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1

Calculating Molecular Weight  

NSDL National Science Digital Library

This video and online calculator show how to calculate the molecular weight of a substance from the atomic weights given on the periodic table. Use the molecular weight to convert between the macroscopic scale (grams of a substance) and the microscopic scale (number of molecules of that substance).

2

Molecular Weight and Molecular Weight Distributions in Synthetic Polymers.  

ERIC Educational Resources Information Center

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…

Ward, Thomas Carl

1981-01-01

3

9 CFR 442.3 - Scale requirements for accurate weights, repairs, adjustments, and replacements after inspection.  

Code of Federal Regulations, 2011 CFR

... false Scale requirements for accurate weights, repairs, adjustments, and replacements...PROCEDURES AND REQUIREMENTS FOR ACCURATE WEIGHTS § 442.3 Scale requirements for accurate weights, repairs, adjustments, and...

2011-01-01

4

9 CFR 442.3 - Scale requirements for accurate weights, repairs, adjustments, and replacements after inspection.  

Code of Federal Regulations, 2010 CFR

... false Scale requirements for accurate weights, repairs, adjustments, and replacements...PROCEDURES AND REQUIREMENTS FOR ACCURATE WEIGHTS § 442.3 Scale requirements for accurate weights, repairs, adjustments, and...

2010-01-01

5

Apparatus for molecular weight separation  

DOEpatents

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).

Smith, Richard D. (Richland, WA); Liu, Chuanliang (Haverhill, MA)

2001-01-01

6

9 CFR 201.71 - Scales; accurate weights, repairs, adjustments or replacements after inspection.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 false Scales; accurate weights, repairs, adjustments or replacements...Services § 201.71 Scales; accurate weights, repairs, adjustments or replacements...maintained, and operated to ensure accurate weights. Such scales shall meet applicable...

2011-01-01

7

Ultrahigh molecular weight aromatic siloxane polymers  

NASA Technical Reports Server (NTRS)

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.

Ludwick, L. M.

1982-01-01

8

Microdialysis unit for molecular weight separation  

DOEpatents

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).

Smith, Richard D. (Richland, WA); Liu, Chuanliang (Richland, WA)

1999-01-01

9

High-order accurate dissipative weighted compact nonlinear schemes  

Microsoft Academic Search

Based on the method deriving dissipative compact linear schemes ( DCS), novel high-order dissipative weighted compact nonlinear\\u000a schemes (DWCNS) are developed. By Fourier analysis, the dissipative and dispersive features of DWCNS are discussed. In view\\u000a of the modified wave number, the DWCNS are equivalent to the fifth-order upwind biased explicit schemes in smooth regions\\u000a and the interpolations at cell-edges dominate

Xiaogang Deng; China Aerodynamics

2002-01-01

10

Molecular characteristics of some commercial high-molecular-weight hyaluronans.  

PubMed

Commercially available hyaluronan (HA) samples were investigated by the method of size exclusion chromatography (SEC). The fractions eluted from the SEC column were on-line molecularly characterized by using a multi-angle laser light scattering (MALLS) photometer. Along with the SEC-MALLS technique, the high-molecular-weight HA biopolymers were (off-line) analyzed by capillary viscometry. PMID:12378558

Soltés, L; Mendichi, R; Lath, D; Mach, M; Bakos, D

2002-10-01

11

Polystyrene-equivalent molecular weight versus true molecular weight in size-exclusion chromatography  

Microsoft Academic Search

The evaluation of the size-exclusion chromatography (SEC) concentration elution curves by means of a calibration dependence obtained in a given SEC set for a polymer different from the polymer to be analyzed results in an error in the determination of both molecular weight and molecular-weight distribution (MWD). The problem is analyzed assuming the validity of the universal-calibration concept. The differences

Miloš Netopil??k; Pavel Kratochv??l

2003-01-01

12

Ultrahigh Molecular Weight Aromatic Siloxane Polymers  

NASA Technical Reports Server (NTRS)

Silphenylene-siloxane polymers can be prepared by a condensation reaction of a diol 1,4-bis(hydroxydimethylsilyl)benzene and a silane bis(dimethylamino)dimethylsilane. Using a stepwise condensation technique, a polymer (R=CH3) with a molecular weight in excess of 1.0 x 1 million has been produced. The polymer exhibits increased thermal stability, compared to a methyl siloxane polymer without the aromatic phenyl ring in the backbone. The use of bis(dimethylamino)methylvinylsilane should allow for ready crosslinking at the vinyl sites (R=-CH=CH2) introduced into the backbone. However, under the conditions of the reaction system a high molecular weight polymer was not obtained or the polymer underwent a crosslinking process during the synthesis.

Ludwick, L. M.

1983-01-01

13

Developments toward more accurate molecular modeling of liquids  

NASA Astrophysics Data System (ADS)

The general goal of this research has been to improve upon existing combined quantum mechanics/molecular mechanics (QM/MM) methodologies. Error weighting functions have been introduced into the perturbative Monte Carlo (PMC) method for use with QM/MM. The PMC approach, introduced earlier, provides a means to reduce the number of full self-consistent field (SCF) calculations in simulations using the QM/MM potential by evoking perturbation theory to calculate energy changes due to displacements of a MM molecule. This will allow the ab initio QM/MM approach to be applied to systems that require more advanced, computationally demanding treatments of the QM and/or MM regions. Efforts have also been made to improve the accuracy of the representation of the solvent molecules usually represented by MM force fields. Results from an investigation of the applicability of the embedded density functional theory (EDFT) for studying physical properties of solutions will be presented. In this approach, the solute wavefunction is solved self- consistently in the field of individually frozen electron-density solvent molecules. To test its accuracy, the potential curves for interactions between Li+, Cl- and H2O with a single frozen-density H 2O molecule in different orientations have been calculated. With the development of the more sophisticated effective fragment potential (EFP) representation of solvent molecules, a QM/EFP technique was created. This hybrid QM/EFP approach was used to investigate the solvation of Li + by small clusters of water, as a test case for larger ionic dusters. The EFP appears to provide an accurate representation of the strong interactions that exist between Li+ and H2O. With the QM/EFP methodology comes an increased computational expense, resulting in an even greater need to rely on the PMC approach. However, while including the PMC into the hybrid QM/EFP technique, it was discovered that the previous implementation of the PMC was done incorrectly, invalidating earlier test results. The PMC implementation was therefore reworked, and tests were performed to investigate the methods usefulness in reducing the computational load of these types of simulations. The results that were obtained while studying F-(H2O) and F-(H 2O)2 show that PMC can be used cautiously to increase computational efficiency.

Evans, Tom J.

2000-12-01

14

Developments toward more accurate molecular modeling of liquids  

Microsoft Academic Search

The general goal of this research has been to improve upon existing combined quantum mechanics\\/molecular mechanics (QM\\/MM) methodologies. Error weighting functions have been introduced into the perturbative Monte Carlo (PMC) method for use with QM\\/MM. The PMC approach, introduced earlier, provides a means to reduce the number of full self-consistent field (SCF) calculations in simulations using the QM\\/MM potential by

Tom J. Evans

2000-01-01

15

Molecular weight of aquatic fulvic acids by vapor pressure osmometry  

Microsoft Academic Search

The molecular weights of aquatic fulvic acids extracted from five rivers were determined by vapor pressure osmometry with water and tetrahydrofuran as solvents. The values obtained ranged form 500 to 950 daltons, indicating that the molecular weights of aquatic fulvic acids are not as great as has been suggested in some other molecular weight studies. The samples were shown to

G. R. Aiken; R. L. Malcolm

1987-01-01

16

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

17

Towards Accurate Molecular Modeling of Plastic Bonded Explosives  

NASA Astrophysics Data System (ADS)

There is substantial interest in identifying the controlling factors that influence the susceptibility of polymer bonded explosives (PBXs) to accidental initiation. Numerous Molecular Dynamics (MD) simulations of PBXs using the COMPASS force field have been reported in recent years, where the validity of the force field in modeling the solid EM fill has been judged solely on its ability to reproduce lattice parameters, which is an insufficient metric. Performance of the COMPASS force field in modeling EMs and the polymeric binder has been assessed by calculating structural, thermal, and mechanical properties, where only fair agreement with experimental data is obtained. We performed MD simulations using the COMPASS force field for the polymer binder hydroxyl-terminated polybutadiene and five EMs: cyclotrimethylenetrinitramine, 1,3,5,7-tetranitro-1,3,5,7-tetra-azacyclo-octane, 2,4,6,8,10,12-hexantirohexaazazisowurzitane, 2,4,6-trinitro-1,3,5-benzenetriamine, and pentaerythritol tetranitate. Predicted EM crystallographic and molecular structural parameters, as well as calculated properties for the binder will be compared with experimental results for different simulation conditions. We also present novel simulation protocols, which improve agreement between experimental and computation results thus leading to the accurate modeling of PBXs.

Chantawansri, T. L.; Andzelm, J.; Taylor, D.; Byrd, E.; Rice, B.

2010-03-01

18

Molecular weight and antitumour activity of Zymomonas mobilis levans  

Microsoft Academic Search

Levans produced by several Zymomonas mobilis strains were classified by their viscosity average molecular weight and tested against sarcoma 180. Measurements of the samples’ polydispersity were carried out to characterise the molecular weight distribution. The antitumour activities of levan samples were plotted against the viscosity average molecular weight and a maximum value of this activity was found at Mv=210?000 (Mw=456?900

Gl??cia M. T Calazans; Rosália C Lima; Francisca P de França; Carlos Edison Lopes

2000-01-01

19

Low Molecular Weight Heparin-Induced Liver Toxicity  

Microsoft Academic Search

The authors report two cases of hepatotoxicity induced by low molecular weight heparin. A 26-year-old woman and a 33-year-old man were treated with low molecular weight heparin for pulmonary embolism and cerebral infarction, respectively. They both developed derangement in liver function tests a few days after commencement of the low molecular weight heparin. The derangement in liver function tests was

Chee-Kin Hui; Man-Fung Yuen; Irene Oi-Lin Ng; Kenneth Wah-Tak Tsang; Gardian Chung-Yan Fong; Ching-Lung Lai

2001-01-01

20

Molecular Weight Effects on the Viscoelastic Response of a Polyimide  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

21

Conversions of low molecular weight hydrocarbons to higher molecular weight hydrocarbons using a metal compound-containing catalyst  

SciTech Connect

A process for the production of higher molecular weight hydrocarbons from lower molecular hydrocarbons is described comprising the steps of: (a) introducing into a reaction zone a lower molecular weight hydrocarbon-containing gas and contacting the gas in the zone with a metal compound-containing catalyst containing a carbide, nitride, boride or oxide of thorium under C/sub 2//sup +/ hydrocarbon synthesis conditions such that at least 15 mole percent of the lower molecular weight hydrocarbons in the gas are converted to higher molecular weight hydrocarbons, the conditions including a temperature of greater than 1000/sup 0/C and a gas hourly space velocity of greater than 6000 hr/sup -1/; (b) withdrawing from the reaction zone a higher molecular weight hydrocarbon-containing stream.

Devries, L.; Ryason, P.R.

1988-03-29

22

Conversions of low molecular weight hydrocarbons to higher molecular weight hydrocarbons using a metal compound-containing catalyst  

SciTech Connect

A process is described for the production of higher molecular weight hydrocarbons from lower molecular hydrocarbons comprising the steps of: (a) introducing into a reaction zone a lower molecular weight hydrocarbon-containing gas and contacting the gas in the zone with a metal compound-containing catalyst having a surface area in the range 0.1 to 10 m/sup 2//gram and containing a carbide, nitride, boride or oxide of a Group I-A metal, under C/sub 2/ + hydrocarbon synthesis conditions such that at least 15 mole percent of the lower molecular weight hydrocarbons in the gas are converted to higher molecular weight hydrocarbons, the conditions including a temperature of greater than 1000/sup 0/C and a gas hourly space velocity of greater than 3200 hr/sup -1/; (b) withdrawing from the reaction zone a higher molecular weight hydrocarbon-containing stream.

Devries, L.; Ryason, P.R.

1987-11-24

23

Molecular weight of aquatic fulvic acids by vapor pressure osmometry  

USGS Publications Warehouse

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

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

1987-01-01

24

Molecular weight of aquatic fulvic acids by vapor pressure osmometry  

SciTech Connect

The molecular weights of aquatic fulvic acids extracted from five rivers were determined by vapor pressure osmometry with water and tetrahydrofuran as solvents. The values obtained ranged form 500 to 950 daltons, indicating that the molecular weights of aquatic fulvic acids are not as great as has been suggested in some other molecular weight studies. The samples were shown to be relatively monodisperse from radii of gyration measurements determined by small angle x-ray scattering. THF affords greater precision and accuracy than H/sub 2/O in VPO measurements, and was found to be a suitable solvent for the determination of molecular weight of aquatic fulvic acid because it obviates the dissociation problem. An inverse correlation was observed with these samples between the concentration of Ca/sup + +/ and Mg/sup + +/ in the river water and the radii of gyration and molecular weights of the corresponding fulvic acid samples.

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

1987-08-01

25

Evaluation of ultrafiltration for determining molecular weight of fulvic acid  

USGS Publications Warehouse

Two commonly used ultrafiltration membranes are evaluated for the determination of molecular weights of humic substances. Polyacrylic acids of Mr 2000 and 5000 and two well-characterized fulvic acids are used as standards. Molecular size characteristics of standards, as determined by small-angle X-ray scattering, are presented. Great care in evaluating molecular weight data obtained by ultrafiltration is needed because of broad nominal cutoffs and membrane-solute interactions.

Aiken, G.R.

1984-01-01

26

Low molecular weight species in humic and fulvic fractions  

USGS Publications Warehouse

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.

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

1988-01-01

27

Low molecular weight species in humic and fulvic fractions  

SciTech Connect

Fourier transform solution /sup 1/H 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, the authors report that some of these materials are not contaminants since /sup 1/H-NMR can be used to follow their formation from higher molecular weight species.

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

1988-01-01

28

Optimization of parameters for coverage of low molecular weight proteins  

E-print Network

Proteins with molecular weights of <25 kDa are involved in major biological processes such as ribosome formation, stress adaption (e.g., temperature reduction) and cell cycle control. Despite their importance, the coverage ...

Muller, Stephan A.

29

Trends and inferred emissions of atmospheric high molecular weight perfluorocarbons  

E-print Network

Atmospheric observations and atmospheric observation-based global emission estimates are presented for the five high molecular weight perfluorocarbons (PFCs): decafluorobutane (C 4 F 1 0 ), dodecafluoropentane (C5 F1 2 ), ...

Ivy, Diane Jean

2012-01-01

30

Low molecular weight heparin in prevention of perioperative thrombosis  

Microsoft Academic Search

OBJECTIVE--To determine whether prophylactic treatment with low molecular weight heparin reduces the incidence of thrombosis in patients who have had general or orthopaedic surgery. DESIGN--Meta-analysis of results from 52 randomised, controlled clinical studies (29 in general surgery and 23 in orthopaedic surgery) in which low molecular weight heparin was compared with placebo, dextran, or unfractionated heparin. SUBJECTS--Patients who had had

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

1992-01-01

31

Molecular weight induced peak doubling in liquid chromatography  

E-print Network

MOLECULAR WEIGHT INDUCED PEAK DOUBLING IN LIQUID CHROMATOGRAPHY A Thesis by JOHN MEBANE FICKLING, JR. Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... May 1980 Ma)or Subject: Chemistry MOLECULAR WEIGHT INDUCED PEAK DOUBLING IN LIQUID CHROMATOGRAPHY A Thesis by JOHN MEBANE PICKLING, JR. Approved as to style and content by: (Chairman of Committee) (Head of Department) (Member) (Member) (Mem...

Fickling, John Mebane

2012-06-07

32

Identification of the High Molecular Weight Isoform of Phostensin  

PubMed Central

Phostensin is encoded by KIAA1949. 5?-RACEanalysis has been used to identify the translation start site of phostensin mRNA, indicating that it encodes 165 amino acids with an apparent molecular weight of 26 kDa on SDS-PAGE. This low-molecular-weight phostensin is present in human peripheral blood mononuclear cells and many leukemic cell lines. Phostensin is a protein phosphatase-1(PP1) binding protein. It also contains one actin-binding motif at its C-terminal region and binds to the pointed ends of actin filaments, modulating actin dynamics. In the current study, a high-molecular-weight phostensin is identified by using immunoprecipitationin combination with a proteomic approach. This new species of phostensin is also encoded by KIAA1949 and consists of 613 amino acids with an apparent molecular weight of 110 kDa on SDS-PAGE. The low-molecular-weight and high-molecular-weight phostensins were named as phostensin-? and phostensin-?, respectively. Although phostensin-? is the C-terminal region of phostensin-?, it is not degraded from phostensin-?. Phostensin-? is capable of associating with PP1 and actin filaments, and is present in many cell lines. PMID:24434620

Lin, Yu-Shan; Huang, Hsien-Lu; Liu, Wei-Ting; Lin, Ta-Hsien; Huang, Hsien-Bin

2014-01-01

33

Evaluation of a Viscosity-Molecular Weight Relationship.  

ERIC Educational Resources Information Center

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…

Mathias, Lon J.

1983-01-01

34

A Weight-Averaged Interpolation Method for Coupling Time-Accurate Rarefied and Continuum Flows  

NASA Astrophysics Data System (ADS)

A novel approach to coupling rarefied and continuum flow regimes as a single, hybrid model is introduced. The method borrows from techniques used in the simulation of spray flows to interpolate Lagrangian point-particles onto an Eulerian grid in a weight-averaged sense. A brief overview of traditional methods for modeling both rarefied and continuum domains is given, and a review of the literature regarding rarefied/continuum flow coupling is presented. Details of the theoretical development of the method of weighted interpolation are then described. The method evaluates macroscopic properties at the nodes of a CFD grid via the weighted interpolation of all simulated molecules in a set surrounding the node. The weight factor applied to each simulated molecule is the inverse of the linear distance between it and the given node. During development, the method was applied to several preliminary cases, including supersonic flow over an airfoil, subsonic flow over tandem airfoils, and supersonic flow over a backward facing step; all at low Knudsen numbers. The main thrust of the research centered on the time-accurate expansion of a rocket plume into a near-vacuum. The method proves flexible enough to be used with various flow solvers, demonstrated by the use of Fluent as the continuum solver for the preliminary cases and a NASA-developed Large Eddy Simulation research code, WRLES, for the full lunar model. The method is applicable to a wide range of Mach numbers and is completely grid independent, allowing the rarefied and continuum solvers to be optimized for their respective domains without consideration of the other. The work presented demonstrates the validity, and flexibility of the method of weighted interpolation as a novel concept in the field of hybrid flow coupling. The method marks a significant divergence from current practices in the coupling of rarefied and continuum flow domains and offers a kernel on which to base an ongoing field of research. It has the potential to significantly increase the flexibility of hybrid rarefied/continuum flow analyses.

Diaz, Steven William

35

Towards Accurate Molecular Modeling of Plastic Bonded Explosives  

Microsoft Academic Search

There is substantial interest in identifying the controlling factors that influence the susceptibility of polymer bonded explosives (PBXs) to accidental initiation. Numerous Molecular Dynamics (MD) simulations of PBXs using the COMPASS force field have been reported in recent years, where the validity of the force field in modeling the solid EM fill has been judged solely on its ability to

T. L. Chantawansri; J. Andzelm; D. Taylor; E. Byrd; B. Rice

2010-01-01

36

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

PubMed Central

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 ?–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

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

2014-01-01

37

Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances  

USGS Publications Warehouse

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.

Chin, Y.-P.; Aiken, G.; O'Loughlin, E.

1994-01-01

38

Novel Technique for Measuring Low Molecular Weight Chemicals in Indoor Dust  

Microsoft Academic Search

A new technique is described which can measure low molecular weight compounds adsorbed onto dust parti cles in a simple yet accurate way. The technique, gas chromatography-ultraviolet spectrometry (GC-UV), com prises a one-stage thermal desorption oven, a gas flow cell with a miniaturised GC column, and a nitrogen- flushed photo diode array (PDA) detector for fast UV spectra recording. The

Anders Nilsson; Ali Reza Nosratabadi; Verner Lagesson; Nicola Murgia; Per Leanderson; Christer Tagesson

2002-01-01

39

Molecular weight dependent bimolecular recombination in organic solar cells  

NASA Astrophysics Data System (ADS)

Charge carrier recombination is studied in operational organic solar cells made from the polymer:fullerene system PCDTBT:PC71BM (poly[N-9''-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]: [6,6]-phenyl-C70-butyric acid methyl ester). A newly developed technique High Intensity Resistance dependent PhotoVoltage is presented for reliably quantifying the bimolecular recombination coefficient independently of variations in experimental conditions, thereby resolving key limitations of previous experimental approaches. Experiments are performed on solar cells of varying thicknesses and varying polymeric molecular weights. It is shown that solar cells made from low molecular weight PCDTBT exhibit Langevin recombination, whereas suppressed (non-Langevin) recombination is found in solar cells made with high molecular weight PCDTBT.

Philippa, Bronson; Stolterfoht, Martin; White, Ronald D.; Velusamy, Marrapan; Burn, Paul L.; Meredith, Paul; Pivrikas, Almantas

2014-08-01

40

RHEOLOGICAL PROPERTIES & MOLECULAR WEIGHT DISTRIBUTIONS OF FOUR PERFLUORINATED THERMOPLASTIC POLYMERS  

SciTech Connect

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

Hoffman, D M; Shields, A L

2009-02-24

41

Mean molecular weight and hydrogen abundance of Titan's atmosphere  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

42

Polyelectrolyte Charge Corrected Molecular Weight and Effective Charge by Sedimentation  

PubMed Central

Ionic charge on a macromolecule complicates the determination of its molecular weight in solution due to the Donnan effect. Compensation for it can be made if one knows the value of the effective charge, which can be found by dialysis equilibrium across a semipermeable membrane. A moving boundary of molecules sedimenting in a centrifugal field can act as a membrane, obviating some of the disadvantages (such as selective adsorption) of a real membrane. Interference optics are used to monitor the reverse gradient of the salt due to the Donnan effect, hence facilitating the determination of the effective charge. The apparent molecular weight obtained from a conventional sedimentation equilibrium can then be corrected to yield the true molecular weight. The effective charge is valuable in revealing macromolecular structural features when related to the titratable charge through the Manning counter-ion condensation theory. Agreement between the values of the backbone molecular weights for the Na, Cs, and Ca salts of heparin indicated the validity of the approach. The effective charge ratio and the axial charge spacing for the Na and Ca heparin agreed with the literature, whereas the results for Cs indicated a degree of binding in excess of that due to counter-ion condensation. PMID:19431694

Braswell, Emory H.

1987-01-01

43

Molecular Weight Dependence of Polymersome Membrane Structure, Elasticity, and Stability  

E-print Network

permeation chromatography with polystyrene standards was used to determine number-average molecular weights by evaporation of the chloroform under vacuum. Addition of sucrose solution (250- 300 mM), to give a final with temperature and humidity control. The sample assembly was rapidly vitrified with liquid ethane at its melting

44

Preparation of soybean oil polymers with high molecular weight  

Technology Transfer Automated Retrieval System (TEKTRAN)

The cationic polymerization of soybean oils was initiated by boron trifluoride diethyl etherate BF3.O(C2H5)2 in supercritical carbon dioxide (scCO2) medium. The resulting polymers had molecular weight ranging from 21,842 to 118,300 g/mol. Nuclear magnetic resonance spectroscopy (NMR) and gel perme...

45

Ultra-High-Molecular-Weight Silphenylene/Siloxane Polymers  

NASA Technical Reports Server (NTRS)

Elastomers having molecular weights above 1 million made by twostage polymerization. Two-stage process proves far more successful than synthesis from reactive monomers. Process involves synthesis of silanolterminated prepolymer and subsequent extension of prepolymer chain with additional aminosilane monomer. Multistage method allows chain-extending monomer added in precise amounts between stages.

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

1986-01-01

46

The influence of molecular weight on plasticizer retention  

E-print Network

, migration and extraction under some ser- vice conditions. Plasticizers used in PVC is volatile loss- branes can be factory-fab- ricated into large panels. Over time, plasticizers can migrate from PYCThe influence of molecular weight on plasticizer retention A key change to specification PGI-ll 04

47

Low Molecular Weight Protamine: A Potential Nontoxic Heparin Antagonist  

Microsoft Academic Search

ened low molecular weight protamine fragment containing the heparin-neutralizing domain could Protamine sulfate is the universal clinical antago- be derived directly from a native protamine, it nist to heparin and is used routinely after cardio- could be a potent and nontoxic heparin antagonist. vascular surgery to neutralize the anticoagulant In this article, we present our experimental re- function of heparin.

Youngro Byun; Vijendra K. Singh; Victor C. Yang

48

A Less Toxic Heparin Antagonist—Low Molecular Weight Protamine  

Microsoft Academic Search

A new thirteen amino acid peptide, named low molecular weight protamine (LMWP), was obtained through the enzymatic digestion of native protamine. Both in vitro and in vivo results showed that LMWP fully maintained the heparin neutralization function of protamine but had much lower immunogenicity and antigenicity. Unlike protamine, neither LMWP nor LMWP\\/heparin complexes caused significant blood platelet aggregation in rats.

J. F. Liang; L. Zhen; L.-C. Chang; V. C. Yang

2003-01-01

49

Study on antimicrobial activity of chitosan with different molecular weights  

Microsoft Academic Search

E. coli and Staphylococcus aureus are used to study the antimicrobial activity of chitosan of different molecular weights (MW). The effect of the concentration and MW of chitosan were investigated, respectively, and the antimicrobial mechanism was discussed. For chitosan with MW below 300 kDa, the antimicrobial effect on S. aureus was strengthened as the MW increased. In contrast, the effect

Lian-Ying Zheng; Jiang-Feng Zhu

2003-01-01

50

Preclinical studies on a low molecular weight heparin  

Microsoft Academic Search

Some major developments in the area of antithrombotic therapy have occurred during the past decade. Of these, the concept of fractionation of heparin has resulted in the development of several products from this agent. The introduction of low molecular weight heparins (LMWHs) has added a new chapter to the prophylactic and therapeutic management of thromboembolic disorders. These agents are now

Jawed Fareed; Walter Jeske; Volker Eschenfelder; Orner Iqbal; Debra Hoppensteadt; Ahmad Ahsan

1996-01-01

51

Discrepancies between Micellar Molecular Weights by Number-Average and Weight-Average Methods  

Microsoft Academic Search

IN recent years, light-scattering techniques have been widely used for the determination of micellar molecular weights. On the other hand, a few workers1-3 have chosen to make such determinations through measurement of colligative properties, in particular, by measurement of the lowering of the vapour pressure.

Paul Becher

1965-01-01

52

Molecular weight dependence of domain structure in silica-siloxane molecular composites  

SciTech Connect

A detailed investigation of the molecular weight dependence of silica growth in in situ filled polydimethylsiloxane/tetraethylorthosilicate (PDMS/TEOS) materials was conducted using small angle neutron scattering (SANS). Composite materials were produced by using TEOS to simultaneously produce the glassy filler phase and to crosslink linear, hydroxyl terminated PDMS of variable molecular weight, M. Correlated domains of glassy filler were produced. The morphology of the in situ filled material showed a definite dependence on the molecular weight of the precursor polymer. The scale, R, of the glassy domains follows de Gennes` description of phase separation in a crosslinked system (R {alpha} M{sup 1/2}).

Ulibarri, T.A.; Beaucage, G.; Schaefer, D.W.; Olivier, B.J.; Assink, R.A.

1992-07-01

53

Molecular weight dependence of domain structure in silica-siloxane molecular composites  

SciTech Connect

A detailed investigation of the molecular weight dependence of silica growth in in situ filled polydimethylsiloxane/tetraethylorthosilicate (PDMS/TEOS) materials was conducted using small angle neutron scattering (SANS). Composite materials were produced by using TEOS to simultaneously produce the glassy filler phase and to crosslink linear, hydroxyl terminated PDMS of variable molecular weight, M. Correlated domains of glassy filler were produced. The morphology of the in situ filled material showed a definite dependence on the molecular weight of the precursor polymer. The scale, R, of the glassy domains follows de Gennes' description of phase separation in a crosslinked system (R {alpha} M{sup 1/2}).

Ulibarri, T.A.; Beaucage, G.; Schaefer, D.W.; Olivier, B.J.; Assink, R.A.

1992-01-01

54

Employing MALDI-MS on Poly(alkylthiophenes): Analysis of Molecular Weights, Molecular Weight Distributions, End-Group Structures, and  

E-print Network

volume of the randomly coiled polymer chains with polymer molecular weight. Conjugated polymer systems subject to end-group fragmentation when the MALDI laser power was high. Larger polymer chains, however/or telechelic poly(3-alkylthiophenes). Another important issue that needs to be closely examined for PAT systems

McCullough, Richard D.

55

Folding Molecular Dynamics Simulations Accurately Predict the Effect of Mutations on the Stability and Structure of a Vammin-  

E-print Network

Folding Molecular Dynamics Simulations Accurately Predict the Effect of Mutations on the Stability Supporting Information ABSTRACT: Folding molecular dynamics simulations amounting to a grand total of 4 system, force field, and simulation protocol, folding molecular dynamics simulations appear

Glykos, Nikolaos

56

Structural determinants in a library of low molecular weight gelators.  

PubMed

Low molecular weight hydrogels are formed by molecules that form a matrix that immobilises water to form a self-supporting gel. Such gels have uses as biomaterials such as molecular scaffolds and structures for tissue engineering. One class of low molecular weight gelator (LMWG), naphthalene-conjugated dipeptides, has been shown to form hydrogels via self-assembly following a controlled drop in pH. A library of naphthalene-dipeptides has been generated previously although the relationship between the precursor sequence and the resulting self-assembled structures remained unclear. Here, we have investigated the structural details of a set of dipeptide sequences containing alanine (A) and valine (V) conjugated to naphthalene groups substituted with a Br, CN or H at the 6-position. Electron microscopy, circular dichroism and X-ray fibre diffraction shows that these LMWG may be structurally classified by their composition: the molecular packing is determined by the class of conjugate, whilst the chirality of the self-assemblies can be attributed to the dipeptide sequence. This provides insights into the relationship between the precursor sequence and the macromolecular and molecular structures of the fibres that make up the resulting hydrogels. PMID:25562785

Morris, Kyle L; Chen, Lin; Rodger, Alison; Adams, Dave J; Serpell, Louise C

2015-01-28

57

Recent Developments in Low Molecular Weight Complement Inhibitors  

PubMed Central

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

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

2009-01-01

58

High molecular weight polysaccharide that binds and inhibits virus  

SciTech Connect

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

Konowalchuk, Thomas W

2014-01-14

59

Low-Molecular-Weight Protein Tyrosine Phosphatases of Bacillus subtilis  

Microsoft Academic Search

In gram-negative organisms, enzymes belonging to the low-molecular-weight protein tyrosine phosphatase (LMPTP) family are involved in the regulation of important physiological functions, including stress resistance and synthesis of the polysaccharide capsule. LMPTPs have been identified also in gram-positive bacteria, but their functions in these organisms are presently unknown. We cloned two putative LMPTPs from Bacillus subtilis, YfkJ and YwlE, which

Lucia Musumeci; Cristina Bongiorni; Lutz Tautz; Robert A. Edwards; Andrei Osterman; Marta Perego; Tomas Mustelin; Nunzio Bottini

2005-01-01

60

Inhibition of HIV1 infectivity by low molecular weight heparin  

Microsoft Academic Search

Several sulfated polysaccharides have been shown to have anti-HIV activity in vitro. However, many of these compounds are\\u000a not suited for use in vivo because they present an increased risk of bleeding or cannot be administered chronically. We tested\\u000a the anti-HIV effects of low molecular weight heparin (LMW-heparin) (Enoxaparin) in vitro using a model system of HIV infectivity\\u000a because LMW-heparin

A. L. Howell; T. H. Taylor; J. D. Miller; D. S. Groveman; E. H. Eccles; L. R. Zacharski

1996-01-01

61

Ultra-High-Molecular-Weight Silphenylene/Siloxane Elastomers  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

62

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

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

63

Fetal pulmonary immunoreactive adrenocorticotropin: molecular weight and cellular localization.  

PubMed

The hypothalamus-pituitary-adrenal axis of the sheep fetus plays a critical role in fetal development, responsiveness to stress, and initiation of parturition. We have recently reported that the fetal lung contains and secretes significant amounts of immunoreactive adrenocorticotropin (iACTH). The present study was designed to identify the molecular weight profile and the cellular location of iACTH in this tissue. iACTH extracted from fetal lung was immunoprecipitated, electrophoresed, and immunoblotted. Pulmonary iACTH was found in several molecular forms. The largest peptides appeared as doublets, and had molecular weights similar to POMC (32, 33 kD). Smaller peptides appeared in molecular weights (17, 24, and 27 kD) which were not consistent with the post-translational processing of POMC in fetal pituitary, but which were consistent with known processing of POMC by chromaffin granule aspartyl protease. None of the molecular forms of iACTH were glycosylated. Immunohistochemistry revealed that the iACTH was contained within bronchial epithelium and within groups of cells within the parenchyma of the lung. Both of these types of cells are consistent with pulmonary neuroendocrine cells. The distribution of neuroendocrine cells and apparent concordance with the iACTH-positive cells was confirmed by immunostaining for neuron specific enolase, a marker for neuroendocrine cells within the lung. We conclude that the lung contains unprocessed and partially processed POMC within cells known to contain neuropeptides. We speculate that secretion of the POMC-related peptides from these cells is physiologically important in the late-gestation fetus. PMID:9556082

Wood, C E; Barkoe, D; The, A; Newman, H; Cudd, T A; Purinton, S; Castro, M I

1998-02-27

64

Low molecular weight protamine (LMWP) as nontoxic heparin\\/low molecular weight heparin antidote (I): Preparation and characterization  

Microsoft Academic Search

Low molecular weight protamine (LMWP) appears to be a promising solution for heparin neutralization without the protamine-associated\\u000a catastrophic toxic effects. The feasibility of this hypothesis was proven previously by using a peptide mixture produced from\\u000a proteolytic digestion of protamine. To further examine the utility of this compound as an ultimate nontoxic protamine substitute,\\u000a detailed studies on the purification and characterization

Li-Chien Chang; Hsiao-Feng Lee; ZhiQiang Yang; Victor C. Yang

2001-01-01

65

Effects of denaturants and osmolytes on proteins are accurately predicted by the molecular transfer model  

E-print Network

Effects of denaturants and osmolytes on proteins are accurately predicted by the molecular transfer between denaturants and proteins are commonly used to probe the structures of the denatured state ensemble simulations in the absence of denaturants or osmolytes, and Tanford's transfer model to predict the dependence

Thirumalai, Devarajan

66

Impact resistance and fractography in ultra high molecular weight polyethylenes.  

PubMed

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. PMID:24275347

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

2014-02-01

67

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

Code of Federal Regulations, 2010 CFR

... Polyethylene glycol (mean molecular weight 200-9,500). 178.3750 Section... Polyethylene glycol (mean molecular weight 200-9,500). Polyethylene glycol...oxide and water with a mean molecular weight of 200 to 9,500. (b) It...

2010-04-01

68

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

Code of Federal Regulations, 2011 CFR

... Polyethylene glycol (mean molecular weight 200-9,500). 178.3750 Section... Polyethylene glycol (mean molecular weight 200-9,500). Polyethylene glycol...oxide and water with a mean molecular weight of 200 to 9,500. (b) It...

2011-04-01

69

Molecular Weight Determinations of Proteins by Californium Plasma Desorption Mass Spectrometry  

Microsoft Academic Search

The plasma desorption mass spectrometry method is used to determine the molecular weights of larger molecules than before, to determine the molecular weights of proteins and peptides in mixtures, and to monitor protein modification reactions. Proteins up to molecular weight 25,000 can now be studied with a mass spectrometric technique. Protein-peptide mixtures that could not be resolved with conventional techniques

B. Sundqvist; Peter Roepstorff; J. Fohlman; A. Hedin; P. Hakansson; I. Kamensky; M. Lindberg; M. Salehpour; G. Saewe

1984-01-01

70

Fluorescence spectroscopy and molecular weight distribution of extracellular polymers from full-scale activated sludge biomass  

Microsoft Academic Search

Two fractions of extracellular polymer substances (EPSs), soluble and readily extractable (RE), were characterised in terms of their molecular weight distributions (MWD) and 3-D excitation-emission- matrix (EEM) fluorescence spectroscopy signatures. The EPS fractions were different: the soluble EPSs were composed mainly of high molecular weight compounds, while the RE EPSs were composed of small molecular weight compounds. Contrary to previous

M. Esparza-Soto; P. K. Westerhoff

2001-01-01

71

Accurate Estimation of ICA Weight Matrix by Implicit Constraint Imposition Using Lie Group  

Microsoft Academic Search

This paper presents a new stochastic algorithm to optimize the independence criterion-mutual information-among multivariate data using local, global, and hybrid optimizers, in conjunction with techniques involving a Lie group and its corresponding Lie algebra, for implicit imposition of the orthonormality constraint among the estimated sources. The major advantage of the proposed algorithm is the increased accuracy with which the weight

S. Easter Selvan; Alexandru Mustatea; C. Cecil Xavier; Jean Sequeira

2009-01-01

72

Weighted depth compensation algorithm for fluorescence molecular tomography reconstruction.  

PubMed

In fluorescence molecular tomography (FMT), diffuse-light measurements are obtained from a series of source-detector pairs placed on the boundary of the medium. The sensitivity of measurements deteriorates quickly with increased distance from the sources and detectors and therefore yields poor depth quantitative recovery. A depth compensation algorithm is presented in this paper to reconstruct fluorescent inclusions in deep tissues. Two weight matrixes are employed to level off sensitivity differences and enhance prominent elements of the solution. Results of numerical and phantom experiments demonstrate that both relative quantitation and spatial resolution of FMT are improved for inclusions at different depths. PMID:23262629

Liu, Fei; Li, Mingze; Zhang, Bin; Luo, Jianwen; Bai, Jing

2012-12-20

73

Conversions of low molecular weight hydrocarbons to higher molecular weight hydrocarbons using a metal compound-containing catalyst (II-A)  

SciTech Connect

A process for the production of higher molecular weight hydrocarbons from lower molecular hydrocarbon is described comprising the steps of: (a) introducing into a reaction zone a lower molecular weight hydrocarbon-containing gas and contacting the gas in the zone with a metal compound-containing catalyst containing a carbide, nitride, boride or oxide of a Group II-A metal, under C/sub 2/+ hydrocarbon synthesis conditions such that at least 15 mole percent of the lower molecular weight hydrocarbons in the gas are converted to higher molecular weight hydrocarbons. The conditions include a temperature of greater than 1000/sup 0/C and a gas hourly spaced velocity of greater than 6000 hr/sup -1/; (b) withdrawing from the reaction zone a higher molecular weight hydrocarbon-containing stream.

Devries, L.; Ryason, P.R.

1987-11-03

74

Conversions of low molecular weight hydrocarbons to higher molecular weight hydrocarbons using a metal compound-containing catalyst (IV-B)  

SciTech Connect

A process for the production of higher molecular weight hydrocarbons from lower molecular hydrocarbons is described comprising the steps of: (a) introducing into a reaction zone a lower molecular weight hydrocarbon-containing gas and contacting the gas in the zone with a metal compound-containing catalyst containing a carbide, nitride, boride or oxide of a Group IV-B metal, under C/sub 2/+ hydrocarbon synthesis conditions such that at least 15 mole percent of the lower molecular weight hydrocarbons in the gas are converted to higher molecular weight hydrocarbons. The conditions include temperature of greater than 1000/sup 0/C and a gas hourly space velocity of greater than 6000 hr/sup -1/; (b) withdrawing from the reaction zone a higher molecular weight hydrocarbon-containing stream.

Devries, L.; Ryason, P.R.

1987-11-03

75

Conversions of low molecular weight hydrocarbons to higher molecular weight hydrocarbons using a metal compound-containing catalyst (III-A)  

SciTech Connect

A process for the production of higher molecular weight hydrocarbons from lower molecular hydrocarbons is described comprising the steps of: (a) introducing into a reaction zone a lower molecular weight hydrocarbon-containing gas and contacting the gas in the zone with a metal compound-containing catalyst containing a carbide, nitride, boride or oxide of a Group III-A metal, under C/sub 2/+ hydrocarbon synthesis conditions such that at least 15 mole percent of the lower molecular weight hydrocarbons in the gas are converted to higher molecular weight hydrocarbons. The conditions include a temperature of greater than 1000/sup 0/C and a gas hourly space velocity of greater than 6000 hr/sup -1/; (b) withdrawing from the reaction zone a higher molecular weight hydrocarbon-containing stream.

Devries, L.; Ryason, P.R.

1987-11-03

76

Accurate Parental Classification of Overweight Adolescents' Weight Status: Does It Matter?  

Microsoft Academic Search

OBJECTIVE.Our goal was to explore whether parents of overweight adolescents who recognize that their children are overweight engage in behaviors that are likely to help their adolescents with long-term weight management. METHODS.The study population included overweight adolescents (BMI 85th percen- tile) who participated in Project EAT (Eating Among Teens) I (1999) and II (2004) and their parents who were interviewed

Dianne Neumark-Sztainer; Melanie Wall; Patricia van den Berg

2010-01-01

77

Determination of molecular weight distributions in native and pretreated wood.  

PubMed

The analysis of native wood components by size-exclusion chromatography (SEC) is challenging. Isolation, derivatization and solubilization of wood polymers is required prior to the analysis. The present approach allowed the determination of molecular weight distributions of the carbohydrates and of lignin in native and processed woods, without preparative component isolation steps. For the first time a component selective SEC analysis of sawdust preparations was made possible by the combination of two selective derivatization methods, namely; ionic liquid assisted benzoylation of the carbohydrate fraction and acetobromination of the lignin in acetic acid media. These were optimized for wood samples. The developed method was thus used to examine changes in softwood samples after degradative mechanical and/or chemical treatments, such as ball milling, steam explosion, green liquor pulping, and chemical oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The methodology can also be applied to examine changes in molecular weight and lignin-carbohydrate linkages that occur during wood-based biorefinery operations, such as pretreatments, and enzymatic saccharification. PMID:25563943

Leskinen, Timo; Kelley, Stephen S; Argyropoulos, Dimitris S

2015-03-30

78

Domain 5 of high molecular weight kininogen is antibacterial.  

PubMed

Antimicrobial peptides are important effectors of the innate immune system. These peptides belong to a multifunctional group of molecules that apart from their antibacterial activities also interact with mammalian cells and glycosaminoglycans and control chemotaxis, apoptosis, and angiogenesis. Here we demonstrate a novel antimicrobial activity of the heparin-binding and cell-binding domain 5 of high molecular weight kininogen. Antimicrobial epitopes of domain 5 were characterized by analysis of overlapping peptides. A peptide, HKH20 (His(479)-His(498)), efficiently killed the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa and the Gram-positive Enterococcus faecalis. Fluorescence microscopy and electron microscopy demonstrated that HKH20 binds to and induces breaks in bacterial membranes. Furthermore, no discernible hemolysis or membrane-permeabilizing effects on eukaryotic cells were noted. Proteolytic degradation of high molecular weight kininogen by neutrophil-derived proteases as well as the metalloproteinase elastase from P. aeruginosa yielded fragments comprising HKH20 epitopes, indicating that kininogen-derived antibacterial peptides are released during proteolysis. PMID:16091369

Nordahl, Emma Andersson; Rydengård, Victoria; Mörgelin, Matthias; Schmidtchen, Artur

2005-10-14

79

Enhancing the production of higher molecular weight hydrocarbons from lower molecular weight hydrocarbons by the additions of aluminum vapor to the feed  

SciTech Connect

In a continuous catalyst process for the production of higher molecular weight hydrocarbons from lower molecular weight hydrocarbons in which a lower molecular weight hydrocarbon containing reaction gas is contacted in a reaction zone with a higher molecular weight hydrocarbon synthesis catalyst under C/sub 2/..mu.. hydrocarbon synthesis conditions, the improvement is described comprising increasing production of higher molecular weight hydrocarbons by the addition of an effective amount of aluminum metal vapor to the reaction gas. The synthesis conditions include a temperature greater than 1000/sup 0/C. and a gas hourly space velocity of greater than 3200 hr/sup -1/ and wherein the hydrocarbon synthesis catalyst contains a carbide, nitride, boride or oxide of a Group I-A, II-A, III-A, IV-B or actinide series metal.

Devries, L.; Ryason, P.R.

1988-03-15

80

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

PubMed

An easy approach was reported to achieve high mechanical properties of ultrahigh-molecular-weight polyethylene (UHMWPE)-based polyethylene (PE) blend for artificial joint application without the sacrifice of the original excellent wear and fatigue behavior of UHMWPE. The PE blend with desirable fluidity was obtained by melt mixing UHMWPE and low molecular weight polyethylene (LMWPE), and then was processed by a modified injection molding technology-oscillatory shear injection molding (OSIM). Morphological observation of the OSIM PE blend showed LMWPE contained well-defined interlocking shish-kebab self-reinforced superstructure. Addition of a small amount of long chain polyethylene (2 wt %) to LMWPE greatly induced formation of rich shish-kebabs. The ultimate tensile strength considerably increased from 27.6 MPa for conventional compression molded UHMWPE up to 78.4 MPa for OSIM PE blend along the flow direction and up to 33.5 MPa in its transverse direction. The impact strength of OSIM PE blend was increased by 46% and 7% for OSIM PE blend in the direction parallel and vertical to the shear flow, respectively. Wear and fatigue resistance were comparable to conventional compression molded UHMWPE. The superb performance of the OSIM PE blend was originated from formation of rich interlocking shish-kebab superstructure while maintaining unique properties of UHMWPE. The present results suggested the OSIM PE blend has high potential for artificial joint application. PMID:22339721

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

2012-03-01

81

Fast, accurate, and reproducible automatic segmentation of the brain in T1-weighted volume MRI data.  

PubMed

A new fast automated algorithm has been developed to segment the brain from T1-weighted volume MR images. The algorithm uses automated thresholding and morphological operations. It is fully three-dimensional and therefore independent of scan orientation. The validity and the performance of the algorithm were evaluated by comparing the automatically calculated brain volume with semi-automated measurements in 10 subjects, by calculating the brain volume from repeated scans in another 10 subjects, and by visual inspection. The mean and standard deviation of the difference between semi-automated and automated measurements were 0.56% and 2.8% of the mean brain volume, respectively, which is within inter-observer variability of the semi-automated method. The mean and standard deviation of the difference between the total volumes calculated from repeated scans were 0.40% and 1.2% of the mean brain volume, respectively. Good results were also obtained from a scan of abnormal brains. PMID:10398958

Lemieux, L; Hagemann, G; Krakow, K; Woermann, F G

1999-07-01

82

Electrophilic reaction chemistry of low molecular weight respiratory sensitizers.  

