible range of all physical parameters. In vitro drug release was in the order of PEG>Agar>cocoa butter. Addition of PVP, HPMC in agar suppositories retards the release. The mechanism of drug release was diffusion controlled and follows first order kinetics. The results suggested that blends of PEG of low molecular weight (1000) with high molecular weight (4000 and 6000) in different percentage and agar in 10% w/w as base used to formulate rapid release suppositories. The sustained release suppositories can be prepared by addition of PVP, HPMC in agar-based suppositories and by use of cocoa butter as base.

In situ upgrading of whole biomass to biofuel precursors with low average molecular weight and acidity by the use of zeolite mixture

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

Ben, Haoxi; Huang, Fang; Li, Liwei

2015-09-09

The pyrolysis of whole biomass—pine wood and bark—with mordenite (M), beta (β) and Y zeolites has been examined at 600°C. The GPC results indicated that the pyrolysis oils upgraded by Y and β zeolites have a very low average molecular weight range (70–170 g mol –1). Several NMR methods have been employed to characterize the whole portion of pyrolysis products. After the use of these two zeolites (Y and β), the two main products from the pyrolysis of cellulose—levoglucosan and HMF—were eliminated; this indicates a significant deoxygenation process. When a mixture of zeolites (Y and M) was used, the upgradedmore » pyrolysis oil exhibited advantages provided by both zeolites; this pyrolysis oil represents a biofuel precursor that has a very low average molecular weight and a relatively low acidity. Finally, this study opens up a new way to upgrade pyrolysis oils by employing mixtures of different functional zeolites to produce biofuel/biochemical precursors from whole biomass.« less

Nanoscale Motion of Soft Nanoparticles in Unentangled and Entangled Polymer Matrices

NASA Astrophysics Data System (ADS)

Lungova, M.; Krutyeva, M.; Pyckhout-Hintzen, W.; Wischnewski, A.; Monkenbusch, M.; Allgaier, J.; Ohl, M.; Sharp, M.; Richter, D.

2016-09-01

We have studied the motion of polyhedral oligomeric silsesquioxane (POSS) nanoparticles modified with poly(ethylene glycol) (PEG) arms immersed in PEG matrices of different molecular weight. Employing neutron spin echo spectroscopy in combination with pulsed field gradient (PFG) NMR we found the following. (i) For entangled matrices the center of mass mean square displacement (MSD) of the PEG-POSS particles is subdiffusive following a t0.56 power law. (ii) The diffusion coefficient as well as the crossover to Fickian diffusion is independent of the matrix molecular weight and takes place as soon as the center of mass has moved a distance corresponding to the particle radius—this holds also for unentangled hosts. (iii) For the entangled matrices Rubinstein's scaling theory is validated; however, the numbers indicate that beyond Rouse friction the entanglement constraints appear to strongly increase the effective friction even on the nanoparticle length scale imposing a caveat on the interpretation of microrheological experiments. (iv) The oligomer decorated PEG-POSS particles exhibit the dynamics of a Gaussian star with an internal viscosity that rises with an increase of the host molecular weight.

Study of PEG Tether Length of Pegylated-Lipid Sensing Films in QCM Odor Sensors

NASA Astrophysics Data System (ADS)

Wyszynski, Bartosz; Somboon, Pakpum; Nakamoto, Takamichi

Odor sensing system using quartz crystal microbalance (QCM) sensor array and pattern recognition technique has been for a long time an important research topic. Research of novel sensing materials for QCM odor sensors is vital for realization of artificial olfaction and related devices such as odor recorder. Herein we study quartz crystal microbalance (QCM, 20 MHz, AT-cut) sensors coated with lipopolymers with polyethylene glycol (PEG) as a tether. The tether's molecular weights were 1000, 2000 and 5000. In addition, we fabricated QCM sensors coated with PEGs of molecular weights 1000, 2000 and 4000. The fabricated sensors' properties were evaluated during experiments of exposures to vapors of alcohols, esters and acids. From the obtained results it is clear that the tether's length (molecular weight) is an important factor influencing the resulting material's sensing properties. Sensititivity patterns of the lipopolymeric sensors were clealrly different from the ones for respective polymers. The obtained sensors seem to have a good capability to discriminate among odor samples according to the functional group of an odorant.

Optimization of process parameters for the production of collagen peptides from fish skin (Epinephelus malabaricus) using response surface methodology and its characterization.

PubMed

Hema, G S; Joshy, C G; Shyni, K; Chatterjee, Niladri S; Ninan, George; Mathew, Suseela

2017-02-01

The study optimized the hydrolysis conditions for the production of fish collagen peptides from skin of Malabar grouper ( Epinephelus malabaricus ) using response surface methodology. The hydrolysis was done with enzymes pepsin, papain and protease from bovine pancreas. Effects of process parameters viz: pH, temperature, enzyme substrate ratio and hydrolysis time of the three different enzymes on degree of hydrolysis were investigated. The optimum response of degree of hydrolysis was estimated to be 10, 20 and 28% respectively for pepsin, papain and protease. The functional properties of the product developed were analysed which showed changes in the properties from proteins to peptides. SDS-PAGE combined with MALDI TOF method was successfully applied to determine the molecular weight distribution of the hydrolysate. The electrophoretic pattern indicated that the molecular weights of peptides formed due to hydrolysis were nearly 2 kDa. MALDI TOF spectral analysis showed the developed hydrolysate contains peptides having molecular weight in the range below 2 kDa.

Dextran as a fast resorbable and mechanically stiff coating for flexible neural probes

NASA Astrophysics Data System (ADS)

Kil, D.; Brancato, L.; Puers, R.

2017-11-01

In this paper we report on the use of dextran as a temporary, fast dissolving stiff coating for flexible neural probes. Although polymer-based neural implants offer several advantages, compared to their rigid silicon counterparts, they pose significant challenges during implantation. Due to their extreme flexibility, they have the tendency to buckle under the axial load applied during insertion. The structural stiffness of the implants can be temporarily increased by applying a bioresorbable dextran coating which eases the penetration of neural tissue. For this application three types of dextran with different molecular weights are analysed. The dissolution rate of the coatings is reported as well as the increased bending stiffness resulting from the dextran coating of Parylene C neural probes. Based on these findings the dissolution rate can be linked to parameters such as molecular weight, coating thickness and the surface area exposed to the dissolution medium. The mechanical characterization yields information on how the structural stiffness of neural probes can be tuned by varying the dextran’s molecular weight and coating thickness.

Low-molecular-weight heparin biosimilars: potential implications for clinical practice. Australian Low-Molecular-Weight Heparin Biosimilar Working Group (ALBW).

PubMed

Nandurkar, H; Chong, B; Salem, H; Gallus, A; Ferro, V; McKinnon, R

2014-05-01

A working group of clinicians and scientists was formed to review the clinical considerations for use of low-molecular-weight heparin (LMWH) biosimilars. LMWH are biological molecules of significant complexity; the full complexity of chemical structure is still to be elucidated. LMWH biosimilars are products that are biologically similar to their reference product and rely on clinical data from a reference product to establish safety and efficacy. The complex nature of LMWH molecules means that it is uncertain whether a LMWH biosimilar is chemically identical to its reference product; this introduces the possibility of differences in activity and immunogenicity. The challenge for regulators and clinicians is to evaluate the level of evidence required to demonstrate that a LMWH is sufficiently similar to the reference product. The consensus opinion of the working group is that prior to clinical use a LMWH biosimilar should have proven efficacy and safety, similar to the reference product with prospective studies, which should be confirmed with a proactive post-marketing pharmacovigilance programme. © 2014 The Authors; Internal Medicine Journal © 2014 Royal Australasian College of Physicians.

Drop-on-demand drop formation of polyethylene oxide solutions

NASA Astrophysics Data System (ADS)

Yan, Xuejia; Carr, Wallace W.; Dong, Hongming

2011-10-01

The dynamics of drop-on-demand (DOD) drop formation for solutions containing polyethylene oxide (PEO) have been studied experimentally. Using a piezoelectrical actuated inkjet printhead with the nozzle orifice diameter of 53 μm, experiments were conducted for a series of PEO aqueous solutions with molecular weights ranging from 14 to 1000 kg/mol, polydispersity from 1.02 to 2.5, and concentrations from 0.005 to 10 wt. %. The addition of a small amount of PEO can have a significant effect on the DOD drop formation process, increasing breakup time, decreasing primary drop speed, and decreasing the number of satellite drops in some cases. The effects depend on both molecular weight and concentration. At lower molecular weights (14 and 35 kg/mol), the effect of PEO over the dilute solution regime is insignificant even at concentrations large enough that the solution does not fall in the dilute regime. As PEO molecular weight increased, the effects became significant. For monodispersed PEO solutions, breakup time and primary drop speed closely correlated with effective relaxation time but not for polydispersed PEO. Effective relaxation time depended greatly on molecular weight distribution. Viscosity-average molecular weight, used in calculating effective relaxation time for polydispersed PEO solutions, did not adequately account for high molecular fractions in the molecular weight distribution of the polydispersed PEOs. A mixture rule was developed to calculate the effective relaxation times for aqueous solutions containing mixtures of monodispersed PEO, and breakup times and primary drop speeds correlated well with effective relaxation times. For our experiments, DOD drop formation was limited to Deborah number ≲ 23.

Overview of the TREC 2009 Chemical IR Track

DTIC Science & Technology

2009-11-01

several classes have been identified. 3 methods for controlling molecular weight of polyhydroxyalkanoate organic, high molecular weight We are a group of...researchers in an university/company. We want to start a project and, before starting, we want more informations about polyhydroxyalkanoate and about...methods for controlling molecular weight of polyhydroxyalkanoate constituted of units containing residue of phenyl-, thienyl-, or cyclohexyl-structure

Isolation and Characterization of a Toxic Moiety of Low Molecular Weight from Clostridium botulinum Type A

PubMed Central

Gerwing, Julia; Dolman, Claude E.; Bains, Hardial S.

1965-01-01

Gerwing, Julia (The University of British Columbia, Vancouver, B.C., Canada), Claude E. Dolman, and Hardial S. Bains. Isolation and characterization of a toxic moiety of low molecular weight from Clostridium botulinum type A. J. Bacteriol. 89:1383–1386. 1965.—A toxic moiety of low molecular weight has been isolated from a type A strain of Clostridium botulinum, by a method involving ammonium sulfate precipitation and elution through diethylaminoethyl cellulose at pH 5.6. By means of electrophoresis and ultracentrifugation, the toxic substance was shown to be homogeneous; a molecular weight of 12,200 was calculated. Images PMID:14293025

Mass spectrometric characterization of membrane integral low molecular weight proteins from photosystem II in barley etioplasts.

PubMed

Plöscher, Matthias; Granvogl, Bernhard; Zoryan, Mikael; Reisinger, Veronika; Eichacker, Lutz Andreas

2009-02-01

In Photosystem II (PSII), a high number of plastid encoded and membrane integral low molecular weight proteins smaller than 10 kDa, the proteins PsbE, F, H, I, J, K, L, M, N, Tc, Z and the nuclear encoded PsbW, X, Y1, Y2 proteins have been described. Here we show that all low molecular weight proteins of PSII already accumulate in the etioplast membrane fraction in darkness, whereas PsaI and PsaJ of photosystem I (PSI) represent the only low molecular weight proteins that do not accumulate in darkness. We found by BN-PAGE separation of membrane protein complexes and selective MS that the accumulation of one-helix proteins from PSII is light independent and occurs in etioplasts. In contrast, in chloroplasts isolated from light-grown plants, low molecular weight proteins were found to specifically accumulate in PSI and II complexes. Our results demonstrate how plants grown in darkness prepare for the induction of chlorophyll dependent photosystem assembly upon light perception. We anticipate that our investigation will provide the essential means for the analysis of protein assembly in any membrane utilizing low molecular weight protein subunits.

The Presence Of Strange Males' Odor Induces Behavioral Responses And Elevated Levels Of Low Molecular Weight Proteins Excreted In The Urine Of Mature Water Vole Males (Arvicola amphibius L).

PubMed

Nazarova, Galina G; Proskurniak, Lyudmila P; Yuzhik, Ekaterina I

2016-03-01

We hypothesized that low molecular weight urinary proteins play a role in male-male chemical communication in the water vole, Arvicola ampibius L. We studied the effect of placing soiled litter from strange males into the cage of another sexually mature male on the intensity of its digging and scattering, urination on the litter, and alteration in the levels of low molecular weight proteins (15-25 kDa) excreted in the urine before and after 4 days of exposure as determined by chip electrophoresis. The intensity of digging and scattering was positively correlated with levels of testosterone in serum of males exposed to strange male odors (r = 0.56; P < 0.01), as well as with the concentration of low molecular weight proteins in the donor's urine (r = 0.52, P < 0.05). At the end of the experiment, the level of low molecular weight protein in excreted urine was elevated in the males exposed to the strange male's litter. These results highlight the importance of quantitative inter-individual variation of low molecular weight urinary proteins in the modulation of the physiology and behavior of conspecifics.

Effect of whey protein hydrolysates with different molecular weight on fatigue induced by swimming exercise in mice.

PubMed

Liu, Jing; Wang, Xinxia; Zhao, Zheng

2014-01-15

In order to improve the antioxidant and anti-fatigue capacities of whey protein for wider utilization, it was hydrolyzed by chymotrypsin (EC 3.4.21.1) to produce whey protein hydrolysate (WPH). Fractions of WPH with different molecular weight (MW) were separated by ultrafiltration. Kunming mice in various treatment groups were orally administered (1.5 g kg(-1) body weight) whey protein isolate (WPI), WPH or WPHs with different MW (<5, 5-10, 10-30 or >30 kDa) for 6 weeks to explore whether different MW fractions of WPH affected mice fatigue. Compared with the control group (orally administered 9 g kg(-1) saline) or the WPI group, low-MW (<10 kDa) WPH groups showed prolonged swimming time (P < 0.05) and had higher concentrations (P < 0.05) of glucose, non-esterfied fatty acid, liver glycogen, superoxide dismutase and glutathione peroxidase and lower concentration of lactate. Low-MW (<10 kDa) WPHs had higher hydroxyl- and α,α-diphenyl-β-picrylhydrazyl-scavenging abilities and ferrous-chelating capacity than WPI. The results proved that low-MW (<10 kDa) WPHs with higher anti-fatigue capacity showed higher free radical-scavenging and ferrous-chelating activities. © 2013 Society of Chemical Industry.

Plastic degradation by thermophilic Bacillus sp. BCBT21 isolated from composting agricultural residual in Vietnam

NASA Astrophysics Data System (ADS)

Dang, Thi Cam Ha; Thang Nguyen, Dang; Thai, Hoang; Chinh Nguyen, Thuy; Thu Hien Tran, Thi; Le, Viet Hung; Huynh Nguyen, Van; Bach Tran, Xuan; Phuong Thao Pham, Thi; Giang Nguyen, Truong; Nguyen, Quang Trung

2018-03-01

Three different kinds of plastic bags HL, VHL, and VN1 with different chemical nature were degraded by a novel thermophilic bacterial strain isolated from composting agricultural residual in Vietnam in shaking liquid medium at 55 °C after 30 d. The new strain was classified in the Bacillus genus by morphological property and sequence of partial 16Sr RNA coding gene and named as Bacillus sp. BCBT21. This strain could produce extracellular hydrolase enzymes including lipase, CMCase, xylanase, chitinase, and protease with different level of activity in the same media. After a 30-d treatment at 55 °C with Bacillus sp. BCBT21, all characteristics including properties and morphology of treated plastic bags had been significantly changed. The weight loss, structure and surface morphology of these bags as well as the change in the average molecular weight of VHL bag were detected. Especially, the average molecular weight of VHL bag was significantly reduced from 205 000 to 116 760. New metabolites from the treated bags indicated biodegradation occurring with the different pathways. This finding suggests that there is high potential to develop an effective integrated method for plastic bags degradation by a combination of extracellular enzymes from bacteria and fungi existing in the composting process.

Antarctic snow: metals bound to high molecular weight dissolved organic matter.

PubMed

Calace, Nicoletta; Nardi, Elisa; Pietroletti, Marco; Bartolucci, Eugenia; Pietrantonio, Massimiliana; Cremisini, Carlo

2017-05-01

In this paper we studied some heavy metals (Cu, Zn, Cd, Pb, As, U) probably associated to high molecular weight organic compounds present in the Antarctic snow. Snow-pit samples were collected and analysed for high molecular weight fraction and heavy metals bound to them by means of ultrafiltration treatment. High molecular weight dissolved organic matter (HMW-DOM) recovered by ultrafiltration showed a dissolved organic carbon concentration (HMW-DOC) of about 18-83% of the total dissolved organic carbon measured in Antarctic snow. The characterisation of HMW-DOM fraction evidenced an ageing of organic compounds going from surface layers to the deepest ones with a shift from aliphatic compounds and proteins/amino sugars to more high unsaturated character and less nitrogen content. The heavy metals associated to HMW-DOM fraction follows the order: Zn > Cu > Pb > Cd ∼ As ∼ U. The percentage fraction of metals bound to HMW-DOM respect to total metal content follows the order: Cu > Pb > Zn, Cd in agreement with humic substance binding ability (Irwing-William series). Going down to depth of trench, all metals except arsenic, showed a high concentration peak corresponding to 2.0-2.5 m layer. This result was attributed to particular structural characteristic of organic matter able to form different type of complexes (1:1, 1:2, 1:n) with metals. Copyright © 2017 Elsevier Ltd. All rights reserved.

Higher Molecular Weight Leads to Improved Photoresponsivity Charge Transport and Interfacial Ordering in a Narrow Bandgap Semiconducting Polymer

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

M Tong; S Cho; J Rogers

2011-12-31

Increasing the molecular weight of the low-bandgap semiconducting copolymer, poly[(4,4-didoecyldithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl], Si-PDTBT, from 9 kDa to 38 kDa improves both photoresponsivity and charge transport properties dramatically. The photocurrent measured under steady state conditions is 20 times larger in the higher molecular weight polymer (HM{sub n} Si-PDTBT). Different decays of polarization memory in transient photoinduced spectroscopy measurements are consistent with more mobile photoexcitations in HM{sub n} Si-PDTBT relative to the lower molecular weight counterpart (LM{sub n} Si-PDTBT). Analysis of the current-voltage characteristics of field effect transistors reveals an increase in the mobility by a factor of 700 for HM{sub n} Si-PDTBT. Nearmore » edge X-ray absorption fine structure (NEXAFS) spectroscopy and grazing incidence small angle X-ray scattering (GISAXS) measurements demonstrate that LM{sub n} Si-PDTBT forms a disordered morphology throughout the depth of the film, whereas HM{sub n} Si-PDTBT exhibits pronounced {pi}-{pi} stacking in an edge-on configuration near the substrate interface. Increased interchain overlap between polymers in the edge-on configuration in HM{sub n} Si-PDTBT results in the higher carrier mobility. The improved optical response, transport mobility, and interfacial ordering highlight the subtle role that the degree of polymerization plays on the optoelectronic properties of conjugated polymer based organic semiconductors.« less

Characterization of the nitrogen compounds released during yeast autolysis in a model wine system.

PubMed

Martínez-Rodríguez, A J; Polo, M C

2000-04-01

The nitrogen composition of wines aged with yeast for a long period of time, as in the case of sparkling wines, depends on the composition of the base wine and on the compounds released by the yeast. In this paper, the release of the different classes of nitrogen compounds during autolysis of one of the strains of yeast used in the manufacture of sparkling wines has been studied. The yeast, Saccharomyces bayanus, was suspended in a model wine buffer, pH 3.0 and 10% ethanol, and incubated at 30 degrees C. Samples of the autolysate were taken after 4, 24, 48, 72, 168, and 360 h of autolysis. An electrophoretic and chromatographic study was conducted of the proteins, peptides with molecular weights higher and lower than 700 Da, and amino acids released during the autolysis. Using SDS-PAGE, it was observed that it was predominantly polypeptides with molecular weights lower than 10 000 that were released. Through HPLC of the fraction lower than 10 000 Da, it was observed that it is polypeptides with molecular weights of between 10 000 and 700 Da that are released first and that these later break up to give rise to peptides with molecular weights lower than 700 Da, which in turn break down into amino acids. This indicates that the nature of the nitrogen compounds present in wines aged with yeast depends on the aging time, being less polymerized as the aging time increases.

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

PubMed Central

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

2016-01-01

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

Effects of Molecular Structure in Macroscopic Mechanical Properties of an Advanced Polymer (LARC(sup TM)-SI)

NASA Technical Reports Server (NTRS)

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

2004-01-01

Mechanical testing of an advanced polymer resin with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The elastic properties, inelastic elongation behavior, and notched tensile strength all as a function of molecular weight and test temperature were determined. 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.

Characterization of organic matter in cloud waters sampled at the puy de Dôme mountain using FT-ICR-MS

NASA Astrophysics Data System (ADS)

Bianco, A.; Chaumerliac, N.; Vaitilingom, M.; Deguillaume, L.; Bridoux, M. C.