PubMed

Certain types of low molecular weight chemicals have the ability to cause respiratory sensitization via haptenation of carrier proteins. It has been suggested that such chemicals must contain multiple "reactive" functional groups to elicit an immune response. In contrast to the well-developed electrophilic reaction chemistry ideas detailing the initial haptenation event for skin sensitization, no detailed mechanistic chemistry analysis has been performed for respiratory sensitization. The aim of this study, therefore, was to perform an electrophilic reaction chemistry analysis to explain the differing respiratory sensitizing potentials of 16 chemicals containing both single and multiple functional groups. The analysis has been supported by quantum chemical calculations probing the electrophilicities of the reactive chemicals. These calculations suggest that within each mechanistic category differing "reactivity thresholds" exist that must be passed for respiratory sensitization to occur. In addition, this study highlights how such mechanistically driven category formation could be used as an in silico hazard identification tool. PMID:19610608

Enoch, Steven J; Roberts, David W; Cronin, Mark T D

2009-08-01

83

Gels and foams from ultrahigh molecular weight polyethylene  

SciTech Connect

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

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

1988-07-01

84

Apparatus and method of determining molecular weight of large molecules  

DOEpatents

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

Fuerstenau, Stephen (Montrose, CA); Benner, W. Henry (Danville, CA); Madden, Norman (Livermore, CA); Searles, William (Fremont, CA)

1998-01-01

85

Apparatus and method of determining molecular weight of large molecules  

DOEpatents

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

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

1998-06-23

86

Low-molecular-weight xylanase from Trichoderma viride  

SciTech Connect

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

Ujiie, M.; Roy, C.; Yaguchi, M. (Inst. of Biological Sciences, Ottawa (Canada))

1991-06-01

87

Effect of Molecular Weight on Hydrated Morphologies of the Short-Side-Chain Perfluorosulfonic Acid Membrane  

E-print Network

either the length of the side chain or equivalent weight (EW) of the ionomer is changed [Wu et al. EnergyEffect of Molecular Weight on Hydrated Morphologies of the Short-Side-Chain Perfluorosulfonic Acid) simulations in an attempt to better understand how molecular weight (MW) affects the hydrated morphology

Elliott, James

88

Anaphylactic reactions to low-molecular weight chemicals.  

PubMed

Low-molecular weight chemicals (haptens) include a large group of chemical compounds occurring in work environment, items of everyday use (cleaning products, clothing, footwear, gloves, furniture), jewelry (earrings, bracelets), drugs, especially in cosmetics. They cause type IV hypersensitive reactions. During the induction phase of delayed-type hypersensitivity, haptens form complexes with skin proteins. After internalization through antigen presenting cells, they are bound to MHC class II molecules. Next, they are exposed against specific T-lymphocytes, what triggers activation of Th1 cells mainly. After repeating exposition to that hapten, during effector phase, Th1 induce production of cytokines affecting non-specific inflammatory cells. Usually, it causes contact dermatitis. However, occasionally incidence of immediate generalized reactions after contact with some kinds of haptens is noticed. A question arises, how the hapten does induce symptoms which are typical for anaphylaxis, and what contributes to amplification of this mechanism. It seems that this phenomenon arises from pathomechanism occurring in contact urticaria syndrome in which an anaphylactic reaction may be caused either by contact of sensitized skin with protein antigens, high-molecular weight allergens, or haptens. One of the hypotheses indicates the leading role of basophiles in this process. Their contact with haptens, may cause to release mediators of immediate allergic reaction (histamine, eicosanoids) and to produce cytokines corresponding to Th2 cells profile. Furthermore, Th17 lymphocytes secreting pro-inflammatory interleukin-17 might be engaged into amplifying hypersensitivity into immediate reactions and regulatory T-cells may play role in the process, due to insufficient control of the activity of effector cells. PMID:25661919

Nowak, Daria; Panaszek, Bernard

2015-01-01

89

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

NASA Technical Reports Server (NTRS)

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.

Asunmaa, S. K.; Haack, R.

1977-01-01

90

Mechanical property and molecular weight distribution changes with photo- and chemical-degradation on LDPE films  

Microsoft Academic Search

In order to clarify the effect of photo- and chemical-degradation on the structure of polyethylene materials, the change in molecular weight distribution and mechanical properties of photo- and chemical-degraded LDPE films were investigated. The molecular weight distribution was significantly changed with photo-exposing times, and the drastic change appeared especially for 8 days-exposed samples where the molecular weight of the high

Eiichi Miyagawa; Katsuhisa Tokumitsu; Akira Tanaka; Koh-hei Nitta

2007-01-01

91

Application of the G-JF discrete-time thermostat for fast and accurate molecular simulations  

NASA Astrophysics Data System (ADS)

A new Langevin-Verlet thermostat that preserves the fluctuation-dissipation relationship for discrete time steps is applied to molecular modeling and tested against several popular suites (AMBER, GROMACS, LAMMPS) using a small molecule as an example that can be easily simulated by all three packages. Contrary to existing methods, the new thermostat exhibits no detectable changes in the sampling statistics as the time step is varied in the entire numerical stability range. The simple form of the method, which we express in the three common forms (Velocity-Explicit, Störmer-Verlet, and Leap-Frog), allows for easy implementation within existing molecular simulation packages to achieve faster and more accurate results with no cost in either computing time or programming complexity.

Grønbech-Jensen, Niels; Hayre, Natha Robert; Farago, Oded

2014-02-01

92

Synthesis of a Low-Molecular-Weight Form of Exopolysaccharide by Bradyrhizobium japonicum USDA 110  

PubMed Central

A novel extracellular low-molecular-weight polysaccharide was detected as a contaminant within extracellular cyclic ?-1,6-?-1,3-glucan preparations from Bradyrhizobium japonicum USDA 110 cultures. Compositional analysis, methylation analysis, and nuclear magnetic resonance analysis revealed that this low-molecular-weight polysaccharide was composed of the same pentasaccharide repeating unit previously described for the high-molecular-weight form of the exopolysaccharide (EPS) synthesized by B. japonicum strains. Mass spectrometry analysis indicated that the size of this low-molecular-weight form of EPS was consistent with a dimeric form of the pentasaccharide repeating unit. PMID:11157281

Louch, Heather A.; Miller, Karen J.

2001-01-01

93

Kinetics of Formation of Molecular Weight Distribution of Epoxy Composite  

NASA Astrophysics Data System (ADS)

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

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

94

Optimization of parameters for coverage of low molecular weight proteins.  

PubMed

Proteins with molecular weights of <25 kDa are involved in major biological processes such as ribosome formation, stress adaption (e.g., temperature reduction) and cell cycle control. Despite their importance, the coverage of smaller proteins in standard proteome studies is rather sparse. Here we investigated biochemical and mass spectrometric parameters that influence coverage and validity of identification. The underrepresentation of low molecular weight (LMW) proteins may be attributed to the low numbers of proteolytic peptides formed by tryptic digestion as well as their tendency to be lost in protein separation and concentration/desalting procedures. In a systematic investigation of the LMW proteome of Escherichia coli, a total of 455 LMW proteins (27% of the 1672 listed in the SwissProt protein database) were identified, corresponding to a coverage of 62% of the known cytosolic LMW proteins. Of these proteins, 93 had not yet been functionally classified, and five had not previously been confirmed at the protein level. In this study, the influences of protein extraction (either urea or TFA), proteolytic digestion (solely, and the combined usage of trypsin and AspN as endoproteases) and protein separation (gel- or non-gel-based) were investigated. Compared to the standard procedure based solely on the use of urea lysis buffer, in-gel separation and tryptic digestion, the complementary use of TFA for extraction or endoprotease AspN for proteolysis permits the identification of an extra 72 (32%) and 51 proteins (23%), respectively. Regarding mass spectrometry analysis with an LTQ Orbitrap mass spectrometer, collision-induced fragmentation (CID and HCD) and electron transfer dissociation using the linear ion trap (IT) or the Orbitrap as the analyzer were compared. IT-CID was found to yield the best identification rate, whereas IT-ETD provided almost comparable results in terms of LMW proteome coverage. The high overlap between the proteins identified with IT-CID and IT-ETD allowed the validation of 75% of the identified proteins using this orthogonal fragmentation technique. Furthermore, a new approach to evaluating and improving the completeness of protein databases that utilizes the program RNAcode was introduced and examined. PMID:20803007

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

2010-12-01

95

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

SciTech Connect

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

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

1984-12-01

96

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

Code of Federal Regulations, 2010 CFR

...Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000. ...Isopropylidenediphenol-epichlorohydrin resins minimum molecular weight 10,000. ...Isopropylidenediphenol-epichlo-rohydrin resins having a minimum molecular...

2010-04-01

97

Absolute Molecular Weight Distribution of Low-Molecular-Weight Heparins by Size-Exclusion Chromatography with Multiangle Laser Light Scattering Detection  

Microsoft Academic Search

The absolute molecular weight (Mr) distribution of seven low-molecular-weight (LMW) heparin products was determined by size-exclusion chromatography (SEC) coupled with multiangle laser light scattering (MALLS) detection. The SEC\\/MALLS technique does not rely on relativeMrstandards for column calibration and yields absoluteMrestimates directly from the angular dependence of scattered light intensity as a function of concentration, as formulated by light scattering theory.

James E. Knobloch; Patrick N. Shaklee

1997-01-01

98

Low molecular weight protamine (LMWP) as nontoxic heparin\\/low molecular weight heparin antidote (II): In vitro evaluation of efficacy and toxicity  

Microsoft Academic Search

Patients undergoing anticoagulation with heparin or low molecular weight heparin (LMWH) require a superior antidote that possesses\\u000a more selective biological actions and a better safety profile than protamine. We had previously developed 2 low molecular\\u000a weight protamine (LMWP) fractions (TDSP4 and TDSP5) from thermolysin-digested protamine as potential nontoxie, heparin-neutralizing\\u000a agents. In this, the second article in this series, studies focused

Li-Chien Chang; Jun Feng Liang; Hsiao-Feng Lee; Lai Ming Lee; Victor C. Yang

2001-01-01

99

Accurate phosphoregulation of kinetochore–microtubule affinity requires unconstrained molecular interactions  

PubMed Central

Accurate chromosome segregation relies on dynamic interactions between microtubules (MTs) and the NDC80 complex, a major kinetochore MT-binding component. Phosphorylation at multiple residues of its Hec1 subunit may tune kinetochore–MT binding affinity for diverse mitotic functions, but molecular details of such phosphoregulation remain elusive. Using quantitative analyses of mitotic progression in mammalian cells, we show that Hec1 phosphorylation provides graded control of kinetochore–MT affinity. In contrast, modeling the kinetochore interface with repetitive MT binding sites predicts a switchlike response. To reconcile these findings, we hypothesize that interactions between NDC80 complexes and MTs are not constrained, i.e., the NDC80 complexes can alternate their binding between adjacent kinetochore MTs. Experiments using cells with phosphomimetic Hec1 mutants corroborate predictions of such a model but not of the repetitive sites model. We propose that accurate regulation of kinetochore–MT affinity is driven by incremental phosphorylation of an NDC80 molecular “lawn,” in which the NDC80–MT bonds reorganize dynamically in response to the number and stability of MT attachments. PMID:24982430

Zaytsev, Anatoly V.; Sundin, Lynsie J.R.; DeLuca, Keith F.

2014-01-01

100

Accurate phosphoregulation of kinetochore-microtubule affinity requires unconstrained molecular interactions.  

PubMed

Accurate chromosome segregation relies on dynamic interactions between microtubules (MTs) and the NDC80 complex, a major kinetochore MT-binding component. Phosphorylation at multiple residues of its Hec1 subunit may tune kinetochore-MT binding affinity for diverse mitotic functions, but molecular details of such phosphoregulation remain elusive. Using quantitative analyses of mitotic progression in mammalian cells, we show that Hec1 phosphorylation provides graded control of kinetochore-MT affinity. In contrast, modeling the kinetochore interface with repetitive MT binding sites predicts a switchlike response. To reconcile these findings, we hypothesize that interactions between NDC80 complexes and MTs are not constrained, i.e., the NDC80 complexes can alternate their binding between adjacent kinetochore MTs. Experiments using cells with phosphomimetic Hec1 mutants corroborate predictions of such a model but not of the repetitive sites model. We propose that accurate regulation of kinetochore-MT affinity is driven by incremental phosphorylation of an NDC80 molecular "lawn," in which the NDC80-MT bonds reorganize dynamically in response to the number and stability of MT attachments. PMID:24982430

Zaytsev, Anatoly V; Sundin, Lynsie J R; DeLuca, Keith F; Grishchuk, Ekaterina L; DeLuca, Jennifer G

2014-07-01

101

Molecular Weight Dependence of Polymersome Membrane Elasticity and Stability  

E-print Network

Vesicles prepared in water from a series of diblock copolymers and termed "polymersomes" are physically characterized. With increasing molecular weight $\\bar{M}_n$, the hydrophobic core thickness $d$ for the self-assembled bilayers of polyethyleneoxide - polybutadiene (PEO-PBD) increases up to 20 $nm$ - considerably greater than any previously studied lipid system. The mechanical responses of these membranes, specifically, the area elastic modulus $K_a$ and maximal areal strain $\\alpha_c$ are measured by micromanipulation. As expected for interface-dominated elasticity, $K_a$ ($\\simeq$ 100 $pN/nm$) is found to be independent of $\\bar{M}_n$. Related mean-field ideas also predict a limiting value for $\\alpha_c$ which is universal and about 10-fold above that typical of lipids. Experiments indeed show $\\alpha_c$ generally increases with $\\bar{M}_n$, coming close to the theoretical limit before stress relaxation is opposed by what might be chain entanglements at the highest $\\bar{M}_n$. The results highlight the interfacial limits of self-assemblies at the nano-scale.

Harry Bermudez; Aaron K. Brannan; Daniel A. Hammer; Frank S. Bates; Dennis E. Discher

2001-10-04

102

Low molecular weight heparin use in unexplained recurrent miscarriage  

PubMed Central

Objective: The aim of the study was to investigate whether the use of low molecular weight heparin (LMWH) improve live birth rates when compared with control group in patients with unexplained recurrent miscarriages (URM). Methods: In this prospective observational study 150 women with a history of two or more previous unexplained first trimester pregnancy loss who received LMWH; either enoxaparin (n=50), tinzaparin (n=50) or nothing (n=50) were followed for the pregnancy outcome measures. Only the patients who have used standardized dosage of LMWH (4000 IU/day enoxaparin or 3500 IU/day tinzaparin ) were included to the study. The primary end point was the live birth rate and secondary end points were the side effects, late pregnancy complications and neonatal outcome in the study cohorts. Results: Live birth was achieved 85% of the LMWH group and 66% of the control group (p=0.007). According to the subgroup analysis; live birth rates did not differ significantly between the enoxaparin and tinzaparin group (84% and 86%, respectively). Maternal and neonatal side effects were not statistically significant among the study participants. Conclusion: Thromboprophylaxis with LMWH resulted in a improved live-birth rate in patient with 2 or more consecutive unexplained recurrent pregnancy loss. Nevertheless these findings need to be confirmed in larger randomized trials.

Yuksel, Halide; Kayatas, Semra; Boza, Aysen Telce; Api, Murat; Ertekin, A. Aktug; Cam, Cetin

2014-01-01

103

Antiaging activity of low molecular weight peptide from Paphia undulate  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

104

Molecular weight distributions of polydisperse polymers in coexisting liquid phases  

NASA Astrophysics Data System (ADS)

We present new experimental measurements of the molecular weight (MW) distributions in coexisting liquid phases for three polymer/solvent systems. We studied samples at the critical compositions and at four temperatures in the two-phase regions. For polystyrene in methylcyclohexane (with an upper critical solution point), we observed the expected fractionation between phases, with a higher average MW in the lower, polymer-rich phase. For poly(ethylene oxide) in 2, 6-lutidine+water (with a lower critical solution point), the total polymer mass is nearly equal in the two phases, but the polymers of higher average MW equilibrate into the upper, 2,6-lutidine-rich phase. For poly(ethylene oxide) in isobutyric acid+water (with an upper critical solution point), most of the total polymer mass is in the upper, isobutyric acid-rich phase, but the polymers of higher average MW equilibrate into the lower, water-rich phase; moreover, the fractionation in this case is quite dramatic, with almost a factor of 2 difference in average MW between the phases and a significant decrease in polydispersity for the lower phase. Our results support prior experimental results on this phenomenon that find that a basic Flory-Huggins (FH) theory is inadequate. More recent theoretical considerations suggest that the difference between FH theory and experiments is due to non-mean field effects, but this theory awaits direct comparison to experiments.

Shresth, R. Saurabh; McDonald, R. Christopher; Greer, Sandra C.

2002-11-01

105

A novel high molecular weight glutenin subunit from Australopyrum retrofractum.  

PubMed

We describe the sequence of a gene encoding a high molecular weight glutenin subunit (HMW-GS) expressed in the endosperm of the wheat relative Australopyrum retrofractum. Although the subunit has a similar primary structure to that HMW-GS genes present in other Triticeae species, its N-terminal domain is shorter, its central repetitive domain includes a unique dodecameric motif, and its C-terminal domain contain an extra cysteine residue. A phylogenetic analysis showed that the Glu-W1 gene is neither a true x- nor a true y-type subunit, although it is more closely related to the y-type genes present in the K and E genomes than to any other published HMW-GS gene. All these results indicated that this novel subunit may undergo a special evolutionary process different from other Triticeae species. A flour supplementation experiment showed that the Glu-W1 subunit has a negative effect on dough quality, which might be the result of interaction between the two closely placed cysteine residues in the C-terminal region. PMID:20058039

Liu, Shuwei; Zhao, Feng; Gao, Xin; Chen, Fanguo; Xia, Guangmin

2010-07-01

106

Photochemical Preparation of a Novel Low Molecular Weight Heparin  

PubMed Central

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

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

2011-01-01

107

Photoelectrical characterization of a new low molecular weight compound  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

108

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

SciTech Connect

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, and 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.

Tolbert, Allison [Georgia Institute of Technology, Atlanta] [Georgia Institute of Technology, Atlanta; Akinosho, Hannah [Georgia Institute of Technology, Atlanta] [Georgia Institute of Technology, Atlanta; Khunsupat, Taya Ratayakorn [ORNL] [ORNL; Naskar, Amit K [ORNL] [ORNL; Ragauskas, Arthur [Georgia Institute of Technology, Atlanta] [Georgia Institute of Technology, Atlanta

2014-01-01

109

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

PubMed Central

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

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

2014-01-01

110

Purification of a low molecular weight fucoidan for SPECT molecular imaging of myocardial infarction.  

PubMed

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

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

2014-09-01

111

A Simple, Inexpensive Molecular Weight Measurement for Water-Soluble Polymers Using Microemulsions.  

ERIC Educational Resources Information Center

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…

Mathias, Lon J.; Moore, D. Roger

1985-01-01

112

CONTEMPORARY CHALLENGES IN AUTOIMMUNITY Effects of Low-Molecular-Weight Heparin  

E-print Network

CONTEMPORARY CHALLENGES IN AUTOIMMUNITY Effects of Low-Molecular-Weight Heparin on Adhesion, Slovenia Heparins represent an efficient treatment of acute thrombosis and obstetric compli- cations to the efficacy of heparin treatment in APS. Key words: low-molecular-weight heparin; anti-2-glycoprotein I

Iglic, Ales

113

Molecular Weight Determination by an Improved Temperature-Monitored Vapor-Density Method.  

ERIC Educational Resources Information Center

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)

Grider, Douglas J.; And Others

1988-01-01

114

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

Microsoft Academic Search

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. The authors 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

Stephen E. Cabaniss; Qunhui Zhou; Patricia A. Maurice; Yu-Ping Chin; George R. Aiken

2000-01-01

115

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators  

Technology Transfer Automated Retrieval System (TEKTRAN)

Low molecular weight gelators are an important class of molecules. The supramolecular gels formed by carbohydrate derived low molecular weight gelators, are interesting soft materials that show great potential for many applications. Previously, we synthesized a series of methyl 4,6-O-benzylidene-a-D...

116

Correlation between gas molecular weight, heating value and sonic speed under variable compositions of natural gas  

Microsoft Academic Search

A simulation study of likely uncertainties in molecular weight and heating value of the gas mixture as predicted from measured or calculated sonic speed. The sonic speed, molecular weight and heating value of natural gas were studied as a function of random fluctuation of the gas fractions. A method of sonic speed prediction was developed and used for over 50,000

L. Burstein; D. Ingman; Y. Michlin

1999-01-01

117

Using Protein Charge Ladders To Estimate the Effective Charges and Molecular Weights of  

E-print Network

Using Protein Charge Ladders To Estimate the Effective Charges and Molecular Weights of Proteins electrophoresis (CE) and protein charge ladders to estimate values of effective charge (Z) and molecular weight of proteins under nondenaturing conditions. A panel of 14 proteins with a range of charges and shapes

Gao, Jinming

118

Preparation and characterization of molecular weight fractions of guar galactomannans using acid and enzymatic hydrolysis  

Microsoft Academic Search

A procedure is described for the preparation of large amounts of guar galactomannan by acid hydrolysis that yields samples of various molecular weights (MW) with uniform polydispersity. This contrasts with preparation by enzymatic degradation that yields samples with a marked increase in polydispersity and a much broader molecular weight distribution (MWD). Acid hydrolyzed guar samples had a Mark–Houwink–Sakurada (MHS) relationship

Yu Cheng; Kirk M Brown; Robert K Prud'homme

2002-01-01

119

A hierarchical approach to accurate predictions of macroscopic thermodynamic behavior from quantum mechanics and molecular simulations  

NASA Astrophysics Data System (ADS)

The combination of molecular simulations and potentials obtained from quantum chemistry is shown to be able to provide reasonably accurate thermodynamic property predictions. Gibbs ensemble Monte Carlo simulations are used to understand the effects of small perturbations to various regions of the model Lennard-Jones 12-6 potential. However, when the phase behavior and second virial coefficient are scaled by the critical properties calculated for each potential, the results obey a corresponding states relation suggesting a non-uniqueness problem for interaction potentials fit to experimental phase behavior. Several variations of a procedure collectively referred to as quantum mechanical Hybrid Methods for Interaction Energies (HM-IE) are developed and used to accurately estimate interaction energies from CCSD(T) calculations with a large basis set in a computationally efficient manner for the neon-neon, acetylene-acetylene, and nitrogen-benzene systems. Using these results and methods, an ab initio, pairwise-additive, site-site potential for acetylene is determined and then improved using results from molecular simulations using this initial potential. The initial simulation results also indicate that a limited range of energies important for accurate phase behavior predictions. Second virial coefficients calculated from the improved potential indicate that one set of experimental data in the literature is likely erroneous. This prescription is then applied to methanethiol. Difficulties in modeling the effects of the lone pair electrons suggest that charges on the lone pair sites negatively impact the ability of the intermolecular potential to describe certain orientations, but that the lone pair sites may be necessary to reasonably duplicate the interaction energies for several orientations. Two possible methods for incorporating the effects of three-body interactions into simulations within the pairwise-additivity formulation are also developed. A low density approximation for the pair and three-body distribution functions is simpler to implement, but the results based on the numerical solution of the inhomogeneous Ornstein-Zernike equation using the Percus-Yevick closure are more accurate. Given the low temperatures for phase equilibria of the model system, neon, several approximations to estimate the quantum effects on the atomic nuclei are presented with reasonable success.

Garrison, Stephen L.

2005-07-01

120

High Molecular Weight Dimer Esters in ?-Pinene Secondary Organic Aerosol  

NASA Astrophysics Data System (ADS)

Monoterpenes, such as ?-pinene, constitute an important group of biogenic volatile organic compounds (BVOC). Once emitted into the atmosphere ?-pinene is removed by oxidization by the hydroxyl radical (OH), reactions with ozone (O3), and with nitrate radicals (NO3) resulting in the formation of first-generation oxidation products, such as semi-volatile carboxylic acids. In addition, higher molecular weight dimer esters originating from the oxidation of ?-pinene have been observed in both laboratory-generated and ambient secondary organic aerosols (SOA). While recent studies suggest that the dimers are formed through esterification between carboxylic acids in the particle phase, the formation mechanism of the dimer esters is still ambiguous. In this work, we present the results of a series of smog chamber experiments to assess the formation of dimer esters formed from the oxidation of ?-pinene. Experiments were conducted in the University of North Carolina (UNC) dual outdoor smog chamber facility to investigate the effect of oxidant species (OH versus O3), relative humidity (RH), and seed aerosol acidity in order to obtain a better understanding of the conditions leading to the formation of the dimer esters and how these parameters may affect the formation and chemical composition of SOA. The chemical composition of ?-pinene SOA was investigated by ultra-performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS), and a total of eight carboxylic acids and four dimer esters were identified, constituting between 8 and 12 % of the total ?-pinene SOA mass.

Kristensen, Kasper; Cui, Tianqu; Zhang, Haofei; Gold, Avram; Glasius, Marianne; Surratt, Jason D.

2014-05-01

121

Fast and accurate quantum molecular dynamics of dense plasmas across temperature regimes  

E-print Network

We have developed and implemented a new quantum molecular dynamics approximation that allows fast and accurate simulations of dense plasmas from cold to hot conditions. The method is based on a carefully designed orbital-free implementation of density functional theory (DFT). The results for hydrogen and aluminum are in very good agreement with Kohn-Sham (orbital-based) DFT and path integral Monte Carlo (PIMC) for microscopic features such as the electron density as well as equation of state. The present approach does not scale with temperature and hence extends to higher temperatures than is accessible in Kohn-Sham method and lower temperatures than is accessible by PIMC, while being significantly less computationally expensive than either of those two methods

Sjostrom, Travis

2014-01-01

122

Molecular chaperone properties of the high molecular weight aggregate from aged lens  

NASA Technical Reports Server (NTRS)

The high molecular weight aggregate (HMWA) fraction was isolated from the water soluble proteins of aged bovine lenses. Its composition and ability to inhibit heat-induced denaturation and aggregation were compared with the lower molecular weight, oligomeric fraction of alpha isolated from the same lens. Although the major components of both fractions were the alpha-A and alpha-B chains, the HMWA fraction possessed a decreased ability to protect other proteins against heat-induced denaturation and aggregation. Immunoelectron microscopy of both fractions demonstrated that alpha particles from the HMWA fraction contained increased amounts of beta and gamma crystallins, bound to a central region of the supramolecular complex. Together, these results demonstrate that alpha crystallins found in the HMWA fraction possess a decreased ability to protect against heat-induced denaturation and aggregation, and suggest that at least part of this decrease could be due to the increased presence of beta and gamma crystallins complexed to the putative chaperone receptor site of the alpha particles.

Takemoto, L.; Boyle, D.; Spooner, B. S. (Principal Investigator)

1994-01-01

123

The renal handling of low molecular weight proteins  

PubMed Central

The present study was directed toward determining the role of the kidney in the metabolism of various classes of serum proteins and to define the urinary protein excretion patterns and the pathogenesis of disorders of protein metabolism in patients with proteinuria. To this end, the metabolic fates of a small protein, ?-L chain (mol wt 44,000), and a protein of intermediate size, IgG (mol wt 160,000), were studied in controls and patients with renal disease. Controls metabolized 0.28%/hr of circulating IgG and 22.3%/hr of circulating ?-L chain. All the IgG and 99% of the ?-L chain was catabolized with the remaining ?-L chain lost intact into the urine. The kidney was shown to be the major site of catabolism for small serum proteins. Three distinct disorders of protein metabolism were noted in patients with renal tubular disease and tubular proteinuria, glomerular disease (the nephrotic syndrome), and disease involving the entire nephrons (uremia), respectively. Patients with renal tubular disease had a 50-fold increase in the daily urinary excretion of 15-40,000 molecular weight proteins such as lysozyme and ?-L chains. Serum IgG and ?-L chain survivals were normal; however, the fraction of the over-all ?-L chain metabolism accounted for by proteinuria was increased 40-fold whereas endogenous catabolism was correspondingly decreased. Thus, tubular proteinuria results from a failure of proximal tubular uptake and catabolism of small proteins that are normally filtered through the glomerulus. Patients with the nephrotic syndrome had a slight increase in ?-L chain survival whereas IgG survival was decreased and the fraction of IgG lost in the urine was markedly increased. Here, abnormal glomerular permeability to proteins of intermediate size is the basic abnormality. Patients with uremia had a normal IgG survival but a four to 10-fold prolongation of ?-L chain survival due to loss of entire nephrons, the major site of metabolism of these proteins. This results in an increase (up to 10-fold) in the serum concentration of ?-L chain, lysozyme, and other small biologically active proteins, a phenomenon that may be of importance in causing some of the manifestations of the uremic syndrome. Images PMID:5054468

Waldmann, Thomas A.; Strober, Warren; Mogielnicki, R. Peter

1972-01-01

124

How Does the Preparation of Rye Porridge Affect Molecular Weight Distribution of Extractable Dietary Fibers?  

PubMed Central

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)-?-d-glucan (?-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 ?-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 ?-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 ?-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

Rakha, Allah; Åman, Per; Andersson, Roger

2011-01-01

125

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

NASA Astrophysics Data System (ADS)

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

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

1981-11-01

126

Accurate measurement of the molecular thickness of thin organic shells on small inorganic cores using dynamic light scattering.  

PubMed

Dynamic light scattering (DLS) has become a primary nanoparticle characterization technique with applications from material characterization to biological and environmental detection. With the expansion in DLS use from homogeneous spheres to more complicated nanostructures comes a decrease in accuracy. Much research has been performed to develop different diffusion models that account for the vastly different structures, but little attention has been given to the effect on the light scattering properties in relation to DLS. In this work, small (core size < 5 nm) core-shell nanoparticles were used as a case study to measure the capping thickness of a layer of dodecanethiol (DDT) on Au and ZnO nanoparticles by DLS. We find that the DDT shell has very little effect on the scattering properties of the inorganic core and, hence, can be ignored to a first approximation. However, this results in conventional DLS analysis overestimating the hydrodynamic size in the volume- and number-weighted distributions. With the introduction of a simple correction formula that more accurately yields hydrodynamic size distributions, a more precise determination of the molecular shell thickness is obtained. With this correction, the measured thickness of the DDT shell was found to be 7.3 ± 0.3 Å, much less than the extended chain length of 16 Å. This organic layer thickness suggests that, on small nanoparticles, the DDT monolayer adopts a compact disordered structure rather than an open ordered structure on both ZnO and Au nanoparticle surfaces. These observations are in agreement with published molecular dynamics results. PMID:24386968

Shortell, Matthew P; Fernando, Joseph F S; Jaatinen, Esa A; Waclawik, Eric R

2014-01-21

127

Rheology of Ziegler–Natta and metallocene high-density polyethylenes: broad molecular weight distribution effects  

Microsoft Academic Search

The linear viscoelastic properties of two series of Ziegler–Natta and metallocene HDPEs (ZN-HDPEs and m-HDPEs, respectively)\\u000a of broad molecular weight distribution (MWD) have been studied. Correlations between zero-shear viscosity and molecular weight\\u000a and molecular weight distribution show that the breadth of the MWD for m-HDPEs plays a role. Other interesting correlations\\u000a between the crossover modulus and steady-state compliance with MWD

Mahmoud Ansari; Savvas G. Hatzikiriakos; Ashish M. Sukhadia; David C. Rohlfing

2011-01-01

128

Effect of sterilization irradiation on friction and wear of ultrahigh-molecular-weight polyethylene  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

129

Enhanced resolution of low molecular weight poly(ethylene glycol) in nanopore analysis.  

PubMed

A design with conjugation of DNA hairpin structure to the poly(ethylene glycol) molecule was presented to enhance the temporal resolution of low molecular weight poly(ethylene glycol) in nanopore studies. By the virtue of this design, detection of an individual PEG with molecular weight as low as 140 Da was achieved at the single-molecule level in solution, which provides a novel strategy for characterization of an individual small molecule within a nanopore. Furthermore, we found that the current duration time of poly(ethylene glycol) was scaled with the relative molecular weight, which has a potential application in single-molecule detection. PMID:25457124

Cao, Chan; Ying, Yi-Lun; Gu, Zhen; Long, Yi-Tao

2014-12-16

130

High molecular weight first generation PMR polyimides for 343 C applications  

NASA Technical Reports Server (NTRS)

The effect of molecular weight on 343 C thermo-oxidative stability (TOS), mechanical properties, and processability, of the first generation PMR polyimides was studied. Graphite fiber reinforced PMR-15, PMR-30, PMR-50, and PMR-75 composites (corresponding to formulated molecular weights of 1500, 3000, 5000, and 7500, respectively) were fabricated using a simulated autoclave process. The data reveals that while alternate autoclave cure schedules are required for the high molecular weight resins, low void laminates can be fabricated which have significantly improved TOS over PMR-15, with only a small sacrifice in mechanical properties.

Malarik, Diane C.; Vannucci, Raymond D.

1991-01-01

131

Accurate ensemble molecular dynamics binding free energy ranking of multidrug-resistant HIV-1 proteases.  

PubMed

Accurate calculation of important thermodynamic properties, such as macromolecular binding free energies, is one of the principal goals of molecular dynamics simulations. However, single long simulation frequently produces incorrectly converged quantitative results due to inadequate sampling of conformational space in a feasible wall-clock time. Multiple short (ensemble) simulations have been shown to explore conformational space more effectively than single long simulations, but the two methods have not yet been thermodynamically compared. Here we show that, for end-state binding free energy determination methods, ensemble simulations exhibit significantly enhanced thermodynamic sampling over single long simulations and result in accurate and converged relative binding free energies that are reproducible to within 0.5 kcal/mol. Completely correct ranking is obtained for six HIV-1 protease variants bound to lopinavir with a correlation coefficient of 0.89 and a mean relative deviation from experiment of 0.9 kcal/mol. Multidrug resistance to lopinavir is enthalpically driven and increases through a decrease in the protein-ligand van der Waals interaction, principally due to the V82A/I84V mutation, and an increase in net electrostatic repulsion due to water-mediated disruption of protein-ligand interactions in the catalytic region. Furthermore, we correctly rank, to within 1 kcal/mol of experiment, the substantially increased chemical potency of lopinavir binding to the wild-type protease compared to saquinavir and show that lopinavir takes advantage of a decreased net electrostatic repulsion to confer enhanced binding. Our approach is dependent on the combined use of petascale computing resources and on an automated simulation workflow to attain the required level of sampling and turn around time to obtain the results, which can be as little as three days. This level of performance promotes integration of such methodology with clinical decision support systems for the optimization of patient-specific therapy. PMID:20384328

Sadiq, S Kashif; Wright, David W; Kenway, Owain A; Coveney, Peter V

2010-05-24

132

Evaluation of diclofenac sodium sustained release matrix pellets: impact of polyethylene glycols molecular weight.  

PubMed

Sustained release matrix pellets loaded with 5% w/w diclofenac sodium (DS) were prepared using extrusion/spheronization technique. Different polyethylene glycols (PEGs) of different molecular weight, namely PEG 2000, PEG 4000 and PEG 6000, were mixed with avicel PH 101 in different weight ratios to manufacture the pellet formulations and water was used as a binder. Mix torque rheometer was used to characterize the pellets' wet mass. Also, the prepared pellets were characterized for their particle sizes, DS content, shape and morphology as well as the in vitro drug release. The results showed increasing PEG weight ratio resulted in a reduction of wet mass torque as well as binder ratio, especially at PEG high weight ratios (30% and 50%) and the extent of lowering wet mass peak torque was inversely proportional to PEG molecular weight. The manufactured pellets exhibited size range of 993 ?m to 1085 ?m with small span values. The drug release from pellets was governed by the molecular weight of PEG used, since increasing PEG molecular weight resulted in slowing the drug release rate from pellets, but increasing its level resulted in enhancing release rate. This was attributed to increasing pellet wet mass peak torque by increasing PEG molecular weight and lowering it by increasing PEG level. The prepared pellets showed non-Fickian or anomalous drug release or the coupled diffusion/polymer relaxation. PMID:25362811

Ibrahim, A; Shazly, A

2014-01-01

133

Improved performance of ultra-high molecular weight polyethylene for orthopedic applications  

E-print Network

A considerable number of total-joint replacement devices used in orthopedic medicine involve articulation between a metallic alloy and ultra-high molecular weight polyethylene (UHMWPE). Though this polymer has excellent wear resistance, the wear...

Plumlee, Kevin Grant

2009-05-15

134

Molecular weight, chain profile of rice amylopectin and starch pasting properties.  

PubMed

Differences in fine structure, average molecular size of amylopectin (AP) as well as clarity of the AP solution from indica waxy rice and high amylose (HAM) rice were examined. Despite similar amylose content (AM), rice starches displayed different pasting properties. Waxy APs had higher values of both number-average and weight-average molecular weight (Mn¯ and Mw¯) but lower values of intrinsic viscosity [?], compared to HAM APs. HAM APs had higher values of average chain length (CL¯), average external chain length (ECL¯), and a proportion of DP ? 37. Statistical correlations of mol proportions of debranched AP, branching parameters, and molecular weight of AP were calculated. The study showed that starch pasting properties and clarity of AP solutions were influenced by molecular weight and branching characteristics of AP. PMID:24751267

Kowittaya, Chutarat; Lumdubwong, Namfone

2014-08-01

135

Methods for increasing the thermal conductivity of ultra-high molecular weight polyethylene (UHMWPE)  

E-print Network

A two-part study was conducted to determine methods for producing ultra-high molecular weight polyethylene with high thermal conductivity by way of polymer chain orientation. The first portion of this report surveys current ...

Miler, Josef L

2006-01-01

136

Electrophoretic analysis of the molecular weight of murine mammary tumor virus RNA.  

PubMed Central

Molecular weight determinations of native and subunit RNAs of murine mammary tumor virus (MuMTV), a type B oncornavirus, were performed by polyacrylamide gel electrophoresis and compared with molecular weights of well-characterized avian cellular RNAs and tobacco mosaic virus RNA. From extrapolations of semilog plots of the molecular weights of the standard RNAs versus relative electrophoretic mobilities and Ferguson plots, the subunit and native RNAs of MuMTV were found to possess molecular weights of 2.93 X 10(6) and 6.45 X 10(6), respectively. These data support the assumption that two subunit molecules comprise the native RNA of MuMTV. Images PMID:195092

Dion, A S; Heine, U I; Pomenti, A A; Korb, J; Weber, G H

1977-01-01

137

Viscosity dependence of O2 escape from respiratory proteins as a function of cosolvent molecular weight.  

PubMed Central

Laser photodissociation of respiratory proteins is followed by fast geminate recombination competing with escape of the oxygen molecule into the solvent. The escape rate from myoglobin or hemerythrin has been shown previously to exhibit a reciprocal power-law dependence on viscosity. We have reinvestigated oxygen escape from hemerythrin using a number of viscous cosolvents of varying molecular weight, from glycerol to dextrans up to 500 kDa. In isoviscous solutions, the strong viscosity dependence observed with small cosolvents is progressively reduced upon increasing the cosolvent's molecular weight and disappears at molecular weights greater than about 100 kDa. Thus, viscosity is not a suitable independent parameter to describe the data. The power of the viscosity dependence of the rate coefficient is shown here to be a function of the cosolvent's molecular weight, suggesting that local protein-solvent interactions rather than bulky viscosity are affecting protein dynamics. PMID:7535116

Yedgar, S; Tetreau, C; Gavish, B; Lavalette, D

1995-01-01

138

An efficient and accurate molecular alignment and docking technique using ab initio quality scoring  

PubMed Central

An accurate and efficient molecular alignment technique is presented based on first principle electronic structure calculations. This new scheme maximizes quantum similarity matrices in the relative orientation of the molecules and uses Fourier transform techniques for two purposes. First, building up the numerical representation of true ab initio electronic densities and their Coulomb potentials is accelerated by the previously described Fourier transform Coulomb method. Second, the Fourier convolution technique is applied for accelerating optimizations in the translational coordinates. In order to avoid any interpolation error, the necessary analytical formulas are derived for the transformation of the ab initio wavefunctions in rotational coordinates. The results of our first implementation for a small test set are analyzed in detail and compared with published results of the literature. A new way of refinement of existing shape based alignments is also proposed by using Fourier convolutions of ab initio or other approximate electron densities. This new alignment technique is generally applicable for overlap, Coulomb, kinetic energy, etc., quantum similarity measures and can be extended to a genuine docking solution with ab initio scoring. PMID:18624561

Füsti-Molnár, László; Merz, Kenneth M.

2008-01-01

139

Non-Born-Oppenheimer potential energy curve: Hydrogen molecular ion with highly accurate free complement method.  

PubMed

Although the concept of a potential energy curve (PEC) originates from the outgrowth of the Born-Oppenheimer (BO) approximation, we propose the application of analysis methods for the physical PEC with non-Born-Oppenheimer (non-BO) wave functions. A numerical examination was performed with the highly accurate non-BO vibronic wave functions of hydrogen molecular ion, which were obtained in our previous studies with the free complement method. The reduced density function integrated over the electron coordinates plays an important role in understanding nuclear motion dynamics, since it corresponds to the wave function density of the vibrational and rotational motions. The maximum positions of this density indicate the high existence probability of nuclei and can be considered as a discrete representation of the PEC. Whereas an ordinary PEC with the BO approximation is obtained as a numeric curve after multiple electronic state calculations at fixed nuclear coordinates, we propose a new analytical expression of the PEC from a non-BO wave function. PMID:23968070

Nakashima, Hiroyuki; Nakatsuji, Hiroshi

2013-08-21

140

Accurate conformation-dependent molecular electrostatic potentials for high-throughput in silico drug discovery.  

PubMed

The atom-centered partial charges-approximation is commonly used in current molecular modeling tools as a computationally inexpensive alternative to quantum mechanics for modeling electrostatics. Even today, the use of partial charges remains useful despite significant advances in improving the efficiency of ab initio methods. Here, we report on new parameters for the EEM and SFKEEM electronegativity equalization-based methods for rapidly determining partial charges that will accurately model the electrostatic potential of flexible molecules. The developed parameters cover most pharmaceutically relevant chemistries, and charges obtained using these parameters reproduce the B3LYP/cc-pVTZ reference electrostatic potential of a set of FDA-approved drug molecules at best to an average accuracy of 13 +/- 4 kJ mol(-1); thus, equipped with these parameters electronegativity equalization-based methods rival the current best non-quantum mechanical methods, such as AM1-BCC, in accuracy, yet incur a lower computational cost. Software implementations of EEM and SFKEEM, including the developed parameters, are included in the conformer-generation tool BALLOON, available free of charge at http://web.abo.fi/fak/mnf/bkf/research/johnson/software.php. PMID:20020481

Puranen, J Santeri; Vainio, Mikko J; Johnson, Mark S

2010-06-01

141

Molecular weight fractionation of poly(methyl methacrylate) using Gas AntiSolvent techniques  

Microsoft Academic Search

The solubility of poly(methyl methacrylate) in acetone, expanded by carbon dioxide, was studied at 20 °C for a variety of molecular weights and architectures. The suitability of the Gas Anti-Solvent method for fractionation of poly(methyl methacrylate) was investigated with positive results. The threshold pressure for precipitation of various monodisperse molecular weights was investigated, and the effectiveness of this technique to

Emma M. Coen; John F. Quinn; Fariba Dehghani; Neil R. Foster; Thomas P. Davis

2003-01-01

142

Low-molecular-weight heparin during instability in coronary artery disease  

Microsoft Academic Search

SummaryBackground Intravenous heparin is at least as effective as aspirin in preventing new cardiac events after an episode of unstable coronary artery disease (CAD), though the benefits are short-lived. Low-molecular-weight heparin has similar antithrombotic properties but can be given subcutaneously and is therefore suitable for long-term treatment. We have investigated whether subcutaneous low-molecular-weight heparin, in addition to aspirin and antianginal

1996-01-01

143

Pharmacokinetic Profile of a Low-Molecular Weight Heparin (Reviparin) in Pregnant Patients  

Microsoft Academic Search

Anticoagulant therapy during pregnancy is problematic. Patients are frequently treated with long-term low-molecular weight heparin despite a lack of evidence for its effectiveness, and in the absence of validated dosing recommendations. The objectives of this investigation were to characterize the safety and pharmacokinetic behavior of a low-molecular weight heparin (reviparin) administered throughout pregnancy. Forty-two patients followed in a tertiary-care rheumatology

Mark A Crowther; Karen Spitzer; Jim Julian; Jeff Ginsberg; Marilyn Johnston; Roberta Crowther; Carl Laskin

2000-01-01

144

Corner rounding in EUV photoresist: tuning through molecular weight, PAG size, and development time  

SciTech Connect

In this paper, the corner rounding bias of a commercially available extreme ultraviolet photoresist is monitored as molecular weight, photoacid generator (PAG) size, and development time are varied. These experiments show that PAG size influences corner biasing while molecular weight and development time do not. Large PAGs are shown to exhibit less corner biasing, and in some cases, lower corner rounding, than small PAGs. In addition, heavier resist polymers are shown to exhibit less corner rounding than lighter ones.

Anderson, Christopher; Daggett, Joe; Naulleau, Patrick

2009-12-31

145

Effectiveness and safety of bemiparin versus low-molecular weight heparins in orthopaedic surgery  

Microsoft Academic Search

Objective: To evaluate the effectiveness and safety of bemiparin in the prophylaxis of thromboembolism in orthopaedic surgery with respect to other low-molecular-weight heparins.Methods: A meta-analysis of effectiveness and safety of low-molecular weight heparins versus standard heparin in orthopaedic surgery was performed. A literature search was done of Medline and Excerpta Medica from 1988 to 1998 . Only controlled clinical trials

R. Ferriols-Lisart; F. Ferriols-Lisart; V. Jimnez-Torres

2002-01-01

146

Effects of molecular weight on permeability and microstructure of mixed ethyl-hydroxypropyl-cellulose films.  

PubMed

Films of ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC) can be used for extended release coatings in oral formulations. The permeability and microstructure of free EC/HPC films with 30% w/w HPC were studied to investigate effects of EC molecular weight. Phase separation during film spraying and subsequent HPC leaching after immersion in aqueous media cause pore formation in such films. It was found that sprayed films were porous throughout the bulk of the films after water immersion. The molecular weight affected HPC leaching, pore morphology and film permeability; increasing the molecular weight resulted in decreasing permeability. A model to distinguish the major factors contributing to diffusion retardation in porous films showed that the trend in permeability was determined predominantly by factors associated with the geometry and arrangement of pores, independent of the diffusing species. The film with the highest molecular weight did, however, show an additional contribution from pore wall/permeant interactions. In addition, rapid drying and increasing molecular weight resulted in smaller pores, which suggest that phase separation kinetics affects the final microstructure of EC/HPC films. Thus, the molecular weight influences the microstructural features of pores, which are crucial for mass transport in EC/HPC films. PMID:23159668

Andersson, Helene; Hjärtstam, Johan; Stading, Mats; von Corswant, Christian; Larsson, Anette

2013-01-23

147

Molecular weight dependent vertical composition profiles of PCDTBT:PC71BM blends for organic photovoltaics  

PubMed Central

We have used Soxhlet solvent purification to fractionate a broad molecular weight distribution of the polycarbazole polymer PCDTBT into three lower polydispersity molecular weight fractions. Organic photovoltaic devices were made using a blend of the fullerene acceptor PC71BM with the molecular weight fractions. An average power conversion efficiency of 5.89% (peak efficiency of 6.15%) was measured for PCDTBT blend devices with a number average molecular weight of Mn = 25.5?kDa. There was significant variation between the molecular weight fractions with low (Mn = 15.0?kDa) and high (Mn = 34.9?kDa) fractions producing devices with average efficiencies of 5.02% and 3.70% respectively. Neutron reflectivity measurements on these polymer:PC71BM blend layers showed that larger molecular weights leads to an increase in the polymer enrichment layer thickness at the anode interface, this improves efficiency up to a limiting point where the polymer solubility causes a reduction of the PCDTBT concentration in the active layer. PMID:24924096

Kingsley, James W.; Marchisio, Pier Paolo; Yi, Hunan; Iraqi, Ahmed; Kinane, Christy J.; Langridge, Sean; Thompson, Richard L.; Cadby, Ashley J.; Pearson, Andrew J.; Lidzey, David G.; Jones, Richard A. L.; Parnell, Andrew J.