2017-12-01

The chemical composition of organic matter in cloud water is highly complex. The organic species result from their dissolution from the gas phase or from the soluble fraction of the particle phase. They are also produced by aqueous phase reactivity. Several low molecular weight organic species have been quantified such as aldehydes and carboxylic acids. Recently, amino acids were also detected in cloud water and their presence is related to the presence of microorganisms. Compounds presenting similarities with high molecular weight organic substances or HULIS found in aerosols were also observed in clouds. Overall, these studies mainly focused on individual compounds or functional groups rather than the complex mixture at the molecular level. This study presents a non-targeted approach to characterize the organic matter in clouds. Samples were collected at the puy de Dôme Mountain (France). Two cloud water samples (June & July 2016) were analyzed using high resolution mass spectrometry (ESI-FT-ICR-MS 9.4T). A reversed solid phase extraction (SPE) procedure was performed to concentrate dissolved organic matter components. Composer (v.1.5.3) software was used to filter the mass spectral data, recalibrate externally the dataset and calculate all possible formulas for detected anions. The first cloud sample (June) resulted from air mass coming from the North (North Sea) while the second one (July) resulted from air mass coming from the West (Atlantic Ocean). Thus, both cloud events derived from marine air masses but were characterized by different hydrogen peroxide concentration and dissolved organic carbon content and were sampled at different periods during the day. Elemental compositions of 6487 and 3284 unique molecular species were identified in each sample. Nitrogen-containing compounds (CHNO compounds), sulfur-containing compounds (CHOS & CHNOS compounds) and other oxygen-containing compounds (CHO compounds) with molecular weights up to 800 Da were detected. The main class is CHNO (53% for both samples) while sulfur-containing compounds represent for the two samples respectively 21 & 14% of the total assigned molecular formulas. CHO compounds molecular formulas are respectively 25 & 32%. Among the two samples, only 2490 molecular formulas were found common to the two samples.

Characterisation of physico-mechanical properties and degradation potential of calcium alginate beads for use in embolisation.

PubMed

Forster, Richard E J; Thürmer, Frank; Wallrapp, Christine; Lloyd, Andrew W; Macfarlane, Wendy; Phillips, Gary J; Boutrand, Jean-Pierre; Lewis, Andrew L

2010-07-01

High molecular weight alginate beads with 59% mannuronic acid content or 68% guluronic acid were prepared using a droplet generator and crosslinked in calcium chloride. The alginate beads were compared to current embolisation microspheres for compressibility and monitored over 12 weeks for size and weight change at 37 degrees C in low volumes of ringers solutions. A sheep uterine model was used to analyse bead degradation and inflammatory response over 12 weeks. Both the in vitro and in vivo data show good delivery, with a compressibility similar to current embolic beads. In vitro, swelling was noted almost immediately and after 12 weeks the first signs of degradation were noted. No difference was noted in vivo. This study has shown that high molecular weight alginate gel beads were well tolerated by the body, but beads associated with induced thrombi were susceptible to inflammatory cell infiltration. The beads were shown to be easy to handle and were still observable after 3 months in vivo. The beads were robust enough to be delivered through a 2.7 Fr microcatheter. This study has demonstrated that high molecular weight, high purity alginate bead can be considered as semi-permanent embolisation beads, with the potential to bioresorb over time.

Extraction and physicochemical characterization of broiler (Gallus gallus domesticus) skin gelatin compared to commercial bovine gelatin.

PubMed

Aykin-Dinçer, E; Koç, A; Erbas, M

2017-09-01

Gelatin was extracted from broiler (Gallus gallus domesticus) skins and analyzed to compare its physicochemical properties with those of commercial bovine gelatin. The average yield of broiler skin gelatin was 6.5% on a wet weight basis. Broiler skin gelatin had more α1-and α2-chains than β-chain and contained high molecular weight (γ-chain) polymers. Glycine was the dominant amino acid in broiler skin gelatin (20.26%), followed by proline (Pro) (15.12%) then hydroxyproline (Hyp) (11.36%). Compared to commercial bovine gelatin, broiler skin gelatin had less total imino acids (Pro and Hyp) but a higher (33.65 vs. 31.38°C) melting temperature (P < 0.01). The differences in physical properties between the broiler and commercial bovine gelatins appeared to be associated with differences in their amino acid composition and molecular weight distribution. The sensory evaluation results revealed that broiler skin gelatin could be a potential alternative to commercial bovine gelatin, useful in various food products. © 2017 Poultry Science Association Inc.

Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances

USGS Publications Warehouse

Chin, Y.-P.; Aiken, G.; O'Loughlin, E.

1994-01-01

The number- and weight-averaged molecular weights of a number of aquatic fulvic acids, a commercial humic acid, and unfractionated organic matter from four natural water samples were measured by high-pressure size exclusion chromatography (HPSEC). Molecular weights determined in this manner compared favorably with those values reported in the literature. Both recent literature values and our data indicate that these substances are smaller and less polydisperse than previously believed. Moreover, the molecular weights of the organic matter from three of the four natural water samples compared favorably to the fulvic acid samples extracted from similar environments. Bulk spectroscopic properties of the fulvic substances such as molar absorptivity at 280 nm and the E4/E6 ratio were also measured. A strong correlation was observed between molar absorptivity, total aromaticity, and the weight average molecular weights of all the humic substances. This observation suggests that bulk spectroscopic properties can be used to quickly estimate the size of humic substances and their aromatic contents. Both parameters are important with respect to understanding humic substance mobility and their propensity to react with both organic and inorganic pollutants. ?? 1994 American Chemical Society.

High-resolution crystal structure of copper amine oxidase from Arthrobacter globiformis: assignment of bound diatomic molecules as O2.

PubMed

Murakawa, Takeshi; Hayashi, Hideyuki; Sunami, Tomoko; Kurihara, Kazuo; Tamada, Taro; Kuroki, Ryota; Suzuki, Mamoru; Tanizawa, Katsuyuki; Okajima, Toshihide

2013-12-01

The crystal structure of a copper amine oxidase from Arthrobacter globiformis was determined at 1.08 Å resolution with the use of low-molecular-weight polyethylene glycol (LMW PEG; average molecular weight ∼200) as a cryoprotectant. The final crystallographic R factor and Rfree were 13.0 and 15.0%, respectively. Several molecules of LMW PEG were found to occupy cavities in the protein interior, including the active site, which resulted in a marked reduction in the overall B factor and consequently led to a subatomic resolution structure for a relatively large protein with a monomer molecular weight of ∼70,000. About 40% of the presumed H atoms were observed as clear electron densities in the Fo - Fc difference map. Multiple minor conformers were also identified for many residues. Anisotropic displacement fluctuations were evaluated in the active site, which contains a post-translationally derived quinone cofactor and a Cu atom. Furthermore, diatomic molecules, most likely to be molecular oxygen, are bound to the protein, one of which is located in a region that had previously been proposed as an entry route for the dioxygen substrate from the central cavity of the dimer interface to the active site.

Marine Collagen Peptides from the Skin of Nile Tilapia (Oreochromis niloticus): Characterization and Wound Healing Evaluation

PubMed Central

Hu, Zhang; Yang, Ping; Zhou, Chunxia; Li, Sidong; Hong, Pengzhi

2017-01-01

Burns can cause tremendous economic problems associated with irreparable harm to patients and their families. To characterize marine collagen peptides (MCPs) from the skin of Nile tilapia (Oreochromis niloticus), molecular weight distribution and amino acid composition of MCPs were determined, and Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemical structure. Meanwhile, to evaluate the wound healing activity, in vitro and in vivo experiments were carried out. The results showed that MCPs prepared from the skin of Nile tilapia by composite enzymatic hydrolysis were composed of polypeptides with different molecular weights and the contents of polypeptides with molecular weights of less than 5 kDa accounted for 99.14%. From the amino acid composition, the majority of residues, accounting for over 58% of the total residues in MCPs, were hydrophilic. FTIR indicated that the main molecular conformations inside MCPs were random coil. In vitro scratch assay showed that there were significant effects on the scratch closure by the treatment of MCPs with the concentration of 50.0 μg/mL. In the experiments of deep partial-thickness scald wound in rabbits, MCPs could enhance the process of wound healing. Therefore, MCPs from the skin of Nile tilapia (O. niloticus) have promising applications in wound care. PMID:28358307

Lead-binding capacity of calcium pectates with different molecular weight.

PubMed

Khotimchenko, Maksim; Makarova, Ksenia; Khozhaenko, Elena; Kovalev, Valeri

2017-04-01

Nowadays, heavy metal contamination of environment is considered as a serious threat to public health because of toxicity of these pollutants and the lack of effective materials with metal-binding properties. Some biopolymers such as pectins were proposed for removal of metal ions from industrial water disposals. Chemical structure of pectins is quite variable and substantially affects their metal binding properties. In this work, relationship between molecular weight and Pb(II)-binding capacity of calcium pectates was investigated in a batch sorption system. The results showed that all pectate samples are able to form complexes with Pb(II) ions. The effects of contact time, pH of the media and equilibrium metal concentration on metal-binding process were tested in experiments. The equilibrium time min required for uptake of Pb(II) by pectate compounds was found to be 60min. Langmuir and Freundlich models were applied for description of interactions between pectates and metal ions. Binding capacity of low molecular pectate was highest among all the samples tested. Langmuir model was figured out to be the best fit within the whole range of pH values. These results demonstrate that calcium pectate with low molecular weight is more promising agent for elimination of Pb(II) ions from contaminated wastewaters. Copyright © 2017 Elsevier B.V. All rights reserved.

Marine Collagen Peptides from the Skin of Nile Tilapia (Oreochromis niloticus): Characterization and Wound Healing Evaluation.

PubMed

Hu, Zhang; Yang, Ping; Zhou, Chunxia; Li, Sidong; Hong, Pengzhi

2017-03-30

Burns can cause tremendous economic problems associated with irreparable harm to patients and their families. To characterize marine collagen peptides (MCPs) from the skin of Nile tilapia ( Oreochromis niloticus ), molecular weight distribution and amino acid composition of MCPs were determined, and Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemical structure. Meanwhile, to evaluate the wound healing activity, in vitro and in vivo experiments were carried out. The results showed that MCPs prepared from the skin of Nile tilapia by composite enzymatic hydrolysis were composed of polypeptides with different molecular weights and the contents of polypeptides with molecular weights of less than 5 kDa accounted for 99.14%. From the amino acid composition, the majority of residues, accounting for over 58% of the total residues in MCPs, were hydrophilic. FTIR indicated that the main molecular conformations inside MCPs were random coil. In vitro scratch assay showed that there were significant effects on the scratch closure by the treatment of MCPs with the concentration of 50.0 μg/mL. In the experiments of deep partial-thickness scald wound in rabbits, MCPs could enhance the process of wound healing. Therefore, MCPs from the skin of Nile tilapia ( O. niloticus ) have promising applications in wound care.

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.

Effects of sources of protein and enzyme supplementation on protein digestibility and chyme characteristics in broilers.

PubMed

Yu, B; Lee, T T T; Chiou, P W S

2002-07-01

1. The purpose of this study was to evaluate the effects of protein source and enzyme supplementation on protein digestibility and chyme characteristics in broilers. 2. One hundred and twenty growing (13 d old) and 60 finishing (34 d old) Arbor Acre strain commercial male broilers were selected and placed into individual metabolic cages. 3. The experiment was a 5 x 2 factorial arrangement with 5 different sources of protein: casein, fish meal, soybean meal (SBM), soy protein concentrate (SPC), maize gluten meal (MGM) and two levels of protease (bromelain), 0 and 65 CDU/kg diets. 4. The diets were iso-nitrogenous and semi-purified, with Cr2O3 as an indicator for determination of ileal digestibility and chyme characteristics. 5. Apparent ileal protein digestibility (AIPD) in both growing and finishing chickens was highest on the casein diet, followed by fish meal, SBM, SPC and MGM. 6. Enzyme inclusion did not improve protein digestibility, but significantly decreased the digesta pH value in the gizzard and increased pH in the ileum in the 3-week-old broilers. 7. The digesta pH values in the gizzard and duodenum were significantly lower in the SBM and fish meal groups compared with the other protein groups. The molecular weight distribution pattern of the soluble protein in the chyme of the gastrointestinal (GI) segments showed a similar trend, regardless of the enzyme inclusion or the stage of growth. 8. The molecular weight profile of soluble protein changed dynamically in the casein fed broilers from the gizzard to ileum and the low molecular weight proteins, < 7 kDa, reached maximum levels at the ileum. The molecular weight profile of the soluble protein in the SBM and SPC changed between the jejunum and the ileum and in the intermediate molecular soluble protein weight (7 to 10 kDa) was significantly decreased. This indicated that the hydrolysis process began from the middle to the posterior end of the small intestine. 9. Similar profiles were also shown with fish meal protein. The pattern of distribution, however, did not show any prominent change in the GI segments of the MGM group. 10. The pepsin, trypsin and chymotrypsin protease activity in the gizzard and duodenum were highest in the casein group and lowest in the MGM group as compared with the other protein groups. 11. The rate change in the patterns of molecular weight distribution in soluble protein and the digestive enzyme activity provide indications of the partial digestibility of different protein sources. The exogenous enzyme, bromelain, did not show any beneficial effect on protein digestion.

Penicillin-binding proteins in Haemophilus influenzae.

PubMed Central

Makover, S D; Wright, R; Telep, E

1981-01-01

The penicillin-binding proteins (PBPs) of Haemophilus influenzae were studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Eight major PBPs, ranging in molecular weights from 90,000 to 27,000, were detected. The pattern of molecular weights was different from that determined fro Escherichia coli or Pseudomonas aeruginosa. A study on the binding of several beta-lactam antibodies to the PBPs at their minimal inhibitory concentrations and at lower and higher concentrations revealed that all had highest affinity for PBP 2. Amdinocillin (mecillinam) was an exception; it had highest affinity for PBP 3. The morphological effects of several penicillins, cephalosporins, and amdinocillin on H. influenzae were similar to those reported for E. coli. Images PMID:6972731

Structural features of Fab fragments of rheumatoid factor IgM-RF in solution

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

Volkov, V. V., E-mail: vvo@ns.crys.ras.ru; Lapuk, V. A.; Shtykova, E. V.

The structural features of the Fab fragments of monoclonal (Waldenstroem's disease) immunoglobulin M (IgM) and rheumatoid immunoglobulin M (IgM-RF) were studied by a complex of methods, including small-angle X-ray scattering (SAXS), electron spin resonance (ESR), and mass spectrometry (MS). The Fab-RF fragment was demonstrated to be much more flexible in the region of interdomain contacts, the molecular weights and the shapes of the Fab and Fab-RF macromolecules in solution being only slightly different. According to the ESR data, the rotational correlation time for a spin label introduced into the peptide sequence for Fab is twice as large as that formore » Fab-RF (21{+-}2 and 11{+-}1 ns, respectively), whereas the molecular weights of these fragments differ by only 0.5% (mass-spectrometric data), which correlates with the results of molecular-shape modeling by small-angle X-ray scattering. The conclusion about the higher flexibility of the Fab-RF fragment contributes to an understanding of the specificity of interactions between the rheumatoid factor and the antigens of the own organism.« less

A RCT study of Rivaroxaban, low-molecular-weight heparin, and sequential medication regimens for the prevention of venous thrombosis after internal fixation of hip fracture.

PubMed

Tang, Yilun; Wang, Kunzheng; Shi, Zhibin; Yang, Pei; Dang, Xiaoqian

2017-08-01

The guidelines for the prevention of venous thromboembolism in orthopedic surgeries have reached a consensus on the postoperative conventional anticoagulation. However, the choice of anticoagulant drugs is yet controversial. The use of the drug rivaroxaban is expensive. Since the compliance of patients with low-molecular-weight heparin is considerably low, a cost-effective, efficacious and convenient anticoagulant program is essential. The present study investigated the efficacy, safety, patient compliance, and cost-effectiveness of low-molecular-weight heparin with sequential Rivaroxaban anticoagulant therapy in patients with a hip fracture, following internal fixation. A total of 287 patients with hip fractures were randomized into three groups: Rivaroxaban alone, Enoxaparin alone, and Enoxaparin followed by Rivaroxaban. The primary endpoint was the incidence of postoperative VTE, whereas the secondary endpoints were the compliance and treatment costs. Adverse reactions included bleeding and wound complications. The incidences of VTE were 5.21%, 14.74%, and 10.42% in the Rivaroxaban, low-molecular-weight heparin, and sequential therapy groups, respectively. The VTE-related mortality rates were 0%, 1.05%, and 1.04%. The average hospital stay was 12±8,15±7, and 11±5d, whereas the compliance rates of the three groups were 82.3%, 71.6%, and 88.5%, respectively. The incidences of adverse incisions were 14.6%, 4.2%, and 6.3% for the three groups examined. The effects and the incidence of postoperative bleeding in the treatment of low-molecular-weight heparin followed by Rivaroxaban did not differ significantly from that of Rivaroxaban alone. However, the postoperative drainage, the cost of treatment and the incidence of VTE reduced significantly, whereas the incidences of adverse incisions and the patient compliance were increased. ChiCTR-INR-17010495. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Origins and fates of PAHs in the coastal marine environment off San Diego (California)

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

Zeng, E.Y.; Yu, C.C.; Vista, C.L.

1995-12-31

The main inputs of anthropogenic hydrocarbons to the coastal marine environment off San Diego include the Point Lama wastewater outfall (City of San Diego), Tijuana River (crossing the boarder between the US and Mexico) and several storm drains along the coastline and in San Diego Bay, inadvertent spills, and aerial deposition. Samples collected (in January and June 1994) from the Point Loma wastewater effluent, Tijuana River runoff, and microlayer, sediment trap, and surface sediment at several locations adjacent to the Point Loma outfall, entrance of Tijuana River into the ocean, and San Diego Bay (near the San Diego International Airport)more » were analyzed to determine the origins and fates of PAHs in the coastal marine environment. Alkyl homologue distributions (AHDS) for naphthalene indicated a mainly petrogenic origin for low molecular-weight PAHs in the effluent, water column particle, and sediment near the outfall. Parent compound distributions (PCDS) for PAHs with molecular weights 178, 202, 228, 252, 276, and 278 showed combustion-related inputs in the water column particle and sediment, especially for mid to high molecular-weight PAHs. PAHs with molecular weight equal to or higher than 252 were not detected in the effluent. The compositions of PAHs were substantially different in the effluent particulates and filtrates, implying a great deal about the fates of PAHs from the outfall and their bioaccumulation by organisms. PAHs detected in Tijuana River runoff had similar AHDs and PCDs to those of the Point Loma outfall effluent. AHDs in the San Diego Bay sediment exhibited marked seasonal variation; low molecular-weight PAHs were significantly combustion-related in January and more petrogenic in June. Microlayer samples generally contained dominant combustion-generated PAHs. The impact of the wastewater outfall discharge on the nearby water column and sediment appeared compromised by other non-point source inputs.« less

40 CFR Table A-7 to Subpart A of... - Data Elements That Are Inputs to Emission Equations and for Which the Reporting Deadline Is March...

Code of Federal Regulations, 2012 CFR

2012-07-01

... mass balance equation. K 98.116(b) Only annual production by product from each EAF (No CEMS). K 98.116... carbon content values, molecular weights for gaseous feedstocks, molecular weights for gaseous products... of gas flared, average molecular weight, carbon content of the flare, and molar volume conversion...

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.

Antiedematogenic and antioxidant properties of high molecular weight protein sub-fraction of Calotropis procera latex in rat.

PubMed

Chaudhary, Priyanka; de Araújo Viana, Carolina; Ramos, Marcio V; Kumar, Vijay L

2015-03-01

The aim was to evaluate the effect of high molecular weight protein fraction of Calotropis procera latex on edema formation and oxidative stress in carrageenan-induced paw inflammation. A sub-plantar injection of carrageenan was given to induce edema in the hind paw of the rat. The inhibitory effect of high molecular weight protein fraction of C. procera latex was evaluated following intravenous administration (5 and 25 mg/kg body weight) and was compared with that of diclofenac given orally (5 mg/kg). The levels of reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARS) and myeloperoxidase (MPO) were measured in the inflamed paw tissue at the end of the study. The high molecular weight protein fraction obtained from the latex of C. procera produced a dose-dependent inhibition of edema formation that was accompanied by normalization of levels of oxidative stress markers (GSH and TBARS) and MPO, a marker for neutrophils in the paw tissue. The high molecular weight protein fraction of C. procera latex ameliorates acute inflammation in the paw through its antioxidant effect.

Protein modification in the post-mating spermatophore of the signal crayfish Pacifastacus leniusculus: insight into the tyrosine phosphorylation in a non-motile spermatozoon.

PubMed

Niksirat, Hamid; Vancová, Marie; Andersson, Liselotte; James, Peter; Kouba, Antonín; Kozák, Pavel

2016-09-01

After mating, spermatophores of signal crayfish are stored on the body of the female for a period before fertilization. This study compared the post-mating protein profile and pattern of protein tyrosine phosphorylation of the signal crayfish spermatophore to that of the freshly ejaculated spermatophore and found substantial differences. Two major bands of tyrosine-phosphorylated proteins of molecular weights 10 and 50kDa were observed in the freshly ejaculated spermatophore of the signal crayfish. While the tyrosine-phosphorylated protein band with molecular weight 10kDa was formed by protein(s) of similar pH, the band with molecular weight of 50kDa consisted of proteins of varying pH. In the post-mating spermatophore, the band with molecular weight of 50kDa was not detected, and an increase in the level of protein tyrosine phosphorylation was observed in the 10kDa band. The microtubular radial arms of the spermatozoon showed a positive reaction to an anti-tyrosine antibody conjugated with gold particles in both the freshly ejaculated and post-mating spermatophores. In conclusion, the male gamete of the signal crayfish undergoes molecular modification during post-mating storage on the body of the female including changes in the level of protein expression and protein tyrosine phosphorylation. Structural similarity of the radial arms in the crayfish immotile spermatozoon with flagellum, which is the main site of protein tyrosine phosphorylation in the mammalian motile spermatozoa, raises questions regarding evolution and function of such organelles across the animal kingdom that must be addressed in the future studies. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of Pectin Molecular Weight Changes on the Structure, Dynamics, and Polysaccharide Interactions of Primary Cell Walls of Arabidopsis thaliana: Insights from Solid-State NMR.

PubMed

Phyo, Pyae; Wang, Tuo; Xiao, Chaowen; Anderson, Charles T; Hong, Mei

2017-09-11

Significant cellulose-pectin interactions in plant cell walls have been reported recently based on 2D 13 C solid-state NMR spectra of intact cell walls, but how these interactions affect cell growth has not been probed. Here, we characterize two Arabidopsis thaliana lines with altered expression of the POLYGALACTURONASE INVOLVED IN EXPANSION1 (PGX1) gene, which encodes a polygalacturonase that cleaves homogalacturonan (HG). PGX1 AT plants overexpress PGX1, have HG with lower molecular weight, and grow larger, whereas pgx1-2 knockout plants have HG with higher molecular weight and grow smaller. Quantitative 13 C solid-state NMR spectra show that PGX1 AT cell walls have lower galacturonic acid and xylose contents and higher HG methyl esterification than controls, whereas high molecular weight pgx1-2 walls have similar galacturonic acid content and methyl esterification as controls. 1 H-transferred 13 C INEPT spectra indicate that the interfibrillar HG backbones are more aggregated whereas the RG-I side chains are more dispersed in PGX1 AT cell walls than in pgx1-2 walls. In contrast, the pectins that are close to cellulose become more mobile and have weaker cross peaks with cellulose in PGX1 AT walls than in pgx1-2 walls. Together, these results show that polygalacturonase-mediated plant growth is accompanied by increased esterification and decreased cross-linking of HG, increased aggregation of interfibrillar HG, and weaker HG-cellulose interactions. These structural and dynamical differences give molecular insights into how pectins influence wall dynamics during cell growth.

The Effect of the Melt Viscosity and Impregnation of a Film on the Mechanical Properties of Thermoplastic Composites

PubMed Central

Kim, Jong Won; Lee, Joon Seok

2016-01-01

Generally, to produce film-type thermoplastic composites with good mechanical properties, high-performance reinforcement films are used. In this case, films used as a matrix are difficult to impregnate into tow due to their high melt viscosity and high molecular weight. To solve the problem, in this paper, three polypropylene (PP) films with different melt viscosities were used separately to produce film-type thermoplastic composites. A film with a low melt viscosity was stacked so that tow was impregnated first and a film with a higher melt viscosity was then stacked to produce the composite. Four different composites were produced by regulating the pressure rising time. The thickness, density, fiber volume fraction (Vf), and void content (Vc) were analyzed to identify the physical properties and compare them in terms of film stacking types. The thermal properties were identified by using differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). The tensile property, flexural property, interlaminar shear strength (ILSS), and scanning electron microscopy (SEM) were performed to identify the mechanical properties. For the films with low molecular weight, impregnation could be completed fast but showed low strength. Additionally, the films with high molecular weight completed impregnation slowly but showed high strength. Therefore, appropriate films should be used considering the forming process time and their mechanical properties to produce film-type composites. PMID:28773572

Oxidative polymerization of lignins by laccase in water-acetone mixture.

PubMed

Fiţigău, Ionița Firuța; Peter, Francisc; Boeriu, Carmen Gabriela

2013-01-01

The enzymatic oxidative polymerization of five technical lignins with different molecular properties, i.e. Soda Grass/Wheat straw Lignin, Organosolv Hardwood Lignin, Soda Wheat straw Lignin, Alkali pretreated Wheat straw Lignin, and Kraft Softwood was studied. All lignins were previously fractionated by acetone/water 50:50 (v/v) and the laccase-catalyzed polymerization of the low molecular weight fractions (Mw < 4000 g/mol) was carried out in the same solvent system. Reactivity of lignin substrates in laccase-catalyzed reactions was determined by monitoring the oxygen consumption. The oxidation reactions in 50% acetone in water mixture proceed with high rate for all tested lignins. Polymerization products were analyzed by size exclusion chromatography, FT-IR, and (31)P-NMR and evidence of important lignin modifications after incubation with laccase. Lignin polymers with higher molecular weight (Mw up to 17500 g/mol) were obtained. The obtained polymers have potential for applications in bioplastics, adhesives and as polymeric dispersants.

Design of magnetic polyplexes taken up efficiently by dendritic cell for enhanced DNA vaccine delivery.

PubMed

Nawwab Al-Deen, F M; Selomulya, C; Kong, Y Y; Xiang, S D; Ma, C; Coppel, R L; Plebanski, M

2014-02-01

Dendritic cells (DC) targeting vaccines require high efficiency for uptake, followed by DC activation and maturation. We used magnetic vectors comprising polyethylenimine (PEI)-coated superparamagnetic iron oxide nanoparticles, with hyaluronic acid (HA) of different molecular weights (<10 and 900 kDa) to reduce cytotoxicity and to facilitate endocytosis of particles into DCs via specific surface receptors. DNA encoding Plasmodium yoelii merozoite surface protein 1-19 and a plasmid encoding yellow fluorescent gene were added to the magnetic complexes with various % charge ratios of HA: PEI. The presence of magnetic fields significantly enhanced DC transfection and maturation. Vectors containing a high-molecular-weight HA with 100% charge ratio of HA: PEI yielded a better transfection efficiency than others. This phenomenon was attributed to their longer molecular chains and higher mucoadhesive properties aiding DNA condensation and stability. Insights gained should improve the design of more effective DNA vaccine delivery systems.

Improved synthesis with high yield and increased molecular weight of poly(alpha,beta-malic acid) by direct polycondensation.

PubMed

Kajiyama, Tetsuto; Kobayashi, Hisatoshi; Taguchi, Tetsushi; Kataoka, Kazunori; Tanaka, Junzo

2004-01-01

The development of synthetic biodegradable polymers, such as poly(alpha-hydroxy acid), is particularly important for constructing medical devices, including scaffolds and sutures, and has attracted growing interest in the biomedical field. Here, we report a novel approach to preparing high molecular weight poly(malic acid) (HMW--PMA) as a biodegradable and bioabsorbable water-soluble polymer. We investigated in detail the reaction conditions for the simple direct polycondensation of l-malic acid, including the reaction times, temperatures, and catalysts. The molecular weight of synthesized alpha,beta-PMA is dependent on both the reaction temperature and time. The optimum reaction condition to obtain alpha,beta-PMA by direct polycondensation using tin(II) chloride as a catalyst was thus determined to be 110 degrees C for 45 h with a molecular weight of 5300. The method for alpha,beta-PMA synthesis established here will facilitate production of alpha,beta-PMA of various molecular weights, which may have a potential utility as biomaterials.

Reorganization of low-molecular-weight fraction of plasma proteins in the annual cycle of cyprinidae.

PubMed

Andreeva, A M; Lamas, N E; Serebryakova, M V; Ryabtseva, I P; Bolshakov, V V

2015-02-01

Reorganization of the low-molecular-weight fraction of cyprinid plasma was analyzed using various electrophoretic techniques (disc electrophoresis, electrophoresis in polyacrylamide concentration gradient, in polyacrylamide with urea, and in SDS-polyacrylamide). The study revealed coordinated changes in the low-molecular-weight protein fractions with seasonal dynamics and related reproductive rhythms of fishes. We used cultured species of the Cyprinidae family with sequenced genomes for the detection of these interrelations in fresh-water and anadromous cyprinid species. The common features of organization of fish low-molecular-weight plasma protein fractions made it possible to make reliable identification of their proteins. MALDI mass-spectrometry analysis revealed the presence of the same proteins (hemopexin, apolipoproteins, and serpins) in the low-molecular-weight plasma fraction in wild species and cultured species with sequenced genomes (carp, zebrafish). It is found that the proteins of the first two classes are organized as complexes made of protein oligomers. Stoichiometry of these complexes changes in concordance with the seasonal and reproductive rhythms.

Dielectric properties of organic solvents from non-polarizable molecular dynamics simulation with electronic continuum model and density functional theory.

PubMed

Lee, Sanghun; Park, Sung Soo

2011-11-03

Dielectric constants of electrolytic organic solvents are calculated employing nonpolarizable Molecular Dynamics simulation with Electronic Continuum (MDEC) model and Density Functional Theory. The molecular polarizabilities are obtained by the B3LYP/6-311++G(d,p) level of theory to estimate high-frequency refractive indices while the densities and dipole moment fluctuations are computed using nonpolarizable MD simulations. The dielectric constants reproduced from these procedures are evaluated to provide a reliable approach for estimating the experimental data. An additional feature, two representative solvents which have similar molecular weights but are different dielectric properties, i.e., ethyl methyl carbonate and propylene carbonate, are compared using MD simulations and the distinctly different dielectric behaviors are observed at short times as well as at long times.

Extended Solution Gate OFET-based Biosensor for Label-free Glial Fibrillary Acidic Protein Detection with Polyethylene Glycol-Containing Bioreceptor Layer.

PubMed

Song, Jian; Dailey, Jennifer; Li, Hui; Jang, Hyun-June; Zhang, Pengfei; Wang, Jeff Tza-Huei; Everett, Allen D; Katz, Howard E

2017-05-25

A novel organic field effect transistor (OFET) -based biosensor is described for label-free glial fibrillary acidic protein (GFAP) detection. We report the first use of an extended solution gate structure where the sensing area and the organic semiconductor are separated, and a reference electrode is not needed. Different molecular weight polyethylene glycols (PEGs) are mixed into the bio-receptor layer to help extend the Debye screening length. The drain current change was significantly increased with the help of higher molecular weight PEGs, as they are known to reduce the dielectric constant. We also investigated the sensing performance under different gate voltage (V g ). The sensitivity increased after we decreased V g from -5 V to -2 V, because the lower V g is much closer to the OFET threshold voltage and the influence of attached negatively charged proteins become more apparent. Finally, the selectivity experiments toward different interferents were performed. The stability and selectivity are promising for clinical applications.

Tissue proteomics of the low-molecular weight proteome using an integrated cLC-ESI-QTOFMS approach.

PubMed

Alvarez, MeiHwa Tanielle Bench; Shah, Dipti Jigar; Thulin, Craig D; Graves, Steven W

2013-05-01

Analysis of the protein/peptide composition of tissue has provided meaningful insights into tissue biology and even disease mechanisms. However, little has been published regarding top down methods to investigate lower molecular weight (MW) (500-5000 Da) species in tissue. Here, we evaluate a tissue proteomics approach involving tissue homogenization followed by depletion of large proteins and then cLC-MS (where c stands for capillary) analysis to interrogate the low MW/low abundance tissue proteome. In the development of this method, sheep heart, lung, liver, kidney, and spleen were surveyed to test our ability to observe tissue differences. After categorical tissue differences were demonstrated, a detailed study of this method's reproducibility was undertaken to determine whether or not it is suitable for analyzing more subtle differences in the abundance of small proteins and peptides. Our results suggest that this method should be useful in exploring the low MW proteome of tissues. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Injection Molding Melt Temperatures on PLGA Craniofacial Plate Properties during In Vitro Degradation

PubMed Central

Fancello, Eduardo Alberto

2017-01-01

The purpose of this article is to present mechanical and physicochemical properties during in vitro degradation of PLGA material as craniofacial plates based on different values of injection molded temperatures. Injection molded plates were submitted to in vitro degradation in a thermostat bath at 37 ± 1°C by 16 weeks. The material was removed after 15, 30, 60, and 120 days; then bending stiffness, crystallinity, molecular weights, and viscoelasticity were studied. A significant decrease of molecular weight and mechanical properties over time and a difference in FT-IR after 60 days showed faster degradation of the material in the geometry studied. DSC analysis confirmed that the crystallization occurred, especially in higher melt temperature condition. DMA analysis suggests a greater contribution of the viscous component of higher temperature than lower temperature in thermomechanical behavior. The results suggest that physical-mechanical properties of PLGA plates among degradation differ per injection molding temperatures. PMID:29056968

An Efficient Method for Genomic DNA Extraction from Different Molluscs Species

PubMed Central

Pereira, Jorge C.; Chaves, Raquel; Bastos, Estela; Leitão, Alexandra; Guedes-Pinto, Henrique

2011-01-01

The selection of a DNA extraction method is a critical step when subsequent analysis depends on the DNA quality and quantity. Unlike mammals, for which several capable DNA extraction methods have been developed, for molluscs the availability of optimized genomic DNA extraction protocols is clearly insufficient. Several aspects such as animal physiology, the type (e.g., adductor muscle or gills) or quantity of tissue, can explain the lack of efficiency (quality and yield) in molluscs genomic DNA extraction procedure. In an attempt to overcome these aspects, this work describes an efficient method for molluscs genomic DNA extraction that was tested in several species from different orders: Veneridae, Ostreidae, Anomiidae, Cardiidae (Bivalvia) and Muricidae (Gastropoda), with different weight sample tissues. The isolated DNA was of high molecular weight with high yield and purity, even with reduced quantities of tissue. Moreover, the genomic DNA isolated, demonstrated to be suitable for several downstream molecular techniques, such as PCR sequencing among others. PMID:22174651

Quantitative characterization of solid epoxy resins using comprehensive two dimensional liquid chromatography coupled with electrospray ionization-time of flight mass spectrometry.

PubMed

Julka, Samir; Cortes, Hernan; Harfmann, Robert; Bell, Bruce; Schweizer-Theobaldt, Andreas; Pursch, Matthias; Mondello, Luigi; Maynard, Shawn; West, David

2009-06-01

A comprehensive multidimensional liquid chromatography system coupled to Electrospray Ionization-Mass Spectrometry (LCxLC-ESI-MS) was developed for detailed characterization and quantitation of solid epoxy resin components. The two orthogonal modes of separation selected were size exclusion chromatography (SEC) in the first dimension and liquid chromatography at critical conditions (LCCC) in the second dimension. Different components present in the solid epoxy resins were separated and quantitated for the first time based on the functional groups and molecular weight heterogeneity. Coupling LCxLC separations with mass spectrometry enabled the identification of components resolved in the two-dimensional space. Several different functional group families of compounds were separated and identified, including epoxy-epoxy and epoxy-alpha-glycol functional oligomers, and their individual molecular weight ranges were determined. Repeatability obtained ranged from 0.5% for the main product to 21% for oligomers at the 0.4% concentration level.

Role of modifiers for analytical-scale supercritical fluid extraction of environmental samples

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

Langenfeld, J.J.; Hawthorne, S.B.; Miller, D.J.

1994-03-15

Supercritical fluid extraction (SFE) using eight different CO[sub 2] + organic modifier mixtures and one ternary mixture (CO[sub 2] + methanol/toluene) at two different concentrations (1 and 10% v/v) was performed on two certified reference materials including polychlorinated biphenyls (PCBs) from river sediment and polycyclic aromatic hydrocarbons (PAHs) from urban air particulate matter. The modifier identity was more important than modifier concentration for increasing extraction efficiencies. Acidic/basic modifiers including methanol, acetic acid, and aniline greatly enhanced the extraction of PCBs. Low molecular weight PAHs were best extracted with modifiers including aniline, acetic acid, acetonitrile, methanol/toluene, hexane, and diethylamine. In contrast,more » modifiers capable of dipole-induced dipole interactions and [pi]-[pi] interactions such as toluene, diethylamine, and methylene chloride were the best modifiers to use for SFE of high molecular weight PAHs from air particulates. 37 refs., 6 tabs.« less

Influence of micromixer characteristics on polydispersity index of block copolymers synthesized in continuous flow microreactors.

PubMed

Rosenfeld, Carine; Serra, Christophe; Brochon, Cyril; Hadziioannou, Georges

2008-10-01

The influence of interdigital multilamination micromixer characteristics on monomer conversions, molecular weights and especially on the polydispersity index of block copolymers synthesized continuously in two microtube reactors is investigated. The micromixers are used to mix, before copolymerization, a polymer solution with different viscosities and the second monomer. Different geometries of micromixer (number of microchannels, characteristic lengths) have been studied. It was found that polydispersity indices of the copolymers follow a linear relationship with the Reynolds number in the micromixer, represented by a form factor. Thus, beside the operating conditions (nature of the first block and comonomer flow rate), the choice of the micromixer geometry and dimension is essential to control the copolymerization in terms of molecular weights and polydispersity indices. This linear correlation allows the prediction of copolymer features. It can also be a new method to optimize existing micromixers or design other geometries so that mixing could be more efficient.

Adsorption of polyethyleneimine and polymethacrylic acid onto synthesized hematite.

PubMed

Chibowski, S; Patkowski, J; Grzadka, E

2009-01-01

An influence of different functional groups of polymer, its molecular weight, polydispersity ratio (M(w)/M(n)) and presence of impurities on its adsorption in different pH values (3, 6 and 9) onto synthesized hematite (Fe(2)O(3)) was measured. A structure of adsorbed macromolecules of PMA and PEI was obtained according to S-F theory. Two polymers were used: polymethacrylic acid (PMA) of 6500 and 75,100 molecular weight as well as polyethyleneimine (PEI) 25,000 commercial and fractionated. Electrokinetic properties of the interface oxide-polymer solution (surface charge density and zeta potential) were also measured as well as adsorption layer thicknesses (with use of viscosimetric measurements). Obtained data show, that all above-mentioned factors do influence not only the adsorption process itself but also a surface charge, zeta potential and structure of adsorbed polymer layers on polymer/hematite interface.

Intercalation of sulfonated melamine formaldehyde polycondensates into a hydrocalumite LDH structure

NASA Astrophysics Data System (ADS)

von Hoessle, F.; Plank, J.; Leroux, F.

2015-05-01

A series of sulfonated melamine formaldehyde (SMF) polycondensates possessing different anionic charge amounts and molecular weights was synthesized and incorporated into a hydrocalumite type layered double hydroxide structure using the rehydration method. For this purpose, tricalcium aluminate was dispersed in water and hydrated in the presence of these polymers. Defined inorganic-organic hybrid materials were obtained as reaction products. All SMF polymers tested intercalated readily into the hydrocalumite structure, independent of their different molecular weights (chain lengths) and anionic charge amounts. X-ray diffraction revealed typical patterns for weakly ordered, highly polymer loaded LDH materials which was confirmed via elemental analysis and thermogravimetry. IR spectroscopy suggests that the SMF polymers are interleaved between the [Ca2Al(OH)6]+ main sheets via electrostatic interaction, and that no chemical bond between the host matrix and the guest anion is formed. The SMF polymers well ensconced within the LDH structure exhibit significantly slower thermal degradation.

A structured understanding of cellobiohydrolase I binding to poplar lignin fractions after dilute acid pretreatment

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

Yao, Lan; Yoo, Chang Geun; Meng, Xianzhi

Background: Cellulase adsorption to lignin is considered a cost barrier for bioethanol production; however, its detailed association mechanism is still not fully understood. In this study, two natural poplar variants with high and low sugar release performance were selected as the low and high recalcitrant raw materials (named L and H, respectively). Three different lignin fractions were extracted using ethanol, followed by p-dioxane and then cellulase treatment from the dilute acid pretreated poplar solids (fraction 1, 2, and 3, respectively).Results: Each lignin fraction had different physicochemical properties. Ethanol-extracted lignin had the lowest weight average molecular weight, while the molecular weightsmore » for the other two lignin fractions were similar. 31P NMR analysis revealed that lignin fraction with higher molecular weight contained more aliphatic hydroxyl groups and less phenolic hydroxyl groups. Semi-quantitative analysis by 2D HSQC NMR indicated that the lignin fractions isolated from the natural variants had different contents of syringyl (S), guaiacyl (G) and interunit linkages. Lignin extracted by ethanol contained the largest amount of S units, the smallest amounts of G and p-hydroxybenzoate (PB) subunits, while the contents of these lignin subunits in the other two lignin fractions were similar. The lignin fraction obtained after cellulase treatment was primarily comprised of β-O-4 linkages with small amounts of β-5 and β–β linkages. The binding strength of these three lignin fractions obtained by Langmuir equations were in the order of L1 > L3 > L2 for the low recalcitrance poplar and H1 > H2 > H3 for the high recalcitrance poplar.Conclusions: Overall, adsorption ability of lignin was correlated with the sugar release of poplar. Structural features of lignin were associated with its binding to CBH. For natural poplar variants, lignin fractions with lower molecular weight and polydispersity index (PDI) exhibited more CBH adsorption ability. Lignins with more phenolic hydroxyl groups had higher CBH binding strength. It was also found that lignin fractions with more condensed aromatics adsorbed more CBH likely attributed to stronger hydrophobic interactions.« less

A structured understanding of cellobiohydrolase I binding to poplar lignin fractions after dilute acid pretreatment

DOE PAGES

Yao, Lan; Yoo, Chang Geun; Meng, Xianzhi; ...