2014-01-01

148

Molecular weight dependent vertical composition profiles of PCDTBT:PC71BM blends for organic photovoltaics  

NASA Astrophysics Data System (ADS)

We have used Soxhlet solvent purification to fractionate a broad molecular weight distribution of the polycarbazole polymer PCDTBT into three lower polydispersity molecular weight fractions. Organic photovoltaic devices were made using a blend of the fullerene acceptor PC71BM with the molecular weight fractions. An average power conversion efficiency of 5.89% (peak efficiency of 6.15%) was measured for PCDTBT blend devices with a number average molecular weight of Mn = 25.5 kDa. There was significant variation between the molecular weight fractions with low (Mn = 15.0 kDa) and high (Mn = 34.9 kDa) fractions producing devices with average efficiencies of 5.02% and 3.70% respectively. Neutron reflectivity measurements on these polymer:PC71BM blend layers showed that larger molecular weights leads to an increase in the polymer enrichment layer thickness at the anode interface, this improves efficiency up to a limiting point where the polymer solubility causes a reduction of the PCDTBT concentration in the active layer.

Kingsley, James W.; Marchisio, Pier Paolo; Yi, Hunan; Iraqi, Ahmed; Kinane, Christy J.; Langridge, Sean; Thompson, Richard L.; Cadby, Ashley J.; Pearson, Andrew J.; Lidzey, David G.; Jones, Richard A. L.; Parnell, Andrew J.

2014-06-01

149

Preparation of polysaccharides in different molecular weights from Ulva pertusa Kjellm (Chorophyta)  

NASA Astrophysics Data System (ADS)

As molecular weight controls the biological activities of polysaccharides, screening the optimal molecular weight of polysaccharides is important in drug research and application. In this study, hydrogen peroxide was employed as oxidant, and temperature, reaction time, and concentration of polysaccharides and hydrogen peroxide were examined for their effects on the preparation of polysaccharides in different molecular weights from Ulva pertusa. Our experiment suggested that the optimal degradation concentrations for polysaccharides and hydrogen peroxide were 2.5% (w/v) and 8.0% (v/v), respectively. The range of degradation measured by relative viscosity was mainly controlled by temperature and time. Results revealed that 35°C was the optimal temperature for obtaining low-degradation samples, and 50°C was the most favorable temperature to accelerate the reaction to yield highly-degraded samples. Four samples in different molecular weights A, B, C and D were finally prepared. The controllability was evaluated by the relative standard deviation (RSD) of relative viscosity, and the peak molecular weights and the polydispersity indexes (Mw/Mn) of molecular weights were measured by high performance gel permeation chromatography (HPGPC).

Yu, Pengzhan; Zhang, Quanbin; Zhang, Hong; Niu, Xizhen; Li, Zhien

2004-12-01

150

RICE STARCH AMYLOPECTIN, AND AMYLOSE: MOLECULAR WEIGHT AND SOLUBILITY IN DIMETHYL SULFOXIDE-BASED SOLVENTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dimethyl sulfoxide (DMSO), with either 50 mM LiBr, 10% water or both, was used as solvent for multi-angle laser-light scattering (MALLS) batch mode analysis of rice starch, and amylopectin and amylose weight-average molecular weight (Mw). DMSO/50 mM LiBr was a better solvent for these measurements ...

151

Low molecular weight heparin as an adjunct to thrombolysis for acute myocardial infarction: the FATIMA study  

Microsoft Academic Search

ObjectiveTo investigate the feasibility of fixed dose, weight adjusted subcutaneous low molecular weight heparin (LMWH), with monitoring of anti-Xa levels and assessment of coronary patency rates after three to five days, thereby giving an initial indication of its safety and efficacy.DesignIn 30 patients with acute myocardial infarction, LMWH (nadroparine) was given as a body weight adjusted intravenous bolus with thrombolysis

S. A. J. Chamuleau; R J de Winter; M. M. Levi; R. Adams; H. R. Buller; M. H. Prins; K. I. Lie; R. J. G. Peters

1998-01-01

152

Effect of Molecular Weight of Surfactant in Nano Ceria Slurry on Shallow Trench Isolation Chemical Mechanical Polishing (CMP)  

NASA Astrophysics Data System (ADS)

We examined the effect of the molecular weight of surfactants in ceria slurry during chemical mechanical polishing (CMP) for shallow trench isolation (STI). We found that for a surfactant with a higher molecular weight, the oxide removal rate decreased drastically as the surfactant concentration increased, but in the case of a lower molecular weight, it only slightly decreased. In addition, slurries whose surfactants had lower molecular weights maintained a higher nitride removal rate with increasing surfactant concentration. The results showed that the molecular weight and surfactant concentration have complex effects on the oxide removal rate and the oxide-to-nitride removal selectivity.

Kang, Hyun-Goo; Katoh, Takeo; Lee, Myung-Yoon; Park, Hyung-Soon; Paik, Ungyu; Park, Jea-Gun

2004-08-01

153

Molecular-weight dependent thermal diusion in dilute polymer solutions Alois Wrger  

E-print Network

Molecular-weight dependent thermal di¤usion in dilute polymer solutions Alois Würger Centre de-, 82.70.-y, 82.20.-w Introduction. Di¤usion in dilute polymer solutions de- pends strongly Talence, France Thermal di¤usion of high polymers in a continous medium is independent of the molecular

Boyer, Edmond

154

Molecular weight determination from light scattering and refraction in solutions. A new and coherent theoretical equation  

Microsoft Academic Search

The classical theoretical equation allowing for the determination of the solute's molecular weight (M2) from light scattering (LS) and refractive measurements in diluted solutions is reexamined. Serious theoretical and practical defects in its derivation and application are pointed out, especially about the refraction increment dndc. A new theoretical equation is deduced from a more consistent application of the basic molecular

M. Herail; M. Le Guennec; D. Le Goff; A. Proutière

1996-01-01

155

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

Microsoft Academic Search

Crosslinking has been shown to improve the wear resistance of ultra-high molecular weight polyethylene in both in vitro and clinical in vivo studies. The molecular mechanisms and material properties that are responsible for this marked improvement in wear resistance are still not well understood. In fact, following crosslinking a number of mechanical properties of UHMWPE are decreased including toughness, modulus,

Orhun K. Muratoglu; Charles R. Bragdon; Daniel O. O’Connor; Murali Jasty; William H. Harris; Rizwan Gul; Fred McGarry

1999-01-01

156

Synthesis of the low molecular weight heat shock proteins in plants  

Microsoft Academic Search

Heat shock of living tissue induces the synthesis of a unique group of proteins, the heat shock proteins. In plants, the major group of heat shock proteins has a molecular mass of 15 to 25 kilodaltons. Accumulation to these proteins to stainable levels has been reported in only a few species. To examine accumulation of the low molecular weight heat

M. A. Mansfield; J. L. Key

1987-01-01

157

Tailoring a low-molecular weight protein tyrosine phosphatase into an efficient reporting protein  

SciTech Connect

Fusion reporter methods are important tools for biology and biotechnology. An ideal reporter protein in a fusion system should have little effects on its fusion partner and provide an easy and accurate readout. Therefore, a small monomeric protein with high activity for detection assays often has advantages as a reporter protein. For this purpose, we have tailored the human B-form low-molecular-weight phosphotyrosyl phosphatase (HPTP-B) to increase its general applicability as a potent reporter protein. With the aim to eliminate interference from cysteine residues in the native HPTP-B, combined with a systematic survey of N- and C-terminal truncated variants, a series of cysteine to serine mutations were introduced, which allowed isolation of an engineered soluble protein with suitable biophysical properties. When we deleted both the first six residues and the last two residues, we still obtained a soluble mutant protein with correct folding and similar activity with wild-type protein. This mutant with two cysteine to serine mutations, HPTP-B{sup N{sub {Delta}}6-C{sub {Delta}}2-C90S-C109S}, has good potential as an optimal reporter.

Liu, Xiao-Yan; Li, Lan-Fen [The National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Science, Peking University, Beijing 100871 (China)] [The National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Science, Peking University, Beijing 100871 (China); Su, Xiao-Dong, E-mail: xdsu@pku.edu.cn [The National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Science, Peking University, Beijing 100871 (China) [The National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Science, Peking University, Beijing 100871 (China); Shenzhen Graduate School of Peking University, Shenzhen 518055 (China)

2009-05-15

158

Determination of molecular weights of humic substances by analytical (UV scanning) ultracentrifugation  

NASA Astrophysics Data System (ADS)

Samples of peat humic acid (PHA) and surface water humic (WBHA) and fulvic (WBFA) acids have been extracted from Whitray Beck in North Yorkshire, U.K. The molecular weights of the extracts have been investigated by sedimentation equilibrium using an analytical ultracentrifuge equipped with a UV scanning system. The system allows measurements to be made at low concentrations of humic substances, comparable to those existing in natural humic-rich water. A method is described for correcting UV scanning data for changes in the optical properties of the materials with changing molecular weight. Measurements have also been made on reference samples of Suwannee river humic (SRHA) and fulvic (SRFA) acids from the International Humic Substances Society (IHSS). The weight-average molecular weights of the extracted samples range from approximately 2000 to 17000 and follow a series PHA > WBHA > WBFA. Apparent specific volumes of these materials were in a range from 0.45 to 0.58 cm 3 g -1 as measured by digital densimetry. All the samples studied were analysed by gel filtration, but the molecular weights determined by this method based on a globular protein calibration are not in good accord with the absolute determinations by the sedimentation-equilibrium technique. The molecular weight of the SRHA determined by sedimentation equilibrium is in good agreement with that reported by BECKETT (1987) et al., based on flow field-flow fractionation.

Reid, Patrick M.; Wilkinson, Alan E.; Tipping, Edward; Jones, Malcolm N.

1990-01-01

159

Profiling of the Molecular Weight and Structural Isomer Abundance of Macroalgae-Derived Phlorotannins  

PubMed Central

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

Heffernan, Natalie; Brunton, Nigel P.; FitzGerald, Richard J.; Smyth, Thomas J.

2015-01-01

160

Profiling of the molecular weight and structural isomer abundance of macroalgae-derived phlorotannins.  

PubMed

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

Heffernan, Natalie; Brunton, Nigel P; FitzGerald, Richard J; Smyth, Thomas J

2015-01-01

161

Adsorption of dissolved organics in lake water by aluminum oxide. Effect of molecular weight  

USGS Publications Warehouse

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.

Davis, J.A.; Gloor, R.

1981-01-01

162

The Role of Molecular Weight and Temperature on the Elastic and Viscoelastic Properties of a Glassy Thermoplastic Polyimide  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

163

Accurate physical laws can permit new standard units: The two laws F?=ma? and the proportionality of weight to mass  

NASA Astrophysics Data System (ADS)

Three common approaches to F?=ma? are: (1) as an exactly true definition of force F? in terms of measured inertial mass m and measured acceleration a?; (2) as an exactly true axiom relating measured values of a?, F? and m; and (3) as an imperfect but accurately true physical law relating measured a? to measured F?, with m an experimentally determined, matter-dependent constant, in the spirit of the resistance R in Ohm's law. In the third case, the natural units are those of a? and F?, where a? is normally specified using distance and time as standard units, and F? from a spring scale as a standard unit; thus mass units are derived from force, distance, and time units such as newtons, meters, and seconds. The present work develops the third approach when one includes a second physical law (again, imperfect but accurate)—that balance-scale weight W is proportional to m—and the fact that balance-scale measurements of relative weight are more accurate than those of absolute force. When distance and time also are more accurately measurable than absolute force, this second physical law permits a shift to standards of mass, distance, and time units, such as kilograms, meters, and seconds, with the unit of force—the newton—a derived unit. However, were force and distance more accurately measurable than time (e.g., time measured with an hourglass), this second physical law would permit a shift to standards of force, mass, and distance units such as newtons, kilograms, and meters, with the unit of time—the second—a derived unit. Therefore, the choice of the most accurate standard units depends both on what is most accurately measurable and on the accuracy of physical law.

Saslow, Wayne M.

2014-04-01

164

Determination of molecular weights of humic substances by analytical (UV scanning) ultracentrifugation  

SciTech Connect

Samples of peat humic acid (PHA) and surface water humic (WBHA) and fulvic (WBFA) acids have been extracted from Whitray Beck in North Yorkshire, U.K. The molecular weights of the extracts have been investigated by sedimentation equilibrium using an analytical ultracentrifuge equipped with a UV scanning system. The system allows measurements to be made at low concentrations of humic substances, comparable to those existing in natural humic-rich water. A method is described for correcting UV scanning data for changes in the optical properties of the materials with changing molecular weight. Measurements have also been made on reference samples of Suwannee river humic (SRHA) and fulvic (SRFA) acids from the International Humic Substances Society (IHSS). The weight-average moleuclar weights of the extracted samples range from approximately 2,000 to 17,000 and follow a series PHA > WBHA > WBFA. Apparent specific volumes of these materials were in a range from 0.45 to 0.58 cm{sup 3} g{sup {minus}1} as measured by digital densimetry. Al the samples studied were analysed by gel filtration, but the molecular weights determined by this method based on a globular protein calibration are not in good accord with the absolute determinations by the sedimentation-equilibrium technique. The molecular weight of the SRHA determined by sedimentation equilibrium is in good agreement with that reported by BECKETT (1987) et al., based on flow field-flow fractionation.

Reid, P.M.; Wilkinson, A.E.; Tipping, E.; Jones, M.N. (Univ. of Manchester (England) Freshwater Biological Association, Ambleside, Cumbria (England))

1990-01-01

165

Antibody response to low-molecular-weight antigens of Aspergillus fumigatus in allergic bronchopulmonary aspergillosis.  

PubMed

Sera from patients with allergic bronchopulmonary aspergillosis (ABPA) or aspergilloma and normal sera were analyzed for specific antibodies by Western (immuno-) blotting with Aspergillus fumigatus antigens transferred electrophoretically onto polyvinylidene difluoride membranes. Western blot analysis demonstrated consistent reactivity of low-molecular-weight A. fumigatus antigens against ABPA sera but not against uncomplicated aspergilloma or normal sera. None of these low-molecular-weight components had any lectin-binding activity. Sera from patients with aspergilloma, however, frequently reacted with high-molecular-weight components of A. fumigatus. The majority of these high-molecular-weight antigenic components demonstrated concanavalin A-binding activity. The low-molecular-weight bands were discernible in Western blots with sera from all ABPA patients irrespective of disease activities, such as relapse, flare, or treatment. Antibodies detected by methods such as immunodiffusion or enzyme-linked immunosorbent assays demonstrated total antibody responses to most or all antigenic components, while Western blots demonstrated the reactivities of the individual components with the specific antibodies. Western blot analysis thus provided more information for immunodiagnosis of ABPA than other methods, especially when only crude antigens were available. PMID:2666440

Kurup, V P; Greenberger, P A; Fink, J N

1989-06-01

166

Anti-aging effects of high molecular weight proteoglycan from salmon nasal cartilage in hairless mice.  

PubMed

Proteoglycans comprise a family of complex macromolecules consisting of a core protein with covalently attached glycosaminoglycan (GAG) chains. The skin anti-aging effects of oral administration of proteoglycan fractions with different molecular weights from salmon nasal cartilage were investigated in a hairless mouse model of skin aging; aging was caused by repeated ultraviolet B (UVB) irradiation. Three proteoglycan fractions of different molecular weights were prepared from salmon nasal cartilage water extract by ion-exchange column chromatography and gel filtration column chromatography. Physiological and histological analysis of the skin indicated that oral administration of high molecular weight proteoglycan inhibited UVB-induced skin aging, defined as increased erythema, increased transepidermal water loss (TEWL), decreased hydration, and epidermal and dermal hypertrophies. The serum and dorsal skin inflammatory cytokine levels indicated that high molecular weight proteoglycan acts on gut immunity and improves skin by inhibiting surplus inflammatory cytokines produced by UVB irradiation. These results suggest that high molecular weight proteoglycan from salmon nasal cartilage is effective in preventing skin aging. PMID:22367383

Goto, Masashi; Yamazaki, Shota; Kato, Yoji; Yamamoto, Kazushi; Katagata, Yohtaro

2012-05-01

167

Low molecular weight protamine as nontoxic heparin\\/low molecular weight heparin antidote (III): Preliminary in vivo evaluation of efficacy and toxicity using a canine model  

Microsoft Academic Search

Heparin employed in cardiovascular surgeries often leads to a high incidence of bleeding complications. Protamine employed\\u000a in heparin reversal, however, can cause severe adverse reactions. In an attempt to address this clinical problem, we developed\\u000a low molecular weight protamine (LMWP) as a potentially effective and less toxic heparin antagonist. A homogeneous 1880-d peptide\\u000a fragment, termed LMWP-TDSP5 and containing the amino

Li-Chien Chang; Shirley Wrobleski; Thomas W. Wakefield; Lai Ming Lee; Victor C. Yang

2001-01-01

168

Molecular weight of DNA from four entomopoxviruses determined by electron microscopy.  

PubMed

DNA was isolated from entomopoxviruses infected Amsacta moorei and Euxoa auxiliaris (Lepidoptera), Goeldichironomus holoprasinus (Diptera), and Othnonius batesi (Coleoptera) and compared with vertebrate virus DNA (vaccinia). After incubation in Pronase, sodium lauryl sulfate, and deoxycholate, poxvirus preparations shadowed with platinum and palladium revealed subcore particles 45 to 60 nm in diameter. Continued incubation in Pronase resulted in the gradual release of DNA from the particles. Metal-shadowed DNA molecules were photographed in the electron microscope and measured, and the average molecular weights were calculated. Lepidopteran poxvirus DNA (135 X 10(6)) was approximately equal to vaccinia DNA (131.7 X 10(6)) in molecular weight. The molecular weight of dipteran and coleopteran poxvirus DNA (200 X 10(6) to 251 X 10(6)) was approximately 50% greater than vaccinia DNA. Based on the concentration of DNA and protein per virion, Amsacta entomopoxvirus contained 5.7 to 7.7% DNA. PMID:833926

Langridge, W H; Roberts, D W

1977-01-01

169

Molecular weight of DNA from four entomopoxviruses determined by electron microscopy.  

PubMed Central

DNA was isolated from entomopoxviruses infected Amsacta moorei and Euxoa auxiliaris (Lepidoptera), Goeldichironomus holoprasinus (Diptera), and Othnonius batesi (Coleoptera) and compared with vertebrate virus DNA (vaccinia). After incubation in Pronase, sodium lauryl sulfate, and deoxycholate, poxvirus preparations shadowed with platinum and palladium revealed subcore particles 45 to 60 nm in diameter. Continued incubation in Pronase resulted in the gradual release of DNA from the particles. Metal-shadowed DNA molecules were photographed in the electron microscope and measured, and the average molecular weights were calculated. Lepidopteran poxvirus DNA (135 X 10(6)) was approximately equal to vaccinia DNA (131.7 X 10(6)) in molecular weight. The molecular weight of dipteran and coleopteran poxvirus DNA (200 X 10(6) to 251 X 10(6)) was approximately 50% greater than vaccinia DNA. Based on the concentration of DNA and protein per virion, Amsacta entomopoxvirus contained 5.7 to 7.7% DNA. Images PMID:833926

Langridge, W H; Roberts, D W

1977-01-01

170

The development of low-molecular weight hydrogels for applications in cancer therapy  

NASA Astrophysics Data System (ADS)

To improve the anti-cancer efficacy and to counteract the side effects of chemotherapy, a variety of drug delivery systems have been invented in past decades, but few of these systems have succeeded in clinical trials due to their respective inherent shortcomings. Recently, low-molecular weight hydrogels of peptides that self-assemble via non-covalent interactions have attracted considerable attention due to their good biocompatibility, low toxicity, inherent biodegradability as well as their convenience of design. Low-molecular weight hydrogels have already shown promise in biomedical applications as diverse as 3D-cell culture, enzyme immobilization, controllable MSC differentiation, wound healing, drug delivery etc. Here we review the recent development in the use of low-molecular weight hydrogels for cancer therapy, which may be helpful in the design of soft materials for drug delivery.

Tian, Ran; Chen, Jin; Niu, Runfang

2014-03-01

171

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

SciTech Connect

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. The authors 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 M{sub n} and M{sub 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.

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

2000-03-15

172

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

PubMed

Low molecular weight phenols of Tannat red wines produced by Traditional Maceration (TM), Prefermentative Cold Maceration (PCM), Maceration Enzyme (ENZ) and grape-Seed Tannins additions (ST), were performed and discussed. Alternatives to TM increased wine phenolic contents but unequally, ST increased mainly smaller flavans-3-ol, PCM anthocyanins and ENZ proanthocyanidins (up to 2250 mg/L). However low molecular weight flavan-3-ols remained below 9 mg/L in all wines, showing that there is not necessarily a correspondence between wine richness in total tannins and flavan-3-ols contents at low molecular weight. PCM wines had particularly high concentrations of tyrosol and tryptophol, yeast metabolism derived compounds. The use of grape-seed enological tannins did not increase grape seed derived phenolic compounds such as gallic acid. Caftaric acid was found in concentrations much higher than those reported in other grape varieties. Wine phenolic content and composition was considerably affected by the winemaking procedures tested. PMID:24731376

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

2014-09-01

173

Intermolecular disulfide bonds link specific high-molecular-weight glutenin subunits in wheat endosperm.  

PubMed

A detergent wash extracted soluble proteins from wheat flour, leaving a residue enriched with insoluble glutenin aggregates. Digestion of this residue with endoproteinase Lys-C, which showed a limited specificity for glutenin subunits, produced several peptides with apparent molecular weights close to those of intact high-molecular-weight glutenin subunits. N-terminal sequencing indicated that the isolated peptides were composed of high-molecular-weight glutenin subunit fragments joined by an intermolecular disulfide bond. In two of these peptides, only two components were found, one from an x-type subunit and the other from a y-type subunit. The isolated peptides all contained at least one x-type C-terminal region and one y-type N-terminal region, suggesting a specific orientation to the intermolecular disulfide linkage. PMID:1390908

Tao, H P; Adalsteins, A E; Kasarda, D D

1992-09-01

174

Pharmacological effects and clinical applications of ultra low molecular weight heparins.  

PubMed

Heparin, one of the common anticoagulants, is clinically used to prevent and treat venous thromboembolism (VTE). Though it has been the drug of choice for many advanced medical and surgical procedures with a long history, the adverse events, such as bleeding, heparin-induced thrombocytopenia (HIT), allergic reactions, follow. Therefore, low molecular weight heparins (LMWHs) and ultra low molecular weight heparins (ULMWHs), with lower molecular weights, higher anti-FXa activity, longer half-life times and lower incidence of adverse events than unfractionated heparin (UFH), were researched and developed. Fondaparinux, a chemically synthesized ULMWH of pentasaccharide, has the same antithrombin III (AT-III)-binding sequence as found in UFH and LMWH. In addition, AVE5026 and RO-14, another two ULMWHs, are obtained by selective chemical depolymerization. In this paper, we review the preparation process, pharmacological effects and clinical applications of fondaparinux, AVE5026 and RO-14. PMID:24647152

Liu, Zhang; Ji, Shengli; Sheng, Juzheng; Wang, Fengshan

2014-02-01

175

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

Microsoft Academic Search

A rigorous mathematical expression for the dependence of colligative properties on acid dissociation of water soluble humic substances is presented. New data for number average molecular weights of a river derived humic material and its gel permeation Chromatographic fractions are compared with values obtained by a reevaluation of previously published experimental observations on soil and water fulvic acids. The results

J. H. Reuter; E. M. Perdue

1981-01-01

176

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

USGS Publications Warehouse

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.

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

2000-01-01

177

Molecular weight of barley ?-glucan does not influence satiety or energy intake in healthy male subjects.  

PubMed

Previous studies have shown the ability of high molecular weight barley ?-glucan with increased viscosity to attenuate glycemic response, gastric emptying and in vitro starch digestion. The main objective of this study was to investigate the effect of molecular weight of barley ?-glucan in a semisolid meal on energy intake and subjective feelings of hunger, fullness, desire to eat and prospective food consumption in healthy male subjects. In a randomised, controlled, crossover trial, 23 healthy male subjects (BMI 24.2?±?2.5?kg/m(2)) tested soups equivalent to 25?g available carbohydrate containing high or low molecular weight barley ?-glucan (~3?g) as preload after a standard breakfast. The viscosity of soup with high molecular weight ?-glucan was 350?Pa·s whereas the soup with low molecular weight ?-glucan had a viscosity of 100?Pa·s. Appetite ratings before and for two hours after consumption of ?-glucan soups and subsequent ad libitum energy intake at lunch were recorded and compared with a control soup with no ?-glucan. There was no significant difference in food intake at the ad libitum meal or for the remainder of the day following consumption of the three test foods (p?>?0.05). Similarly, there were no significant differences (p?>?0.05) in hunger, fullness, desire to eat or prospective food consumption following ?-glucan soups. The current study provides evidence that the molecular weight of barley ?-glucan may not impact on perceived feelings of hunger or food intake at the current dose and viscosity. PMID:25106092

Clegg, Miriam E; Thondre, Pariyarath S

2014-12-01

178

Absolute molecular weight determination of hypromellose acetate succinate by size exclusion chromatography: use of a multi angle laser light scattering detector and a mixed solvent.  

PubMed

Molecular weight distribution is an important quality attribute for hypromellose acetate succinate (HPMCAS), a pharmaceutical excipient used in spray-dried dispersions. Our previous study showed that neither relative nor universal calibration method of size exclusion chromatography (SEC) works for HPMCAS polymers. We here report our effort to develop a SEC method using a mass sensitive multi angle laser light scattering detector (MALLS) to determine molecular weight distributions of HPMCAS polymers. A solvent screen study reveals that a mixed solvent (60:40%, v/v 50mM NaH(2)PO(4) with 0.1M NaNO(3) buffer: acetonitrile, pH* 8.0) is the best for HPMCAS-LF and MF sub-classes. Use of a mixed solvent creates a challenging condition for the method that uses refractive index detector. Therefore, we thoroughly evaluated the method performance and robustness. The mean weight average molecular weight of a polyethylene oxide standard has a 95% confidence interval of (28,443-28,793) g/mol vs. 28,700g/mol from the Certificate of Analysis. The relative standard deviations of average molecular weights for all polymers are 3-6%. These results and the Design of Experiments study demonstrate that the method is accurate and robust. PMID:21840663

Chen, Raymond; Ilasi, Nicholas; Sekulic, Sonja S

2011-12-01

179

The Combined Influence of Molecular Weight and Temperature on the Aging and Viscoelastic Response of a Glassy Thermoplastic Polyimide  

NASA Technical Reports Server (NTRS)

The effect of molecular weight on the viscoelastic performance of an advanced polymer (LaRC-SI) was investigated through the use of creep compliance tests. Testing consisted of short-term isothermal creep and recovery with the creep segments performed under constant load. The tests were conducted at three temperatures below the glass transition temperature of five materials of different molecular weight. Through the use of time-aging-time superposition procedures, the material constants, material master curves and aging-related parameters were evaluated at each temperature for a given molecular weight. The time-temperature superposition technique helped to describe the effect of temperature on the timescale of the viscoelastic response of each molecular weight. It was shown that the low molecular weight materials have higher creep compliance and creep rate, and are more sensitive to temperature than the high molecular weight materials. Furthermore, a critical molecular weight transition was observed to occur at a weight-average molecular weight of M (bar) (sub w) 25000 g/mol below which, the temperature sensitivity of the time-temperature superposition shift factor increases rapidly. The short-term creep compliance data were used in association with Struik's effective time theory to predict the long-term creep compliance behavior for the different molecular weights. At long timescales, physical aging serves to significantly decrease the creep compliance and creep rate of all the materials tested.

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

2000-01-01

180

Thermal response of low molecular weight poly-( N -isopropylacrylamide) polymers in aqueous solution  

Microsoft Academic Search

Temperature-induced phase transition of three low-molecular-weight samples (M\\u000a w\\u000a  4) of poly(N-isopropylacrylamide) was studied with the aid of turbidimetry, dynamic light scattering, and rheology. We have demonstrated\\u000a that the lower critical solution temperature depends on the length of the chain and the concentration of the polymer in the\\u000a low molecular weight range. The turbidity results show a transition peak in

Ramón Pamies; Kaizheng Zhu; Anna-Lena Kjøniksen; Bo Nyström

2009-01-01

181

Formulation/cure technology for ultrahigh molecular weight silphenylene-siloxane polymers  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

182

Low molecular weight thermostable {beta}-D-glucosidase from Acidothermus cellulolyticus  

DOEpatents

A purified low molecular weight {beta}-D-glucosidase is produced from Acidothermus cellulolyticus ATCC 43068. The enzyme is water soluble, possesses activity against pNP-{beta}-D-glucopyranoside, has a high of degree of stability toward heat, exhibits optimal temperature activity at about 65 C at a pH range of from about 2 to about 7, has an inactivation temperature of about 80 C at a pH range of from about 2 to about 7 and has a molecular weight of about 50.5--54.5 kD as determined by SDS-PAGE. 6 figs.

Himmel, M.E.; Tucker, M.P.; Adney, W.S.; Nieves, R.A.

1995-07-11

183

Different cleavage site for high molecular weight kininogen in vivo following intravenous injection of dextran sulfate in the rabbit  

SciTech Connect

Purified radiolabeled rabbit Hageman factor, prekallikrein, and high molecular weight kininogen were used to examine Hageman factor system molecular dynamics after the intravenous injection of heparin-like dextran sulfate polymer in the rabbit. Hageman factor system proteins rapidly disappeared from the circulation following dextran sulfate injection, as measured by radial immunodiffusion, by kaolin-releasable kinin formation, and by measuring circulating levels of radiolabeled Hageman factor, prekallikrein, and high molecular weight kininogen. /sup 125/I-Hageman factor was distributed mainly to lung, liver, and spleen following dextran sulfate injection. Proteolysis of circulating /sup 125/I-Hageman factor occurred at a site within a disulfide loop into fragments of 50,000 and 30,000 molecular weight. Proteolysis of /sup 125/I-prekallikrein also occurred with visualization of a 50,000 molecular weight fragment. Although extensive proteolysis of /sup 131/I-high molecular weight kininogen was observed, the cleavage fragments were not the same as those generated during contact activation in vitro. The major fragment of high molecular weight kininogen observed in vivo was at 80,000 molecular weight, in contrast to the 65,000 molecular weight fragment generated by kallikrein in vitro. These results indicate that high molecular weight kininogen can undergo proteolysis in vivo into fragments not known to be associated with kinin release.

Wiggins, R.C.

1986-04-01

184

Synthesis of the low molecular weight heat shock proteins in plants  

SciTech Connect

Heat shock of living tissue induces the synthesis of a unique group of proteins, the heat shock proteins. In plants, the major group of heat shock proteins has a molecular mass of 15 to 25 kilodaltons. Accumulation to these proteins to stainable levels has been reported in only a few species. To examine accumulation of the low molecular weight heat shock proteins in a broader range of species, two-dimensional electrophoresis was used to resolve total protein from the following species: soybean (Glycine max L. Merr., var Wayne), pea (Pisum sativum L., var Early Alaska), sunflower (Helianthus annuus L.), wheat (Triticum asetivum L.), rice (Oryza sativa L., cv IR-36), maize (Zea mays L.), pearl millet (Pennisetum americanum L. Leeke, line 23DB), and Panicum miliaceum L. When identified by both silver staining and incorporation of radiolabel, a diverse array of low molecular weight heat shock proteins was synthesized in each of these species. These proteins accumulated to significant levels after three hours of heat shock but exhibited considerable heterogeneity in isoelectric point, molecular weight, stainability, and radiolabel incorporation. Although most appeared to be synthesized only during heat shock, some were detectable at low levels in control tissue. Compared to the monocots, a higher proportion of low molecular weight heat shock proteins was detectable in control tissues from dicots.

Mansfield, M.A.; Key, J.L. (Univ., of Georgia, Athens (USA))

1987-08-01

185

Effect of molecular weight on the electrophoretic deposition of carbon black nanoparticles in moderately viscous systems.  

PubMed

Electrophoretic deposition from viscous media has the potential to produce in-mold assembly of nanoparticles onto three-dimensional parts in high-rate, polymer melt-based processes like injection molding. The effects of the media's molecular weight on deposition behavior were investigated using a model system of carbon black and polystyrene in tetrahydrofuran. Increases in molecular weight reduced the electrophoretic deposition of the carbon black particles due to increases in suspension viscosity and preferential adsorption of the longer polystyrene chains on the carbon black particles. At low deposition times (?5 s), only carbon black deposited onto the electrodes, but the deposition decreased with increasing molecular weight and the resultant increases in suspension viscosity. For longer deposition times, polystyrene codeposited with the carbon black, with the amount of polystyrene increasing with molecular weight and decreasing with greater charge on the polystyrene molecules. This deposition behavior suggests that use of lower molecular polymers and control of electrical properties will permit electrophoretic deposition of nanoparticles from polymer melts for high-rate, one-step fabrication of nano-optical devices, biochemical sensors, and nanoelectronics. PMID:23848316

Modi, Satyam; Panwar, Artee; Mead, Joey L; Barry, Carol M F

2013-08-01

186

Synthesis of the low molecular weight heat shock proteins in plants.  

PubMed

Heat shock of living tissue induces the synthesis of a unique group of proteins, the heat shock proteins. In plants, the major group of heat shock proteins has a molecular mass of 15 to 25 kilodaltons. Accumulation of these proteins to stainable levels has been reported in only a few species. To examine accumulation of the low molecular weight heat shock proteins in a broader range of species, two-dimensional electrophoresis was used to resolve total protein from the following species: soybean (Glycine max L. Merr., var Wayne), pea (Pisum sativum L., var Early Alaska), sunflower (Helianthus annuus L.), wheat (Triticum aestivum L.), rice (Oryza sativa L., cv IR-36), maize (Zea mays L.), pearl millet (Pennisetum americanum L. Leeke, line 23DB), and Panicum miliaceum L. When identified by both silver staining and incorporation of radiolabel, a diverse array of low molecular weight heat shock proteins was synthesized in each of these species. These proteins accumulated to significant levels after three hours of heat shock but exhibited considerable heterogeneity in isoelectric point, molecular weight, stainability, and radiolabel incorporation. Although most appeared to be synthesized only during heat shock, some were detectable at low levels in control tissue. Compared to the monocots, a higher proportion of low molecular weight heat shock proteins was detectable in control tissues from dicots. PMID:16665553

Mansfield, M A; Key, J L

1987-08-01

187

Low-molecular-weight inhibitors of NF-?B signalling pathways  

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

188

Effect of cyclic strain on the mechanical behavior of virgin ultra-high molecular weight polyethylene.  

PubMed

Ultra High Molecular Weight Polyethylene (UHMWPE) is a polymeric material employed in critical biomedical applications. Knowledge of its mechanical behavior is essential in order to obtain accurate prediction of stresses and deformations in real components, in particular when cyclic loading is considered. In the present research the effects of alternating and pulsating cyclic strain on the mechanical response of UHMWPE were studied by means of an experimental procedure based on tests carried out in strain control at different mean cyclic strain levels. During the tests the temperature increase due to hysteretic heating was controlled by means of a compressed air cooling apparatus specifically devised. By taking advantage of the possibility to control and stabilize temperature, cyclic steady-state mechanical response was investigated at room temperature and at 37 and 50 °C, comparing the effects of alternating and pulsating loading cycles. A transient thermal analysis using the finite element method (FEM) was also carried out to analyze temperature distribution within the specimen. UHMWPE exhibited cyclic softening as a result of a thermal contribution due to temperature increase and of a mechanical contribution related to the effects of applied load on the microstructure. The material exhibited different peak stress percent reductions for pulsating and alternating loading and during tensile and compressive loading phases. For pulsating tests significant cyclic mean stress relaxation was also observed. Based on the experimental procedure described the cyclic curve was determined as a function of temperature and fitted with a Ramberg-Osgood type constitutive equation, in which material parameters are temperature dependent. In this way the combined effects of temperature rises, such as those that might occur in biological environments or due to frictional heating, and mechanical loads could effectively be taken into account for constitutive modeling purposes of cyclic mechanical behavior of UHMWPE. PMID:21783133

Avanzini, A

2011-10-01

189

Novel High-Molecular Weight Fucosylated Milk Oligosaccharides Identified in Dairy Streams  

PubMed Central

Oligosaccharides are the third largest component in human milk. This abundance is remarkable because oligosaccharides are not digestible by the newborn, and yet they have been conserved and amplified during evolution. In addition to encouraging the growth of a protective microbiota dominated by bifidobacteria, oligosaccharides have anti-infective activity, preventing pathogens from binding to intestinal cells. Although it would be advantageous adding these valuable molecules to infant milk formula, the technologies to reproduce the variety and complexity of human milk oligosaccharides by enzymatic/organic synthesis are not yet mature. Consequently, there is an enormous interest in alternative sources of these valuable oligosaccharides. Recent research has demonstrated that bovine milk and whey permeate also contain oligosaccharides. Thus, a thorough characterization of oligosaccharides in bovine dairy streams is an important step towards fully assessing their specific functionalities. In this study, bovine milk oligosaccharides (BMOs) were concentrated by membrane filtration from a readily available dairy stream called “mother liquor”, and analyzed by high accuracy MALDI FT-ICR mass spectrometry. The combination of HPLC and accurate mass spectrometry allowed the identification of ideal processing conditions leading to the production of Kg amount of BMO enriched powders. Among the BMOs identified, 18 have high-molecular weight and corresponded in size to the most abundant oligosaccharides present in human milk. Notably 6 oligosaccharides contained fucose, a sugar monomer that is highly abundant in human milk, but is rarely observed in bovine milk. This work shows that dairy streams represent a potential source of complex milk oligosaccharides for commercial development of unique dairy ingredients in functional foods that reproduce the benefits of human milk. PMID:24810963

Mehra, Raj; Barile, Daniela; Marotta, Mariarosaria; Lebrilla, Carlito B.; Chu, Caroline; German, J. Bruce

2014-01-01

190

Water activity and mobility in solutions of glycerol and small molecular weight sugars: Implication for cryo- and lyopreservation  

NASA Astrophysics Data System (ADS)

In this study, the free volume models, originally developed for large molecular weight polymer-solvent systems, were used to study the water activity and mobility in solutions of four small molecular weight cryo-/lyoprotectants, viz., glycerol, a monosaccharide (fructose), and two disaccharides (sucrose and trehalose). The free volume model parameters were determined by fitting the models to available experimental data using a nonlinear optimization procedure. It was found that free volume models could accurately predict the available experimental data, which suggests that the free volume models might be generally applicable to aqueous solutions of small molecular weight cryo-/lyoprotectants. Furthermore, several models for estimating the mutual diffusion coefficient were tested using available experimental data for aqueous solutions of glycerol and a better method to estimate the mutual diffusion coefficient was proposed. Free volume models were used to predict and analyze the water activity and mobility in solutions of four cryo-/lyoprotectants under conditions frequently encountered in cryo-/lyopreservation applications. It was found that the water mobility in the glassy state of the above four solutions is essentially negligible in the case of cryopreservation with storage temperature lower than -110°C. However, the water mobility in a glass at higher temperature (>-80°C) may be significant. As a result, a subcooling of up to 50°C may be necessary for the long-term cryo-/lyopreservation of biomaterials depending on the water content and the type of cryo-/lyoprotectants. It was further shown that trehalose might be the best of the four protectants studied for lyopreservation (water mass fraction ?0.1) when the storage temperature is above the room temperature. The results from this study might be useful for the development of more effective protocols for both cryopreservation and lyopreservation of living cells and other biomaterials.

He, Xiaoming; Fowler, Alex; Toner, Mehmet

2006-10-01

191

Accurate description of phase diagram of clathrate hydrates at the molecular level  

Microsoft Academic Search

In order to accurately estimate the thermodynamic properties of hydrogen clathrate hydrates, we developed a method based on the solid solution theory of van der Waals and Platteeuw. This model allows one to take into account the influence of guest molecules on the host lattice and guest-guest interactions-especially when more than one guest molecule occupies a cage. The free energies,

Rodion V. Belosudov; Oleg S. Subbotin; Hiroshi Mizuseki; Yoshiyuki Kawazoe; Vladimir R. Belosludov

2009-01-01

192

The effect of chemical composition and molecular weight of polysaccharide depressants on the flotation of talc  

Microsoft Academic Search

Polysaccharide reagents are frequently used in the mineral processing industry to improve the grade of the concentrate by depressing the naturally floatable gangue. A microflotation study showed that at an ionic strength of 10?3 M KNO3, the dosage, molecular weight, and chemical composition of polysaccharide depressants affect their depressing action on talc. Viscosity readings for four carboxymethylcellulose (CMC) reagents and

P. G. Shortridge; P. J. Harris; D. J. Bradshaw; L. K. Koopal

2000-01-01

193

Synaptic effects of low molecular weight components from Chilean Black Widow spider venom  

Microsoft Academic Search

?-Latrotoxin is the principal component of the venom from the euroasiatic Black Widow spider and has been studied for its pharmacological use as a synaptic modulator. Interestingly, smaller molecular weight fractions have been found to be associated with this toxin, but their cellular actions have not been studied in detail. The venom from the Chilean Black Widow spider (Latrodectus mactans)

Jorge Parodi; Fernando Romero

2008-01-01

194

Low Molecular Weight Fucoidan Prevents Neointimal Hyperplasia in Rabbit Iliac Artery In-Stent Restenosis Model  

Microsoft Academic Search

Objective—Smooth muscle cell (SMC) proliferation within the intima is regulated by heparan sulfates. We studied a low molecular weight (LMW) fucoidan (sulfated polysaccharide from brown seaweed) on SMC proliferation in vitro and intimal hyperplasia in vivo. Methods and Results—In vitro study revealed that LMW fucoidan reduces rabbit SMC proliferation and is internalized in SMC perinuclear vesicles. On rabbit iliac arteries

Jean-François Deux; Anne Meddahi-Pellé; Alain F. Le Blanche; Laurent J. Feldman; Sylvia Colliec-Jouault; Françoise Brée; Frank Boudghène; Jean-Baptiste Michel; Didier Letourneur

195

Flow field-flow fractionation and multiangle light scattering for ultrahigh molecular weight sodium hyaluronate characterization.  

PubMed

This review describes the utility of flow field-flow fractionation coupled with multiangle light scattering and differential refractive index (FlFFF-MALS-DRI) detection methods for the separation of ultrahigh molecular weight sodium hyaluronate (NaHA) materials and for the characterization of molecular weight distribution as well as structural determination. The sodium salt of hyaluronic acid (HA), NaHA, is a water-soluble polysaccharide with a broad range of molecular weights (10(5) -10(8) ) found in various naturally occurring fluids and tissues. Basic principles of FlFFF-MALS using field programming for the separation of the degraded products of NaHA prepared by treating raw materials with depolymerization or degradation processes such as membrane filtration, enzymatic degradation, ultrasonic degradation, alkaline reaction, irradiation by ?-rays, and thermal treatment for the development of pharmaceutical applications are introduced. Changes in molecular weight distribution and conformation of NaHA materials due to external stimuli are also discussed. PMID:20886518

Moon, Myeong Hee

2010-11-01

196

Composition of the Atmosphere Average molecular weight = 28.97 g/mole  

E-print Network

westerlies in SH less pole-ward flow in SH, cold Antarctic atm #12;3-Cell Model (Hadley, Ferrel, and Polar Cells): Circulation in 3 cells controlled by heating at Eq. cooling at poles · Hadley Cell Winds AloftComposition of the Atmosphere Average molecular weight = 28.97 g/mole #12;#12;Global Circulation

Weber, Rodney

197

Improved isolation protocol to detect high molecular weight polysaccharide structures of Campylobacter jejuni.  

PubMed

Simple detection of high molecular weight, LPS-like structures of Campylobacter jejuni is still an unsolved problem. A phenol-free extraction method for the detection of HMW polysaccharide was developed without the need for Western blot. This method provides a reliable technique for large-scale screening and comparative characterization study of different isolates. PMID:25229649

Kovács, Judit K; Fels?, Péter; Em?dy, Levente; Schneider, György; Kocsis, Béla

2014-12-01

198

EVAPORATIVE LIGHT SCATTERING DETECTOR AS A MASS DETECTOR WITH MALLS FOR DETERMINATION OF PECTIN MOLECULAR WEIGHT  

Technology Transfer Automated Retrieval System (TEKTRAN)

A method to calibrate and use an evaporative light scattering detector (ELS) as a mass detector for molecular weight determination of polysaccharides using a multi-angle laser light scattering detector (MALLS) is shown. The calibration of the ELS was performed under isocratic conditions using conce...

199

IMPROVED METHOD FOR ESTIMATING MOLECULAR WEIGHTS OF VOLATILE ORGANIC COMPOUNDS FROM LOW RESOLUTION MASS SPECTRA  

EPA Science Inventory

An improved method of estimating molecular weights of volatile organic compound from their mass spectra has been developed and implemented with an expert system. he method is based on the strong correlation of MAXMASS, the highest mass with an intensity of 5% of the base peak in ...

200

EXPERT SYSTEM FOR ESTIMATING MOLECULAR WEIGHTS OF VOLATILE ORGANIC COMPOUNDS FROM LOW RESOLUTION MASS SPECTRA  

EPA Science Inventory

MAXMASS, the highest mass with an intensity of 5% of the base peak in a low resolution mass spectrum, has been found to be linearly correlated with the true molecular weights of 400 randomly selected spectra, yielding a family of parallel lines. imple exert system using MAXMASS h...

201

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

Microsoft Academic Search

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

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

202

Sedimentation Coefficient, Frictional Coefficient, and Molecular Weight: A Preparative Ultracentrifuge Experiment for the Advanced Undergraduate Laboratory.  

ERIC Educational Resources Information Center

Describes an experiment using a high-speed preparative centrifuge and calculator to demonstrate effects of the frictional coefficient of a macromolecule on its rate of transport in a force field and to estimate molecular weight of the macromolecule using an empirical relationship. Background information, procedures, and discussion of results are…

Halsall, H. B.; Wermeling, J. R.