2018-04-04

Background: Cellulase adsorption to lignin is considered a cost barrier for bioethanol production; however, its detailed association mechanism is still not fully understood. In this study, two natural poplar variants with high and low sugar release performance were selected as the low and high recalcitrant raw materials (named L and H, respectively). Three different lignin fractions were extracted using ethanol, followed by p-dioxane and then cellulase treatment from the dilute acid pretreated poplar solids (fraction 1, 2, and 3, respectively).Results: Each lignin fraction had different physicochemical properties. Ethanol-extracted lignin had the lowest weight average molecular weight, while the molecular weightsmore » for the other two lignin fractions were similar. 31P NMR analysis revealed that lignin fraction with higher molecular weight contained more aliphatic hydroxyl groups and less phenolic hydroxyl groups. Semi-quantitative analysis by 2D HSQC NMR indicated that the lignin fractions isolated from the natural variants had different contents of syringyl (S), guaiacyl (G) and interunit linkages. Lignin extracted by ethanol contained the largest amount of S units, the smallest amounts of G and p-hydroxybenzoate (PB) subunits, while the contents of these lignin subunits in the other two lignin fractions were similar. The lignin fraction obtained after cellulase treatment was primarily comprised of β-O-4 linkages with small amounts of β-5 and β–β linkages. The binding strength of these three lignin fractions obtained by Langmuir equations were in the order of L1 > L3 > L2 for the low recalcitrance poplar and H1 > H2 > H3 for the high recalcitrance poplar.Conclusions: Overall, adsorption ability of lignin was correlated with the sugar release of poplar. Structural features of lignin were associated with its binding to CBH. For natural poplar variants, lignin fractions with lower molecular weight and polydispersity index (PDI) exhibited more CBH adsorption ability. Lignins with more phenolic hydroxyl groups had higher CBH binding strength. It was also found that lignin fractions with more condensed aromatics adsorbed more CBH likely attributed to stronger hydrophobic interactions.« less

Increasing molecular weight parameters of a helical polymer through polymerization in a chiral solvent.

PubMed

Holder, Simon J; Achilleos, Mariliz; Jones, Richard G

2006-09-27

In this communication, we will demonstrate that polymerization in a chiral solvent can affect the molecular weight distribution of the product by perturbing the balance of the P and M helical screw senses of the growing chains. Specifically, for the Wurtz-type synthesis of polymethylphenylsilane (PMPS) in either (R) or (S)-limonene, the weight-average molecular weight of the products (average Mw = 80 000) was twice that of PMPS synthesized in (R/S)-limonene (average Mw = 39 200). Peturbation of the helical segmentation along the polymer chains leads to a reduction in the rate of occurrence of a key termination step. This the first time that a chiral solvent has been demonstrated to have such an effect on a polymerization process in affecting molecular weight parameters in contrast to affecting tacticity.

Production of low-molecular weight soluble yeast β-glucan by an acid degradation method.

PubMed

Ishimoto, Yuina; Ishibashi, Ken-Ichi; Yamanaka, Daisuke; Adachi, Yoshiyuki; Kanzaki, Ken; Iwakura, Yoichiro; Ohno, Naohito

2018-02-01

β-glucan is widely distributed in nature as water soluble and insoluble forms. Both forms of β-glucan are utilized in several fields, especially for functional foods. Yeast β-glucan is a medically important insoluble particle. Solubilization of yeast β-glucan may be valuable for improving functional foods and in medicinal industries. In the present study, we applied an acid degradation method to solubilize yeast β-glucan and found that β-glucan was effectively solubilized to low-molecular weight β-glucans by 45% sulfuric acid treatment at 20°C. The acid-degraded soluble yeast β-glucan (ad-sBBG) was further fractionated into a higher-molecular weight fraction (ad-sBBG-high) and a lower-molecular weight fraction (ad-sBBG-low). Since ad-sBBG-high contained mannan, while ad-sBBG-low contained it only scarcely, it was possible to prepare low-molecular weight soluble β-glucan with higher purity. In addition, ad-sBBG-low bound to dectin-1, which is an innate immunity receptor of β-glucan, and showed antagonistic activity against reactive oxygen production and cytokine synthesis by macrophages. Thus, this acid degradation method is an important procedure for generating immune-modulating, low-molecular weight, soluble yeast β-glucan. Copyright © 2017 Elsevier B.V. All rights reserved.

Retraction Note: Catalytic living ring-opening metathesis polymerization

NASA Astrophysics Data System (ADS)

Nagarkar, Amit A.; Kilbinger, Andreas F. M.

2018-05-01

We the authors are retracting this Article because of our failure to reproduce the molecular weight dispersities (PDI) shown in Fig. 4 using the chain-transfer agent described in the paper (CTA1). While the degenerate chain-transfer mechanism described in Fig. 3 is correct, the best molecular weight dispersities that could be reproduced with the chain-transfer agent shown in the Article are much larger (PDI > 2.0) than reported.We have since studied the kinetics of CTA1 in comparison with several other chain-transfer agents we are currently investigating and we now understand that the reactivity of CTA1 towards propagating ruthenium alkylidene complexes is very low. Very long monomer addition times would therefore have been necessary to gain control over the molecular weight distribution. Such long addition times would exceed the lifetime of the Grubbs catalyst in solution. Faster addition of the monomer has since repeatedly been shown to broaden the molecular weight dispersity.Additionally, the best chain-transfer agents we are currently investigating are orders of magnitude more reactive than CTA1 but give broader molecular weight dispersities than reported in Fig. 4. Molecular weight and dispersity control as shown in Fig. 4 is therefore an inappropriate claim for CTA1.The authors deeply regret these errors and apologize to the community.

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.

Post-exercise ingestion of a unique, high molecular weight glucose polymer solution improves performance during a subsequent bout of cycling exercise.

PubMed

Stephens, Francis B; Roig, Marc; Armstrong, Gerald; Greenhaff, Paul L

2008-01-15

The aim of the present study was to determine the effect of post-exercise ingestion of a unique, high molecular weight glucose polymer solution, known to augment gastric emptying and post-exercise muscle glycogen re-synthesis, on performance during a subsequent bout of intense exercise. On three randomized visits, eight healthy men cycled to exhaustion at 73.0% (s = 1.3) maximal oxygen uptake (90 min, s = 15). Immediately after this, participants consumed a one-litre solution containing sugar-free flavoured water (control), 100 g of a low molecular weight glucose polymer or 100 g of a very high molecular weight glucose polymer, and rested on a bed for 2 h. After recovery, a 15-min time-trial was performed on a cycle ergometer, during which work output was determined. Post-exercise ingestion of the very high molecular weight glucose polymer solution resulted in faster and greater increases in blood glucose (P < 0.001) and serum insulin (P < 0.01) concentrations than the low molecular weight glucose polymer solution, and greater work output during the 15-min time-trial (164.1 kJ, s = 21.1) than both the sugar-free flavoured water (137.5 kJ, s = 24.2; P < 0.05) and the low molecular weight glucose polymer (149.4 kJ, s = 21.8; P < 0.05) solutions. These findings could be of practical importance for athletes wishing to optimize performance by facilitating rapid re-synthesis of the muscle glycogen store during recovery following prolonged sub-maximal exercise.

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.

Graph Theoretical Representation of Atomic Asymmetry and Molecular Chirality of Benzenoids in Two-Dimensional Space

PubMed Central

Zhao, Tanfeng; Zhang, Qingyou; Long, Hailin; Xu, Lu

2014-01-01

In order to explore atomic asymmetry and molecular chirality in 2D space, benzenoids composed of 3 to 11 hexagons in 2D space were enumerated in our laboratory. These benzenoids are regarded as planar connected polyhexes and have no internal holes; that is, their internal regions are filled with hexagons. The produced dataset was composed of 357,968 benzenoids, including more than 14 million atoms. Rather than simply labeling the huge number of atoms as being either symmetric or asymmetric, this investigation aims at exploring a quantitative graph theoretical descriptor of atomic asymmetry. Based on the particular characteristics in the 2D plane, we suggested the weighted atomic sum as the descriptor of atomic asymmetry. This descriptor is measured by circulating around the molecule going in opposite directions. The investigation demonstrates that the weighted atomic sums are superior to the previously reported quantitative descriptor, atomic sums. The investigation of quantitative descriptors also reveals that the most asymmetric atom is in a structure with a spiral ring with the convex shape going in clockwise direction and concave shape going in anticlockwise direction from the atom. Based on weighted atomic sums, a weighted F index is introduced to quantitatively represent molecular chirality in the plane, rather than merely regarding benzenoids as being either chiral or achiral. By validating with enumerated benzenoids, the results indicate that the weighted F indexes were in accordance with their chiral classification (achiral or chiral) over the whole benzenoids dataset. Furthermore, weighted F indexes were superior to previously available descriptors. Benzenoids possess a variety of shapes and can be extended to practically represent any shape in 2D space—our proposed descriptor has thus the potential to be a general method to represent 2D molecular chirality based on the difference between clockwise and anticlockwise sums around a molecule. PMID:25032832

Occurrence and extent of bruising according to duration of administration of subcutaneous low-molecular-weight heparin: a quasi-experimental case-crossover study.

PubMed

Palese, Alvisa; Aidone, Elena; Dante, Angelo; Pea, Federico

2013-01-01

Several authors have documented the role of low-molecular-weight heparin injection techniques in bruising. However, few researchers have measured the influence of injection duration on the occurrence and extent of bruising. The aim of this study was to evaluate the influence of different durations of subcutaneous heparin injection on the occurrence and extent of bruising. A quasi-experimental case-crossover study design was adopted in 2010. A consecutive series of patients admitted to 2 orthopedic units in a large (600 beds) teaching hospital located in northern Italy were eligible for enrolment. Injections were administered following a standard procedure. The manipulated variable was the duration of the injection, 10 seconds (treatment A) and 30 seconds (treatment B). The evaluation of bruise occurrence and extension performed after 48 hours and data analysis were conducted in a blinded fashion. A total of 150 patients receiving their first and second subcutaneous heparin injections (300 injections) were enrolled. Eighty-seven bruises were observed out of 300 injections (29%): 57 of 150 (38%) after injections lasting 10 seconds and 30 of 150 (20%) after injections lasting 30 seconds (relative risk, 1.50; 95% confidence interval, 1.21-1.86; P = .00). Of the 87 bruises that occurred, 69 (79.3%) were small (2-5 mm) and 18 (20.6%) were large (>5 mm), with no difference in size between 10- and 30-second injections (relative risk, 0.91; 95% confidence interval, 0.39-2.12; P = .83). Low-molecular-weight heparin injection should be administered over 30 seconds to decrease bruising. There is a need to reflect on the feasibility of such a practice because injecting low-molecular-weight heparin at 30 seconds requires accuracy, a steady hand, the absence of tremor, a calm environment, and the ability to administer an infinitesimally small amount of liquid (eg, 0.4 mL) per second.

Increase in gap-junctional intercellular communications (GJIC) of normal human dermal fibroblasts (NHDF) on surfaces coated with high-molecular-weight hyaluronic acid (HMW HA).

PubMed

Park, Jeong Ung; Tsuchiya, Toshie

2002-06-15

Normal human dermal fibroblast (NHDF) cells were used to detect differences in gap-junctional intercellular communication (GJIC) by hyaluronic acid (HA), a linear polymer built from repeating disaccharide units that consist of N-acetyl-D-glucosamine (GlcNa) and D-glucuronic acid (GlcA) linked by a beta 1-4 glycosidic bond. The NHDF cells were cultured with different molecular weights (MW) of HA for 4 days. The rates of cell attachment in dishes coated with high-molecular-weight (HMW; 310 kDa or 800 kDa) HA at 2 mg/dish were significantly reduced at an early time point compared with low-molecular-weight (LMW; 4.8 kDa or 48 kDa) HA with the same coating amounts. HA-coated surfaces were observed by atomic force microscopy (AFM) under air and showed that HA molecules ran parallel in the dish coated with LMW HA and had an aggregated island structure in the dish coated with HMW HA surfaces. The cell functions of GJIC were assayed by a scrape-loading dye transfer (SLDT) method using a dye solution of Lucifer yellow. Promotion of the dye transfer was clearly obtained in the cell monolayer grown on the surface coated with HMW HA. These results suggest that HMW HA promotes the function of GJIC in NHDF cells. In contrast, when HMW HA was added to the monolayer of NHDF cells, the functions of GJIC clearly were lowered in comparison with the cells grown in the control dish or with those grown on the surface of HMW HA. Therefore it is concluded that the MW size of HA and its application method are important factors for generating biocompatible tissue-engineered products because of the manner in which the GJIC participates in cell differentiation and cell growth rate. Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 541-547, 2002

Modified Mostardi approach with ultra-high-molecular-weight polyethylene tape for total hip arthroplasty provides a good rate of union of osteotomized fragments.

PubMed

Kuroda, Yutaka; Akiyama, Haruhiko; Nankaku, Manabu; So, Kazutaka; Matsuda, Shuichi

2015-07-01

A lateral approach is common in total hip arthroplasty because of the good exposure it provides and its low complication rates. However, a drawback of the procedure is that the abductor mechanism is damaged when the tendinous insertion of the abductor muscle is split. Here, we describe a wafer technique using ultra-high-molecular-weight polyethylene tape for promising reattachment of the abductor mechanism. We retrospectively evaluated 120 consecutive primary total hip arthroplasties performed using a modified Mostardi approach, which involved reattaching the trochanter using either a braided polyester suture (polyester suture group, n = 60) or ultra-high-molecular-weight polyethylene tape (UHMWPE tape group, n = 60). The osteotomized fragment was reattached by inducing bone-to-bone contact using 3-mm-wide tapes that were precisely tied with a double-loop sliding knot in conjunction with a cable gun tensioner. The abductor strength and radiographic union rate were postoperatively assessed at 4 weeks and 6 months, respectively. A statistically significant lower incidence of nonunion and cutout was observed in the UHMWPE group (0 and 5.0 %, respectively) compared to the polyester suture group (8.3 and 15 %, respectively). No differences in abductor strength either preoperatively or at 4 weeks postoperatively were observed between the groups. In radiographically healed patients, abductor strength at 4 weeks post-surgery exceeded preoperative strength. The recovery rate of hip abductor strength was 109.9 ± 34.3 % in union patients and 92.9 ± 23.3 % in nonunion patients, which was statistically significant. The mean Japanese Orthopedic Association hip scores improved from 48.6 to 86.8 in union patients and from 50.3 to 85.9 in nonunion patients at 1 year postoperatively; however, this difference was not significant. The modified Mostardi approach using ultra-high molecular weight polyethylene tape can promote successful union of the osteotomized fragment.

Modeling the relationship between body weight and energy intake: A molecular diffusion-based approach

PubMed Central

2012-01-01

Background Body weight is at least partly controlled by the choices made by a human in response to external stimuli. Changes in body weight are mainly caused by energy intake. By analyzing the mechanisms involved in food intake, we considered that molecular diffusion plays an important role in body weight changes. We propose a model based on Fick's second law of diffusion to simulate the relationship between energy intake and body weight. Results This model was applied to food intake and body weight data recorded in humans; the model showed a good fit to the experimental data. This model was also effective in predicting future body weight. Conclusions In conclusion, this model based on molecular diffusion provides a new insight into the body weight mechanisms. Reviewers This article was reviewed by Dr. Cabral Balreira (nominated by Dr. Peter Olofsson), Prof. Yang Kuang and Dr. Chao Chen. PMID:22742862

Treatment efficacy for idiopathic recurrent pregnancy loss - a systematic review and meta-analyses.

PubMed

Rasmark Roepke, Emma; Hellgren, Margareta; Hjertberg, Ragnhild; Blomqvist, Lennart; Matthiesen, Leif; Henic, Emir; Lalitkumar, Sujata; Strandell, Annika

2018-03-30

Medical treatment of women with idiopathic recurrent pregnancy loss is controversial. The objective was to assess the effects of different treatments on live birth rates and complications in women with unexplained recurrent pregnancy loss. We searched MEDLINE, Embase and the Cochrane Library, and identified 1415 publications. This systematic review included 21 randomized controlled trials regarding acetylsalicylic acid, low-molecular-weight heparin, progesterone, intravenous immunoglobulin or leukocyte immune therapy in women with three or more consecutive miscarriages of unknown cause. The study quality was assessed and data was extracted independently by at least two authors. No significant difference in live birth rate was found when acetylsalicylic acid was compared with low-molecular-weight heparin or with placebo. Meta-analyses of low-molecular-weight heparin vs. control found no significant differences in live birth rate [risk ratio (RR) 1.47, 95% CI 0.83-2.61]. Treatment with progesterone starting in the luteal phase seemed effective in increasing live birth rate (RR 1.18, 95% CI 1.09-1.27) but not when started after conception. Intravenous immunoglobulin showed no effect on live birth rate compared with placebo (RR 1.07, 95% CI 0.91-1.26). Paternal immunization compared with autologous immunization showed a significant difference in outcome (RR 1.8, 95% CI 1.34-2.41), although the studies were small and at high risk of bias. The literature does not allow advice on any specific treatment for idiopathic recurrent pregnancy loss, with the exception of progesterone starting from ovulation. We suggest that any treatment for recurrent pregnancy loss should be used within the context of a randomized controlled trial. © 2018 Nordic Federation of Societies of Obstetrics and Gynecology.

Spontaneous nucleotide exchange in low molecular weight GTPases by fluorescently labeled γ-phosphate-linked GTP analogs

PubMed Central

Korlach, Jonas; Baird, Daniel W.; Heikal, Ahmed A.; Gee, Kyle R.; Hoffman, Gregory R.; Webb, Watt W.

2004-01-01

Regulated guanosine nucleotide exchange and hydrolysis constitute the fundamental activities of low molecular weight GTPases. We show that three guanosine 5′-triphosphate analogs with BODIPY fluorophores coupled via the gamma phosphate bind to the GTPases Cdc42, Rac1, RhoA, and Ras and displace guanosine 5′-diphosphate with high intrinsic exchange rates in the presence of Mg2+ ions, thereby acting as synthetic, low molecular weight guanine nucleotide exchange factors. The accompanying large fluorescence enhancements (as high as 12-fold), caused by a reduction in guanine quenching of the environmentally sensitive BODIPY dye fluorescence on protein binding, allow for real-time monitoring of this spontaneous nucleotide exchange in the visible spectrum with high signal-to-noise ratios. Binding affinities increased with longer aliphatic linkers connecting the nucleotide and BODIPY fluorophore and were in the 10–100 nM range. Steady-state and time-resolved fluorescence spectroscopy showed an inverse relationship between linker length and fluorescence enhancement factors and differences in protein-bound fluorophore mobilities, providing optimization criteria for future applications of such compounds as efficient elicitors and reporters of nucleotide exchange. EDTA markedly enhanced nucleotide exchange, enabling rapid loading of GTPases with these probes. Differences in active site geometries, in the absence of Mg2+, caused qualitatively different reporting of the bound state by the different analogs. The BODIPY analogs also prevented the interaction of Cdc42 with p21 activated kinase. Together, these results validate the use of these analogs as valuable tools for studying GTPase functions and for developing potent synthetic nucleotide exchange factors for this important class of signaling molecules. PMID:14973186

[Clinical and metabolic consequences of uremic toxicity].

PubMed

Rutkowski, Przemysław

2006-01-01

Retention of many substances takes place in the pathogenesis of uremic toxicity. There are almost 100 different molecules described and defined as uremic toxins. These substances are divided into three groups according to EUTOX group calssification. Small water soluble molecules with a molecular weight less than 500 D are included into the first group. Derivate of guanidines, purines, pyrimidines and methyloamines appeared in this group. There is also an unclassified subgroup with urea as a "classical" toxin which the real role in the uraemic syndrome is still discussed. Main symptoms caused by these molecules are digestive disturbances, neurological changes, hypertension etc. We can eliminate almost all of these toxins with standard methods used during dialysotherapy. Substances with a different molecular weight but connected with proteins determine the second group. AGE-s, phenol derivates, leptin and poliamines beside others create this group. There are many studies that have proved that these toxins cause hypertension, arteriosclerosis and shortened life time of hemodialysed patients. However, melatonin toxicity is not fully proved. Different types of renal replacement therapy are not valid to purify blood from protein-bound substances. Middle molecules are included into the third group, with a molecular weight higher than 500 D. There are cytokines, neuro-transmitters e.g. beta-endorphin, metencephalin and many others accounted into this group. One of them is the parathormon, well known and considered as "universal" toxin for several years. Middle molecules are causing very different effects. They are responsible for: anemia, arteriosclerosis, chronic inflammation and generally increase dialysed patient mortality. Toxic action of several molecules described below is still not proved; however there are some ongoing studies aimed to find pathophysiological links between old and new described uremic toxins.