1982-01-01

203

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

Technology Transfer Automated Retrieval System (TEKTRAN)

A systematic study was performed to demonstrate the impact of methanol (MeOH) on poly(3-hydroxybutyrate) (PHB) synthesis and molecular weight (MW) control. Glycerine (init. conc. = 1.0%; w/v), was used as the primary carbon source in batch-culture fermentations with varying concentrations (0 to 0.85...

204

Bombyx mori L. Ribosomal proteins: Resolution, nomenclature, molecular weights and in vivo phosphorylation  

Microsoft Academic Search

Bombyx mori L. ribosomal proteins have been analyzed by four related two-dimensional polyacrylamide gel electrophoretic systems (Madjar et al. 1977a). In the small and large subunits are present 32 and 45 proteins, respectively, whose numbering is proposed. No significant differences in composition or migration could be detected between proteins in membranebound ribosomes and free ribosomes. The molecular weights of the

Jean-Jacques Madjar; Alain Fournier

1981-01-01

205

Effect of temperature on the extent of migration of low molecular weight moieties to rubber surface  

Microsoft Academic Search

Vulcanized rubbers contain different low molecular weight additives in their formulation, including antiozonants, plasticizers, oils, etc. These moieties – mostly paraffin wax – often migrate to the surface causing a weak boundary layer of non-rubber contaminants which is deleterious for adhesion of rubber to adhesives (such as polyurethane and polychloroprene adhesives). One of the key steps in the manufacturing of

Rafael Torregrosa-Coque; Sonia Álvarez-García; José Miguel Martín-Martínez

2011-01-01

206

COMPARISON OF HIGH MOLECULAR WEIGHT ORGANICS ISOLATED FROM DRINKING WATER IN FIVE CITIES  

EPA Science Inventory

Since the previously unidentifiable non-volatile fraction of the chlorinated organics in drinking water is of significant health concern, the physical and chemical characteristics of the high molecular weight organics isolated from drinking water in five cities (New Orleans, Phil...

207

IR-MALDI OF LOW MOLECULAR WEIGHT COMPOUNDS USING A FREE ELECTRON LASER.  

EPA Science Inventory

Initial experiments on infrared matrix-assisted laser desorption/ionization mass spectrometry (IR-MALDI) using a free electron laser in the analysis of low-molecular-weight compounds are reported. Mass spectra from samples of ethylenediaminetetraacetic acid (EDTA), nitrilotriacet...

208

A low-molecular-weight supramolecular hydrogel of riboflavin bolaamphiphile for VEGF-siRNA delivery.  

PubMed

A low-molecular-weight hydrogel derived from riboflavin (vitamin B(2)) that self-assembles to provide supramolecular nanofibers, biocompatible material, can be used to deliver VEGF-siRNA efficiently into human cells by the endocytosis pathway, where the siRNA is functionalized. PMID:22847486

Patil, Sachin Prakash; Jeong, Hyun Seok; Kim, Byeang Hyean

2012-09-14

209

Monitoring of heparin and its low-molecular-weight analogs by silicon field effect  

E-print Network

Monitoring of heparin and its low-molecular-weight analogs by silicon field effect Nebojsa M, Stanford University, Stanford, CA, and approved July 20, 2006 (received for review May 31, 2006) Heparin and control of the heparin level in a patient's blood during and after surgery is essential, but current

Manalis, Scott

210

Delivery of therapeutic levels of heparin and low-molecular-weight heparin through a pulmonary route  

Microsoft Academic Search

Although heparin and low-molecular-weight heparins (LMWH) have been widely used clinically as anticoagulants, their broader use has been limited by the lack of noninvasive delivery methods for this class of molecules. In this study, we demonstrate an efficient, rapid, and reproducible delivery system for heparin through the lungs that is not confined to particles of a certain geometric or aerodynamic

Yiwei Qi; Ganlin Zhao; Dongfang Liu; Zachary Shriver; Mallik Sundaram; Shiladitya Sengupta; Ganesh Venkataraman; Robert Langer; Ram Sasisekharan

2004-01-01

211

Low molecular weight heparin aggravates infectious arthritis triggered by Staphylococcus aureus  

Microsoft Academic Search

Purpose. Staphylococcus aureus is responsible for the majority of wound infections in clean surgical procedures that involve implantation of foreign material, grafts or prosthetic devices. The aim of the study was to assess the effect of low molecular weight heparin on the development and progression of S. aureus arthritis.Materials and methods. The murine model of hematogenously acquired septic arthritis was

Egidija Sakiniene; Andrzej Tarkowski

2002-01-01

212

Low Molecular Weight Eosinophil Chemotactic Factor (ECF) in the Serum of Murine Schistosomiasis Japonica  

Microsoft Academic Search

Eosinophil chemotactic activity was detected in the serum obtained at an acute stage of murine schistosomiasis japonica. Gel filtration of the dialyzable fraction of the serum on Sephadex G25 showed that the chemotactic component had an apparent molecular weight of less than 1,000. It was stable to heating, but was sensitive to pronase or carboxypeptidase A digestions, indicating its peptide

Makoto Owhashi; Yoichro Horii; Akira Ishii; Yukifumi Nawa

1986-01-01

213

Influence of low molecular weight heparin preparations on human internal thoracic artery contraction  

Microsoft Academic Search

Objective: Low molecular weight heparins (LMWHs) offer practical and potential pharmacological advantages over unfractionated heparin in multiple applications but have not been studied as vasoactive agents. The purpose of this study was to investigate the effects of two commercial preparations of LMWHs, enoxaparin sodium and nadroparin calcium, on vasoconstriction in the human internal thoracic artery (ITA) in vitro. Methods: Samples

Leszek Buzun; Tomasz Kleszczewski; Anna Kostrzewska; Anna Pe; Tomasz Hirnle

214

Influence of low molecular weight heparin preparations on human internal thoracic artery contraction  

Microsoft Academic Search

Objective: Low molecular weight heparins (LMWHs) offer practical and potential pharmacological advantages over unfractionated heparin in multiple applications but have not been studied as vasoactive agents. The purpose of this study was to investigate the effects of two commercial preparations of LMWHs, enoxaparin sodium and nadroparin calcium, on vasoconstriction in the human internal thoracic artery (ITA) in vitro. Methods: Samples

Leszek Buzun; Tomasz Kleszczewski; Anna Kostrzewska; Piotr Lisowski; Piotr Oleksza; Ryszard Jackowski; Tomasz Hirnle

2004-01-01

215

Alpha naphthyl acetate esterase in human blood cells with different molecular weights  

Microsoft Academic Search

Normal human blood cells contain esterases which hydrolyze a-naphthyl acetate (aNA). Purified preparations of these cells were investigated by polyacrylamide gradient gel electrophoresis at pH 9.0 and subsequent staining of gels for esterase activity. Extractable aNA esterase was separated according to molecular weight.

J. Oertel; R. Wirthmüller; M. Kastner

1983-01-01

216

TOXICOLOGICAL HIGHLIGHT (REDOX REDUX: A CLOSER LOOK AT CONCEPTAL LOW MOLECULAR WEIGHT THIOLS)  

EPA Science Inventory

Glutathione (GSH) is present as the most abundant low molecular weight thiol (LMWT) in virtually all mitochondria-bearing eucaryotic cells, often at millimolar concentrations (Meister, 1988). Functions of GSH include roles in DNA and protein synthesis, maintenance of cell membra...

217

Infiltration and Erosion in Soils Treated with Dry PAM of Two Molecular Weights and Phosphogypsum  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soil surface application of dissolved linear polyacrylamide (PAM) of high molecular weight (MW) can mitigate seal formation, runoff and erosion, especially when added with a source of electrolytes (e.g., gypsum). Practical difficulties associated with PAM solution application prohibited commercial u...

218

LARGE SCALE EVALUATION OF A PATTERN RECOGNITION/EXPERT SYSTEM FOR MASS SPECTRAL MOLECULAR WEIGHT ESTIMATION  

EPA Science Inventory

A fast, personal-computer based method of estimating molecular weights of organic compounds from low resolution mass I spectra has been thoroughly evaluated. he method is based on a rule-based pattern,recognition/expert system approach which uses empirical linear corrections whic...

219

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight and concentration  

E-print Network

Drop formation and breakup of low viscosity elastic fluids: Effects of molecular weight fluids all exhibit the same global necking behavior that is observed for a Newtonian fluid of equivalent, as would occur in the equivalent Newtonian fluid. Alternatively, a cylindrical filament forms in which

220

Impact of Molecular Weight on Lymphatic Drainage of a Biopolymer-Based Imaging Agent  

E-print Network

different molecular weight hyaluronan (HA) near-infrared dye (HA-IR820) conjugates (ca. 5–200 nm). Mice were imaged using whole body fluorescent imaging over two weeks. HA-IR820 fluorescence was clearly visualized in the draining lymphatic capillaries...

Bagby, Taryn Rochelle; Cai, Shuang; Duan, Shaofeng; Thati, Sharadvi; Aires, Danial J.; Forrest, Marcus Laird

2012-05-23

221

Effect of chitosan molecular weight on rheological behavious of chitosan modified nanoclay at highly hydrated state  

Technology Transfer Automated Retrieval System (TEKTRAN)

Effect of chitosan molecular weight (M(cs)) on the rheological properties of chitosan modified clay (CMCs) at highly hydrated state was investigated. With special emphasis on its effect on the thixotropy of CMCs, the structure recovery at rest after underwent a pre-shearing process was further perfo...

222

Bimodal Molecular Weight Distribution Formed in Emulsion Polymerization with Long?Chain Branching  

Microsoft Academic Search

It is known that the molecular weight distribution (MWD) formed in emulsion polymerization of ethylene can be bimodal. A simplified model is used to investigate the emulsion polymerization that involves chain transfer to polymer, aiming at finding necessary conditions to form a bimodal MWD. According to the present theoretical investigation, a bimodal MWD can be formed when the probability that

H. Tobita

2003-01-01

223

Ultra-High Molecular-Weight Polyethylene Composites: Structure, Properties and Ballistic Response  

E-print Network

Ultra-High Molecular-Weight Polyethylene Composites: Structure, Properties and Ballistic Response increase in ballistic performance was attributed to the very high plastic strain energy absorption: James H. Aylor, Dean School of Engineering and Applied Science August 2010 #12;i ABSTRACT Ultra-high

Wadley, Haydn

224

Determination of low molecular weight thiols using monobromobimane fluorescent labeling and high-performance liquid chromatography  

NASA Technical Reports Server (NTRS)

Methods are described for the preparation and high-performance liquid chromatography (HPLC) analysis of monobromobimane derivatives of low molecular weight thiols in extracts of biological samples. Typical problems encountered in the development and application of these methods are discussed. Analysis of mung bean extract is used as an example.

Fahey, Robert C.; Newton, Gerald L.

1988-01-01

225

Determination of molecular weight of heparin by size exclusion chromatography with universal calibration  

E-print Network

Determination of molecular weight of heparin by size exclusion chromatography with universal chromatography using ``universal cali- bration.'' A universal calibration curve was constructed for Superose 12 chromatography (SEC).1 * Corresponding author. Fax: 1-317-274-6879. E-mail address: dubin@chem.iupui.edu (P

Dubin, Paul D.

226

Molecular weight distribution and functional group profiles of TEMPO-oxidized lyocell fibers.  

PubMed

The effects of TEMPO-mediated oxidation, performed with NaClO, a catalytic amount of NaBr, and 2,2',6,6'-tetramethylpiperidine-1-oxy radical (TEMPO), were studied on lyocell fibers by means of GPC using multiple detection and group-selective fluorescence labeling according to the CCOA and FDAM methodology. The applied method determines functional group content as a sum parameter, as well as functional group profiles in relation to the molecular weight of the cellulose fibers. Both the CHO and COOH profiles, as well as molecular weight alterations, were analyzed. A significant decrease in the average molecular weight was obtained during the first hour of TEMPO-mediated oxidation, but prolonged oxidation time resulted in no strong additional chain scission. Significant amounts of COOH groups were introduced in the high molecular weight fractions by the oxidation with higher concentrations of NaClO (2.42-9.67 mmol NaClO/g fiber) after modification times of 1h or longer. PMID:23987366

Milanovic, Jovana; Schiehser, Sonja; Milanovic, Predrag; Potthast, Antje; Kostic, Mirjana

2013-10-15

227

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

PubMed

The low-molecular-weight succinoglycans isolated from Sinorhizobium meliloti are repeating octasaccharide units consisting of monomers, dimers, and trimers. Pindolol is a beta-blocker used to treat cardiovascular disorders. We investigated the formation of complexes between pindolol and low-molecular-weight succinoglycan monomers (SGs). Even though SGs have a linear structure, the solubility of pindolol in the presence of SGs was increased up to 7-fold compared with methyl-?-cyclodextrin reported as the best solubilizer of pindolol. Complexation of SGs with pindolol was confirmed by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. Formation constants of complexes were determined from phase solubility diagrams. Conformation of complex was suggested based on a molecular docking study. The present study indicated that formation of pindolol/SGs complexes not only resulted in increased pindolol solubility but also could be useful for improving its clinical application as it did not affect cell viability. PMID:24721056

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

2014-06-15

228

Accurate molecular energies by extrapolation of atomic energies using an analytic quantum mechanical model  

Microsoft Academic Search

Using an analytic quantum-mechanical method based on Slater's Xalpha method, we show that a fairly accurate estimate of the total energy of a molecule can be obtained from the exact energies of its constituent atoms. The mean absolute error in the total energies thus determined for the G2 set of 56 molecules is about 16kcal\\/mol , comparable to or better

Rajendra R. Zope; Brett I. Dunlap

2005-01-01

229

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

PubMed

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 ?-cyclodextrin (?-CD) to the aqueous eluent. SEC mass recovery, especially for the higher molecular weight chains, increased with increasing concentration of ?-CD in the eluent. A ?-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. PMID:25092594

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

2014-09-12

230

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

SciTech Connect

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

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

2010-01-01

231

Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic and other trace elements  

Microsoft Academic Search

Low molecular weight thiol-containing compounds have been reported to play an important role in metal detoxification and accumulation in some higher plants. The formation of these low molecular weight thiols in the recently discovered arsenic hyperaccumulator, Chinese Brake fern (Pteris vittata) upon exposure to arsenic and other trace metals was investigated. In addition to cysteine and glutathione, an unidentified thiol

Yong Cai; Jinhui Su; Lena Q. Ma

2004-01-01

232

Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic and other trace elements  

E-print Network

Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic in the arsenic hyperaccumulator Pteris vittata. Abstract Low molecular weight thiol-containing compounds have, Chinese Brake fern (Pteris vittata) upon exposure to arsenic and other trace metals was investigated

Ma, Lena

233

ATOMIC FORCE MICROSCOPY OF A HYBRID HIGH-MOLECULAR-WEIGHT GLUTENIN SUBUNIT FROM A TRANSGENIC HEXAPLOID WHEAT  

Technology Transfer Automated Retrieval System (TEKTRAN)

The high-molecular-weight glutenin subunits (HMW-GS) of wheat gluten in their native form are incorporated into an intermolecularly disulfide-linked, polymeric system that gives rise to the elasticity of wheat flour doughs. These protein subunits range in molecular weight from about ''K-90K and are...

234

Low molecular weight heparin versus regular heparin or aspirin in the treatment of unstable angina and silent ischemia  

Microsoft Academic Search

Objectives. This study was designed to test the hypothesis that low molecular weight heparin may lessen the severity of ischemic events in patients with unstable angina.Background. Unstable angina is a thrombotic process that requires intensive medical treatment Although current treatments can reduce the number of complications, serious bleeding continues to occur. Nadroparin calcium, a low molecular weight heparin, seems to

Enrique P. Gurfinkel; Eustaquio J. Manos; Ricardo I. Mejaíl; Miguel A. Cerdá; Ernesto A. Duronto; Claudio N. García; Ana M. Daroca; Branco Mautner

1995-01-01

235

Effect of molecular weight of polymeric additives on formation, permeation properties and hypochlorite treatment of asymmetric polyacrylonitrile membranes  

Microsoft Academic Search

Asymmetric polyacrylonitrile membranes were prepared via phase inversion process from casting solution composed of synthesized polyacrylonitrile (PAN), dimethylsulfoxide (DMSO), and poly(vinylpyrrolidone) (PVP) of different molecular weights. The effect of molecular weight of PVP in the casting solution on the morphology, water flux was investigated. The effect of hypochlorite treatment on PVP which was entrapped in pore was investigated. As the

Bumsuk Jung; Joon Ki Yoon; Bokyung Kim; Hee-Woo Rhee

2004-01-01

236

PCR analysis of genes encoding allelic variants of high-molecular-weight glutenin subunits at the Glu-D1 locus.  

PubMed

Genes encoding high-molecular-weight (HMW) glutenin subunits, present in bread-wheat lines and cultivars, were studied by RFLP (restriction fragment length polymorphism) and PCR (polymerase chain reaction) analyses. In particular, allelic subunits of the x-or y-type, encoded at the Glu-D1 locus present on the long arm of chromosome 1D, were investigated. The variation in size, observed in different allelic subunits, is mainly due to variation in the length of the central repetitive domain, typical of these proteins. Deletions or duplications, probably caused by unequal crossingover, have given rise to the size heterogeneity currently observed. The possibility of using the PCR technique for a detailed analysis of HMW glutenin genes in order to obtain a more accurate estimation of the molecular weight of their encoded subunits, and the detection of unexpressed genes, is also described. PMID:24185923

D'Ovidio, R; Porceddu, E; Lafiandra, D

1994-05-01

237

Accurate specific molecular state densities by phase space integration. I. Computational method  

NASA Astrophysics Data System (ADS)

The semiclassical determination of the specific density of quantum states, ?(E;J), at energy E with fixed total angular momentum J is discussed for small molecules. Monte Carlo integration allows the accurate numerical determination of the phase space volume of systems with J>0 and arbitrary anharmonicity. The corresponding semiclassical number of states can be corrected for the effects of zero point motion in analogy to the well-known Whitten-Rabinovitch procedure. In this paper, the procedures are tested by comparison with rigid rotor harmonic oscillator models, while a comparison with recent exact quantum calculations on H+3 and HD+2 is described in the following paper. We conclude that, if the intramolecular potential is known or assumed, this numerical semiclassical procedure is a viable and simple way to get state densities of a much improved accuracy.

Berblinger, Michael; Schlier, Christoph

1992-05-01

238

Accurate vibrational spectra via molecular tailoring approach: A case study of water clusters at MP2 level  

NASA Astrophysics Data System (ADS)

In spite of the recent advents in parallel algorithms and computer hardware, high-level calculation of vibrational spectra of large molecules is still an uphill task. To overcome this, significant effort has been devoted to the development of new algorithms based on fragmentation methods. The present work provides the details of an efficient and accurate procedure for computing the vibrational spectra of large clusters employing molecular tailoring approach (MTA). The errors in the Hessian matrix elements and dipole derivatives arising due to the approximation nature of MTA are reduced by grafting the corrections from a smaller basis set. The algorithm has been tested out for obtaining vibrational spectra of neutral and charged water clusters at Møller-Plesset second order level of theory, and benchmarking them against the respective full calculation (FC) and/or experimental results. For (H2O)16 clusters, the estimated vibrational frequencies are found to differ by a maximum of 2 cm-1 with reference to the corresponding FC values. Unlike the FC, the MTA-based calculations including grafting procedure can be performed on a limited hardware, yet take a fraction of the FC time. The present methodology, thus, opens a possibility of the accurate estimation of the vibrational spectra of large molecular systems, which is otherwise impossible or formidable.

Sahu, Nityananda; Gadre, Shridhar R.

2015-01-01

239

Accurate vibrational spectra via molecular tailoring approach: A case study of water clusters at MP2 level.  

PubMed

In spite of the recent advents in parallel algorithms and computer hardware, high-level calculation of vibrational spectra of large molecules is still an uphill task. To overcome this, significant effort has been devoted to the development of new algorithms based on fragmentation methods. The present work provides the details of an efficient and accurate procedure for computing the vibrational spectra of large clusters employing molecular tailoring approach (MTA). The errors in the Hessian matrix elements and dipole derivatives arising due to the approximation nature of MTA are reduced by grafting the corrections from a smaller basis set. The algorithm has been tested out for obtaining vibrational spectra of neutral and charged water clusters at Møller-Plesset second order level of theory, and benchmarking them against the respective full calculation (FC) and/or experimental results. For (H2O)16 clusters, the estimated vibrational frequencies are found to differ by a maximum of 2 cm(-1) with reference to the corresponding FC values. Unlike the FC, the MTA-based calculations including grafting procedure can be performed on a limited hardware, yet take a fraction of the FC time. The present methodology, thus, opens a possibility of the accurate estimation of the vibrational spectra of large molecular systems, which is otherwise impossible or formidable. PMID:25573553

Sahu, Nityananda; Gadre, Shridhar R

2015-01-01

240

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

USGS Publications Warehouse

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

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

1997-01-01

241

High molecular weight acidic polysaccharides from Malva sylvestris and Alcea rosea.  

PubMed

Leaves and flowers of Malva sylvestris and Alcea rosea (Malvaceae) were compared by determination of the swelling index as well as the content and viscosity of their mucilages. The investigations showed mucilage from flowers of Alcea to be superior to mucilages from leaves or flowers from Malva. High molecular weight acidic polysaccharides (HMWAPs) were isolated from the mucilages of leaves and flowers of both species. The molecular weight of all HMWAPs was in a range of 1.3 to 1.6 x 10(6) D. HMWAP-content in mucilage from flowers of Alcea was highest compared to content in mucilages from leaves or flowers from Malva. HMWAPs were found to be composed mainly of glucuronic acid, galacturonic acid, rhamnose and galactose. Methylation analysis of the carboxyl-reduced and deuterium labeled sugar derivatives of HMWAPs from flowers of Malva sylvestris ssp. mauritiana and Alcea rosea enabled elucidation of the principal structural features of both polysaccharides. PMID:9810269

Classen, B; Blaschek, W

1998-10-01

242

[Circadian rhythm of ornithine decarboxylase and its endogenous high molecular weight inhibitor in rat pineal gland].  

PubMed

The biochemical mechanisms involved in circadian variations of the activity of ornithine decarboxylase (EC 4.1.1.17)--the rate-limiting enzyme of polyamine biosynthesis in rat pineal gland were studied. The enzyme was separated from its endogenous high molecular weight inhibitor by gel-filtration of the cytosol fraction from this organ through Sephadex G-100 in the presence of 250 mM NaCl. The inhibitor was similar in its molecular weight (30 000) and activity to ornithine decarboxylase inhibior from rat liver. The amount of the enzyme in the pineal gland undergoes much smaller circadian variations as compared to that of the inhibitor. It is concluded that the circadian variations of the ornithine decarboxylase activity in the pineal gland may be largely due to the changes in the enzyme/inhibitor ratio. PMID:497279

Iarygin, K N; Trushina, E D; Isachenkov, V A

1979-07-01

243

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

USGS Publications Warehouse

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.

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

2007-01-01

244

Probable identity of NILE glycoprotein and the high-molecular-weight component of L1 antigen.  

PubMed

We report here that anti-L1 antiserum, raised against material from embryonic brain, and anti-NILE antiserum, raised against purified NILE (nerve growth factor-inducible large external) glycoprotein of PC12 cells, immunoprecipitate from PC12 cells material of the same apparent molecular weight (230 kilodaltons) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Furthermore, each of these immune reagents has the capacity to clear from a PC12 cell extract all of the 230-kilodalton antigen recognized by the other antiserum. Finally, in immunohistochemical staining of developing cerebellum the two antisera exhibit very similar staining patterns. We suggest that the NILE glycoprotein and the high-molecular-weight component of L1 antigen are closely related molecules, and probably the same. PMID:2426400

Sajovic, P; Kouvelas, E; Trenkner, E

1986-08-01

245

Degradation of high-molecular-weight hyaluronan by hydrogen peroxide in the presence of cupric ions.  

PubMed

Dynamic viscosity (eta) of the high-molecular-weight hyaluronan (HA) solution was measured by a Brookfield rotational viscometer equipped with a Teflon cup and spindle of coaxial cylindrical geometry. The decrease of eta of the HA solution, indicating degradation of the biopolymer, was induced by a system containing H2O2 alone or H2O2 plus CuCl2. The reaction system H2O2 plus CuCl2 as investigated by EPR spin-trapping technique revealed the formation of a four-line EPR signal characteristic of a *DMPO-OH spin adduct. Thus, hydroxyl radicals are implicated in degradation of high-molecular-weight HA by the system containing H2O2 and CuCl2. PMID:16445893

Soltés, Ladislav; Brezová, Vlasta; Stankovská, Monika; Kogan, Grigorij; Gemeiner, Peter

2006-04-10

246

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

NASA Technical Reports Server (NTRS)

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

Babcock, Dale A.

1995-01-01

247

Sulfated, Low Molecular Weight Lignins Inhibit a Select Group of Heparin-Binding Serine Proteases  

PubMed Central

Sulfated low molecular weight lignins (LMWLs), designed as oligomeric mimetics of low molecular weight heparins (LMWHs), have been found to bind in exosite II of thrombin (Abdel Aziz et al. Biochem. Biophys. Res. Commun. 413 (2011) 348–352). To assess whether sulfated LMWLs recognize other heparin-binding proteins, we studied their effect on serine proteases of the coagulation, inflammatory and digestive systems. Using chromogenic substrate hydrolysis assay, sulfated LMWLs were found to potently inhibit coagulation factor XIa and human leukocyte elastase, moderately inhibit cathepsin G and not inhibit coagulation factors VIIa, IXa, and XIIa, plasma kallikrein, activated protein C, trypsin, and chymotrypsin. Competition studies show that UFH competes with sulfated LMWLs for binding to factors Xa and XIa. These results further advance the heparin-mimicking property of sulfated LMWLs and will aid the design of anticoagulants based on their novel scaffold. PMID:22155248

Henry, Brian L.; Thakkar, Jay N.; Liang, Aiye; Desai, Umesh R.

2012-01-01

248

Accurate Density Measurements of Molecular Cores Using K-Doublet Formaldehyde Transitions  

NASA Astrophysics Data System (ADS)

The densities of protostellar cores are poorly constrained. The current techniques come with substantial uncertainty, and the molecular tracers traditionally used are subject to radiative transfer effects at densities approaching and greater than 106cm-3. Formaldehyde (H2CO) is a proven tracer of the high-density environs in molecular clouds. It is ubiquitous: H2CO is associated with 80% of the HII regions surveyed by Downes et al. (1980) and because of its low relative abundance, H2CO transitions rarely become optically thick. H2CO is a slightly asymmetric rotor molecule, so each rotational energy level is split into two, leading to two basic types of transitions: the higher frequency, "P-branch” transitions (?J=1, ?K-1=0, ?K+1=1) and the lower frequency, "Q-branch” or "K-doublet” transitions (?J=0, ?K-1=0, ?K+1=+1), which are uniquely sensitive to spatial density. For n(H2)<105cm-3 the lower energy states (J<5) become overpopulated due to a collisional selection effect. This cools them to excitation temperatures lower than that of the CMB, causing the K-doublet transitions to appear in absorption. For n(H2)>105.5cm-3, the collisional pump is quenched and the lines are seen in emission. An LVG model prediction of the ratio of two of these transitions can further constrain the density with a high degree of accuracy. We present GBT observations of the J=3 and J=4 K-doublets toward 22 galactic, star-forming sites. Adopting kinetic temperatures from the literature, we have used an LVG model to derive the average density within a 16” beam toward each source. Spatial densities between 1-2 x106cm-3 and column densities between 1-9 x1013cm-2/km s-1 are found for most of the sources. The statistical uncertainty from our measurement uncertainty alone is 10%. The ease with which these transitions are detected along with their unique sensitivity to spatial density make them excellent monitors of density in molecular cores for this and future experiments.

McCauley, Patrick; Mangum, J.; Wootten, A.

2010-01-01

249

Role of Gas Pressure and Molecular Weight in Bubble Pinch-Off from an Underwater Nozzle  

Microsoft Academic Search

We report on experiments that explore the role of gas pressure and molecular weight near the pinch-off of an air bubble from an nozzle submerged in water. We use high-speed video to image the dynamics close to the singularity occurring at pinch-off. As the neck collapses to a radius of several microns, the effects of the Bernoulli pressure associated with

Nathan C. Keim; Sidney R. Nagel

2008-01-01

250

Solubility and molecular weight of hemicelluloses from Alnus incana and Alnus glutinosa. Effect of tree age  

Microsoft Academic Search

The xylems of Alnus incana Moench. and Alnus glutinosa Gaertn. 8-15-year-old trees were subjected to comparative studies regarding the molecular weight (MW) of hemicelluloses. Extraction of hemicelluloses according to the sequence 1% NaOH-10% KOH-18% NaOH, followed by direct analysis of each extract using the SEC\\/UV method, was applied aiming at simultaneous quantitative and MW analysis. Both the tree age and

Tatiana Bikova; Arnis Treimanis

2002-01-01

251

Hydrogen isotope fractionation of low molecular weight n-alkanes during progressive vaporization  

Microsoft Academic Search

We determined the stable hydrogen isotope fractionation during progressive vaporization of three n-alkanes (heptane or C7, octane or C8, nonane or C9) at 24±1 °C, in an effort to understand the environmental isotopic fractionation of low molecular weight petroleum hydrocarbons. The measurements were carried out using continuous flow gas chromatography- high temperature conversion–isotope ratio mass spectrometry (GC\\/TC\\/IRMS). During the course of

Yi Wang; Yongsong Huang

2001-01-01

252

Sorption and permeation of low molecular weight volatile compounds in polypropylene  

E-print Network

there is no interaction between the polymer and the penetrant molecules. The permeability coefficient is the combination of the diffusion coefficient (D) and solubility coefficient (S). They are 8 related as follows: P DS The diffusion coefficient is associated... with the velocity of propagation of the permeant molecules, and the solubility coefficient reflects the degree of affinity between the permeant molecules and the polymer. 9 The list of factors influencing sorption and permeation of low molecular weight organic...

Vidal, Antonio Ramiro Santiago

2012-06-07

253

Comparative study of protein molecular weights by size-exclusion chromatography and laser-light scattering  

Microsoft Academic Search

High-performance size-exclusion chromatography (SEC) based on UV-Vis detection is a relative technique for molecular weight determination whereas procedure based on multi-angle laser light scattering (MALLS) is both rapid and absolute. The two methods using recombinant human growth hormone (rHGH) and ?-lactoglobulin samples were compared. A calibration curve for the chromatographic system was generated based on standard proteins and the data

Alexis Oliva; Mat??as Llabrés; José B Fariña

2001-01-01

254

Molecular weight distribution of proteinaceous material in Long Island Sound sediments  

Microsoft Academic Search

Abstract Proteinaceous material usually accounts for much,of the total nitrogen and organic carbon in marine sediments. Thus, decomposition of protein is frequently investigated as a measure of labile organic matter turnover. The fraction of protein that escapes remineralization to CO2 undergoes,transformations that may,reflect pathways,of preservation in sedimentary,environments. We analyzed,the molecular weight distribution of sedimentary,proteinaceous,material extracted with NaOH and evaluated the

Silvio Pantoja; Cindy Lee

1999-01-01

255

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

PubMed

A novel series of glucagon receptor antagonists has been discovered. These pyrazole ethers and aminopyrazoles have lower molecular weight and increased polarity such that the molecules fall into better drug-like property space. This work has culminated in compounds 44 and 50 that were shown to have good pharmacokinetic attributes in dog, in contrast to rats, in which clearance was high; and compound 49, which demonstrated a dose-dependent reduction in glucose excursion in a rat glucagon challenge experiment. PMID:22119466

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

2012-01-01

256

Effect of Molecular Weight on the Interfacial Dilational Viscoelasticity of Anionic Polyelectrolyte\\/Surfactant Systems  

Microsoft Academic Search

In this article, the effect of molecular weight on the interfacial tension and interfacial dilational viscoelasticity of polystyrene sulfonate\\/surfactant adsorption films at the water-octane interface have been studied by spinning drop method and oscillating barriers method respectively. The experimental results show that different interfacial behaviors can be observed in different type of polyelectrolyte\\/surfactant systems. PSS\\/cationic surfactant CTAB systems show the

Hong-Bo Fang; Hua Zong; Lei-Ting Mao; Lu Zhang; Guo-Zhu Cui; Sui Zhao; Jia-Yong Yu

2010-01-01

257

Combination of various analytical techniques for speciation of low molecular weight aluminium complexes in plant sap  

Microsoft Academic Search

The possibilities for speciation of low molecular weight aluminium organic acid complexes (LMW-Al) in plant sap were investigated\\u000a by applying a combination of various chromatographic and spectroscopic techniques. The behavior of different LMW-Al complexes\\u000a was investigated in synthetic aqueous solutions on anion and cation exchange fast protein liquid chromatography (FPLC) columns\\u000a with inductively coupled plasma – atomic emission spectrometry (ICP-AES)

Tjaöa Bantan; R. Mila?i?; B. Mitrovi?; Boris Pihlar

1999-01-01

258

Efficient bulk heterojunction photovoltaic cells using small-molecular-weight organic thin films  

Microsoft Academic Search

The power conversion efficiency of small-molecular-weight and polymer organic photovoltaic cells has increased steadily over the past decade. This progress is chiefly attributable to the introduction of the donor-acceptor heterojunction that functions as a dissociation site for the strongly bound photogenerated excitons. Further progress was realized in polymer devices through use of blends of the donor and acceptor materials: phase

Peter Peumans; Soichi Uchida; Stephen R. Forrest

2003-01-01

259

Development of an extremely wear-resistant ultra high molecular weight polyethylene for total hip replacements.  

PubMed

Osteolysis induced by ultra high molecular weight polyethylene wear debris is one of the primary factors limiting the lifespan of total hip replacements. Crosslinking polyethylene is known to improve its wear resistance in certain industrial applications, and crosslinked polyethylene acetabular cups have shown improved wear resistance in two clinical studies. In the present study, crosslinked polyethylene cups were produced by two methods. Chemically crosslinked cups were produced by mixing a peroxide with ultra high molecular weight polyethylene powder and then molding the cups directly to shape. Radiation-crosslinked cups were produced by exposing conventional extruded ultra high molecular weight polyethylene bar stock to gamma radiation at various doses from 3.3 to 100 Mrad (1 Mrad = 10 kGy), remelting the bars to extinguish residual free radicals (i.e., to minimize long-term oxidation), and then machining the cups by conventional techniques. In hip-joint simulator tests lasting as long as 5 million cycles, both types of cross-linked cups exhibited dramatically improved resistance to wear. Artificial aging of the cups by heating for 30 days in air at 80 degrees C induced oxidation of the chemically crosslinked cups. However, a chemically crosslinked cup that was aged 2.7 years at room temperature had very little oxidation. Thus, whether substantial oxidation of chemically crosslinked polyethylene would occur at body temperature remains unclear. The radiation-crosslinked remelted cups exhibited excellent resistance to oxidation. Because crosslinking can reduce the ultimate tensile strength, fatigue strength, and elongation to failure of ultra high molecular weight polyethylene, the optimal crosslinking dose provides a balance between these physical properties and the wear resistance of the implant and might substantially reduce the incidence of wear-induced osteolysis with total hip replacements. PMID:10221831

McKellop, H; Shen, F W; Lu, B; Campbell, P; Salovey, R

1999-03-01

260

The Determination of Hyaluronan Molecular Weight Distribution by Means of High-Performance Size Exclusion Chromatography  

Microsoft Academic Search

The high-performance liquid chromatographic (HPLC) method relevant to the size exclusion chromatographic mode (SEC) used for the distribution analysis of high-molecular-weight hyaluronans is described. The HPLC fillings used, to which was applied a phosphate buffer (50 mM, pH 7.8) effluent, consisted of a cross-linked hydroxyethylmethacrylate derivative gel (HEMA-BIO), which is commercially available, and a highly porous aminopropyl-silica sorbent (SG-10-6000-NH2), which

E. Orviský; L. Šoltés; P. Chabr?ek; I. Novák; V. Kéry; M. Stan?íková; I. Vinš

1992-01-01

261

Degradation of high-molecular-weight hyaluronan by hydrogen peroxide in the presence of cupric ions  

Microsoft Academic Search

Dynamic viscosity (?) of the high-molecular-weight hyaluronan (HA) solution was measured by a Brookfield rotational viscometer equipped with a Teflon cup and spindle of coaxial cylindrical geometry. The decrease of ? of the HA solution, indicating degradation of the biopolymer, was induced by a system containing H2O2 alone or H2O2 plus CuCl2. The reaction system H2O2 plus CuCl2 as investigated

Ladislav Šoltés; Vlasta Brezová; Monika Stankovská; Grigorij Kogan; Peter Gemeiner

2006-01-01

262

Solvent Annealing Strategies for the Self-Assemblty of Low Molecular Weight Block Copolymers  

Microsoft Academic Search

Templated self-assembly of block copolymer (BCP) films is of intrest for lithographic applications. As the drive for smaller features continues, we explore the extensibility of block copolymer microphase separation towards smaller periods in a series of low molecular weight (5 -15 kg\\/mol) poly(styrene-b-dimethylsiloxane) (PS-PDMS) diblock copolymers. This material exhibits a large segmental Flory-Huggins interaction parameter ( 0.26), enabling microphase separation

Kevin Gotrik; Yeon Sik Jung; Jeong Gon Son; Caroline Ross

2010-01-01

263

Alkali-Degraded Cornea Generates a Low Molecular Weight Chemoattractant for Polymorphonuclear Leukocytes  

Microsoft Academic Search

Purpose. The current study was designed to determine if a polymorphonuclear leukocyte (PMN) chemoattractant is derived from alkali-degraded whole cornea and to establish a range for its molecular weight. Methods. We utilized a collagen gel-visual chemotactic assay to quantify the directional move- ment of PMN exposed to alkali-degraded corneas (30 min or 24 hi). In this experiment, the sample to

Roswell R. Pfister; Jeffrey L. Haddox; Charnell I. Sommers

264

Structural and functional properties of low molecular weight endo-1,4-? -xylanases  

Microsoft Academic Search

There are currently four crystal structures of low molecular weight endo-1,4-?-xylanases (E.C.3.2.1.8), i.e. family G\\/11 xylanases, available at the Brookhaven Data Bank: 2 xylanases from Trichoderma reesei (Törrönen et al., (1994); Törrönen and Rouvinen, (1995)) and one from Bacillus circulans and another from Trichoderma harzianum (Campbell et al., (1993)). They consist of two ?-sheets and one ?-helix and have been

Anneli Törrönen; Juha Rouvinen

1997-01-01

265

Studies of low density lipoprotein molecular weight in human beings with coronary artery disease  

Microsoft Academic Search

Low density lipoprotein molecular weight (LDL MW) correlates positively with coronary artery disease in cho- lesterol-fed nonhuman primates. To evaluate this in human beings with coronary artery disease (CAD) we measured LDL MW in 93 volunteers undergoing coronary angiography (47 controls and 46 CAD patients). LDL MW of CAD patients was less than that of controls (patients, 2.79 * 0.17

John R. Crouse; Johns S. Parks; Harry M. Schey; Frederic R. Kahl

266

Low molecular weight heparin (bemiparin sodium) and the coagulation profile of patients with heart failure  

Microsoft Academic Search

Background Congestive heart failure (CHF) is associated with a hypercoagulable state. Patients and Methods A single-center, randomized, double-blind, placebo-controlled trial was performed to test the hypothesis that a prophylactic dose of low molecular weight heparin (bemiparin sodium 3500 IU\\/daily subcutaneously) will modify a hypercoagulable state in CHF. This study included 100 patients with CHF (New York Heart Association classification II

Ferruccio De Lorenzo; Douglas Newberry; Mike Scully; Zibgniew Kadziola; Gloria Dawson; Nancy Ranlall; Neelam Saba; Ali Noorani; Shaharam Kashani; Rene' Williams; Vijay Vir Kakkar

2002-01-01

267

Effects of a Low Molecular Weight Heparin, Bemiparin, and Unfractionated Heparin on Hemostatic Properties of Endothelium  

Microsoft Academic Search

Human endothelial cells synthesize and secrete a variety of molecules involved in fibrinolysis and coagulation. The effects of a low molecular weight heparin, Bemiparin, and unfractionated heparin (UFH) were compared on plasminogen activator inhibitor-i (PAI-1), tissue-plasminogen activator (t-PA), tissue factor (TF), tissue factor pathway inhibitor (TFPI) release, and PAl-i gene expression by human umbilical vein endothelial cells (HUVEC). Cell cultures

Ana Perez-Ruiz; Ramon Montes; Pilar Carrasco; Eduardo Rocha

2002-01-01

268

Bioreversibly crosslinked polyplexes of PEI and high molecular weight PEG show extended circulation times in vivo  

Microsoft Academic Search

Copolymers consisting of branched PEI 25 kDa grafted with high molecular weight PEG at a low degree of substitution were successfully synthesized using a simple two-step procedure. The resulting AB-type and ABA-type copolymers were tested for cytotoxicity and DNA condensation and complexation properties. Their polyplexes with plasmid DNA were characterized in terms of DNA size and surface charge, transfection efficiency and

Michael Neu; Oliver Germershaus; Martin Behe; Thomas Kissel

2007-01-01

269

Structural and genetical studies on the high-molecular-weight subunits of wheat glutenin  

Microsoft Academic Search

Summary  The high-molecular-weight (HMW) subunits of glutenin from about 185 varieties were fractionated by sodium dodecyl sulphate\\u000a polyacrylamide gel electrophoresis (SDS-PAGE). About 20 different, major subunits were distinguished by this technique although\\u000a each variety contained, with only a few exceptions, between 3 and 5 subunits. Further inter-varietal substitution lines to\\u000a those already described (Payne et al. 1980) were analysed and the

P. I. Payne; L. M. Holt; C. N. Law

1981-01-01

270

Accurate molecular diagnosis of phenylketonuria and tetrahydrobiopterin-deficient hyperphenylalaninemias using high-throughput targeted sequencing.  

PubMed

Genetic diagnostics of phenylketonuria (PKU) and tetrahydrobiopterin (BH4) deficient hyperphenylalaninemia (BH4DH) rely on methods that scan for known mutations or on laborious molecular tools that use Sanger sequencing. We have implemented a novel and much more efficient strategy based on high-throughput multiplex-targeted resequencing of four genes (PAH, GCH1, PTS, and QDPR) that, when affected by loss-of-function mutations, cause PKU and BH4DH. We have validated this approach in a cohort of 95 samples with the previously known PAH, GCH1, PTS, and QDPR mutations and one control sample. Pooled barcoded DNA libraries were enriched using a custom NimbleGen SeqCap EZ Choice array and sequenced using a HiSeq2000 sequencer. The combination of several robust bioinformatics tools allowed us to detect all known pathogenic mutations (point mutations, short insertions/deletions, and large genomic rearrangements) in the 95 samples, without detecting spurious calls in these genes in the control sample. We then used the same capture assay in a discovery cohort of 11 uncharacterized HPA patients using a MiSeq sequencer. In addition, we report the precise characterization of the breakpoints of four genomic rearrangements in PAH, including a novel deletion of 899?bp in intron 3. Our study is a proof-of-principle that high-throughput-targeted resequencing is ready to substitute classical molecular methods to perform differential genetic diagnosis of hyperphenylalaninemias, allowing the establishment of specifically tailored treatments a few days after birth. PMID:23942198

Trujillano, Daniel; Perez, Belén; González, Justo; Tornador, Cristian; Navarrete, Rosa; Escaramis, Georgia; Ossowski, Stephan; Armengol, Lluís; Cornejo, Verónica; Desviat, Lourdes R; Ugarte, Magdalena; Estivill, Xavier

2014-04-01

271

Accurate description of phase diagram of clathrate hydrates at the molecular level.  

PubMed

In order to accurately estimate the thermodynamic properties of hydrogen clathrate hydrates, we developed a method based on the solid solution theory of van der Waals and Platteeuw. This model allows one to take into account the influence of guest molecules on the host lattice and guest-guest interactions--especially when more than one guest molecule occupies a cage. The free energies, equations of state, and chemical potentials of hydrogen and mixed propane-hydrogen clathrate hydrates of cubic structure II with different cage fillings have been estimated using this approach. Moreover, the proposed theory has been used for construction p-T phase diagrams of hydrogen hydrate and mixed hydrogen-propane hydrates in a wide range of pressures and temperatures. For the systems with well defined interactions the calculated curves of "guest gas-hydrate-ice I(h)" equilibrium agree with the available experimental data. We also believe that the present model allows one not only to calculate the hydrogen storage ability of known hydrogen hydrate but also predict this value for structures that have not yet been realized by experiment. PMID:20059082

Belosudov, Rodion V; Subbotin, Oleg S; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki; Belosludov, Vladimir R

2009-12-28

272

Stabilization of montmorillonite clay in porous media by high-molecular-weight polymers  

SciTech Connect

In this paper a dynamic method is proposed for checking the stability of clay in porous media for different brine conditions and the stabilizing effect provided by several anionic and nonionic high-molecular-weight polymers. The method consists of injecting brine at decreasing salinity levels into clayey sandpacks until unstabilized permeability reduction is reached from the dislodging of clay particles that become trapped in pore restrictions. The last stable state before clay destablization is characterized by a critical salinity concentration (CSC). As expected, montmorillonite clay 5% dispersed in a sandpack is more stable in the presence of KCl than NaCl brines, giving CSC values of 5,000 and 27,500 ppm, respectively. Polyacrylamides are much better clay stabilizers than carboxymethyl cellulose (CMC) or xanthan gum (XG), lowering the CSC of KCl to 1,000 to 2,000 ppm and the CSC of NaCl to 6,000 to 7,000 ppm. A low-molecular-weight shear-degraded polyacrylamide is shown to keep good stabilizing power without inducing the high permeability reduction values obtained after adsorption of high-molecular-weight products. In addition to preventing clay migration, polyacrylamides are also shown to inhibit clay swelling.

Zaitoun, A.; Berton, N. (Inst. Francais du Petrole (FR))

1992-05-01

273

Interfacial microgels formed by oppositely charged polyelectrolytes and surfactants. 1. Influence of polyelectrolyte molecular weight.  

PubMed

The synergistic adsorption and complexation of polystyrene sulfonate, PSS (a highly charged anionic polyelectrolyte), and dodecyltrimethylammonium bromide, C12TAB (a cationic surfactant), at the air-water interface can lead to interfacial gels that strongly influence foam-film drainage and stability. The formation and characteristics of these gels have been studied as a function of PSS molecular weight by combining surface tension, ellipsometry, and foam-film drainage experiments. Simultaneously the solution electromotive force has been measured to track the polymer-surfactant interactions in the bulk solution. It has been found that there is a critical molecular weight for surface gelation as well as for bulk precipitation and aggregation. Furthermore, we show that for the lowest molecular weights, PSS adsorbs with C12TAB in compact layers at the air-water interface. In particular, for mixtures of C12TAB with the monomer compound of the PSS repeat unit (e.g. Mw = 208), interfacial complexation is found to be similar to that of catanionic mixtures (mixtures of surfactants of opposite charge). PMID:15986674

Monteux, Cécile; Llauro, Marie-France; Baigl, Damien; Williams, Claudine E; Anthony, Olivier; Bergeron, Vance

2004-06-22

274

INFLUENCE OF POLYMER MOLECULAR WEIGHT, TEMPERATURE, AND STRAIN RATE ON THE MECHANICAL PROPERTIES OF PBX 9501  

SciTech Connect

Compression and tensile measurements were conducted on newly formulated (baseline) and lower molecular weight (virtually-aged) plastic-bonded explosive PBX 9501. The PBX 9501 binder system is composed of nitroplasticized Estane 5703, TM a polyester polyurethane copolymer. The molecular weight of polyester urethanes can degrade with time as a function of hydrolysis, affecting the mechanical behavior of the polymer or a polymer composite material of high explosives, i.e. PBXs. The molecular weight of Estane 5703{trademark} was degraded by exposure to high temperature and humidity for different periods of time, and then formulated to produce ''virtually-aged'' PBX 9501 specimens. Quasi-static and dynamic compression tests were conducted on the baseline and virtually-aged PBX 9501 as a function of temperature and strain rate. Quasi-static tensile tests were also conducted as a function of temperature and test rate. Rate and temperature dependence was exhibited during both compression and tensile loading. Results also show significant differences between the baseline and virtually-aged specimens for the dynamic compression tests at -15 C, and for the quasi-static compression tests at -15 C, 22 C, and 50 C.

D. J. IDAR; D. G. THOMPSON; ET AL

2001-06-01

275

The Effect of PEG Molecular Weights on Dissolution Behavior of Simvastatin in Solid Dispersions  

PubMed Central

The purpose of the present study was to investigate the effect of polyethylene glycol (PEG) molecular weights (6000, 12000 and 20000) as solid dispersion (SD) carriers on the dissolution behavior of simvastatin. SDs with various drug : carrier ratios were prepared by solvent method and evaluated for dissolution rate. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), infrared spectroscopy and solubility studies were also performed on the optimum SD formulation. Samples prepared with all three types of PEG showed improved drug dissolution compared to intact drug and corresponding physical mixtures. Meanwhile, the best result was obtained by PEG 12000 with drug : carrier ratio of 1:7 which showed a 3-fold increase in dissolution rate compared to the intact drug. Based on DSC and XRD, no crystalline change occurred during the sample preparation. Solubility studies revealed that increasing the PEG molecular weight resulted in higher phase solubility of drug. In addition, saturated solubility of the optimum SD was significantly higher than that of intact drug and the related physical mixture (24.83, 8.74 and 8.88 ?g/mL, respectively) that could be due to the decreased particle size and aggregation. The results confirmed the influence of PEG molecular weight on drug dissolution rate from solid dispersion systems. PMID:24250667

Bolourchian, Noushin; Mahboobian, Mohammad Mehdi; Dadashzadeh, Simin

2013-01-01

276

Developmental co-expression of small molecular weight apolipoprotein B synthesis and triacylglycerol secretion  

SciTech Connect

The development of the liver's ability to coordinately express the synthesis and secretion of the two major components of very low density lipoproteins (VLDL): triacylglycerol (TG) and apolipoprotein B (apo B) was examined in cultured hepatocytes obtained from fetal, suckling and adult rats. Hepatocytes from fetal and suckling rats synthesized and secreted TG at rates lower than that displayed by adult cells. When TG synthesis was equalized by adding oleic acid to the culture medium, fetal cells still secreted only 39% as much TG as did adult cells. To determine the basis for the apparent defect in VLDL assembly/secretion displayed by fetal cells, the synthesis and secretion of (TVS)methionine-labeled apo B was quantified by immunoprecipitation. Although adult and fetal cells synthesized and secreted large molecular weight apo B at similar rates, the synthesis and secretion of small molecular weight apo B was 2-fold greater in adult cells. These data suggest that the ability to assemble/secrete VLDL triacylglycerol varies in parallel with the developmental expression of small molecular weight apo B. Furthermore, these studies show the usefulness of the cultured rat hepatocyte model for examining the ontogeny and regulation of VLDL assembly/secretion.

Coleman, R.A.; Haynes, E.B.; Sand, T.M.; Davis, R.A.

1987-05-01

277

Influence of the polymer molecular weight on the microstructure of hybrid materials prepared by ?-irradiation  

NASA Astrophysics Data System (ADS)

Hybrid materials have been the object of intense research due to their potential for biomedical applications as well as in other fields. They are usually prepared by sol-gel but the method of gamma irradiation of the precursors is an alternative avoiding the addition of any other chemicals. The study of the hybrids prepared by this method has been progressing to understand the impact of different variables on the microstructure. In this work, the influence of the polymer?s molecular weight on the microstructure of the materials is investigated. Hybrids were obtained from a mixture of polydimethylsiloxane (PDMS) silanol terminated, tetraethylorthosilicate (TEOS) and zirconium propoxide (PrZr) in the wt% composition 20PDMS-73TEOS-7PrZr varying only the PDMS molecular weight. The obtained materials are homogeneous, transparent and flexible and their microstructure was analysed by Scanning Electron Microscopy (SEM) and Small-Angle Neutron Scattering (SANS). It was found that different microstructures were obtained, depending on the polymer molecular weight.

Lancastre, Joana J. H.; Falcão, António N.; Margaça, Fernanda M. A.; Ferreira, Luís M.; Miranda Salvado, Isabel M.; Casimiro, Maria H.; Almásy, László; Meiszterics, Anikó

2015-01-01

278

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

PubMed

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. PMID:24837922

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

279

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

PubMed

The glycosaminoglycan (GAG) heparin is a polyanionic sulfated polysaccharide most recognized for its anticoagulant activity. In the present study, the GAGs were extracted from bivalve mollusc Amussium pleuronectus. The crude GAGs were fractionated by ion-exchange (DEAE-cellulose and Amberlite IRA-900 & 120) chromatography. The recovered active fractions (as determined by metachromatic assay) were confirmed by agarose gel electrophoresis and the active fractions were purified in Sephadex G-100 column. Fractionated and purified GAG molecular weight was determined through gradient polyacrylamide gel electrophoresis. The structural characterization of low molecular weight GAG was analyzed by Fourier transform infrared spectroscopy. The activated partial thromboplastin time of purified GAG is 95 IU/mg and has molecular weight 6,500-7,500 Da. The disaccharide compositional analysis on the GAG sample was sulfated like porcine intestinal mucosal heparan sulfate, and it contains equivalent amount of uronic acid and hexosamine. The results of this study suggest that the GAG from A. pleuronectus could be an alternative source of heparin. PMID:19184547

Saravanan, R; Shanmugam, A

2010-03-01

280

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

PubMed

Dextrose equivalent (DE) value is the most common parameter used to characterize the molecular weight of maltodextrins. Its theoretical value is inversely proportional to number average molecular weight (M(n)), providing a theoretical basis for correlations with physical properties important to food manufacturing, such as: hygroscopicity, the glass transition temperature, and colligative properties. The use of freezing point osmometry to measure DE and M(n) was assessed. Measurements were made on a homologous series of malto-oligomers as well as a variety of commercially available maltodextrin products with DE values ranging from 5 to 18. Results on malto-oligomer samples confirmed that freezing point osmometry provided a linear response with number average molecular weight. However, noncarbohydrate species in some commercial maltodextrin products were found to be in high enough concentration to interfere appreciably with DE measurement. Energy dispersive spectroscopy showed that sodium and chloride were the major ions present in most commercial samples. Osmolality was successfully corrected using conductivity measurements to estimate ion concentrations. The conductivity correction factor appeared to be dependent on the concentration of maltodextrin. Equations were developed to calculate corrected values of DE and M(n) based on measurements of osmolality, conductivity, and maltodextrin concentration. This study builds upon previously reported results through the identification of the major interfering ions and provides an osmolality correction factor that successfully accounts for the influence of maltodextrin concentration on the conductivity measurement. The resulting technique was found to be rapid, robust, and required no reagents. PMID:19200083

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

2009-01-01

281

Hypoglycemic effect of polysaccharides with different molecular weight of Pseudostellaria heterophylla  

PubMed Central

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-1?, IL-2, IL-10, Leptin, TNF-?, 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-? 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

2013-01-01

282

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

PubMed

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. PMID:23151653

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

2013-01-01

283

Content and molecular-weight distribution of dietary fiber components in whole-grain rye flour and bread.  

PubMed

Content of dietary fiber and dietary fiber components in whole-grain rye (n = 18) were analyzed. The average total content, when fructan was included, was for dietary fiber 19.9% (range of 18.7-22.2%) and for extractable dietary fiber 7.4% (range of 6.9-7.9%). Arabinoxylan was the main dietary fiber component, with an average total content of 8.6%, followed by fructan (4.1%). During baking of whole-grain rye bread, only small changes in total content of arabinoxylan, arabinogalactan, and beta-glucan occurred, while the content of resistant starch increased and the content of fructan decreased in a baking-method-dependent manner. The molecular-weight distribution of extractable arabinoxylan in the flour was analyzed with a new method and ranged from 4 x 10(4) to 9 x 10(6) g/mol, with a weight average molecular weight of about 2 x 10(6) g/mol. During crisp bread making, only a limited degradation of arabinoxylan molecular weight was detected, while a notable degradation was observed in sour-dough bread. The molecular weight of extractable beta-glucan in the whole-grain rye flour ranged from 10(4) to 5 x 10(6) g/mol, with a weight average molecular weight of 0.97 x 10(6) g/mol. During bread making, the molecular weight of the beta-glucan was substantially degraded. PMID:19219994

Andersson, Roger; Fransson, Gunnel; Tietjen, Markus; Aman, Per

2009-03-11

284

Characterization of high-molecular-weight glutenin subunits from Eremopyrum bonaepartis and identification of a novel variant with unusual high molecular weight and altered cysteine residues.  

PubMed

We characterized two high-molecular-weight glutenin subunit (HMW-GS) variants from Eremopyrum bonaepartis, determined their complete open reading frames, and further expressed them in a bacterial system. The variants have many novel structural features compared with typical subunits encoded by Glu-1 loci: 1Fx3.7 and 1Fy1.5 exhibit hybrid properties of x- and y-type subunits. In addition, unusual molecular mass and altered number and distribution of cysteine residues were unique features of HMW-GSs encoded by Glu-F1 from E. bonaepartis. The mature 1Fx3.7 subunit has a full length of 1,223 amino acid residues, making it the largest subunit found thus far, while 1Fy1.5 is just 496 residues. In addition, the mutated PGQQ repeat motif was found in the repetitive region of 1Fx3.7. Although it has a similar molecular mass to that previously reported for 1Dx2.2, 1Dx2.2* and 1S(sh)x2.9 subunits, 1Fx3.7 appears to have had a different evolutionary history. The N-terminal and repetitive regions have a total of four additional cysteine residues, giving 1Fx3.7 a total of eight cysteines, while 1Fy1.5 has only six cysteines because the GHCPTSPQQ nonapeptide at the end of the repetitive region is deleted. With its extra cysteine residues and the longest repetitive region, features that are relevant to good wheat quality, the 1Fx3.7 subunit gene could be an excellent candidate for applications in wheat quality improvement. PMID:24395202

Jiang, Qian-Tao; Zhang, Xiao-Wei; Ma, Jian; Wei, Long; Zhao, Shan; Zhao, Quan-Zhi; Qi, Peng-Fei; Lu, Zhen-Xiang; Zheng, You-Liang; Wei, Yu-Ming

2014-04-01

285

Effects of the molecular weight and the degree of deacetylation of chitosan oligosaccharides on antitumor activity.  

PubMed

Effects of the degree of deacetylation (DDA) and the molecular mass of chitosan oligosaccharides (CTS-OS), obtained from the enzymatic hydrolysis of high molecular weight chitosan (HMWC), on antitumor activity was explored. The DDA and molecular weights of CTS-OS were determined by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-TOF MS) analysis. The CTS-OS were found to be a mixture of mainly dimers (18.8%), trimers (24.8%), tetramers (24.9%), pentamers (17.7%), hexamers (7.1%), heptamers (3.3%), and octamers (3.4%). The CTS-OS were further fractionated by gel-filtration chromatography into two major fractions: (1) COS, consisting of glucosamine (GlcN)(n), n = 3-5 with DDA 100%; and (2) HOS, consisting of (GlcN)(5) as the minimum residues and varying number of N-acetylglucosamine (GlcNAc)(n), n = 1-2 with DDA about 87.5% in random order. The cytotoxicities, expressed as the concentration needed for 50% cell death (CC(50)), of CTS-OS, COS, and HOS against PC3 (prostate cancer cell), A549 (lung cancer cell), and HepG2 (hepatoma cell), were determined to be 25 ?g·mL(-1), 25 ?g·mL(-1), and 50 ?g·mL(-1), respectively. The HMWC was approximately 50% less effective than both CTS-OS and COS. These results demonstrate that the molecular weight and DDA of chitosan oligosaccharides are important factors for suppressing cancer cell growth. PMID:21339986

Park, Jae Kweon; Chung, Mi Ja; Choi, Ha Na; Park, Yong Il

2011-01-01

286

Culture Conditions Affect the Molecular Weight Properties of Hyaluronic Acid Produced by Streptococcus zooepidemicus  

PubMed Central

The effect of five culture variables on the molecular weight properties of hyaluronic acid (HA) produced by Streptococcus zooepidemicus was studied in batch culture with a complex medium containing glucose and 10 g of yeast extract per liter. Neither the culture pH (pH 6.3 to 8.0) nor the agitation speed (300 to 1,000 rpm) affected the weight-average molecular weight (M(infw)) of HA under anaerobic conditions at 37(deg)C when 20 g of glucose per liter was used initially. M(infw) was in the narrow range of 1.5 x 10(sup6) to 2.3 x 10(sup6), and polydispersity (P) was between 1.8 and 2.5. When S. zooepidemicus was grown at lower temperatures or with aeration, higher-molecular-weight polymer and increased yields were observed. The polydispersity, however, remained unaffected. Anaerobically, the mean M(infw) (based on three samples taken within 4 h of glucose exhaustion) was (2.40 (plusmn) 0.10) x 10(sup6) and (1.90 (plusmn) 0.05) x 10(sup6) at 32 and 40(deg)C respectively. Aeration of the culture at 1 vol/vol/min produced HA with mean M(infw) of (2.65 (plusmn) 0.05) x 10(sup6) compared with (2.10 (plusmn) 0.10) x 10(sup6) under equivalent anaerobic conditions. The initial glucose concentration had the most pronounced effect on polymer characteristics. Increasing this concentration from 20 to 40 g/liter produced HA with mean M(infw) of (3.1 (plusmn) 0.1) x 10(sup6) at 1-vol/vol/min aeration. The molecular weight of HA also exhibited time dependency, with smaller chains (M(infw), ca. 2.5 x 10(sup6)) detected early in the culture time course, rising to a maximum (M(infw), 3.2 x 10(sup6)) in the late exponential phase of growth. The mean polydispersity was also greater (2.7 (plusmn) 0.1) under these conditions. Replicate experiments performed under conditions resulting in the lowest (40(deg)C, anaerobic) and highest (40 g of glucose per liter, 1-vol/vol/min aeration)-M(infw) polymer demonstrated excellent experimental reproducibility. PMID:16535649

Armstrong, D. C.; Johns, M. R.

1997-01-01

287

Accurate static and dynamic properties of liquid-electrolytes for Li-ion batteries from ab initio molecular dynamics  

SciTech Connect

Lithium-ion batteries have the potential to revolutionize the transportation industry, as they did for wireless communication. A judicious choice of the liquid electrolytes used in these systems is required to achieve a good balance among high-energy storage, long cycle life and stability, and fast charging. Ethylene-carbonate (EC) and propylene-carbonate (PC) are popular electrolytes. However, to date, almost all molecular-dynamics simulations of these fluids rely on classical force fields, while a complete description of the functionality of Li-ion batteries will eventually require quantum mechanics. We perform accurate ab initio molecular-dynamics simulations of ethylene- and propylene-carbonate with LiPF6 at experimental concentrations to build solvation models which explain available neutron scattering and nuclear magnetic resonance (NMR) results and to compute Li-ion solvation energies and diffusion constants. Our results suggest some similarities between the two liquids as well as some important differences. Simulations also provide useful insights into formation of solid-electrolyte interphases in the presence of electrodes in conventional Li-ion batteries.

Ganesh, Panchapakesan [ORNL; Jiang, Deen [ORNL; Kent, Paul R [ORNL

2011-01-01

288

Molecular Characterization and Diagnostic Value of Taenia solium Low-Molecular-Weight Antigen Genes  

PubMed Central

Neurocysticercosis (NCC) caused by infection with the larvae of Taenia solium is an important cause of neurological disease worldwide. In order to establish an enzyme-linked immunosorbent assay (ELISA) for this infection using recombinant proteins, we carried out molecular cloning and identified four candidates as diagnostic antigens (designated Ag1, Ag1V1, Ag2, and Ag2V1). Except for Ag2V1, these clones could encode a 7-kDa polypeptide, and Ag2V1 could encode a 10-kDa polypeptide. All of the clones were very similar. Except for Ag2V1, recombinant proteins were successfully expressed using an Escherichia coli expression system. Immunoblot analysis of NCC patient sera detected recombinant proteins, but because reactivity to recombinant Ag1 was too weak, Ag1 was not suitable as an immunodiagnostic antigen. So, Ag1V1 and Ag2 were chosen as ELISA antigens, and the Ag1V1/Ag2 chimeric protein was expressed. Of 49 serum samples from NCC patients confirmed to be seropositive by immunoblot analysis, 44 (89.7%) were positive by ELISA. No assays of serum samples from patients with other parasitic infections recognized the Ag1V1/Ag2 chimeric protein. The Ag1V1/Ag2 chimeric protein obtained in this study had a high value for differential immunodiagnosis. PMID:11101577

Sako, Yasuhito; Nakao, Minoru; Ikejima, Takashi; Piao, Xian Zhi; Nakaya, Kazuhiro; Ito, Akira

2000-01-01

289

Manifestation of sub-Rouse modes in flow at the surface of low molecular weight polystyrene  

E-print Network

The presence of a viscoelastic mechanism distinctly different from the segmental a-relaxation and the Rouse modes within the glass-rubber transition zone of polymers had been justified by theoretical considerations, and subsequently experimentally verified in different bulk polymers by various techniques, and in several laboratories. Referred to in the literature as the sub-Rouse modes, they were also found in polymer thin films by the creep compliance measurements of McKenna and co-workers Established by experiment and theoretical considerations is the enhanced mobility of sub-Rouse modes in thin PS films by the combination of effect from the free surface, finite size, and induced chain orientations, concomitant with the segmental a-relaxation. Induced chain orientations effect is present only when h is less than the end-to-end distance of the high molecular weight polymer chains. In this paper, the proven enhanced mobility of sub-Rouse modes at the surface of polymers is used to explain recent experimental investigations of viscous flow at the surface of low molecular weight PS by Chai et al. [Science, 343, 994 (2014)], and by Yang et al. [Science, 328, 1676 (2010).]. Viscous flow of polymers is by global chain motion, therefore the observed large reduction of viscosity at the surface of low molecular weight PS originates from the sub-Rouse modes, and not the segmental a-relaxation. This distinction is not commonly recognized in the current literature. The accerleration of the sub-Rouse modes at the surface explains the experimental findings.

K. L. Ngai; S. Capaccioli; Daniele Prevosto; Luigi Grassia

2014-10-17

290

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

291

Extraction of High Molecular Weight Genomic DNA from Soils and Sediments  

PubMed Central

The soil microbiome is a vast and relatively unexplored reservoir of genomic diversity and metabolic innovation that is intimately associated with nutrient and energy flow within terrestrial ecosystems. Cultivation-independent environmental genomic, also known as metagenomic, approaches promise unprecedented access to this genetic information with respect to pathway reconstruction and functional screening for high value therapeutic and biomass conversion processes. However, the soil microbiome still remains a challenge largely due to the difficulty in obtaining high molecular weight DNA of sufficient quality for large insert library production. Here we introduce a protocol for extracting high molecular weight, microbial community genomic DNA from soils and sediments. The quality of isolated genomic DNA is ideal for constructing large insert environmental genomic libraries for downstream sequencing and screening applications. The procedure starts with cell lysis. Cell walls and membranes of microbes are lysed by both mechanical (grinding) and chemical forces (?-mercaptoethanol). Genomic DNA is then isolated using extraction buffer, chloroform-isoamyl alcohol and isopropyl alcohol. The buffers employed for the lysis and extraction steps include guanidine isothiocyanate and hexadecyltrimethylammonium bromide (CTAB) to preserve the integrity of the high molecular weight genomic DNA. Depending on your downstream application, the isolated genomic DNA can be further purified using cesium chloride (CsCl) gradient ultracentrifugation, which reduces impurities including humic acids. The first procedure, extraction, takes approximately 8 hours, excluding DNA quantification step. The CsCl gradient ultracentrifugation, is a two days process. During the entire procedure, genomic DNA should be treated gently to prevent shearing, avoid severe vortexing, and repetitive harsh pipetting. PMID:19904232

Lee, Sangwon; Hallam, Steven J.

2009-01-01

292

Molecular weight of barley ?-glucan influences energy expenditure, gastric emptying and glycaemic response in human subjects.  

PubMed

Barley ?-glucan (BG) has been shown to reduce glycaemic response (GR) in some studies. It is hypothesised that this reduction may be a function of its physical properties that delay gastric emptying (GE). The effect of these changes in GR and GE on diet-induced thermogenesis (DIT) is not known. The aim of the present study was to assess the effect of BG of different molecular weights and purities on GR, GE and DIT in healthy subjects. This was a randomised, single-blind, repeated-measures design where fifteen healthy subjects were tested on three occasions following an overnight fast. Following the baseline measurements, the volunteers were fed a soup containing high-molecular-weight BG (HBG), a soup containing low-molecular-weight BG (LBG) or a control soup with no BG (CHO). Following the consumption of the breakfast, GR was measured using finger-prick blood samples, GE was determined using the 13C-octanoic acid breath test and DIT was measured using indirect calorimetry. There was a difference in GR AUC between the soups after 60 min but not after 120 min. The CHO and LBG meals had a greater GR than the HBG meal. There were differences in all GE time points, with the HBG meal having the slowest GE time. There was a correlation between the GR and the initial GE times. There were differences in total DIT between the three test meals with the HBG meal having the lowest DIT. The present study indicates that HBG has the ability to delay GE due to increased viscosity, resulting in a decreased GR and DIT. PMID:23742725

Thondre, P S; Shafat, A; Clegg, M E

2013-12-01

293

High molecular weight hyaluronan mediates the cancer resistance of the naked mole-rat  

PubMed Central

The naked mole-rat displays exceptional longevity, with a maximum lifespan exceeding 30 years1–3. This is the longest reported lifespan for a rodent species and is especially striking considering the small body mass of the naked mole-rat. In comparison, a similarly sized house mouse has a maximum lifespan of 4 years4,5. In addition to their longevity, naked mole-rats show an unusual resistance to cancer. Multi-year observations of large naked mole-rat colonies did not detect a single incidence of cancer2,6. Here we identify a mechanism responsible for the naked mole-rat’s cancer resistance. We found that naked mole-rat fibroblasts secrete extremely high molecular weight hyaluronan (HA), which is over five times larger than human or mouse HA. This high molecular weight HA accumulates abundantly in naked mole rat tissues due to the decreased activity of HA-degrading enzymes and a unique sequence of hyaluronan synthase 2 (HAS2). Furthermore, the naked mole-rat cells are more sensitive to HA signaling, as the naked mole rat cells have a higher affinity to HA than the mouse or human cells. Perturbation of the signaling pathways sufficient for malignant transformation of mouse fibroblasts fails to transform naked mole-rat cells. However, once high molecular weight HA is removed by either knocking down HAS2 or overexpressing the HA-degrading enzyme, Hyal2, naked mole-rat cells become susceptible to malignant transformation and readily form tumors in mice. We speculate that naked mole-rats have evolved a higher concentration of HA in the skin to provide skin elasticity needed for life in underground tunnels. This trait may have then been co-opted to provide cancer resistance and longevity to this species. PMID:23783513

Tian, Xiao; Azpurua, Jorge; Hine, Christopher; Vaidya, Amita; Myakishev-Rempel, Max; Ablaeva, Julia; Mao, Zhiyong; Nevo, Eviatar; Gorbunova, Vera; Seluanov, Andrei

2013-01-01

294

Cold flow tudy of a fluidized bed reactor for catalytic conversion of methanol to low molecular weight hydrocarbons  

E-print Network

COLD FLOW STUDY OF A FLUIDIZED BED REACTOR FOR CATALYTIC CONVERSION OF METHANOL TO LOW MOLECULAR WEIGHT HYDROCAREONS A Thesis by SHIRISH RAMNIKLAL MEHTA Submitted to the Graduate College of Texas A&M University in partial fulfilment... of the requirement for the degree of MASTER OF SCIENCE March 1982 Major Subject: Chemical Engineering COLD FLOW STUDY OF A FLUIDIZED BED REACTOR FOR CATALYTIC CONVERSION OF METHANOL TO LOW MOLECULAR WEIGHT HYDROCARBON A Thesis by SHIRISH RAMNIKLAL MEHTA...

Mehta, Shirish Ramniklal

1982-01-01

295

Method for determining the amylose content, molecular weights, and weight- and molar-based distributions of degree of polymerization of amylose and fine-structure of amylopectin  

Microsoft Academic Search

Cooked rice texture and other aspects of rice starch functionality are influenced by amylose and amylopectin content and structure. A method is described that uses high performance size exclusion chromatography coupled with multiangle laser light scattering and refractive index detectors to determine amylose content, molecular mass of amylose and the weight- and molar-based distributions of degree of polymerization (DP) of

Ming-Hsuan Chen; Christine J. Bergman

2007-01-01

296

Multiplex-PCR typing of high molecular weight glutenin alleles in wheat  

Microsoft Academic Search

In Australian commercial cultivars, each high molecular weight glutenin (Glu-1) homoeologous locus consists of one of two predominant alleles: Glu-A1a (subunit Ax1) or Glu-A1b (subunit Ax2*) at the GluA1 locus, Glu-B1b (Bx7 and By8 subunits) or Glu-B1i (Bx17 and By18 subunits) at the Glu-B1 locus, and Glu-D1d (Dx5 and Dy10 subunits) or Glu-D1a (Dx2 and Dy12 subunits) at the Glu-D1

W. Ma; W. Zhang; K. R. Gale

2003-01-01

297

Dense-gas chromatography of nonvolatile substances of high molecular weight.  

PubMed

Working at pressures of up to 2000 atmospheres, more than ten times higher than in previous gas chromatography, we used the solvent power of dense gases to enable migration of chromatographic substances of molecular weights as high as 400,000. Carotenoids, corticol steroids, sterols, nucleosides, amino acids, carbohydrates, and several polymers have been caused to migrate, separated, and detected in NH(3) and CO(2) carrier gases at temperatures of 140 degrees and 40 degrees C, just above the respective critical points. Previously such compounds either defied separation by gas chromatography or had to be chromatographed as their more volatile derivatives. PMID:5634909

McLaren, L; Myers, M N; Giddings, J C

1968-01-12

298

Total internal reflection ellipsometry and SPR detection of low molecular weight environmental toxins  

NASA Astrophysics Data System (ADS)

The environmental toxins, such as herbicides simazine and atrazine, and T2 mycotoxin were registered with the optical methods of surface plasmon resonance (SPR) and recently developed total internal reflection ellipsometry (TIRE). The immune assay approach was exploited for in situ registration of the above low molecular weight toxins with specific antibodies immobilised onto the gold surface via (poly)allylamine hydrochloride layer using electrostatic self-assembly (ESA) technique. The comparison of two methods of SPR and TIRE shows a higher sensitivity of the latter.

Nabok, A. V.; Tsargorodskaya, A.; Hassan, A. K.; Starodub, N. F.

2005-06-01

299

Antioxidation activities of low-molecular-weight gelatin hydrolysate isolated from the sea cucumber Stichopus japonicus  

Microsoft Academic Search

Gelatin extracted from the body wall of the sea cucumber (Stichopus japonicus) was hydrolyzed with flavourzyme. Low-molecular-weight gelatin hydrolysate (LMW-GH) of 700–1700 Da was produced using an\\u000a ultrafiltration membrane bioreactor system. Chemiluminescence analysis revealed that LMW-GH scavenges high free radicals in\\u000a a concentration-dependent manner; IC50 value for superoxide and hydroxyl radicals was 442 and 285 ?g mL?1, respectively. LMW-GH exhibited

Jingfeng Wang; Yuming Wang; Qingjuan Tang; Yi Wang; Yaoguang Chang; Qin Zhao; Changhu Xue

2010-01-01

300

Rheological Properties of Gels from Pyrene Based Low Molecular Weight Gelators  

SciTech Connect

Gels of pyrene derived low molecular weight organogelators (LMOGs) in primary alcohols have been characterized by rheometry and scanning electron microscopy. Total gelator concentration was 1-2.7 % w/w depending on the solvent and the gelator, including equimolar amounts of the gelator and 2,4,7-trinitrofluorenone (TNF), which is necessary for gelation. Thermoreversible and strongly shear thinning gels were achieved as the two components interact non-covalently to form a gel network. A qualitative correlation between the rheological properties and the nanoscale gel structure were found.

Leivo, Kimmo T.; Hahma, Arno P. [University of Jyvaeskylae, Department of Chemistry, Survontie 9, 40500 Jyvaeskylae (Finland)

2008-07-07

301

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

PubMed

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

Azizo?lu, Selimcan; Kizilel, Riza; Maruši?, Maja; Kavakli, Ibrahim Halil; Erman, Burak; Kizilel, Seda

2013-07-01

302

Effects of molecular weights on the absorption, distribution and urinary excretion of intraperitoneally administrated carboxymethyl chitosan in rats.  

PubMed

Carboxymethyl chitosan (CM-chitosan) is one of water-soluble derivatives of chitosan. Numerous studies have been focused on its applications as pharmaceutical excipient, bioactive reagent and nontoxic drug carrier. Like other polysaccharides, CM-chitosan is inhomogenous in molecular weight. Originations and preparation procedures considerably influence its molecular weight and molecular weight distributions. Understanding the molecular weight related biological behaviour of this inhomogenous glycopolymer in vivo were crucial for the quality control and clinical applications of chitosan and chitosan based medical devices. In this study, we investigated the effects of molecular weights on the absorption, distribution, degradation and urinary excretion of the fluorescein isothiocyanate-labeled CM-chitosan in rats. The results indicated that molecular weight significantly influenced the uptake of CM-chitosan from the lumen of abdomen and blood vessels to peripheral tissues, the distribution of this chemical and urinary excretion after intraperitoneal administration. These findings provided an important reference for the clinical applications of this versatile derivative of chitosan as postsurgical and other biomedical materials and important clues for the exploitation of CM-chitosan based drug targeting and delivery systems. PMID:22890521

Dong, Wen; Han, Baoqin; Shao, Kai; Yang, Zhao; Peng, Yanfei; Yang, Yan; Liu, Wanshun

2012-12-01

303

The dependency of solute diffusion on molecular weight and shape in intact bone  

PubMed Central

Solute transport through the bone lacunar-canalicular system (LCS) is essential for osteocyte survival and function, but quantitative data on the diffusivity of various biological molecules in the LCS are scarce. Using our recently developed approach based on fluorescence recovery after photobleaching (FRAP), diffusion coefficients of five exogenous fluorescent tracers (sodium fluorescein, dextran-3k, dextran-10k, parvalbumin, and ovalbumin) were measured in murine tibiae in situ. These tracers were chosen to test the dependency of solute diffusion on molecular weight (376–43,000 Da) and shape (linear vs. globular). Among the five tracers, no fluorescence recovery (and thus mobility) was detected for dextran-10k and the diffusion coefficients (DLCS) of the other four tracers were 295±46, 128±32, 157±88, 65±21 µm2s?1 in the LCS, respectively. Overall, the rate of solute diffusion in the bone LCS showed strong dependency on molecular size and shape. Diffusivity decreased with increasing molecular weight for both linear and globular molecules, with the linear molecules decreasing at a faster rate. Compared with free diffusion (Dfree) in aqueous solutions, the relative diffusivities (DLCS/Dfree) of the four tracers were not significantly different for sodium fluorescein, dextran-3k, parvalbumin, and ovalbumin (55±8.6%, 68.1±17.0%, 79.7±44.7%, 61.0±19.6%, respectively). This result did not agree with the homogenous molecular sieve model proposed for the osteocytic pericellular matrix structure. Instead, a heterogeneous porous model of the pericellular matrix may account for the observed solute transport in the LCS. In summary, the present study provides quantitative data on diffusion of various nutrients and signaling molecules in the LCS that are important for bone metabolism and mechanotrusduction. PMID:19647808

Li, Wen; You, Lidan; Schaffler, Mitchell B.; Wang, Liyun

2009-01-01

304

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

PubMed

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

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

2014-11-10

305

Gas separation properties of carbon molecular sieve membranes derived from polyimide\\/polyvinylpyrrolidone blends: effect of the molecular weight of polyvinylpyrrolidone  

Microsoft Academic Search

Carbon molecular sieve (CMS) membranes were prepared using aromatic polyimide (PI) and polyvinylpyrrolidone (PVP) polymer blends. The characteristics of the carbon structures and the gas permeation properties of the CMS membranes pyrolyzed at 500 and 700°C were investigated in terms of the molecular weight of PVP (the thermally labile polymer). The PI\\/PVP blend showed two separate thermal decomposition steps. In

Youn Kook Kim; Ho Bum Park; Young Moo Lee

2005-01-01

306

Hydrophilic Polyester Microspheres: Effect of Molecular Weight and Copolymer Composition on Release of BSA  

PubMed Central

ABSTRACT Purpose To study the release of a model protein, bovine serum albumin (BSA), from microspheres of an hydroxylated aliphatic polyester, poly(lactic-co-hydroxymethyl glycolic acid) (PLHMGA). Methods BSA-loaded microspheres were prepared by a double emulsion solvent evaporation method. The effect of copolymer composition and the molecular weight of the copolymer on in vitro release and degradation were studied. The integrity of the released BSA was studied by fluorescence spectroscopy and size exclusion chromatography (SEC). Results Microspheres prepared from PLHMGA with 50% hydroxymethyl glycolic acid (HMG) showed a burst release followed by a sustained release in 5–10 days. PLHMGA microspheres prepared from a copolymer with 35% and 25% HMG showed a sustained release of BSA up to 80% for 30 and 60 days, respectively. The release of BSA was hardly affected by the molecular weight of the polymer. Fluorescence spectroscopy and SEC showed that the released BSA preserved its structural integrity. Microspheres were fully degradable, and the degradation time increased from ~20 days to 60 days when the HMG content decreased from 50% to 25%. Conclusions Taking the degradation and release data together, it can be concluded that the release of BSA from PLHMGA microspheres is governed by degradation of the microspheres. PMID:20602152

Ghassemi, Amir H.; van Steenbergen, Mies J.; Talsma, Herre; van Nostrum, Cornelus F.; Crommelin, Daan J. A.

2010-01-01

307

Impact of Molecular Weight on Lymphatic Drainage of a Biopolymer-Based Imaging Agent  

PubMed Central

New lymphatic imaging technologies are needed to better assess immune function and cancer progression and treatment. Lymphatic uptake depends mainly on particle size (10–100 nm) and charge. The size of carriers for imaging and drug delivery can be optimized to maximize lymphatic uptake, localize chemotherapy to lymphatic metastases, and enable visualization of treatment deposition. Toward this end, female BALB/c mice were injected subcutaneously in the hind footpad or forearm with a series of six different molecular weight hyaluronan (HA) near-infrared dye (HA-IR820) conjugates (ca. 5–200 nm). Mice were imaged using whole body fluorescent imaging over two weeks. HA-IR820 fluorescence was clearly visualized in the draining lymphatic capillaries, and in the popliteal and iliac or axillary lymph nodes. The 74-kDa HA-IR820 had the largest lymph node area-under-the-curve. In contrast to prior reports, mice bearing limb tumors exhibited three-fold longer retention of 74-kDa HA-IR820 in the popliteal node compared to mice without tumors. HA conjugate kinetics and disposition can be specifically tailored by altering their molecular weight. The specific lymphatic uptake and increased nodal retention of HA conjugates indicate significant potential for development as a natural biopolymer for intralymphatic drug delivery and imaging. PMID:24300232

Bagby, Taryn R.; Cai, Shuang; Duan, Shaofeng; Thati, Sharadvi; Aires, Daniel J.; Forrest, Laird

2012-01-01

308

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

PubMed

The standard process for preparing the low-molecular-weight heparin (LMWH) tinzaparin, through the partial enzymatic depolymerization of heparin, results in a reduced yield because of the formation of a high content of undesired disaccharides and tetrasaccharides. An enzymatic ultrafiltration reactor for LMWH preparation was developed to overcome this problem. The behavior, of the heparin oligosaccharides and polysaccharides using various membranes and conditions, was investigated to optimize this reactor. A novel product, LMWH-II, was produced from the controlled depolymerization of heparin using heparin lyase II in this optimized ultrafiltration reactor. Enzymatic ultrafiltration provides easy control and high yields (>80%) of LMWH-II. The molecular weight properties of LMWH-II were similar to other commercial LMWHs. The structure of LMWH-II closely matched heparin's core structural features. Most of the common process artifacts, present in many commercial LWMHs, were eliminated as demonstrated by 1D and 2D nuclear magnetic resonance spectroscopy. The antithrombin III and platelet factor-4 binding affinity of LMWH-II were comparable to commercial LMWHs, as was its in vitro anticoagulant activity. PMID:24634007

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

2014-05-01

309

The Effect of Ozonolysis on the Freezing of Water Catalyzed by High Molecular Weight Organic Compounds  

NASA Astrophysics Data System (ADS)

High altitude clouds may be impacted by the products of biomass burning which can be lofted into the upper troposphere through deep convection. Some high molecular weight organic compounds are efficient ice nucleators (e.g. long chain alcohols) while others are not (e.g. long chain alkanes). To further complicate the picture, once in the atmosphere organic compounds may be transformed through oxidation and photochemistry, which could change their characteristics as freezing catalysts. To develop a deeper understanding of these processes, we observed the freezing temperatures of pure water droplets covered by high molecular weight organic compounds before and after exposure to ozone. Oleic acid and oleyl alcohol, which have carbon-carbon double bonds at approximately the same position along the backbone of the molecule, display very different behaviors. The mean freezing temperature for oleic acid is unchanged after exposure to ozone while that for oleyl alcohol increases by approximately 4 K. These changes will be compared to the structure of the film that the compounds form at the water surface. We will also present results of experiments with alkenes.

Irish, S.; Cantrell, W.

2006-12-01

310

The integrity of welded interfaces in ultra-high molecular weight polyethylene: Part 2--interface toughness.  

PubMed

In Part 2 of a study of welding of ultra-high molecular weight polyethylene (UHMWPE), experiments were conducted to measure the interfacial fracture energy of butt welds, for various welding times and temperatures above the melting point. Their toughness was investigated at 37 degrees C in terms of their fracture energy, obtained by adapting the essential work of fracture (EWF) method. However, a proportion of the welded samples (generally decreasing with increasing welding time or temperature) failed in dual ductile/brittle mode, hence invalidating the EWF test. Even those failing in purely ductile mode showed a measurable interface work of fracture only for the highest weld temperature and time: 188 degrees C and 90 min. Results from the model presented in Part 1 show that this corresponds to the maximum reptated molecular weight reaching close to the peak in the molar mass distribution. Hence this work provides the first experimental evidence that the slow rate of self-diffusion in UHMWPE leads to welded interfaces acting as low-toughness crack paths. Since such interfaces exist around every powder particle in processed UHMWPE this problem cannot be avoided, and it must be accommodated in design of hip and knee bearing surfaces made from this polymer. PMID:16574221

Haughie, David W; Buckley, C Paul; Wu, Junjie

2006-07-01

311

Structural Characterization of the Symbiotically Important Low-Molecular-Weight Succinoglycan of Sinorhizobium meliloti  

PubMed Central

The production of succinoglycan by Sinorhizobium meliloti Rm1021 is required for successful nodule invasion by the bacterium of its host plant, alfalfa. Rm1021 produces succinoglycan, an acidic exopolysaccharide composed of an octasaccharide repeating unit modified with acetyl, succinyl, and pyruvyl moieties, in both low- and high-molecular-weight forms. Low-molecular-weight (LMW) succinoglycan, previously thought to consist of monomers, trimers, and tetramers of the repeating unit, has been reported as being capable of promoting the formation of nitrogen-fixing nodules by succinoglycan-deficient derivatives of strain Rm1021. We have determined that the three size classes of LMW succinoglycan species are in fact monomers, dimers, and trimers of the repeating unit and that the trimer is the species active in promoting nodule invasion. A detailed structural analysis of the components of LMW succinoglycan by using various chromatographic techniques, along with nuclear magnetic resonance analyses, has revealed that there is considerable heterogeneity within the LMW succinoglycan oligomers in terms of noncarbohydrate substitutions, and we have determined the structural basis of this heterogeneity. PMID:10542182

Wang, Lai-Xi; Wang, Ying; Pellock, Brett; Walker, Graham C.

1999-01-01

312

Partial Hydrothermal Oxidation of High Molecular Weight Unsaturated Carboxylic Acids for Upgrading of Biodiesel Fuel  

NASA Astrophysics Data System (ADS)

With increasing environmental awareness and crude oil price, biodiesel fuel (BDF) is gaining recognition as a renewable fuel which may be used as an alternative diesel fuel without any modification to the engine. The cold flow and viscosity of BDF, however, is a major drawback that limited its use in cold area. In this study, therefore, we investigated that partial oxidation of high molecular weight unsaturated carboxylic acids in subcritical water, which major compositions in BDF, to upgrade biodiesel fuel. Oleic acid, (HOOC(CH2)7CH=CH(CH2)7CH3), was selected as a model compound of high molecular weight unsaturated carboxylic acids. All experiments were performed with a batch reactor made of SUS 316 with an internal volume of 5.7 cm3. Oleic acid was oxidized at 300 °C with oxygen supply varying from 1-10 %. Results showed that a large amount of carboxylic acids and aldehydes having 8-9 carbon atoms were formed. These experimental results suggest that the hydrothermal oxidative cleavage may mainly occur at double bonds and the cleavage of double bonds could improve the cold flow and viscosity of BDF.

Kawasaki, K.; Jin, F.; Kishita, A.; Tohji, K.; Enomoto, H.

2007-03-01

313

Assembly and Characterization ofWell-DefinedHigh-Molecular-Weight Poly(p-phenylene) Polymer Brushes  

SciTech Connect

The assembly and characterization of well-de ned, end-tethered poly- (p-phenylene) (PPP) brushes having high molecular weight, low polydispersity and high 1,4-stereoregularity are presented. The PPP brushes are formed using a precursor route that relies on either self-assembly or spin coating of high molecular weight (degrees of poly- merizations 54, 146, and 238) end-functionalized poly(1,3-cyclohexadiene) (PCHD) chains from benzene solutions onto silicon or quartz substrates, followed by aromatization of the end-attached PCHD chains on the surface. The approach allows the thickness (grafting density) of the brushes to be easily varied. The dry brushes before and after aromatization are characterized by ellipsometry, atomic force microscopy, grazing angle attenuated total re ectance Fourier transform infrared spectroscopy, and UV-Vis spectros- copy. The properties of the PPP brushes are compared with those of lms made using oligo- paraphenylenes and with ab initio density functional theory simulations of optical proper- ties. Our results suggest conversion to fully aromatized, end-tetheredPPPpolymerbrusheshaving eective conjugation lengths of 5 phenyl units.

Chen, Jihua [ORNL; Dadmun, Mark D [ORNL; Mays, Jimmy [ORNL; Messman, Jamie M [ORNL; Hong, Kunlun [ORNL; Britt, Phillip F [ORNL; Sumpter, Bobby G [ORNL; Alonzo Calderon, Jose E [ORNL; Kilbey, II, S Michael [ORNL; Ankner, John Francis [ORNL; Bredas, Jean-Luc E [ORNL; Malagoli, Massimo [ORNL; Deng, Suxiang [ORNL; Swader, Onome A [ORNL; Yu, Xiang [ORNL

2011-01-01

314

Molecular weight dependence of the morphology in P3HT:PCBM solar cells.  

PubMed

In polymer-based photovoltaic devices, optimizing and controlling the active layer morphology is important to enhancing the device efficiency. Using poly(3-hexylthiophene) (P3HT) with well-defined molecular weights (MWs), synthesized by the Grignard metathesis (GRIM) method, we show that the morphology of the photovoltaic active layer and the absorption and crystal structure of P3HT are dependent on the MW. Differential scanning calorimetry showed that the crystallinity of P3HT reached a maximum for intermediate MWs. Grazing-incidence wide-angle X-ray diffraction showed that the spacing of the (100) planes of P3HT increased with increasing MW, while the crystal size decreased. Nonlinear crystal lattice expansions were found for both the (100) and (020) lattice planes, with an unusual ?-?-stacking enhancement observed between 50 and 100 °C. The melting point depression for P3HT, when mixed with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), and, hence, the Flory-Huggins interaction parameter depended on the MW. PCBM was found to perturb the ordering of P3HT chains. In photovoltaic devices, P3HT with a MW of ?20K showed the best device performance. The morphologies of these blends were studied by grazing-incidence small-angle X-ray scattering (GISAXS) and resonant soft X-ray scattering. In GISAXS, we observed that the low-molecular-weight P3HT more readily crystallizes, promoting a phase-separated morphology. PMID:25350382

Liu, Feng; Chen, Dian; Wang, Cheng; Luo, Kaiyuan; Gu, Weiyin; Briseno, Alejandro L; Hsu, Julia W P; Russell, Thomas P

2014-11-26

315

Solvent Annealing Strategies for the Self-Assemblty of Low Molecular Weight Block Copolymers  

NASA Astrophysics Data System (ADS)

Templated self-assembly of block copolymer (BCP) films is of intrest for lithographic applications. As the drive for smaller features continues, we explore the extensibility of block copolymer microphase separation towards smaller periods in a series of low molecular weight (5 -15 kg/mol) poly(styrene-b-dimethylsiloxane) (PS-PDMS) diblock copolymers. This material exhibits a large segmental Flory-Huggins interaction parameter ( 0.26), enabling microphase separation with a periodicity of <10 nm in 5kg/mol PS- PDMS at room temperature. One of the challenges in low molecular weight systems is to obtain self-assembly while avoiding dewetting. Here we describe the use of solvent annealing and substrate functionalization processes to accomplish microphase separation. We also discuss the use of mixed solvents to selectively swell different blocks of the copolymer resulting in a change in the final morphology of the self-assembled features, e.g. a cylindrical-morphology BCP forming perforated lamellae.