Diffusion of macromolecules through sclera.

PubMed

Miao, Heng; Wu, Bi-Dong; Tao, Yong; Li, Xiao-Xin

2013-02-01

To quantify the in vitro permeability coefficient over different topographical locations of porcine sclera to macromolecules with different molecular weight. Fresh equatorial and posterior superotemporal porcine sclera was mounted in a two-chamber diffusion apparatus, and its permeability to fluorescein isothiocyanate (FITC)-conjugated dextrans ranging in molecular weight from 40 kDa to 150 kDa was determined by fluorescence spectrophotometry. The sclera was processed as frozen sections and viewed with a fluorescence microscope. The thickness of the area and the thickness that macromolecules enriched in the surface of sclera were measured. The permeability coefficient (Pc) of porcine sclera to macromolecules was significantly higher (40 kDa, p = 0.028; 70 kDa, p = 0.033; 150 kDa, p = 0.007) in equatorial region than posterior, which could be attributed to the significant difference of thickness (p < 0.001, Kruskal-Wallis) between them. Moreover, linear regression indicated a significant negative relationship (40 kDa, p < 0.001; 70 kDa, p = 0.015; 150 kDa, p < 0.001) between scleral permeability coefficient and thickness. Also, Pc declined significantly with increasing molecular weight (MW, p < 0.001, Kruskal-Wallis). The area that the macromolecules enriched in the scleral surface was thicker for those with larger MW (p < 0.001, Kruskal-Wallis). The maximum MW and size for equatorial and posterior superotemporal scleral tissue were 185.01 KDa and 180.42 KDa, 9.92 nm and 9.67 nm, respectively. The permeability coefficient of porcine sclera has a significant negative relationship with scleral thickness and MW of macromolecules. Larger macromolecules are more likely to accumulate in scleral surface. The difference between topographical locations may have pharmacokinetic implications when considering transscleral diffusion of macromolecules. © 2012 The Authors. Acta Ophthalmologica © 2012 Acta Ophthalmologica Scandinavica Foundation.

Synergistic effect of high and low molecular weight molecules in the foamability and foam stability of sparkling wines.

PubMed

Coelho, Elisabete; Reis, Ana; Domingues, M Rosário M; Rocha, Sílvia M; Coimbra, Manuel A

2011-04-13

The foam of sparkling wines is a key parameter of their quality. However, the compounds that are directly involved in foam formation and stabilization are not yet completely established. In this work, seven sparkling wines were produced in Bairrada appellation (Portugal) under different conditions and their foaming properties evaluated using a Mosalux-based device. Fractionation of the sparkling wines into four independent fractions, (1) high molecular weight material, with molecular weight higher than 12 kDa (HMW), (2) hydrophilic material with molecular weigh between 1 and 12 kDa (AqIMW), (3) hydrophobic material with molecular weigh between 1 and 12 kDa (MeIMW), and (4) hydrophobic material with a molecular weight lower than 1 kDa (MeLMW), allowed the observation that the wines presenting the lower foam stability were those that presented lower amounts of the MeLMW fraction. The fraction that presented the best foam stability was HMW. When HMW is combined with MeLMW fraction, the foam stability largely increased. This increase was even larger, approaching the foam stability of the sparkling wine, when HMW was combined with the less hydrophobic subfraction of MeLMW (fraction 3). Electrospray tandem mass spectrometry (ESI-MS/MS) of fraction 3 allowed the assignment of polyethylene glycol oligomers (n = 5-11) and diethylene glycol 8-hydroxytridecanoate glyceryl acetate. To observe if these molecules occur in sparkling wine foam, the MeLMW was recovered directly from the sparkling wine foam and was also analyzed by ESI-MS/MS. The presence of monoacylglycerols of palmitic and stearic acids, as well as four glycerylethylene glycol fatty acid derivatives, was observed. These surface active compounds are preferentially partitioned by the sparkling wine foam rather than the liquid phase, allowing the inference of their role as key components in the promotion and stabilization of sparkling wine foam.

A low molecular weight zinc2+-dipicolylamine-based probe detects apoptosis during tumour treatment better than an annexin V-based probe.

PubMed

Palmowski, Karin; Rix, Anne; Lederle, Wiltrud; Behrendt, Florian F; Mottaghy, Felix M; Gray, Brian D; Pak, Koon Y; Palmowski, Moritz; Kiessling, Fabian

2014-02-01

Molecular imaging of apoptosis is frequently discussed for monitoring cancer therapies. Here, we compare the low molecular weight phosphatidylserine-targeting ligand zinc2+-dipicolylamine (Zn2+-DPA) with the established but reasonably larger protein annexin V. Molecular apoptosis imaging with the fluorescently labelled probes annexin V (750 nm, 36 kDa) and Zn2+-DPA (794 nm, 1.84 kDa) was performed in tumour-bearing mice (A431). Three animal groups were investigated: untreated controls and treated tumours after 1 or 4 days of anti-angiogenic therapy (SU11248). Additionally, μPET with 18 F-FDG was performed. Imaging data were displayed as tumour-to-muscle ratio (TMR) and validated by quantitative immunohistochemistry. Compared with untreated control tumours, TUNEL staining indicated significant apoptosis after 1 day (P < 0.05) and 4 days (P < 0.01) of treatment. Concordantly, Zn2+-DPA uptake increased significantly after 1 day (P < 0.05) and 4 days (P < 0.01). Surprisingly, annexin V failed to detect significant differences between control and treated animals. Contrary to the increasing uptake of Zn2+-DPA, 18 F-FDG tumour uptake decreased significantly at days 1 (P < 0.05) and 4 (P < 0.01). Increase in apoptosis during anti-angiogenic therapy was detected significantly better with the low molecular weight probe Zn2+-DPA than with the annexin V-based probe. Additionally, significant treatment effects were detectable as early using Zn2+-DPA as with measurements of the glucose metabolism using 18 F-FDG. • The detection of apoptosis by non-invasive imaging is important in oncology. • A new low molecular weight probe Zn2+-DPA shows promise in depicting anti-angiogenic effects. • The small Zn2+-DPA ligand appears well suited for monitoring therapy. • Treatment effects are detectable just as early with Zn2+-DPA as with 18F-FDG.

The High and Low Molecular Weight Forms of Hyaluronan Have Distinct Effects on CD44 Clustering*

PubMed Central

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

2012-01-01

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. PMID:23118219

Preparation of Low Molecular Weight Chondroitin Sulfates, Screening of a High Anti-Complement Capacity of Low Molecular Weight Chondroitin Sulfate and Its Biological Activity Studies in Attenuating Osteoarthritis

PubMed Central

Li, Lian; Li, Yan; Feng, Danyang; Xu, Linghua; Yin, Fengxin; Zang, Hengchang; Liu, Chunhui; Wang, Fengshan

2016-01-01

Chondroitin sulfate (CS) plays important roles in the complement system. However, the CS structure is complicated due to different sources and the number and positions of sulfate groups. The objective of this study was to prepare different low molecular weight chondroitin sulfates (LMWCSs) and to investigate the biological activity in anti-complement capacity. A series of LMWCSs was prepared from different sources and characterized by ultraviolet-visible (UV) spectroscopy, high-performance liquid chromatography (HPLC), size exclusion chromatography-multiangle laser light scattering (SEC-MALLS) and nuclear magnetic resonance (NMR) spectroscopy. Hemolytic, anti-complement 3 deposition capacity and cell viability assays were carried out to investigate the biological activities in vitro. The results showed that LMWCS prepared from shark cartilage with the oxidative degradation method (LMWCS-S-O) had the best anti-complement capacity. LMWCS-S-O could inhibit the alternative pathway of the complement system and protect chondrocytes from cell death. The attenuating effect of LMWCS-S-O on Osteoarthritis (OA) was investigated by destabilization of the medial meniscus (DMM) model in vivo. Functional wind-up, histological and C5b-9 analyses were used to evaluate the treatment effect on the OA model. In vivo results showed that LMWCS-S-O could attenuate OA. LMWCS-S-O with a high content of ΔDi-2,6diS and ΔDi-6S could be used for attenuating OA through regulating the complement system. PMID:27727159

The correlation between gelatin macroscale differences and nanoparticle properties: providing insight into biopolymer variability.

PubMed

Stevenson, André T; Jankus, Danny J; Tarshis, Max A; Whittington, Abby R

2018-05-21

From therapeutic delivery to sustainable packaging, manipulation of biopolymers into nanostructures imparts biocompatibility to numerous materials with minimal environmental pollution during processing. While biopolymers are appealing natural based materials, the lack of nanoparticle (NP) physicochemical consistency has decreased their nanoscale translation into actual products. Insights regarding the macroscale and nanoscale property variation of gelatin, one of the most common biopolymers already utilized in its bulk form, are presented. Novel correlations between macroscale and nanoscale properties were made by characterizing similar gelatin rigidities obtained from different manufacturers. Samples with significant differences in clarity, indicating sample purity, obtained the largest deviations in NP diameter. Furthermore, a statistically significant positive correlation between macroscale molecular weight dispersity and NP diameter was determined. New theoretical calculations proposing the limited number of gelatin chains that can aggregate and subsequently get crosslinked for NP formation were presented as one possible reason to substantiate the correlation analysis. NP charge and crosslinking extent were also related to diameter. Lower gelatin sample molecular weight dispersities produced statistically smaller average diameters (<75 nm), and higher average electrostatic charges (∼30 mV) and crosslinking extents (∼95%), which were independent of gelatin rigidity, conclusions not shown in the literature. This study demonstrates that the molecular weight composition of the starting material is one significant factor affecting gelatin nanoscale properties and must be characterized prior to NP preparation. Identifying gelatin macroscale and nanoscale correlations offers a route toward greater physicochemical property control and reproducibility of new NP formulations for translation to industry.

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…

Gel filtration of sialoglycoproteins.

PubMed Central

Alhadeff, J A

1978-01-01

The role of sialic acid in the gel-filtration behaviour of sialoglycoproteins was investigated by using the separated isoenzymes of purified human liver alpha-L-fucosidase and several other well-known sialic acid-containing glycoproteins (fetuin, alpha1-acid glycoprotein, thyroglobulin and bovine submaxillary mucin). For each glycoprotein studied, gel filtration of its desialylated derivative gave an apparent molecular weights much less than that expected just from removal of sialic acid. For the lower-molecular-weight glycoproteins (fetuin and alpha1-acid glyocprotein), gel filtration of the sialylated molecules led to apparent molecular weights much larger than the known values. The data indicate that gel filtration cannot be used for accurately determining the molecular weights of at least some sialoglycoproteins. Images Fig. 1. PMID:356853

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

Polyimide molding powder, coating, adhesive, and matrix resin

NASA Technical Reports Server (NTRS)

St.clair, Terry L. (Inventor); Progar, Donald J. (Inventor)

1992-01-01

The invention is a polyimide prepared from 3,4'-oxydianiline (3,4'-ODA) and 4,4'-oxydiphthalic anhydride (ODPA), in 2-methoxyethyl ether (diglyme). The polymer was prepared in ultra high molecular weight and in a controlled molecular weight form which has a 2.5 percent offset in stoichiometry (excess diamine) with a 5.0 percent level of phthalic anhydride as an endcap. This controlled molecular weight form allows for greatly improved processing of the polymer for moldings, adhesive bonding, and composite fabrication. The higher molecular weight version affords tougher films and coatings. The overall polymer structure groups in the dianhydride, the diamine, and a metal linkage in the diamine affords adequate flow properties for making this polymer useful as a molding powder, adhesive, and matrix resin.

A study of physical properties of ODPA-p-PDA polyimide films

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Eftekhari, Abe; St.clair, Terry L.

1990-01-01

Physical properties were investigated of ODPA-p-PDA polyimide films, including their lower molecular weight versions with phthalimide endcaps. Free volume, determined by low energy positron annihilation in the test films, was the major parameter of interest since all other physical properties are ostensibly related to it. It affects the dielectric constant as well as the saturation moisture pickup of the test films. An empirical relation was developed between the free volume and molecular weight of the test films, comparable to the Mark-Houwink relation between the polymer solution viscosity and the molecular weight. Development of such a relation constitutes a unique achievement since it enables researchers to estimate the molecular weight of an intractable polymer in solid state for the first time.

Summary of GPC/DV results for space exposed poly(arylene ether phosphine oxide)s

NASA Technical Reports Server (NTRS)

Siochi, Emilie

1995-01-01

Gel Permeation Chromatography (GPC) was used to analyze poly(arylene ether phosphine oxide)s whose backbones were identical except for the ketone content and placement. These samples were exposed to low Earth orbit environment (predominantly atomic oxygen) on space shuttle flights. The materials and their unexposed controls were then characterized by GPC to investigate the effect of atomic oxygen on the molecular weight distributions. Analysis of the soluble portion of the samples revealed that there was significant loss of high molecular weight species. The presence of insoluble material also suggested that crosslinking was induced by the atomic oxygen exposure and that this very likely occurred at the high molecular weight portion of the molecular weight distribution.

Saponification equivalent of dasamula taila.

PubMed

Saxena, R B

1994-07-01

Saponification equivalent values of Dasamula taila are very useful for the technical and analytical work. It gives the mean molecular weight of the glycerides and acids present in Dasamula Taila. Saponification equivalent values of Dasamula taila are reported in different packings.

Ultraviolet-B radiation mobilizes uranium from uranium-dissolved organic carbon complexes in aquatic systems, demonstrated by asymmetrical flow field-flow fractionation.

PubMed

Nehete, Sachin Vilas; Christensen, Terje; Salbu, Brit; Teien, Hans-Christian

2017-05-05

Humic substances have a tendency to form complexes with metal ions in aquatic medium, impacting the metal mobility, decreasing bioavailability and toxicity. Ultraviolet-B (UV-B) radiation exposure degrades the humic substance, changes their molecular weight distribution and their metal binding capacity in aquatic medium. In this study, we experimented the effect of UV-B radiation on the uranium complexed with fulvic acids and humic acids in a soft water system at different pH, uranium concentrations and radiant exposure. The concentration and distribution of uranium in a complexed form were investigated by asymmetrical flow field-flow fractionation coupled to multi detection technique (AsFlFFF-UV-ICP-MS). The major concentration of uranium present in complexes was primarily associated with average and higher molecular weight fulvic and humic acids components. The concentration of uranium in a complexed form increased with increasing fulvic and humic acid concentrations as well as pH of the solution. The higher molecular weight fraction of uranium was degraded due to the UV-B exposure, transforming about 50% of the uranium-dissolved organic carbon complexes into low molecular weight uranium species in complex form with organic ligands and/or free form. The result also suggests AsFlFFF-UV-ICP-MS to be an important separation and detection technique for understanding the interaction of radionuclides with dissolved organic matter, tracking size distribution changes during degradation of organic complexes for understanding mobility, bioavailability and ecosystem transfer of radionuclides as well as metals. Copyright © 2017 Elsevier B.V. All rights reserved.

Mutagenicity, anticancer activity and blood brain barrier: similarity and dissimilarity of molecular alerts.

PubMed

Toropov, Andrey A; Toropova, Alla P; Benfenati, Emilio; Salmona, Mario

2018-06-01

The aim of the present work is an attempt to define computable measure of similarity between different endpoints. The similarity of structural alerts of different biochemical endpoints can be used to solve tasks of medicinal chemistry. Optimal descriptors are a tool to build up models for different endpoints. The optimal descriptor is calculated with simplified molecular input-line entry system (SMILES). A group of elements (single symbol or pair of symbols) can represent any SMILES. Each element of SMILES can be represented by so-called correlation weight i.e. coefficient that should be used to calculate descriptor. Numerical data on the correlation weights are calculated by the Monte Carlo method, i.e. by optimization procedure, which gives maximal correlation coefficient between the optimal descriptor and endpoint for the training set. Statistically stable correlation weights observed in several runs of the optimization can be examined as structural alerts, which are promoters of the increase or the decrease of a biochemical activity of a substance. Having data on several runs of the optimization correlation weights, one can extract list of promoters of increase and list of promoters of decrease for an endpoint. The study of similarity and dissimilarity of the above lists has been carried out for the following pairs of endpoints: (i) mutagenicity and anticancer activity; (ii) mutagenicity and blood brain barrier; and (iii) blood brain barrier and anticancer activity. The computational experiment confirms that similarity and dissimilarity for pairs of endpoints can be measured.

Volatilization of benzene and eight alkyl-substituted benzene compounds from water

USGS Publications Warehouse

Rathbun, R.E.; Tai, D.Y.

1988-01-01

Predicting the fate of organic compounds in streams and rivers often requires knowledge of the volatilization characteristics of the compounds. The reference-substance concept, involving laboratory-determined ratios of the liquid-film coefficients for volatilization of the organic compounds to the liquid-film coefficient for oxygen absorption, is used to predict liquid-film coefficients for streams and rivers. In the absence of experimental data, two procedures have been used for estimating these liquid-film coefficient ratios. These procedures, based on the molecular-diffusion coefficient and on the molecular weight, have been widely used but never extensively evaluated. Liquid-film coefficients for the volatilization of benzene and eight alkyl-substituted benzene compounds (toluene through n-octylbenzene) from water were measured in a constant-temperature, stirred water bath. Liquid-film coefficients for oxygen absorption were measured simultaneously. A range of water mixing conditions was used with a water temperature of 298.2 K. The ratios of the liquid-film coefficients for volatilization to the liquid-film coefficient for oxygen absorption for all of the organic compounds were independent of mixing conditions in the water. Experimental ratios ranged from 0.606 for benzene to 0.357 for n-octylbenzene. The molecular-diffusion-coefficient procedure accurately predicted the ratios for ethylbenzene through n-pentylbenzene with a power dependence of 0.566 on the molecular-diffusion coefficient, in agreement with published values. Predicted ratios for benzene and toluene were slightly larger than the experimental ratios. These differences were attributed to possible interactions between the molecules of these compounds and the water molecules and to benzene-benzene interactions that form dimers. Because these interactions also are likely to occur in natural waters, it was concluded that the experimental ratios are more correct than the predicted ratios for application purposes in the reference-substance concept. Predicted ratios for n-hexylbenzene, n-heptylbenzene, and n-octylbenzene were larger than the experimental ratios. These differences were attributed to a sorption-desorption process between these compounds and the surfaces of the constant-temperature water bath. Other experimental problems associated with preparing water solutions of these slightly soluble compounds also may have contributed to the differences. Because these processes are not part of the true volatilization process, it was concluded that the predicted ratios for these three compounds are probably more correct than the experimental ratios for application purposes in the reference-substance concept. Any model of the fate of these compounds in streams and rivers would have to include terms accounting for sorption processes, however. The molecular-weight procedure accurately predicted the ratios for ethylbenzene through n-pentylbenzene, but only if the power dependence on the molecular weight was decreased from the commonly used -0.500 to -0.427. Deviations for the low- and high-molecular-weight compounds were similar to those observed for the molecular-diffusion-coefficient procedure.

Precise measurement of the self-diffusion coefficient for poly(ethylene glycol) in aqueous solution using uniform oligomers

NASA Astrophysics Data System (ADS)

Shimada, Kayori; Kato, Haruhisa; Saito, Takeshi; Matsuyama, Shigetomo; Kinugasa, Shinichi

2005-06-01

Uniform poly(ethylene glycol) (PEG) oligomers, with a degree of polymerization n =1-40, were separated by preparative supercritical fluid chromatography from commercial monodispersed samples. Diffusion coefficients, D, for separated uniform PEG oligomers were measured in dilute solutions of deuterium oxide (D2O) at 30 ° C, using pulsed-field gradient nuclear magnetic resonance. The measured D for each molecular weight was extrapolated to infinite dilution. Diffusion coefficients obtained at infinite dilution follow the scaling behavior of Zimm-type diffusion, even in the lower molecular weight range. Molecular-dynamics simulations for PEG in H2O also showed this scaling behavior, and reproduced close hydrodynamic interactions between PEG and water. These findings suggest that diffusion of PEG in water is dominated by hydrodynamic interaction over a wide molecular weight range, including at low molecular weights around 1000.

Physicochemical and Biological Studies on Various Preparations of Tuberculin Purifield Protein Derivative

PubMed Central

Landi, S.; Held, H. R.

1965-01-01

Tuberculin purified protein derivative (PPD) has been prepared by seven different precipitation methods from culture filtrate of Mycobacterium tuberculosis var. hominis. It was found to contain 48 to 99% tuberculoprotein, depending on the method of precipitation. The remaining percentage is represented by nucleic acid, polysaccharide, and ash. Activation analysis on tuberculin PPD and on tubercle bacilli has revealed the presence of trace elements. The molecular weight of tuberculin PPD has been found to be of the order of 14,800 to 27,800. The biological activity of tuberculin PPD varies from lot to lot and from method to method. A correlation between its molecular weight and its biological activity seems to exist. Images Fig. 1 Fig. 3 PMID:14325869

On the origin of Triton

NASA Astrophysics Data System (ADS)

Celebonovic, V.

1986-01-01

The origin of Triton, based on the theory of materials under high pressure by Savic and Kasanin (1962, 1965), is described. The mean molecular weight (A) and the volume of one gram mole of Triton's material (V) are evaluated using its values of mass and radius; it is calculated that A = 67 + or - 2 and V = 3 + or - 2. These values are compared with Celebonovic's (1983) model of Neptune; it is observed that the mean molecular weight of Triton is ten times larger than Neptune's. The cause of this large variation in chemical composition is investigated. It is hypothesized that Triton and Neptune formed in different regions of the solar system, and that Triton was ejected from its primordial orbit and was later captured by Neptune.

Bio-activity of natural polymers from the genus Pistacia: a validated model for their antimicrobial action.

PubMed

Sharifi, Mohammad Sharif; Ebrahimi, Diako; Hibbert, David Brynn; Hook, James; Hazell, Stuart Loyd

2011-12-29

The polymers from mastic gum of Pistacia lentiscose and subspecies of Pistacia atlantica, (sp. kurdica, mutica and cabolica) have been isolated and characterised by gel permeation chromatography (GPC) and 13C NMR spectroscopy as cis-1,4-poly-?-myrcenes. They were screened against Helicobacter pylori and other Gram-negative and Gram-positive bacteria to evaluate their antimicrobial action. In order to further test their hypothesised mode of action, two polymer types were synthesized: one from myrcene, and four from polyvinyl alcohols of different molecular weights, derivatised with p-hydroxybenzoate. The anti-microbial activity of these polymers, evaluated through their 'kill' kinetics, was found to be related to their functional groups, their molecular weight and their solubility.

Electrophoretic variation in low molecular weight lens crystallins from inbred strains of rats.

PubMed

Donner, M E; Skow, L C; Kunz, H W; Gill, T J

1985-10-01

Analysis of rat lens soluble proteins by analytical isoelectric focusing detected two inherited electrophoretic differences in low molecular weight (LM) crystallins from inbred strains of rats (Rattus norvegicus). The polymorphic lens crystallins were shown to be similar to a genetically variant LM crystallin, LEN-1, previously described in mice (Mus musculus) and encoded on chromosome 1, at a locus linked to Pep-3 (dipeptidase). Linkage analysis demonstrated that the rat crystallin locus was loosely linked to Pep-3 at a recombination distance of 38 +/- 4.5 U. These data suggest the conservation of a large chromosomal region during the evolution of Rodentia and support the hypothesis that the gamma-crystallins are evolving more rapidly than alpha- or beta-crystallins.

Understanding the effects of lignosulfonate on enzymatic saccharification of pure cellulose

Treesearch

Hongming Lou; Haifeng Zhou; Xiuli Li; Mengxia Wang; J.Y. Zhu; Xueqing Qiu

2014-01-01

The effects of lignosulfonate (LS) on enzymatic saccharification of pure cellulose were studied. Four fractions of LS with different molecular weight (MW) prepared by ultrafiltration of a commercial LS were applied at different loadings to enzymatic hydrolysis of Whatman paper under different pH. Using LS fractions with low MW and high degree of sulfonation can enhance...

Studies on the accessibility of deoxyribonucleic acid in deoxyribonucleoprotein to cationic molecules

PubMed Central

Itzhaki, Ruth F.

1971-01-01

The binding of deoxyribonucleoprotein to Toluidine Blue, to cetylpyridinium chloride and to polylysine of various molecular weights was studied to determine the percentage of free DNA phosphate groups in deoxyribonucleoprotein. Binding was measured by addition of these reagents to deoxyribonucleoprotein at a range of concentrations such that complete precipitation of the deoxyribonucleoprotein occurred. With Toluidine Blue the binding corresponded to about 48% of the DNA phosphates in deoxyribonucleoprotein. The dye did not cause appreciable displacement of protein from the DNA. With cetylpyridinium chloride the binding corresponded to about 41% of the DNA phosphates. With polylysine preparations of molecular weight 1250 and 7790 the binding values for deoxyribonucleoprotein were 46 and 38% respectively. The results suggest that the free phosphates lie in stretches sufficiently long to accommodate most of each polylysine molecule. With polylysine of molecular weight 62000 cross-linking of free stretches of DNA on different deoxyribonucleoprotein molecules probably occurs. It is concluded that although most of the free phosphates are probably `hidden' beneath covering histone, corresponding perhaps to runs of non-basic residues in the latter, they are surprisingly accessible to very large molecules. The relevance of this finding to the problem of gene repression is discussed. PMID:5166331

PDGF-BB induces vascular smooth muscle cell expression of high molecular weight FGF-2, which accumulates in the nucleus.

PubMed

Pintucci, Giuseppe; Yu, Pey-Jen; Saponara, Fiorella; Kadian-Dodov, Daniella L; Galloway, Aubrey C; Mignatti, Paolo

2005-08-15

Basic fibroblast growth factor (FGF-2) and platelet-derived growth factor (PDGF) are implicated in vascular remodeling secondary to injury. Both growth factors control vascular endothelial and smooth muscle cell proliferation, migration, and survival through overlapping intracellular signaling pathways. In vascular smooth muscle cells PDGF-BB induces FGF-2 expression. However, the effect of PDGF on the different forms of FGF-2 has not been elucidated. Here, we report that treatment of vascular aortic smooth muscle cells with PDGF-BB rapidly induces expression of 20.5 and 21 kDa, high molecular weight (HMW) FGF-2 that accumulates in the nucleus and nucleolus. Conversely, PDGF treatment has little or no effect on 18 kDa, low-molecular weight FGF-2 expression. PDGF-BB-induced upregulation of HMW FGF-2 expression is controlled by sustained activation of extracellular signal-regulated kinase (ERK)-1/2 and is abolished by actinomycin D. These data describe a novel interaction between PDGF-BB and FGF-2, and indicate that the nuclear forms of FGF-2 may mediate the effect of PDGF activity on vascular smooth muscle cells.

Preparation and mass spectrometric study of egg yolk antibody (IgY) against rabies virus.

PubMed

Sun, S; Mo, W; Ji, Y; Liu, S

2001-01-01

Rabies virus was used as the antigen to immunize laying chickens. Anti-rabies virus immunoglobulin Y(IgY) was isolated from yolks of the eggs laid by these chickens using a two-step salt precipitation and one-step gel filtration protocol. The purified IgY was reduced with dithiothreitol, and heavy chains (HC) and light chains (LC) were obtained. In addition, the purified IgY was digested with pepsin and the fragment with specific antigen binding properties (Fab) was produced. Using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOFMS), the average molecular weights of IgY, HC, LC, and Fab were determined as 167 250, 65 105, 18 660, and 45,359 Da, respectively. IgY has two structural differences compared with mammalian IgGs. First, the molecular weight of the heavy chain of IgY is larger than that of its mammalian counterpart, while the molecular weight of the light chain of IgY is smaller. Second, upon pepsin digestion, anti-rabies virus IgY is degraded into Fab, in contrast to mammalian IgG, which has been reported to be degraded into F(ab')(2) under the same conditions. Copyright 2001 John Wiley & Sons, Ltd.

Relationships between the morphology and thermoresponsive behavior in micro/nanostructured thermosetting matrixes containing a 4'-(hexyloxy)-4-biphenylcarbonitrile liquid crystal.

PubMed

Tercjak, Agnieszka; Mondragon, Iñaki

2008-10-07

Meso/nanostructured thermoresponsive thermosetting materials based on an epoxy resin modified with two different molecular weight amphiphilic poly(styrene- block-ethylene oxide) block copolymers (PSEO) and a low molecular weight liquid crystal, 4'-(hexyloxy)-4-biphenylcarbonitrile (HOBC), were investigated. A strong influence of the addition of PSEO on the morphology generated in HOBC--(diglicydyl ether of bisphenol A epoxy resin/ m-xylylenediamine) was detected, especially in the case of the addition of PSEO block copolymers with a higher PEO-block content and a lower molecular weight. The morphologies generated in the ternary systems also influenced the thermoresponsive behavior of the HOBC separated phase provoked by applying an external field, such as a temperature gradient and an electrical field. Thermal analysis of the investigated materials allowed for a better understanding of the relationships between generated morphology/thermo-optical properties/PSEO:HOBC ratio, and HOBC content. Controlling the relationship between the morphology and thermoresponsive behavior in micro/nanostructured thermosetting materials based on a 4'-(hexyloxy)-4-biphenylcarbonitrile liquid crystal allows the development of materials which can find application in thermo- and in some cases electroresponsive devices, with a high contrast ratio between transparent and opaque states.

The relative safety of gamma-ray, autoclave, and ethylene oxide gas sterilization of thermosetting polyurethane.

PubMed

Shintani, H

1995-01-01

Sterilization of polyurethane (PU) produces 4,4'-methylenedianiline (MDA), a known carcinogen, and various other compounds. The relationships of the components of PU to the formation of these compounds by sterilization were studied. Specimens of PU fabricated from different combinations of isocyanates and polyols were obtained from dialyzers. The molecular weight of the particular polyol was found to influence the production of MDA by sterilization. Sterilization also produced many unidentified compounds. MDA production was not always associated with the production of the other compounds. Compared with gamma-ray irradiation and ethylene oxide gas (EOG) sterilization, autoclave sterilization eluted more hydrophilic compounds. This phenomenon was significant for PUs produced from smaller-molecular-weight polyols. The combination of autoclave sterilization and a PU produced from a larger-molecular-weight polyol is recommended to minimize the production of potentially toxic compounds. Of the techniques studied, EOG sterilization produced the least amounts of MDA and the other compounds, but the residue of EOG is itself problematic. The risk posed by the amounts of MDA extracted was not significant, but the biological safety of the other compounds remains to be determined.

Characterization of dissolved organic matter in Dongjianghu Lake by UV-visible absorption spectroscopy with multivariate analysis.

PubMed

Zhu, Yanzhong; Song, Yonghui; Yu, Huibin; Liu, Ruixia; Liu, Lusan; Lv, Chunjian

2017-08-08

UV-visible absorption spectroscopy coupled with principal component analysis (PCA) and hierarchical cluster analysis (HCA) was applied to characterize spectroscopic components, detect latent factors, and investigate spatial variations of dissolved organic matter (DOM) in a large-scale lake. Twelve surface water samples were collected from Dongjianghu Lake in China. DOM contained lignin and quinine moieties, carboxylic acid, microbial products, and aromatic and alkyl groups, which in the northern part of the lake was largely different from the southern part. Fifteen spectroscopic indices were deduced from the absorption spectra to indicate molecular weight or humification degree of DOM. The northern part of the lake presented the smaller molecular weight or the lower humification degree of DOM than the southern part. E 2/4 , E 3/4 , E 2/3 , and S 2 were latent factors of characterizing the molecular weight of DOM, while E 2/5 , E 3/5 , E 2/6 , E 4/5 , E 3/6 , and A 2/1 were latent factors of evaluating the humification degree of DOM. The UV-visible absorption spectroscopy combined with PCA and HCA may not only characterize DOM fractions of lakes, but may be transferred to other types of waterscape.

Model-based intensification of a fed-batch microbial process for the maximization of polyhydroxybutyrate (PHB) production rate.

PubMed

Penloglou, Giannis; Vasileiadou, Athina; Chatzidoukas, Christos; Kiparissides, Costas

2017-08-01

An integrated metabolic-polymerization-macroscopic model, describing the microbial production of polyhydroxybutyrate (PHB) in Azohydromonas lata bacteria, was developed and validated using a comprehensive series of experimental measurements. The model accounted for biomass growth, biopolymer accumulation, carbon and nitrogen sources utilization, oxygen mass transfer and uptake rates and average molecular weights of the accumulated PHB, produced under batch and fed-batch cultivation conditions. Model predictions were in excellent agreement with experimental measurements. The validated model was subsequently utilized to calculate optimal operating conditions and feeding policies for maximizing PHB productivity for desired PHB molecular properties. More specifically, two optimal fed-batch strategies were calculated and experimentally tested: (1) a nitrogen-limited fed-batch policy and (2) a nitrogen sufficient one. The calculated optimal operating policies resulted in a maximum PHB content (94% g/g) in the cultivated bacteria and a biopolymer productivity of 4.2 g/(l h), respectively. Moreover, it was demonstrated that different PHB grades with weight average molecular weights of up to 1513 kg/mol could be produced via the optimal selection of bioprocess operating conditions.

Using ozone to reduce recalcitrant compounds and to enhance biodegradability of pulp and paper effluents.

PubMed

Bijan, L; Mohseni, M

2004-01-01

The effect of ozone based oxidation on removing recalcitrant organic matter (ROM) and enhancing the biodegradability of alkaline bleach plant effluent was investigated. A bubble column ozonation tower was used in the study. The experiments were carried out at different temperatures (20 degrees C and 60 degrees C) and pH (9 and 11), with a number of biological and chemical parameters being monitored including BOD5, COD, TC, pH, color, and molecular weight distribution of organics (nominal cut off of 1,000 Da). Biodegradability of the effluent was determined based on BOD5/COD of the wastewater throughout the process. For all the experiments, ozonation enhanced the biodegradability of the effluent by 30-40%, which was associated with noticeable removal of ROM including high molecular weight (HMW) and color-causing organics by about 30% and 60%, respectively. While the biodegradability of HMW fraction increased by about 50%, there was no biodegradability improvement for low molecular weight (LMW) portion, which was originally readily biodegradable (with BOD5/COD of about 0.5). Statistical analysis of variance (ANOVA) revealed neither pH nor temperature played significant role on the ozonation process at 95% confidence level.

In vivo oxidation in remelted highly cross-linked retrievals.

PubMed

Currier, B H; Van Citters, D W; Currier, J H; Collier, J P

2010-10-20

Elimination of free radicals to prevent oxidation has played a major role in the development and product differentiation of the latest generation of highly cross-linked ultra-high molecular weight polyethylene bearing materials. In the current study, we (1) examined oxidation in a series of retrieved remelted highly cross-linked ultra-high molecular weight polyethylene bearings from a number of device manufacturers and (2) compared the retrieval results with findings for shelf-stored control specimens. The hypothesis was that radiation-cross-linked remelted ultra-high molecular weight polyethylene would maintain oxidative stability in vivo comparable with the stability during shelf storage and in published laboratory aging tests. Fifty remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners and nineteen remelted highly cross-linked ultra-high molecular weight polyethylene tibial inserts were received after retrieval from twenty-one surgeons from across the U.S. Thirty-two of the retrievals had been in vivo for two years or more. Each was measured for oxidation with use of Fourier transform infrared spectroscopy. A control series of remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners from three manufacturers was analyzed with electron paramagnetic resonance spectroscopy to measure free radical content and with Fourier transform infrared spectroscopy to measure oxidation initially and after eight to nine years of shelf storage in air. The never-implanted, shelf-aged controls had no measurable free-radical content initially or after eight to nine years of shelf storage. The never-implanted controls showed no increase in oxidation during shelf storage. Oxidation measurements showed measurable oxidation in 22% of the retrieved remelted highly cross-linked liners and inserts after an average of two years in vivo. Because never-implanted remelted highly cross-linked ultra-high molecular weight polyethylene materials had no measurable free-radical concentration and no increase in oxidation during shelf storage, these materials were expected to be oxidation-resistant in vivo. However, some remelted highly cross-linked ultra-high molecular weight polyethylene retrievals showed measurable oxidation after an average of more than two years in vivo. This apparent departure from widely expected behavior requires continued study of the process of in vivo oxidation of ultra-high molecular weight polyethylene materials.

Features of Extrusion Processing of Ultrahigh Molecular Weight Polyethylene. Experiment and Theory

NASA Astrophysics Data System (ADS)

Skul‧skii, O. I.; Slavnov, E. V.

2018-05-01

Experimental studies have been made of the permissible regimes of processing ultrahigh molecular weight polyethylene GUR 2122 with molecular mass of 4.5 million g/moles in a laboratory extruder with an auger diameter 32 mm and a ratio L/D = 20 at temperatures of 155-165oC. On the basis of rotational viscometry, the rheological properties of the melt are described. A mathematical model and a numerical method for calculating the motion of ultrahigh molecular weight polyethylene melt in the auger and in the moulding rigging are proposed. The velocity and stress fields have been determined.

Seed maturation associated transcriptional programs and regulatory networks underlying genotypic difference in seed dormancy and size/weight in wheat (Triticum aestivum L.).

PubMed

Yamasaki, Yuji; Gao, Feng; Jordan, Mark C; Ayele, Belay T

2017-09-16

Maturation forms one of the critical seed developmental phases and it is characterized mainly by programmed cell death, dormancy and desiccation, however, the transcriptional programs and regulatory networks underlying acquisition of dormancy and deposition of storage reserves during the maturation phase of seed development are poorly understood in wheat. The present study performed comparative spatiotemporal transcriptomic analysis of seed maturation in two wheat genotypes with contrasting seed weight/size and dormancy phenotype. The embryo and endosperm tissues of maturing seeds appeared to exhibit genotype-specific temporal shifts in gene expression profile that might contribute to the seed phenotypic variations. Functional annotations of gene clusters suggest that the two tissues exhibit distinct but genotypically overlapping molecular functions. Motif enrichment predicts genotypically distinct abscisic acid (ABA) and gibberellin (GA) regulated transcriptional networks contribute to the contrasting seed weight/size and dormancy phenotypes between the two genotypes. While other ABA responsive element (ABRE) motifs are enriched in both genotypes, the prevalence of G-box-like motif specifically in tissues of the dormant genotype suggests distinct ABA mediated transcriptional mechanisms control the establishment of dormancy during seed maturation. In agreement with this, the bZIP transcription factors that co-express with ABRE enriched embryonic genes differ with genotype. The enrichment of SITEIIATCYTC motif specifically in embryo clusters of maturing seeds irrespective of genotype predicts a tissue specific role for the respective TCP transcription factors with no or minimal contribution to the variations in seed dormancy. The results of this study advance our understanding of the seed maturation associated molecular mechanisms underlying variation in dormancy and weight/size in wheat seeds, which is a critical step towards the designing of molecular strategies for enhancing seed yield and quality.

The influence of malalignment and ageing following sterilisation by gamma irradiation in an inert atmosphere on the wear of ultra-high-molecular-weight polyethylene in patellofemoral replacements

PubMed Central

Maiti, Raman; Cowie, Raelene M; Fisher, John; Jennings, Louise M

2017-01-01

Complications of patellofemoral arthroplasty often occur soon after implantation and, as well as other factors, can be due to the design of the implant or its surgical positioning. A number of studies have previously considered the wear of ultra-high-molecular-weight polyethylene patellae following suboptimal implantation; however, studies have primarily been carried out under a limited number of degrees of freedom. The aim of this study was to develop a protocol to assess the wear of patellae under a malaligned condition in a six-axis patellofemoral joint simulator. The malalignment protocol hindered the tracking of the patella centrally in the trochlear groove and imparted a constant 5° external rotation (tilt) on the patella button. Following 3 million cycles of wear simulation, this condition had no influence on the wear of ultra-high-molecular-weight polyethylene patellae aged for 4 years compared to well-positioned non-aged implants (p > 0.05). However, under the malaligned condition, ultra-high-molecular-weight polyethylene patellae aged 8–10 years after unpacking (following sterilisation by gamma irradiation in an inert atmosphere) and worn ultra-high-molecular-weight polyethylene components also aged 4 years after unpacking (following the same sterilisation process) exhibited a high rate of wear. Fatigue failure due to elevated contact stress led to delamination of the ultra-high-molecular-weight polyethylene and in some cases complete failure of the patellae. The results suggest that suboptimal tracking of the patella in the trochlear groove and tilt of the patella button could have a significant effect on the wear of ultra-high-molecular-weight polyethylene and could lead to implant failure. PMID:28661229

The influence of malalignment and ageing following sterilisation by gamma irradiation in an inert atmosphere on the wear of ultra-high-molecular-weight polyethylene in patellofemoral replacements.