Gotrik, Kevin; Jung, Yeon Sik; Son, Jeong Gon; Ross, Caroline

2010-03-01

316

Seasonal Variations of Low Molecular Weight Dicarboxylic Acids in Atmospheric Aerosols at Okinawa Islands, Japan  

NASA Astrophysics Data System (ADS)

Low molecular weight dicarboxylic acids are major fraction of water soluble organic compounds in the atmospheric aerosols. Recently, economy of East Asia grows up remarkably, and atmospheric aerosols discharged from this area have been transported to Japan. In this study, we collected aerosol at Cape Hedo (CH) and University of the Ryukyus(UR), and studied the distribution and origin of low molecule dicarboxylic acid. Aerosols were collected on a quartz filter with a high volume air sampler. Low molecular weight dicarboxylic acids extracted by pure water were derivatized to dibutyl esters by reactions with BF3/butanol and were measured by GC-FID. In many samples, oxalic acid showed the highest concentration. Concentration of oxalic acid, malonic acid, succinic acid and malic acid were strongly correlated between the two sampling sites. Oxalic acid occupied on the average 83% and 76% of all the dicarboxylic acid measured for CH samples and UR samples. It is suggested that the aerosols in Okinawa were affected by secondary photochemical reactions, not by the primary emissions from local sources. The seasonal variation of the dicarboxylic acids concentrations in CH and UR showed higher in spring and fall, and a lower in summer. From the back trajectory analysis, dicarboxylic acids concentrations showed higher when an air mass came from East Asia area, and showed lower when it came from Pacific Ocean.

Nakaema, F.; Handa, D.; Tanahara, A.; Arakaki, T.

2009-04-01

317

Comparative study of two ATP : L-arginine phosphotransferases of molecular weight 84 000.  

PubMed

Solen ensisensis muscle arginine kinase (ATP : L-arginine phosphotransferase, EC 2.7.3.3) was isolated in an homogeneous state. Its molecular weight was found to be about 80 000. The properties of this enzyme were compared with those of arginine kinase from Sipunculus nudus, an enzyme which also has a molecular weight of about 80 000. Both enzymes have several reactive thiol groups (8 thiol groups in the Solen kinase and 12 in the Sipunculus enzyme were titrateable with 5,5'-dithio-bis-(2-nitrobenzoic) acid and histidine residues (both enzymes have 6 reactive histidine residues). These kinases were, therefore, highly susceptible to oxidation. Both enzymes show the same pH optimum and absolute specificity towards the guanidine substrate, L-arginine. The reaction kinetics of both enzymes are of the sequential type. In the presence of alpha-aminoacids of Mg2+-ADP, similar spectral effects were obtained. The enzymes differ in their enzymic activities and in their rate of recovery following urea denaturation. The most important difference that appeared to be a special feature of the Sipunculus enzyme is that the spectrum of the Mg2+-ADP-enzyme complex is strongly intensified by L-arginine. PMID:164227

Thiem, N V; Lacombe, G; Thoai, N V

1975-01-23

318

Occupational Asthma: New Low-Molecular-Weight Causal Agents, 2000–2010  

PubMed Central

Background. More than 400 agents have been documented as causing occupational asthma (OA). The list of low-molecular-weight (LMW) agents that have been identified as potential causes of OA is constantly expanding, emphasizing the need to continually update our knowledge by reviewing the literature. Objective. The objective of this paper was to identify all new LMW agents causing occupational asthma reported during the period 2000–2010. Methods. A Medline search was performed using the keywords occupational asthma, new allergens, new causes, and low-molecular-weight agents. Results. We found 39 publications describing 41 new LMW causal agents, which belonged to the following categories: drugs (n = 12), wood dust (n = 11), chemicals (n = 8), metals (n = 4), biocides (n = 3), and miscellaneous (n = 3). The diagnosis of OA was confirmed through SIC for 35 of 41 agents, peak expiratory flow monitoring for three (3) agents, and the clinical history alone for three (3) agents. Immunological tests provided evidence supporting an IgE-mediated mechanism for eight (8) (20%) of the newly described agents. Conclusion. This paper highlights the importance of being alert to the occurrence of new LMW sensitizers, which can elicit OA. The immunological mechanism is explained by a type I hypersensitivity reaction in 20% of all newly described LMW agents. PMID:22548090

Pralong, J. A.; Cartier, A.; Vandenplas, O.; Labrecque, M.

2012-01-01

319

New challenges for a second-generation low-molecular-weight heparin: focus on bemiparin.  

PubMed

Bemiparin is a second-generation low-molecular-weight heparin (LMWH) that has the lowest molecular weight, the longest half-life and the highest anti-Factor Xa/anti-Factor IIa activity ratio. The safety and efficacy of bemiparin has been demonstrated in several studies and currently it is licensed for the treatment and prophylaxis of venous thromboembolism (VTE), as well as for the prevention of clotting in the extracorporeal circuit during hemodialysis. Multicenter pharmacoeconomic studies carried out in the Spanish National Health system indicate that bemiparin is more cost effective than enoxaparin for the prevention of VTE in total knee replacement. Interestingly, recent results suggest that bemiparin could be useful as an adjuvant treatment in the management of lower-extremity diabetic ulcers. Since international guidelines recommend LMWHs for initial and continuous anticoagulant treatment in cancer patients with VTE, as well as for its prevention, results from ongoing trials could be critical to establish the potential of bemiparin in oncological patients. Finally, the pharmacokinetics of two oral bemiparin formulations are currently being analyzed in a Phase I trial. PMID:20450295

Martínez-González, José; Rodríguez, Cristina

2010-05-01

320

Bemiparin, an effective and safe low molecular weight heparin: a review.  

PubMed

Bemiparin is a low molecular weight heparin (LMWH) indicated for the acute treatment of deep vein thrombosis with or without pulmonary embolism, for the prophylaxis of venous thromboembolism in surgical and non-surgical patients and for the prevention of clotting in the extracorporeal circuit during hemodialysis. Due to its excellent pharmacological profile-the second-generation LMWH with the lowest molecular weight, the longest half-life and the highest anti-Factor Xa/anti-Factor IIa activity ratio-it can be safely used in special categories of patients (children, elderly, patients with renal impairment and congestive heart failure). Several studies demonstrated its safety and efficacy, while cost analyses show the economic benefits of bemiparin treatment as compared to other heparins. Recent evidences suggested the application of bemiparin even in the management of diabetic foot ulcers. The aim of this narrative review was to evaluate literature according to results coming from studies involving bemiparin administration in various clinical conditions. PMID:24657810

Ciccone, Marco Matteo; Cortese, Francesca; Corbo, Filomena; Corrales, Noel Ernesto; Al-Momen, Abdul Kareem; Silva, Antonio; Zito, Annapaola; Pinto, Mariangela; Gesualdo, Michele; Scicchitano, Pietro

2014-07-01

321

Thrombin generation assay identifies individual variability in responses to low molecular weight heparin in pregnancy: implications for anticoagulant monitoring.  

PubMed

Low molecular weight heparin (LMWH) given to inhibit coagulation and reduce the risk of thrombosis, is typically monitored by anti-Xa assay. However, anti-Xa levels may not necessarily provide an accurate measure of coagulation inhibition. Moreover, pregnancy is associated with hypercoagulability, which may compromise the efficacy of LMWH. We looked at the association between anti-Xa levels and parameters of thrombin generation assay [TGA; area under the curve (AUC), peak height (PH) and time to peak (ttP)] using samples from 41 pregnant women receiving LMWH and 40 normal pregnant women controls. TGA results confirmed the physiological hypercoagulability of normal pregnancy (mean normalised values: AUC 119%; PH 157%; ttP 72%). Although anti-Xa measures correlated with all three TGA parameters, this group correlation masked significant inter-individual variability, demonstrated by the R(2) value or coefficient of determination. Anti-Xa levels contributed to 74% of variation in AUC values, 63% of variation in PH values and only 53% of variation in ttP values. The remainder reflects the contribution of patients' intrinsic coagulation status. Hence, some patients with 'safe' anti-Xa levels may potentially be under-anticoagulated, particularly in pregnancy. Measuring coagulability directly with TGA may lower the risk of adverse events due to under-anticoagulation in selected patients. PMID:25351814

Chowdary, Pratima; Adamidou, Despoina; Riddell, Anne; Aghighi, Saman; Griffioen, Anja; Priest, Paul; Moghadam, Lida; Kelaher, Nicholas; Huq, Farah Y; Kadir, Rezan A; Tuddenham, Edward G; Gatt, Alex

2015-03-01

322

Antibacterial activity of chemically defined chitosans: influence of molecular weight, degree of acetylation and test organism.  

PubMed

Chitosans, polysaccharides obtained from the exoskeleton of crustaceans, have been shown to exert antibacterial activity in vitro and their use as a food preservative is of growing interest. However, beyond a consensus that chitosan appears to disrupt the bacterial cell membrane, published data are inconsistent on the chemical characteristics that confer the antibacterial activity of chitosan. While most authors agree that the net charge density of the polymer (reflected in the fraction of positively charged amino groups at the C-2 position of the glucosamine unit) is an important factor in antibacterial activity, conflicting data have been reported on the effect of molecular weight and on the susceptibility among different bacterial species to chitosan. Therefore, we prepared batches of water-soluble hydrochloride salts of chitosans with weight average molecular weights (M(w)) of 2-224kDa and degree of acetylation of 0.16 and 0.48. Their antibacterial activity was evaluated using tube inhibition assays and membrane integrity assays (N-Phenyl-1-naphthylamine fluorescence and potassium release) against Bacillus cereus, Escherichia coli, Salmonella Typhimurium and three lipopolysaccharide mutants of E. coli and S. Typhimurium. Chitosans with lower degree of acetylation (F(A)=0.16) were more active than the more acetylated chitosans (F(A)=0.48). No trends in antibacterial action related to increasing or decreasing M(w) were observed although one of the chitosans (M(w) 28.4kDa, F(A)=0.16) was more active than the other chitosans, inhibiting growth and permeabilizing the membrane of all the test strains included. The test strains varied in their susceptibility to the different chitosans with wild type S. Typhimurium more resistant than the wild type E. coli. Salmonellae lipopolysaccharide mutants were more susceptible than the matched wild type strain. Our results show that the chitosan preparation details are critically important in identifying the antibacterial features that target different test organisms. PMID:21605923

Mellegård, H; Strand, S P; Christensen, B E; Granum, P E; Hardy, S P

2011-07-15

323

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

USGS Publications Warehouse

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.

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

1990-01-01

324

Purification, composition, charge, and molecular weight of the FeMo cofactor from Azotobacter vinelandii nitrogenase.  

PubMed

A procedure has been developed for purifying NMF and NMF/DMF solutions of the FeMo cofactor (FeMoco) derived from the molybdenum iron protein of nitrogenase. This procedure consists of anaerobic chromatography of FeMoco solutions on two consecutive anaerobic molecular sizing columns followed by electrophoretic migration through a third sizing column. FeMoco prepared by this procedure is homogeneous as evidenced by chromatographic, electrophoretic, and compositional criteria. The minimal elemental composition was found to be MoFe6S6 using chemical colorimetric, inductively coupled plasma (ICP), and proton induced x-ray emission (PIXE) analytical procedures. Molecular weight measurements of NMF and DMF solutions of FeMoco using calibrated columns containing various molecular sizing matrices gave values of 1395 +/- 130 daltons for the molecular weight of FeMoco. The measured MW of FeMoco is about twice the value expected from the minimal stoichiometry, suggesting that FeMoco may exist as Mo2Fe12S12 in NMF and DMF solutions. The charge of FeMoco in its EPR silent state was determined to be 2- per Mo by passing NMF solutions of FeMoco containing excess salts of Na+, K+, Rb+, and Mg2+ through long columns equilibrated with pure NMF and then measuring the M/Mo ratio of the emerging FeMoco. Decomposition of purified FeMoco by acid or O2-exposure followed by exhaustive methylation or silanation of the resulting mixture failed to yield any methylated or silanated homocitric acid as measured by tandem gas chromatography-mass spectrometry (GC-MS) analysis. The GC-MS procedure applied to standard homocitric acid samples and various controls readily detects methylated homocitric acid at the sub-nanomole level. We conclude that the minimum molecular formula for active oxidized (EPR silent) FeMoco in NMF and in NMF-DMF mixtures is [Mo2Fe12S12]4-, but that other small organic anions such as NMF- may be present. PMID:8228979

Huang, H Q; Kofford, M; Simpson, F B; Watt, G D

1993-10-01

325

Fluorescence imaging of macromolecule transport in high molecular weight cut-off microdialysis.  

PubMed

When microdialysis (MD) membrane exceeds molecular weight cut-off (MWCO) of 100 kDa, the fluid mechanics are in the ultrafiltration regime. Consequently, fluidic mass transport of macromolecules in the perfusate over the membrane may reduce the biological relevance of the sampling and cause an inflammatory response in the test subject. Therefore, a method to investigate the molecular transport of high MWCO MD is presented. An in vitro test chamber was fabricated to facilitate the fluorescent imaging of the MD sampling process, using fluoresceinylisothiocyanate (FITC) dextran and fluorescence microscopy. Qualitative studies on dextran behavior inside and outside the membrane were performed. Semiquantitative results showed clear dextran leakage from both 40 and 250 kDa dextran when 100 kDa MWCO membranes were used. Dextran 40 kDa leaked out with an order of magnitude higher concentration and the leakage pattern resembled more of a convective flow pattern compared with dextran 250 kDa, where the leakage pattern was more diffusion based. No leakage was observed when dextran 500 kDa was used as a colloid osmotic agent. The results in this study suggest that fluorescence imaging could be used as a method for qualitative and semiquantitative molecular transport and fluid dynamics studies of MD membranes and other hollow fiber catheter membranes. PMID:25286875

Chu, Jiangtao; Koudriavtsev, Vitali; Hjort, Klas; Dahlin, Andreas P

2014-11-01

326

Oligomeric bile acid-mediated oral delivery of low molecular weight heparin.  

PubMed

Intestinal transporters are limited to the transport of small molecular substrates. Here, we describe the development of apical sodium-dependent bile acid transporter (ASBT)-targeted high-affinity oligomeric bile acid substrates that mediate the transmembrane transport of low molecular weight heparin (LMWH). Several oligomers of deoxycholic acid (oligoDOCA) were synthesized to investigate the substrate specificity of ASBT. To see the binding of oligoDOCA on the substrate-binding pocket of ASBT, molecular docking was used and the dissociation rate constants (KD) were measured using surface plasmon resonance. The KD for tetrameric DOCA (tetraDOCA) was 50-fold lower than that for monomeric DOCA, because tetraDOCA interacted with several hydrophobic grooves in the substrate-binding pocket of ASBT. The synthesized oligoDOCA compounds were subsequently chemically conjugated to macromolecular LMWH. In vitro, tetraDOCA-conjugated LMWH (LHe-tetraD) had highest selectivity for ASBT during its transport. Orally administered LHe-tetraD showed remarkable systemic anticoagulation activity and high oral bioavailability of 33.5±3.2% and 19.9±2.5% in rats and monkeys, respectively. Notably, LHe-tetraD successfully prevented thrombosis in a rat model of deep vein thrombosis. These results represent a major advancement in ASBT-mediated LMWH delivery and may facilitate administration of many important therapeutic macromolecules through a non-invasive oral route. PMID:24333628

Al-Hilal, Taslim A; Park, Jooho; Alam, Farzana; Chung, Seung Woo; Park, Jin Woo; Kim, Kwangmeyung; Kwon, Ick Chan; Kim, In-San; Kim, Sang Yoon; Byun, Youngro

2014-02-10

327

Effects of cross-linked high-molecular-weight hyaluronic acid on epidural fibrosis: experimental study.  

PubMed

OBJECT Epidural fibrosis is nonphysiological scar formation, usually at the site of neurosurgical access into the spinal canal, in the intimate vicinity of and around the origin of the radicular sheath. The formation of dense fibrous tissue causes lumbar and radicular pain. In addition to radicular symptoms, the formation of scar tissue may cause problems during reoperation. The authors aimed to investigate the effects of cross-linked high-molecular-weight hyaluronic acid (HA), an HA derivative known as HA gel, on the prevention of epidural fibrosis by using histopathological and biochemical parameters. METHODS Fifty-six adult female Sprague-Dawley rats were evaluated. The rats were divided into 4 groups. Rats in the sham group (n = 14) underwent laminectomy and discectomy and received no treatment; rats in the control group (n = 14) underwent laminectomy and discectomy and received 0.9% NaCl treatment in the surgical area; rats in the HA group (n = 14) received HA treatment at the surgical area after laminectomy and discectomy; and rats in the HA gel group (n = 14) underwent laminectomy and discectomy in addition to receiving treatment with cross-linked high-molecular-weight HA in the surgical area. All rats were decapitated after 4 weeks, and the specimens were evaluated histopathologically and biochemically. The results were statistically compared using the Mann-Whitney U-test. RESULTS Compared with the sham and control groups, the HA and HA gel groups showed significantly lower fibroblast cell density and tissue hydroxyproline concentrations (p < 0.05). There was statistically significant lower dural adhesion and foreign-body reaction between the control and HA gel groups (p < 0.05). Granulation tissue and epidural fibrosis were significantly lower in the HA and HA gel groups compared with the sham group (p < 0.05). There were no significant differences in any histopathological parameters or biochemical values between Groups 3 and 4 (p > 0.05). CONCLUSIONS Cross-linked high-molecular-weight HA had positive effects on the prevention of epidural fibrosis and the reduction of fibrotic tissue density. The efficacy of this agent should also be verified in further experimental and clinical studies. PMID:25396261

Is?k, Semra; Ta?kap?l?o?lu, M Özgür; Atalay, Fatma Oz; Dogan, Seref

2015-01-01

328

Aqueous geochemistry of low molecular weight hydrocarbons at elevated temperatures and pressures: constraints from mineral buffered laboratory experiments  

NASA Astrophysics Data System (ADS)

Organic matter, water, and minerals coexist at elevated temperatures and pressures in sedimentary basins and participate in a wide range of geochemical processes that includes the generation of oil and natural gas. A series of laboratory experiments were conducted at 300 to 350°C and 350 bars to examine chemical interactions involving low molecular weight aqueous hydrocarbons with water and Fe-bearing minerals under hydrothermal conditions. Mineral buffers composed of hematite-magnetite-pyrite, hematite-magnetite, and pyrite-pyrrhotite-magnetite were added to each experiment to fix the redox state of the fluid and the activity of reduced sulfur species. During each experiment the chemical system was externally modified by addition of ethene, ethane, propene, 1-butene, or n-heptane, and variations in the abundance of aqueous organic species were monitored as a function of time and temperature. Results of the experiments indicate that decomposition of aqueous n-alkanes proceeds through a series of oxidation and hydration reactions that sequentially produce alkenes, alcohols, ketones, and organic acids as reaction intermediaries. Organic acids subsequently undergo decarboxylation and/or oxidation reactions to form carbon dioxide and shorter chain saturated hydrocarbons. This alteration assemblage is compositionally distinct from that produced by thermal cracking under anhydrous conditions, indicating that the presence of water and minerals provide alternative reaction pathways for the decomposition of hydrocarbons. The rate of hydrocarbon oxidation decreases substantially under reducing conditions and in the absence of catalytically active aqueous sulfur species. These results represent compelling evidence that the stability of aqueous hydrocarbons at elevated temperatures in natural environments is not a simple function of time and temperature alone. Under the appropriate geochemical conditions, stepwise oxidation represents a mechanism for the decomposition of low molecular weight hydrocarbons and the production of methane-rich ("dry") natural gas. Evaluation of aqueous reaction products generated during the experiments within a thermodynamic framework indicates that alkane-alkene, alkene-ketone, and alkene-alcohol reactions attained metastable thermodynamic equilibrium states. This equilibrium included water and iron-bearing minerals, demonstrating the direct involvement of inorganic species as reactants during organic transformations. The high reactivity of water and iron-bearing minerals suggests that they represent abundant sources of hydrogen and oxygen available for the formation of hydrocarbons and oxygenated alteration products. Thus, variations in elemental kerogen composition may not accurately reflect the timing and extent of hydrocarbon, carbon dioxide, and organic acid generation in sedimentary basins. This study demonstrates that the stabilities of aqueous hydrocarbons are strongly influenced by inorganic sediment composition at elevated temperatures. Incorporation of such interactions into geochemical models will greatly improve prediction of the occurrence of hydrocarbons in natural environments over geologic time.

Seewald, Jeffrey S.

2001-05-01

329

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

USGS Publications Warehouse

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.

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

2004-01-01

330

Seasonal variation of high-molecular-weight compounds in the water-soluble fraction of organic urban aerosols  

NASA Astrophysics Data System (ADS)

Aerosol samples were collected in Zurich, Switzerland, at an urban background site and were analyzed with size exclusion chromatography (SEC) and laser/desorption ionization mass spectrometry (LDI-MS) for water-soluble organic compounds with high molecular weight. Daily samples were collected during two campaigns in winter and summer, for 1 month each. The concentration of high-molecular-weight compounds (humic-like substances (HULIS)) was between 0.4 and 4 ?g/m3 in winter and summer. The most intense signals in the LDI-MS mass spectra were measured between m/z150 and 500, comparing well with the mode of the two main high mass peaks determined with SEC corresponding to masses between 200 and 600 Da. For the maximum molecular weight, however, different results were obtained by the two techniques: whereas a maximum molecular weight between 1300 and 3300 Da was found with SEC, hardly any peaks above m/z700 were measured with LDI-MS. During summer the maximum molecular weight of HULIS (determined with SEC) correlates positively with several parameters such as ozone and increased temperature indicative of enhanced atmospheric photo-oxidation. The HULIS concentration also correlates positively with the oxalic acid concentration in the particles. This suggests that HULIS are generated by secondary processes in summer. The lack of such correlations during winter suggests that other sources and processes might be important during colder seasons.

Samburova, V.; Szidat, S.; Hueglin, C.; Fisseha, R.; Baltensperger, U.; Zenobi, R.; Kalberer, M.

2005-12-01

331

Immune-enhancing activities of low molecular weight ?-glucan depolymerized by gamma irradiation  

NASA Astrophysics Data System (ADS)

?-glucans are structural cell wall polymers of many microorganisms and cereals which possess immunomodulatory properties and have been used in the food, cosmetic and medical industry. In our previous study, ?-glucan was depolymerized by gamma irradiation and leads to improve the solubility and viscosity. This study was carried out to evaluate the functional properties, mainly immune-enhancing activities of low molecular weight ?-glucan fragmented by gamma irradiation. The results showed that RAW 264.7 macrophage cell stimulation activities of irradiated ?-glucan were higher than that of non-irradiated ?-glucan. In addition, the oral administration of gamma-irradiated ?-glucan significantly increased the proliferation and cytokine (IFN-? and IL-2) release of spleen and Peyer's patch cells compared with non-irradiated ?-glucan. In conclusion, gamma irradiation could be used as an effective method for the production of depolymerized ?-glucan improved functional property such as immunomodulatory activity.

Sung, Nak-Yun; Byun, Eui-Hong; Kwon, Sun-Kyu; Song, Beom-Seok; Choi, Jong-il; Kim, Jae-Hun; Byun, Myung-Woo; Yoo, Young-Choon; Kim, Mee-Ree; Lee, Ju-Woon

2009-07-01

332

Antioxidation activities of low-molecular-weight gelatin hydrolysate isolated from the sea cucumber Stichopus japonicus  

NASA Astrophysics Data System (ADS)

Gelatin extracted from the body wall of the sea cucumber ( Stichopus japonicus) was hydrolyzed with flavourzyme. Low-molecular-weight gelatin hydrolysate (LMW-GH) of 700-1700 Da was produced using an ultrafiltration membrane bioreactor system. Chemiluminescence analysis revealed that LMW-GH scavenges high free radicals in a concentration-dependent manner; IC50 value for superoxide and hydroxyl radicals was 442 and 285 ?g mL-1, respectively. LMW-GH exhibited excellent inhibitory characteristics against melanin synthesis and tyrosinase activity in B16 cells. Furthermore, LMW-GH notably increased intracellular glutathione (GSH), which in turn suppressed melanogenesis. LMW-GH performs antioxidation activity, holding the potential of being used as a valuable ingredient in function foods, cosmetics and pharmaceuticals or nutriceuticals.

Wang, Jingfeng; Wang, Yuming; Tang, Qingjuan; Wang, Yi; Chang, Yaoguang; Zhao, Qin; Xue, Changhu

2010-03-01

333

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

NASA Technical Reports Server (NTRS)

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

Chuang, Kathy C.; Vannucci, Raymond D.

1993-01-01

334

[Thrombocytopenia induced by low molecular weight heparin during hypotensive and diuretic treatment: coincidence or connection?].  

PubMed

A case is reported of a 70-year-old female who presented with early thrombocytopaenia, apparently induced by a low molecular weight heparin. The patient was admitted with anasarca. The initial treatment consisted in digoxin, furosemide, potassium canrenoate and aldactone, and 0.3 ml of Fraxiparine daily, which replaced acenocoumarol. She had never been given any heparin previously. On the fourth day, her platelet count had dropped from 210 G.1-1 to 122 G.1-1, and to 15 G.1-1 on the sixth day. Heparin administration had been stopped on the fourth day, and the platelet count had returned to 141 G.1-1 five days later. Similar cases of such an early thrombocytopaenia have been reported in patients also taking diuretics and hypotensive drugs. However, a relationship between the two facts cannot yet be ascertained. PMID:1664667

Lévy, G; Lévy, P Y; Jamet, M; Toroyan, P

1991-01-01

335

D-penicillamine and other low molecular weight thiols: review of anticancer effects and related mechanisms.  

PubMed

Low molecular weight thiols (LMWTs) like N-acetyl cysteine, D-penicillamine, captopril, Disulfiram and Amifostine, etc. have been used as chemo-preventive agents. Recent studies have reported cell growth inhibition and cytotoxicity in several different types of cancer cells following treatment with several LMWTs. Cytotoxic and cytostatic effects of LMWTs may involve interaction of the thiol group with cellular lipids, proteins, intermediates or enzymes. Some of the mechanisms that have been proposed include a p53 mediated apoptosis, thiyl radical induced DNA damage, membrane damage through lipid peroxidation, anti-angiogenic effects induced by inhibition of matrix metalloproteinase enzymes and angiostatin generation. LMWTs are strong chelators of transition metals like copper, nickel, zinc, iron and cobalt and may cause metal co-factor depletion resulting in cytotoxicity. Oxidation of thiol group can also generate cytotoxic reactive oxygen species (ROS). PMID:23727371

Wadhwa, Saurabh; Mumper, Russell J

2013-08-28

336

Bioassay-guided isolation of a low molecular weight PHB from Burkholderia sp. with phytotoxic activity.  

PubMed

This work reports on the bioassay-guided isolation and identification of the macrocyclic pentolide 1, a cyclic polyhydroxybutyrate (PHB) with low molecular weight. This metabolite is produced by Burkholderia sp. and it exhibited phytotoxic activity in a Lemna minor bioassay. Its structure was determined by (1)H and (13)C NMR, heteronuclear multiple quantum correlation, heteronuclear multiple bond correlation, IR, and electrospray ionization tandem mass spectrometry analyses. The period for maximum production of the pentolide was optimized and determined on the basis of multiple reaction monitoring experiments at 15 days. The potential of Burkholderia sp. as a producer of higher biopolymers of PHB was also investigated. The methodology employed here accelerated the isolation and characterization of a phytotoxic metabolite whose structure can serve as a model for the synthesis of new classes of herbicides. PMID:23722946

Petta, Tânia; Raichardt, Leandro; Melo, Itamar S; Moraes, Luiz A B

2013-08-01

337

Surface modification of ultra high molecular weight polyethylene fibers via the sequential photoinduced graft polymerization  

NASA Astrophysics Data System (ADS)

In this study, a sequential photoinduced graft polymerization process was proposed to improve the poor interfacial bonding property of ultra high molecular weight polyethylene (UHMWPE) fibers. The polymerization was initiated by dormant semipinacol (SP) groups and carried out in a thin liquid layer. Methacrylic acid (MAA) and acryl amide (AM) were grafted stepwise onto the surface of UHMWPE fibers. Attenuated total reflectance infrared spectroscopy (ATR-IR) and thermo gravimetric analysis (TGA) confirmed the grafting. The analysis result of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) indicated the structure of grafted chains. Scanning electron microscopy (SEM) images and atomic force microscopy (AFM) images revealed the apparent morphology changing, and the grafted layers were observed. Interfacial shear stress (IFSS) test of the modified fibers showed an extensively improved interfacial bonding property. The active groups grafted onto the fibers would supply enough anchor points for the chemical bonding with various resins or further reactions.

Li, Zhi; Zhang, Wei; Wang, Xinwei; Mai, Yongyi; Zhang, Yumei

2011-06-01

338

Molecular weight: Property relationships of high performance polymers used for adhesives and composites  

NASA Technical Reports Server (NTRS)

Degradation of high performance polyimide precursor resins was investigated by measuring the molecular weight of the polymers in solution, using a membrane osmometer. It was found that polyimide precursor resins composed of BTDA and ODPA combined with DABP and MDA were unstable in DMAC. The degradation rate was found to depend upon the chemical nature of the isomeric diamine and the geometric structure about the amide linkage. The polymers of DABP were less susceptible to degradation than those of MDA and p,p'-compounds were more stable than m,m'-compounds. These results suggest that degradation is correlated with the basicity of the diamine. That is, the rate of the degradation reaction increases with the basicity of the diamine group in the polyimide precursor resin. The presence of water and a higher temperature increased the degradation rate of the polymers.

Kranbuehl, D.

1975-01-01

339

Numerical simulations on fatigue destruction of ultra-high molecular weight polyethylene using discrete element analyses.  

PubMed

Ultra-high molecular weight polyethylene (UHMWPE) is a heterogeneous material composed of a networked substructure of grain boundary and grain aggregation. A new numerical model based on the discrete element method (DEM) was proposed to examine microscopic defect formation and propagation in UHMWPE. Numerical simulations were carried out using this model under two types of loading condition: unidirectional repetitive compression (simple loading) and bidirectional repetitive compression (switched loading). Subsurface defects were initiated and propagated in the vicinity of grain boundaries under both loading conditions. The defect propagation behavior was especially sensitive to grain boundary allocation under switched loading. An increase in defects was more rapid under switched loading than under simple loading. These numerical results showed qualitatively good agreement with experimental ones. It is suggested that the newly developed numerical method based on the DEM is a promising method to investigate fatigue behavior of a heterogeneous material such as UHMWPE under complicated loading conditions. PMID:12579572

Shibata, Nobuyuki; Tomita, Naohide; Ikeuchi, Ken

2003-03-01

340

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

SciTech Connect

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

Yamamoto, Kohji; Yamaguchi, Mariko; Tani, Masahiko; Hangyo, Masanori; Teramura, Satoshi; Isu, Toshiro; Tomita, Naohide [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka, 565-0871 (Japan); Graduate School of Material Science, Nara Institute of Science and Technology (NAIST), 8916-5, Takayama, Ikoma, Nara, 630-0101 (Japan); International Innovation Center, Kyoto University, Yoshida-Hon-machi, Sakyo-ku, Kyoto, 606-8501 (Japan)

2004-11-29

341

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

342

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

SciTech Connect

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

Merk, Hans F. [Department of Dermatology and Allergology, Univ.-Hospital, RWTH Aachen, Pauwelsstr. 30, D-52074 Aachen (Germany)], E-mail: hans.merk@post.rwth-aachen.de; Baron, Jens M.; Neis, Mark M.; Obrigkeit, Daniela Hoeller [Department of Dermatology and Allergology, Univ.-Hospital, RWTH Aachen, Pauwelsstr. 30, D-52074 Aachen (Germany); Karlberg, Ann-Therese [Dermatochemistry and Skin Allergy, Department of Chemistry, Goeteborg University, SE-412 96 Goeteborg (Sweden)

2007-11-01

343

Use of principal component analysis for differentiation of gelatine sources based on polypeptide molecular weights.  

PubMed

The study was aimed to differentiate between porcine and bovine gelatines in adulterated samples by utilising sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) combined with principal component analysis (PCA). The distinct polypeptide patterns of 6 porcine type A and 6 bovine type B gelatines at molecular weight ranged from 50 to 220 kDa were studied. Experimental samples of raw gelatine were prepared by adding porcine gelatine in a proportion ranging from 5% to 50% (v/v) to bovine gelatine and vice versa. The method used was able to detect 5% porcine gelatine added to the bovine gelatine. There were no differences in the electrophoretic profiles of the jelly samples when the proteins were extracted with an acetone precipitation method. The simple approach employing SDS-PAGE and PCA reported in this paper may provide a useful tool for food authenticity issues concerning gelatine. PMID:24423534

Nur Azira, T; Che Man, Y B; Raja Mohd Hafidz, R N; Aina, M A; Amin, I

2014-05-15

344

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

NASA Technical Reports Server (NTRS)

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

Fusaro, R. L.

1983-01-01

345

Radical degradation of high molecular weight hyaluronan: inhibition of the reaction by ibuprofen enantiomers.  

PubMed

The antioxidative and/or free-radical-scavenging activities of R-(-)- and S-(+)-ibuprofen enantiomers, as well as of the drug racemate, were studied in vitro on measuring the kinetics of (uninhibited or drug-inhibited) degradation of high molecular weight hyaluronan by hydroxyl radicals. The continual flux of OH radicals at aerobic conditions was maintained by the H2O2 + Cu2+ system. The kinetics of hyaluronan degradation was monitored indirectly by capillary viscometry. Under experimental conditions, with no drug addition, the relative viscosity ([eta]rel) decreased continuously, reaching 13% of the initial [eta]rel. value in 4 h. Each drug tested exhibited a dose-dependent protective effect against hyaluronan degradation, however R-(-)-ibuprofen demonstrated a slightly greater activity than the drug S-(+)-enantiomer. PMID:11484412

Soltés, L; Lath, D; Mendichi, R; Bystrický, P

2001-03-01

346

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

NASA Technical Reports Server (NTRS)

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

Fusaro, R. L.

1985-01-01

347

In vivo endothelial siRNA delivery using polymeric nanoparticles with low molecular weight  

NASA Astrophysics Data System (ADS)

Dysfunctional endothelium contributes to more diseases than any other tissue in the body. Small interfering RNAs (siRNAs) can help in the study and treatment of endothelial cells in vivo by durably silencing multiple genes simultaneously, but efficient siRNA delivery has so far remained challenging. Here, we show that polymeric nanoparticles made of low-molecular-weight polyamines and lipids can deliver siRNA to endothelial cells with high efficiency, thereby facilitating the simultaneous silencing of multiple endothelial genes in vivo. Unlike lipid or lipid-like nanoparticles, this formulation does not significantly reduce gene expression in hepatocytes or immune cells even at the dosage necessary for endothelial gene silencing. These nanoparticles mediate the most durable non-liver silencing reported so far and facilitate the delivery of siRNAs that modify endothelial function in mouse models of vascular permeability, emphysema, primary tumour growth and metastasis.

Dahlman, James E.; Barnes, Carmen; Khan, Omar F.; Thiriot, Aude; Jhunjunwala, Siddharth; Shaw, Taylor E.; Xing, Yiping; Sager, Hendrik B.; Sahay, Gaurav; Speciner, Lauren; Bader, Andrew; Bogorad, Roman L.; Yin, Hao; Racie, Tim; Dong, Yizhou; Jiang, Shan; Seedorf, Danielle; Dave, Apeksha; Singh Sandhu, Kamaljeet; Webber, Matthew J.; Novobrantseva, Tatiana; Ruda, Vera M.; Lytton-Jean, Abigail K. R.; Levins, Christopher G.; Kalish, Brian; Mudge, Dayna K.; Perez, Mario; Abezgauz, Ludmila; Dutta, Partha; Smith, Lynelle; Charisse, Klaus; Kieran, Mark W.; Fitzgerald, Kevin; Nahrendorf, Matthias; Danino, Dganit; Tuder, Rubin M.; von Andrian, Ulrich H.; Akinc, Akin; Panigrahy, Dipak; Schroeder, Avi; Koteliansky, Victor; Langer, Robert; Anderson, Daniel G.

2014-08-01

348

Mechanical characterization of ultra-high molecular weight polyethylene-hydroxyapatite nanocomposites.  

PubMed

An experimental study of Ultra-High Molecular Weight Polyethylene (UHMWPE) and hydroxyapatite (HAP) nanocomposites for the purpose of joint prosthesis is investigated under quasi-static and dynamic loading conditions. By employing compression mold process, five different volume fractions of hydroxyapatite nanoparticle reinforced nanocomposites are made. Quasi-static tension and compression tests are performed using ASTM test methods. Dynamic compression characterization is performed using split Hopkinson pressure bar technique. The nanocomposite performance as a function of volume fraction under a typical loading rate is investigated. The results of the fabricated nanocomposites are compared with currently employed UHMWPE in the joint implants. For comparison purposes, separate sets of tests are performed on currently employed UHMWPE. This comparison provides a valid measure to identify the optimum volume fraction of hydroxyapatite that can be used without compromising the integrity of the UHMPWPE in joint prosthesis. PMID:18725695

Crowley, J; Chalivendra, V B

2008-01-01

349

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

PubMed

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

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

2014-05-01

350

Low-molecular-weight displacers for high-resolution protein separations.  

PubMed

The resolving power of displacement chromatography using low-molecular-weight displacers was investigated using a model mixture containing bovine and horse heart cytochrome c. The linear and nonlinear adsorption behavior of these two proteins was examined in cation-exchange chromatography and shown to be quite similar. Furthermore, an analysis of the dynamic affinity of these proteins indicated extremely similar affinities under displacement conditions. Despite the extreme similarities in the adsorption behavior, displacement chromatography using a protected amino acid displacer resulted in excellent separation of the proteins with both high yields and purity. These results indicate that displacement chromatography may be efficacious for a wide variety of difficult protein separation problems. PMID:9177730

Kundu, A; Cramer, S M

1997-05-15

351

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

PubMed

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

Hovsépian, S; Aouani, A; Fayet, G

1986-05-01

352

[Allelic variation at high-molecular-weight glutenin subunit loci in Aegilops biuncialis Vis].  

PubMed

Alleles at the high-molecular-weight glutenin subunit loci Glu-U1 and Glu-M(b)1 were analyzed in the tetraploid species Aegilops biuncialis (UUM(b)M(b)). The material for the investigation included the collection of 39 accessions of Ae. biuncialis from Ukraine (the Crimea), one Hellenic accession, one accession of unknown origin, F2 seeds from different crosses, as well as samples from natural populations from the Crimea. Ae. umbellulata and Ae. comosa accessions were used to allocate components of the HMW glutenin subunit patterns of Ae. biuncialis to U or M(b) genomes. Eight alleles were identified at the Glu-U1 locus and ten alleles were revealed at the Glu-M(b) 1 locus. Among alleles at the Glu-M(b) 1 locus ofAe. biuncialis there were two alleles controlling the y-type subunit only and one allele encoding the x-subunit only. PMID:22117406

Kozub, N A; Sozinov, I A; Ksinias, I N; Sozinov, A A

2011-09-01

353

High-molecular-weight polyethylene glycol enhances hypothermic storage of feline kidney cells.  

PubMed

Phosphate-buffered sucrose (PBSc) solution is effective for short-term hypothermic preservation of tissue during feline kidney transplantation. A high-molecular-weight polyethylene glycol (35,000 Da, PEG35) reportedly enhanced the protective effects against cold-induced tubular injuries in animal kidney transplantation models. We investigated the ability of PBSc solution containing PEG35 to preserve cultured feline kidney cells using in vitro WST-8 cell proliferation assays. PEG35 significantly improved cell viability during 24 hr of cold preservation. PBSc containing 20 g/l PEG35 achieved an effect almost equal to that of University of Wisconsin (UW) solution, the gold standard preservation solution used in human clinical kidney transplantation, for up to 24 hr of preservation. Our results suggest that PBSc containing PEG35 provides an excellent medium for graft cold storage during feline kidney transplantation. PMID:24599064

Katayama, Masaaki; Tsuchiaka, Shinobu; Motegi, Tomoki; Miyazaki, Masao; Yamashita, Tetsuro; Shimamura, Shunsuke; Okamura, Yasuhiko; Uzuka, Yuji

2014-06-01

354

Mechanical properties and biocompatibility of melt processed, self-reinforced ultrahigh molecular weight polyethylene.  

PubMed

The low efficiency of fabrication of ultrahigh molecular weight polyethylene (UHMWPE)-based artificial knee joint implants is a bottleneck problem because of its extremely high melt viscosity. We prepared melt processable UHMWPE (MP-UHMWPE) by addition of 9.8 wt% ultralow molecular weight polyethylene (ULMWPE) as a flow accelerator. More importantly, an intense shear flow was applied during injection molding of MP-UHMWPE, which on one hand, promoted the self-diffusion of UHMWPE chains, thus effectively reducing the structural defects; on the other hand, increased the overall crystallinity and induced the formation of self-reinforcing superstructure, i.e., interlocked shish-kebabs and oriented lamellae. Aside from the good biocompatibility, and the superior fatigue and wear resistance to the compression-molded UHMWPE, the injection-molded MP-UHMWPE exhibits a noteworthy enhancement in tensile properties and impact strength, where the yield strength increases to 46.3 ± 4.4 MPa with an increment of 128.0%, the ultimate tensile strength and Young's modulus rise remarkably up to 65.5 ± 5.0 MPa and 1248.7 ± 45.3 MPa, respectively, and the impact strength reaches 90.6 kJ/m(2). These results suggested such melt processed and self-reinforced UHMWPE parts hold a great application promise for use of knee joint implants, particularly for younger and more active patients. Our work sets up a new method to fabricate high-performance UHMWPE implants by tailoring the superstructure during thermoplastic processing. PMID:24835044

Huang, Yan-Fei; Xu, Jia-Zhuang; Li, Jian-Shu; He, Ben-Xiang; Xu, Ling; Li, Zhong-Ming

2014-08-01

355

A low molecular weight proteome comparison of fertile and male sterile 8 anthers of Zea mays.  

PubMed

During maize anther development, somatic locular cells differentiate to support meiosis in the pollen mother cells. Meiosis is an important event during anther growth and is essential for plant fertility as pollen contains the haploid sperm. A subset of maize male sterile mutants exhibit meiotic failure, including ms8 (male sterile 8) in which meiocytes arrest as dyads and the locular somatic cells exhibit multiple defects. Systematic proteomic profiles were analysed in biological triplicates plus technical triplicates comparing ms8 anthers with fertile sibling samples at both the premeiotic and meiotic stages; proteins from 3.5 to 20 kDa were fractionated by 1-D PAGE, cleaved with Lys-C and then sequenced using a LTQ Orbitrap Velos MS paradigm. Three hundred and 59 proteins were identified with two or more assigned peptides in which each of those peptides were counted at least two or more times (0.4% peptide false discovery rate (FDR) and 0.2% protein FDR); 2761 proteins were identified with one or more assigned peptides (0.4% peptide FDR and 7.6% protein FDR). Stage-specific protein expression provides candidate stage markers for early anther development, and proteins specifically expressed in fertile compared to sterile anthers provide important clues about the regulation of meiosis. 49% of the proteins detected by this study are new to an independent whole anther proteome, and many small proteins missed by automated maize genome annotation were validated; these outcomes indicate the value of focusing on low molecular weight proteins. The roles of distinctive expressed proteins and methods for mass spectrometry of low molecular weight proteins are discussed. PMID:22748129

Wang, Dongxue; Adams, Christopher M; Fernandes, John F; Egger, Rachel L; Walbot, Virginia

2012-10-01

356

Biosynthesis and functions of bacillithiol, a major low-molecular-weight thiol in Bacilli  

PubMed Central

Bacillithiol (BSH), the ?-anomeric glycoside of L-cysteinyl-D-glucosamine with L-malic acid, is a major low-molecular-weight thiol in Bacillus subtilis and related bacteria. Here, we identify genes required for BSH biosynthesis and provide evidence that the synthetic pathway has similarities to that established for the related thiol (mycothiol) in the Actinobacteria. Consistent with a key role for BSH in detoxification of electrophiles, the BshA glycosyltransferase and BshB1 deacetylase are encoded in an operon with methylglyoxal synthase. BshB1 is partially redundant in function with BshB2, a deacetylase of the LmbE family. Phylogenomic profiling identified a conserved unknown function protein (COG4365) as a candidate cysteine-adding enzyme (BshC) that co-occurs in genomes also encoding BshA, BshB1, and BshB2. Additional evolutionarily linked proteins include a thioredoxin reductase homolog and two thiol:disulfide oxidoreductases of the DUF1094 (CxC motif) family. Mutants lacking BshA, BshC, or both BshB1 and BshB2 are devoid of BSH. BSH is at least partially redundant in function with other low-molecular-weight thiols: redox proteomics indicates that protein thiols are largely reduced even in the absence of BSH. At the transcriptional level, the induction of genes controlled by two thiol-based regulators (OhrR, Spx) occurs normally. However, BSH null cells are significantly altered in acid and salt resistance, sporulation, and resistance to electrophiles and thiol reactive compounds. Moreover, cells lacking BSH are highly sensitive to fosfomycin, an epoxide-containing antibiotic detoxified by FosB, a prototype for bacillithiol-S-transferase enzymes. PMID:20308541

Gaballa, Ahmed; Newton, Gerald L.; Antelmann, Haike; Parsonage, Derek; Upton, Heather; Rawat, Mamta; Claiborne, Al; Fahey, Robert C.; Helmann, John D.

2010-01-01

357

Tumor-Specific Urinary MMP Fingerprinting: Identification of High Molecular Weight Urinary MMP Species  

PubMed Central

Purpose We have previously reported that MMP-2, MMP-9 and the complex MMP-9/NGAL can be detected in urine of patients with a variety of cancers including prostate and bladder carcinoma. In addition, we also detected several unidentified urinary gelatinase activities with molecular weights >125kDa. The objective of the current study was to identify these high molecular weight (HMW) species, determine their potential as predictors of disease status and ask whether a tumor-specific pattern existed based on urinary MMP (uMMP) analysis. Experimental Design Chromatography, zymography and mass spectrometry was used to identify HMW gelatinase species of ?140, 190 and >220kDa in urine of cancer patients. To determine whether a tumor-specific pattern of appearance existed among the MMPs detected, we analyzed the urine of 189 patients with prostate or bladder cancer and controls. Results The ?140, >220kDa and ?190 HMW gelatinase species were identified as MMP-9/TIMP-1 complex, MMP-9 dimer and ADAMTS-7 respectively. The frequency of detection of any MMP species was significantly higher in urine from prostate and bladder cancer groups than controls. MMP-9 dimer and MMP-9 were independent predictors for distinguishing between patients with prostate or bladder cancer (P<0.001 for each) by multivariable analysis. Conclusions This study is the first to identify a tumor-specific uMMP fingerprint that may noninvasively facilitate identification of cancer presence and type. This information may be of diagnostic and prognostic value in the detection and/or clinical monitoring of disease progression and therapeutic efficacy in patients with bladder or prostate cancer. PMID:18927302

Roy, Roopali; Louis, Gwendolyn; Loughlin, Kevin R.; Wiederschain, Dmitri; Kilroy, Susan M.; Lamb, Carolyn C.; Zurakowski, David; Moses, Marsha A.