PubMed

Maiti, Raman; Cowie, Raelene M; Fisher, John; Jennings, Louise M

2017-07-01

Complications of patellofemoral arthroplasty often occur soon after implantation and, as well as other factors, can be due to the design of the implant or its surgical positioning. A number of studies have previously considered the wear of ultra-high-molecular-weight polyethylene patellae following suboptimal implantation; however, studies have primarily been carried out under a limited number of degrees of freedom. The aim of this study was to develop a protocol to assess the wear of patellae under a malaligned condition in a six-axis patellofemoral joint simulator. The malalignment protocol hindered the tracking of the patella centrally in the trochlear groove and imparted a constant 5° external rotation (tilt) on the patella button. Following 3 million cycles of wear simulation, this condition had no influence on the wear of ultra-high-molecular-weight polyethylene patellae aged for 4 years compared to well-positioned non-aged implants (p > 0.05). However, under the malaligned condition, ultra-high-molecular-weight polyethylene patellae aged 8-10 years after unpacking (following sterilisation by gamma irradiation in an inert atmosphere) and worn ultra-high-molecular-weight polyethylene components also aged 4 years after unpacking (following the same sterilisation process) exhibited a high rate of wear. Fatigue failure due to elevated contact stress led to delamination of the ultra-high-molecular-weight polyethylene and in some cases complete failure of the patellae. The results suggest that suboptimal tracking of the patella in the trochlear groove and tilt of the patella button could have a significant effect on the wear of ultra-high-molecular-weight polyethylene and could lead to implant failure.

Polar organic compounds in pore waters of the Chesapeake Bay impact structure, Eyreville core hole: Character of the dissolved organic carbon and comparison with drilling fluids

USGS Publications Warehouse

Rostad, C.E.; Sanford, W.E.

2009-01-01

Pore waters from the Chesapeake Bay impact structure cores recovered at Eyreville Farm, Northampton County, Virginia, were analyzed to characterize the dissolved organic carbon. After squeezing or centrifuging, a small volume of pore water, 100 ??L, was taken for analysis by electrospray ionization-mass spectrometry. Porewater samples were analyzed directly without filtration or fractionation, in positive and negative mode, for polar organic compounds. Spectra in both modes were dominated by low-molecular-weight ions. Negative mode had clusters of ions differing by -60 daltons, possibly due to increasing concentrations of inorganic salts. The numberaverage molecular weight and weight-average molecular weight values for the pore waters from the Chesapeake Bay impact structure are higher than those reported for other aquatic sources of natural dissolved organic carbon as determined by electrospray ionization-mass spectrometry. In order to address the question of whether drilling mud fluids may have contaminated the pore waters during sample collection, spectra from the pore waters were compared to spectra from drilling mud fluids. Ions indicative of drilling mud fluids were not found in spectra from the pore waters, indicating there was no detectable contamination, and highlighting the usefulness of this analytical technique for detecting potential contamination during sample collection. ?? 2009 The Geological Society of America.

Cartilage collagen damage in hip osteoarthritis similar to that seen in knee osteoarthritis; a case-control study of relationship between collagen, glycosaminoglycan and cartilage swelling.

PubMed

Hosseininia, Shahrzad; Lindberg, Lisbeth R; Dahlberg, Leif E

2013-01-09

It remains to be shown whether OA shares molecular similarities between different joints in humans. This study provides evidence for similarities in cartilage molecular damage in osteoarthritic (OA) joints. Articular cartilage from osteoarthritic hip joints were analysed and compared to non-OA controls regarding collagen, glycosaminoglycan and water content. Femoral heads from 16 osteoarthritic (OA) and 20 reference patients were obtained from hip replacement surgery due to OA and femoral neck fracture, respectively. Cartilage histological changes were assessed by Mankin grading and denatured collagen type II immunostaining and cartilage was extracted by α-chymotrypsin. Hydroxyproline and Alcian blue binding assays were used to measure collagen and glycosaminoglycan (GAG) content, respectively. Mankin and immunohistology scores were significantly higher in hip OA samples than in reference samples. Cartilage water content was 6% higher in OA samples than in references. 2.5 times more collagen was extracted from OA than from reference samples. There was a positive association between water content and percentage of extractable collagen pool (ECP) in both groups. The amounts of collagen per wet and dry weights did not differ statistically between OA and reference cartilage. % Extractable collagen was not related to collagen per dry weight in either group. However when collagen was expressed by wet weight there was a negative correlation between % extractable and collagen in OA cartilage. The amount of GAG per wet weight was similar in both groups but the amount of GAG per dry weight was higher in OA samples compared to reference samples, which suggests a capacity for GAG biosynthesis in hip OA cartilage. Neither of the studied parameters was related to age in either group. Increased collagen extractability and water content in human hip cartilage is associated with OA pathology and can be observed at early stages of the degenerative hip OA process. Our results suggest a common degradative pathway of collagen in articular cartilage of different joints. Furthermore, the study suggests that biochemical changes precede more overt OA changes and that chondrocytes may have a capability to compensate molecular loss in the early phase of OA.

Effect of molecular topology on the transport properties of dendrimers in dilute solution at Θ temperature: A Brownian dynamics study

NASA Astrophysics Data System (ADS)

Bosko, Jaroslaw T.; Ravi Prakash, J.

2008-01-01

Structure and transport properties of dendrimers in dilute solution are studied with the aid of Brownian dynamics simulations. To investigate the effect of molecular topology on the properties, linear chain, star, and dendrimer molecules of comparable molecular weights are studied. A bead-spring chain model with finitely extensible springs and fluctuating hydrodynamic interactions is used to represent polymer molecules under Θ conditions. Structural properties as well as the diffusivity and zero-shear-rate intrinsic viscosity of polymers with varied degrees of branching are analyzed. Results for the free-draining case are compared to and found in very good agreement with the Rouse model predictions. Translational diffusivity is evaluated and the difference between the short-time and long-time behavior due to dynamic correlations is observed. Incorporation of hydrodynamic interactions is found to be sufficient to reproduce the maximum in the intrinsic viscosity versus molecular weight observed experimentally for dendrimers. Results of the nonequilibrium Brownian dynamics simulations of dendrimers and linear chain polymers subjected to a planar shear flow in a wide range of strain rates are also reported. The flow-induced molecular deformation of molecules is found to decrease hydrodynamic interactions and lead to the appearance of shear thickening. Further, branching is found to suppress flow-induced molecular alignment and deformation.

Serum cholesterol reduction by feeding a high-cholesterol diet containing a lower-molecular-weight polyphenol fraction from peanut skin.

PubMed

Tamura, Tomoko; Inoue, Naoko; Shimizu-Ibuka, Akiko; Tadaishi, Miki; Takita, Toshichika; Arai, Soichi; Mura, Kiyoshi

2012-01-01

Feeding a high-cholesterol diet with a water-soluble peanut skin polyphenol fraction to rats reduced their plasma cholesterol level, with an increase in fecal cholesterol excretion. The hypocholesterolemic effect was greater with the lower-molecular-weight rather than higher-molecular-weight polyphenol fraction. This effect was possibly due to some oligomeric polyphenols which reduced the solubility of dietary cholesterol in intestinal bile acid-emulsified micelles.

Synthesis and Structural Characterization of New Light Molecular Weight Inorganic Oxidizers and Related Derivatives. Volume: 2

DTIC Science & Technology

1993-02-01

of the strong inductive effect of the five fluorine ligands attached to the tellurium atom. 34 It is prepared under anhydrous conditions according to...MOLECULAR WEIGHT INORGANIC OXIDIZERS AND RELATED DERIVATIVES. VOLUME: II Professor G. J. Schrobilgen McMaster University Department of Chemistry...C: F04611-91-K-0004 Molecular Weight Inorganic Oxidizers and Relative PE: 62302F SDerivatives: Volume II 1PR: 5730 6. AUTHOFR(S) TA: 0*( C

Raman analysis of polyethylene glycols and polyethylene oxides

NASA Astrophysics Data System (ADS)

Sagitova, E. A.; Prokhorov, K. A.; Nikolaeva, G. Yu; Baimova, A. V.; Pashinin, P. P.; Yarysheva, A. Yu; Mendeleev, D. I.

2018-04-01

We present Raman study of commercial liquids and powders of polyethylene glycols and polyethylene oxides with the average molecular weight from 400 Da to 10000 kDa. The most significant spectral changes were observed for the range of the molecular weights, where the liquid/semisolid transition has occurred. For the powders we revealed increase in the content of the molecules in the helical conformation and in the content of the monoclinic crystalline phase with growth of the molecular weight.

Should Low Molecular Weight PSMA Targeted Ligands Get Bigger and Use Albumin Ligands for PSMA Targeting?

PubMed

Huang, Steve S; Heston, Warren D W

2017-01-01

Prostate Specific Membrane Antigen (PSMA) is strongly expressed in prostate cancer. Recently a number of low-molecular-weight inhibitors have demonstrated excellent PSMA targeting activity for both imaging as well as Lutecium-177 radiotherapy in human trials. The paper by Choy et al raises the question of whether we can further increase the effectiveness of PSMA targeted therapy by adding an albumin-binding entity to low-molecular-weight agents.

High-molecular-weight tropomyosins localize to the contractile rings of dividing CNS cells but are absent from malignant pediatric and adult CNS tumors.

PubMed

Hughes, Julie A I; Cooke-Yarborough, Claire M; Chadwick, Nigel C; Schevzov, Galina; Arbuckle, Susan M; Gunning, Peter; Weinberger, Ron P

2003-04-01

Tropomyosin has been implicated in the control of actin filament dynamics during cell migration, morphogenesis, and cytokinesis. In order to gain insight into the role of tropomyosins in cell division, we examined their expression in developing and neoplastic brain tissue. We found that the high-molecular-weight tropomyosins are downregulated at birth, which correlates with glial cell differentiation and withdrawal of most cells from the cell cycle. Expression of these isoforms was restricted to proliferative areas in the embryonic brain and was absent from the adult, where the majority of cells are quiescent. However, they were induced under conditions where glial cells became proliferative in response to injury. During cytokinesis, these tropomyosin isoforms were associated with the contractile ring. We also investigated tropomyosin expression in neoplastic CNS tissues. Low-grade astrocytic tumors expressed high-molecular-weight tropomyosins, while highly malignant CNS tumors of diverse origin did not (P

The binding of sodium dodecyl sulphate to various proteins

PubMed Central

Pitt-Rivers, Rosalind; Impiombato, F. S. Ambesi

1968-01-01

1. The binding of sodium dodecyl sulphate to proteins by equilibrium dialysis was investigated. 2. Most of the proteins studied bound 90–100% of their weight of sodium dodecyl sulphate. 3. The glycoproteins studied bound 70–100% of their weight of sodium dodecyl sulphate, calculated in terms of the polypeptide moiety of the molecule. 4. Proteins not containing S·S groups bound about 140% of their weight of sodium dodecyl sulphate. 5. Reduction of four proteins containing S·S groups caused a rise in sodium dodecyl sulphate binding to 140% of the weight of protein. 6. The apparent micellar molecular weights of the protein–sodium dodecyl sulphate complexes were measured by the dye-solubilization method; they were all found to have approximately the same micellar molecular weight (34000–41000) irrespective of the molecular weight of the protein to which they were attached. PMID:4177067

Definition of high-performance membranes - from the clinical point of view.

PubMed

Saito, Akira

2011-01-01

Global knowledge of the molecular target of uremic toxins (UTs) was significantly different in the 1980s than it is now. In 1971, Babb et al. hypothesized that UTs such as neurotoxin existed in mid-sized molecules ranging from 300 to 3,000 Da. In the 1980s, larger molecular weight substances > 5,000 Da were targeted for removal, as well as small and medium size toxins in Japan, while urea was considered a surrogate marker of UTs, and Kt/V for urea was used as a measure of dialysis dose in the USA. In Japan, albumin-bound toxins in addition to low-molecular-weight proteins were targeted for removal as glomerular filtration in the normal kidney. As binding capacity of albumin is significantly lowered and, on the other hand, the α-helical content of albumin also lowered in uremic patients because of binding of UTs to albumin, a small amount of albumin should be removed to stimulate the synthesis of new albumin. KF101 C-2 (EVAL) used as a high-performance dialysis membrane (HPM) at the first step, in which approximately 7 g of albumin is removed per dialysis session. It resulted in lowered plasma albumin levels in hemodialysis patients, although accumulated levels of low-molecular-weight proteins were significantly lowered. Therefore, the Japanese Society of Dialysis Therapy has recommended limitation of albumin removal to < 3 g/session by the second generation of HPMs. Many different HPMs have been developed since the Japanese Society of HPM was first organized in 1985. Approximately 98% of the dialyzers used in Japan employ HPMs. New technology is required to suppress fouling on the surface and in the pores of HPMs. This would maintain permeation of inflammatory cytokines during dialysis sessions. Copyright © 2011 S. Karger AG, Basel.

Constructing a molecular theory of self-assembly: Interplay of ideas from surfactants and block copolymers.

PubMed

Nagarajan, Ramanathan

2017-06-01

Low molecular weight surfactants and high molecular weight block copolymers display analogous self-assembly behavior in solutions and at interfaces, generating nanoscale structures of different shapes. Understanding the link between the molecular structure of these amphiphiles and their self-assembly behavior has been the goal of theoretical studies. Despite the analogies between surfactants and block copolymers, models predicting their self-assembly behavior have evolved independent of one another, each overlooking the molecular feature considered critical to the other. In this review, we focus on the interplay of ideas pertaining to surfactants and block copolymers in three areas of self-assembly. First, we show how improved free energy models have evolved by applying ideas from surfactants to block copolymers and vice versa, giving rise to a unitary theoretical framework and better predictive capabilities for both classes of amphiphiles. Second we show that even though molecular packing arguments are often used to explain aggregate shape transitions resulting from self-assembly, the molecular packing considerations are more relevant in the case of surfactants whereas free energy criteria are relevant for block copolymers. Third, we show that even though the surfactant and block copolymer aggregates are small nanostructures, the size differences between them is significant enough to make the interfacial effects control the solubilization of molecules in surfactant micelles while the bulk interactions control the solubilization in block copolymer micelles. Finally, we conclude by identifying recent theoretical progress in adapting the micelle model to a wide variety of self-assembly phenomena and the challenges to modeling posed by emerging novel classes of amphiphiles with complex biological, inorganic or nanoparticle moieties. Published by Elsevier B.V.

Circulating form of beta-2-microglobulin in dialysis patients.

PubMed

Gagnon, R F; Somerville, P; Thomson, D M

1988-01-01

The circulating profile of beta-2-microglobulin (beta 2M) was determined in 8 end-stage renal disease patients on long-term dialysis (6 on hemodialysis, 2 on CAPD) by measuring beta 2M in different fraction after molecular sieve separation of their sera. Four patients had carpal tunnel syndrome with demonstrated amyloid in excised wrist tissues of which 2 were positive for beta 2M. In all patients despite very high blood levels (34.3-63.1 mg/l), beta 2M eluted exclusively as a single peak in the molecular weight region of about 12,000 daltons on a calibrated Sephacryl S-200 column. Recoveries from within the peak accounted for 96% of the applied beta 2M serum concentrations. These results were confirmed by molecular sieve separation of the enriched beta 2M-containing fractions by high-pressure liquid chromatography. We conclude that immunoreactive beta 2M in dialysis patients circulates as an intact monomer without evidence for the formation of aggregates or fragments. The pathogenesis of tissue deposition of this low-molecular-weight protein and its polymerisation to form a specific amyloid remains to be defined.

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) of low molecular weight organic compounds and synthetic polymers using zinc oxide (ZnO) nanoparticles.

PubMed

Watanabe, Takehiro; Kawasaki, Hideya; Yonezawa, Tetsu; Arakawa, Ryuichi

2008-08-01

We have developed surface-assisted laser desorption/ionization mass spectrometry using zinc oxide (ZnO) nanoparticles with anisotropic shapes (ZnO-SALDI-MS). The mass spectra showed low background noises in the low m/z, i.e. less than 500 u region. Thus, we succeeded in SALDI ionization on low molecular weight organic compounds, such as verapamil hydrochloride, testosterone, and polypropylene glycol (PPG) (average molecular weight 400) without using a liquid matrix or buffers such as citric acids. In addition, we found that ZnO-SALDI has advantages in post-source decay (PSD) analysis and produced a simple mass spectrum for phospholipids. The ZnO-SALDI spectra for synthetic polymers of polyethylene glycol (PEG), polystyrene (PS) and polymethylmethacrylate (PMMA) showed the sensitivity and molecular weight distribution to be comparable to matrix-assisted laser desorption/ionization (MALDI) spectra with a 2,5-dihydroxybenzoic acid (DHB) matrix. ZnO-SALDI shows good performance for synthetic polymers as well as low molecular weight organic compounds. Copyright (c) 2008 John Wiley & Sons, Ltd.

Complete Molecular Weight Profiling of Low-Molecular Weight Heparins Using Size Exclusion Chromatography-Ion Suppressor-High-Resolution Mass Spectrometry.

PubMed

Zaia, Joseph; Khatri, Kshitij; Klein, Joshua; Shao, Chun; Sheng, Yuewei; Viner, Rosa

2016-11-01

Low-molecular weight heparins (LMWH) prepared by partial depolymerization of unfractionated heparin are used globally to treat coagulation disorders on an outpatient basis. Patent protection for several LMWH has expired and abbreviated new drug applications have been approved by the Food and Drug Administration. As a result, reverse engineering of LMWH for biosimilar LMWH has become an active global endeavor. Traditionally, the molecular weight distributions of LMWH preparations have been determined using size exclusion chromatography (SEC) with optical detection. Recent advances in liquid chromatography-mass spectrometry methods have enabled exact mass measurements of heparin saccharides roughly up to degree-of-polymerization 20, leaving the high molecular weight half of the LMWH preparation unassigned. We demonstrate a new LC-MS system capable of determining the exact masses of complete LMWH preparations, up to dp30. This system employed an ion suppressor cell to desalt the chromatographic effluent online prior to the electrospray mass spectrometry source. We expect this new capability will impact the ability to define LMWH mixtures favorably.

[The analysis of the low and medium molecular weight substances for differential diagnostics of deaths from acute small-focal myocardial infarction and other forms of cardiac pathology].

PubMed

Edelev, N S; Obuhova, L M; Edelev, I S; Katirkina, A A

The objective of the present study was to analyze the possibilities for the use of the low and medium molecular weight substances for differential diagnostics of deaths from acute small-focal myocardial infarction and other forms of cardiac pathology. We determined the amount of the low and medium molecular weight substances in the urine obtained from the subjects who had died as a result of chronic coronary heart disease, acute myocardial infarction, and alcoholic cardiomyopathy. The levels of the low and medium molecular weight substances in the urine were measured by the method of N.Ya. Malakhov in the modification of T.V. Kopytova [5]. The study has demonstrated the appearance of the products of cardiomyocyte degradation (giving rise to a peak at a wavelength of 278 nm) in the fraction of the low and medium molecular weight substances of the urine from the patients suffering from acute small-focal myocardial infarction and some other forms of cardiac pathology.

Brominated flame retardants in Chinese air before and after the phase out of polybrominated diphenyl ethers

NASA Astrophysics Data System (ADS)

Li, Wen-Long; Qi, Hong; Ma, Wan-Li; Liu, Li-Yan; Zhang, Zhi; Mohammed, Mohammed O. A.; Song, Wei-Wei; Zhang, Zifeng; Li, Yi-Fan

2015-09-01

Brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs) and novel non-BDE flame retardants (NBFRs), were analyzed in Chinese air during China's POPs Soil and Air Monitoring Program Phase I (SAMP-I) and Phase II (SAMP-II). The levels of Σ12PBDEs and Σ6NBFRs in urban sites were significantly higher than those in rural sites and background sites. The higher detection rate and concentrations of high molecular weight PBDEs and NBFRs in Phase II indicated the changing of the commercial pattern of BFRs after the phase out of PBDEs in China. Temperature was the major factor affecting the seasonal variations of molecular weight BFRs in atmosphere. A significant correlation between BFRs concentration and gross domestic product (GDP) was observed, with the GDP parameter explained 59.4% and 72.7% of the total variability for Octa-BDEs and low molecular weight NBFRs, respectively. Our findings indicated an evolving commercial usage of BFRs from SAMP-I to SAMP-II, i.e. shifting from lower molecular weight to higher molecular weight congeners in China.

MAPLE deposition of PLGA:PEG films for controlled drug delivery: Influence of PEG molecular weight

NASA Astrophysics Data System (ADS)

Paun, Irina Alexandra; Moldovan, Antoniu; Luculescu, Catalin Romeo; Staicu, Angela; Dinescu, Maria

2012-09-01

Implantable devices consisting of indomethacin (INC) cores coated with poly(lactide-co-glycolide):polyethylene glycol films (i.e. PLGA:PEG films) deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) were produced. To predict their behavior after implantation inside the body, the implants were studied in vitro, in media similar with those encountered inside the body (phosphate buffered saline (PBS) pH 7.4 and blood). The influence of the molecular weight of PEG (i.e. low (1450 Da) versus high (10 kDa) molecular weights) on the characteristics of the implants was investigated, in terms of morphology, blood compatibility and kinetics of the drug release. The use of PEG of high molecular weight resulted in larger pores on the implants surfaces, enhanced blood compatibility of the implants and higher drug delivery rates. For both molecular weights PEGs, sustained release of INC was maintained over a three weeks interval. Theoretical fitting of the drug release data with Higuchi's model indicated that the INC was released mainly by diffusion, most probably through the pores formed in PLGA:PEG films during PBS immersion.

Derepression of the Azotobacter vinelandii siderophore system, using iron-containing minerals to limit iron repletion.

PubMed Central

Page, W J; Huyer, M

1984-01-01

Azotobacter vinelandii solubilized iron from certain minerals using only dihydroxybenzoic acid, which appeared to be produced constitutively. Solubilization of iron from other minerals required dihydroxybenzoic acid and the siderophore N,N'-bis-(2,3- dihydroxybenzoyl )-L-lysine ( azotochelin ) or these chelators plus the yellow-green fluorescent siderophore azotobactin . In addition to this sequential production of siderophores, cells also demonstrated partial to hyperproduction relative to the iron-limited control. The iron sources which caused partial derepression of the siderophores caused derepression of all the high-molecular-weight iron-repressible outer membrane proteins except a 77,000-molecular-weight protein, which appeared to be coordinated with azotobactin production. Increased siderophore production correlated with increased production of outer membrane proteins with molecular weights of 93,000, 85,000, and 77,000, but an 81,000-molecular-weight iron-repressible protein appeared at a constant level despite the degree of derepression. When iron was readily available, it appeared to complex with a 60,000-molecular-weight protein believed to form a surface layer on the A. vinelandii cell. Images PMID:6233258

Glycation inhibits trichloroacetic acid (TCA)-induced whey protein precipitation

USDA-ARS?s Scientific Manuscript database

Four different WPI saccharide conjugates were successfully prepared to test whether glycation could inhibit WPI precipitation induced by trichloroacetic acid (TCA). Conjugates molecular weights after glycation were analyzed with SDS-PAGE. No significant secondary structure change due to glycation wa...

SAPONIFICATION EQUIVALENT OF DASAMULA TAILA

PubMed Central

Saxena, R. B.

1994-01-01

Saponification equivalent values of Dasamula taila are very useful for the technical and analytical work. It gives the mean molecular weight of the glycerides and acids present in Dasamula Taila. Saponification equivalent values of Dasamula taila are reported in different packings. PMID:22556683

Constructing Phylogenies.

ERIC Educational Resources Information Center

Bilardello, Nicholas; Valdes, Linda

1998-01-01

Introduces a method for constructing phylogenies using molecular traits and elementary graph theory. Discusses analyzing molecular data and using weighted graphs, minimum-weight spanning trees, and rooted cube phylogenies to display the data. (DDR)

Influence of excess diamine on properties of PMR polyimide resins and composites

NASA Technical Reports Server (NTRS)

Hurwitz, F. I.

1980-01-01

By varying the stoichiometry of the reactants in the preparation of PMR polyimide resin, changes occur in molecular weight distribution which influence the rheological properties and thus the processability of the resin, as well as the mechanical properties of the composite. The influence of 1-10 percent molar excess MDA on the molecular weight distribution and rheological properties of an imidized PMR system were exposed. Molecular weight distribution is characterized by gel permeation chromatography of the imidized molding compound; shear viscosity is related to changes in average molecular weight. The thermo-oxidative stability at 600 F, glass transition temperature, flexural and interlaminar shear properties of PMR polyimide/Celion 6000 graphite fiber composites are compared as a function of the percent excess MDA in the monomer reactant mixture.

Selenium/Tellurium-Containing Hyperbranched Polymers: Effect of Molecular Weight and Degree of Branching on Glutathione Peroxidase-Like Activity.

PubMed

Thomas, Joice; Dong, Zeyuan; Dehaen, Wim; Smet, Mario

2012-12-21

A series of novel hyperbranched polyselenides and polytellurides with multiple catalytic sites at the branching units has been synthesized via the polycondensation of A2 + B3 monomers. The GPx-like activities of these polymer mimics were assessed and it was found that the polytellurides showed higher GPx-like activities than the corresponding polyselenides. Interestingly, the polymers with higher molecular weights and degree of branching (DB) showed higher GPx-like activities than the analogous lower molecular weight polymer. The enhancement in the catalytical activity of the hyperbranched polymers with increasing molecular weight affirmed the importance of the incorporation of multiple catalytic groups in the macromolecule which increases the local concentration of catalytic sites. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Increase in 4-coumaryl alcohol units during lignification in alfalfa (Medicago sativa) alters the extractability and molecular weight of lignin.

PubMed

Ziebell, Angela; Gracom, Kristen; Katahira, Rui; Chen, Fang; Pu, Yunqiao; Ragauskas, Art; Dixon, Richard A; Davis, Mark

2010-12-10

The lignin content of biomass can impact the ease and cost of biomass processing. Lignin reduction through breeding and genetic modification therefore has potential to reduce costs in biomass-processing industries (e.g. pulp and paper, forage, and lignocellulosic ethanol). We investigated compositional changes in two low-lignin alfalfa (Medicago sativa) lines with antisense down-regulation of p-coumarate 3-hydroxylase (C3H) or hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyltransferase (HCT). We investigated whether the difference in reactivity during lignification of 4-coumaryl alcohol (H) monomers versus the naturally dominant sinapyl alcohol and coniferyl alcohol lignin monomers alters the lignin structure. Sequential base extraction readily reduced the H monomer content of the transgenic lines, leaving a residual lignin greatly enriched in H subunits; the extraction profile highlighted the difference between the control and transgenic lines. Gel permeation chromatography of isolated ball-milled lignin indicated significant changes in the weight average molecular weight distribution of the control versus transgenic lines (CTR1a, 6000; C3H4a, 5500; C3H9a, 4000; and HCT30a, 4000).

Chemistry of gluten proteins.

PubMed

Wieser, Herbert

2007-04-01

Gluten proteins play a key role in determining the unique baking quality of wheat by conferring water absorption capacity, cohesivity, viscosity and elasticity on dough. Gluten proteins can be divided into two main fractions according to their solubility in aqueous alcohols: the soluble gliadins and the insoluble glutenins. Both fractions consist of numerous, partially closely related protein components characterized by high glutamine and proline contents. Gliadins are mainly monomeric proteins with molecular weights (MWs) around 28,000-55,000 and can be classified according to their different primary structures into the alpha/beta-, gamma- and omega-type. Disulphide bonds are either absent or present as intrachain crosslinks. The glutenin fraction comprises aggregated proteins linked by interchain disulphide bonds; they have a varying size ranging from about 500,000 to more than 10 million. After reduction of disulphide bonds, the resulting glutenin subunits show a solubility in aqueous alcohols similar to gliadins. Based on primary structure, glutenin subunits have been divided into the high-molecular-weight (HMW) subunits (MW=67,000-88,000) and low-molecular-weight (LMW) subunits (MW=32,000-35,000). Each gluten protein type consists or two or three different structural domains; one of them contains unique repetitive sequences rich in glutamine and proline. Native glutenins are composed of a backbone formed by HMW subunit polymers and of LMW subunit polymers branched off from HMW subunits. Non-covalent bonds such as hydrogen bonds, ionic bonds and hydrophobic bonds are important for the aggregation of gliadins and glutenins and implicate structure and physical properties of dough.

Biodegradable in situ gelling delivery systems containing pilocarpine as new antiglaucoma formulations: effect of a mercaptoacetic acid/N-isopropylacrylamide molar ratio

PubMed Central

Lai, Jui-Yang

2013-01-01

Ocular drug delivery is one of the most commonly used treatment modalities in the management of glaucoma. We have recently proposed the use of gelatin and poly(N-isopropylacrylamide) (PNIPAAm) graft copolymers as biodegradable in situ forming delivery systems for the intracameral administration of antiglaucoma medications. In this study, we further investigated the influence of carrier characteristics on drug delivery performance. The carboxyl-terminated PNIPAAm samples with different molecular weights were synthesized by varying the molar ratio of mercaptoacetic acid (MAA)/N-isopropylacrylamide (NIPAAm) from 0.05 to 1.25, and were determined by end-group titration. The preparation of gelatin-g-PNIPAAm (GN) copolymers from these thermoresponsive polymers was achieved using carbodiimide chemistry. Our results showed that the carboxylic end-capped PNIPAAm of high molecular weight may lead to the lower thermal phase transition temperature and slower degradation rate of GN vehicles than its low molecular weight counterparts. With a decreasing MAA/NIPAAm molar ratio, the drug encapsulation efficiency of copolymers was increased due to fast temperature-triggered capture of pilocarpine nitrate. The degradation of the gelatin network could greatly affect the drug release profiles. All of the GN copolymeric carriers demonstrated good corneal endothelial cell and tissue compatibility. It is concluded that different types of GN-based delivery systems exhibit noticeably distinct intraocular pressure-lowering effect and miosis action, thereby reflecting the potential value of a MAA/NIPAAm molar ratio in the development of new antiglaucoma formulations. PMID:24187486

Biodegradable in situ gelling delivery systems containing pilocarpine as new antiglaucoma formulations: effect of a mercaptoacetic acid/N-isopropylacrylamide molar ratio.

PubMed

Lai, Jui-Yang

2013-01-01

Ocular drug delivery is one of the most commonly used treatment modalities in the management of glaucoma. We have recently proposed the use of gelatin and poly(N-isopropylacrylamide) (PNIPAAm) graft copolymers as biodegradable in situ forming delivery systems for the intracameral administration of antiglaucoma medications. In this study, we further investigated the influence of carrier characteristics on drug delivery performance. The carboxyl-terminated PNIPAAm samples with different molecular weights were synthesized by varying the molar ratio of mercaptoacetic acid (MAA)/N-isopropylacrylamide (NIPAAm) from 0.05 to 1.25, and were determined by end-group titration. The preparation of gelatin-g-PNIPAAm (GN) copolymers from these thermoresponsive polymers was achieved using carbodiimide chemistry. Our results showed that the carboxylic end-capped PNIPAAm of high molecular weight may lead to the lower thermal phase transition temperature and slower degradation rate of GN vehicles than its low molecular weight counterparts. With a decreasing MAA/NIPAAm molar ratio, the drug encapsulation efficiency of copolymers was increased due to fast temperature-triggered capture of pilocarpine nitrate. The degradation of the gelatin network could greatly affect the drug release profiles. All of the GN copolymeric carriers demonstrated good corneal endothelial cell and tissue compatibility. It is concluded that different types of GN-based delivery systems exhibit noticeably distinct intraocular pressure-lowering effect and miosis action, thereby reflecting the potential value of a MAA/NIPAAm molar ratio in the development of new antiglaucoma formulations.

Purification and Characterization of Two Major Lectins from Araucaria brasiliensis syn. Araucaria angustifolia Seeds (Pinhão) 1

PubMed Central

Datta, Pradip K.; Figueroa, Maria O. D. C. R.; Lajolo, Franco M.

1991-01-01

Two major lectins (lectin I and lectin II) were purified to homogeneity from the seeds of Araucaria brasiliensis (Gymnospermae). The purity of the lectins was confirmed by polyacrylamide gel electrophoresis, isoelectric focusing, and high performance liquid chromatography. They are glycoproteins in nature containing 6.3 and 2.9%, respectively, of neutral sugar and have absorption coefficients of 3.8 and 4.7, respectively, at 280 nanometers. The molecular weights of both lectins obtained by gel filtration on Sephacryl S-400 were equal: 200,000. After dissociation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, molecular weights were 20,000 and 34,000, respectively, for lectin I and lectin II, suggesting they are decameric and hexameric in nature. The amino acid composition of both lectins showed little difference, but both had high amounts of acidic amino acids and lacked methionine in their molecule. The carbohydrate binding specificity of lectins was directed towards mannose, glucose, and their oligomers. High inhibitory activity was also found with thyroglobulin. The erythroagglutinating activity of the lectins was enhanced in the presence of high-molecular-weight substances both at 37 and 4°C. Divalent cations do not appear to be essential for activity. They maintained their agglutinating activity over a broad but different range of pH: 5.5 to 7.5 and 6.5 to 7.5, respectively. Both lectins agglutinated erythrocytes of human ABO blood types equally well. ImagesFigure 2Figure 3 PMID:16668523

Isomer effects on polyimide properties

NASA Technical Reports Server (NTRS)

Stump, B. L.

1974-01-01

The polymerization of 2,4'-methylene-dianiline with benzophenone tetracarboxylic acid dianhydride yields high molecular weight polyamic acid. Polyimide is formed when films of the polyamic acid are cured between 200 - 300 C. A lower molecular weight polyamic acid is obtained from 2,2'-MDA with BTDA, but it appears that a lowering of the reaction temperature will yield high molecular weight polymer. Evaluation of these polymers is underway. Continued efforts to synthesize 2,3'- MDA and 2,3'-diaminobenzophenone have met with little success.

[Intensive care of children with DIC syndrome based on the use of low molecular weight heparins].

PubMed

Chuprova, A V; Shmakov, A N; Solov'ev, O N; Anokhina, T Iu; Loskutova, S A; Pinegina, Iu S

2002-01-01

The first section of this paper presents data on low-molecular-weight heparins: pharmacokinetics and pharmacodynamics, advantages in comparison with common heparin. The second section presents the results of fraxiparin and clivarin use in 43 children aged 9 months to 14 years with acute/subacute DIC syndrome of infectious origin. Therapeutic and maintenance doses, the mode of injection of low-molecular-weight heparins, and methods for laboratory monitoring of their efficiency and safety are presented.

Monitoring of occupational and environmental aeroallergens-- EAACI Position Paper. Concerted action of the EAACI IG Occupational Allergy and Aerobiology & Air Pollution.

PubMed

Raulf, M; Buters, J; Chapman, M; Cecchi, L; de Blay, F; Doekes, G; Eduard, W; Heederik, D; Jeebhay, M F; Kespohl, S; Krop, E; Moscato, G; Pala, G; Quirce, S; Sander, I; Schlünssen, V; Sigsgaard, T; Walusiak-Skorupa, J; Wiszniewska, M; Wouters, I M; Annesi-Maesano, I

2014-10-01

Exposure to high molecular weight sensitizers of biological origin is an important risk factor for the development of asthma and rhinitis. Most of the causal allergens have been defined based on their reactivity with IgE antibodies, and in many cases, the molecular structure and function of the allergens have been established. Significant information on allergen levels that cause sensitization and allergic symptoms for several major environmental and occupational allergens has been reported. Monitoring of high molecular weight allergens and allergen carrier particles is an important part of the management of allergic respiratory diseases and requires standardized allergen assessment methods for occupational and environmental (indoor and outdoor) allergen exposure. The aim of this EAACI task force was to review the essential points for monitoring environmental and occupational allergen exposure including sampling strategies and methods, processing of dust samples, allergen analysis, and quantification. The paper includes a summary of different methods for sampling and allergen quantification, as well as their pros and cons for various exposure settings. Recommendations are being made for different exposure scenarios. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Broadband terahertz dynamics of propylene glycol monomer and oligomers

NASA Astrophysics Data System (ADS)

Koda, Shota; Mori, Tatsuya; Kojima, Seiji

2016-12-01

We investigated the broadband terahertz spectra (0.1-5.0 THz) of glass-forming liquids, propylene glycol (PG), its oligomers poly (propylene glycol)s (PPGs), and poly (propylene glycol) diglycidyl ether (PPG-de) using broadband terahertz time-domain spectroscopy and low-frequency Raman scattering. The numerical value of the dielectric loss at around 1.5 THz, which is the peak position of broad peaks in all samples, decreased as the molecular weight increased. Furthermore, the peak at around 1.5 THz is insensitive to the molecular weight. For PPGs, the side chain effect of the oligomer was observed in the terahertz region. Based on the experimental and calculation results for the PPGs and PPG-de, whose end groups are epoxy groups, the beginnings of the increases in the observed dielectric loss above 3.5 THz of the PPGs are assigned to the OH bending vibration. The higher value of the dielectric loss in the terahertz region for the PPG-de can be the tail of a broad peak located in the MHz region. The difference between the Raman susceptibility and dielectric loss reflects the difference in the observable molecular dynamics between the infrared and Raman spectroscopies.

Bioavailability of riverine dissolved organic matter in three Baltic Sea estuaries and the effect of catchment land-use

NASA Astrophysics Data System (ADS)

Asmala, E.; Autio, R.; Kaartokallio, H.; Pitkänen, L.; Stedmon, C. A.; Thomas, D. N.

2013-06-01

The microbial degradation of dissolved organic carbon and nitrogen (DOC, DON) was studied in three boreal estuaries with contrasting land use patterns (Kiiminkijoki - natural forest and peatland; Kyrönjoki - agricultural; Karjaanjoki - mixed/urban). Bioassays conducted for 12-18 days were used in 3 seasons at in situ temperatures. Besides the bulk parameters, a suite of dissolved organic matter (DOM) quality parameters were investigated, including colored DOM (CDOM), fluorescent DOM and the molecular weight of DOM. Bioavailable DOC and DON pools varied significantly between the estuaries, from 7.9% in Kiiminkijoki to 10.6% in Karjaanjoki and from 5.5% in Kiiminkijoki to 21.9% in Kyrönjoki, respectively. DOM originating from catchment dominated by natural forests and peatlands had the lowest DOC and DON degradation rates, as well as the lowest proportions of biodegradable DOC and DON. A greater proportion of agricultural land in the catchment increased the bioavailability of DON, but not the bioavailability of DOC. Also DOM quality varied significantly between the estuaries, and DOM originating from the agricultural Kyrönjoki catchment sustained higher DOC and DON degradation rates and higher bacterial growth efficiency (BGE) compared to those of the natural forest and peat dominated Kiiminkijoki catchment. The quality of DOM, indicated by differences in CDOM, fluorescent DOM and molecular weight, varied between estuaries with differing land use and was concluded to be major driver of BGE of these systems and thereafter to the microbial CO2 fluxes from the estuaries. The differences in BGE resulted in a 5-fold differences in the calculated daily bacterial CO2-emissions between the study estuaries due to bacterial activity, ranging from 40 kg C d-1 in Karjaanjoki estuary to 200 kg C d-1 in Kyrönjoki estuary. Two of the study systems (Karjaanjoki, mixed land use; Kyrönjoki, intensive agriculture) in which the DOM pool had lower DOC : DON ratio, smaller molecular weight and higher CDOM absorption spectral slope values resulted in higher proportion of the initial DOC and DON being transferred to microbial growth and therefore to the pelagic food web. The pristine, peatland and forest-dominated Kiiminkijoki catchment had the lowest BGE, and therefore proportionally highest CO2 fluxes. The slope coefficient S275-295 was a good proxy of molecular weight across estuaries and seasons, and also for different diagenetic stages of DOM during biological degradation.

The Vertex Version of Weighted Wiener Number for Bicyclic Molecular Structures

PubMed Central

Gao, Wei

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

Low-molecular weight protein profiling of genetically modified maize using fast liquid chromatography electrospray ionization and time-of-flight mass spectrometry.

PubMed

Koc, Anna; Cañuelo, Ana; Garcia-Reyes, Juan F; Molina-Diaz, Antonio; Trojanowicz, Marek

2012-06-01

In this work, the use of liquid chromatography coupled to electrospray time-of-flight mass spectrometry (LC-TOFMS) has been evaluated for the profiling of relatively low-molecular weight protein species in both genetically modified (GM) and non-GM maize. The proposed approach consisted of a straightforward sample fractionation with different water and ethanol-based buffer solutions followed by separation and detection of the protein species using liquid chromatography with a small particle size (1.8 μm) C(18) column and electrospray-time-of-flight mass spectrometry detection in the positive ionization mode. The fractionation of maize reference material containing different content of transgenic material (from 0 to 5% GM) led to five different fractions (albumins, globulins, zeins, zein-like glutelins, and glutelins), all of them containing different protein species (from 2 to 52 different species in each fraction). Some relevant differences in the quantity and types of protein species were observed in the different fractions of the reference material (with different GM contents) tested, thus revealing the potential use of the proposed approach for fast protein profiling and to detect tentative GMO markers in maize. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface segregation and surface tension of polydisperse polymer melts.

PubMed

Minnikanti, Venkatachala S; Qian, Zhenyu; Archer, Lynden A

2007-04-14

The effect of polydispersity on surface segregation of a lower molecular weight polymer component in a higher molecular weight linear polymer melt host is investigated theoretically. We show that the integrated surface excess zM of a polymer component of molecular weight M satisfies a simple relation zM=2Ue(M/Mw-1)phiM, where Mw is the weight averaged molecular weight, phiM is the polymer volume fraction, and Ue is the attraction of polymer chain ends to the surface. Ue is principally of entropic origin, but also reflects any energetic preference of chain ends to the surface. We further show that the surface tension gammaM of a polydisperse melt of high molar mass components depends on the number average degree of polymerization Mn as, gammaM=gammainfinity+2UerhobRT/Mn. The parameter gammainfinity is the asymptotic surface tension of an infinitely long polymer of the same chemistry, rhob is the bulk density of the polymer, R is the universal gas constant, and T is the temperature. The predicted gammaM compare favorably with surface tension values obtained from self-consistent field theory simulations that include equation of state effects, which account for changes in polymer density with molecular weight. We also compare the predicted surface tension with available experimental data.