2009-01-01

358

Synthesis and characterization of monosaccharide-derived carbamates as low-molecular-weight gelators.  

PubMed

Sugar-based low-molecular-weight gelators are an interesting new class of compounds that are important in supramolecular chemistry and for the preparation of advanced materials. Previously, we synthesized a series of ester and carbamate derivatives of 4,6-O-benzylidene methyl-alpha-D-glucopyranoside and found that monosubstituted alkynyl esters with five to seven carbons and monosubstituted carbamates with saturated five- and seven-carbon chains are good gelators. To understand the structural requirement for the gelation of the carbamate derivatives (O-linked carbamates), a diverse series of analogs, including alkynyl, aryl, and alkyl halide derivatives, were prepared and analyzed. We found that for gelation the O-linked carbamate derivatives have different structural preferences than the ester derivatives. To exhibit gellation, the ester analogs favor alkyl-containing terminal acetylene groups and the carbamoyl derivatives prefer saturated hydrocarbons. Both the esters and the carbamates showed good gelation properties when they were functionalized with aryl side chains. We also synthesized and screened a new series of carbamates (N-linked carbamates) in which the nitrogen atom of the carbamate group is directly attached to the sugar ring. The N-linked carbamates are good gelators for aqueous DMSO and ethanol solutions, and two of the compounds are also able to form gels in pure water. Optical microscopy and scanning electron microscopy were used to characterize several representative gels. In general, long, narrow, uniform fibrous networks were observed for effective gelators. The structure-gelation correlation obtained here can be used in the design of new sugar-based low-molecular-weight gelators. PMID:19449815

Wang, Guijun; Cheuk, Sherwin; Yang, Hao; Goyal, Navneet; Reddy, P V Narasimha; Hopkinson, Branden

2009-08-01

359

Isotopic evidence for the contemporary origin of high-molecular weight organic matter in oceanic environments  

NASA Astrophysics Data System (ADS)

Previous work has suggested that apparent old 14C ages for oceanic DOC are the result of mixing of different organic carbon fractions. This report provides direct evidence for a contemporary 14C age of a high-molecular-weight (HMW) fraction of colloidal organic carbon (?10 kD). Colloidal organic matter, COM 10 (from 10 kDaltons (kD) to 0.2 ?m), isolated from the upper water column of the Gulf of Mexico and the Middle Atlantic Bight (MAB) region, generally has a contemporary age (i.e., younger than a few decades), while COM 1 (from 1 kD to 0.2 ?m), is apparently old: 380-4500 y BP. Thus, BMW COM 10 (3-5% of DOC) from the upper water column is derived from living particulate organic matter (POM) and cycles rapidly, while a significant fraction of low-molecular-weight (?1 kD) DOM is likely more refractory, and cycles on much longer time scales. The presence of pigment biomarker compounds in COM 1 from the upper water column points to selected phytoplankton species as one of the sources of COM. Terrestrial carbon as another source of COM is suggested from the inverse correlation between ? 14C and ? 13C values, as well as the increasing ? 13C values with increasing salinity. 234Th-derived turnover times of COM 10 and COM 1 from both the Gulf of Mexico and MAB are consistently short, 1-20 and 3-30 days, respectively. These short residence times support the hypothesis that 14C ages of colloidal fractions of DOC are the result of COM fractions being a mixture of several endmembers with fast and slow turnover rates.

Santschi, Peter H.; Guo, Laodong; Baskaran, M.; Trumbore, Susan; Southon, John; Bianchi, Thomas S.; Honeyman, Bruce; Cifuentes, Luis

1995-02-01

360

Extended Fujita Approach to the Molecular Weight Distribution of Polysaccharides and other Polymeric Systems  

PubMed Central

In 1962 H. Fujita (Mathematical Theory of Sedimentation Analysis, Academic Press, New York, pp. 182–192) examined the possibility of transforming a quasi-continuous distribution g(s) of sedimentation coefficient s into a distribution f(M) of molecular weight M for linear polymers using the relation f(M) = g(s).(ds/dM) and showed that this could be done if information about the relation between s and M is available from other sources. Fujita provided the transformation based on the scaling relation s = ?M0.5, where ? is taken as a constant for that particular polymer and the exponent 0.5 essentially corresponds to a randomly coiled polymer under ideal conditions. This method was successfully applied to mucus glycoproteins (S.E. Harding, Adv. Carbohyd. Chem. Biochem. 47 (1989), 345–381). We now describe an extension of the method to general conformation types via the scaling relation s = ?Mb, where b = 0.4–0.5 for a coil, ~0.15–0.2 for a rod and ~0.67 for a sphere. We give examples of distributions f(M) vs M obtained for polysaccharides from SEDFIT derived least squares g(s) vs s profiles (P. Schuck, Biophys. J. 78 (2000) 1606–1619) and the analytical derivative for ds/dM performed with Microcal ORIGIN. We also describe a more direct route from a direct numerical solution of the integral equation describing the molecular weight distribution problem. Both routes give identical distributions although the latter offers the advantage of being incorporated completely within SEDFIT. The method currently assumes that solutions behave ideally: sedimentation velocity has the major advantage over sedimentation equilibrium in that concentrations less than 0.2 mg/ml can be employed, and for many systems non-ideality effects can be reasonably ignored. For large, non-globular polymer systems, diffusive contributions are also likely to be small. PMID:21276851

Harding, Stephen E.; Schuck, Peter; Abdelhameed, Ali Saber; Adams, Gary; Kök, M. Samil; Morris, Gordon A.

2011-01-01

361

Low molecular weight heparin (enoxaparin) reduces restenosis after iliac angioplasty in the hypercholesterolemic rabbit.  

PubMed

Smooth muscle cell proliferation is central to the process of restenosis. Attempts to inhibit the events leading to this proliferation have met with little success. In addition to its known antithrombotic effects, heparin also has inhibitory effects on smooth muscle cell proliferation. These effects appear to be unrelated to its anticoagulant properties and are retained in low molecular weight heparin derivatives. Although the use of heparin for as long as 18 to 24 h after coronary angioplasty in humans has not prevented restenosis, longer treatment periods have not been assessed. This study examines the effect of treatment with a low molecular weight heparin (enoxaparin) in a hypercholesterolemic rabbit iliac artery model. Control rabbits had a mean iliac artery diameter of 0.70 +/- 0.06 mm, which increased to 1.73 +/- 0.09 mm after balloon angioplasty. At follow-up angiography 4 weeks later, the mean vessel diameter was 0.56 +/- 0.12 mm. Animals treated with low dose enoxaparin (1 mg/kg per day) for 4 weeks and high dose enoxaparin (10 mg/kg per day) for either 2 or 4 weeks had similar mean luminal diameters before and immediately after angioplasty. At follow-up angiography, the mean luminal diameter was 0.82 +/- 0.17 mm for low dose enoxaparin, 1.04 +/- 0.20 mm for 2 week high dose enoxaparin (p = 0.03 versus control) and 1.19 +/- 0.09 mm for 4 week high dose enoxaparin (p = 0.001 versus control). When defined as loss of 50% of the initial gain achieved with angioplasty, restenosis was found in all control vessels.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1849930

Currier, J W; Pow, T K; Haudenschild, C C; Minihan, A C; Faxon, D P

1991-05-01

362

Identification and characterization of high-molecular-weight secalins from triticale seeds by capillary zone electrophoresis.  

PubMed

A rapid and reliable method for separation and characterization of the variability of high-molecular-weight secalin subunits (HMW-SS) in hexaploid triticale (x Triticosecale Wittmack) by CZE has been developed. In this method, a mixture of two poly(ethylene oxide) polymers differing in molecular weight and a high concentration of ACN in isoelectric buffer was applied as the running electrolyte. For dynamic coating of the capillary inner wall, a low-concentration mixture of poly(vinylpyrrolidone) and hydroxypropylmethylcellulose was employed. Wide allelic variations in rye HMW-SS composition, including some novel x- and y-type HMW-SS, were detected by CZE. The CZE electropherograms of HMW-SS showed two groups of peaks in accordance with y- and x-type subunits, with migration times of 8.0-8.8 and 11.0-13.3 min, respectively. HMW-SS differed in migration times from the simultaneously resolved HMW glutenin subunits, but frequently had very similar electrophoretic mobilities during separation by SDS-PAGE. Each of the two rye subunits 2r and 6.5r detected by SDS-PAGE represents in fact two subunits (5.1r or 5.2r, and 6.4r or 6.5r, respectively). After analyzing 106 European triticale cultivars, 12 HMW-SS were identified (six x-type and six y-type). They form six allelic variants of these subunits. The simultaneous separation and identification of triticale HMW glutenin and secalin subunits by CZE is an efficient alternative to SDS-PAGE and should facilitate breeding of valuable cultivars. PMID:20593398

Salmanowicz, Boleslaw P

2010-07-01

363

Large-scale expression and purification of high-molecular-weight glutenin subunits.  

PubMed

The high-molecular-weight glutenin subunits (HMW-GSs) are considered to be one of the most important components of wheat gluten, contributing to the unique viscoelastic properties of wheat dough. The HMW-GSs are highly homologous in sequence and structure and a mixture of subunits is usually present in wheat flours. Consequently, it is difficult to purify these proteins separately in appreciable amounts. Expression in heterologous systems provides a clear opportunity to produce large amounts of single HMW-GS proteins, amounts (up to 100 mg) which are required for in vitro analysis of these proteins. However, since the first expression studies of HMW-GSs, over 10 years ago, this technology has not been widely utilized. Previous studies have been analytical or small scale (5-100 ml) and in most cases only partial purity was obtained. In the present paper, we describe in detail the expression of the HMW-GSs Glu1-Dx2, Dx5, Dy10, and Dy12 for the first time on a large scale, producing up to 100 mg of target protein from a 2-liter bacterial culture, using a Biostat fermenter. Our results include optimization of expression conditions to increase yield and stability of proteins. Results also include localization, differences between x- and y-type expression and small-scale versus large-scale expression. We also developed a large-scale purification procedure. The bacterially expressed proteins have the same molecular weight on SDS-PAGE and the same retention times on RP-HPLC as their native counterparts extracted from flour. Functionality tests, on the bacterially produced proteins, have shown a clear correlation with the equivalent native proteins from flour. These results provide a clear opportunity to produce protein in amounts necessary for more detailed studies of the structure and function of the HMW-GSs and glutenin polymers on dough development and quality. PMID:12071704

Dowd, Caitriona; Bekes, Ferenc

2002-06-01

364

Low molecular weight PEI-appended polyesters as non-viral gene delivery vectors.  

PubMed

Routine clinical implementation of human gene therapy requires safe and efficient gene delivery methods. Linear biodegradable polyesters with carbon-carbon double bonds are prepared from unsaturated diacids and diols. Subsequent appending of low molecular weight PEI by Michael addition gives target cationic polymers efficiently. Agarose gel retardation and fluorescence quenching assays show that these materials have good DNA binding ability and can completely retard plasmid DNA at weight ratio of 0.8. The formed polyplexes have appropriate sizes around 275 nm and zeta-potential values about +20-35 mV. The cytotoxicities of these polymers assayed by MTT are much lower than that of 25 kDa PEI. In vitro transfection toward 7402, HEK293 and U-2OS cells show that polymer P1 may give dramatically higher transfection efficiency (TE) than 25 kDa PEI, especially in U-2OS cells, suggesting that such polymer might be promising non-viral gene vectors. PMID:24681389

Xun, Miao-Miao; Liu, Yan-Hong; Guo, Qian; Zhang, Ji; Zhang, Qin-Fang; Wu, Wan-Xia; Yu, Xiao-Qi

2014-05-01

365

Differential effects of fucoidans with low and high molecular weight on the viability and function of spleen cells.  

PubMed

Fucoidan is an edible sulfated polysaccharide purified from brown algae that has multiple biological activities. However, the effects of fucoidans of different molecular weights on immune cells have not been determined. Thus, we treated spleen cells with low- and high-molecular-weight fucoidans (LMF and HMF, respectively). Viability assays demonstrated that HMF enhanced the viability and prevented the death of spleen cells. Furthermore, functional analysis revealed that HMF significantly increased the production of interferon-? and nitric oxide. In contrast, LMF had low activity and was relatively toxic to spleen cells. Taken together, these results indicate that HMF makes the greatest contribution to the immunostimulatory activity of fucoidan mixtures. Additionally, fucoidans with different molecular weights may have different effects on the viability and function of immune cells. This study increases our understanding of fucoidans, and may broaden their use in the basic research and clinical fields. PMID:24681238

Jang, Ji-Young; Moon, Sun-Young; Joo, Hong-Gu

2014-06-01

366

The effects of molecular weight on the single lap shear creep and constant strain rate behavior of thermoplastic polyimidesulfone adhesive  

NASA Technical Reports Server (NTRS)

The bonded shear creep and constant strain rate behaviors of zero, one, and three percent endcapped thermoplastic polyimidesulfone adhesive were examined at room and elevated temperatures. Endcapping was accomplished by the addition of phthalic anhydrides. The primary objective was to determine the effects of molecular weight on the mechanical properties of the adhesive. Viscoelastic and nonlinear elastic constitutive equations were utilized to model the adhesive. Ludwik's and Crochet's relations were used to describe the experimental failure data. The effects of molecular weight changes on the above mentioned mechanical behavior were assessed. The viscoelastic Chase-Goldsmith and elastic nonlinear relations gave a good fit to the experimental stress strain behavior. Crochet's relations based on Maxwell and Chase-Goldsmith models were fit to delayed failure data. Ludwik's equations revealed negligible rate dependence. Ultimate stress levels and the safe levels for creep stresses were found to decrease as molecular weight was reduced.

Dembosky, Stanley K.; Sancaktar, Erol

1985-01-01

367

Calix[6]arene electron beam sensitivity and contrast dependence on functionalization and molecular weight  

NASA Astrophysics Data System (ADS)

Calixarenes are macrocyclic molecules that have shown high resolution as electron beam resists. Earlier work has demonstrated that the sensitivity can be increased by adding functional groups to the molecular rim of these ring-shaped molecules. However, these earlier studies used either unfunctionalized resists or ones that were fully functionalized. In this study, the number of functional groups added to a calix[6]arene structure was deliberately varied from zero to the maximum possible number of groups. This allowed direct observation of the effect of the number of attached groups on the sensitivity. Two different conformers were used; a cone conformer and the 1,2,3-alternate conformer. Both used xylenyl groups as bridging units, giving conformationally-locked monomers. The number of added allyl groups was varied from 0 to 8. The resulting nine resists were exposed and contrast curves were measured by AFM. This allowed measurement of both resist sensitivity and contrast. The sensitivity was found to be a strong function of the number of pendant groups. Also the effect of molecular weight on sensitivity was found for the heaviest resist, after the functional group effect saturated between four and six groups. These results and comparison with others will be discussed.

Spencer, Gregory; Ralls, Daniel; Wolfe, Stephan; Blanda, Michael; Bandyopadhyay, Anup

2011-10-01

368

A study of the formation of high molecular weight compounds during the decomposition of a field diatom population  

NASA Astrophysics Data System (ADS)

This work has investigated the possible formation of humic and fulvic acids, particularly high molecular weight moieties, in degrading diatom debris. The diatom debris was collected, freshly sedimented, from a well characterized natural field diatom population and allowed to degrade under conditions similar to those found at the sediment-water interface of many marine, organic-rich sediments. Samples of the detritus and overlying water were taken regularly over a period of 4 months and analysed for the presence of humic compounds. In the case of the detrital material, a sequential series of extractions were used. Molecular weight fractionation of the extracted humic material was carried out using Diaflow Ultrafiltration Membranes and two different fractionation methods have been compared. It appears that the choice of method may have an important effect on the determined distribution of the humic material, particularly when humic acid concentrations are low. High molecular weight (> 300 000- > 100 000) humic and fulvic acids were found in all the detrital samples, the content increasing with the period of decomposition. No evidence of any humic material was found in extracts of the living diatoms, the conclusion being that this material had been formed in situ during the degradation of the diatom debris. Most (65-90%) of the humic material was extracted from the detritus using a mild 0·05 M NaOH extraction at room temperature. Fulvic acids comprised approximately 90% of the total 0·05 M NaOH extraction, being composed mainly of either low molecular weight compounds (40-50% < 10000) or high molecular weight compounds (38-48% > 100000). Levels of humic acids were much lower and included a wide range of molecular weight fractions. The relevance of these findings to the possible origin of humic material in certain marine sediments is discussed.

Poutanen, E.-L.; Morris, R. J.

1983-08-01

369

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

PubMed

Many polar fishes synthesize a group of eight glycopeptides that exhibit a non-colligative lowering of the freezing point of water. These glycopeptides range in molecular weight between 2600 and 33 700. The largest glycopeptides [1-5] lower the freezing point more than the small ones on a weight basis and contain only two amino acids, alanine and threonine, with the disaccharide galactose-N-acetyl-galactosamine attached to threonine. The small glycopeptides, 6, 7, and 8, also lower the freezing point and contain proline, which periodically substitutes for alanine. Glycopeptides with similar antifreeze properties isolated from the saffron cod and the Atlantic tomcod contain an additional amino acid, arginine, which substitutes for threonine in glycopeptide 6. In this study we address the question of whether differences in amino acid composition or molecular weight between large and small glycopeptides are responsible for the reduced freezing point depressing capability of the low molecular weight glycopeptides. The results indicate that the degree of amino acid substitutions that occur in glycopeptides 6-8 do not have a significant effect on the unusual freezing point lowering and that the observed decrease in freezing point depression with smaller glycopeptides can be accounted for on the basis of molecular weight. PMID:7115772

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

1982-08-01

370

Effects of temperature and molecular weight on dissolution of cellulose in NaOH\\/urea aqueous solution  

Microsoft Academic Search

Dissolution of cellulose having different viscosity-average molecular weight (M\\u000a \\u000a ?\\u000a ) in 7 wt%NaOH\\/12 wt%urea aqueous solution at temperature from 60 to ?12.6°C was investigated with optical microscope, viscosity\\u000a measurements and wide X-ray diffraction (WXRD). The solubility (Sa) of cellulose in NaOH\\/urea aqueous solution strongly depended on the temperature, and molecular weight. Their Sa values increased with a decrease in temperature, and

Haisong Qi; Chunyu Chang; Lina Zhang

2008-01-01

371

Lower molecular weight hydrocarbon formation in an open flow system by Fischer Tropsch reaction. [in primitive solar system  

NASA Technical Reports Server (NTRS)

A Fischer Tropsch type mechanism has been proposed for the synthesis of organic compounds in the primitive solar system. The evidence for hydrocarbon formation, especially those of higher molecular weight, under simulated conditions of the early solar nebula has been presented (Studier et al., 1968, 1972; Gelpi et al., 1970). In this paper, we report studies on the formation of specifically the lower molecular weight hydrocarbons. By using an open flow reaction system and two closed systems, several factors which may affect the production of these compounds have been examined.

Hobo, T.; Ponnamperuma, C.; Hook, A. G.; Donn, B.

1978-01-01

372

Neutrophil-Activating Protein Mediates Adhesion of Helicobacter pylori to Sulfated Carbohydrates on High-Molecular-Weight Salivary Mucin  

PubMed Central

The in vitro binding of surface-exposed material and outer membrane proteins of Helicobacter pylori to high-molecular-weight salivary mucin was studied. We identified a 16-kDa surface protein which adhered to high-molecular-weight salivary mucin. This protein binds specifically to sulfated oligosaccharide structures such as sulfo-Lewis a, sulfogalactose and sulfo-N-acetyl-glucosamine on mucin. Sequence analysis of the protein proved that it was identical to the N-terminal amino acid sequence of neutrophil-activating protein. Moreover, this adhesin was able to bind to Lewis x blood group antigen. PMID:9453593

Namavar, Ferry; Sparrius, Marion; Veerman, Enno C. I.; Appelmelk, Ben J.; Vandenbroucke-Grauls, Christina M. J. E.

1998-01-01

373

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

PubMed

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. PMID:18413136

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

2007-12-01

374

Simultaneous determination of protein aggregation, degradation, and absolute molecular weight by size exclusion chromatography-multiangle laser light scattering.  

PubMed

The feasibility of size exclusion chromotography (SEC)-multiangle laser-light scattering as a technique to investigate aggregation and degradation of glycosylated and nonglycosylated proteins, and antibodies under various conditions such as addition of detergent, changes in pH, and variation of protein concentration and heat stress temperature was examined. Separation of proteins and their aggregates was performed using SEC-high-performance liquid chromatography. Detection of analytes was carried out with on-line UV, refractive index, and multiangle laser light-scattering detectors. Quantification and molecular weight determination were performed using commercial software. Aggregation and degradation were examined under various conditions and quantitative results are presented for bovine serum albumin, choriogonadotropin, glyceraldehyde-3-phosphate dehydrogenase, Herceptin, and ReoPro. This method can simultaneously determine both the quantities and the molecular weights of macromolecules from a single injection. The determination of molecular weight is absolute which avoids misleading results caused by molecular shape or interactions with the column matrix. This technique is valuable not only for assessing the extent of aggregation but also for effectively monitoring molecule degradation as evidenced by molecular weight reduction and change in monomer amount. PMID:16839514

Ye, Hongping

2006-09-01

375

Dependence of pH, Molecular Weight, and Concentration of Surfactant in Ceria Slurry on Saturated Nitride Removal Rate in Shallow Trench Isolation Chemical Mechanical Polishing  

NASA Astrophysics Data System (ADS)

We have investigated how controlling the pH, molecular weight, and concentration of the surfactant in ceria slurry affects the nitride film loss and oxide-to-nitride selectivity in the shallow trench isolation (STI) chemical mechanical polishing (CMP) process. We found that for a surfactant with a higher molecular weight, the oxide removal rate markedly decreased as the surfactant concentration increased, but in the case of a lower molecular weight, the removal rate only slightly decreased. In addition, with increasing surfactant concentration and addition of surfactant with the same molecular weight, the nitride removal rates for all slurries markedly decreased and very quickly saturated at a lower surfactant pH. Moreover, with an increase in the surfactant concentration from 0.1 to 0.3 wt %, the slurries whose surfactants had a medium or the lowest molecular weight maintained higher nitride removal rates than did the slurry whose surfactant had the highest molecular weight.

Kang, Hyun-Goo; Lee, Myung-Yoon; Park, Hyung-Soon; Paik, Ungyu; Park, Jea-Gun

2005-07-01

376

Determination of molecular weight and molecular sizes of polymers by high temperature gel permeation chromatography with a static and dynamic laser light scattering detector  

Microsoft Academic Search

Flow-mode static and dynamic laser light scattering (SLS\\/DLS) studies of polymers, including polystyrene, polyethylene, polypropylene and poly(dimethylsiloxane) (PDMS), in 1,2,4-trichlorobenzene (TCB) at 150 °C were performed on a high temperature gel permeation chromatography (GPC) coupled with a SLS\\/DLS detector. Both absolute molecular weight (M) and molecular sizes (radius of gyration, Rg and hydrodynamic radius, Rh) of polymers eluting from the

Yonggang Liu; Shuqin Bo; Yejuan Zhu; Wenhe Zhang

2003-01-01

377

MRI detection of VEGFR2 in vivo using a low molecular weight peptoid-(Gd)8-dendron for targeting  

PubMed Central

The synthesis of a polylysine dendron containing eight GdDOTA units conjugated to peptoid dimer known to have a high affinity for the vascular endothelial growth factor receptor 2 (VEGFR2) is described. This simple low molecular weight system with a molecular r1 relaxivity of ~48 mM?1s?1 is shown to enhance MR images of tumors grown in mice in vivo. PMID:20795620

De León-Rodríguez, Luis M.; Lubag, Angelo; Udugamasooriya, D. Gomika; Proneth, Bettina; Brekken, Rolf A.; Sun, Xiankai; Kodadek, Thomas; Sherry, A. Dean

2010-01-01

378

MRI detection of VEGFR2 in vivo using a low molecular weight peptoid-(Gd)8-dendron for targeting.  

PubMed

The synthesis of a polylysine dendron containing eight GdDOTA units conjugated to a peptoid dimer known to have a high affinity for the vascular endothelial growth factor receptor 2 (VEGFR2) is described. This simple low molecular weight system with a molecular r(1) relaxivity of ?48 mM(-1) s(-1) is shown to enhance MR images of tumors grown in mice in vivo. PMID:20795620

De León-Rodríguez, Luis M; Lubag, Angelo; Udugamasooriya, D Gomika; Proneth, Bettina; Brekken, Rolf A; Sun, Xiankai; Kodadek, Thomas; Dean Sherry, A

2010-09-22

379

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

PubMed

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. PMID:22866871

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

2012-09-01

380

Beta-Glucanase Activity and its Impact on Beta-Glucan Molecular Weight Degradation in Cereal Products Fortified with Beta-Glucan .  

E-print Network

??Health benefits of high molecular weight (MW) ?-glucans are well documented. Therefore, understanding and controlling depolymerization of ?-glucan in baked products, would increase the effectiveness… (more)

Vatandoust, Azadeh

2012-01-01

381

ORG 10172: a low molecular weight heparinoid anticoagulant with a long half-life in man.  

PubMed Central

ORG 10172 is a heparinoid with mean molecular weight 6500 daltons. Intravenous bolus injections of ORG 10172 were compared with placebo and heparin injections in 91 separate studies in 83 healthy male subjects. 6400 units ORG 10172 produced a mean maximum change of 14.7 s in kaolin cephalin time (c.f. greater than 120 s for 5000 units heparin). Changes in prothrombin time were minimal (1.6 s for 6400 units ORG 10172 and 4.5 s after 5000 units heparin). A dose-related increase in bleeding time occurred after ORG 10172 and at high doses (greater than 3200 units) some secondary bleeding, which was never serious, occurred at between 1 and 4 h after incision. A dose-dependent reduction in ex vivo platelet adhesiveness was found at 10 min after ORG 10172 injection. ORG 10172 promoted a much smaller release of lipoprotein lipase as compared with heparin. The effect of ORG 10172 on plasma factor Xa activity (one measure of its action) was described by a biexponential decay with a mean distribution half-life of 2.34 (s.e. mean 0.16) h and mean disposition half-life of 17.6 (s.e. mean 1.1) h. It thus has a much longer duration of effect than heparin. There was a linear relationship of plasma anti-Xa response to increasing dose although there was some variability only partly explained by differences in body weight or surface area. ORG 10172 administration by bolus intravenous injection was well tolerated and there was no evidence of adverse effects on clinical chemistry or haematology tests. PMID:3606928

Bradbrook, I D; Magnani, H N; Moelker, H C; Morrison, P J; Robinson, J; Rogers, H J; Spector, R G; Van Dinther, T; Wijnand, H

1987-01-01

382

Hypervelocity Impact Experiments on Epoxy/Ultra-High Molecular Weight Polyethylene Composite Panels Reinforced with Nanotubes  

NASA Technical Reports Server (NTRS)

Advanced composites with multi-functional capabilities are of great interest to the designers of aerospace structures. Polymer matrix composites (PMCs) reinforced with high strength fibers provide a lightweight and high strength alternative to metals and metal alloys conventionally used in aerospace architectures. Novel reinforcements such as nanofillers offer potential to improve the mechanical properties and add multi-functionality such as radiation resistance and sensing capabilities to the PMCs. This paper reports the hypervelocity impact (HVI) test results on ultra-high molecular weight polyethylene (UHMWPE) fiber composites reinforced with single-walled carbon nanotubes (SWCNT) and boron nitride nanotubes (BNNT). Woven UHMWPE fabrics, in addition to providing excellent impact properties and high strength, also offer radiation resistance due to inherent high hydrogen content. SWCNT have exceptional mechanical and electrical properties. BNNT (figure 1) have high neutron cross section and good mechanical properties that add multi-functionality to this system. In this project, epoxy based UHMWPE composites containing SWCNT and BNNT are assessed for their use as bumper shields and as intermediate plates in a Whipple Shield for HVI resistance. Three composite systems are prepared to compare against one another: (I) Epoxy/UHMWPE, (II) Epoxy/UHMWPE/SWCNT and (III) Epoxy/UHMWPE/SWCNT/BNNT. Each composite is a 10.0 by 10.0 by 0.11 cm3 panel, consisting of 4 layers of fabrics arranged in cross-ply orientation. Both SWCNT and BNNT are 0.5 weight % of the fabric preform. Hypervelocity impact tests are performed using a two-stage light gas gun at Rice University

Khatiwada, Suman; Laughman, Jay W.; Armada, Carlos A.; Christiansen, Eric L.; Barrera, Enrique V.

2012-01-01

383

Three high molecular weight protease inhibitors of rat plasma. Isolation, characterization, and acute phase changes.  

PubMed

Rat blood plasma contains three high molecular weight thiol ester-containing proteinase inhibitors, alpha 1-macroglobulin (alpha 1M), alpha 1-inhibitor III (alpha 1I3), and alpha 2-macroglobulin (alpha 2M). Rat serums have been analyzed using a two-dimensional gel electrophoretic technique which optimizes recovery of high molecular weight proteins. alpha 1M, and (alpha beta)4-tetramer in native solution, separated in the second sodium dodecyl sulfate-containing electrophoretic dimension as a disulfide-linked (alpha beta)2-dimer with an approximate Mr of 360 kDa. alpha 1I3 separated in the gels as a single 190-kDa polypeptide. It is also a monomer in native solution by ultracentrifugation criteria. Native rat alpha 2M is a tetramer, but it separates in the gels as a disulfide-linked dimer with an Mr of approximately 360 kDa. The kinetics of changes in concentration of these proteins during the induction of polyarthritis was also measured by quantitative immunoelectrophoresis. In rats with adjuvant-induced polyarthritis, the concentration of alpha 1I3 dramatically decreases and alpha 2M appears and continues to increase in a biphasic manner for 2 weeks. The alpha 1M concentration remains relatively constant. All three macroglobulins were purified utilizing modern rapid chromatographic techniques, and parallel comparisons of their native physicochemical properties were carried out. The N-terminal sequence of the alpha-chain of rat alpha 1M was also shown to share sequence homology with that of alpha 2M. In agreement, Esnard et al. (Esnard, F., Gutman, N., El Moujahed, A., and Gauthier, F. (1985) FEBS Lett. 182, 125-129) recently reported that alpha 1I3 also contains a thiol ester bond, as do alpha 1M and alpha 2M, since it reacts covalently with [14C]methylamine and is cleaved autolytically at 80 degrees C. We have examined negatively stained preparations of native, trypsin-treated, and methylamine-treated human alpha 2M, rat alpha 2M, and rat alpha 1M in the electron microscope. Trypsin appears to convert globular ring-shaped native molecules to rectangular box-like structures, in agreement with the conclusions of a recent report on human alpha 2M (Tapon-Bretaudiere, J., Bros, A., Couture-Tosi, E., and Delain, E. (1985) EMBO J. 4, 85-89). PMID:2432067

Lonberg-Holm, K; Reed, D L; Roberts, R C; Hebert, R R; Hillman, M C; Kutney, R M

1987-01-01

384

Molecular weight, tertiary structure, water binding and colon behaviour of ispaghula husk fibre.  

PubMed

Molecular variables, using aqueous and alkaline extracts, of the polysaccharide from ispaghula husk (IH) were examined using gel-permeation chromatography linked to multi-angle laser light scattering. Progressive extraction can yield a component with a molecular weight (MW)value up to about 7 x 106 Da, and gels, which accompany the extraction, have MW ranging from 10-20 x 106 Da. To mimic the polysaccharide degradation, particularly in the colon, the solid IH was degraded progressively using ionising radiation. A chain break occurs every 7.5 kGy in NaOH and every 15 kGy in water. The solid-state matrix is opened by the radiation to yield increased visco-elasticity of the aqueous extracts at critical radiation doses, before further degradation occurs after about 12 kGy. Differential scanning calorimetry is used to study the mechanism of interaction of water with IH. The first water to be taken up is non-freezing water and represents about twelve water molecules/disaccharide unit of the polysaccharide. As the water content is increased, the water becomes bound to the polysaccharide and freezes and melts at a temperature different from free water. This water is thermodynamically distinguishable from free water. It forms amorphous ice on cooling which crystallises exothermically and subsequently melts endothermically. Saturation occurs at a water content of 2-3 g water/g polymer, showing that about 60% of the water in the system is 'bound'. The most surprising conclusion is that despite the fact that the IH swells in water to form a solid and stiff gel, the greater part of that water in the gel is still free and behaves like liquid water. PMID:12756969

Al-Assaf, Saphwan; Phillips, Glyn O; Williams, Peter A; Takigami, Shoji; Dettmar, Peter; Havler, Michael

2003-02-01

385

Antithrombin binding of low molecular weight heparins and inhibition of factor Xa.  

PubMed

Fluorescence and stopped flow methods were used to compare clinically used heparins with regard to their ability to bind to antithrombin and to accelerate the inactivation of factor Xa. Titration of antithrombin with both low molecular weight heparin (LMWH) (enoxaparin, fragmin and ardeparin) and unfractionated heparin (UFH) produced an equivalent fluorescence increase and indicates similar affinity of all heparin preparations to antithrombin. However, relative to UFH enoxaparin, the LMWH with the smallest average molecular mass, contained only 12% material with high affinity for antithrombin. The rate of factor Xa inhibition by antithrombin increased with the concentration of the examined heparins to the same limiting value, but the concentration required for maximal acceleration depended on the preparation. According to these data the high affinity fraction of the heparin preparations increased the intrinsic fluorescence and inhibitory activity equally without additional effects by variations in chain length and chemical composition. In contrast, in the presence of Ca UFH accelerated the inhibition of factor Xa by antithrombin 10-fold more efficiently than comparable concentrations of the high affinity fractions of enoxaparin and fragmin. The bell-shaped dependence of this accelerating effect suggests simultaneous binding of both proteins to heparin. In conclusion, under physiologic conditions the anti-factor Xa activity of heparin results from a composite effect of chain length and the content of material with high affinity to antithrombin. Thus, the reduced antithrombotic activity of LMWH relative to UFH results from a smaller content of high affinity material and the absence of a stimulating effect of calcium. PMID:11287128

Lin, P; Sinha, U; Betz, A

2001-04-01

386

Identification and Characterization of High-Molecular-Weight Glutenin Subunits from Agropyron intermedium  

PubMed Central

High-molecular-weight glutenin subunit (HMW-GS) is a primary determinant of processing quality of wheat. Considerable progress has been made in understanding the structure, function and genetic regulation of HMW-GS in wheat and some of its related species, but less is known about their orthologs in Agropyron intermedium, a useful related species for wheat improvement. Here seven HMW-GSs in Ag. intermedium were identified using SDS-PAGE and Western blotting experiments. Subsequently, the seven genes (Glu-1Aix1?4 and Glu-1Aiy1?3) encoding the seven HMW-GSs were isolated using PCR technique with degenerate primers, and confirmed by bacterial expression and Western blotting. Sequence analysis indicated that the seven Ag. intermedium HMW-GSs shared high similarity in primary structure to those of wheat, but four of the seven subunits were unusually small compared to the representatives of HMW-GS from wheat and two of them possessed extra cysteine residues. The alignment and clustering analysis of deduced amino acid sequences revealed that 1Aix1 and 1Aiy1 subunits had special molecular structure, belonging to the hybrid type compounding between typical x- and y-type subunit. The xy-type subunit 1Aix1 is composed of the N-terminal of x-type and C-terminal of y-type, whereas yx-type subunit 1Aiy1 comprises the N-terminal of y-type and C-terminal of x-type. This result strongly supported the hypothesis of unequal crossover mechanism that might generate the novel coding sequence for the hybrid type of HMW-GSs. In addition to the aforementioned, the other novel characteristics of the seven subunits were also discussed. Finally, phylogenetic analysis based on HMW-GS genes was carried out and provided new insights into the evolutionary biology of Ag. intermedium. PMID:24503781

Cao, Shuanghe; Li, Zhixin; Gong, Caiyan; Xu, Hong; Yang, Ran; Hao, Shanting; Wang, Xianping; Wang, Daowen; Zhang, Xiangqi

2014-01-01

387

Identification and characterization of high-molecular-weight glutenin subunits from Agropyron intermedium.  

PubMed

High-molecular-weight glutenin subunit (HMW-GS) is a primary determinant of processing quality of wheat. Considerable progress has been made in understanding the structure, function and genetic regulation of HMW-GS in wheat and some of its related species, but less is known about their orthologs in Agropyron intermedium, a useful related species for wheat improvement. Here seven HMW-GSs in Ag. intermedium were identified using SDS-PAGE and Western blotting experiments. Subsequently, the seven genes (Glu-1Aix1 ? 4 and Glu-1Aiy1 ? 3) encoding the seven HMW-GSs were isolated using PCR technique with degenerate primers, and confirmed by bacterial expression and Western blotting. Sequence analysis indicated that the seven Ag. intermedium HMW-GSs shared high similarity in primary structure to those of wheat, but four of the seven subunits were unusually small compared to the representatives of HMW-GS from wheat and two of them possessed extra cysteine residues. The alignment and clustering analysis of deduced amino acid sequences revealed that 1Aix1 and 1Aiy1 subunits had special molecular structure, belonging to the hybrid type compounding between typical x- and y-type subunit. The xy-type subunit 1Aix1 is composed of the N-terminal of x-type and C-terminal of y-type, whereas yx-type subunit 1Aiy1 comprises the N-terminal of y-type and C-terminal of x-type. This result strongly supported the hypothesis of unequal crossover mechanism that might generate the novel coding sequence for the hybrid type of HMW-GSs. In addition to the aforementioned, the other novel characteristics of the seven subunits were also discussed. Finally, phylogenetic analysis based on HMW-GS genes was carried out and provided new insights into the evolutionary biology of Ag. intermedium. PMID:24503781

Cao, Shuanghe; Li, Zhixin; Gong, Caiyan; Xu, Hong; Yang, Ran; Hao, Shanting; Wang, Xianping; Wang, Daowen; Zhang, Xiangqi

2014-01-01

388

Homology modeling and molecular dynamics simulations of the N-terminal domain of wheat high molecular weight glutenin subunit 10.  

PubMed

High molecular weight glutenin subunits (HMW-GS) are of a particular interest because of their biomechanical properties, which are important in many food systems such as breadmaking. Using fold-recognition techniques, we identified a fold compatible with the N-terminal domain of HMW-GS Dy10. This fold corresponds to the one adopted by proteins belonging to the cereal inhibitor family. Starting from three known protein structures of this family as templates, we built three models for the N-terminal domain of HMW-GS Dy10. We analyzed these models, and we propose a number of hypotheses regarding the N-terminal domain properties that can be tested experimentally. In particular, we discuss two possible ways of interaction between the N-terminal domains of the y-type HMW glutenin subunits. The first way consists in the creation of interchain disulfide bridges. According to our models, we propose two plausible scenarios: (1) the existence of an intrachain disulfide bridge between cysteines 22 and 44, leaving the three other cysteines free of engaging in intermolecular bonds; and (2) the creation of two intrachain disulfide bridges (involving cysteines 22-44 and cysteines 10-55), leaving a single cysteine (45) for creating an intermolecular disulfide bridge. We discuss these scenarios in relation to contradictory experimental results. The second way, although less likely, is nevertheless worth considering. There might exist a possibility for the N-terminal domain of Dy10, Nt-Dy10, to create oligomers, because homologous cereal inhibitor proteins are known to exist as monomers, homodimers, and heterooligomers. We also discuss, in relation to the function of the cereal inhibitor proteins, the possibility that this N-terminal domain has retained similar inhibitory functions. PMID:12493826

Cazalis, Roland; Aussenac, Thierry; Rhazi, Larbi; Marin, Antoine; Gibrat, Jean-François

2003-01-01

389

Homology modeling and molecular dynamics simulations of the N-terminal domain of wheat high molecular weight glutenin subunit 10  

PubMed Central

High molecular weight glutenin subunits (HMW-GS) are of a particular interest because of their biomechanical properties, which are important in many food systems such as breadmaking. Using fold-recognition techniques, we identified a fold compatible with the N-terminal domain of HMW-GS Dy10. This fold corresponds to the one adopted by proteins belonging to the cereal inhibitor family. Starting from three known protein structures of this family as templates, we built three models for the N-terminal domain of HMW-GS Dy10. We analyzed these models, and we propose a number of hypotheses regarding the N-terminal domain properties that can be tested experimentally. In particular, we discuss two possible ways of interaction between the N-terminal domains of the y-type HMW glutenin subunits. The first way consists in the creation of interchain disulfide bridges. According to our models, we propose two plausible scenarios: (1) the existence of an intrachain disulfide bridge between cysteines 22 and 44, leaving the three other cysteines free of engaging in intermolecular bonds; and (2) the creation of two intrachain disulfide bridges (involving cysteines 22–44 and cysteines 10–55), leaving a single cysteine (45) for creating an intermolecular disulfide bridge. We discuss these scenarios in relation to contradictory experimental results. The second way, although less likely, is nevertheless worth considering. There might exist a possibility for the N-terminal domain of Dy10, Nt-Dy10, to create oligomers, because homologous cereal inhibitor proteins are known to exist as monomers, homodimers, and heterooligomers. We also discuss, in relation to the function of the cereal inhibitor proteins, the possibility that this N-terminal domain has retained similar inhibitory functions. PMID:12493826

Cazalis, Roland; Aussenac, Thierry; Rhazi, Larbi; Marin, Antoine; Gibrat, Jean-François

2003-01-01

390

Potential of the biopolymer chitosan with different molecular weights to control postharvest gray mold of tomato fruit  

Microsoft Academic Search

Gray mold caused by Botrytis cinerea (Pers.) is the most economically important postharvest disease of fruit and vegetables at harvest and during storage. Therefore the current study was conducted to investigate the effectiveness of chitosan with different molecular weights on gray mold in vitro and in vivo in tomato fruit (Solanum lycopersicum L. var. lycopersicum) stored at different temperatures. In

Mohamed E. I. Badawy; Entsar I. Rabea

2009-01-01

391

Bone-tissue-engineering material poly(propylene fumarate): correlation between molecular weight, chain dimensions, and physical properties.  

PubMed

Poly(propylene fumarate) (PPF) is an important biodegradable and cross-linkable polymer designed for bone-tissue-engineering applications. For the first time we report the extensive characterization of this biomaterial including molecular weight dependences of physical properties such as glass transition temperature Tg, thermal degradation temperature Td, density rho, melt viscosity eta0, hydrodynamic radius RH, and intrinsic viscosity [eta]. The temperature dependence of eta0 changes progressively with molecular weight, whereas it can be unified when the temperature is normalized to Tg. The plateau modulus and entanglement molecular weight Me have been obtained from the rheological master curves. A variety of chain microstructure parameters such as the Mark-Houwink-Sakurada constants K and alpha, characteristic ratio Cinfinity, unperturbed chain dimension r0(2)/M, packing lengthp, Kuhn length b, and tube diameter a have been deduced. Further correlation between the microstructure and macroscopic physical properties has been discussed in light of recent progress in polymer dynamics to supply a better understanding about this unsaturated polyester to advance its biomedical uses. The molecular weight dependence of Tg for six polymer species including PPF has been summarized to support that Me is irrelevant for the finite length effect on the glass transition, whereas surprisingly these polymers can be divided into two groups when their normalized Tg is plotted simply against Mw to indicate the deciding roles of inherent chain properties such as chain fragility, intermolecular cooperativity, and chain end mobility. PMID:16768422

Wang, Shanfeng; Lu, Lichun; Yaszemski, Michael J

2006-06-01

392

Effect of high molecular weight glutenin subunit composition in common wheat on dough properties and steamed bread quality  

Technology Transfer Automated Retrieval System (TEKTRAN)

Steamed bread is a popular staple in Asia with different flour quality requirements from pan bread. Little is known about how glutenin characteristics affect steamed bread quality. This work investigated how deletions of high molecular weight glutenin subunits (HMW-GS) influence gluten properties an...

393

Inhibition of Helicobacter pylori Adhesion to Human Gastric Mucus by a High-Molecular-Weight Constituent of Cranberry Juice  

Microsoft Academic Search

A high–molecular–weight constituent of cranberry juice has been found to inhibit the sialyllactose specific adhesion of Helicobacter pylori strains to immobilized human mucus, erythrocytes, and cultured gastric epithelial cells. Different isolates of H. pylori differ in thenaffinity to the cranberry juice constituent. Cranberry juice may also inhibit adhesion of bacteria to the stomach in vivo, and may prove useful for

Ora Burger; Ervin Weiss; Nathan Sharon; Mina Tabak; Ishak Neeman; Itzhak Ofek

2002-01-01

394

Effect of frozen storage on molecular weight, size distribution and conformation of gluten by SAXS and SEC-MALLS.  

PubMed

In this study, the effects of frozen (-18 °C) storage time on molecular weight, size distribution, conformation, free amino groups and free sulfhydryl groups of gluten were studied by small-angle X-ray scattering (SAXS), multi-angle laser light scattering (MALLS) in conjunction with a size exclusion chromatography (SEC) and spectrophotometrically. The results showed that the gluten dissolved in 50 mM acetic acid appeared to be similar to quasi-spherical of the chain conformation and the slope of the conformation plot decreased during the storage. Both the molecular weight and radius of gyration of the frozen gluten decreased with the storage time showing a depolymerization in the high molecular weight fraction of gluten (10(5) Da ~ 10(9) Da). Therefore, at constant molecular weight the change of the chain conformation did not show a clear correlation with the storage time. The free amino groups content changed little and the free sulfhydryl groups content of the gluten increased from 9.8 ?mol/g for the control to 12.87 ?mol/g for 120-day-stored gluten, indicating that the water redistribution and ice recrystallization lead to the breakage of the disulphide bonds and may be one of the reasons for the depolymerization of gluten polymer. PMID:22692241

Zhao, Lei; Li, Lin; Liu, Guo-Qin; Liu, Xing-Xun; Li, Bing

2012-01-01

395

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

Microsoft Academic Search

This work aimed to evaluate, in vitro, the capability of roots of two salt marsh plants to release low molecular weight organic acids (LMWOAs) and to ascertain whether Cu contamination would stimulate or not organic acids exudation. The sea rush Juncus maritimus and the sea-club rush Scirpus maritimus, both from the lower Douro river estuary (NW Portugal), were used. Plants

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

2010-01-01

396

Organic Solar Cells Using a High-Molecular-Weight Benzodithiophene-Benzothiadiazole Copolymer with an Efficiency of 9.4%  

PubMed

A high molecular weight donor-acceptor conjugated polymer is synthesized using Suzuki polycondensation method. Using this polymer, a single junction bulk heterojunction solar cell is fabricated giving a power conversion efficiency of 9.4% using a fullerene-modified ZnO interlayer at the cathode contact. PMID:25429716

Subbiah, Jegadesan; Purushothaman, Balaji; Chen, Ming; Qin, Tianshi; Gao, Mei; Vak, Doojin; Scholes, Fiona H; Chen, Xiwen; Watkins, Scott E; Wilson, Gerard J; Holmes, Andrew B; Wong, Wallace W H; Jones, David J

2014-11-27

397

Design of water-soluble, thiol-reactive polymers of controlled molecular weight: a novel multivalent scaffold  

Microsoft Academic Search

Multivalent molecules, i.e. scaffolds presenting multiple copies of a suitable ligand, constitute an emerging class of nanoscale therapeutics. We present a novel approach for the design of multivalent ligands, which allows the biofunctionalization of polymers with proteins or peptides in a controlled orientation. It consists of the synthesis of water-soluble, activated polymer scaffolds of controlled molecular weight, which can be

Alvaro Carrillo; Kunal V. Gujraty; Prakash R. Rai; Ravi S. Kane

2005-01-01

398

INFLUENCE OF GLYCOSIDIC LINKAGES AND MOLECULAR WEIGHT ON THE FERMENTATION OF MALTOSE-BASED OLIGOSACCHARIDES BY GUT BACTERIA  

Technology Transfer Automated Retrieval System (TEKTRAN)

A structure-function study was carried out to increase knowledge of how glycosidic linkages and molecular weight of carbohydrates contribute towards the selectivity of fermentation by gut bacteria. Oligosaccharides with maltose as the common carbohydrate source were used. Potentially prebiotic alt...

399

Investigation of molecular weight distribution of LBG galactomannan for flours prepared from individual seeds, mixtures, and commercial samples  

Microsoft Academic Search

The molecular weight distribution has been determined for the galactomannan solubilized from three types of locust bean gum (LBG) flours: single carob seeds, mixtures, and a range of commercial products. To prepare crude endosperm flours from carob seeds with minimal galactomannan degradation, a new extraction and milling method was developed. The method consists of applying a brief thermal shock to

Michael A. Pollard; Roger Kelly; Peter A. Fischer; Erich J. Windhab; Barbara Eder; Renato Amadò

2008-01-01

400

Effects of experimental conditions on the mechanism of particle aggregation in protein precipitation by polyelectrolytes with a high molecular weight  

Microsoft Academic Search

Lysozyme precipitation by polyacrylic acid (PAA), especially with a high molecular weight of 4×106, where the polymer bridging effect of PAA is thought to be dominant in the particle aggregation of lysozyme precipitates, was carried out to investigate the relationship between the bridging effect of PAA and the operation conditions in a semi-batch reactor. The bridging effect of PAA was

Woon-Soo Kim; Izumi Hirasawa; Woo-Sik Kim

2001-01-01

401

Molecular weight distribution of proteins in hard red spring wheat: Relationship to quality parameters and intra-sample uniformity  

Technology Transfer Automated Retrieval System (TEKTRAN)

Molecular weight distribution (MWD) of proteins extracted from hard spring wheat grain was analyzed by size exclusion HPLC to investigate associations with wheat and breadmaking quality characteristics. Certain protein fractions were found to be related to associations between wheat and breadmaking ...

402

Friction and wear behavior of ultra-high molecular weight polyethylene as a function of polymer crystallinity  

Microsoft Academic Search

In this study the friction, wear and surface mechanical behavior of medical-grade ultra-high molecular weight polyethylene (UHMWPE) (GUR 1050 resin) were evaluated as a function of polymer crystallinity. Crystallinity was controlled by heating UHMWPE to a temperature above its melting point and varying the hold time and cooling rates. The degree of crystallinity of the samples was evaluated using differential

K. S. Kanaga Karuppiah; Angela L. Bruck; Sriram Sundararajan; Jun Wang; Zhiqun Lin; Zhi-Hui Xu; Xiaodong Li

2008-01-01

403

Malate dehydrogenase isozymes in flax genotroph leaves: Differences in apparent molecular weight and charge between and within L and S  

Microsoft Academic Search

Ferguson plots demonstrated that corresponding malate dehydrogenase (MDH) isozymes of Durrant's L and S flax genotrophs differ in apparent molecular weight (MW) and also in net negative charge. The MW differences explain heritable differences in electrophoretic relative mobility (Rm) between corresponding L and S isozymes. The MW for each MDH isozyme was higher for L than for S and resulted

M. A. Fieldes; B. Dixon

1988-01-01

404

Temperature effects on polymer-carbon composite sensors: Evaluating the role of polymer molecular weight and carbon loading  

Microsoft Academic Search

We report the effect of temperature coupled with varying polymer molecular weight and carbon loadings on the performance of polymer-carbon black composite films, used as sensing media in the JPL Electronic Nose (ENose). While bulk electrical properties of polymer composites have been studied, with mechanisms of conductivity described by connectivity and tunneling, it is not fully understood how environmental conditions

M. L. Homer; J. R. Lim; K. Manatt; A. Kisor; A. M. Manfreda; L. Lara; A. D. Jewell; S.-P. S. Yen; H. Zhou; A. V. Shevade; M. A. Ryan

2003-01-01

405

Effects of machining on tribological behavior of ultra high molecular weight polyethylene (UHMWPE) under dry reciprocating sliding  

Microsoft Academic Search

This paper presents a study of the machining effect on tribological properties of ultra high molecular weight polyethylene (UHMWPE) in terms of coefficient of friction and wear factor under dry reciprocating sliding conditions. Machining parameters include cutting speed, feed rate and depth of cut. Polymeric structure of the semicrystalline polymer was characterized using differential scanning calorimetry (DSC). Changes in polymeric

J Song; P Liu; M Cremens; P Bonutti

1999-01-01

406

A MURINE MODEL FOR LOW MOLECULAR WEIGHT CHEMICALS: DIFFERENTIATION OF RESPIRATORY SENSITIZERS (TMA) FROM CONTACT SENSITIZERS (DNFB)  

EPA Science Inventory

Exposure to low molecular weight (LMW) chemicals contributes to both dermal and respiratory sensitization and is an important occupational health problem. Our goal was to establish an in vivo murine model for hazard identification of LMW chemicals that have the potential to indu...

407

Study on the preparation and characterization of ultra-high molecular weight polyethylene–carbon nanotubes composite fiber  

Microsoft Academic Search

The ultra-high molecular weight polyethylene (UHMWPE)–carbon nanotubes (CNTs) composite fibers were prepared by gel spinning. To realize the homogeneous dispersion and good load transfer between the CNTs and the polymer matrix, the purification and functionalization of CNTs were carried out. TEM, SEM, XRD, IR were used to characterize the CNTs, their dispersion in the matrix and the functional group changes

Yanping Wang; Ruiling Cheng; Linli Liang; Yimin Wang

2005-01-01

408

Accumulation of low molecular weight (bleomycin detectable) iron in bone marrow cells of rats after benzene exposure  

Microsoft Academic Search

An accumulation of low molecular weight (LMW) bleomycin detectable iron in the bone marrow was observed after administration of benzene (IP 0.5 ml\\/kg, daily) for 5 and 10 days in female albino rats. However, this LMW iron was not detectable in the bone marrow of rats from the control group. Studies of bone marrow fractionation showed that the maximum accumulation

K. P. Pandya; G. S. Rao; S. Khan; R. Krishnamurthy

1990-01-01

409

Enhanced Gene Delivery Mediated by Low Molecular Weight Chitosan/DNA Complexes: Effect of pH and Serum  

E-print Network

RESEARCH Enhanced Gene Delivery Mediated by Low Molecular Weight Chitosan/DNA Complexes: Effect on the transfection process of chitosan­DNA complexes, with the objective of maximizing their efficiency 24­40 h period. Cytotoxicity of chitosan/ DNA complexes was also considerably lower than Lipo

Buschmann, Michael

410

A common standard is inappropriate for determining the potency of ultra low molecular weight heparins such as semuloparin and bemiparin  

Microsoft Academic Search

IntroductionLower low-molecular-weight heparins are being developed to improve on the safety and efficacy of antithrombotic therapy. Semuloparin and bemiparin are two depolymerized heparins produced by distinct manufacturing processes. The objective of this investigation was to determine whether a common standard could be used to define their potency.

Walter P. Jeske; Debra Hoppensteadt; Angel Gray; Jeanine M. Walenga; Josephine Cunanan; Lauren Myers; Jawed Fareed; Alain Bayol; Hélène Rigal; Christian Viskov

2011-01-01

411

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

PubMed Central

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

Muthukumar, M.

2012-01-01

412

HPMA copolymer-doxorubicin conjugates: The effects of molecular weight and architecture on biodistribution and in vivo activity.  

PubMed

The molecular weight and molecular architecture of soluble polymer drug carriers significantly influence the biodistribution and anti-tumour activities of their doxorubicin (DOX) conjugates in tumour-bearing mice. Biodistribution of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-DOX conjugates of linear and star architectures were compared in EL4 T-cell lymphoma-bearing mice. Biodistribution, including tumour accumulation, and anti-tumour activity of the conjugates strongly depended on conjugate molecular weight (MW), polydispersity, hydrodynamic radius (R(h)) and molecular architecture. With increasing MW, renal clearance decreased, and the conjugates displayed extended blood circulation and enhanced tumour accumulation. The linear conjugates with flexible polymer chains were eliminated by kidney clearance more quickly than the highly branched star conjugates with comparable MWs. Interestingly, the data suggested different mechanisms of renal filtration for star and linear conjugates. Only star conjugates with MWs below 50,000g.mo(-1) were removed by kidney filtration, while linear polymer conjugates with MWs near 70,000g.mol(-1), exceeding the generally accepted limit for renal elimination, were detected in the urine 36-96h after injection. Additionally, survival of tumour-bearing mice was strongly dependent on molecular weight and polymer conjugate architecture. Treatment of mice with the lower MW conjugate at a dose of 10mg DOX eq./kg resulted in 12% long-term surviving animals, while treatment with the corresponding star conjugate enabled 75% survival of animals. PMID:22759979

Etrych, Tomáš; Subr, Vladimír; Strohalm, Ji?í; Sírová, Milada; Ríhová, Blanka; Ulbrich, Karel

2012-12-28

413

[Influence of high molecular weight polyethylene on viability of osteoblasts and new bone formation].  

PubMed

To investigate the influence of high molecular weight polyethylene (HMWP) on the viability of osteoblasts and new bone formation in the process of fracture healing, the osteoblasts derived from adult human bone marrow were cultured in HMWP maceration extract and normal culture medium. The viability of the osteoblasts was measured by MTT assay, and the function of the osteoblasts was detected by use of alkaline phosphatase test kit. The locked double-plating (steel plate and HMWP plate) was implanted and fixed at the artificial fracture of distal femur of dogs. Specimens were gained at 3, 6, 9 and 12 weeks postoperatively, examined with macroscopy, microscope and scanning electron microscope (SEM). The results showed that HMWP did no harm to osteoblasts. There is no significant difference in activities of proliferation and alkaline phosphatase between HMWP maceration extract and normal culture medium at each observation time of at 2,4,8, and 14 dyas (P>0. 05). Bone tissue under the implanted HMWP plate manifested no absorption; the new bones formed under the HMWP plate and gradually matured as time went on. It is demonstrated in this study that HMWP has no adverse influence on the viability of osteoblasts and new bone formation and it can be used as internal fixation implant in treating fractures. PMID:16532823

Ren, Gaohong; Lin, Angru; Pei, Guoxian; Hu, Basheng

2006-02-01

414

Amphiphilic Interpenetrating Networks for the Delivery of Hydrophobic, Low Molecular Weight Therapeutic Agents  

PubMed Central

To investigate the delivery of hydrophobic therapeutic agents, a novel class of interpenetrating networks (IPNs) were synthesized and composed of two networks: methacrylic acid grafted with poly(ethylene glycol) tethers, P(MAA-g-EG), and poly(n-butyl acrylate) (PBA). The hydrophilic P(MAA-g-EG) networks are pH-responsive hydrogels capable of triggered release of an encapsulated therapeutic agent, such as a low molecular weight drug or a protein, when it passes from the stomach (low pH) to upper small intestine (neutral pH). PBA is a hydrophobic homopolymer that can affect the IPN swelling behavior, the therapeutic agent loading efficiencies in IPNs, and solute release profiles from IPNs. In dynamic swelling conditions, IPNs had greater swelling ratios than P(MAA-g-EG), but in equilibrium swelling conditions the IPN swelling ratio decreased with increasing PBA content. Loading efficiencies of the model therapeutic agent fluorescein ranged from 21 – 44%. Release studies from neat P(MAA-g-EG) and the ensuing IPNs indicated that the transition from low pH (2.0) to neutral pH (7.0) triggered fluorescein release. Maximum fluorescein release depended on the structure and hydrophilicity of the carriers used in these studies. PMID:22247592

Schoener, Cody A.; Hutson, Heather N.; Fletcher, Grace K.; Peppas, Nicholas A.

2011-01-01

415

The integrity of welded interfaces in ultra high molecular weight polyethylene: Part 1-Model.  

PubMed

The difficulty of eradicating memory of powder-particle interfaces in UHMWPE for bearing surfaces for hip and knee replacements is well-known, and 'fusion defects' have been implicated frequently in joint failures. During processing the polymer is formed into solid directly from the reactor powder, under pressure and at temperatures above the melting point, and two types of inter-particle defect occur: Type 1 (consolidation-deficient) and Type 2 (diffusion-deficient). To gain quantitative information on the extent of the problem, the formation of macroscopic butt welds in this material was studied, by (1) modelling the process and (2) measuring experimentally the resultant evolution of interface toughness. This paper reports on the model. A quantitative measure of interface structural integrity is defined, and related to the "maximum reptated molecular weight" introduced previously. The model assumes an idealised surface topography. It is used to calculate the evolution of interface integrity during welding, for given values of temperature, pressure, and parameters describing the surfaces, and a given molar mass distribution. Only four material properties are needed for the calculation; all of them available for polyethylene. The model shows that, for UHMWPE typically employed in knee transplants, the rate of eradication of Type 1 defects is highly sensitive to surface topography, process temperature and pressure. Also, even if Type 1 defects are prevented, Type 2 defects heal extremely slowly. They must be an intrinsic feature of UHMWPE for all reasonable forming conditions, and products and forming processes should be designed accordingly. PMID:16490249

Buckley, C Paul; Wu, Junjie; Haughie, David W

2006-06-01

416

Characterization of high molecular weight disinfection byproducts resulting from chlorination of aquatic humic substances.  

PubMed

Aquatic humic substances react with chlorine to produce numerous disinfection byproducts (DBPs) during chlorination of drinking water. Although low molecular weight (MW) chlorinated DBPs have been intensively studied over the past several decades, relatively little is known about high MW chlorinated DBPs (above 500 Da) that may be associated with adverse health implications. In this work, carrier-free radioactive 36Cl was introduced into a Suwannee River fulvic acid sample to label the chlorine-containing DBPs. By combining the fractionation techniques of ultrafiltration (UF) and size exclusion chromatography (SEC) with the detection of 36Cl, UV, and dissolved organic carbon (DOC), the high MW region in the SEC-36Cl profiles of the chlorinated sample with and without UF was defined. SEC-UV and SEC-DOC profiles were found to be approximately indicative of SEC-36Cl profiles for the high MW region. The MW distribution shows that the high MW chlorinated DBPs were highly dispersed with an average MW around 2000 Da based on calibration with polystyrene sulfonate standards. The Cl/C atomic ratios of the high MW DBPs were roughly constant (0.025), which is much lower than those of the common known chlorinated DBPs. PMID:12380071

Zhang, Xiangru; Minear, Roger A

2002-10-01

417

Synthesis, DNA binding and antileishmanial activity of low molecular weight bis-arylimidamides  

PubMed Central

The effects of reducing the molecular weight of the antileishmanial compound DB766 on DNA binding affinity, antileishmanial activity and cytotoxicity are reported. The bis-arylimidamides were prepared by the coupling of aryl S-(2-naphthylmethyl)thioimidates with the corresponding amines. Specifically, we have prepared new series of bis-arylimidamides which include 3a, 3b, 6, 9a, 9b, 9c, 13, and 18. Three compounds 9a, 9c, and 18 bind to DNA with similar or moderately lower affinity to that of DB766, the rest of these compounds either show quite weak binding or no binding at all to DNA. Compounds 9a, 9c, and 13 were the most active against L. amazonensis showing IC50 values of less than 1 µM, so they were screened against intracellular L. donovani showing outstanding activity with IC50.values of 25–79 nM. Despite exhibiting little in vitro cytotoxicity these three compounds were quite toxic to mice. PMID:22840696

Banerjee, Moloy; Farahat, Abdelbasset A.; Kumar, Arvind; Wenzler, Tanja; Brun, Reto; Munde, Manoj M.; Wilson, W. David; Zhu, Xiaohua

2013-01-01

418

Physical and chemical studies of a low-molecular-weight form of urease  

PubMed Central

1. A new form of enzymically active jack-bean [Canavalia ensiformis (L.) DC] urease corresponding to an S20,w value of 11·8s and a molecular weight of 260000 was investigated. 2. Conversion of 18s urease (EC 3.5.1.5) into the 12s form depends on both low protein concentration and pH. Above pH5·3 urease exists in the 18s form and below pH4·8 in the 12s form; between these two pH values a 12s–18s rapid-equilibrium process is observed. 3. Comparison of the properties of 18s and 12s urease indicated no major differences. 4. A survey of other good urease sources revealed that the 12s form can also be obtained from soya bean (Glycine soja Sieb. and Zucc. cultivar Biloxi) and the bacterium Bacillus pasteurii (Miguel) Migula, but not from watermelon (Citrullus vulgaris Schrad. cultivar Congo). 5. The 12s forms from jack bean and Bacillus pasteurii did not hybridize. ImagesFig. 5.Fig. 6.Fig. 7. PMID:5691753

Tanis, Robert J.; Naylor, Aubrey W.

1968-01-01

419

Molecular weight distribution effects on the structure of strongly adsorbed polymers by Monte Carlo simulation  

NASA Astrophysics Data System (ADS)

Monte Carlo simulations are reported to study the structure of polymers adsorbed from solution onto strongly attractive, perfectly smooth substrates. Six systems spanning a range of molecular weight distributions are investigated with a coarse-grained united atom model for freely rotating chains. By employing a global replica exchange algorithm and topology altering Monte Carlo moves, a range of monomer-surface attraction from weak (0.27kT) to strong (4kT) is simultaneously explored. Thus for the first time ever, equilibrium polymer adsorption on highly attractive surfaces is studied, with all adsorbed molecules displaying similar properties and statistics. The architecture of the adsorbed layers, including density profiles, bond orientation order parameters, radii of gyration, and distribution of the adsorbed chain fractions, is shown to be highly dependent on the polydispersity of the polymer phase. The homology of polymer chains, and the ergodicity of states explored by the molecules is in contrast to the metastable, kinetically constrained paradigm of irreversible adsorption. The structure of more monodisperse systems is qualitatively similar to experimental results and theoretical predictions, but result from very different chain conformations and statistics. The polydispersity-dependent behavior is explained in the context of the competition between polymers to make contact with the surface.

Kuppa, Vikram K.

2012-06-01

420

Effects of dissolved low molecular weight organic acids on oxidation of ferrous iron by Acidithiobacillus ferrooxidans.  

PubMed

A few researchers have reported on work concerning bioleaching of heavy-metal-contaminated soil using Acidithiobacillus ferrooxidans, since this acidophile is sensitive to dissolved low molecular weight (LMW) organic acids. Iron oxidation by A. ferrooxidans R2 as well as growth on ferrous iron was inhibited by a variety of dissolved LMW organic acids. Growth experiments with ferrous iron as an oxidant showed that the inhibition capability sequence was formic acid>acetic acid>propionic acid>oxalic acid>malic acid>citric acid. The concentrations that R2 might tolerate were formic acid 0.1mmolL(-1) (2mmolkg(-1)soil), acetic and propionic acids 0.4mmolL(-1) (8mmolkg(-1)soil), oxalic acid 2.0mmolL(-1) (40mmolkg(-1)soil), malic acid 20mmolL(-1) (400mmolkg(-1)soil), citric acid 40mmolL(-1) (800mmolkg(-1)soil), respectively. Although R2 was sensitive to organic acids, the concentrations of LMW organic acids in the contaminated soils were rather lower than the tolerable levels. Hence, it is feasible that R2 might be used for bioleaching of soils contaminated with metals or metals coupled with organic compounds because of the higher concentrations of LMW organic acids to which R2 is tolerant. PMID:18554786

Ren, Wan-Xia; Li, Pei-Jun; Zheng, Le; Fan, Shu-Xiu; Verhozina, V A

2009-02-15

421

The influence of polymer molecular weight in lamellar gels based on PEG-lipids.  

PubMed Central

We report x-ray scattering, rheological, and freeze-fracture and polarizing microscopy studies of a liquid crystalline hydrogel called Lalpha,g. The hydrogel, found in DMPC, pentanol, water, and PEG-DMPE mixtures, differs from traditional hydrogels, which require high MW polymer, are disordered, and gel only at polymer concentrations exceeding an "overlap" concentration. In contrast, the Lalpha,g uses very low-molecular-weight polymer-lipids (1212, 2689, and 5817 g/mole), shows lamellar order, and requires a lower PEG-DMPE concentration to gel as water concentration increases. Significantly, the Lalpha,g contains fluid membranes, unlike Lbeta' gels, which gel via chain ordering. A recent model of gelation in Lalpha phases predicts that polymer-lipids both promote and stabilize defects; these defects, resisting shear in all directions, then produce elasticity. We compare our observations to this model, with particular attention to the dependence of gelation on the PEG MW used. We also use x-ray lineshape analysis of scattering from samples spanning the fluid-gel transition to obtain the elasticity coefficients kappa and B; this analysis demonstrates that although B in particular depends strongly on PEG-DMPE concentration, gelation is uncorrelated to changes in membrane elasticity. PMID:9649387

Warriner, H E; Keller, S L; Idziak, S H; Slack, N L; Davidson, P; Zasadzinski, J A; Safinya, C R

1998-01-01

422

Potential errors in FTIR measurement of oxidation in ultrahigh molecular weight polyethylene implants.  

PubMed

Potential sources of error in the use of FTIR to measure the level of oxidation in ultrahigh molecular weight polyethylene acetabular cups were evaluated using cups from a hip simulator wear study with and without artificial aging, as well as cups retrieved from clinically failed hip prostheses. Oxidation was measured as a function of depth below the bearing surface using transmission FTIR on microtomed sections of the cups. To account for the variation of the thickness of the microtomed sections, oxidation was plotted as the ratio of the absorbance of the carbonyl groups to the absorbance of a reference band at 2022 cm-1. Overnight soaking in hexane reduced the apparent levels of oxidation, presumably due to the extraction of absorbed contaminants. In cups with low to moderate levels of oxidation, the reference absorption was relatively independent of the level of oxidation and was linearly proportional to the thickness of the specimens, providing reproducible oxidation ratios. However, the scatter in the reference absorption and in the apparent oxidation ratio increased with increasing levels of oxidation and was greatest for the thickest (400 microm) microtomed sections. The profiles of the oxidation ratios for a given specimen that were plotted by the present study method could be numerically adjusted to coincide with the ratios plotted using the methods of two previous investigators, providing conversion factors that are useful for comparing results among the studies. PMID:10398021

Shen, F W; Yu, Y J; McKellop, H

1999-01-01

423

High frequency viscoelastic behaviour of low molecular weight hyaluronic acid water solutions.  

PubMed

Hyaluronic acid (HA) is a polysaccharide widely used in biomedical applications, due to its elevated biocompatibility and the peculiar viscoelastic properties of its solutions. Although the viscoelastic behaviour of HA solutions has been extensively studied in the literature it has been often reported in the range of low frequency (1-100 Hz) and high salt concentration, whereas the main rheological peculiarities of this molecule are expected at high frequency (>100 Hz) and low salt concentration. In this work we studied the viscoelastic properties of low molecular weight HA (155 kDa) in wide range of concentrations (0.01-20 mg/ml) at low ionic strength and over an extended frequency range (0.1-1000 Hz) using both optical tweezers and conventional rheometry. Good agreement between the high frequency dynamic behaviour (optical tweezers) and the viscoelastic properties at low frequency (rheometry) was found. We also found that, in apparent contradiction with polyelectrolyte solution theory, HA solution behaves as liquid-like viscoelastic fluid (G''>G') even at concentrations higher than the entanglement concentration where a weak-gel behavior should be expected. PMID:18401078

Fusco, Sabato; Borzacchiello, Assunta; Miccio, Lisa; Pesce, Giuseppe; Rusciano, Giulia; Sasso, Antonio; Netti, Paolo A

2007-01-01

424

Characterisation of low molecular weight glutenin subunit genes from Pseudoroegneria spicata and Pd. strigosa.  

PubMed

We report the characterisation of nine novel low molecular weight glutenin subunit (LMW-GS) genes from two Pseudoroegneria species, Pd. spicata and Pd. strigosa. We found that all nine LMW-GS genes possess the same primary structure shared by other published LMW-GS. Five genes encode LMW-i type subunits, three encode LMW-m type subunits and one encodes a peptide similar to B-3 hordeins of Hordeum chilense. No LMW-s type subunit genes were found in Pseudoroegneria. One subunit, PSt24-LMW-2, contains six conserved cysteine residues, and the other eight subunits all contain eight cysteine residues. We show that one cysteine residue is located in the signal peptide of PSt24-LMW-1, suggesting a mature peptide containing only seven cysteine residues. Phylogenetic analysis indicates that the LMW-GS genes from the St genome cluster together and suggests a distant relationship with LMW-GS of the A and B genomes of wheat. Slippage/unequal crossing over and illegitimate recombination are effective mechanisms for enriching variations of seed storage proteins. PMID:25099921

Qin, Lumin; Liang, Yu; Yang, Daozheng; Xia, Guangmin; Liu, Shuwei

2015-02-01

425

Effect of low molecular weight heparan sulphate on angiogenesis in the rat cornea after chemical cauterization.  

PubMed

Vascularization of the cornea occurs in many pathological conditions and can result in loss of visual acuity. It is also thought that vascularization predisposes the cornea to reject grafts by facilitating the detection of foreign antigens in donor material. A rat corneal assay for angiogenesis was adopted in the present study to evaluate the possible angiostatic activity of a low molecular weight heparan sulphate (LMW-HS). Corneal lesions were induced by chemical cauterization at 2 mm from the corneoscleral limbus. Rats were randomized to receive two drops/eye four times daily, for 6 days, of a solution of LMW-HS in vehicle (2.5% carboxymethylcellulose), heparin, heparin plus hydrocortisone, or vehicle alone. After a 6 day-treatment period, the eyes were perfused with india ink and the degree of neovascularization was evaluated. In rats treated with vehicle alone a dense vascular network extending from the corneoscleral limbus to the cauterized site was observed; on the contrary, a markedly reduced vascular network was evidenced in animals treated with LMW-HS. The distribution of basic fibroblast growth factor (bFGF) in the cauterized cornea was also evaluated by using an immunohistochemical method. A marked bFGF immunoreactivity was demonstrated in corneal epithelium and stroma of control rats 12-48 hours after the cautery. These results lead to the assumption that LMW-HS could be used in ophthalmology to inhibit corneal neovascularization. PMID:8207330

Lepri, A; Benelli, U; Bernardini, N; Bianchi, F; Lupetti, M; Danesi, R; Del Tacca, M; Nardi, M

1994-01-01

426

Black Carbon in Estuarine (Coastal) High-molecular-weight Dissolved Organic Matter  

NASA Technical Reports Server (NTRS)

Dissolved organic matter (DOM) in the ocean constitutes one of the largest pools of organic carbon in the biosphere, yet much of its composition is uncharacterized. Observations of black carbon (BC) particles (by-products of fossil fuel combustion and biomass burning) in the atmosphere, ice, rivers, soils and marine sediments suggest that this material is ubiquitous, yet the contribution of BC to the ocean s DOM pool remains unknown. Analysis of high-molecular-weight DOM isolated from surface waters of two estuaries in the northwest Atlantic Ocean finds that BC is a significant component of DOM, suggesting that river-estuary systems are important exporters of BC to the ocean through DOM. We show that BC comprises 4-7% of the dissolved organic carbon (DOC) at coastal ocean sites, which supports the hypothesis that the DOC pool is the intermediate reservoir in which BC ages prior to sedimentary deposition. Flux calculations suggest that BC could be as important as vascular plant-derived lignin in terms of carbon inputs to the ocean. Production of BC sequesters fossil fuel- and biomass-derived carbon into a refractory carbon pool. Hence, BC may represent a significant sink for carbon to the ocean.

Mannino, Antonio; Harvey, H. Rodger

2003-01-01

427

Thrombin generation and low-molecular-weight heparin prophylaxis in pregnant women with thrombophilia.  

PubMed

Pregnancy is associated with increased risk of venous thromboembolism, especially in the presence of thrombophilia. However, there is no consensus on the optimal approach for thromboprophylaxis in this population. Recent evidence suggests that thrombin generation correlates with the overall procoagulant state of the plasma. Our aim was to evaluate thrombin generation in a prospective cohort of thrombophilic pregnant women, and investigate the effectiveness of low-molecular-weight heparin (LMWH) prophylaxis in pregnancy. Women with severe (n=8), mild (n=47) and no (n=15) thrombophilia were followed throughout their pregnancies. Thrombin generation was evaluated in each trimester as well as five days and eight weeks postpartum (as a reference category). In women undergoing LMWH prophylaxis, thrombin generation and anti-Factor-Xa activity were measured just before and 4 hours after administration (peak effect). Thrombin generation was determined using Technothrombin TGA assay system. For the analysis, median peak thrombin and endogenous thrombin potential were used. Peak thrombin and endogenous thrombin potential were increased during pregnancy compared to the non-pregnant state with the highest results in the severe thrombophilia group. In women receiving LMWH prophylaxis a decrease was observed in thrombin generation at peak effect but over the progression of pregnancy the extent of this decrease reduced in a stepwise fashion. Our results show that thrombin generation demonstrates the hypercoagulable state in thrombophilic pregnancies. In addition, we found the effect of LMWH prophylaxis to progressively decrease with advancing stages of pregnancy. PMID:25392852

Selmeczi, A; Roach, R E J; Móré, C; Batta, Z; Hársfalvi, J; van der Bom, J G; Boda, Z; Oláh, Z

2014-11-13

428

Delamination and adhesive wear behavior of alpha-tocopherol-stabilized irradiated ultrahigh-molecular-weight polyethylene.  

PubMed

Wear and delamination of conventional ultrahigh-molecular-weight polyethylene (UHMWPE) components used in total knee arthroplasty can compromise long-term performance. Radiation cross-linking and melt-annealing reduced wear and increased delamination resistance of UHMWPE. An alternative material is the alpha-tocopherol-stabilized irradiated UHMWPE (alphaTPE), with improved mechanical and fatigue properties vs irradiated and melted UHMWPE. We studied the wear and delamination resistance of alphaTPE and conventional UHMWPE (direct compression molded GUR 1050 and Himont 1900) under reciprocating unidirectional motion. Wear resistance was improved, and no delamination was observed in alphaTPE. Accelerated aging did not alter the wear and delamination behavior of alphaTPE. The GUR 1050 UHMWPE showed delamination and pitting when subjected to unidirectional reciprocating motion after accelerated aging. Himont 1900 UHMWPE showed no delamination when subjected to unidirectional reciprocating motion after accelerated aging. alpha-Tocopherol-stabilized irradiated UHMWPE is advanced for use in total knee arthroplasty due to its high resistance to wear, delamination, and oxidation. PMID:19493652

Wannomae, Keith K; Christensen, Steven D; Micheli, Brad R; Rowell, Shannon L; Schroeder, Dave W; Muratoglu, Orhun K

2010-06-01

429

Low-Molecular-Weight Metabolites Secreted by Paenibacillus larvae as Potential Virulence Factors of American Foulbrood  

PubMed Central

The spore-forming bacterium Paenibacillus larvae causes a severe and highly infective bee disease, American foulbrood (AFB). Despite the large economic losses induced by AFB, the virulence factors produced by P. larvae are as yet unknown. To identify such virulence factors, we experimentally infected young, susceptible larvae of the honeybee, Apis mellifera carnica, with different P. larvae isolates. Honeybee larvae were reared in vitro in 24-well plates in the laboratory after isolation from the brood comb. We identified genotype-specific differences in the etiopathology of AFB between the tested isolates of P. larvae, which were revealed by differences in the median lethal times. Furthermore, we confirmed that extracts of P. larvae cultures contain low-molecular-weight compounds, which are toxic to honeybee larvae. Our data indicate that P. larvae secretes metabolites into the medium with a potent honeybee toxic activity pointing to a novel pathogenic factor(s) of P. larvae. Genome mining of P. larvae subsp. larvae BRL-230010 led to the identification of several biosynthesis gene clusters putatively involved in natural product biosynthesis, highlighting the potential of P. larvae to produce such compounds. PMID:24509920

Schild, Hedwig-Annabell; Fuchs, Sebastian W.

2014-01-01

430

Microscopic destruction of ultra-high molecular weight polyethylene (UHMWPE) under uniaxial tension.  

PubMed

To examine the effects of a networked substructure of granular agglomerate on a style of destruction in prosthetic ultra-high molecular weight polyethylene (UHMWPE), uniaxial tensile simulations were carried out using the numerical model based on the discrete element method (DEM). The numerical simulations were performed taking the difference of mechanical characteristics between inter-granular and intra-granular portions of UHMWPE into consideration. A significant increase in stress and strain was observed along grain boundaries where micro cracks were initiated. This finding suggests that the large difference of mechanical properties between intra-granular and inter-granular portions causes significantly increased local stresses and strains in the vicinity of grain boundaries. The tensile simulation resulted in intra-granular destruction, which had good agreement with a result of previous experimental observation. This is presumably because the directions of principal shear stresses do not coincide with those at stress-concentrated grain boundaries. The dependence of the style of material destruction on forms of loading application could be explained by the relationship between directions of principal shear stress and reorientations of stress-concentrated grain boundaries. PMID:12652022

Shibata, Nobuyuki; Tomita, Naohide; Ikeuchi, Ken

2003-01-01

431

Characterization and quantitation of low and high molecular weight phenolic compounds in apple seeds.  

PubMed

The phenolic constituents of seeds of 12 different apple cultivars were fractionated by sequential extraction with aqueous acetone (30:70, v/v) and ethyl acetate after hexane extraction of the lipids. Low molecular weight phenolic compounds were individually quantitated by RP-HPLC-DAD. The contents of extractable and nonextractable procyanidins were determined by applying RP-HPLC following thiolysis and n-butanol/HCl hydrolysis, respectively. As expected, the results revealed marked differences of the ethyl acetate extracts, aqueous acetone extracts, and insoluble residues with regard to contents and mean degrees of polymerization of procyanidins. Total phenolic contents in the defatted apple seed residues ranged between 18.4 and 99.8 mg/g. Phloridzin was the most abundant phenolic compound, representing 79-92% of monomeric polyphenols. Yields of phenolic compounds significantly differed among the cultivars under study, with seeds of cider apples generally being richer in phloridzin and catechins than seeds of dessert apple cultivars. This is the first study presenting comprehensive data on the contents of phenolic compounds in apple seeds comprising extractable and nonextractable procyanidins. Furthermore, the present work points out a strategy for the sustainable and complete exploitation of apple seeds as valuable agro-industrial byproducts, in particular as a rich source of phloridzin and antioxidant flavanols. PMID:22220632

Fromm, Matthias; Bayha, Sandra; Carle, Reinhold; Kammerer, Dietmar R

2012-02-01

432

Characterization of low-molecular-weight glutenin subunit genes from Hordeum brevisubulatum ssp. turkestanicum.  

PubMed

Three novel low-molecular-weight glutenin subunit (LMW-GS) genes (designated as Ht1, Ht2, and Ht3) were isolated from the genomic DNA of Hordeum brevisubulatum ssp. turkestanicum by PCR amplification (accession no. Y0695). The coding regions of Ht1, Ht2, and Ht3 were 924, 924, and 903 bp, respectively. The deduced amino acid sequences were 306, 306, and 299 amino acid residues each with a signal peptide, a central repetitive region rich in proline and glutamine, and N- and C-terminal non-repetitive domains. A comparison was carried out of these genes with other known B hordein genes from cultivated barley and LMW glutenin genes from wheat. The results indicated that Ht1, Ht2, and Ht3 had a more similar structure and a higher level of homology with the LMW-GS genes than the B hordein genes. In order to investigate the evolutionary relationship of the novel genes with the prolamin genes from barley and wheat, the phylogenetic tree was constructed and the subfamilies of these prolamin genes were identified. The results suggested that the three novel genes were glutenin-like proteins designated as LMW-m type genes. PMID:16521538

Hou, Y C; Liu, Q; Long, H; Wei, Y M; Zheng, Y L

2006-01-01

433

Low-molecular-weight metabolites secreted by Paenibacillus larvae as potential virulence factors of American foulbrood.  

PubMed

The spore-forming bacterium Paenibacillus larvae causes a severe and highly infective bee disease, American foulbrood (AFB). Despite the large economic losses induced by AFB, the virulence factors produced by P. larvae are as yet unknown. To identify such virulence factors, we experimentally infected young, susceptible larvae of the honeybee, Apis mellifera carnica, with different P. larvae isolates. Honeybee larvae were reared in vitro in 24-well plates in the laboratory after isolation from the brood comb. We identified genotype-specific differences in the etiopathology of AFB between the tested isolates of P. larvae, which were revealed by differences in the median lethal times. Furthermore, we confirmed that extracts of P. larvae cultures contain low-molecular-weight compounds, which are toxic to honeybee larvae. Our data indicate that P. larvae secretes metabolites into the medium with a potent honeybee toxic activity pointing to a novel pathogenic factor(s) of P. larvae. Genome mining of P. larvae subsp. larvae BRL-230010 led to the identification of several biosynthesis gene clusters putatively involved in natural product biosynthesis, highlighting the potential of P. larvae to produce such compounds. PMID:24509920

Schild, Hedwig-Annabell; Fuchs, Sebastian W; Bode, Helge B; Grünewald, Bernd

2014-04-01

434

Laser surface modification of ultra-high-molecular-weight polyethylene (UHMWPE) for biomedical applications  

NASA Astrophysics Data System (ADS)

Ultra-high-molecular-weight polyethylene (UHMWPE) is a synthetic polymer used for biomedical applications because of its high impact resistance, ductility and stability in contact with physiological fluids. Therefore, this material is being used in human orthopedic implants such as total hip or knee replacements. Surface modification of this material relates to changes on its chemistry, microstructure, roughness, and topography, all influencing its biological response. Surface treatment of UHMWPE is very difficult due to its high melt viscosity. This work presents a systematic approach to discern the role of different laser wavelengths (? = 1064, 532, and 355 nm) on the surface modification of carbon coated UHMWPE samples. Influence of laser processing conditions (irradiance, pulse frequency, scanning speed, and spot overlapping) on the surface properties of this material was determined using an advanced statistical planning of experiments. A full factorial design of experiments was used to find the main effects of the processing parameters. The obtained results indicate the way to maximize surface properties which largely influence cell-material interaction.

Riveiro, A.; Soto, R.; del Val, J.; Comesaña, R.; Boutinguiza, M.; Quintero, F.; Lusquiños, F.; Pou, J.

2014-05-01

435

Stabilization of fenofibrate in low molecular weight hydroxypropylcellulose matrices produced by hot-melt extrusion.  

PubMed

The objective of this study was to improve the dissolution rate and to enhance the stability of a poorly water-soluble and low glass-trasition temperature (T(g)) model drug, fenofibrate, in low molecular weight grades of hydroxypropylcellulose matrices produced by hot-melt extrusion (HME). Percent drug loading had a significant effect on the extrudability of the formulations. Dissolution rate of fenofibrate from melt extruded pellets was faster than that of the pure drug (p < 0.05). Incorporation of sugars within the formulation further increased the fenofibrate release rates. Differential scanning calorimetry results revealed that the crystalline drug was converted into an amorphous form during the HME process. Fenofibrate is prone to recrystallization due to its low T(g). Various polymers were evaluated as stabilizing agents among which polyvinylpyrrolidone 17PF and amino methacrylate copolymer exhibited a significant inhibitory effect on fenofibrate recrystallization in the hot-melt extrudates. Subsequently immediate-release fenofibrate tablets were successfully developed and complete drug release was achieved within 5 min. The dissolution profile was comparable to that of a currently marketed formulation. The hot-melt extruded fenofibrate tablets were stable, and exhibited an unchanged drug release profile after 3-month storage at 40°C/75% RH. PMID:22524504

Deng, Weibin; Majumdar, Soumyajit; Singh, Abhilasha; Shah, Sejal; Mohammed, Noorullah Naqvi; Jo, Seongbong; Pinto, Elanor; Tewari, Divya; Durig, Thomas; Repka, Michael A

2013-02-01

436

Molecular weight distribution effects on the structure of strongly adsorbed polymers by Monte Carlo simulation.  

PubMed

Monte Carlo simulations are reported to study the structure of polymers adsorbed from solution onto strongly attractive, perfectly smooth substrates. Six systems spanning a range of molecular weight distributions are investigated with a coarse-grained united atom model for freely rotating chains. By employing a global replica exchange algorithm and topology altering Monte Carlo moves, a range of monomer-surface attraction from weak (0.27kT) to strong (4kT) is simultaneously explored. Thus for the first time ever, equilibrium polymer adsorption on highly attractive surfaces is studied, with all adsorbed molecules displaying similar properties and statistics. The architecture of the adsorbed layers, including density profiles, bond orientation order parameters, radii of gyration, and distribution of the adsorbed chain fractions, is shown to be highly dependent on the polydispersity of the polymer phase. The homology of polymer chains, and the ergodicity of states explored by the molecules is in contrast to the metastable, kinetically constrained paradigm of irreversible adsorption. The structure of more monodisperse systems is qualitatively similar to experimental results and theoretical predictions, but result from very different chain conformations and statistics. The polydispersity-dependent behavior is explained in the context of the competition between polymers to make contact with the surface. PMID:22697567

Kuppa, Vikram K

2012-06-01

437

Quasi-static multiaxial testing of PBX 9501: Creep effects on Estane molecular weight  

SciTech Connect

High explosives (HE) can be subjected to low level loading due to weapon design. As with other materials, loads well below the elastic limit may still lead to material property changes over time. PBX 9501, a conventional high explosive, has been used in several system designs. To evaluate potential environmental aging effects on HE, it is necessary to characterize material-flow and mechanical-property changes occurring in PBX 9501. Low-level loads may bring about material changes if creep related phenomena, such as polymer disentanglement or uncrosslinking, occur in the material. Recently, several studies on HE have increased understanding of the effects of density and the relative percentage of constituents on materials properties, e.g. elastic modulus, ultimate strength, and strain at ultimate strength, at low strain rates ({approx} 10{sup {minus}3} to 10{sup {minus}1} s{sup {minus}1}). However, the authors are only beginning to understand the effects of quasi-static multiaxial loading on PBX 9501 and Estane molecular weight (MW) changes. The results of these experiments are presented in this report.

Peterson, P.D. [Univ. of South Carolina, Columbia, SC (United States); Idar, D.J.; Rabie, R.; Fugard, C.S.; King, W.; Buntain, G.A. [Los Alamos National Lab., NM (United States); Crane, N.B. [Brigham Young Univ., Provo, UT (United States)

1999-02-01

438

Primary structures of bovine liver low molecular weight kininogen precursors and their two mRNAs.  

PubMed Central

By using a mixture of synthetic oligodeoxyribonucleotides as a probe, cloned cDNA sequences specific for low molecular weight (LMW) kininogen have been isolated from a cDNA library of bovine liver mRNA sequences. Nucleotide sequence analyses of cloned cDNA inserts have revealed that bovine liver LMW kininogens are encoded by at least two very similar but distinct mRNAs. The corresponding amino acid sequences show that the LMW kininogen precursors of the two types, composed of 436 and 434 amino acid residues, both contain two internally homologous sequences in the amino-terminal portion between a signal peptide and a bradykinin moiety. The two mRNAs exhibit 15 nucleotide substitutions and 6 nucleotide deletions/additions in their protein-coding regions. The replacement of 13 amino acid residues and the deletions/additions of 2 amino acid residues in the two LMW kininogen precursors are all localized within the internally homologous regions, implying that these regions may be biologically significant in relation to the existence of two LMW kininogens. The nucleotide changes in the two mRNAs also occur in the limited portions that principally encode the internally homologous amino acid sequences. This suggests that the mRNAs are transcribed from the same gene to generate two LMW kininogen precursors differing only in the internally homologous sequences. Images PMID:6572010

Nawa, H; Kitamura, N; Hirose, T; Asai, M; Inayama, S; Nakanishi, S

1983-01-01

439

Disappearance of a low molecular weight heparin fraction (CY 216) differs from standard heparin in rabbits  

SciTech Connect

In previous studies, we have reported that standard heparin (SH) was cleared by two mechanisms, a saturable mechanism which predominated at low doses (less than 100 anti-factor Xa U/kg) and a non-saturable mechanism which predominated at higher doses, when the first mechanism became saturated. In this study, we examined the importance of these two mechanisms in the disappearance of a low molecular weight heparin fraction (LMWH) (CY 216), by comparing the pharmacokinetics and the pharmacodynamics of a wide range of doses of SH and CY 216 (1.5 to 500 anti-factor Xa U/kg). Pharmacokinetics was measured as the disappearance of /sup 125/I-radiolabelled SH or CY 216. Pharmacodynamics was measured as the disappearance of the anti-factor Xa activity of SH and CY 216. We found that the saturable mechanism contributed little to the disappearance of CY 216 and that it was cleared predominantly by the non-saturable mechanism at all doses tested. Thus, at low doses (less than 100 anti-factor Xa U/kg), SH was cleared more rapidly than CY 216, whereas at higher doses, CY 216 was cleared more rapidly than SH. We conclude that the mechanism of disappearance of LMWH's differ significantly from those of SH, and that this difference may explain the apparent prolonged anticoagulant activity of LMWH's within the therapeutic range doses.

Boneu, B.; Buchanan, M.R.; Caranobe, C.; Gabaig, A.M.; Dupouy, D.; Sie, P.; Hirsh, J.

1987-06-15

440

Influence of molecular weight on oral absorption of water soluble chitosans.  

PubMed

Chitosan, a cationic polysaccharide, has been widely employed as dietary supplement and in pharmacological and biomedical applications. Although numerous studies have focused on its applications as pharmaceutical excipients or bioactive reagents, molecular weight (MW)-dependent pharmaceutical and bioactive properties remain unclear. As a preliminary study, we investigated the MW-dependent Caco-2 cell layer transport phenomena (in vitro) and intestinal absorption patterns after oral administration (in vivo) of water-soluble chitosans (WSCs). The absorption of chitosan was significantly influenced by its MW. As the MW increases, the absorption decreases. Compared to high-MW chitosan (WSC 230K, MW=230 kDa), absorption profiles were observed to increase more than 23 and 25 times with WSC 3.8K (MW=3.8 kDa) in both in vitro and in vivo transport experiments, respectively. Furthermore, the chitosans showed concentration- and MW-dependent cytotoxic effects, and the chitosan oligosaccharides (MW<10 kDa) showed negligible cytotoxic effect on the Caco-2 cells. In consideration with safety and absorption profiles, chitosan oligosaccharides may be considered as safe and potential candidates for pharmaceutical and biomedical applications. PMID:15653159

Chae, Su Young; Jang, Mi-Kyeong; Nah, Jae-Woon

2005-02-01